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Control Techniques for Particulate Air Pollutants.Public Health Service (DHEW), Washington, D.C.National Air Pollution Control. Administration.Pub-AP-51Jan 69241p.Superintendent of Documents, J.S. GovernmentPrinting Office, Vshington, D.C. 20402 (Cat. No. FS2.93/3:51, $1.75)

EDRS Price MF-$1.00 HC Not Available from EDRS.*Air Pollution Control, *Environment, EnvironmentalInfluences, *Pollution, *Resource Materials

ABSTRACTIncluded Is a comprehensive review of the approaches

commonly recommended for controlling the sources of particulate airpollution. Not all possible combinations of control techniques thatmight bring atout more stringent control of each individual sourceore reviewed. The many agricultural, commercial, domestic,industrial, and municipal processes and activities that generateparticulate air pollutants are described individually and the varioustechniques that can be applied to control emissions of particulatematte: from these sources ate reviewed and compared. A technicalconsideration of the most important types of gas cleaning devicesforms a major segment of the document, while sections on sourceevaluation, equipment costs and cost-effectiveness analysis, andcurrent research and development are also included. The bibliographycontains important reference articles, arranged according toapplicable procerses. (Author/PR)

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CONTROL TECHNIQUES

FOR

PARTICULATE AIR POLLUTANTS

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE

Public Health ServiceConsumer Protection and Environmental Health Service

National Air Polluilon Control Adminfstratien

Washington, D.C.

January 1969

National Mr Pollution Cootrol Administration Publication No, AP-51

Preface

Throughout the development of Federalair pollution legislation, the Congress hasconsistently found that the States and localgovernments have the primary responsibilityfor preventing and controlling air pollutionat its source. Further, the Congress has con-sistently declared that, it is the responsibilityof the Federal government to provide techi-cal and financial assistance to State and localgovernments so that they can undertakethese responsibilities.

These principles were reiterated in the AirQuality Act of 1967. A hey element of thatAct directs the Secretary of Health, Educa-tion, and Welfare to collect and make avail-able information on all aspects of air pol-lution and its control. Under the Act theissuance of control techniques informationis a vital step in a program designed to as-sist the States in taking responsible techno-logical, social, and political action to protectthe public from the adverse effects of airpollution.

Briefly, the Act calls for the Secretary ofHealth, Education, and Welfare to define thebroad atmospheric areas of the Nation inwhich climate, meteorology, and topography.all of which influence the capacity of air todilute and disperse pollution, are generallyhomogeneous.

Further, the Act requires the Secretary todefine those geographical regions in thecountry where air pollution is A problem--whether interstate or intrastate. These airquality control regions are designated onthe basis of meteorological, social, and po-litical factors which suggest that a groupof communities should be treated as a unitfor setting limitations on concentrations ofatmospheric pollutants. Concurrently, theSecretary is required to issue air quality cri-teria for those pollutants he believes maybe harmful to health or welfare, and to pub-

lish related information on the techniqueswhich can be employed to control the sourcesof those pollutants.

Once these steps have been taken for anyregion, and for any pollutant or combina-tion of pollutants, then the State or Statesresponsible for the designated region are onnotice to develop ambient air quality stand-ards applicable to the region for the pollut-ants involved, and to develop plans of ac-tion for meeting the standards.

The Department of Health, Education, andWelfare will review, evaluate, and approvethese standards and plans and, once theyare approved, the States will be expected totake action to control pollution sources in themanner outlined in their plans.

At the direction. of the Secretary, the Na-tional Air Pollution Control Administrationhas established appropriate programs tocarry out the several Federal responsibilitiesspecified in the legislation.

Control Techniques for Particulate AirPollutants is the first of a series of docu-ments to be produced under the program es-tablished to carry out the responsibility fordeveloping and distributing control techn...'ogy information. The document is the culmi-nation of intensive and dedicated effort onthe part of many persons.

In eccordance with the Air Quality Act, aNational Air Pollution Control TechniquesAdvisory Committee was established, havinga membership broadly representative of in-dustry, universities, and all levels of go 'ern-rnent. The committee, whose members arelisted following this discussion, provided in-valuable advice in identifying the best pos-sible methods for controlling the sources ofparticulate air pollution, assisted in deter-mining the costs involved, and gave majorassistance in dratting this document.

As further required by the Air Quality

Hi

Act, appropriate Federal departments andagencies, also listed on the following pages,were consulted prior to issuance of this docu-ment. A Federal consultation committee,comprising members designated by the headsof 17 departments and agencies, reviewed thedocument, and met with staff personnel ofthe National Air Pollution Control Adminis-tration to discuss its contents.

During 196 ?, at the initiation of the Sec-retary of Health, Education, and Welfare,several government-industry task groupswere formed to explore mutual problems re-lating to air pollution control. One of these,a task group on control technology researchand development, looked into ways that in-dustry representatives could participate inthe review of the control techniques reports.Accordingly, several industrial representa-tives, listed on the following pages, reviewedthis document and provided helpful com-ments and suggestions. In addition, certainconsultants to the National Mr PollutionControl Administration also reviewed andassisted in preparing portions of this docu-ment. (These also are listed on the follow-ing pages.)

iv

The Administration is pleased to acknowl-edge the efforts of each of the persons spe-cifically named, as well as those of the manynot so listed who contributed to the publica-tion of this volur.e. In the last analysis, how-ever, the National Air Pollution Control Ad-ministration is responsible for its content.

The control of air pollutant emissions isa complex problem because of the variety ofsources and source characteristics. Techni-cal factors frequently make necessary theuse of different control procedures for dif-ferent types of sources. Many techniquesare still in the developmental stage, and pru-dent control strategy may call for the use ofinterim methods until these techniques areperfected. Thus, we can expect that we willcontinue to improve, refine, and periodicallyrevise the control technique information sothat it will continue to reflect the most up-to-date knowledge available.

Jon N T. MIDDLNTON, Commissioncr,National Mr Pollution Control

Administration

NATIONAL AIR POLLUTION CONTROL TECHNIQUES ADVISORYCOMMITTEE:

Mr. Louis 1). AlpertGeneral ManagerMidwestern Department of the

Federated Metal' DivisionAmerican Smelting & Refining CompanyWhiting, Indiana

Professor James II. BlacksDepartment of Chemical EngineeringUniversity of AlabamaUniversity, Alabama

Mr. Robert L. ChatsChief Deputy Air Pollution

Control OfficerLos Angeles Conty Air Pollution

Control DistrictLos Angeles, California

Mr. W. DonhAm CrawfordAdministrative Vice PresidentConsolidated Edison Company

of New York, Inc.New York, New York

Mr. Herbert J. DunsmoreAssistant to Administrative

Vice President of EngineeringU. S. Steel CorporationPittsburgh, Pennsylvania

Mr. John L Gi !MeadTechnical DirectorIdeal Cement CompanyDenver, Colorado

lusivtcl September 1, tirSa

Mr. James L. ParsonsConsultant ManagerEnvironmental Engineeringnngineering DepartmentE. I. duPont de Nemours & Co., Inc.Wilmington, Delaware

Professor August T. RossanoDepartment of Civil EngineeringAir Resource ProgramUnivers lty of WashingtonSeattle, Washington

Mr. Jack A. SimonPrincipal GeologistIllinois State Geological SurveyNatural Resources BuildingUrbana, Illinois

Mr. Victor Ii. SussmanDirectorDivision of Air Pollution ControlPennsylvania Department of

HealthHarrisburg, Pennsylvania

Mr. Ea:i L. Wilson, Jr.ManagerIndustrial Gas Cleaning DepartmentKoppers Conttany, Inc.Metal Products DivisionI3aitimorc, Maryland

Dr. !tarry J. WhiteIlea&Department of Applied SciencePortland State CollegePortland, Oregon

FEDERAL AGENCY LIAISON REPRESENTATIVES

Department of AgricultureKenneth E. GrantAssociate AdministratorSoil Conservation Service

Department of CommercePaul T. O'DayStaff Assistant to the Secretary

Department of DefenseColonel Alvin F. Meyer, Jr.ChairmanEnvironmental Pollution Centro) Committee

Department of /lousing and UrbanDevelopment

Charles M. HaarAssistant Secretary for Metropolitan

Development

Department of the InteriorHarry PerryMineral Resources Research Advisor

Department of JusticeWalter Kietel, Jr.Assistant ChiefGeneral Litigation SectionLand and Natural Resources Division

Department of LaborDr. Leonard R. LinsenmayerDeputy DirectorBureau of Labor Standards

Department of TransportationWilliam H. CloseAssistant Director for Environmental

ResearchOffice ,1'. Noise Abatement

vi

Department of the TreasuryGerard M. BrannonDirectorOffice of Tax Analysis

Federal Power CommissionF. Stewart BrownChiefBureau of Power

General Services AdministrationThomas E. CrockerDirectorRepair and Improvement DivisionPublic Buildings Service

National Aeronautics and SpaceAdministration

Major General R. II. Curtin, USAF (Ret.)Director of Facilities

National Science FoundationDr. Eugene W. BierlyProgram Director for MeteorologyDivision of Environmental Sciences

Post Office DepartmentLouis B. FelemanClic(Transportation Equipment BranchBureau of Research and Engineering

Trancesre Valley AuthorityDr. F. E. GartrellAssistant Director of Hellth

Atomic Energy CommissionDr. Martin R. BilesDirectorDivision of Operational Safety

Veterans AdministrationGerald M. HollanderDirector of Architecture and EngineeringOffice of Construction

CONTRIBUTORS

Mr. L. P. AugenbrightAssistant Sales ManagerWestern Knapp Engineering DivisionArthur G. McKee and CompanySan Francisco, California

Dr, Alien D. BrandtManagerEnvironmental Quality ControlBethlehem Steel CompanyBethlehem, Pennsylvania

Mr. William BridleSenior AdvisorInstitute of Gas TechnologyChicago, Illinois

Di. Donald A. I3orumConsulting Chemical EngineerNew York, New York

Mr. John D. CaplanTechnical DirectorBask. and Applied SciencesResearch LaboratoriesGeneral Motors CorporationWarren, richigan

Dr. R. R. ChambersVire PresidentSinclair Oil CorporationNew York, New York

Mr. John M. DeppDirectorCentral Me/leering DepartmentNlots.anto CompanySL Louis, Missouri

Mr. Harold F. ElkinSun Oil CompanyPhiladelphia, Pennsylvania

Mr. B. R. GebhartVice PresidentFreeman Coal Mining CorporationChicago, Illinois

Mr. James R. JonesChief Combustion EngineerPeabody Coal CompanyChicago, Illinois

Mr. Olaf KayserVice President-ManufacturingLone Star Cement CorporationNew York, New York

Mr. David LurieConsultantWyckoff, New Jersey

Dr. Glenn A. NesiyVice PresidentSenior Technical OfficerAllied Chemical CorporationNew York, New York

Dr. Arthur L. PlumleySenior Project EngineerKt esingee Development

LaboratoryCombustion Engineering, Inc.Windsor, Connecticut

Mr. James It. RookDirector of Environmental

Control SystemsAmerican Cy .namid CompanyWayne, New Jersey

Mr. T. W. SchroederManager of Power SupplyIllinois Power CompanyDecAtur, Illinois

pit

Dr. Seymour C. SchumanPrivate ConsultantPrinceton, New Jersey

Mr. R. W. ScottCoordinator for Conservation

TechnologyEsso Resehrch and Engineering

CompanyLinden, New Jersey

tilt

Mr. David SwanVice President-TechnologyKennecott Copper CorporationNew York, New York

Mr. R. A. WaltersProject Director of Smelter StudiesWestern Knapp Engineering DivisionArthur G. McKee and CompanySan Francisco, California

TABLE OF CONTENTSPale

PREFACE iii

LIST OF FIGURES xiv

LIST OF TABLES . ,,,, ...... . xvii

SUMMARY xxi

1. INTRODUCTION 1

2. BACKGROUND INFORMATION 2

2.1 DEFINITIONS 22.2 MAJOR SOURCES OF PARTICULATE MATTER 2

2.2.1 Combustion Sources 32.2.2 Industrial Sources 32,2.3 Mobile Sources 3

3. PARTICULATE SOURCES AND CONTROLS 4

3.1 INTRODUCTION 4

3.2 INTERNAL COMBUSTION ENGINES 43.2.1 Gasoline-Fueled Vehicles 43.2.2 Diesel-Powered Vehicles 5

3.3 CONTROL OF PARTICULATE EMISSIONS FROM 6STATIONARY COMBUSTION SOURCES

3.3.1 Introduction 63.3.1.1 General 63.3.1.2 Sources 63.3.1.3 Emissions 7

3.3.2 Control Techniques 83.3.2.1 Gas Cleaning 93.3.2.2 Source Relocation 103.3.2.3 Energy Substitution 103,3.2.4 Energy Conservation 123.3.2.6 Good Practice 133.3.2.6 Source Shutdown 143.3.2.7 Dispersion 14

3.4 INDUSTRIAL PROCESSES 143.4.1 Introduction 143.4.2 Iron and Steel Mills 14

3.4.2.1 Sintering Plants 143.4.2.2 Blast Furnaces 143.4.2.3 Steel Furnaces 16

3.4.3 Gray Iron Foundries 163.4.4 Petroleum Refineries 173.4.6 Portland Cement 173.4.6 Kraft Pulp Mills 18

Ix

4.7 Asphalt Melling Plants 183.4.8 Add Manufacture 19

3.4.8.1 Sulfuric Acid 193.4.8.2 Phosphoric Add 19

3.4.9 Cope Manufacture 193.4.10 Primary and Secondary Recovery of Copper, Load, Zinc,

and Aluminum 203.4.11 Soap and Synthetic Detergent Manufacture 213.4.12 Glass Furnaces and Glass Fiber Manufacture 223.4.13 Carbon Black 223.4.14 Gypsum Processing 223.4.15 Coffee Processing 233.4.16 Cotton Ginning 23

3.5 CONSTRUCTION AND DEMOLITION 233.5.1 Introduction 233.5.2 Demolition of Masonry 243.5.3 Open Burning 243.5.4 Road Dust 243.5.5 Grading Roads and Other Surfaces 243.5.6 Handling Dusty Materials 243.5.7 Sandblasting 24

3.6 SOLID WASTE DISPOSAL 253.6.1 Introduction 253.6.2 Definition of Solid Waste 253.6.3 Amounts of Solid Waste Generated 25

3.6.3.1 Disposal Methods to Minimize Air Pollution 263.6.3.2 Disposal Methods Without Incineration 273.6.3.3 Disposal Methc1ds With Incineration 29

3.6.4 Air Pollution Potential From Solid Waste Disposal Methods .. 343.6.5 Public Health Service Programs and Assistance in

Solid Waste Disposal 34

4. GAS CLEANING DEVICES 384.1 INTRODUCTION 38

4.1.1 Preliminary Selection of Equipment 394.2 SETTLING CHAMBERS 39

4.2.1 Introduction 394.2.2 Discussion of Terms 414.2.3 Design Considerations 424.2.4 Typical Applications 42

4.3 DRY CENTRIFUGAL COLLECTORS 444.3.1 Introduction 444.3.2 Types of Centrifugal Collectors 444.3.3 Design 46

4.3.3.1 Operating Pressure Drop 474.3.3.2 Dust Loading 494.3.3.3 Other Design Considerations 49

4.3.4 Typical Applications 504A WET COLLECTORS AND MIST ELIMINATORS 50

4.4.1 Introduction 604.4.1.1 Collection Theory 504.4.1.2 Egiciency 52

4.2 Equipment Description and Design 52

4.4.2.1 spray Chamber 524.4,2.2 Gravity Spray Towers 544.4.2.3 Centrifugal Spray Scrubbers 544.4.2.4 Impingement Plate Scrubbers 574.4.2.5 Venturi Scrubbers 584.4.2.6 Packed Bed Scrubbers 604.4.2.7 Self-Induced Spray Scrubbers 644.4.2.8 Mechanically Induced Spray Scrubbers 644.4.2.9 Disintegrator Scrubbers 694.4.2.10 Centrifugal Fan Wet Scrubbers 704.4.2.11 In line Wet Scrubber 704.4.2.12 Irrigated Wet Filters 704.4.2.13 Wet Fiber Mist Eliminators 724.4.2.14 Impingement Baffle Mist Eliminators 734.4.2.15 Vane-Type Mist Eliminators . . .. .. . . 754.4.2.16 Packed Bed Mist Eliminators 764.4.2.17 Mist and Vapor Suppression 764.4.2.18 Liquid Distribution 764.4.2.19 Spray Nozzles 77

4.4.3 Typical Applications of Wet Scrubbers 804.4.4 Water Disposal 80

4.4.4.1 Settling Tanks and Ponds 814.4.4.2 Continuous Filtration 814.4.4.3 Liquid Cyclones 814,4.4.4 Continuous Centrifuge 814.4.4.5 Chemical Treatment 81

4.6 HIGH-VOLTAGE ELECTROSTATIC PRECIPITATORS 814.5.1 Introduction 814.5.2 Operating Principles 814.5.3 Equipment Description 84

4.5.3.1 Voltage Control and Electrical Equipment 844.5.3.2 Discharge Electrodes 844.5.3.3 Collecting Surfaces 844.5.3.4 Removal of Collected Particulate Matter 88

4.5.4 High-Voltage Electrostatic Precipitator Equipment Design 884.5.4.1 Conditioning Systems . . ... . . .................... 884.5.4.2 Voltage, Electrical Energy. and Sectionalization

Requirements 884.5.4.3 Gas Velocity, Treatment Time, and Flow Distribution . 914.5.4.4 Collecting Surfaces and Discharge Elcc:trodes 911.5.4.5 Materials of Construction 914.6.4.6 Collected Particulate Matter Handling Systems .......... . 934.6.4.7 Controls and Instruments 934.5.4.8 Layout 93

4.6.5 Specifications and Guarantees4.5.6 Maintaining Collection Efficiency 944.5.7 Improvement of Collection Efficiency4.5.8 Typical Applications :14

4.5.8.1 Pulverized Coal-Fired Power Plants 944.5.8.2 Integrated Steel Making Operations 964 5.8.3 Cement II:Autry 96

xi

5.8.4 Kraft Pulp Mills 964.5.8.5 Sulfuric Acid 96

4.6 LOW-VOLTAGE ELECTROSTATIC PRECIPITATORS 964.6.1 Introduction 964.6.2 Major Components of Low-Voltage Electrostatic

Precipitators 974.6.3 Auxiliary Equipment 974.6.4 Design Parameters 974.6.5 Materials of Construction 1014.6.6 Typical Applications of Low-Voltage Electrostatic

Precipitators 1014.6.6.1 Machining Operations 1014.6.6.2 Asphalt Saturators 1014.6.6.3 Meat Smokehouses 1024.6.6.4 Other Applications 102

4.6.7 Air Distribution 1024.6.8 Maintenance 102

4.7 FABRIC FILTRATION 10211.7.1 Introduction 102

4.7.1.1 Range of Application 1044.7.2 Mechanisms of Fabric Filtration 10

4.7.2.1 Direct Interception 1044.7.2.2 Inertial Impaction 1044.7.2.3 Diffusion 1054.7.2.4 Electrostatic Attraction 1054.7.2.5 Gravitational Settling 105

4.7.3 Filter Resistance 1054.7.3.1 Clean Cloth Resistance 1051.7.3.2 Dust Mat Resistance 1054.7.3.3 Effect of Resistance on Design 107

4.7.4 Equipment Description and Design 1074.7.4.1 Baghouse Design 1094.7.4.2 Fab: is Filter Shupe 1114.7.4.3 Cloth Type 1134.7.4.4 Fabric Cleaning 1184.7.4.6 Fabric Selection 1214.7.4.6 Auxiliary Equipment 1224.7.4.7 Individual Collectors Versus Large Collecting Systems 123

4.7.5 Typical Applicatiors 12343.5.1 Cement Kilns 1234.7.5.2 Foundry Cupolas 1234.7.5.3 Electric Arc Steel Furnaces 1234.7.5.4 Open Hearth Furnaces 1244.7.5.5 Nonferrous Metal Furnaces 1244.7.5.6 Carlrm Black Plants 1244.7.5.7 Grain Handling Operations 124

4.7.6 Operational Practices 1254.7.7 Maintenance Procedures 1254.7.8 Safety 126

4.8 AFTERBURNERS 1264.8.1 Introduction 126

xil

8.1.1 Definition of Terms 1264.8.1.2 Advantages and Disadvantages of Afterburners 1264.8.1.3 Combustion Theory 127

4.8.2 Afterburner Design Criteria 1284.8.2.1 General 1284.8.2.2 Heat Transfer 1284.8.2.3 Reaction Temperature 1284.8.2.4 Retention Time 1294.8.2.5 Heat Recovery 1314.8.2.6 Fuel Requirements 1334.8.2.7 Modified Furnace Afterburners 1334.8.2.8 Hood ?...na Duct Design Considerations 1344.8.2.9 Gas Burners 1364.8.2.10 Construction Materials 1374.8.2.11 Typical Applications 139

5. EMISSION FACTORS FOR PARTICULATE AIRPOLLUTANTS 150

6. ECONOMIC CONSIDERATIONS IN AIR POLLUTIONCONTROL 155

6.1 SELECTION OF CONTROL SYSTEM 1556.2 COST-EFFECTIVENESS RELATIONSHIPS 1556.3 COST DATA 1586.4 UNCERTAINTIES IN DEVELOPING COST

RELATIONSHIPS 1686.5 DESCRIPTION OF CONTROL COST ELEMENTS 159

6.5.1 General 1596.5.2 Capital Investment 1596.5.3 Maintenance and Operation 162

6.5.3.1 General 1626.6.3.2 Gravitational and Centrifugal Mechanical Collectors 1636.5.3.3 Wet Collectors 1636.5.3.4 Electrostatic Precipitators 1646.5.3.6 Fabric Filters 1646.5.3.6 Afterburners 165

6.5.4 Capital Charges 1656.5.5 Annualization of Costs 1656.5.6 Assumptions in Annualized Control Cost Elements 165

6.5.6.1 Annualized Capital Cost Assumptions 1666.5.6.2 Operating Cost Assumptions 1666.5.6.3 Maintenance Cost Assumptions 166

6.6 METHOD FOR ESTIMATING ANNUAL COST OFCONTROL FOR A SPECIFIC SOURCE 166

6.6.1 General 1666.6.2 Procedure 1666.6.3 Sample Calculations 1686.6.4 Annualized Cost Variation 169

6.7 COST CURVES BY EQUIPMENT TYPE 1696.7.1 General 1696.72 Gravitational Collectors 1706.7.3 Dry Centrifugal Collectors 170

7.4 Wet Collectors 172

6.7.5 High-Voltage Eletrostatic Precipitators 172

6.7.6 Low-Voltage Electrostatic Precipitators ' 173

6.7.7 Fabric Filters 174

6.7.8 Afterburners 176

6.8 DISPOSAL OF COLLECTED PARTICULATE EMISSIONS . 1766.8.1 General 1766.8.2 Elements of Disposal Systems 1776.8.3 Disposal Cost for Discarded Material 179

6.8.4 Return of Collected Material to Process 181

6.8.6 Recovery of Material for Sale 182

7. CURRENT RESEARCH IN CONTROL OF PARTICULATEMATTER 183

8. BIBLIOGRAPHY 185

AUTHOR INDEX 209

SUBJECT INDEX

UST OF FIGURESFigure2-1 Sources of particulate matter and quantities produced in tons 2

per year3-1 Motor vehicle emission control system 6

3-2 Costs of incinerator at three levels of control of particulateemissions 31

4-1 Composite grade (fractional) efficiency curves based on testsilica dint 40

4-2 Terminal velocities of spherical particles in air 424-3 Balloon duct 42

4-4 Baffled expansion chamber with dust hopper 434-5 Dust settling chamber 434-6 Multiple-tray dust collector 434-7 Conventional reverse-flow cyclone 444-8 Axial inlet cyclone 454-9 Straight-through-flow cyclone 454-10 Dynamic cyclone showing method by which dust is dynamically

precipitated and delivered to the storage hopper 464-11 Various types of cyclone dust discharge 484-12 Cyclones arranged in parallel 49

4-13 Cyclones arranged in parallel 49

4-14 Arrangement of nozzles in smoke stack spray system 534-15 Typical layout for spray tower 554-16 Centrifugal spray scrubbers 564-17 Impingement plate scrubber 674-18 Venturi scrubber may feed liquid through jets (a), over a

weir (b), or swirl them on a shelf (c) 694-19 Flooded disk (variable throat orifice) scrubber 60

4-20 Multiple-venturi jet scrubber 61

4-21 Vertical venturi scrubber 624-22 Wet scrubber packings 634-23 Packed-bed scrubbers 64

xiv

Il

Page

4-24 Flooded-bed scrubber 654-26 Floating-ball (fluid-bed) packed scrubber 664-26 Self-induced-spray scrubbers 674-27 Mechanically induced spray scrubbers 684-28 Centrifugal fan wet scrubber 694-29 In line wet scrubber 704-30 Wetted and impingement plate filters . ......... 714-31 Low-velocity filtering elements 734-32 High-velocity filtering elements 744-33 Wire mesh mist eliminators 744-34 Coke quench mist elimination baffle system 754-35 Details of baffle design 754-36 Streamline mist eliminator baffles 764-37 Screen and mist eliminator details . ... 'i64-38 Bed of Bed saddles added to discharge stack 764-39 Spray nozzles commonly used in wet scrubbers 784-40 Weir and sieve plate liquid distributors commonly used in

packed towers 794-41 Multiple precipitator installation in basic oxygen furnace plant . 824-42 Detarrer precipitators installed h steel mill 834-43 Schematic view of a flat surface-type electrostatic precipitator 854-44 Schematic view of tubular surface-type electrostatic rrecipitator 854-45 Cutaway view of a flat surface-type electrostatic precipitator 864-46 Cross-sectional view of irrigated tubular blast furnace

precipitator .874-47 Typical double half wave silicon rectifier with twin output

bushings 884-48 Internal view of one type of reeifier control console showing

component parts 894-49 Electrostatic precipitator collecting plates and discharge

electrodes 904-50 Hopper discharge valves. (a) Rotary valve and (b) swing

valve 914-51 Electrostatic precipitator rapper mechanisms. (a) Pneumatic

impulse rapper, (b) Magnetic impulse rapper, and(c) Pneumatic reciprocating rapper 92

4-52 Variation of precipitato- "fficiency with sparking rate for agiven fly ash precipitator 93

4-53 Electrostatic precipitator installed after air heater in powerplant steam generator system 95

4-54 Operating principle of two-stage electrostatic precipitator 984-55 Two-stage precipitator used to control oil mist from machining

operations 994-56 Two-stage electrostatic precipitator with auxiliary scrubbers,

mist eliminator, tempering coil, and gas distribution plate(top view) 100

4-57 Efficiency of two stage precipitator as function of velocityfor several industrial operations 100

4-58 Typical simple fabric filter baghouse design 1034-59 Streamlines and particle trajectories approaching filter

elements 1044-60 System analysis for fabric filter collector design 107

xv

4-61 Pressure chop versus filter ratio for fabrics on 60-minutePert

cleaning cycle for electric .furnace dust 1084-62 Typical performance of reverse-jet baghouses using felted

fabrics on a variety of dusts (dust load versus filteringratio at 3.5 in. w.c. pressure drop) 109

4-63 Open pressure baghouse 111

4-64 Open pressure baghouse unit showing installation without aseparate clean gas housing 112

4-65 Closed pressure baghouse 1134-66 Closed pressure baghouse unit 1144-67 Closed suction baghouse 1164-68 Closed suction concrete baghouse unit 1154-69 Typical fiat or envelope dust collector bag 1154-70 Typical round or ttlhular dust collector bag 1164-71 Typical multi-bag dust collection system 1164-72 Bottom entry design uni-bag 1164-73 Top entry design uni-bag 1164-74 Basic fabric weaves used for woven filter bags 1174-75 Mechanical shaking of bottom entry design uni-bag dust

collector 1184-76 Air shaking wind-whip cleans dust collector bags 1194-77 Bubble cleaning of dust collector bags 1194-78 Jet pulse dust collector bag cleaning 1194-79 Reverse air flexing to clean dust collector bags by repressuring . 1204-80 Sonic cleaning of dust collector bags 1204-81 Repressuring cleaning of dust collector bags 1204-82 Cloth cleaning by reverse flow of ambient air 1214-83 Reverse jet cleaning of dust collector bags i214-84 Effect of cleaning frequency on filter resistance in reversejet

baghouse 1254-85 Effect of air velocity and particle diameter on the combustion

rate of carbon 1284-86 Combustion efficiency of catalytic afterburner 1294-87 Effect of temperature and velocity on abatement effectiveness:

spiral-wound metal foils catalyst support 1294-88 Typical direct-fired afterburner with tangential entries for

both fuel and contaminated gases 1314-89 Portable 'anopy hood with stack afterburner 1324-90 Afterburner energy requirements with fume energy content

and temperature parameters 1324-91 Counter-flow type 1324-92 Parallel-flow type 1S24-93 Cross-flow type 1324-94 Fixed-bed, pebble-stone, regenerative desteucher 1334-95 Direct recirculation of combustion gases to recover heat 1344-96 Heat exchanger to recover heat from combustion gases 1344-97 Integration of fume disposal from a kettle cooking operation with

factory make-up air heating 1354-98 Packed bed flame arrester 1354-99 Corrugated metal flame arrester with cone removed and tube

bank pulled partly out of body 1364-100 Dip leg flame arrester 136

xvi

4-101 Cross-sectional view of open-type inspirational premixPope

burner 136

4-102 Cross-sectional view of forced air, premix, multiple portburner 137

4-103 Multiple-port high-intensity premix burner 1374-104 Service temperature ranges for refractories 1394-105 Degree of refraction for alumina-silica system products .. 142

6-1 Criteria for selection of gas cleaning equipment 1666-2 Cost of control 1576-3 Expected new cost of control 1576-4 Diagram of cost evaluation for a gas cleaning system 1606-5 Purchase cost of gravitational collectors 1706-6 Installed cost of gravitational collectors 1716-7 Purchase cost of dry centrifugal collectors 171

6-8 . Installed cost of dry centrifugal collectors 171

6-9 Annualized cost of operation of dry centrifugal collectors 1716-10 Purchase cost of wet collectors 1726-11 Installed cost of wet collectors 1726-12 Annualized cost of operation of wet collectors 1726-13 Purchase cost of high-voltage electrostatic precipitators 1736-14 InstaPeri cost of high-voltage electrostatic precipitators 1736-16 Ann, alized cost of operation of high-voltage electrostatic

precipitators 1736-16 Purchase cost of low-voltage electrostatic precipitators 1746-17 Installed cost of low-voltage electrostatic precipitators 1746-18 Annualized cost of operation of low-voltage eleqrostatic

precipitators 1746-19 Purchase cost of fabric filters 1746-20 Installed cost of fabric filters 1766-21 Annualized cost of operation of fabric filters 1756-22 Purchase cost of afterburners 1766-23 Installed cost of afterburners 1766-24 Annualized cost of operation of afterburners 1776-26 Flow diagram for disposal of collected particulate material

from air pollution control equipment 1796-26 Economic cost of dust control with valuable material recovered:

industrial viewpoint 181

LIST OF TABLESTable1 Typical pressure drops and efficiency ranges for gas cleaning

devices used for stationary combustion sources xxi2 Industrial process control summary xxii3 .Advantages and disadvantages of collection devices xxiv4 examples of particulate emission factors xxv5 Installed costs of control equipment xxv6 Generalized annual operating and maintenance cost

equations for control equipment xxv3-1 Comparison of motor vehicle particulate emissions with total

particulate emissions for selected areas 43-2 Estimated 1966 United States energy consumption by selected

consumer (10" Btu)

xvii

POPE

3-3 Common uses of various fuel-burning equipment 7

3-4 Estimated amount and control status for particulate emissionsfrom stationary combustion sources in 1966 8

3-5 Optimum expected performance of various types of gascleaning systems for stationary combustion sources . ....... 9

3-6 Comparison of energy substitution alternatives for electricpower generation 11

3-7 Comparison of energy substitution alternatives for stationarycombustion sources of less than 10 million Btu/hr input ... 11

3-8 Comparison of energy substitution alternatives for stationarycombustion sources of 10 million to 100 million Btu/hr input 12

3-9 Trends in efficiency of coal, oil, and gas use in United States 123-10 Industrial process summary 153-11 Steel production, percentage by process 163-12 Average solid waste collected 263-13 Maximum demonstrated collection efficiency of incinerator

control equipment 294-1 Manufacturers' shipments of industrial gas cleaning equipment

by end use in 1967 ....... 384-2 Use of particulate collectors by industry 404-3 Relationship between particle size range and cyclone efficiency

range 474-4 Representative performance of centrifugal collectors 504-5 Applications of centrifugal collectors 514-6 Typir-., industrial application of wet scrubbers 804-7 Industrial operation of two-stage precipitators 1014-8 Control mechanism for particle size collection 1054-9 Filter resistance coefficients tK) for industrial dusts on woven

fabric filters 1064-10 Physical characteristics of bag fabrics tested in pilot plant 1084-11 Recommended maximum filtering ratios and dust conveying

velocities for various dusts and fumes in conventional bag-houses with woven fabrics 108

4-12 Recommended maximum filtering ratios and fabric for dustand fume collection in reverse-jet baghouses 110

4-13 Filter fabric characteristics 1226-14 Gas burner classifications 1384-15 ASTM classification of fire clay refractories 1394-16 Commonly used castable fire clay refractories 1394-17 General physical and chemical characteristics of classes of

refractory brick ' 1404-18 Summary of afterburner applications and literature

references 1415-1 Particulate emission factors 1506-1 Air pollution control equipment collection efficiencies 1556-2 Approximate cost of wet collectors in 1965 1586-3 Total installation cost for various types of contr.)l devices

expressed as a percentage of purchase costs 1606-4 Conditions affecting installed cost of control devices 1606-5 Annual maintenance costs for all generic types of control

devices 1616-6 Miscellaneous cost and engineering factors 161

xviii

Pape

Hourly fuel costs 1656-8 Illustrative presentation of annual costs of control for 60,000

acfm wet scrubber (dollars) 1696-9 Costs of specific disposal systems 1806-10 Cost of ash disposal by electric utilities 181

xix kX

SUMMARY

PARTICULATE SOURCESParticulate material found in ambient air

originates from both stationary and mobilesources. Of the 11.5 million tons of particu-late pollution produced by industrial, com-mercial, and domestic sources in 1966, 6million tons were emitted from industrialsources, including industrial fuel burning;6 million tons from power generation, incin-eration, and space heating; and 0.5 millionton from mobile sources.

The following techniques are in use forcontrolling the source or reducing the effectsof particulate pollution:

1. Gas cleaning2. Source relocation3. Fuel substitution4. Process changes6. Good operating practice6. Source shutdown7. Dispersion

Internal Combustion EnginesAlthough particulate emissions from in-

ternal combustion engines are estimated tocontribute only 4 percent of the total par-ticulate emissions on a nationwide basis,they do contribute as much as 38 percentin certain urban areas. The relative percent-ages of particulate emissions for this andother source categories differ from one areato another depending on automobile density,degree of stationary source control, andtypes of sources present in the area.

For each 1000 gallons of fuel consumed,diesel-fueled engines produce about 110pounds of particulate matter. Gasoline-fueled engines produce about 12 pounds per100 gallons of fuel consumed.

Gasoline engine-produced particulate mat-ter emanates from the crankcase and ex-haust gases. It consists of carbon, metallicash, aerosol hydrocarbons, and metallic par-ticles,

The particulate matter emitted from adiesel engine comprises carbon and hydro-carbon aerosols. Control of diesel engineemissions effects reduction in smoke.

Stationary Combustion Sources

In the United States more than 29 millionstationary combustion sources are currentlyin operation. About 2 percent are fired withcoal, 61 percent are fired with gas, and 37percent are fired with fuel oil. The relativeusage of fuels on a Btu basis shows coal tobe 32 percent, natural gas 49 percent, andfuel oil 19 percent.

Types of gas cleaning devices currentlybeing used for stationary combustion sourcesare listed in Table 1. Newer control systemsare now being installed which will be usedto control both particulate matter and sulfuroxides.

Industrial SourcesIndustrial processes, including industrial

fuel burning, discharged an estimated 6.0million tons of particulate materials in 1966.This amounts to more than 50 percent of thetotal particulate pollution on a nationwidebasis. Major pollutants are dusts, fumes, oils,smoke, and mists.

Table 2 presents a summary of importantindustries, their pollutant sources, particu-

Table 1. TYPICAL PRESSURE DROPS AND EF-FICIENCY RANGES FOR GAS CLEANING DEVICES USED FOR STATIONARY COMBUSTIONSOURCES

UnitPressure

drop, Efficiency,in. H,0 percent

Settling chambers 0.6 20-60Large-diameter cyclones 0.6-4.0 30-65Small-diameter cyclones 2-8 70-90Electrostatic precipitator 0.1-0.6 76-99.6

xxi

Table 2. INDUSTRIAL PROCESS AND CONTROL SUMMARY

Industry or process Source of emissions Particulate matter Method of control

Iron and steel mills Blast furnaces, steelmaking furnaces,sintering machines.

Gray iron foundries Cupolas, shake out systems,core making.

Metallurgical (non-ferrous). Smelters and furnaces

Petroleum refineries Catalyst regenerators,sludge inciner,..tors.

Portland cement Kilns, dryers, materialhandling systems.

Kraft paper mills Chemical recovery furnaces,me!: tanks, lime kilns.

Acid manufacture-phos- Thermal processes, phos-phoric, sulfuric. phate rock acidulating,

grinding and handlingsystems.

Coke manufactoing Charging and dischargingoven cells, quenching,materials handling.

Glass and glass fiber Raw materials handling,glass furnaces, fiberglassforming and curing.

Coffee processing Roasters, spray dryers,waste heat boilers,coolers, conveyingequipment.

Iron oxide, dust, smoke....

Iron oxide, dust, smoke, oil,grease, metal fumes.

Smoke, metal fumes, oil,grease.

Catalyst dust, ash fromsludge.

Alkali and process dusts...

Chemical dusts

Acid mist, dust

Coal and coke dusts, coaltars.

Sulfuric add mist, rawrnaterizis dusts, alkalineoxides, resin lAtosolt.

Chaff, oil aerosol, ash fromchaff burning, dehy-drated coffee dust.

Cyclones, baghouses,electrostatic precipita-tors, wet collectors.

Scrubbers, dry centrifugalcollectors.

Electrostatic precipitators,fabric fitters.

High-efficiency cyclones,electrostatic precipita-tors, scrubbing towers,baghouses.

Fabric filters, electrostaticprecipitator, mechanicalcollectors.

Electrostatic precipitators,venturi scrubbers.

Electrostatic precipitators,mesh mist eliminators.

Meticulous design, opera-lion, and maintenance.

Glass fabric filters, after-burners.

Cyclones, afterburners,fabric filters.

late pollutants, and air cleaning techniques(equipment) presently in use.

Construction and DemolitionThe principal demolition, construction, and

Mated operations that generate particulateair pollution are:

1. Demolition of masonry2. Open burning3. Movement of vehicles on unpaved

roads4. Grading of earth5. Paving of roads and parking lots6. Handling and Welling of paving ma-

terials7. Sandblasting of buildings8. Spray painting

Control of the above operations is accom-plished by various means which include hood-ing and venting to air pollution control equip-silent, wetting (tow/ working surfaces withwater or oil, and using sanitary landfill.

xtii

Solid Waste DispotatAlthough solid waste disposal by inciner-

ation accounts for less than 10 percent ofthe total particulate pollution (1 million tonsin 1966), it does, however. inspire many com-plaints about ail pollution. Of the 190 mil-lion tons of solid wastes colected in 1967,86 percent went into land disposal sites, 8percent was burned in municipal inciner-ators, and 6 percent was disposed of in sani-tary landfills. Since open burning is practicedat three-fourths of the land disposal sites,particulate emissions from these sites con-tribute significantly to air pollution arisingfrom the disposal of solid waste.

Over 70 percent of existing municipal in-cinerators were installed before 1960, andlack adequate provisions for eliminating par-ticulate emissions.

An obvious means of reducing the Ai, pol-lution resulting from solid waste disposals is

to use rich non-incineration methods for dis-posal as follows:

1. Sanitary landfill2. Composting3. Shredding and grinding4. Dispersion (hauling to another lo-

cale)These methods contribute little to air pol-

lution problems.It is estimated that measures to upgrade

existing land disposal sites, and thus deaway with open burning, will cost as muchas $230 million per year for 5 years.

Where incineration is used for solid wastedisposal, the principal particulate pollutantemitted is fly ash. Its removal from Oh entgas streams is accomplished by low pressuredrop (0.5 inch ILO) scrubbers, or settlingchambers.

The estimated cost of upgrading or re-placing existing inadequate municipal incin-erators is $225 million, of which $75 millionwould be for air pollution control equipment.

GAS CLEANING DEVICESIt has Leen estimated that total expendi-

tures in 1966 on industrial air pollution con-trol equipment in the United States wereabout $235 million. Value of shipments of theindustrial gas cleaning iipment industryin 1967 was double the 1963 figure, and thebacklog of orders recently nearly equalled ayear's produdive output. Undoubtedly legis-lative pressure and local pollution controlregulations have supplied the impetus forsuch rapid growth in this industry.

The selection of gas cleaning equipmentis far from an exact science and must bebased on characteristics of particle and car-rier gas. and process, operation, construc-tion, and economic factors. Information onparticle site gradation in the inlet gas streamis important in the proper selection of gascleaning equipment. Particles larger than50 microns may be removed satisfactorilyin inertial and cyclone separators and sim-ple, low-eriergy wet scrubbers. Particlessmaller than 1 micron can be arrested effec-tively by electrostatic precipitators. high-energy scrubbers, and fabric filters.

Table 3 lists advantages and disadvan-

tages in applicability of each of the generaltypes of air cleaners to given situations.

EMMISSION FACTORS

Emission factors may be used to estimateemissions from sources for which accuratestack test results are unavailable. Processemission factors for some selected sourcetypes ale presented in Table 4.

ECONOMICS

Air pollution control is viewed not onlfrom the standpoint of available technologybut also with respect to the econcmic feosi-bility of control methods and/or equipment.

Among the cost elements relevant to anair pollution control problem are:

1. Capital costs of rentrol equipment.2. Depreciation of all control equipment.3. Overhead io.-ts including taxes, in-

surance, and '-terest for controlequipment.

4. Operation and maintenance costs.5. rollected waste material disposal

costs.6. Other capital expenditures for re-

search and development, land, andengineering studies to determine anddesign optimum control system.

Many of these elements differ from one in-stallation to another. Table 6 lists major col-lector types amt their approximate installedcosts for operational air flow rates. The in-stalled costs (purchase cost, transportation,and preparation for on line operation) areaverage costs for typical control equipment.

Table 6 presents generalized operating andmaintenance cost equations for various typesof control equipment.

11111LIOGRAPIIV

A list of references follows each section ofthis document. Other references relating tocontrol technology for generic sources of par-ticulate air pollutants are cited in the bibli-ography, which comprises the final section.Although all of the articles cited in the bibli-ography do not necessarily reflect the mostmodern control practices, they do provideuseful background material on the controltechnology for particulate air pollutants.

Table LADVANTAGES AND DISADVANTAGES OF COLLECTION DEVICES

Collector Advantages Disadvantages

Gravitational Low pressum loss, simplicity of design andmaintainance.

Cyclone Simrlicity of design and rnaintainanceLittle floor space requiredCry continuous disposal of collected dusts....

Low to moderate pressure loss.Handles large particles.Handles high dust loadings.Temperature independent.

Wet collectors__ Simultaneous gas absorption and particle re-moval.

Electrcstaticmelt ttator.

Ability to cool and clean high-temperature,moisture-laden gases.

Corrosive gases and mists an be recoveredand neutralised.

Reduced dust explosion riskEfficiency can be varied

99+ percent efficiency obtainable ...Very small particles can be collected.....

Particles may be collected wet or dry

Pressure drops and power requirements aresmall compared to other high-effickncycollectors.

Maintenance is nominal unless corrosive oradhesive materials are handled.

Few moving partsCan be operated at high t.vnperatures (550'

to IMO' F.).Fabric filtration..... Dry collection possible

Decrease of performance is noticeable

Afterburner,direct flame.

Afterburner,catalytic.

Collection of small particles possible.High efficiencies possibleHigh removal efficiency of submkron odor-

erasing particulate matter.Simultaneous disposal of combustible gaseous

and particulate matter.Direct dblosal of non-toxic gases and wastes

to the atmosphere after combustion.Passible heat recoveryRelatively small space requirement.Simple constructionLow maintenanceSame as direct Aare, afterburnerCompared to direct flame: reduced fuel re-

quirements., reduced temperature, insula-tion requirements, and fire hazard.

Much space required. Low collection efliciency.

Much head room required.Low collection efficiency of small particles.Sensitive to variable dust loadings and flow

rata.

Corrosion, erosion r roblerr s.Added cost of wastewater treatment and rec-

lamation.Low efficiency on submicron particles.

Ccltamir.stion of effluent stream by liquidentrainment.

Freezing problerra in cold wet ther.Reduction in btrlancy and plume rise.Water vapor contributes to visible plume

under some atmospheric conditions.Relatively high initial cost.

Precipitators are sensitive to variable dustloadings or flow rates.

hesistivity causes some material to be eco-nomically tificolledable.

Precautions are reqdired to safeguard person-nel from high voltage.

Collection efficiencies can deteriorate gtadu-ally and imperceptibly.

Sensitiviti to filtering velocity.High-temperatu-e gases must be cooled to

200' to 550' r.Affected by relative humidity (condensation).Susceptibility of fabric to chemical attack.High operational cost. Fire hoard.

Removes only combustibles.

High initial cost.Catalysts subject to poisoning.

Catalysts require reactivation.

Table 1.EXAMPLES OF PARTICULATE EMISSION FACTORS

Source Specific process Particulate emission rate,uncontrolled

AircraftSolid want. disposalPhosphoric acid

mtnufacturing.Sulfuric acid

manufacturing.Food and agricultural

Feed and grafi' millsPrimary metal industry_

Secondary 'metal industry...

Four engine fan jetOren burning dumpThermal process

Contact process

Coffee roasting, direct firedCotton ginning and incineration of trashGrit ri.) t.perationIron and steel manufacturing furnace, open

hearth (orb gen !Amu)Aluminum sr.t-lting, chlorination-lancing.Brats and bronze smelting reverberatory

furnace.Grey iron roundly cupola

7.4 lb/flight.16 lb/ton of refuse.0.2-10.8 lb/ton of phosphorus burned.

0.8-7.6 lb/ton of acid produced.

7.6 lb/ton of green beans.11.7 lb/bale of cotton.6 Ih/ton of product.22 lb/tun of steel.

1000 lb/ton r: chlorine.26.8 lb/ton of meta charged.

17.4 ih/ton of metal charged.

Table S.INSTALLE0 COSTS OF CON1ROL EQUIPMENT

Collector type

Approximste installed cost, in thourands of dollars

Gas flow rates(1000 actual cubic feet per minute)

2 5 10 15 100 300 600

Gravity 0.6 1.2 2.6 16 28Mechanical 4 13 23Wet 7.6 10 114 65 160High-velar electrostatic precipitator 83 120 263 416Low-voltage electrostatic precipitOor 13 24 105 200Fabric filter:

High temperature (660' F.) 80 88 166 430 720

Medium temperature (260' F.) 16 46 82 226 376Afterburner, direct flame catalytic 8.2 12 18

16 20 29

Table 4.--GENEP.A1.12ED ANNUAL OPERATING AND MAIN1rENANCE COST EQUATIONS FOR CON.TROL EQUIPMENT

Collector

Mechanical centrifugal collector

Wet collector

Electrostatic precipitator

Fabric Mter

Afterburner .

Generalized equation

G.s r 0.7457 PHK +ML 6336 E

0..8[0.7157 1-1K (Z+---911--)80 +WHL+M19

r 03437 PHK +M}L 6336 E

43.sLrt_1.74$7 PHK 4FH+3i

1/41.11-k

XIV

Where:- annual costs, dollars, for operating and

maintenanceS - design capacity of the obit, actual cubic feet

per minute (acfm)P -pressure drop, inches of wterH ...hours of operation annuallyK -cost of electricity; dollars per kilowatt-hourE -fan efficien:y expressed as decimalM.-maint4nar.ce cost per actin, dollars per cfm

xxvi

F -fuel cost, dollars per acfm per hourW.-make-up liquid rate in gallons per hour per

acfmL -cost of liquid in dollars per gallonZ -total power input required for a specified

scrubbing efficiency, horsepower per acfmJ - kilowatts of electricity err acfm

-elevation for pumping of liquor in circuit'.th,a syslAm for colecter. feet

Q 'rater gallons per acfm

1. INTRODUCTION

Pursaant to authority delegated to theCommissioner of the National Air PollutionControl Administration, Control Techniquesfor Particulate Air Pollutants is issued in ac-cordance with Section 101c of the Clean AirAct (42 U.S.C. 1857c-2b1).

Particulate matter in the atmosphere isknown to have many adverse effects uponhealth and welfare, and red teflon rf emis-sions of this pollutant is of prime importanceto any effective air pollilion abatement pro-pan.. Partierlate pollutants originate fromel variety of sources, and the :missions varywidely in physical and chemical eharacterls-tics. Similarly, the availMe control tech-niques vary in type, application, effective-ness, and cost.

The control techniqu .1 described hereinrepresent a broad spectrum of informationfrom many engineering and other technicalfields. The devices, methods, and principleshave been developed and us..NI over manyyears, and much experience has been gainedin their application. They are recommendedas the techniques generally applicable to thebroad range of particulate emission controlproblems.

The proper choice of a method, or com-bination of methods, to be applied to anyspecific source depends on many factors otherthan the characteristics of the source itself.While a certain percentage of control, for ex-

ample, may be acceptable for a single source,a much higher degree may be required for thesame source when its emissions blend withClose of others. This document provides acomprehensive review of the approachescommonly recommended for controlling thesources of particulate air pollution. It doesnot review all possible combinations of con-trol techniques that might bring about morestringent control of each individual mime.

The many aFricultural, iercial, do-mest'c, industrial, tied municipal processesr.nd activities that generate particulate air?ol!utants are described individually in thisdocument. The various tech iques that canbe applied to control emissicn: nt oarticulatematter frcal these source% are reviewed andcompared. A technice.I consideration of themost important types of gas cleaning devicesforms a major segment, while sections onsource evaluation, equipment costs and cost-effectiveness analysis. and current researchand development also are included. The bibli-ography contains important reference arti-cles, arranged according to applicable proc-esses.

While some data are presented on quanti-ties of particulate matter emitted to theAtmosphere, the effects of particulate matteron health and welfare are considered in acompanion document, Air Quality Criteriafor Particulate Matter.

1

2. BACKGROUND

2.1 DEFINITIONS

This section contains general definitions ofthe terms used throughout this document.

Pollutant or Contaminantany solid, liq-uid, or gaseous matter in the outdoor atmos-phere which is not normally present in nat-ural air.

Particulate Matteras related to controltechnology. any material, except unrombinedwater, that exists as P, solid or liquid in th.;atmosphere or i I a gas stream at standardconditions.

It h import' It that standard conditionsfor the measurement of particulate matterbe ircluded with its definition. Some cern-pounes are no; solids or liquids et stack con-diticas but coll,1 'se in the ambient atmos-phere. Unless s',an lard conditions for messurement of particulate matter are definc4,these materials would nut be considered par-ticulate and subject to control.

Aerosol --,a dispersion in gaseous media ofsolid or liquid ',Articles of microscopic size,such as smoke, fog, or mist.

Dustsolid particles predominantly largerthan colloidal site and capable of temporarysuspension in air and other gases. Derivationfrom larger masses through the applicationof physical force is usually implied.

Fly Ashfinely divided particles of Ash en-trained in flue gasses arising from the com-bustion of fuel. The particles of ash may con-tain unburned fuel And minerals.

Fogvisible aerosols in which the dis-persed phase is liquid. In meteorology, fog isa dispersion of water or ice.

Fumeparticles formed by condensation,sublimation, or chemical reaction, of whichthe predominant part. by weight. consist ofparticles smaller than 1 micron. Tobaccosmoke and condensed metal oxides are ex-amples of fume.

Mist 'ow- concentration dispersion of rel-atively small liquid droplets. In meteorology,

2

INFORMATION

the term mist applies to a light dispersion ofwater droplets of sufficient size to fall fromthe air.

Particlesmall, discrete mass of solid orliquid matter.

Smoke--small gasborne particles result-ing from incomplete combustion. Such parti-cles consist predominantly of carbon andother combustible material, and are presentin sufficient quantity to be observable inde-pendently of other solids.

Sootan agglomeration of carbon parti-cles impregnated with "tar," formed in theincomplete combustion of carbonaceous ma-terial.

Spraysliquid droplets formed by me-chanical action.

2,2 MAJOR F,OURCIS OF PARTICULATEMATTER

An estimated 11.5 million tons of particu-late matter was emitted from zidustrial, com-mercial, and domestic sources in the UnitedStates during 1966.' Particulate matter,emitted from sources other than these, in-cludes ocean salt, volcanic ash, wind erosion

imCINEAAVOMI malION

SPACEHI AT (KOI MILLION

MORE0.5 MILLION

rIct-Its 2-I. Sources of particulate matter and qua-lities produced in VAis pa year.

and roadway dust, forest fire smoke, andplant seed and pollen. Figure 2-1, which Isbased on Reference 1 and gasoline and fuelconsumption figures, shows that industrialsources of particulate matter, including in-dustrial fuel burning, emit 6 million tons ofparticulate matter annually. About 6 milliontons result annually from power generation,incineration, and space heating. Mobile(transportation) sources emit the remaining0.6 million tons.

2.2.1 Combustion SourcesCombustion of coal and oil results in all an-

nual emission of 4.6 million tons of particu-late matter that is principally fly ash fromcoal combustion. Emission sources are dis-cussed in Section 3.3 of this report.

Refuse burning, both in incinerators andIn dumps, produces approximately 1 milliontons of particulate matter annually. Much ofthis particulate matter is dust, fume, smoke,fly ash, and large pieces of partially burnedrefuse. Although refuse burning creates lessthan 15 percent of the total particulate mat-ter emitted h. the United States, such emis-sions are oually concentrate:I in heavilypopulated areas and have a more significantimpact on the population than these statisticsmay suggest.

2.2.2 Industrial SourcesParticulate emissions from industrial proc-

esses consist of dust, fume, smoke, and mist

'Does not include agricultural burning and forestAres.

arising largely from combustion and loss ofprocess materials or products to the atmos-phere. Such emissions totaled 6 million tonsin 1966. Major industrial sources are listedand discussed in Section 3.4 of this report.

In some industrial processes, efficient col-lection of particulate matter increases over-all plant operating efficiency by recovering aportion of the product that would otherwisebe lost to the atmosphere. Dust collectorsused in cement plants, grain handling opera-tions, and carbon black plants can recovervaluable products.

2.2.3 Mobile SourcesEmissions from mobile sources, which total

approximately 0.6 million tons of particulatematter per year, are largely caused by theburning of fuels In motor vehicles. Automo-bile exhaust is the largest source of particu-late matter in this category. It is character-ized by an extremely large number of fineparticles consisting of organic and inorganicmaterials, including lead. Particulate emis-sions from diesel engines are more concen-trated and may cause a visible plume. Mr-craft, especially jet-powered planes, alsoproduce visible particulate emissions. Theemission rate is greatest during takeoff andlanding operations when the engines operateunder conditions of a high ratio of fuel to air.

REFERENCE FOR SECTION 21. "The Sources of Air Pollution and Their Con-

trol." U.S. Dept. of Health, Education, and Wel-feet-, Dir. of Air Pollution, Washington,PHS-Nb-1645, 1966.

3

3. PARTICULATE SOURCES AND CONTROLS

3.1 INTRODUCTION

The earliest approaches to air pollutioncontrol, used in England over 200 years ago,were the restriction of smoke releases andrelocation of sources to "offensive tradeszones." The latter was used particularlywhen the odor of the some was offensive.Relocation is still used, or at least considered,by operators of some pollution sources as analternate to emissions control. In most in-stances, however, relocating a pollutionsource to a remote area may only postponethe adoption of emissions control.

Many sources such as transportation,space heating, and solid wastes disposal areinherent in population centers. All generateparticulate air pollution in moan areas. Al-though remote power generation and longdistance hauling of solid wastes are poibte,automobiles, busses, incinerators, and homefurnaces and manufacturing and commercialoperations that require workers will, in alllikelihood, continue to operate in our cities.

To appreciate the air pollution problemfacing the United States. it is necessary tohave some understanding of the sources ofair pollution and the means of controllingthem. The multitude of small sources closestto the average citizenautomobiles. homefurnaces, on-site incineratorsare often theleast effectively controlled. High-efficiencycontrol equipment use is limi Yl almost en-tirely to certain steam-electric generatingstations and industrial operations, particu-larly the large installations. Most of the high-efficiency emissions controls are being 1e-s-eloped for such sources t.a steel mills, steam-electric generating stations. petroleum re-fineries, and chemical plants. The most prom-ising areas of improvement for small sourcesinvolve basic changes in source operationcleaner fuels. tutomobile engine modifica-tions, and improved means of solid wastesdisposal.

4

3.2 INTERNAL COMBUSTION ENGINES

Although stationary sources are the majorcontributors of particulate matter, the motorvehicle contributk,s a significant amount ofparticulate matter to the atmosphere. Theranking of the motor vehicle emissions in anurban community is a function of the relativemagnitude of the vehicular and industrialactivities; the extent to which coal, residualNee., and refuse are burned; and the extentand effectiveness of the air pollution controlmeasures used. Each 1,000 gallons of fuelconsumed by diesel engines produces about110 pounds of particulate matter and gaso-line engines produce about 12 pounds of par-ticulate for every 1,000 gallons consumed.' Ofthe total annual emission of 11.5 million tonsof particulate matter, motor vehicles con-tribute approximately 4 percent or about500,000 tons.

Table 3-1 presents examples of contri-bution by motor vehicles to particulate emis-sions in different communities.3.2.1 Gfoo linc-Fueled Vehicles

Particulate matter is emitted in the exhaust and crankcase blowby gases of gaso-

Table 3-1.COMPARISON OF MOTOR VEHICLEPARTICULATE EMISSIONS WITH TOTAL PAR.TICULATE EMISSION. FOR SELECTEDAREAS

Particulate matter, tons/yr

Metropolitan areaPercentof total

Total Motorvehicles

frommotor

vehicles

Washington, D. C. 5,000 5,700 16New YorkNorthern

New Jersey 2:31,000 3.S,800 15Kansas City 60,000 5,000 8Jacksonville, Florida 11,000 600 4

St. Louis 147,000 4,700 3Los Angeles County 45,000 16,400 38

line-fueled engines. Carbon, metallic ash,hydrocarbons in aerosol form, and metallicmaterials present in engine systems are

Metal-based particles result almost en-tirely from the use of lead antiknock com-pounds in the fuel; however, metallic lubri-cating oil additives and engine wear particlesare also present. Carbon and some of thehydrocarbon aerosols result from incompletecombustion of fuel. The rest of the aerosolsare emitted to the atmosphere from engineswith vented crankcases or are produced bycrankcase oil that leaks past the piston ringsinto the combustion chamber and is emittedunburned with the exhaust gases.

Particulate matter in automobile exhaustamounts to approximately 6 percent byweight of the amount of gaseous hydrocarbonemitted. It consists of lead compounds, car-bon particles, motor oil, and nonvolatile re-action products formed from motor oil in thecombustion zone. It is suspected that thesereactions involve the formation of high-mo-leculat.-weight olefins, and carbonyl com-pounds.

Particles in blowby gases consist almostentirely of unchanged lubricating oil. As avery rough approximation, the amount ofmaterial emitted in blowby gases is one-thirdto one-half the amount emitted in the ex-haust. The same approximate ratio appliesto either particulate emission or gaseous hy-drocarbon emission. Blowby emissions are in-fluenced to a greater extent than exhaustemissions by mechanical condition of theengine.'

Partial control of vehicle particulate emis-sions has been in effect nationally since 1963.Beginning with the 1968 automobile models,the particulates in crankcase gases werecompletely controlled (Fig. 8-1). It is pos-sible the exhaust emission control measuresemployed in the 1968 model passenger carsreduce the emissions of some particulates.

Technology for the control of lead in exhaunt emissions is in the developmentalstage. The National Air Pollution ControlAdministration is presently evaluating twoprototype electrogasdynamic precipitatorsfor gasoline and diesel rfiotor vehicle ex-hausts.'

Lead emissions may also be controlled byrestricting the concentration of lead anti-knock compounds that are permitted in thefuel. The American Petroleum Institute indi-cates that the additional cost of unleadedfuel would be 1.8 to 4.7 cents per gallon.Petroleum processing equipment is availablefor prodvdng unleaded gasoline, but an esti-mated 6 to 10 years is necessary for its in-stallation at a capital investment of over $4billion."."

3.2.2 DleselPowered Vehicles

Particulate matter emitted by diesel en-gines consists primarily of carbon and hydro-carbon aerosols resulting from incompletecombustion of the fuel. Aerosols in the ventgases of the two-stroke-cycle diesel engine(from air box drains) and in the exhaust, asa result of crankcase oil going through thecombustion process unburned, produce asmall amount of additional particulate emis-sions.

Federal regulations scheduled for imple-mentation in 1970 will limit smoke from newdiesel engines. The regulations establish amaximum intensity of smoke emission(measured by reduction in Ifght transmis-sion) under conditions of severe engine load-ing at (1) full-throttle acceleration from aprolcAged idle and (2) "iugdown" from max-imum governed speed, also at full throttle.No new information or control devices arebelieved to be needed to reduce the smokeemissions from diesel engines to meet theestablished standards. As vehicle mileage in-creases, proper fuel system adjustment,maintenance at appropriate intervals, theuse of the specified type of fuel, and goodoperating techniques can maintain low levelsof visible emissions, particularly with respectto particulate carbon.

New engines, which will comply with the1970 smoke standards, will be adjusted bythe engine manufacturer to a conservativefuel rate and power output. Increases in fuelrate above the manufacturer's setting will in-crease engine power, but also will raise thelevel of black smoke. Even in a properly ad-justed engine, injector deterioration (suchas nozzle erosion) can effect a substantial in-crease in the emission of black smoke.

FILTERED AIR

CONTROL VALVE

CRANKCASEBLOWBY GASES

0 FILTERED AIRBLOWBY GASES

I oil FILTERED AIR + BLOWBY GASESImp COMBUSTIBLE MIXTURE

now. 3-1. Motor vehicle emission control system.

Investigations have been conducted to eval-uate methods of reducing diesel smoke. Meth-ods consist primarily of exhaust gas dilutionand the use of smoke-suppressing fuel addi-tives. Neither of these methods can be recom-mended for general application at this time.The dilution technique at best, merely re-duces the opacity of the smoke plume with-out reducing the quantity of particles emit-ted. Smoke suppressants have been reportedto be effective in overfueled engii,es in goodmechanical condition. One type of suppres-sant reported to show promise contains bar-ium." Use of the organic barium additivetvuld, however, result in the emission oftexic, water-soluble, barium compounds. Fur-ther study of additives is needed before thistechnology can be broadly adopted.

6

3.3 CONTROL OF PARTICULATE ENIIS-MONS FROM STATIONARY COM-11USTION SOURCES

3.3.1 Introduction

4.3.1.1 GrncrydOf the many techniquesunit to control particulate air pollution fromstationary combustion sources, none hasemerged as an all-inclusive answer to thecontrol problem.

3.3.11 SourcesMore than 29 million sta-tionary combustion sources are currently inoperation in the United States." About 2percent are fired with coal, 61 percent arefired with gas, and 37 percent are fired withliquid fuels. Table 3 -2 shows the consumptionof energy by type of consumer. Coal, gas, andoil are burned in a wide variety of equip-

Table 1-2.ESTIMATED 1966 UNITED STATESENERGY CONSUMPTION BY SELECTED CON.SUMER (10" Btu)"

Consumer

Energy sourceHouse.

holdandcorn.

merdal

IndustrialPowergenera-

lionTotal

Anthr.cite coal. 143 41 66 240Bituminous and

lignite coal.676 2,206 6,841 9,122

Natural gas 6,946 6,674 a 2,692 14,311Petroleum 2,247 2.612 005 6,664Hydroelectric 0 0 2,060 2,060Nuclear 0 0 68 U

Total 8,910 10,433 12,112 31,453

Excludes non-combustion consumption.b Excludes naphtha, keroatte, and liquified petroleum

gases.

ment. The more common types of equipmentare shown in Table 8-3.

3.3.1.3 EmissionsParticulate emissionsfrom stationary combustion sources in theUnited States are estimated at 4.5 milliontons (see Table 3-4). Local patterns of emis-sions will usually differ from the nationalpattern because of differences in fuel andequipment use patterns.

The rate of uncontrolled particulate emis-sions varies widely from unit to unit becauseprocesses, practices, and fuels all affect emis-sion levels. For each fuel, several differentprocesses are used for stationary combustion.Steam, hot water, and warm air furnaces arein common use for domestic heating andmany specialized heaters are used by in-dustry. Burners, combustion chambers, heattransfer characteristics, draft systems, and

Table 3-3.COMMON USES OF VARIOUS FUELBURNING EQUIPMENT

Equipment Common t.*

Coabfired:Rand stoked equipment

Single-retort underfeed stokers

Multiple-retort underfeed otolteraSpreader atokersTraveling grate stokersChain grate stokersVibrating grate stokersPalverited-fuel-fired equipment

(dry bottom or wet bottom)Oil-fired:

High - pressure gun-type burners

Low-pressure air - atomising burners

Rotary cup burnersSteam atomizing burnersHigh-pressure air-atomising burners

Oas-fired:Premixing burners

Notale mixing burners

101

Residential, institutional, and commercial warm-air andboiler applications at capacities up to 6 million Btu perhour input. (Used primarily In coal-producing areas.)Residential. institutional. and commercial warm-air andboiler applications at co; &cities up to 40 million Btu perhour input.Water tube and fire tube boiler applications for institu-tional, commercial, and industrial heating at capacities inrange of 6 million to 200 million Btu Der hone input.

Water tube boiler applications for power generation atcapacities greater than 100 million Btu per hour input.

Residential warm air furnace or boiler applications atcapacitiest up to 3 gallons pet hour distillate oil.

Water tube and Are tube boiler applications for institu.lional, commercial, and industrial process heating withdistillate or residual oil.Water tube and Are tube boiler applications for institu.tional, commercial, and industrial heating and powergeneration with residual oil.

Residential warrair furnace or boiler applications andlow-temperature industrial application/L.Water tube and Are tube boiler applications for institu-tional, tORVIWttild, industrial, and power-generation appli-catioas. (May be combination type to permit fuel oil firingwhen gas supply is interrupted.)

7

Table 3-4.-ESTIMATED AMOUNT AND CONTROL STATUS FOR PARTICULATE EMISSIONS FROMSTATIONARY COMBUSTION SOURCES IN 1966

Fuel and sourceUncontrolled

emissions104 tons

Estimatedcontrol status

in 1966,6percent

Estimated emissionsin 1966

10' tons Percentof total

Anthracite coal:Household and commercial 0.05 Negligible 0.05 1.1

Industrial 0.04 62.0 0.02 0.4Power 0.17 86.5 0.02 0.4

Subtotal 0.26 0.09 1.9Bituminous and lignite coal:

Household and commercial 0.24 Negligible 0.24 5.4Industrial 2.29 62.0 0.87 19.5Power 21.14 86.5 2.85 64.1

Subtotal 23.67 3.96 89.0Petroleum:

Household and commercial 0.08 Negligible 0.80 1.8Industrial 0.17 Negligible 0.17 3.8Power 0.03 Negligible 0.03 0.7

Subtotal 0.28 0.28 6.3Natural gas:

Household and commercial 0.06 Negligible 0.06 1.3Industrial 0.05 Negligible 0.05 1.1

Power 0.02 Negligible 0.02 0.4Subtotal 0.13 0.13 2.8

Grand total 24.34 4.46 100.0

Basis for estimates:1. Emission factors Table 5-1.2. Energy consumption Table 3-2.3. Fuel properties:

Anthracite coal-13,000 Btu/lb., 10 percent ash.Bituminous coal-12,000 Btu/lb., 10 percent ash.Distillate oil-140,000 Btu/gal.Residual oil-150,000 Btu/gal.Natural gas-1000 Btu/ft s.

b Reference 15.Excludes naphtha, kerosene, range oil, and LP gas.

combustion controls of industrial heatingunits may vary widely. The practices of thoseresponsible for selecting, installing, operat-ing, and maintaining stationary combustionsources can also have significant effects onparticulate emissions.

Because the rate of particulate emissionsvaries widely from unit to unit, the amountof particulate emissions that may be expect cdfrom a given source has not been establishedwith accuracy. Data that are useful for esti-mating emissions from groups of units havebeen compiled and are reported as emissionfactors in Section 5.

8

3.3.2 Control TechniquesTechniques that will control particulate

air pollution from stationary combustionsources may be broadly categorized fol-lows:

1. Gas cleaning2. Energy substitution3. Energy conservation4. Good practice5. Source shutdown

Although source relocation and dispersiontechniques will not reduce particulate emis-sions from stationary combustion sources,they may effect some measure of impro,-e-ment in ambient air quality in selected areas.

Table 3-5.OPTIMUM EXPECTED PERFORMANCE OF VARIOUS TYPES OF GAS CLEANING SYSTEMSFOR STATIONARY COMBUSTION SOURCES

Sources

Removal of uncontrolled particulate emissions, percent

Systems in operation Systems underdevelopment

Settlingchambers

Largediametercyclones

Smalldiametercyclones

Electro-static Stackprecip- spraysitators

8-in.pressure Fabric

drop filtersscrubbers

Coal-fired:Spreader, chain grate, and

vibrating stokers.50 60 85 99.6 e 60 99+ 99,6 b

Other stokers 60 65 90 99.6 80 99+ 99.6 hCyclone furnaces 10 15 70 99.6 ' (9 (9 (9Other pulverized coal units 20 30 SO 99.6' (1) 99+ 99.5 b

Oil-fired 5 I. 10 b 30 h 76.0 d (0 (f) (I)

Estimate based on references 17 and 18.b Efficiency estimatednot commonly used.

Estimate based on reference 16.d Estimate based on private reports of field ex-

perience.

3.3.2.1 Gas CleaningGas cleaning is themost common technique used for control ofparticulate emissions from stationary com-bustion sources. As shown in Table 3-4, 20million tons of an estimated total of 24.5million tons of particulate matter from sta-tionary combustion was recovered by gascleaning devices in 1966.

A wide variety of gas cleaning equipmentis available for control of particulate emis-sions from stationary combustion sources.The cost of gas cleaning equipment is usuallygreater for devices of high efficiency; how-ever, the performance of competitively pricedgas cleaning equipment may differ consider-ably. Table 3-5 shows the optimum perform-ance that may be expected from the varioustypes of gas cleaning equipment that mightbe used for removing particulate matter fromflue gases of stationary combustion sources.The efficiencies shown in Table 3-5 are esti-mates based on an analysis of information onparticle size distribution, equipment effi-ciency, reports of experience from the field,and actual source tests.

More detailed information on the specialapplication of these devices to stationarycombustion sources is given in Section 4, GasCleaning Devices.

Settling chambersThe settling chamber

Reference 19.f Insufficient data for estimate.

Estimate based on reference 20.b Estimate based on reference 21.

is a low efficiency, low cost, low pressure dropgas cleaning device. Settling chambers areapplied primarily to natural-draft, stocker-fired, coal-burning units. Collection efficien-cies for this application are estimated to be50 to 60 percent. Only a few oil-fired, gas-fired, and other coal-fired combustion sourcesare equipped with settling chambers.

Large-diameter cyclonesLarge-diametercyclones are more efficient than settlingchambers, but have higher pressure drops.Efficiencies of large-diameter cyclones rangefrom a high of 65 percent for some types ofstoker-fired coal burning units to a low of 15percent for coal-fired cyclone furnaces.

Multiple small-diameter cyclonesMulti-ple small-diameter cyclones are used on me-chanical draft combustion units either as pre-cleaners for electrostatic precipitators or asfinal cleaners. Efficiencies of well designedunits range from 90 percent for some stoker-fired units to 70 percent for coal-fired cyclonefurnaces.

Wet scrubbersSprays are s.ised to a lim-ited extent in the stacks of coal-fired unitsto control particulate emissions during sootblowing. The problems that limit the use ofwet scrubbers include high corrosion rates,high or fluctuating pressure drops, adverseeffects on stack gas dispersion, and waste

9

disposal. Technically, these problems can beovercome, but the feasibility of wet scrubbersystems for stationary combustion sourceparticle control has not yet been demon-strated.

Wet scrubbers have been used experimen-tally for the removal of sulfur oxides fromthe flue gases of coal-fired sources. Thesescrubbers also removed combustion partic-ulate matter with efficiencies of up to 99.5percent.2° A recently completed full-scale sys-tem connected to a pulverized coal-firedpower plant boiler in Missouri is similar tothe experimental installation. Evaluation ofthe economic feasibility and effectiveness ofthis system must be deferred until aftershakedown runs are complete.

Electrostatic precipitatorsElectrostaticprecipitators are the most common gas clean-ing devices used to remove particulates fromthe flue gases of large stationary combustionsources. Such devices are capable of collec-tion efficiencies of at least 99.5 percent, andit is quite possible that even more efficientsystems can be provided if necessary." Elec-trostatic precipitator systems are usually ap-plied to large pulverized coal-fired powerboilers. The cost of these systems has limitedtheir use on smaller combustion sources.

Electrostatic precipitators are highly sen-sitive, and if not properly designed, smallchanges in the properties of the particles andthe gas stream can significantly affect theircollection efficiencies.22 Allowance should bemade for possible changes in fuels, in fuelcomposition, and in gas temperature whenconsideration is given to the nse of electro-static precipitators. It has been establishedthat low-sulfur fuels adversely affect theparticulate collection efficiency of electro-static precipitators designed for high-sulfurfuels."

Fabric FiltersFabric filters are not com-monly applied to stationary combustionsources. Factors which limit the use of thesedevices are uncertainty of performance aridreliability, and availability of other effectivegas cleaning devices.

3.3.2.2 Source RelocationSource relocationwill not eliminate particulate emissions fromstationary combustion sources, but it will

10

eliminate emissions from the original loca-tion of the source. Due consideration shouldbe given, however, to possible air pollutioneffects on other areas.

Source relocation is ordinarily consideredwhen new stationary combustion sources areto be built, particularly when a new plant isto be built to replace one that has created airpollution problems.

33.2.3 Energy SubstitutionThe emissioncharacteristics of fuels used in stationarycombustion processes may differ widely.Therefore, some measure of control may beeffected by substituting among the variousfuels. Control of emissions may also be ef-fected through the substitution of noncom-bustion energy for combustion energy. Thesubstitutions considered in this section arelimited to the more commonly used types ofenergyhydraulic, electric, and nuclearand fossil fuels. Fuels that might be consid-ered as substitutes are LPG gas, coke ovengas, blast furnace gas, pipeline gas fromcoal, kerosene, range oil, coke oven tar, liqui-fied coal, and low-ash coal. Although chemi-cal, solar, and geothermal energies have long-range potential as substitutes that would re-duce particulate emissions, these sources arenot sufficiently developed to warrant currentconsideration.

Information on cost and availability ofenergy substitution is given in Control Tech-niques for Sulfur Oxide Air Pollutants, U.S.Department of Health, Education, and Wel-fare, 1969.

Power generation by stationary combus-tion is a principal source of particulate emis-sions in the United States (see Table 3-4).Energy sources used to generate power arewater, nuclear fuel, gas, oil, and coal asshown in Table. 3-6. Particulate emissionsfrom gas- and oil-fired power plants totalless than 0.1 pound per million Btu input.Coal-fired power plants equipped with gascleaning devices that are 99.5 percent effi-cient compare favorably with oil- and gas-fired plants. Hydroelectric and nuclear powerplants are particulate pollution free.

Substitutions commonly avilable for com-mercial, industrial, and domestic stationarycombustion sources are electric power, coal,

Table 3-6.COMPARISON OF ENERGY SUBSTI-TUTION ALTERNATIVES FOR ELECTRIC POW-ER GENERATION

Energy substitutionalternative

Particulateemissions,lb/10' Btu

input

Hydroelectric 0Nuclear 0Gas (no control) 0.02Oil (no control) 0,07Coal-90 percent fly ash removal 01,7Coal-99.5 percent fly ash removal .. 0.03

a Based on emission factors from Table 5-1 andthe following gross heating values:

Coal-12,000 Btu/lb at 10 percent ash.Oil-150,000 Btu/gal.Gas-1,000 Btu /ft'.

gas, and oil. Fossil fuels may be burned di-rectly at the site where energy is used, or thefuels may be used to produce electrical energyfor transmission to the site of use. Tables3-7 and 3-8 compare the effectiveness of

various substitution alternatives on the basisof particulate emissions per unit of usefulheat.

When comparing substitiution alterna-tives, allowance should be made for differ-ences in heat requirements between seeming-ly identical applications. The differences thatmight be found between fossil fuel and elec-trical heat requirements for space heatingmay be used as an example. Because electri-cally heated buildings are often insulated bet-ter than fossil fuel heating buildings, heat.requirements may not be the same. It is rec-ommended that individual studies be made todetermine these differences by consultingwith representatives of the fossil fuel, elec-trical, and building industries and by usinginformation such as that published by theAmerican Society of Heating, Refrigerating,and Air Conditioning Engineers.25

To make comparisons for a given area, itit recommended that Tables 3-6, 3-7, and 3-8 be revised to reflect local conditions beforesubstitution alternatives are compared.

Table 3-7.COMPARISON OF ENERGY SUBSTITUTION ALTERNATIVES FOR STATIONARYCOMBUSTION SOURCES OF LESS THAN 10 MILLION Btu/hr INPUT

Energy substitution alternativeParticulate emission

equivalent alb/104 Btu useful heat

Electric heat (hydroelectric or nuclear power plant originated) 0Electric heat (gas-fired power plant originated) 0.05Electric heat (oil-fired power plant originated) 0.22Electric heat (coal-fired power plant originated-90 percent fly ash removal) 2.00Electric heat (coal -fired power plant originated-99.5 percent fly ash removal) 0.10Gas -fired furnace on site (no control) 0.03Oil-fired furnace on site (no control) 0.08Coal-fired furnace on site (no control) 1.11

Based on:1. Emission factorsTable 5-1.2. Fuel properties:

Heating value, coal-12,000 Btu/lb at 10 percent ashHeating value, oil-140,000 Btu/galHeating value, gas-1,000 Btu/ft'

3. Estimated thermal efficiency of on-site heating systems.Electric-100 percentCoal, gas, oil-75 percent

4. National average efficiency of power generation "(Btu equivalent of generated power per unit ofheat input).

Coal-33.42 percentGas-31.42 percentOil-30.77 percent

11

Table 3-8.COMPARISON OF ENERGY SUBSTITUTION ALTERNATIVES FOR STATIONARYCOMBUSTION SOURCES OF 10 MILLION TO 100 MILLION Blu/hr INPUT

Energy imbstitution alternativeParticulate emission

equivalentlb/10° Btu useful heat

Electric heat (hydroelectric or nuclear power plant originated) 0Electric heat (gas-fired power plant originated) . . .. 0.05Electric heat (oil-fired power plant originated) 0.22Electric heat (coal -fired power plant originated-90 percent fly ash removal) 2.00Electric heat (coal-fired power plant originated-99.5 percent fly ash removal) 0.10Gas-fired furnace on site (no control) 0.03Distillate oil-fired furnace on site (no control) 0.14Residual oil-fired furnace on site (no control) 0.20Stoker-fired furnace on site (no control) 2.78Stoker-fired furnace on site (90 percent fly ash removal) 0.28Stoker-fired furnace on site (99.6 percent fly ash removal) 0.01

Based on:1. Emission factorsTable 5-1.2. Fuel properties:

Heating value, coal-12,000 Btu/lb at 10 percent ashHeating value, distillate oil-140,000 Btu/galHeating value, residual oil-150.000 Btu/galHeating value, gas-1,000 Btu/ft°

3. Estimated thermal efficiency of on-site heating systems.Electric-100 percentCoal, gas, oil-75 percent

4. National average efficiency of power generation=' (Btu equivalent of generated power per unit ofheat input).

Coal-33.42 percentGas-31.42 percent011.30.77 percent

Energy substitution can be an effectiveand useful technique for control of particu-late emissions from stationary combustionsources. This technique has special value forcontrol of many small sources when the costof effective gas cleaning equipment would beexcessive. When use of this technique is con-sidered, attention should also be given to theeffect of substitution on national security,foreign relations, industry, labor, commerce,conservation, and the public.3.3.2.4 Energy ConservationEnergy con-servation limits particulate emissions fromstationary :ombustion sources by reducingfuel consumption. Energy conservation thatis economical should be encouraged per se.Energy conservation that is not economicalfrom the standpoint of individual processcosts may actually be economical when com-pared with other techniques available for airpollution control.

12

Table 3-9.TRENDS IN EFFICIENCY OF COAL,OIL, AND GAS USE IN UNITED STATES"

Year

Average Btu required to generate1 (net) kw-hr

Coal Oil Gas

1956 11,257 12,828 12,2451963 10,258 11,278 11,0661964 10,241 11,138 10,9621965 10,218 11,097 10,868

Improvement of power generation efficien-cy through use of high-temperature, high-pressure steam electric power generatingprocesses reduces fuel consumption. Table3-9 shows average national trends in efficien-cy improvement for steam electric powergenerating plants. Large, modern powerplants with efficiencies near 8,000 Btu per kw-hr reduce energy consumption substantially

to below the national average of 10,000 to11,000 Btu per kw-hr, and processes nowunder development, such as the magneto-hydrodynamic, electrogasdynamic, and fuelcell, have promise of improving efficiencyeven mere."-"3.3.2.5 Good PracticeEquipment must beproperly applied, installed, operated, andmaintained to minimize emissions of partic-ulate matter. Guidelines for good practice arepublished by the fuel industry, equipmentmanufacturers, engineering associations, andgovernment agencies. Although improperpractices are frequently the cause of visibleparticulate emissions, insufficient informa-tion exists to permit numerical evaluation ofthe effect of good practice on emission levels.Some sources of information on good prac-tice are:

1. Air Pollution Control Association2. American Boiler Manufacturers As-

sociation3. American Gas Association4. American Petroleum Institute5. American Society of Heating, Refrig-

erating, and Air Conditioning En-gineers

6. American Society of Mechanical En-gineers

7. Edison Electrical Institute8. Industrial Gas Cleaning Institute9. The Institute of Boiler and Radiator

Manufacturers10. Mechanical Contractors Association

of America11, National Academy of SciencesNa-

tional Research Council12. National Air Pollution Control Ad-

ministration13. National Coal Association14. National Fire Protection Association15, National Oil Fuel Institute16. National Warm Air Heating and Air

Conditioning Association17. U.S. Bureau of Mines18. Various State and local air pollution

control agenciesProper design and applicationCombus-

tion systems must be propc:rly selected to

meet load requirements. Components, of thesystem should be compatible to avoid exces-sive emission of particulate matter.

Stationary combustion units are designedto operate within a specific range of loadconditions. If such a unit is operated outsidedesign' limits, excessive discharge of particu-late matter is nossible. It is therefore neces-sary that the lo.,d be accurately estimated be-fore stationary combustion systems are se-lected and applied. The total design capacityof the system should be sufficient to carry themaximum load, and consideration should begiven to future increases in load require-ments. The minimum design capacity of oneunit of the combustion system should be suf-ficient to carry the minimum load require-ments of the facility, and the total combus-tion system should be selected to carry, with-in design limits, any load between maximumand minimum.

Consideration must also be given to loadcharacteristics when seleCting a combustionsystem. The combustion system should beable to supply energy at a change in rateconsistent with the demands of the facilitywithout deviation from design limits.

Each component of the combustion system,such as the fuel handling system, the draftsystem, the fuel burning system, the fluesand stacks, the ash handling system, and thecontrols relate(' to these systems, must beproperly selected and integrated to handlethe load and the fuel to be burned.

Proper installationProperly installedequipment will promote clean, efficient oper-ation of stationary combustion sources. Com-prehensive installation instructions andplans are a prerequisite for proper installa-tion. The designer of the entire combustionsystem and the manufacturers of the sys-tem's components are responsible for pro-viding such plans and instructions. Equip-ment should be installed only by qualifiedpersonnel, and all work should be inspectedfor quality.

Proper operation and maintcnonceProper operation and maintenance of sta-tionary combustion equipment will promotethe reduction of particulate air pollution.Stationary combustion units should be openated within their design limits at all times

13

and according to the recommendations ofeither the manufacturer or another authorityon proper operational practices. Combustionunits and system components should be keptin good repair to conform with design speci-fications. Sensitive monitoring systems arehelpful in indicating needed combustion sys-tem repair.

Proper operation also involves the reduc-tion of emissions from fuel- and ash-han-dling systems. Storage pile fires and fuel- andash-handling operations can become signifi-cant sources of particulate air pollution ifgood practice is disregarded.

3.3.2.6 Source ShutdownSource shutdownis a drastic control technique, but it shouldnot be completely disregarded. Source shut-down is useful for control of particulateemissions whep air pollution levels threatenthe public health in emergency episode sit-uations and for control of emissions whenlawful orders to abate are ignored.3.3.2.7 DispersionDispersion is discussedin detail in Section 6 of the report ControlTechniques for Sulfur Oxide Air Pollutants.

3.4 INDUSTRIAL PROCESSES

3.4.1 IntroductionApproximately 6 million tons of dust,

fume, and mist, were discharged from indus-trial processes and industrial fuels fired in1966. This quantity would be considerablygreater if high-efficiency collectors were notused by many industries. However, the totalwould be drastically lower if existing controltechnology were employed to the full ,,t.

Some industries inherently create moreparticulate air pollution than others, and forsuch industries one or two specific operationsdominate the emission picture. In a givenindustry, particulate releases to the atmos-phere are generally proportional to pro-duction rates. Often these discharges canbe reduced dramatically through processchanges or by the use of collection devices.

Table 3-10 lists many of the industriesthat release large quant;ties of particulatematter. As discharged, these particles in-clude dry dusts, combustible oil and tar mists,inorganic acid mists, and combinations of

14

these and other pollutants. The same proc-esses frequently release gaseous pollutants,some of which may be more objectionablethan the particulate matter. Although thisdiscussion is limited to particulate matter,some remedial measures also affect sulfuroxides, odors, or other gaseous contaminants.

The industries which are cited in the fol-lowing pages commonly use several types offired heaters and bailers. Particulate emis-sions associated with this equipment, for themost part, are functions of the fuel burned.Combustion principles developed in Section3.3 generally apply, and the combustion proc-esses are not cited unless specific problemsare associated with them.

3.4.2 Iron and Steel MillsThe major sources of particulate matter in

iron and steel mills are blast furnaces, steel-making furnaces, and sintering plants. Cokeovens, which are operated as adjuncts tosteel mills, are discussed in Section 3.4.9.

3.4.2.1 Sintering PlantsMajor sources ofdust in sintering plants are the combustiongases drawn through the bed and the exhaustgases from sinter grinding, screening, andcooling operations.40 Exhaust temperaturesof the combustion gases range from 160°to 390° F. One 6000-ton-per-day plant oper-ates at 350°F. About 50 percent by weightof the particles discharged from a sinteringmachine are larger than 100 microns." Be-cause dust generated in the sintering oper-ation can be returned to the process, mostplants are equipped with cyclones, which,because of the large particle size, usuallyoperate at over 90 percent efficienzy byweight. However, cyclone exit loadings rangefrom 0.2 to 0.6 grains per cubic foot. High-efficiency baghouses and electrostatic precip-itators, therefore, offer promise of much bet-ter collection. However, few have been ap-plied to sintering machines.

3.4.2.2 Blast FuruncesIron ore, coke, andlimestone are charged into a blast furnace tomake iron. Under normal conditions the un-treated gases from a blast furnace containfrom 7 to 30 grains of dust per standardcubic foot (scf ) of gas.1, Most of the parti-

Tab

le 3

-10.

IND

UST

RIA

L P

RO

CE

SS S

UM

MA

RY

Ann

ual c

apac

ity,

Nw

. ber

Indu

stry

or

proc

ess

1000

tons

of(e

xcep

t as

note

d)pl

ants

Part

icul

ate

emis

sion

s

Nat

ure

Prin

cipa

l sou

rces

Oth

er e

mis

sion

sR

efer

ence

Iron

and

ste

el m

ills_

__

_14

9,00

018

4Ir

on o

xide

dus

t, sm

oke_

_

Gra

y ir

on f

ound

ries

..___

17,3

501,

400

L-o

n ox

ide

dust

, sm

oke,

oil a

nd g

reas

e, m

etal

fum

es.

Non

-fer

rous

sm

elte

rs_

__2,

721

2,50

0 Sm

oke,

met

al f

umes

, oil

and

grea

se.

Petr

oleu

m r

efin

erie

s an

d3,

650

x 10

0 bb

ls.

318

Cat

alys

t dus

t, as

h, s

ul-

asph

alt b

low

ing.

furi

c ac

id m

ist,

liqui

dae

roso

ls.

Port

land

cem

ent

500

x 10

4 bb

ifi.l

.18

0A

lkal

i and

pro

duct

dus

ts

Kra

ft p

ulp

mill

s30

,000

88C

hem

ical

dus

ts, m

ists

_

Asp

halt

batc

h pl

ants

Agg

rega

te d

usts

Aci

d m

anuf

actu

re:

Phos

phor

ic2,

300

66A

cid

mis

t, du

stSu

lfur

ic20

,518

223

Aci

d m

ist

Cok

e m

anuf

actu

ring

_ _

_54

,278

60C

oal a

nd c

oke

dust

s,co

al ta

rs.

Gla

ss f

urna

ces

and

glas

sSu

lfur

ic a

cid

mis

t, ra

wfi

ber

man

ufac

ture

.m

ater

ial d

usts

, alk

alin

eox

ides

, res

in a

eros

ols.

Cof

fee

proc

essi

ngC

haff

, oil

aero

sols

, ash

dehy

drat

ed c

ofie

edu

sts.

Cot

ton

ginn

ing

Car

bon

blac

kSo

ap a

nd d

eter

gent

man

ufac

turi

ng.

Gyp

sum

pro

cess

ing.

.

Coa

l cle

anin

g

1,49

6

Cot

ton

fibe

r, d

ust a

ndsm

oke.

37C

arbo

n bl

ack

Det

erge

nt d

usts

___

___

Prod

uct d

usts

Coa

l dus

ts

Bla

st f

urna

ces,

ste

el m

akin

gfu

rnac

es, s

inte

ring

mac

hine

s.C

upol

as, s

hake

out s

yste

ms,

cor

em

akin

g.

Smel

ting

and

mel

ting

furn

aces

_ _

_

Cat

aljs

t reg

ener

ator

, slu

dge

inci

nera

tion,

air

blo

win

g of

asph

alt.

Kiln

s, c

oole

rs, d

ryer

s, m

ater

ial

hand

ling

syst

ems.

Che

mic

al r

ecla

imin

g fu

rnac

es,

smel

t tan

ks li

me

kiln

s.D

ryer

s, m

ater

ial h

andl

ing

syst

ems_

The

rmal

pro

cess

esph

osph

ate

rock

aci

dula

ting,

gri

ndin

g an

dha

ndlin

g sy

stem

.C

harg

ing

and

disc

harg

ing

oven

cells

, que

nchi

ng, m

ater

ial

hand

ling.

Raw

mat

eria

l han

dlin

g, g

lass

furn

aces

, gla

ss f

iber

for

min

gan

d cu

ring

.R

oast

ers,

spr

ay d

ryer

s, w

aste

heat

boi

lers

, coo

lers

, sto

ners

,co

nvey

ing

equi

pmen

t, ch

aff

burn

ing.

Gin

s, tr

ash

inci

nera

tion

CO

, com

bust

ion

prod

ucts

29, 3

0

Odo

rs, c

ombu

stio

n pr

oduc

ts,

31, 3

2hy

droc

arbo

ns f

rom

con

tam

-in

ated

scr

ap.

SO, c

ombu

stio

n pr

oduc

ts31

, 33

Hyd

roca

rbon

s, S

O.,

H2S

, Mor

s.31

, 34

Com

bust

ion

prod

ucts

31, 3

5

Odo

rs, S

O.

36

Odo

rs, c

ombu

stio

n pr

oduc

ts_

_ _

HF,

SO

., od

ors

37

Phen

ols,

112

S29

Com

bust

ion

prod

ucts

Def

olia

nts

and

inse

ctic

ides

Car

bon

blac

k ge

nera

tors

Spra

y dr

yers

, pro

duct

and

raw

Com

bust

ion

prod

ucts

, odo

rs_

_ _

mat

eria

l han

dlin

g sy

stem

s.C

alci

ners

, dry

ers,

gri

ndin

g an

dC

ombu

stio

n pr

oduc

tsm

ater

ial h

andl

ing

syst

ems.

Was

hed

coal

dry

ers

com

bust

ion

prod

ucts

38 39

Bar

rel

42 g

allo

ns.

Bar

rel =

376

poun

ds.

Iles are larger than 50 microns in diameter.The dust contains about 30 percent iron, 15percent carbon, 10 percent silicon dioxide,and small amounts of aluminum oxide, man-ganese oxide, calcium oxide, and other ma-terials. Blast furnace gas cleaning systemsnormally reduce particulate loading to lessthan 0.01 grain per standard cubic feet toprevent fouling of the stoves where the gasis burned. These systems are composed ofsettling chambers, low efficiency wet scrub-bers, and high efficiency wet scrubbers orelectrostatic precipitators connected in se-ries.

3.4.2.3 Steel FurnacesThe three most im-portant types of steel-making furnaces areopen hearth furnaces, basic oxygen furnaces,and electric furnaces. Relative usage as apercent of total production of each of thesefurnaces in 1958, 1966, and 1967 is shown inTable 341.

Table 3-11.STEEL PRODUCTION, PERCENTAGEBY PROCESS"

Furnace typePercent of total

1958 1966 1967

Open hearth 90.7 72.1 55.6Bask oxygen 1.6 17.4 32.6Electric 7.8 10.5 11.8

Average emission rate from a hot-metalopen-hearth furnace is about 0.4 grain perscf for a conventional furnace and 1.0 foran oxygen-lanced furnace."-41 Up to 90 per-cent of the particles are iron oxide, predomi-nantly FE,Os. A composite of particles col-lected throughout a heat show that about50 percent were less than 5 microns in size.Control of iron oxide requires high-efficiencycollection equipment such as venturi scrub-bers and electrostatic precipitators. Becauseof the cost involved and the growing obso-lescence of open hearth furnaces, industryhas been reluctant to invest money in therequired control equipment." Often thesefurnaces have been replaced by controlledbasic oxygen furnaces and electric furnaces.

More emissions are created by the basicoxygen furnace than by the open-hearth fur-

16

nace. The principal portion of the increasein emissions is caused from furnace oxygenblowing. Emissions of about 5 grains perscf are reported as typical." Particle sizeis small; 85 percent are smaller than onemicron in diameter." All basic oxygen fur-naces in the United States are equipped withhigh-efficiency electrostatic precipitators orventuri scrubbers.

Electric furnaces are usually used for al-loy production, and because of their flexi-bility, are becoming popular for most metalmelting operations. Emissions from electricfurnaces often reach particulate matter con-centrations of grains per scf. Only 40 to50 percent of ..le dust is iron oxide, anamount considerably smaller than that emit-ted by other furnaces. The particles are diffi-cult to collect because of a strong tendency toadhere to fabric surfaces, a high angle ofrepose, and a high electrical resistivity, andbecause they are difficult to wet. Approxi-mately 70 percent by weight of the particlesare smaller than five microns and 95 per-cent by number are smalle than 0.5 micronin diameter." Nevertheless, except for diffi-culties inherent in the charging operation,over 95 percent effective collection can beachieved with appropriate hooding and high-efficiency collection equipment. Baghousesare especially suited for such collection.

3.4.3 Gray Iron FoundriesMelting cupolas are the principle sources

of particulate matter at iron foundries. Cast-ing shake-out sys;ems, sand handling sys-tems, grinding and deburring operations,and coke-baking ovens are other sources.

Cupola exhaust gases are hot and volumi-nous, and contain significant portions of com-bustible matter and inorganic ash. The mosteffective control system incorporates anafterburner to eliminate combustibles anda fabric filter to collect the inorganic dustand fume. Coolers must be used ahead ofthe baghouse to protect fabric filters fromthe heat of the exhaust gas. Most such sys-tems use glass fabrics, but some syntheticcloths have been found to be satisfactory.Even though baghouse control systems pro-vide excellent particle collection, they havenot met with wide acceptance, principally be-

cause of cost." Dry centrifugal collectors andscrubbers with various efficiencies are usedin many instances. High-efficiency scrubbersare reported to provide about the same per-formance as fabric filters, but visible emis-sions are more pronounced.

Casting shake-out and sand cleaning aredusty operations that are normally well con-trolled. For these operations baghouses arecommonly used; medium-efficiency scrubbersand dry centrifugal collectors are also used.

Core ovens create relatively smaller quan-tities of particulate matter, much of whichis in the form of finely divided liquid aero-sols. Emissions from core ovens are similarto those discharged from paint baking andresin curing operations with odors beingmore objectionable than the particulates. Aproperly designed afterburner will eliminatemost of the particulates and malodors.

3.4.4 Petroleum RefiuerlesMajor sources of particulate matter at re-

fineries are catalyst regenerators, airblownasphalt stills, and sludge burners. Lessersources include fired heaters, boilers, andem'rgency flares.

In modern fluidized catalytic crackers, finecatalysts are circulated through the reactorand regenerator vessels. From 100,000 to150,000 cfm of hot, dusty gases are ventedfrom a large regenerator. Dust collectors aswell as carbon monoxide waste heat boilersare often used to control air pollution. It iscommon practice to install a carbon monox-ide boiler to use the fuel value of the cleangas stream exiting from the particulate col-lector.

In typical installations 2-stage or 3-stagecyclones are located in the regenerator ves-sels of FCC units for catalyst recovery andreutilization. In some cases external cyclonesare installed to reduce the particulate con-tent of the flue gases leaving the regener-ators of these units. Catalyst dust losses fromthe regenerator equipped with internal cy-clones and in some cases supplemented byexternal cyclone equipment can range in theorder of 100 to 350 pounds per hour depend-ing on the size, age, and basis of design ofthe unit.

Electrostatic precipitators may also be

used to collect the fine particles from theregenerator exit gases and some refinershave reported catalyst dust losses as low as40-60 pounds per hour although typical cur-rent installations have higher emission rates.The percent efficiency of the precipitators isa function of the inlet dust loading from theregenerator and the desired emission rate tothe atmosphere.

Airblowing of asphalts generates oil andtar mists and malodorous gaseous pollut-ants. It is common practice to scrub the oilsand tars from the hot (300 to 400°F) gasstream. Sea water is sometimes used for thispurpose. In any case, separators are neces-sary to reclaim the oil and prevent contami-nation of effluent water. Afterburners areused to incinerate the uncoadensed gasesand vapors, which can constitute an odornuisance.

As petroleum refineries, the open burningor incineration of sludges can be a majorsource of particulate matter and sulfur di-oxide emissions. These sludges are a mixtureof heavy petroleum residues and such inor-ganic materials as clay, sand, and acids. Be-cause the materials cannot be separatedreadily, sludge is usually atomized in muchthe same way as heavy fuel oil. The organicfraction can be burned effectively in such anincinerator, but any inorganic matter is en-trained in exhaust gases. High-efficiency pre-cipitators, baghouses, and high-energy scrub-bers are among the stack cleaning devicesthat are available to collect the fine dusts;the final choice of control unit would be basedupon the nature of the sludge. Sulfur di-oxide collection would not be effected. How-ever, if there is an accessible sulfuric acidplant, sludge may be conditioned and usedas part of the acid plant's feed material.Very low grade sludges may be dumped atsea. It must be emphasized that incinerationalone is not the solution for the disposal ofall forms of refinery waste sludges. Solventextraction is another method for recoveringthe organic fraction and the separated"clean" solids are acceptable to normal land-fill sites.

3.4.5 Portland CementBoth mining of raw materials and man-

17

ufacture of cement create dust. Dust is gen-erated at the blasthole drilling operation atthe quarry, during blasting at the rockface, and during loading of trucks. Atprimary and secondary crushing plants, inthe grinding mills, at blending and transferpoints, and in the final bagfilling and bulktruck or railroad car loading operations,where the particulate-laden air is at ambi-ent temperatures, bag filters are usuallythe best means of control..'

Rotary dryers used in dry process cementplants may be a major source of dust gen-eration and require collecting systems de-signed for higher temperatures. Dust con-centrations of 5 to 10 grains per scf enter-ing the collector are normal. Baghouses orcombinations of multiple cyclones and bag-houses are frequently used. Newer dryprocess cement plants incorporate the dry-ing operation into the raw grinding circuit.In such a "dry-in-the-mill" combinationel-.-ving and grinding circuit dusts are nor-m fly vented to a baghouse.

The largest sources of emissions at ce-ment plants are direct-fired kilns for burn-ing Portland cement clinker. Exit gas par-ticulate loadings are usually 5 to 10 grainsper scf for wet kilns and 10 to 20 grainsper scf for dry-process kilns. Exhaustgases from wet-process kilns contain con-siderably more moisture than gases fromdry process kilns. The volume of the hot(500° to 600° F) kiln gases may exceed250,000 cubic feet per minute. Over 85 per-cent by weight of gasborne particles aresmaller than 20 microns in diameter. Themost prevalent chemical constituents arecalcium oxide (CaO), about 41 percent; sil-icon dioxide (SiO2), 19 percent; and alu-minum and iron oxides (A12034-Fe20A).9 percent. The balance would be predomi-nately CO2.5°

Electrostatic precipitators are widelyused to control particulate emissions fromkilns. Fabric filters of siliconized glassbags have been installed on both wet anddry process kilns. Each control device hasbeen successful when adequately designedand properly maintained.3.4.6 Kraft Pulp Mills

The major source of par'lulate emis-

18

:ions in kraft pulping is the recovery fur-nace in which spent cooking liquors areburned to remove the organic materials dis-solved from the wood to recover the inor-ganic cooking chemicals. Sodium sulfate isthe major chemical released as particulatematter. Small amounts of sodium carbo-nate, salt, and silica, and traces of lime,iron oxide, alumina, and potash also areemitted. Because 95 to 98 percent of thetotal alkali charged to the digester finds itsway to the spent liquor, it is economicallyimperative that it be recovered.

Electrostatic precipitators of about 90percent efficiency are used to recover par-ticles emitted from recovery furnaces. Newinstallations call for design efficiencies ofabout 97.5 percent, and at least one suchunit has a design efficiency of over 99.9percent.

Other sources of particulate matter aresmelt tanks and lime kilns. Stack dust fromlime kilns can be collected in 85 to 90percent efficient venturi scrubbers. Watersprays of 20 to 30 percent efficiency andmesh demisters of 80 to 90 percent efficien-cy are usually used on smelt tanks.3.4.7 Asphalt Botching Plants

Hot asphalt batching plants are potentialsources of heavy dust. emissions.

Asphalt batching involves the mixing ofhot, dry sand, aggregate, and mineral dustwith hot asphalt. Although conveyors andelevators generate some dust, the majorsource is the direct-fired dryer used to dryand heat aggregates. Exit gases range from250° to 350° at volume rates of 15,000 to60,000 standard cubic feet per minute(scfm). Most dryers employ simple cycloneseparators which collect 70 to 90 percent ofthe dust entrained in the exit gases. Never-theless, the remaining dust in the gas streamusually totals more than 1000 pounds perhour and further dust controls are neededin most areas.

Cc ntrifugal and baffled scrubbers havebeen used with success in many areas tocontrol the fine dust which escapes the pri-mary cyclone. High efficiencies are report-edsome exceed 99.0 percentwith loss-es from most tested plants ranging from20 to 40 pounds per hour. It is common to

vent elevators and major conveyor trans-fer points to the scrubber.51

As high temperature fabrics were de-veloped, fabric filters found greater accept-ance at asphalt batch plants. Such filtershave been used successfully at asphalt batchplants since 1950. Recently, several wereinstalled in Chicago, Illinois, in an effortto obtain better dust control than had beenafforded with scrubbers. They are report-ed to provide excellent collection of fineparticles with little or no visible emissionsfrom the baghouse. Although fabric filtersfrequently are more expensive than scrub-bers, they collect dry "fines" which maybe useable in high-grade asphaltic concretemixes. In addition, they obviate the needfor holding ponds and preclude waterproblems.

3.4.8 Acid Manufacture

Most of the particulate matter attributedto acid manufacture is created in the pro-duction of sulfuric and phosphoric acids.Manufacture of the other two major indus-trial acidsnitric and hydrochloricdoesnot generate large amounts of acid mist.

3.4.8.1 Sulfuric Acid Over 90 percentof the sulfuric acid in the United States ismanufactured by the contact process. 37 Inthe process sulfur or other sulfur bearingmaterials are burned to sulfur dioxide(SO2) and catalytically converted to sul-fur trioxide (SO,). Uncontrolled emissionsrange from 0.05 to 0.23 grain per scf ofexit gas. Concentrations depend to a largedegree on plant design and proper opera-tion of the acid absorber. Most modernplants are equipped with high-efficiencyelectrostatic precipitators or mesh elimi-nators in which 99 percent of the acid mistis recovered. Acid mists are usually con-trolled to a far greater extent than gaseousSO2 releases.

The primary source of emissions in thechamber process is the final Gay Lussactower. Combined sulfuric acid mist andspray in the exit gas ranges from 0.08 to0.46 grain per scf.

3.4.8.2 Phosphoric Acid Two processes

are used to manufacture phosphoric acid.High purity acid for the food and deter-gent industries is produced by burning ele-mental phosphorous. The process is sim-ilar to the contact sulfuric acid process.The oxidation product, phosphorous pen-toxide (P.O,;), is hydrated and absorbedin phosphoric acid. Mist is collected fromexhaust gases with electrostatic precipita-tors or high pressure drop mesh entrain-ment separators. Acid mists escaping col-lection are extremely hygroscopic so thatvisible emissions are pronounced unlesshigh collection efficiencies are achieved.High-purity phosphorous for this processis manufactured in electric furnaces, whichcreate gaseous fluorine compounds and solidparticulates.

The wet process is used to produce lesspure phosphoric acid for the fertilizer in-dustry. During the manufacturing process,sulfuric acid is reacted with phosphate rock.Except for material handling and grindingoperations few particulates are generated.However, the acidulation reaction liberateslarge quantities of gaseous silicon tetraflu-oride (SiP4), and scrubbers are required.

3.4.9 Coke ManufactureMetallurgical coke is the solid material

remaining after distillation of certain coals.About 90 percent of the United Statescoke output is used for production of blastfurnace iron.

Conventional coking is done in long rowsof slot-type coke ovens into which coal ischarged through holes in the top of the ovens.Coke oven gas or other suitable fuel is burnedin the flues surrounding the ovens, to furnishheat for coking. Flue temperature is about2600° F and the coking period averages17 to 18 hours. At the end of the cokingperiod, incandescent coke is pushed out ofthe furnace into quenching cars and car-ried to a quenching station, where it iscooled with water sprays.

The beehive oven is a simpler type ofcoking ovt .1. Distillation products fromthis oven are not recovered. Its use hasdiminished with the development of the by-product oven. The process persists becauseof an economic advantage during peak pro-

19

duction periods. Capital investment low-er and inoperative periods can be tolerated.About 1.5 percent of the total coal coked in1967 was produced in these ovens. A verylarge part, i.e., 25 to 30 percent of the coalcharged to these ovens is emitted to theatmosphere as gases and particulate matter.Ducting these emissions to an afterburnerappears to be a feasible method of control.

Coal and coke dust emissions result fromcoal car unloading, coal storage, crushingand screening, the coking process (wherethe largest releases of particulate dust oc-cur during larry car coal charging of the by-pioduct oven and pushing of the productcoke to quench cars), quenching, and finaldumping from the quench car.

Slot type coke ovens currently being de-signed include the following features thatspeed operations and minimize leaks:

1. Better designed and thinner-walledheating flues to improve heat trans-fer and minimize cool spots and un-dercoking. This results in a clean-er pushing operation.

2. Improved refractories, with lessspalling and cracking. These re-fractory defects cause warping ofmetal furnace parts, gas leaks intoflue systems and chimneys, andvoids which fill with undercokedcoal and cause smoke during pushing.

3. Gas-tight, self-sealing oven doors,that minimize manual sealing withclay.

4. Mechanical cleaners or self-sealersfor doors and for top-charging holecovers. A few grains of sand on ametal seat can cause appreciableleakage of hot gases.

5. Sealing sleeves for leveling bars.Leveling bars are used to even outthe oven charge to allow free pas-sage of gas over the charge into thegas collector main.

6. Mechanical removal of top coal-charging lids and means to chargeall three holes of an individual ovenrapidly and simultaneously, with gasrecovery mains in operation.

7. Steam jet aspirators in byproductheader ducts.

20

I

8. Anintercell header to no malize thecell pressure through( ut the battery.

9. Charging car volumetric sleeves anddust entrainment chutes.

10. Wooden baffling to separate particu-late matter from quench tower efflu-ent gases.

A breakthrough in coke manufacturingtechnology is needed to improve opera-tions." Improvements have been slow."Installations exist that have employed sup-posedly superior charging and di,chargingequipment, but satisfactory ope, at i-n havenot been achieved. A joint rc, ffort

by several steel companies has been underway for 5 years to develop new coke man-ufacturing technology, but potential com-mercial applications appear to be five yearsaway. 53

Another form of coke, used in blast fur-nace refractories and in the manufacturingof electrodes for large steel and aluminumreduction furnaces, Is calcined petroleumcoke. Petroleum coke is a refinery product,but is seldom calcined by the refinery. Cal-cining occurs in a rotary kiln at 1700' Fremoving absorbed water and heavy oiland forming a marble-size product. Volatil-ized hydrocarbons are usually passed to a2200' F combustion chamber before beingreleased to the atmosphere. Subsequent con-veyance of the dusty product to the storagerequires hooding and enclosed ducting. Thedust is abrasive and causes heavy wear onbucket elevators and other transfer equip-ment. Control of particulate matter can beaccomplished during loading of the coke.One system uses concentric tubing; the in-ner filling tube carries the coke and theouter tube exhausts entrained dust from theenclosed railroad car, truck or ship hold.Baghouses are used to capture dust fromloading as well as dust generated at otherhandling and transfer points.

3.4.10 Primary and Secondary Recovery ofCopper, Lead, Zinc, andAluminum

Primary smelting of lead and sine in-volves converting the sulfide of the ore toan oxide through roasting, and subsequentreduction of the metal oxide to its metallic

state in a separate vessel. Copper, however,requires a preliminary smelting step, duringwhich the naturally occurring complex sul-fide is reduced to the cuprous sulfide, CuS2,by mixing the vharge with limestone. Thecuprous sulfide is then converted to blistercopper in a converter where the sulfur isremoved by oxidation. Sulfur dioxide gasis released from these operations, along withparticulate matter which is largely sublimedoxides, dust, and acid mists. When sulfurdioxide emissions exceed 3 percent of thesefurnace exhaust volumes, a sulfuric acidmanufacturing plant is feasible. Pretreat-ment of the smelter gases going to the addis required to remove particulate matter.If sulfur dioxide recovery is not practiced.fiberglass demisters or precipitators are us-ually used to remove particulate materialfrom smelter exhaust gases. For a more de-tailed discussion of smelting, refer to thereport Control Technique's for Sulfur OxideAir Pollutants.

Most materials fed to secondary recoveryfurnaces are alloys of copper, zinc, tin, orlead in the form of solid scrap and drosses.Gases from the furnaces may contain asfumes oxides of the low boiling metals. Par-ticularly bothersome are submicron leadand zinc fume. Zinc oxide fume particle sizeranges from a high of 0.5 micron to a lowof 0.03 micron 13aghouses are usually usedto control these oxide fumes; where thefumes are corrosive, electrostatic precipi-tators are used. Soiled scrap metal meltingmay evolve grease or oil fumes as smokeduring the heatup phase. Incineration ofthe smoke with a control afterburner is nec-essary if the metal cannot be cleaned beforemelting.

Metallic aluminum is produced by theelectrolytic reduction of alumina (A120,)in a bath of fused cryolite by the Ifall-lIeroult process. Cell operating tempera-tures range from 1700' to 1800: F. Thegases generated in the cells are corrosiveand toxic, and consist of hydrogen fluorideand volatilised fluorides. Some fine partic-ulate matter is entrained in the exit gases.Water scrubbers have long been used forcollection of both the particulate and cor-rosive gates. Some installations have used

baghouses with alumina coated cloth filterbags. a4

Secondary aluminum recovery operationsproduce particulate matter from the fluxesused, from impurities in the scrap, and fromchlorination of the molten aluminum. Oilyor greasy scrap gives off smoke. Whenchlorine gas is used to degas the melt orremove magnesium, hydrogen chloride gasand aluminum chloride fume are evolved.The fume Is diaicult to collect because ofits small particle size and hygroscopic na-ture. Water scrubbers are used to collectthe gaseous contaminants.

3.4.11 Soap and Synthetic DetergentManufacture

Principal sources of particulate matterin the making of soap and synthetic deter-gents are the spray drying of products andthe handling of dry raw materials. The wetchemical processes used to make soaps anddetergents are relatively innocuous fromthe particulate standpoint, although malod-orous gases and vapors are generated insome instances.

Gases from the spray dryers, dischargedat approximately 200' F, contain largeamounts of moisture. In addition, the prod-uct is sticky at these temperatures so thatdry collection in fabric filters or electro-static precipitators is difficult. Multiple cy-clones may be employed as precleaners, butscrubbers are used almost exclusively tocollect fine dust Moderate pressure ven-turi units or baffled scrubbers provide ade-quate control in many instances. Thesescrubbers usually use slurries rather thanmerely water and product is recovered fromthe slurries. Residual file particles, togeth-er with high moisture levels, frequently im-part marked opaqueness to the stack gases.It is sometimes passible to avoid this prob-lem by adding some of the less stable ingre-dients to the product after the spray dryingoperation.

Fabric filters are widely used in soapand detergent plants to control dusts gen-erated from the handling of products andraw materials and from packaging opera-tions.

21

3.4.12 Glass Furnaces and Glass FiberManufacture

Reverberatory furnaces are used to pro-duce nearly all glass products. The furnacesand raw materials generate significantquantities of particulate matter.

Glass furnaces are usually heated withoil or natural gas, which is fired directlyover the melt. Heat is reclaimed in check-erwork regenerators used to preheat com-bustion air. Raw materials are charged atone end of the furnace and molted glass ispulled from the other end. Cutlet (scrapglass), limestone, soda ash, and sand arethe main ingredients fed to the furnacemelter section. Glass temperatures are ashigh as 2700° F in the furnace, but are us-ually near 2200' F at the point of discharge.Particulate matter in exhaust gases is trace-able to two principal sources: (1) Fine rawmaterials that are entrained in combustiongases before they are melted; and (2) Ma-terials from the melt, such as sulfur triox-ide created by sulfate decomposition andother solids picked up by escaping carbondioxide gases. Sulfur trioxide and the oxidesof potassium, sodium, and calcium are themain constituents of particulate emissions.Losses from large furnaces range from lessthan 10 pounds per hour to as high as 100pounds per hour. Most units release lessthan 40 pounds per hour. Particulate re-leases tend to be affected by feeder designsand the makeup of raw materials.

Operators control emissions through fur-nace design, electric heating, and raw ma-terial control rather than with .tack clean-ing devices. Control of emissions with fiber-glass filters is feasible, but the particulatematter is extremely difficult to handle.

In the manufacture of glass fiber, theemissions from the forming processes areconsidered unacceptable both from thestandpoint of odor and visible particles. Al-though suitable control methods are notat hand, it appears that a combination ofprocess changes and stack controls will berequired to render exit gases acceptable inmany communities. These methods are be-ing developed and prospects are good thatsatisfactory techniques will be found. After-burners have been employed with success

22

at curing ovens where volumes are low incomparison to forming lines.

3.4.13 Carbon Black

Because of the extremely fine size (0.01to 0.4 micron) and fluffy nature of carbonblack particles, they are readily emittedfrom improper handling and transferringoperations and during separation of themfrom the process gases. Emissions havebeen particularly heavy from channel blackprocess plants. The furnace black process(oil and gas) accounts for 94 percent of thetotal production and technology is avail-able to control emissions from these plants.

Furnace temperature is kept at about2500° F and the black-laden gases are cooledto 450° and 550° F before entering the dustcollecting equipment. The preferred sys-tem consists of an agglomerator followed bya baghouse.39 Coated fiberglass bags lastabout 12 months. The over-all particulatecollection efficiency of such a system Isabout 99 percent. The combination of cy-clone and electrostatic precipitator is nolonger satisfactory because it collects onlyabout 60 percent of the particulate matter.

3.1.14 Gypsum ProcessingGypsum, the basic ingredient of plaster

and wallboard, is manufactured by grind-ing, drying, and calcining gypsum rock. Atmost plants much of the gypsum is proc-essed into wallboard in highly mechanizedsystems. Grinding, drying, and calciningprocesses are principal sources of dust.Handling, packaging, and wallboard man-ufacture are of secondary potential.

Most grinding operations are controlledwith fabric filters. Fine grinders often areequipped with built-in pneumatic convey-om that allow the product to be collectedin the filter.

Gypsum is dried in direct-fired dryersto remove free moisture before calcining.F,xit gases of about 220' F contain a largeamount of fine dust. Electrostatic precipi-tators, baghouses, or scrubbers are almostalways used to remove this dust from exitPAM

The calcining operation is conducted at400- to 450- F in externally heated kettlesor conveyors. In general, exit gases from

the calcining operation are less voluminousthan those from dryers. Historically, elec-trostatic precipitators have been used tocontrol calciners. Dust collection has notalways been adequate, and baghouses nowfind better acceptance. Most new gypsumplants have been equipped with fabric fil-ters. High-temperature fabrics are requiredand heaters have to be installed to preventmoisture from condensing in duct work.

Baghouses are used extensively in mod-ern gypsum plants to collect dust from vari-ous conveying and processing points. Inmost instances a salable product is re-claimed.

3.4.15 Coffee Proceseing

The processing of green coffee beans andthe production of dehydrated instant cof-fee generate dust and liquid aerosols aswell as odorous gases. The most prominentsources are roasters, spray dryers, wasteheat boilers, and green coffee cleaners.

Roasters are the predominant sources ofoil aerosols and odors but also create sig-nificant amounts of solid particulate mat-ter. Chaff, a flaky membrane from the bean,and other solids are collected in simple cy-clones at temperatures of 400) to 500= F.Remaining aerosols and odorous gases maybe incinerated in afterburners at tempera-tures ranging from 1200) to 1400= F.

Coolers and stoners create additional sol-id particulate matter, but few aerosols ormalodors. Cyclones normally provide ade-quate dust control. With some continuoussystems, the exit of roaster gases throughclose coupled coolers requires the use ofafterburners on the cooler exhaust stream.

Spray dryers not unlike those used inother industries are used to produce instantcoffee. If the dryer is operated properly,very little fine particulate matter is gen-erated and satisfactory dust control can beachieved with dry multiple-cyclone collec-tors. Periodic excursions can be expectedwith resultant discharges of fine dust. Manyplants operate scrubbers or baghouses down-stream of mechankal collectors. Collectedfines are blended with the main productstream. Dust recovered in dry collectors is

of sufficient value to rnake it attractive tomaintain collector efficiencies.

At instant coffee plants, large quantitiesof leached coffee grounds are produced.Many operators burn the spent grounds inwaste heat boilers similar to coal-firedboilers. Particulate emissions are depend-ent on the type of firing and the ash con-tent (usually about 4 percent by weight ofdry grounds). A common design incorpo-rates an underfeed stoker and auxiliary gasburners.

Green coffee cleaning and handling cre-ates dust and chaff which normally can behandled well in simple cyclones.

3.4.16 Colton Ginning

The major sources of particulate matterin cotton ginning are the gin itself andthe subsequent incineration of the trash.Relatively coarse materials are emitted fromthe ginning operation an relatively linematerials escape the associated lint clean-er. Iligh-efilcienc. multiple-cyclones suc-cessfully collect the coarse pt....-tie:es, and therecently developed stainless steel in-line fil-ter is effective on the fine particles.

Disposal of the cotton trash by compost-ing, rather than incineration, is being prac-ticed in some parts of the country. Incin-eration of trash generates a large portionof the particulate matter released from un-controlled ginning plants.

3.S CONSTRUCTION AND DEMOLITION

3.5.1 Introduction

The demolition and construction of build-ings and roads creates particulate air pol-lution with periodic emissions character-istically dependent on the specific opera-tions. The handling of dusty materials,movement of trucks on temporary roads,and breaking of masonry walls are a fewof the more prominent dust generating op-erations. None is continuous and the dustfrom almost all can be reduced if suitableprocedures are used.

Principal demolition, construction, andrelat.d operations that generate particulateair poll'ition are:

1. Demolition of masonry.

23

2. Open burning of wooden structures,trees, shrubbery, and constructionlumber.

3. Movement of vehicles on unpavedroads.

4. Grading of earth.5. Paving of roads and parking lots.6. Handling and batching of Portland

cement, plaster, and similar materi-als at the site.

7. Sandblasting of buildings.8. Spray painting of exposed surfaces.

Essentially all of these processes gen-erate particulates that create local nui-sances. Techniques have been developed tominimize dust releases from most offendingoperations; however, none of these are en-tirely satisfactory. Furthermore, all of thecontrol measures require some expense andattention and offer little, if any, monetaryreturn.

3.5.2 Demolition of Masonry

When a brick, plaster or concrete wall isdemolished, most of the particulate matteris released when the broken wall hits theground or floor. In urban areas, watersprays are used to keep exposed surfacesas wet as possible. Before walls are torndown they are sprayed with water, and asthe debris crashes to the ground more wateris sprayed onto the pile. The procedure atbest is inefficient and as it is ordinarilypracticed may reduce particulate matter byonly 10 to 20 percent. In cold or freezingweather, water spraying systems becomealmost completely inoperable.

One concept of dust collection at demo-lition sites calls for enclosing the four sidesof the building by means of plastic sheetsattached to the scaffolding by removableclips." The top of the building is left openand air is sucked in by a large exhaust faninto bag filters for collection. As yet thisconcept has not been applied. Nevertheless,it offers one of the few possibilitit foradequate collection of demolition dust incongested metropolitan areas.

3.5.3 Open BurningBecause open burning cannot be con-

trolled adequately, the only solution is to

24

stop the practice and remove wood and oth-er combustibles to an incinerator or sani-tary landfill or to handle it in some otheracceptable manner.

3.5.4 Road Dust

Trucks moving across dry, unpaved roadsare a prime dust source at construction proj-ects. Dust can be held to a tolerable levelby blacktoppiiig or at least oiling euch sur-faces. For very temporary roads, frequentspraying with water may be satisfactory.

3.5.5 Grading Roads and Other SurfacesThere are few satisfactory remedies for

dust created by earth-moving equipment. Itis best to conduct such operations whenwinds are light and materials are sufficient-ly moist to minimize entrainment of dust inambient air currents. Sand, rock, gravel,and the roadbed can be sprayed with water.

3.5.6 Handling Dusty Materials

Portland cement, plaster, and similaritems are easily rendered airborne duringhandling and batching. If the materials aremixed at the site, greater possibilities arepresented for the evolution of dust. The bestapproach is to mix such materials in a cen-tral location, hooding all major points andventing the dust to a fabric filter.

3.5.7 Sandblasting

The cleaning of stone and concrete sur-faces by sandblasting creates particles thatare difficult to control by common tech-niques. When access is possible, hooding andductwork can be provided from the point ofsandblasting to a baghouse or similar high-efficiency dust collection device. A morecommon p :actice has been to shroud theoperator and the area being cleaned. Mostof the resultant dust is contained withinthe canvas shroud and drops to the groundbelow. A clean eir supply has to be pipedby hose to the operator. The arrangementis successful when winds are light. Understrong wind velocities much of the particu-late matter remains airborne. Sandblast-ing of buildings has been replaced in manyareas by steam cleaning and acid washing.

3.6 SOLID WASTE DISPOSAL

3.6.1 Introduction

Disposal of solid wastes contributes toair and water pollution and threatens topollute the land (through improper dispos-al methods). In 1967, 190 million tons ofsolid wastes were collected excluding someindustrial and agricultural sources." Ofthis quantity, 86 percent was disposed ofat land disposal sites, 8 percent was burnedin municipal incinerators, and only 6 per-cent was disposed of in what could trulybe called a sanitary landfill." Much of thewaste in disposal sites is ultimately burnedin the open. Emissions from these activi-ties represent the most freouent causeof local air pollution complaints by citi-zens." Particulate emissions from inciner-ation cause soiling, visibility reduction, anda generally unsanitary appearance of theair.

Better engineering end planning are re-quired to cope with the problem of disposing of solid wastes in a manner that willleast affect our environment. One surveyindicates that if present trends continueand long-range plans are not made and implemented, this country will not have thecapability to handle the increased amountof solid wastes generated In the year1975." Planning, perhaps on a regionalbasis, and proper use of existing technology,specifically In the fields of incineration andsanitary landfill operation, are the key tomastering the problem of air pollution fromsolid waste disposal.

3.6.2 Definition of Solid Wat,le

As defined in the So Waste DisposalAct of 1965, "The term 'solid waste' meansgarbage, refuse, and other discarded lidmaterials, including solid-waste materialsresulting from industrial, commercial, andAgricultural operations, and from commu-nity activities, but donA not include solidsor dissolved material in domestic sewage orother significant pollutants in water re-sources. . ." It includes both combustiblesand non-combustibles, such as garbage, rub-

WA, ashes, street refuse, dead animals, andabandoned automobiles. Solid waste isgrouped into the following five categor-ies: 39

1. Residential and commercial solidwaste. Food waste, paper, plastics,metals, cloth, wood, and numerousother materials are included in resi-dential and commercial solid waste.Heating value is approximately 4500Btu per pound. Uncompacted densi-ty is approximately 250 pounds percubic yardcompacted density is ap-proximately 600 pounds per cubicyard.

2. Construction and demolition waste.This category includes building ma-terials such as wood, steel, plaster,brick, and concrete.

3. Institutional solid waste. Wastesfrom hospitals, nursing homes, andother institutions are included in in-stitutional solid waste. Such wastesare similar to residential and com-mercial solid wastes, but may containpathogenic materials.

4. Industrial solid waste. Waste prod-ucts as produced by industry includea variety of com'ouftible and non-combustible materials.

6. Agricultural waste. Agriculturalwastt includes animal droppings andcrop tesidue, but does not Includestands of timber or brush burned asa result of accidental forest fires.Reference articles on agriculturalwaste disposal may be fou,'d in Sec-tion 8, Bibliography, under v e head-ing of Food and ArgiculturalSources.

3.6.3 Amounts of Solid Waste Generated

The amount of solid waste generated inthis country is truly astrmamical. Alto-gether, 190 million tons per year or 5.3pounds per person per day are collected. "A breakdown of this latter figure is shownin Table 3-12. These figures however, areonly for that amount of waste actually col,

25

Table 3-12.AVERAGE SOLID WASTECOLLECTED'

(Pounds per person per day)

Solid wastes Urban Rural National

Household 1.26 0.72 1.14

Commercial 0.46 0.11 0.38Combined . 2.63 2.60 2.63Industrial . 0.65 0.37 0.59Demolition,

construction 0.23 0.02 0.18Street and alley 0.11 0.03 0.09Miscellaneous 0.38 0.08 0.31

TOTALS . . 5.72 3.93 5.32

lected. Other amounts are also generatedbeyond that collected and these amounts arebest described in the following quotationfrom Reference 56.

"It must be recalled that 10 to 15percent of household and commercialwastes are collected or transported bythe individual generating the waste.Approximately 30 to 40 percent of theindustrial wastes are self-collected andtransported. Additionally, local rep:-lationsor lack of thempermit c..ter50 percent of our population to burnsome type of household waste in theirbackyards. About 45 percent of com-mercial and other establishments arealso allowed to practice controlled openburning of some type. Thus, althoughthe amount of waste material that hasto be collected is staggering in itself,the amount of material that is actual-ly generated and could pose potentialcollection problems is even more im-pressive. Conservative estimates indi-cate that 7 pounds of household, com-mercial, and municipal wastes are pres-ently generated per person per day; thistotals over 250 million tons per year. Tothis must be added our estimate of over 3pounds per person per day for indus-trial wastes, amounting to an addition-al 110 million tons per year. Thus, es-timates for 1967 indicate that over 10pounds of household, commercial, andindustrial wastes are being generatedper day in this country for every man,

26

woman, and child, totalling over 360million tons per year."'

"To these figures we must add over550 million tons per year of agriculturalwaste and crop re,zidues, approximately1.5 billion tot:s per year of animalwastes, and ore: 1.1 billion tons of min-eral wastes. Altogether, over 3.5 bil-lion tons of solid wastes are generatedin this nation every year. "

4.6.4.1 Disposal Methods to Minimize AirPollutionMany areas of the country haveadequate land available for sanitary land-fills. A properly operated sanitary landfillin which solid waste is buried daily with-out burning can turn a worthless piece ofproperty into a valuable recreation area.The cost of a landfill operation, in mostcases, is less than incineration, not consid-ering hauling costs in either case:" Ex-panded use of landfills, of conrse, may re-quire an efficient municipal pick-up sys-tem. At present, only about 6 percent ofmunicipal solid waste, not including indus-trial and agricultural waste, is disposed ofin a sanitary landfill."

Some solid wastes such as automobile bod-ies, paper and wood chips have a salvagevalue or reclamation potential. If a mar-ket exists in an area (c1 part of all of thewaste currently being burned, it can be de-veloped and used to reduce or eliminate airpollution. Frequent collection of municipalrefuse and the pickup of leaves in the fallwill deter the citizen from open burning.Disposal methods other than combustion are,in many cases, economical. These methodscan be put to use, however, only with theexecution of adequate planning.

In metropolitan areas in which land is be-coming scarce for landfill operations, com-bustion processes are being used to reducerefuse volume by as much as 90 percent be-fore disposal in a landfill, increasing the lifeexpectancy of the landfill site. s: Incinera-tion is often used to sterilize pathogenic orcontaminated waste and reduce its volumebefore burial. Our expanding society mayhave to resort to more extensive iminera-

tion in many areas as an alternative tolandfill. 63

01 the total amount of municipal solidwaste produced, not counting agriculturalor industrial solid waste, 86 percent is ulti-mately disposed of in open dumps whereopen burning is frequently practiced."Such methods of volume reduction normallydo not meet health and esthetic standardsthat usually are desired by a progressivecommunity, 63 because of the large amountof particulate matter (as much as 16 poundsper ton of solid waste burned) released tothe atmosphere with virtually no possibilityof controlling emissions.1 Open burninghas been banned in at least six States."

Even today many apartment house, com-mercial, and municipal incinerators beingbuilt do not meet requirements of good airpollution control standards. Some incinera-tors can operate with a minimum of air pol-lution; however, these units are costly tooperate and maintain, and If poorly oper-ated will create noticeable air pollution. Thetrend today is toward multiple-chamber in-cinerators of adequate design that areequipped with efficient control devices andfull instrumentation as well as towardscontrolled municipal size units. Municipalunits now proposed in this country are ofthe water-wall type that produce steam asa saleable product and collect more tha,:99 percent of the particulate matter emit-ted from the incinerator itself by means ofelectrostatic precipitators.

3.6.32 Disposal Methods Without Incinera-tionDispml and volume-reduction meth-ods that do not use incineration are mostdesirable from an air pollution standpoint.In many cases they may be more economicaland may prove to be more acceptable to acommunity than methods using incineration.

Sanitary landfill-11w sanitarywhich should not be confused with an opendump, is an acceptable means of solid wastedisposal. si Almost any kind of material canbe disposed of by this method of systemat-ically dumping solid waste on the groundor in trenches, compacting the waste bydriving a bulldozer or other heavy equip-ment over it, and covering the waste at the

end of each day with a layer of compactedearth to prevent rodent and insect infesta-tion and to confine odors. When complete-ly filled, land so used may be made intoparks and recreation areas. A properly op-erated sanitary landfill is operated withoutopen burning. Air pollution emissions arelimited to material entrained in the air byearth-moving equipment. Even these emis-sions, however, can be kept to a minimumby wetting the fill material.

Choice of a site and method of operationof a sanitary landfill is essentially depend-ent on the topography and availability ofland. In addition, other factors such aslength of haul, land drainage, source of cov-er material, and quantity of land needed tohandle future waste generation must lx con-sidered before choosing a final site. Somefactors that must be considered are;

1. Land requirements. About 1 acre-foot of land is required for each 1000persons for one year operation whenthe production of waste is 4.5 poundsper day per capita." In addition,cover material totaling at least 20percent by volume of the compactedwaste is required. Such materialmay be supplied from the site ortransported from nearby areas.Normally, sites are designed for 10-to 20-year service periods.

2. Topography. Depressed areas suchas ravines and abandoned pits wherethe grade must be raised are usuallyconsidered desirable for sanitarylandfill sites. Flat land can he usedby applying progressive excavationor the cut and cover method of op-eration. 44

3. Operation. Proper operation of asanitary landfil! requires continuoususe of heavy cirthmoving equipmentto compact and cover the wage withfill material. It is essential thatwaste be covered by no less than a6-inch layer of material at least oncea day. An intermediate layer of cov-er material (about 1 foot deep) isusually spread over completed sec-tions of the site. An additional 2feet of final cover is required as a

27

minimum for the entire site on com-pletion of the operation.

4. Cost. Costs of site, site preparation,and operation must be computed tojudge the true cost of sanitary land-fill operation. In addition, the finalvalue of the land when reclaimedmust be balanced cgainst the initialcost of the land. Sanitary landfillequipment and operating costs usual-ly range from $0.80 to $1.60 per tonof solid waste placed in the land-fill." (Transportation of waste tothe site is not included in thisfigure.)

CompostingComposting, as applied towaste disposal, is the biological decomposi-tion of the organic component of waste.Stable organic residue is the ultimate prod-uct. The residue is usable as low-grade soilconditirner. The market for compost, how -evcr, has not becn very good, because equiv-alent commercial products are available atless cost.

Composting requires seraration of non-organic material from the waste. To beeconomical, a market for such scrap is nec-essary.

Composting costs are the same or higherthan those of incineration. Consequently,only a few plants are operating in the Unit-ed States today." Actually, however, in thecase of a composting plant operated by amunicipality, there is no more reason to ex-pect such a plant to be profitable than anincinerator, as both perform essentially thesame service for the citizens of the munici-pality: that of getting rid of solid wastes.In areas where commercial fertilizer is notreadily available and the scrap market isgood, composting could be a suitable meth-od for handling organic wastes with littleor no particulate air pollution. However,some compost plants Lave odor problems.

ShrtddingDisposal of bulky waste canbe facilitated by shredding. Auto tires, forinstance, can be shredded and placed in aunitary landfill instead of being burned.Bulky wood waste, such as driftwood andcombustible demolition waste, which hasheretofore been burned openly because ofthe difficulty of incinerating it, can be

28

shredded and incinerated in a conventionalincinerator provided it is mixed with con-ventional refuse so that it does not blindthe grates. It can also be disposed of in alandfill site.

Each year more than six million automo-biles are junked in the United States. Auto-mobile body disposal, therefore, is one ofthe growing solid waste problems. The mostpromising solution to the problem appearsto be to step up the reuse for autobody met-al scrap in the domestic steel and foundryindustry, so that the large portion of theavailable supply now being discarded eachyear can be remelted.

Air pollution arising from disposal ofautomobile bodies results, however, whenthey are burned to remove upholstery,grease, and paint. Such burning is appar-ently required to produce a useable scrapthat is competitive with other available ma-terial. Open burning of automobile bodieshas proven entirely unacceptable from anair pollution standpoint. Large quantitiesof particulate matter are generated by suchburning. Metallic particles containing cad-mium, nickel, and lead may also be releasedby this method of disposal.

Open burning of junk automobiles hasbeen replaced by controlled incineration inenclosures. 7° Emissions from such practiceshave been successfully controlled by after-burners, wet scrubbers, and electrostaticprecipitators. Unfortunately, however, be-cause of the low market price paid for auto-mobile scrap, the cost of purchasing, oper-ating, and maintaining such control equip-ment is prohibitive in many areas. It wouldappear therefore, that these control tech-niques need to be reapplied, perhaps in con-junction with process ch.!nges, to lower op-erating and maintenance costs, and allow thehigher installation costs resulting from moresophisticated designs to be amortized overthe life of the installation. Such designsmight attempt to minimize inlet air flow sothat the control devices could be made assmall and inexpensive as possible." Also,where afterburners are used, heat recoverymight be considered.

A possible solution to the air pollutionproblem is the expanded use of mechanical

devices which can disintegrate and shred awhole car (minus the block, rear axle, andseats), remove contaminants by a series ofmechanical separations, and produce a rel-atively useable scrap with little or no incin-eration.72 Such processes can be used bymost larger cities. Cost of equipment fora unit capable of handling from 200 to 300cars per day is $500,000. Cost for a unitcapable of handling 1200 cars per day rangesfrom $1 million to $3 million."

In many locations, however, the low mark-et price paid for shredded scrap has restrict-ed the area from which shredders can drawjunk auto-bodies. Although it, too, is re-stricted by low scrap prices, the practice offlattening junk autos and delivering themfrom outlying areas to a centralized shred-der results in some cars being processedwithout Kenerating as much air pollutionas if they were burned in the open.

CompactionCompaction, although not adisposal method, has the potential of reduc-ing on-site refuse volume to a point thatlarge storage areas nre not required andtransfer to final disposal at landfills ormunicipal incinerators is easier. Compac-tion devices are now being marketed forinstallation in larger apartment complexes.In some instances, these units have replacedchute-fed incinerators.

Compaction installations are similar tochute-fed incinerator installations. Nor-mally, refuse is charged by tenants througha door located on each floor of the building.Refuse builds up to a predetermined levelin a receiving hopper, usually in the base-ment, then is forced by hydraulic ram intoa storage container or bag. Comnaction ofrefuse in the storage container Is claimedto be accomplished up to 3 to 1. Recent in-vestigat tons indicate, however, that muchhigher compaction ratios may be obtained.

Metal containers with capartities tip totwo cubic yards have been used. It has beenreported that one container is required forevery fifty apartments, with removal twoto five times per week.

Installed cost of a compactor is reportedto be $3500, plus $175 per floor for the met-al chute. hauling cost of the compacted ref.use for a 100-unit apartment building in one

area of the country is $85 per month. In-cineration of the same refuse would cost $50.

Widespread use of compaction units couldplace a heavy burden on pickup and dispos-al facilities of a municipality and couldcause art accumulation of refuse shouldscheduled pick up be prevented. Anotherdisadvantage of such a disposal method isthe high cost of installing such units in old-er buildings.

,I.6.3.3 Disposal Methods With !Heiner°.lionIncineration, as a means of volumereduction, may be justified in areas whereland for sanitary landfill is scarce or haul-ing costs are prohibitive. That well designedand well operated equipment be used to min-imize the discharge of particulate matter tothe atmosphere is of utmost importance inthe use of incinerators.

Emissions of particulate air pollutantsfrom combustion of solid waste, includingopen burning, can range from 3 to 28 poundsper ton of refuse, depending on the degreeof combustion and control of emissions.'Reduction of these emissions to the desiredlevel requires either that the incinerator bedesigned for control of fly ash or that a sep-arate control system be used. Table 3.13

Table 3-IXMANI1IUM DEMONSTRATED COL-LECTION ErrtctENcy OP INCINERATORCONTROL EQUIPMENT "A

Collection delceSettling chamberWetted bafflesCyclohesImpaction scrubbers (with

pressure drop less than teninches of water) .

Electrostatic precipitatorsRag filters

Collectionefficiency,percent

3363

75 to SO

91 to 939999+

summarizes the collection efficiency of vari-ous control devices when applied to incin-erators.

Open burning The results of the Na-tional Solid Wastes Survey show that openburning is widespread. Eighty-six percentof the 190 million tons of solid waste col-lected in 1967 went into land disposal sites,76 percent of which resulted in some formof open burning. " The I3ureau of Solid

Waste Management of the EnvironmentalControl Administration sees even a higherpercentage of the sites as undesirable as in-dicated by the following quotation:

"This country has over 12,000 landdisposal sites being utilized by collec-tion services, control of 94 percent ofwhich is unacceptable and representsdisease potential, threat of pollution,and land blight. By no stretch of theimagination do these sites resemble asanitary landfill. The waste manage-ment field must face the challenge ofstudying and evaluating these sites todetermine their suitability for conver-sion to sanitary landfills. We must de-velop the necessary plans, finances, andaction programs to convert those sitesthat can function as a sanitary landfill.In many instances it will be necessaryto close and abandon many of these sites.Local government then must locate anddevelop new sites for immediate usenow and to provide necessary capaci-ties for the increase of the future."

"To eliminate open dumps, and theair pollution that results from openburning in them, as well as other en-vironmental pollution, may cost as muchas $230 million per year for 6 years."This represents about 6 percent morethan is currently being spent annuallyfor solid waste management, ""

Open Top IncineratorsA refractory-lined rectangular chamber with a full, opentop and forced overflre air has 1;een usedto incinerate a variety of wastes includingliquids, solids with high caloric value,"general trash, and municipal refuse. Thisdesign, because of its relatively low cost,has been applied to waste disposal by bothmunicipalities and industries. Tests of apilot unit conducted by the National AirPollution Control Administration haveshown excessive particulate emissions forhigh-ash materials and for low-ash materi-als under certain operating conditions Lowemissions were realised for a low-ash (0.6percent by weight) material incinerated un-der carefully controlled conditions." Oper-ation of full-scale units on certain high-I3tulow-ash wastes are being conducted without

80

visible emissions of smoke, but no quantita-tive test data are yet available. Before ap-plying this technique, careful considerationshould be given to the ash content and physi-cal characteristics of the waste, and testsshould be conducted on the specific waste.As with all combustion sources, this type ofunit requires control of charging and airflow to prevent the emission of smoke andexcessive fly ash. All installations shouldbe equipped with appropriate instrumenta-tion to ensure operation within allowableair pollution limits. Additional tests arecontemplated to further define significantparameters which can be used to estimateperformance on any waste material.

Conical metal burnersConical metalwaste burners are used in the lumber in-dustry to incinerate wood wastes. This sin-gle-chamber incinerator is not properly de-signed to minimize atmosOeric emissions,and is usually not operated or maintainedproperly. Consequently, large amounts ofparticulate matter are emitted from suchunits. Some areas of the country, in fact,have banned all new construction of theseburners. Conical metal burners are not sat-isfactory for other types of refuse either. 7a

Domestic IncineralorsDomestic incin-erators may include such units as single-chamber backyard units with no auxiliaryfuel to dual chamber incinerators having aprimary burner section followed by an after-burner section.

Many air pollution control agencies havebanned installation and use of backyard in-cinerators. A few air pollution agencieshave in the past prohibited the installationof some or all types of domestic incineratorsbecause of the inability to meet various localstandards pertaining to emissions of partic-ulates, organic compounds, or odors. Suchaction may be due in part to excessive emis-sions caused by negligent operation of suchunits and the fact they can be operated with-out using the gas burners.

Commercial and industrial incineratorsCommercial and industrial incinerators forburning general refuse range in capacityfrom 60 to several thousand pounds of ref-use per tour. These units may be classifiedinto two general designs, single- and mul-

tiple-chamber incinerators. A single-cham-ber unit is so designed that admission, com-bustion, and exhaust to a stack take placein one chamber. The multiple-chamber in-cinerator has separate chambers for admis-sion and combustion of the solid refuse,mixing and further combustion of the flyash and gaseous emissions, e.nd settling andcollecting of the fly ash. industrial wastesother than general refuse require special de-signs based on characteristics of the particu-lar waste.

Single-chamber incinerators have gen-erally proven inadequate to meet most emis-sion regulations. Emissions from such unitshave been reported to be as much as 10pounds of particulate matter per ton of ref-use burned.' Multiple-chamber incinera-tors, however, when designed, operated, andmaintained properly, reduce the volume ofrefuse sufficiently and produce a minimumof particulate emission. Emissions fromsuch units have been reported to be as littleas 3 pounds per ton of refuse burned.'Even well-designed multiple-chamber incin-erators may require a good gas washer tomeet more stringent regulations. The Na-tional Air Pollution Control Administrationhas tentatively found that scrubbers havingat least % inch 11,0 pressure drop and awater rate of 4 gallons per 1,000 scfm arerequired for Federal incinerators to meetemission standards for Federal facilities."

To keep particulate emissions to a min-imum, design standards for any incineratormust include means to satisfy the followingcriteria: "

1. Air and fuel must be in proper pro-portion.

2. Air and fuel must be mixed ade-quately.

3. Temperature must be sufficient forcombustion for both the solid fueland gaseous products.

4. Furnace volume must be largeenough to provide the retention tin,eneeded for complete combustion.

5. Furnace proportions must be suchthat ignition temperatures are main-tained and fly ash entrainment isminimised.

Even an incinerator of proper designmust be operated and maintained properlyto minimize particulate emissions. Wherecharging and operation cannot be closelysupervised, scrubbers and auxiliary burn-ers can minimize emissions. Periodic clean-ing and adjustment of burners, spray noz-zles, fans, and other appurtenant devices arealso necessary to minimize emissions.

Initial incinerator cost depends mainly onthe capacity of the unit and the degree ofair pollution controt desired. Figure 3-2"shows typical costs for incinerators with-out scrubbers, with low-efficiency scrubbers,and with high-efficiency scrubbers. Pre-sumably, these costs data are for the ap-proximate time the information was pre-sented, December 1966. To meet the moststringent emission standards and to mini-mize visible emissions and by ash, most in-cinerators must be equipped with scrubbers.

Design criteria and operating practicespreviously described for general refuse in-cinerators should also apply to units burn-

100 SOO 1000 1300 2000

CAPACITY OF INCINERATOR, IIA

Floss 3-4. Cost of Incinerator at three levelt of con-trol of partkaats emissions.

81

ing pathological waste. Primary factorsthat affect particulate emissions from path-ological incinerators include:

1. Gas burner rates should be suffi-cient to maintain at least 1400° F insecondary chamber.

2. Burner placement should be suchthat all waste in primary chamberis covered by flame from burner.

3. Preheating should be accomplishedwith secondary burners prior tocharging of waste.

Many air pollution control agencies re-view on a routine basis all plans for futureincinerator installations to ensure that theseunits meet emission standards. Details thatare usually checked in such a reviewinclude:

1. Plot plans to see if unit is locatedin a suitable area.

2. Unit capacity to see if it is adequatefor the expected daily waste genera-tion.

3. Gas burner placement and fuel rates.4. Scrubber water flow rate.5. Materials of construction for resist-

ance to heat, stress, and corrosion.6. Air port sizes.

Recognizing the fact that emissions fromincinerators are, to a great extent, a func-tion of operation, some air pollution con-trol agencies conduct training courses andpublish literature to be Lsed by incineratoroperators or their supervisors. Once awareof the factors influencing atmospheric emis-sions, it is possible for operators to con-tribute greatly to the reduction of particu-late emissions by such simple practices asregularly cleaning out the ash pit or preheat-ing the unit prior to operation.

Apartment house incinerators Apart-ment house incinerators are an importantpollutant source in urban areas of the coun-try. Smoke and fly ash from these unitscause many complaints.

Emissions are usually higher than other

82

Z.

incineration systems because of low coming-tion temperatures and improper air regula-tion. Adequate control of this source inmost cases has not been achieved, althoughstricter air pollution regulations are inspir-ing the application of new control measures.

The most common apartment house incin-erator is the flue-fed or single-flue, single-chamber model. In this unit refuse ischarged down the same passage that theproducts of combustion use to leave the unit.Refuse dropped onto the fuel bed duringburning smothers the fire and causes in-complete combustion. Improvements in de-sign have been made to the single-flue, sin-gle-chamber unit. There are now chute fedunits that are multiple-chamber incineratorswith separate passages for the refuse andproducts of combustion. This design pro-vides improved combustion and air regula-tion but emissions would still exceed mostemission standards. Inherent in the designof flue or chute-fed models is the high nat-ural draft in the flues of a tall apartmentbuilding which is a major cause cf high par-ticulate emissions.

Air pollution agencies have approachedthe control of these units in different ways.New York has prohibited the installation ofnew apartment house incinerators and hasissued specific criteria for upgrading exist-ing units. Washington, D. C., and Atlantado not allow flue or chute-fed units to be in-stalled. Detroit and Philadelphia have setemission standards at a level that requiresefficient collection equipment, usually waterscrubbers, on apartment house incinerators.

In upgrading existing units and designingnew units, several techniques are used toovercome the problems of excessive emis-sions from apartment house incinerators.A gate at the base of the charging chuteis used to prevent refuse from entering theincinerator during burning and to preventthe products of combustion from leavingthrough the charging flue. This appr( itch ispreferable to locking the hopper doors be-

cause these locks eventually either fail ontheir own or are broken by occupants of thebuilding. For single-flue units, a bypass orseparate flue must be constructed for theproducts of combustion. Auxiliary burnersare placed in the primary and/or secondarychambers of the incinerator to increaseburning temperature and improve combus-tion. 82

Draft control has been used in New Yorkto reduce entrainment of fuel bed material inthe effluent gas stream. A sensor is placedin the primary chamber to monitor draft.When a preset draft level is exceeded adamper located in the breeching at the in-cinerator outlet is activated and decreasesthe amount of air entering the incinerator.

An important step is the addition of effi-cient gas scrubbers to the incineration sys-tem. Scrubbers designed to increase thevelocity of the gases and contact them withlow-velocity water appear to be preferableto spray nozzle units because plugged noz-zles reduce collection efficiency. A finalimprovement is the establishment of definiteburning periods. Burning cycles depend onthe relative size of the apartment house andincinerator, and are quite variable. Theintent of such cycles is to systematically de-stroy the refuse without overloading the in-cinerator, and to minimize smoldering ref-use by destroying all waste charged duringany one cycle. Employment of the abovetechniques should reduce emissions to a lev-el of 2 to 6 pounds per ton of refuseburned. 83

Municipal incineratorsIn 1966, 254municipal-size incinerators were in opera-tion in the United States. The average ca-pacity of these units is 300 tons per day.Most installations are old (70 percent wereinstalled before 1960) and not designed tominimize air pollution.

"It is estimated that approximately $150million is required to construct new incin-erators for replacement of existing inade-quate incinerators and conical burners. Anadditional $76 million is required for airpollution control equipment to upgrade orreplace existing inadequate incinera-tors." 58

Approximately 8 percent of all municipal

solid waste, not including agricultural andindustrial waste, is burned in municipal in-cinerators.56

Desig, criteria to,. municipal incinera-tors Municipal incinerators may be classi-fied as either batch-zed or continuously fedunits. Continuously fed units are preferablebecause operating parameters, such as com-bustion chamber temperatures that affectparticulate emissions, can be closely con-trolled. Grates must be of proper design toensure complete burnout of material. At thesame time, however, grates should mix ortumble the refuse as gently as possible tominimize entrainment of material in theexhaust gas.

Most municipal incinerators in this coun-try are of the refractory-lined furnace type.Water-wall furnaces are more common inEurope. This type of unit offers the advan-tage of steam generation. As a consequenceof heat recovery in the steam generationprocess, flue gas temperatures are lowerthan those of refractory-lined units. Lowerflue gas temperatures cause smaller flue gasvolumes, which in turn require smaller, lesscostly air pollution control equipment. In ad-dition, water-wall units can be operated withless excess air, which further reduces stackgas volume.

Air pollution control equipmentMostmunicipal incinerators in the United Statesare equipped with some form of fly ashcontrol system. Generally. this system con-sists of a simple baffle-type spray cham-ber. These spray chambers prevent hotcinders and large particles from being emit-ted to the atmosphere, but they do not ef-fectively control finer material.

More efficient collection devices will berequired for municipal incinerators to meetreasonable air pollution ck. `rol codes. Themedium pressure drop (6 inches of water)scrubber and the electrostatic precipitatorare two control devices capable of effectiveparticulate control. No precipitator has yetbeen installed on any American municipalincinerator, but several nave been installedand successfully operated in Europe. Sev.eral devices with collection efficiencies ofover 95 percent are scheduled for new andexisting units." High efficiency scrubbers,

33

in contrast to precipitators, might also con-trol emissions of potentially odorous andtoxic gas.

Cost of municipal incineration arai con-trol devices -- Current :oats of constructingmunicipal incinerators may range from$6,000 to $13,000 per ton of rated 24 hour ca-pacity." Costs in the low end of the rangerepresent incinerators of relatively simpledesign with minimal controls, such as a set-tling chamber. Costs for incinerators ofcomplex design, equipped with sophisticatedcontrols such as electrostatic precipitators,would be near the high end of the range.Between 30 and 40 percent of this cost isusually spent on operating equipment andthe remainder is anent on building and land.Operating costs (not including plant amor-tization) range from $4 to $8 per ton ofrefuse incinerated. 84 Precipitator (95 per-cent efficiency) cost for two 250-ton-per-day incinerators is reported at approximate-ly $430,000. 86

3.6.4 Air Pollution. Potential From SolidDisposal Methods

There are approximately 12,000 land dis-posal sites in this country. 66 Such sitesmay be defined ab locations, either privatelyor publicly owned, on which there is dump-ing of solid wastes by public or private con-tractor3. Only 6 percent of these sites maybe termed saritary landfills, in that theyhave daily cover, no open burning, and nowater pollution problems." On three-quar-ters of the remaining 94 percent of the landdisposal sites, some form of open burningis practiced." This type of ultimate dis-posal accounts for a larg share of the par-ticulate emissions '3stimated to arise fromthe burning of solid wastes.

Some amounts of construction, institu-tional, industrial and agricultural waste arcalso burned. Emissions from field burningto remove weeds or residue, incineration ofwood waste, and burning of car bodies forsalvage can contribute significantly to lo-cal and even regional air pollution problems.In some areas of the country these sourcesmay, in fact, be the greatest cause of par-ticulate air pollution.

34

3.6.5 Public Health Service Programs andAssistance in Solid Waste Dispotal

With passage of the Solid Waste Act of1965, the Federal Government made a com-mitment to support and assist in a coordi-nated national effort co solve 'solid wasteproblems." The Solid Wastes Program ofthe E wironmental Control Administrationpresently supplies technical and financial as-sistance relating to methods for handlingsolid wastes. The National Air PollutionControl Administration also provides tech-nical assistance on air pollution emissionsand control techniques for solid waste dis-posal methods. Public Health Service re-gional office directors should be contacted inregard to specific services available. In ad-dition., where problems of solid waste dis-posal arise in connection with mining indus-tries, the Solid Waste Research Group ofthe Bureau of Mines may also be consulted.

REFERENCES FOR SECTION 31. Duprey, R. L. "Compilation of Air Pollutant

Emission Factors." U.S. Dept. of Health, Educa-tion, and Welfare, Public Health Service, PHS-rub 9£9-AP-42, 1968, 67 pp.

2. "Washington, D.C. Metropolitan Area Air Pol-lution Abatement Activity." U.S. Dept. of Health,Education, and Welfare, Public Health Service,National Center for Air Pollution Control, Cin-cinnati, Ohio, Nov. 1967, 162 pp.

3. "New York-New Jersey Air Pollution AbatementActivity, Phase IIParticulate Matter." U.S.Dept. of lIealth, Education, and Welfare, Na.tional Center for Air Pollution Control, Cincin-nati, Ohio, Dec. 1967, pp. 48-49.

4. "Kansas City, KansasKansas City, MissouriAir Pollution Abatement Activity, Phase IIPreconference Investigations." U.S. Dept. ofHealth, Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati, Ohio,March 1968, 180 pp.

6. Sheehy, J. P., Henderson, J. J., Harding, C. I.,and Davis, A. L. "A Pilot Study of Air Pollutionin Jacksonville, Florida." U.S. Dept. of Health,Education, and Welfare, Div. of Air Pollution,PHS-Pub-P99-AP-3, April 1963, 65 pp.

6. Venezia, R. and Cowling, G. "Interstate Air Pol.lution Study, Phase IIProject Report. 11. AirPollutant Emission Inventory." U.S. Dept. ofHealth, Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati, Ohio, Dec.1966. p. 5.

7. "Air Pollution Data for LOS Angeles County."Los Angeles County Air Pollution Control Digs-Het, Jan. 1967, p. 10.

8. McKee, H. E. and McMahon, W. A., Jr. "Auto-mobile Exhaust ParticulateSource and Varia-tion." Southwest Research Institute, May 19139.Also: J. Air Pollution Control Assoc., 10(6):465-462, Dec 1960.

9. "Precipitators for Vehicle Exhaust Control."Environ. Sol, & Technol., 1(12) :970, Dec. 1967.

10. Lawson, S. 0., Moore, J. F., and Rather, J. B.,"A Look at Lead Economics in Motor Gaso-

line." Preprint. American Petroleum Institute,Div. of Refining, May 1967, p. 36.

11. "The Automobile & Air Pollution: A Programfor Progress, Part IL" U.S. Dept. of Commerce,Washington, D.C., Dec. 1967, 160 pp. (SubpanelReports to the Panel on Electrically PoweredVehicles).

12. Norman, G. R. "New Approach to Diesel SmokeSuppression." Transactions, Society of Automo-tive Engineers, 1967, p. 105.

13. "1966 Oil Heating Sales Analysis." Fuel Oil andOa Heat, Jan. 1967, pp. 29-35.

14. "1966 Minerals Yearbook." U.S. Dept of Interior,Washington, D.C., 1967.

15. Moore, W W. "Reduction in Ambient Air Con-centration of Fly AshPresent and Future."U.S. Dept. of Health, Education, and Welfare,Public Health Service, Washington, D.C., PHS-Pub- 1649, 1967, pp. 170-178.

16. "The Sources of Air Pollution and Their Con-trol," U.S. Dept. of Health, Education, and Wel-fare, National Center for Air Pollution Control,Washington, D.C., PHS-Pub-1548, 1967 15 pp.

17. "Criteria for the Application of Dust Collectorsto Coal-Fired Boilers." Results of an IGCl/ABMA Joint Technical Committee Survey.

18. "Modern Dust Collection for Coal-Fired Indus-trial Heating and Power Plants." In: Fuel En-gineering Handbook, Section F-2, National CoalAssociation, Washington, D.C., Sept. 1961, 14 pp.

19. Stack Sprays to Reduce Dust Emissions DuringSoot Blowing." Bituminous Coal Research Inc.,Pittsburgh, Pa., 1965, 4 pp. (BCR Aid to Indus-try, 600-330).

20. Pollock, W, A., Tomany, J. P., and Frieling, G."Removal of Sulfur Dioxide and Fly Ash fromCoal Burning Power Plant Fue Gases." Ameri-can Society of Mechanical Engineers, New York,Pub. 66-WA/CD-4, 1966, p. 8.

21. Sommer lad, K. E. "Fabric viltraticn'State ofthe Art'." Foster Wheeler Corp., Livingston,N.J., March 1967, 19 pp.

22. Reese, J. T. and Greco, J. "Experience withElectrostatic Fly-Ash Collection EquipmentService Steam Electric Generating Plants." J.Air Pollution Control Assoc., 18(8) :523-528,Aug. 1968.

23. Katz, J. "The Effective Collection of Fly Ask, at'Pulverized Coal-Fired Plants." J. Air PollutionControl Assoc., Vol. 15, pp. 526-528, Nov. 1965(Presented at the 68th Annual Meeting, Air Pol-lution Control Assoc., Toronto, Canada, June1966).

24. "Steam-Electric Plant Factors 1966." NationalCoal Association, Washington, D.C., 1967, pp.81-90.

25. "Handbook of I undamentals--1967." AmericanSociety of Heating, Refrigerating, and Air C9n-ditioning Engineers, New York, 1967.

26. Brogan, T. R. and Dragoumis, P. "The Develop-ment of MHD Power Generators." Preprint.(Presented at the National Coal AssociationTechnical Sales Conference and Bituminous CoalResearch, Inc. Annual Meeting, Pittsburgh, Pa.,SrA. 1966).

27. Gourdine, M. C. "Electrogasdynamics and the.Coal Industry." Preprint. (Presented at the Na-tio'al Coal Association Technical Sales Confer-ewe and Bituminous Coal Research, Inc. AnnualMeeting, Pittsburgh, Pa., Sept. 1966).

28. "Review and Evaluation of Project Fuel Cell."U.S. Dept. of the Interior, &Nicer of Coal Re-search, Washington, D.0

29. Schueneman, J. J., High, M. D., and Bye, W. E."Air Pollution Aspects of the Iron and SteelIndustry." U.S. Dept. of Health, Education, andWelfare, Div. of Air Pollution, Cincinnati, Ohio,PHS-Pub-999-AP-1, 1903, 129 pp.

30, "Directory of Iron and Steel Works of theUnited States and Canada." 31st edition, Ameri-can Iron & Steel Association, New York, 1967,411 pp.

31. Von Bergen, J. M. "Profile of Industry Costa forControl of Particulate Air Pollution." Unpub-lished manuscript, 1967.

32. "A Marketing Guide to the Metal Casting Mar-ket." Pentad Publishing Co., Cleveland, Ohio,1960.

33. "Statistical Abstract of the United States." 85thedition, U.S. Dept, of Commerce, Rureau of theCensus, Washington, D.C., 1964.

34. "Standard Industrial Classification Manual."Bureau of the Budget, Washington, D.C., 1964.

35. Kreichelt, T. E., Kemnitz, D. A., and Cuffe, S. T."Atmosphetic Emissions from the Manufactureof Portland Cement." U.S. Dept. of Health, Ed-ucation, and Welfare, National Center for AirPollution Control, Cincinnati, Ohio, PHS-Pub-999-AP-17, 1D67, 47 pp.

36. Kenline, P. A. and Hales, J. M. "Air Pollutionand the K.aft Pulping Industry. An AnnotatedBibliography." 11.S. Dept. of Health, Education,and Welfare, Div: of Air Pollution, Cincinnati,Ohio, PHS-Pub-999-AP-4, 1963, 122 pp.

37. "Atmospheric Emissions from Sulfuric AcidMane.11:'uring Processes." U.S. Dept. of Health,Eiucation, and Welfare, Div. of Air Pollution,Cincinnati, Ohio, PHS-Pub-999-AP-13, 1965,127 pp.

38. "Control and Disposal of Cotton GinningWastes." U.S. Dept. of Health, Education, andWelfare, National Center for Air PollutionControl, Cincinnati, Ohio, PHS-Pub-999- AP -31,1967, 103 pp.

35

39. Drogin, I. "Carbon Bieck." .1. Air Pollution Con-trol Assoc., Vol. 18, pp. 216-228, April 1268.

40. Brandt, A. D. "Current Status and Future Pros-pectsSteel Industry Air Pollution Control."In: Proceedings of the 3i d National Conferenceon Air Pollution, Washington, D.C., 1966, pp.236-241.

41. itic Gannon, Harold K "The Making, Shaping,and Treating of Steel." U.S. Steel Corporation,8th edition, 1964, p. 404.

42. "Annual Statistical Report." American Iron andSteel Institute, 1967 edition, pp. 66, 68.

43. Schueneman, J. J., High, M. D., and Bye, W. a"Air Pollution Aspects of the Iron and SteelIndustry." U.S. Dept. of Health, Education, andWelfare, Div. of Air Pollution, Cincinnati, Ohio,PHS-Pub-999-AP-1, 1963, p. 45.

44. Brandt, A. D. "Current Status and FutureProspectsSteel Industry Air Pollution Con-trol." In: Proceedings of the 3rd National Con-l'erence on Air Pollution, Washington, D.C., 1966,pp. 236-241.

45. Schueneman, J. J., Nigh, M. D., and Bye, W. E."Mr Pollution Aspects of the Iron and SteelIndustry." U.S. Dept. of Health, Education, andWelfare, Div, of Air Pollution, Cincinnati, Ohio,PHS-Pub-999-AP-1, 1963, p. 67.

46. Schueneman, J. J., High, M. D., and Bye, W. E."Mr Pollution Aspects of the Iron and SteelIndustry." U.S. Dept, of Health, Education, andWelfare, Div, of Air Pollution, Cincinnati, Ohio,PHS-Pub-999-AP-1, 1963, p. 68.

47. Schueneman, J. J., High, M. D.. and Bye, W. E."Air Pollution Aspects of the Iron and SteelIndustry." U.S. Dept. of Health, Education, andWelfare, Div. of Air Pollution, Cincinnati, Ohio,PHS-Pub-999-AP-1, 1963, p. 61.

48. Sterling, M. "Current Status and Future Pros-pectsFoundry Air Pollution Control." In:Proceedings of the 3rd National Conference onAir Pollution, Washington, D.C., Dec. 1966, pp.254-259.

49. Doherty, R. E. "Current Status and FutureProspectsCement Mill Air Pollution Control."In: Proceedings of the 3rd National Conferenceon Mr Pollution, Washington, D.C., 1966, pp.24? -249.

50. Doherty, R. E. "Current Status and FutureProspectsCement Mill Air Pollution Control."In: Proceedings of the 3rd National Conferenceon Air Pollution, Washington, D.C., 1966, pp,242-249.

51. Ingeln, R. M., Shaffer, N. R., and Danielson, J.A. "Control of Asphaltic Concrete Plants in LosAngeles Count "." J. Air Pollution Control AMC.,10(1) :29-33, Feb. 1960.

52. Brandt, A. D. "Current Status and FutureProspectsSteel Industry Air Pollution Con-trol." In: Proceedings of the 3rd National Con-ference on Air Pollution, Washington, D.C., 1966,pp. 236-241.

53. Brandt, A. D. Private communication, June 11,1968,

86

51, "Impregnated Fabrics Collect Fluorid. Fumes."Engineering and Mining, J., Vol. 160, No. 5,May 1959.

65. "New 'York City Officials Considering Cocoon forDemolition Dust Control." Clean Air News,2 (8) :12-13, March 12, 1968.

56. Black, R. J., Muhl oh, A. T., Klee, A. j., Hickman,H. L, Jr., and Vaughn, R. D. "The NationalSolid Wastes Survey, an Interim Report."(Presented at the 1965 Annual Meeting of theInstitute of Solid Wastes of the American PublicWorks Association, Miami Beach, Florida, Oct.24, 1968.)

57. Prindle, Richard A. "Health Aspects of SolidWaste Disposal." In: Proceedings, the SurgeonGeneral's Conference on Solid Waste Manage-ment, Washington, D.C., Public Health Service,PHS-Pub-1729, 1967, pp. 15-20.

58. Copp, W. R. "Municipal Inventory. CombustionEngineering, TechnlcafEconomic Study of SolidWaste Dispostal Needs and Practices." Vol. 1,Nov. 1P67, pp. 1-69.

59. Schueller, H. M. "Q.antities and Characteristicsof Solid Waste." In: Elements of Solid WasteManagement Training Course Manual, PublicHealth Service, Cincinnati, Chlo, March 1968,PP. 1-5.

60. Bremser, L. W., "Solid Waste Disposal Study forthe Washington Metropolitan Area." In: Pro-ceedings, the Surgeon General's Conference onSolid Waste Management, Washington, D.C.,Public Health Service, PHS-Pub-1729, 1967, pp.25-33.

61. Kaiser, E. R., Halitsky, J., Jacobs, M. B., andMcCabe, L. C. "Performance of a Flue Fed In-cinerator" J. Air Pollution Control Assoc., 9(2);85-91, Aug. 1959.

62. Weston, R. F. "Future Altevnatives to Incinera-tion and their Air Pollution Potential." In; Pro-ceedings of the Ord National Conference on AirPollution, Washington, D.C., 1967, pp. 806 -308.

63. Seely, R. J. and Loquercio, P. A. "Solid WasteReport for the City of Chicago" City of ChicagoDept, of Air Pollution Control, Chicago, Ill.,1966.

64. Mayer, M."A Compilation of Air Pollutant Emio-sion Factors for Combustion Processes, GasolineEvaporation and Selected Industrial Processes."U.S. Dept. of Health, Education, and Welfare,Div. of Air Pollution, Cincinnati, Ohio, May1965, 53 pp.

65. Kaiser, Elmer R. "Refuse Reduction Processes."In: Proceedings, the Surgeon General's Confer-ence on Solid Waste Management, Washington,D.C., U.S. Dept. of Health, Education, and Wel-fare, National Center for Occupational andIndustrial Health, 1967, pp. 93-104.

6. Sorg, T. J. and Hickman, H. L. "Sanitary LandfillFacts." U.S. Dept, of Health, Education, andWelfare, Nstianal Center for Occupational endIndustrial Health, Washington, D.C., PHS-Pub-1729, 1968.

67. Kirsh, J, B. "Sanitary Landfill." In Elementsof Solid Waste Management Training CourseManual, Public Health Service, Cincinnati, Ohio,1968, pp. 1-4.

68. Sibel, J. T. "Landfill Operations. Coen stion En-gineering, Technical-Econoir Stud:' of SolidWaste Disposal Needs and Practiced." Vol. 4,1967, pp. 1-17.

69. Goluecke, C. G, and McGaughey, P. H. "FutureAlternatives to Incineration and their Air Pol-lution Potential." In: Proceedings of the 3rdNational Conference on Air Pollution, Washing-ton, D.C., 1967, pp. 296-305.

70. Alpiser, Francis M. "Air Pollution from Dispos-al of Junk Autos." Preprint. (Presented at theAnnual Meeting of the Air Pollution ControlAssociation, St. Paul, Minnesota, June 1968).

71. Lieberman, C. "Recovering Scrap Steel for Melt-ing from Automobile Bodies." U.S. Patent No.3,320,051, May 16, 1967, 3 pp.

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74. Kaiser, Elmer B. "incinerators to Meet New AirPollution Standards." (Presented at Mid-Atlan-tic Seals:, Meeting of the Air Pollution ControlAssociation, New York, April 20, 196'/).

75. O'Conner, C. and Swinehart, G. "Baghouee CuresStack Effluent." Power Eng., Vol, C5, pp. 58-69,May 1961.

78. Monroe, E. S., Jr., "New Developments in Indus-trial Incineration." In: Proceedings of 1966 Na-tional Incinerator Conference, American Societyof Mechanical Engineers, New York, 1966, pp.226-230.

77. Burckle, J. 0., Dorsey, J. A., and Riley, B. T."The Effects of the Operating Variables and Ref-use Type, on the Emissions from a Pilot-SealeTrerch Incinerator." In: Proceedings, of 1968National Incinerator Conference, Americun So-ciety of Mechanical Engineers, New York, MayS-8, 1968, pp. 34-41.

78. Kreichelt, Thomas E. "Air Pollution Aspects ofTepee Burnell Used for Disposal of Municipal

Refuse." U.S. Dept. of Health, Education, andWelfare, Liv. of Air Pollution, PHS-Pub-999 -AP-28, 1966, 39 pp.

79. Sal:deski, J. J., Knudson, J. C., Cote, W. A., andKowalczyk, J. F. "Development of IncinerationGuidelines for Federal Facilities." (Presentedat the Annual Meeting of the Air Pollution Con-trol Association, St. Paul, Minnesota, June 23-27, 1968).

80. Williamson, 1. E., McKnight, R. J., and Chess,R. L. "MultipleChamber Incinerator DesignStandards for Los Angeles County." Les AngelesCounty Air Pollution Control District, LosAngeles, California, Oct. 1960.

81. Voelker, E. M. "Contrd of Air Pollution fromIndustrial and Household 'ncineratoris." In: Pro-ceedings of the 3rd Natio al Conference on AirPollution, Washington, D.C., 1967, pp. 332-338.

82. Feuss, James V. and Flower, Franklin B. "TheDesign of Apartment House IncineratorstheState of Art," (Presented at the Annual Meet-ing of the Air Pollution Control Association,June 23-27, 1968.)

83. Duprey, R. L. "Compilation of Air PollutantEmission Factors." U.S. Dept. of Health, Educa-tion, and Welfare, National Center for Air Pol.lution Control, Durhan, North Carolina, PHS-Pub-999-AP-42, 1968, 67 pp.

84. Bogue, M, DeVon "Municipal Incinerators." U.S.Public Health Service, Office of Solid Wastes,1965.

85. Hickman, H. L. Private Communication, Techni-cal Services, Bureau of Solid Waste Manage-ment, Rockville, Maryland, Nov. 1, 1963

86. Fife, James A. and Boyer, Robert H., Jr. "WhatPrice Incineration Air Pollution Control?" In:Proceedings of 1966 National Incinerator Con-ference, American Society of Mechanical En-gineers, New York, 1966, pp. 89-96.

87. Vaughan, R. D. "Assistance Available underthe Solid Waste Disposal Act." In: Proceedingsof the Surgeon General's Conference on SolidWaste Management, Washington, D.C., U.S.Dept. of Health, Education, and Welfare, Na-tional Center for Urban and Industrial Health,1967, pp. 165-162.

37

1. GAS CLEANING DEVICES

4.1 INTRODUCTION

Gas streams contaminated with particu-late matter may be cleaned before the gasis discharged to the atmosphere. Gas clean-ing devices take advantage of certain physical, chemical, and/or electrical propertiesof the particulate matter and gas stream.Selection of a gas cleaning device will beinfluenced by the efficiency required, natureof the process gas to be cleaned, character-istics of the particulate and gas stream, costof the device's use, availability of space, andpower and water requirements. Other basicconsiderations include maintenance, depend-ability, and waste disposal. It has been es-timated that total expenditures in 1966 ofindustrial air pollution control equipment inthe United States were about $235 million.'Value of shipments of the industrial gascleaning equipment industry in 1967 wasdouble the 1963 figure, and the backlog oforders recently nearly equalled a yen's pro-ductive output. Undoubtedly legislative

pressure and local pollution control regula-tions have supplied the impetus for suchrapid growth in this industry.."Fable 4-1shows an up-to-date list of the types andvalues of control equipment being sold tovarious industries. 2

This chapter discusses the wide array ofcommercially available gas cleaning devicesand summarizes published operating charac-teristics, including efficiencies, and infor-mation that will help determine the gascleaning devices suited for a specific appli-cation. Information presented includes:

1. Introductory material (definitionsand theoretical principles).

2. Equipment description and design(variations, arrangements, and per-formance).

3. Typical applications (including effi-ciency data).

4. Operational factors (power require-ments, pressure drops, temperature

Table 4-1.-MANUFACTURERS' SHIPMENTS OF INDUSTRIAL GAS CLEANING EQUIPMENT BY ENDUSE IN 1967

IThoosands of dollars}

Electro- Gasstatic Fabric Mechane:al Scrubbers Scrubbers incinerators Total

precip- filters collectors particulate gaseous and shipmentsitators adsorbers

Iron and steel 6,783 4,636 2,300 7,423 4,276 (b) 24,817 bUtilities 15,506 2,476 () () (*) 18,481Chemicals 1,207 5,344 3,130 3,709 1,479 1,001 15,870Rock products 2,760 3,602 1,038 1,142 ( (a) 8,966Pulp and paper () 122 802 989 193 () 6,753Mining and metallurgical_ () 1,855 389 825 394 () 6,160Refinery ( ( () () () 282 4,098Ali other a 687 4,959 8,408 3,901 114 2,137 20,206Exports () 1,081 651 72 79 6,744

Toial shipments 36,509 21,730 22,381 19,229 6,770 3,976 110,695

Not published to avoid disclosure.b Gas incinerators and adsorbers purchased by iron and steel companies are included in "all others" category to

avoid disclosure."Rock products" toeludes cement and asbestos plants."All other" includes shipments to distributors where end use cannot be identified.

38

I.-

limitations, corrosion and mainte-nance problems, and waste disposal).

Cost factors for each major type of con-trol device are discussed in Section 6 of thisreport. Capital, installation, and operatingcosts are provided for settling chambers, cy-clones, scrubbers, electrostatic precipitators,fabric filters, and afterburners.

4.1.1 Preliminary Selection of EquipmentThe selection of gas cleaning equipment

is far from an exact science and must bebased on particle and carrier gas charac-teristics, and process, operating, construc-tion, and economic factor',.

Important particle characteristics consistof size distribution, shape, density, andsuch physio-chemical properties as hygro-scopicity, agglomerating tendency, corro-siver.ess, "stickiness", flowability, electricalconductivity, flammability, and toxicity.'

Test methods for determining some of theproperties of fine particulate matter citedabove are outlined in the American Societyof Mechanical Engineers' Power Test CodeNumber 28.

The process factors affecting selection ofa gas cleaner are volumetric flow rate, vari-ability of gas flow, particle concentration,allowable pressure drop, product qualityrequirements, and the required collection ef-ficiency. Required collection efficiency isbased on the value ol the material being col-lected, the nuisance or damage potential ofthe material, the physical location of theexhaust, the geographical location (i.e., theair pollution susceptibility of the area), andpresent and future local codes and ordi-nances.

Ease of maintenance and the need for con-tinuity of operation are operating factorswhich should he considered. Important con-struction factors include available floorspace and headroom and construction mate-rial limitations imposed by the temperature,pressure, and /or corrosiveness of the ex-haust stream. Economic factors consist ofinstallation, operating, and maintenancecosts.

Information on the particle size gradationin the inlet gas stream is very important inthe proper selection of gas cleaning equip-

ment. Particles larger than 50 microns maybe removed in inertial and cyclone separa-tors and simple, low-energy wet scrubbers.Particles smaller than 60 microns requireeither high-efficiency (high-energy) wetscrubbers, fabric filters, or electrostatic pre-cipitators. 4

Wet collectors operate at variable effi-ciencies directly proportional to the ener-gy expended and can handle changing efflu-ent flow rates and characteristics. Disad-vantages of wet scrubbers are (1) scrubbeeliquor may require treatment, (2) powercost is high, and (3) a visible plume maybe emitted. Fabric filters more readily per-mit reuse of the collected material and cancollect combustible and explosive dusts.They do, however, have temperature limita-tions and are sensitive to process conditions.Electrostatic precipitators can operate atrelatively high temperatures, have low pres-sure drop, low power requirements, andfew moving parts. They are, however, sen-sitive to variable dust loadings or flow ratesand, in some cases, require special safetyprecautions.

The performance of various gas cleaningdevices may differ widely depending uponthe particular application. Grade efficiencycurves for selected gas cleaning devices areshown in Figure 4- as an illustration of amethod for describing collection equipmentperformance for one application.5,6 Theperformance of the various gas cleaning de-vices shown could differ significantly forother applications.

As a further aid in the selection of par-ticulate matter collection equipment, theareas of application of the various cleaningdevices are given in Table 4-2., Otherareas of application have been summerizedat the end of each equipment section. Thereader should refer to these sections andto the material referenced therein.

4.2 SETTLING CHAMBERS

4.2.1 IntroductionGravitational settling chambers use the

force of gravity to separate dusts and :Listsfrom gas streams. Such collectors are sim-ple in design and operation, but nave lowcollection efficiency. The principal disad-

39

Table 4-2.USE OF PARTICULATE COLLECTORS BY INDUSTRY'

Industrial classification Process EP MC FE WS Other

Utilities and industrial power plants CoalOilNatural gas_LigniteWood and bsrk.Bagasse_

00

0+

00

000

Fluid coke. + +Pulp and paper Kraft 0 0

Soda 0 0Lime kiln 0Chemical ... _ 0

Dissolver tank vents ... _ 0 +Rock products Cement_ 0 0 0 +

Phosphate 0 0 0 0

Gypsum 0 0 0 0Alumina 0 0 0 4-

Lime_ 0 0 + - - --Bauxite 0 0Magnesium oxide + + ____ ____

Steel Blast furnace 0 0 +On hearth 0 - +Basic oxygen furnace 0Electric furnaceSinteric.g 0 0Coke ovens 0

Ore roasters 0

CupolaPyrites roaster 0 0

100

40

r BAG FILTERHOUSE

A VENTURI SCRUBBER (6-INCH THROAT, 30-INCH WATER GAUGE)ISPRAY TOWER (22FUOT DIAMETER)DRY ELECTROSTATIC PRECIPITATOR (3-SECOND CONTACT TIME)

{MULTIPLECYCLONES (12 -INCH DIAMETER TUBES)

8 SIMPLE CYCLONE (1-FOOT DIAMETER)INERTIAL COLLECTOR

I

20 30 10 SO 60 70 80

PARTICLE SIZE, micronsFIGURE 4-1. Composite grade (fractional) efficiency curves based on rest silica dust,

Table 4 -1. (continued}. USE OF PARTICULATE COLLECTORS BY IliDUSTRI"

Industrial classification Process EP MC FF WS Other

Steel-- Continued

Milling and metalltng13.41

TaconiteHot scarfingZinc roasterZinc smelt,:Copper roasterCopper reverbCopper converter

+000000

0....

0_ _ _ .

0......

+

Lead furnace 0Aluminum 0 0Elemental ykos 0Ilmenite 0 0Titanium dioxide + oMolybdenum +Sulfurir acid 0 0 0Phosphoric add 0 0Nitric acid ---- - - -. 0 0Ore heneficiation -I- + + + +

Miscellaneous Refinery catalyst 0 0Coal drying .... 0Coal mill vents + 0Municipal incinerators + 0 0 --Carbon black -I- -I- +Apartment incinerators. ...... ..... 0Spray drying_ ____ 0 0 +Mae' ;fling operation ..... 0 0 + +liot coating --- - ---- 0 0Precious metal 0 .... 0Feed and flour milling 0 0Lumber mills_ 0Wood working. 0 0

Key:0 Most common

+ ...Not normally usedEP " Eleeirostatic Precipitator

MC.. Mechanical CollectorFF.-, Fabric FilterWS...Wet Scrubber

vantages are low collection efficiency forsmall particles and large space require-ments.

4.2.2 Discussloa of Terms

To assist in understanding the operationof Fettling chambers, the following termsare discussed:

1. Terminal Settling Velocity. A dust par-ticle falling under the influence of gravityattains a constant terminal velocity, whichis dependent on the physical properties ofthe gas through which the particle is fall-ing, as well as the physical properties ofthe particle, including its size and shape. 7Terminal settling velocities in air of spheres

Other.z.Packed towersMist padsSlag filterCentrifugal exhaustersFlame incinerationSettling chamber

of different particle densities were calcu-lated and are presented graphically in Fig-ure 4-2.7

2. Pick-Up Velocity. Gas flow velocitiesin a settling chamber must be kept belowvelocities at which reentrainment or "pick-up" occurs, 8 9 or collection efficiency willbe decreased.

8. Collection Efficiency, Collection effi-ciency is represented by the weight frac-tion of the dust retained in the collector.Theoretical collection efficiency may be rep-resented by the ratio of particle retentiontime to theoretical settling time and cannotexceed unity.

41

102

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to weer et VC.Votes C-wolroylAcr eve

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DrtRi.11114.4t14F1,

0.01IT INo envois !million I oil MI I1111 11111! 11111111111 II 11111 III

It 100 l. ao 100

PAQT'CLE DIAMETER, slims%

Floras 4-1 Terminal relocit'ea of spherical particlesin air. (Adapted from reference 7

4.2.3 Design Conoitlerationo

A gravitational settling chamber consistsessentially of a chamber in which the veloc-ity of the carriEr gas is decreased so thatparticles in the gas settle out by gravity.Velocity of a g7s is reduced by expandingthe ducting into a chamber of suitable di-mensions so that a low gas velocity is ob-tained.

42

The settling chamber may consist of asimple balloon duct (Figure 4-3), an ex-pansion chamber with dust hopper (Figure4.4), or dust settling chamber (Figure4-5). The multiple-tray settling chamber(Figure 4-6) represents one of the first at-tempts to increase collection efficiency byreducing the vertical settling distance(time) by using multiple shelving. Verticaldistance between shelves may be as littleas 1 inch. The gas must be uniformly dis-tributed laterally upon entering the cham-ber; vertical distribution is not critical.Uniform distribution is achieved by the useof gradual transitions, guide vanes, dis-tributor screens, or perforated plates.

FIGSTRE 14. Balloon duct.

Because the settling rate of dust decreaseswith increasing turbulence of the gas, thevelocl:y of the gas stream is usually kept aslow as passible. For practical purposes, thevelocity must not be so great that settledparticles are reentrained, or so low thatequipment size becomes excesshe. Gas ve.locities are normally from 1 to 10 feet persecond.

In practice. gravitational settling veloci-ties used in design must be based on experi-ence or on tests conducted under actual von-ilitions, because terminal settling velocitymay be influenced by such factors as ag-glomee.ttion and electrostatic charge.

4.2.4 Typical Applications

Settling chambers are usually installed aspre-cleaners to remove large particle* andagglomerated particles, which can clogsmall-diameter cyclones and other dustcleaning equipment, 13ecause of space ton-sideralions, dust chambers are usually lim-ited to particles larger tht.n 43 microns(328 mesh).

Dust settling chambers are most frequent-ly used on natural draft exhausts from kilns

11111111,,

1r< iFtrqr.werwirratioer

14 Is

ft&

11/....m.- 0

(Cimtosy of Sven Enetnesoinfa Ceavamy, PAOnorm 4-4. Baffled eNps.usic chamber with dust hopper.

INLETAIR PIPE

and furnaces because of their low oressure drop and simplicity of design.t Otherarea of application are in cotton gin °perations and alfalfa feed mills. II

rtGli2 4-8. Dust settling chamber. rta-ftE 4-8. Multiple-tray dust collector.

43

4.3 DRY CENTRIFUGAL COLLECTORS

4.3.1 IntroductionDry centrifugal collectors are gas clean-

ing devices that utilize the centrifugal forcecreated by a spinning gas stream to sepa-rate particulate matter from the carriergas, Spinning motion is imparted to thecarrier gas by a tangential gas inlet, vanes,or a fan. The dust particles, by virtue oftheir inertia, move outward to the sepa-rator wall, from which they travel to a re-ceiver. Is

Three important forces that act on indi-vidual dust particles during the oeuarationprocess are gravitational, centrifugal, andfrictional drag. The force of gravity (F,),which causes the particulate matter to set-tle, is equal to the product of the particulatemass (Mr.) and acceleration caused by grav-ity (G).

F,=111,XG

The major force causing the separa-tion of particulate matter in a cycloneseparator is the centrifugal (radial) forcecaused by a uniform change in linear ve-locity caused by rotation. The centrifugalforce (F,.) is equal to the product of theparticulate mass (Mr) and centrifugal ac-celeration (Vrt/R).

F,=211,,xVpit/R

Where Vr is the particle velocity and Itis the radius of motion (curvature).

The ratio of centrifugal force to the forceof gravity is often called the separationfactor (5) : Is

S F,'FI=Vp1/110

In practice, S varies from 6 for large-di-ameter, low-resistance cyclones to 2600 forsmall-diameter, high-resistance units. 14

The frictional drag on a dust particle iscaused by the relative motion of the particleand gas, and acts to oppose the centrifugalforce on the particle. The frictional drag(Fa is directly proportional to the productof (Cr), a drag coefficient, the projectedcross-sectional area of the particle (Ar),particle density (p), the square of the par-ticle velocity relative to the gas stream

44

(V,'), and an inverse function of the accel-eration due to gravity G.

(C,) (Ar) (p) ( Yrg) /2G

The gravitational, radial, and frictionalforces combine to deterzmne the path of theparticle and collection efficiency.

4.3.2 Types of Centrifugal Collectors

Centrifugal collectors, commonly calledcyclones, are made in a wide variety of de-signs, which generally fall in the followingcategories:

I. Conventional reverse-flow cyclones.a. Tangential inlet.b. Axial inlet.

2. Straight-through-flow "vclones.3. Impeller collectors.

Figure 4.7 shows a typical cyclone of con-ventional reverse-flow design with a tan-gential inlet. Dust-laden gas enters the tan-gential inlet and flows in a helical vortexpath that reverses at the base of the cycloneto form an inner cone. Dust particles areforced to the wall by centrifugal action anddrop to the bottom of the cyclone. There,dust must be removed without disturbingthe vortex of gas flow in the cyclone. Anydisruption of the gas stream reduces collec-

ZONE OF INLETINTERFERENCE

TOP VIEW

SIDE VIEW

Waft .1VORTEX

GASINLET

OUTERVORTEX

GAS OUTLET

BODY\ / /

OUTERVORTEX

INNERVORTEX

INNERCYLINDER(TUBULARGUARD)

CORE

/ I \--DUST OUTLET

rictitt 4-7. Conventional reverse-flow crekne.

tion efficiency and cause-, particle reentrain-ment in the ga3 stream.

Tangential inlet cyclones are categorizedas either high-ediciency or high-throughputcollectors. The high-efficiency design fea-tures a narrow gas inlet which enhancescollection because of the shorter radial set-tling distance and large cross-sectfbnal areabetween the wall and the dust-laden vortex.These features are typical of many smalldiameter cyclones. The high-throughput cy-clone sacrifices efficiency for voluine flowrate and is typical of larger-diameter cy-clones.

Althoukh most cyclones use a cone to re-verse the gas direction and to deliver thecollected dust to a central point for removal,a simple cylinder can be used. Because thecylinder requires a greater axial distancethan the cone and thereby adds height andweight to the collector, it lo not commonlyused.

DUSTLADEN OAS

Ftctitt 4-8. Axial inlet evict*.

The axial inlet cyclone is shown in Fig-ure 4-8. Like the tangential inlet cyclone,both the efficiency and pressure drop of ax-:al inlet units are affected by the dimensionsof the gas inlet.

In cyclones with straight-through flow(Figure 4-9), particulate matter is collect-ed around the periphery of the base and isbled off to a secondary collector that may be

SWIRL VANES

SIDE VIEW

PURGE

DEFLECTOR RING

nem 4-9. StraigIttthroagb-flow cyclone.(Cearfesy of Me ANteritma Pet. ateim hatitmte)

45

a cyclone or dust settling chamber. Thistype of cyclone is used frequently as a flyash collector and as a precleaner (Aimmer)for other types of dust cleaning equipment.The chief advantages of this design are lowpressure drop and high gas handling ca-pacity.

In the impeller collector (Figure 4-10) ,the particulate-laden gas enters the throatof the impeller and passes through a special-ly shaved fan blade where the Oust is throwninto an annular slot leading to the collec-tion hopper.

The principal advantage of this unit isits compactness, which may be of concernin a plant requiring a large number of col-lectors. The major limitation is a tendencytoward plugging and rotor imbalance fromthe buildup of solids on the rotating impell-er. Temperature limitations also exist be-cause of the use of bearings and seals inthe device.

1.3.3 Dealgi

High-efficiency, dry centrifugal collectorsrequire that the separation factor be high,

and the number of gas revolutions large,and that collected dust be removed to avoidreentrainmcnt. Cyclone dimensional factors,gas characteristics, and dust properties af-fect dust collection. It

Collection efficiency increases with:1. Oust particle size,2. particle density,3. inlet gas velocity,4. cyclone body length,5. number of gas revolutions,6. smoothness of cyclone wall.

Collection efficiency decreases with ia-creased :

1. gas viscosity.2. cyclone diameter,3. gas outlet duct diameter,4. gas inlet area.

Cyclone efficiencies am commonly classi-fied as low, medium, and high, correspond-ing to weight collection efficiency rangesof 60 to 80, 80 to 95, and 95 to 99 percent,respectively. " A riven cyclone design canfall into more than one class, depending uponthe mode of operation and the particle

1-7

Ttctita. 4-10. Dynamic ()clone showing method by which dust is dynamically precipitated and &livered tothe storage hopper.

(Cow, 'try of Amerire* Air Fitter CoRpaity)

46

size being collected. For example, a cyclonenominally considered a high - efficiency cy-clone coal operate in the low collection ef-ficiency vange if it were used on a gasstream containing a significant quantity ofsubmlcron particles.

In addition to the overall collection effi-ciency, based on the weight of entrained par-ticulate entering and leaving the collector,performance is also related to cut size.Generally, cut size is defined as the particlediameter collected with 50 percent effi-ciency on a weight basis.

Particle cut size may be estimated fromthe Rozin, Hammier, and Intelmann " for-mula:

Dr,=\/(9-0i)1(2/rN,V1(pg.)where:

D, =diameter Of particle collected with50 percent efficiency,

ic =gas viscosity,b =width of cyclone inlet,N, =number of effective tuns within the

cyclone,=inlet gas velocity,=density of the particulate matter,

andg 1..-dtnsity of the gas.Well-designed, large-diameter, conven-

tional cyclones may be expected to providehigh collection efficiency fur particles from40 to 60 microns and typically hove cut sizesof 8 microns." High-efficiency cycloneshaving diametera of less than 1 foot operateefficiently on y.articles of 16 to 20 microns insite and have cut sizes of 3 microns. Typi-cal efficiencies for various particle siteranges are shown in Table 4-3.

Collection efficiency of small-diameter cy-clones will be low if much of the suspendedmaterial is smaller than 5 microns. In spe-

V

p

Tattle t-LRELATIONSHIP PETWEEN PARTICLESIZE RANGE AM) C'CLoSE EMCIENCVRANGE"

CoareatioaalParticle tar! range, crew*

Mitt)INS efficiency

Lets thsa 6 . ......5 to V)16 to 60Greater that 10 ..

LowMediumHigh

Hightplone

efficiency

LowMcdiam

amb. 41.1.

cal cases in which the dust shows a highdegree of agglomeration or high dust con-centrations are involved (over 100 grainsper cubic foot), cyclones wil! remove dustparticles smaller than 5 microns in diame-ter. The size of the agglomerates is manytimes larger than the original particles. Ef-ficiencies of as high as 98 percent have beenattained on agglomerated dusts having orig-inal particle sizes of from 0.1 to 2.0microns. 17

Factors that commonly cause a reductionin cyclone collection efficiency include infil-tration of air at the bottom of the cycloneand the buildup of dust en the cyclone walls.A variety of dust removal methods is avail-able (Figure 4-11). The buildup of dustmay be reduced by means of vibrators andflexible rubber cones." Specie.' valves maybe used to discharge dust without admittingair.4.3.3.1 Opel-Ming Pressure DropThe pres-sure drop across a cyclone depends on a num-ber of variables, but usually ranges from 1to 8 inches of water. Efficiency increaseswith increasing inlet velocity," but at a lowerrate than that at which the pressure dropincreases. For a given cyclone and dust com-bination, an oplintnin velocity existr, be-yond which turbulence increases more rap-idly than separation efficiency, and aft-cier.cy decreases.

Pressure drop in a cycione is due to bothfrictional and dynamic energy losses, whichare interdependent. Frictional losses are de-termined by cyclone surface roughness, gasvelocity, and the physical properties of thegas and aerosol. Dynamic energy loss, onthe other har..4, is caused by the energystored in the Ir!.;ii-velocity rotating centrif-ugal gas strew,. .TI.Irt of this energy is lostin the rotating .;as leaving the cyclone.

Internal surface roughness can cause anincrease in frictional pressure drop, and re-uult in a eecrease in overall prem.ure dropby causing a decrease in rotational gas ve-locity (dynamic pressu-: loss) along theouter cirIumference of the cyclone, with aresultant decrease in collection efficiency.

To love. the pressure drop through aGiven collector, either a reduction of the ro-tational velocity (dynamic pressure loss) of

47

REMOVABLECONNECTION

DOWNSPOUTFROMCYCLONE

MANUA.SLIDE GATE

DRUMCLOSED

SIMPLE CLOSED DRUMPERIODIC DUMP


.°4 COUNTERWEIGHT

DUST COVER

DUSTBIN

AUTOMATICFLAPVALVES

AUTOMATIC FLAP VALVES

48


DUST 4-TO

BIN

MOTOR.OPERATEDVALVE

MOTOROPERATEDVALVE.


MECHANICALLYOPERATEDSPHEkiCALSEGMENTVALVESOUT OF PHASE

TO DUST0, BIN

SPHERICAL SEGMENT vALvrtFOR IIIGHPRESSUFIE DleFERENTIAL

DOWNSPOUT,C) FROM

ow CYCLONE

CHOKE DISCHARGE SCREW FEEDER

SPRINGLOADEDCHOICE ONSCREWDISCHARGE

navits 4 -it. Various types of eyriorte dust diseliatire.(Ceurtrap of the Amtrieen Par,4estra fariilute)

the cleah exit gas or reduction of internalrotational enemy (dynamic pressure gain)is used. Prt,ssure recovery from the exit

Ftocax 4,12. Cyclones arranged in parallel.(Cowie oy of Buell EntifillOint Company, Int.)

Ift

Frsitys 4-14. Cyclones arrangtA is parallel(Cowles,/ of Wester* Precipitation birision)

gas may be accomplished by the use of de-flection cones, baffles, inverted cones, vanes,or drums and scrolls, but usually at the ex-pense of reduced collection efficiency. Pres-sure reduction vsiues reported in the litera-ture vary from i0 to 26 percent of the totalpressure drop across the cyclone."'

Pressure reduction may also be accom-plished by the use of inlet vanes which re-duce pressure drop and rotational velocity,and hence collection efficiency. Vanes areused when gas handling capacity is to beincreased and/or when normal collection ef-ficiency Is so high that loss in efficiency isinsignificant.

In the impeller collector, pressure dropand collection efficiency may be increasedby restricting the gas outlet. Pressure cropmay be as low as ih inch of water, and pres.sure gains may ever be leatized with someunits because of the pumping action of themotor-driven impeller.

4.3.3 3 Dust Loading --A cyclone can be de-signed to handle practically any amount ofmaterial that can be moved by gas flow.In genera), cyclone efficiency increases withincreasing dust load. Since these (Wee-teristIcs are not possessed by other typesof collectors with inherently higher efficien.ciAs, cyclones are frequently used as pre-cleaners where dust loadings are too highfor the final collector.

Because cyclone efficiencies decrease withdecreitdng dust load and other types of collectors to.n operate efficiently at lower dustloadings, cyclones are usually used (1) fordust loadings of more than 10 grains percubic foot, (2) for come or easily flocculat-ed dust loadings of less than 10 grains percubic foot, or (3) if such factors as hightemperature and corrosion exert an over-riding influence.

4.3.3.3 Other Design ConsiderationtCyclones may be operated In parallel as shownin Figures 4.12 and 4.13. In both configu-rations, gas distribution becomes criticalan collection efficiency is usually lowerthan the corresponding single-unit efficien-cy, even in well-designed systems.

Series operation is sometimes justifiedit the duet is subjected to fragmentation

49

and deflocculation as a result of bouncingwithin the cyclone, if large particles mustbe removed to prevent clogging, if abrasionis a problem, or if the primary cyclone losesefficiency. In these cases, the primary cy-clone is usually of large-diameter, low-pres-sure-drop design followed by progressivelysmaller-diameter cyclones, each with in-creased efficiency and pressure drop.

Erosion effects, increase exponentiallywith increasing gas velocity. Maximumerosion occurs at An impingement angle offrom 20 to SO degrees, and is approximatelytwice the erosion occurring at 90 degrees. IThe effects of erasion may be minimisedby the use of special alloys, abrasion-resist-ant refractories, thicker walls, rubber lin-ing, and by reducing gas velocity.

4.3.4 Typical Applications

C.,,clones are frequently used in both pri-mary and secondary ga cleaning and opera-tions. They are used in feed and grainmills, cotton gins, fertilizer plants, petrole-um refineries, asphalt mixing plants, met-al!.irgical operations, and chemicals, plas-tics, and metals manufacture. to. tt

Cyclones designed for the collection ofmist are sometimes modified by placing anouter skirt on the gas outlet to prevent liq-uid carryover. Representative performAnceand applicathms of centrifugal .collectors arelisted in Tables 4.4 and 4-8. tt

4.4 WET COLLECTORS AND MISTELIMINATORS

4%4.1 Introduction

We collectors use a liquid, usually wa-ter, in the separation process either to re-move particulate matter directly from thegas stream by contact or to increase collec-tion efficiency by preventing reentrainment.4.4.1.1 Collection TAcoryWet collectors in-crease particle removal eiciency by twomechanisms: (1) fine particles are "condi-tioned" sr, that their effective size is in-creased enabling them to be collected moreeasily and (2) reentrainment of the col-lected particles is minimized by trappingthem in a liquid film and washing themaway. 201. 29

The effective size of the particle may beincreased by promoting condensation or.fine particles, whin act as nuclei when thevapor passes through its dew point. Con-densation can remove only a relatively smallamount of dust because the amount of con-densatfon required to remote high concen-teations is usually greater than can be readi-ly achiesed.

Forced conditioning or trapping i dustparticles on liquid droplets is usually ac-complished by impact using inertial forces.Wetting agents do not significantly increasecollection efficiency, but they do help toprevent reentrainment cf collected dusts

Table 4-4--REPHSSENTATIVE PERIVIISIANCE OP CENTIEFIVAL COLLECTORS'

Cot Itt,Pe

nooses stateiaf Airflow,Pressurenu*, Efticicnq,

111. H2O at percent

al...111.1164ar

Islettoad,gr if ti

InletMU,mediansite,*

Series cyclone_ fluid-catalytketa Aim.

Catalyst 10,000 High 0.14 2100 1/.0

Cyclone_ Abrasive cleaning. Tale 2,800 0.33 23.0 2.2Cielorte Drying Sand and gravel 12,800 1.2 88.0 88.0 8.2Cyclone Grinding Aluminum 2,100 1.2 eo.o 0.4

Planing mill Wood. 3,100 2.4 21.0 0.1Impeller

cellectors.Grinding. Iron scale 11,600 1.7 24.3 ..I1 3.21'

Impellercolletiors.

Rubber dusting Lint situate 3,330 1.0 44.0 0.4 0.1

Outlet mass median sites. 2.! micron&Out/et isms median then 2.1 microns.

.1

that are not easily wetted by water."Solubility of the particle in the droplet isusually not a factor in increasing collectioneffectiveness.

The principal mechanisms by which par-ticulate matter is brought into contact withliquid droplets 19 are:

1. Interception. Interception occurswhen particles are carried by a gasin streamlines around an obstacle atdistances of less than the radius ofthe particle.

2. Gravitational Force. Gravitationalforce causes a particle, as it passesan obstacle, to fall from the stream-line and settle on the surface of theobstacle.

3. Impingement. Impingement occurswhen an object, placed in the pathOf a particle-laden gas stream, causes

11111

the gas to flow around the obstacle.Larger particles, however, tend tocontinue in a straight path becauseof inertia and may impinge on theobstacle and be collected. (The im-pingement target efficiency is rep-resented by the ratio of the cross -sectional area of the liquid dropletsto the area of the gas stream clearedof particles.)

4. Diffusion. Diffusion results frommolecular collisions and, except forsubmicron particles, plays little partin separation of particles from a gasstream.

5. Electrostatic Force Electrostaticforces result when particles and liq-uid droplets become electricallycharged. An electrical charge maybe induced by flame ionisation or

Tabl: 44APPLICATIONS OF CENTRIFUGAL COLLECTORS

Operation or process Air contaminantType of air

cleaningequipment

Collectorfficiency,t percent

Reference

Crusliing, pulverising, mixing, screening:Alfalfa feed mill . Alfalfa dust Cyclone, settling

chamber.85 23

Harley feed mill.Wheat air cleaner

Barley flour dust.Chaff

Cyclone.4. Hone

8385

2523

Drying, bak;ntCatalyst refer este:* (petroleum).. Catalyst dust Cyclone, ESP. 9S 23Detergent ponder spray drier Detergent powder Cyclone 85 23Orange " alp feed Met utp dust. Cyclone 83 23Said drying kiln Silica dust. Cyclone 78 21Sand and r we] drying. Silica dust Inertial collector... 60 26Stone drying kiln. Silica dust Cyclone 86 24

Mhing fluids:Asphalt mixing Sand and gravel dust... Cyclone 60-86 24Bituminous COMM* Sand and atone dint.... Cyclone, et-rubber (4 22

Polhing. bleat, ainding, chipping:Grtklint (0,unlauml. Aluminum dust........ Cyclone 82 26()Hiding (iron) Iron et.e.le and rand. Cyclon iS6 25Grinding (machine shop). Dust. Impeller coPlectot_ . 91 21

Surface radio; rubber dusting fluffy 0 A stearate ..... Impeller collector I8 -88 26Surface treatment-013W:

Abrasive , Tait Cyclone 93 26Abrasive stick trimming and

shaping.Silica, carbide and

alumina dent.2 parallel cyclones 61 21

Casting cleaning with metal shot,sandblasting and tumbling.

Metallic and silica dust.. Impeller collector 17 -91+ 27

Foundry tumbling Dust Impeller eollectot... 99 27Truing 614 shaping abrasive

products.Silicon carbide and

alumina dint.Cycloac 68 21

Wooden:eking, including plastics rob-ber, paper board: mill planing.

Wood dust and chips._ Cyclone 9? 24

51

friction, or by the presence ofcharged matter. Electrostatic forcesmay affect collection efficiency sig-nificantly.

6. Thermal Gradients. Thermal gradi-ents are important to the removal ofmatter from a particle-laden gasstream because particulate matterwill more from a hot erea to a coldarea. it ne motion is caused by tinequa! gas molecular collision energyon the surfaces of the hot and coldsides of the particle, and is directlyproportional to the temperature gra-dient.

4.4.1.2 EfficiencyEfficiencies of wet-scrub-bing devices are compared on the basisof "contacting power" and the "transferunit." " Contacting power is that portionof unfol energy expended in producing con.tact of the particulate matter with thescrubbing 114uid, as well as in producing'urbuience and nu (14 ;n the scrubber de-rice. The contacting power represents thekinetic energy or pressure head loss acrossthe scrubber, kinetic energy or pressurehead drop of the scrubbing liquid, and otherforms of energy dissipnted in the gasstream, such as sonic energy or e..ergy sup-plied by a mechanical rotor.

The transfer unit, which Is expressed asthe numerical value of the rotural logarithmof the reciprocal of the frac don of the dustpassing through the scrubber, is a measure+f the difficulty of separation of the particu-late matter.

Dust collection efficiency Is believed bysome investigators to be directly related tocontacting power and the properties of theaerosol and Zo have little relationship toscrubber design and geometry." Othersbelieve design details hr,e important in theeffort to achieve maximum collection efli-dency for a given pressure drop.

Gas Meaning equipment is usually selectedon the basis of required collection efficiency."There are other factors such as gas temper-ature and humidity awl dust stickiness andabrasiveness that may exert an overridinginfluence on the final choice. In the following

62

discussion principal design features of thevarious groups of wet collectors are reviewedfrom the point of view of get.eral suitabilityunder different operating conditions.

In general, particle size distribution andoperating conditions will determine collec-tion efficiencies, which, in turn, will deter-mine power requirements for a given unit.

IJ.2 Equipment Description and Design

Collection efficiencies, operating pressuredrop, water requirements, and other operat-ing characteristics reported herein were ob-tained from manufacturers' equipment bul-letins and other literature sources.4.4.2.1 Spray Chambe The simplest typeof wet scrubber is a round or rectangularspray chamber into which water is intro-duced by means of spray nozzles. 33

When spray chambers are used to removecoarse particles from hot gases, they per-form the additional functions of gas coolingand humidification. Spray chambers alsoeffect preliminary conditioning of the par-ticulate matter by causing condensation ofmoisture on particle, thus increasing collec-tion efficiency by increasing the size of theparticles.

The principal three configurations in aspray chamber are cocurrent flow, countercurrent flow, and cross flow. al

In cocurrent flow, both the spray dropletsand the gas ct.iitaining particulate matterflow though the spray chamber in the samedirection. The relative velocity of the waterdroplet and gas stream causing effectivecollision and rapture of the particulate mat-ter is at a minimum, as is collodion effi-ciency. Part of the kinetic energy of thespray droplets is expended in inducing gascirculation and motion wiThin the scrubber.

Countercurrent flow occurs when the lig-ilk, and gas flow in opposite directions, asin a spray tower in which the liquid is in-troduced in the top of the tower and fallsagainst the rising gas stream. The relativevelocity of the liquid droplets and particu-late matter in the gas stream is at a max-imum, as is collection efficiency.

In cross flow operation, the liquid is in-troduced' at right angles to tte direction ofgas flow and fells across the gas stream.

The relative velocity of the particulate andliquid droplet and Inc impaction efficiencylie between the cross flow and countercur-rent flow methods of operation.

For a given spray chary bee design, mixedflow usually occurs because of turbulence,liquid droplet inertia, and gravitationalforce. Liquid droplets travel in the direc-tion of the liqdd stream until inertial forcesare overcome by air resistance. Large drop-lets settle under the influence of gravitywhile smaller droplets Mar be swept alongwith the gas stream.

Liquid droplets and particulate mattermay be separated from the gas stream bygravitational settling, impaction on bafileo,filtration through shallow packed beds, orby cyclonic action.

Spray chambers are used in exhaust sys-tems for light dust clean!ng, electroplating

SA FULLJET HOUSES11 REQUIRED ;N TKOISANKSMATERIAL TI")E 20 STAIN.LESS STEEL, PkESSUREDROP 51 TO 61 p.s.i.

NOZZLES TO PITCH10' TOwARDCENTEROF STACK

fume control, and preconditioning d "st fromacid phosphate fertilizers," as well 4.s forproviding a final cleanup of exhaust gasesfrom the recovery furnaces in the kraft pulpmanufacturing process."

Figure 4.14 shows a spray system installed in the base of a stack," When thesystem is properly adjusted and operated,GO to 80 percent of the solids entering thespray zone may be collected during soot-blowing operations. a6 Approximately 1/t

gallon of ilquid per minute per square footof stack cross sectional area is required.

The smokestack soot wet-out surface areamay also be increased by packing the smoke-stack (Figure 4.14). The raves of packingare usually stacked and of large diameter tominimize pressure drop and fouling of thebed. Extra draft fan capacity must be avail-able to make up for the decrease in draft

FULLJET NOZZLEI FULLJET NOZZLES26 REQUIRED IN FOURBANKS MATERIAL T T PE103 KT...MUSS STEELPRESSURE DROP SS TO65

NOTE: NOZZLES 10 PITCH10"tOwARDCENTEROF STACK

PACKED STACK UNPACKED STACK

INLET PIPE

SECTION A S

IFULLAT NOZZLE

SECTION 111P

EKFECTED VARIATION OF LIQUID 1,0A0FER SQUARE FEET A *PROximATELY 10%

rialItt 4 -11. Arrangement of nottles is ttrtAce stack spray system.041 rimy of Xpraisiag Sperm: ('oppeRy)

63

caused by lower flue gas temperature and bypacking. The bed must be cleaned periodi-cally by flooding with water.4.4.2.2 Gravity Spray TowersOne of thesimplest types of wet scrubbers is the grav-ity spray tower. Liquid droplets, producedby either spray nozzles or atomizers, falldownward through a countercurrent risinggas stream containing dust particles. Toavoid spray droplet entrainment and carry-over, the terminal settling velocity of thespray droplets must be greater than the ve-locity of the rising gas stream. In practice,the vertical gas velocity usually ranges from2 to 5 feet per second. For higher velocities,a mist eliminator must be used in the topof the tower.

Collection impingement target efficiencyin a gravity spray tower is influenced by thedifference between the free-falling velocityof these particles and the velocity of the ris-ing gas stream. Droplet collection efficiencyincreases with decreasing droplet size andincreasing relative velocity. In a gravita-tional settling chamber these two conditionsare mutually exclusive. Hence, there is anoptimum droplet size for a maximum collec-tion efficiency." In practice, this optimumsize is from 500 to 1000 microns.

Spray towers are often used as precool -era where large quantities of gas are in-volved. Operating characteristics includelow pressure drop (usually less than 1 inchof water, exclusive of mist eliminator sec-tion and gas distribution plate), ability tohandle spray liquid having a high solid con-tent (using water recirculation because oflarge spray nozzle clearance and spray drop-let size), and moderate liquid requirements(from 5 to 20 gallons per 1000 cfm). Theirchief disadvantages are low scrubbing effi-ciencies for dust particles in the 1- to 2-micron range and large space requirements.Spray towers are usually limited to the col-lection of particles of 10 microns or larger.

Figure 4-15 shows a typical spray towerlayout. 33 Gas entering the base of the spraytower passes through inlet conditioningsprays, through a distribution plate, throughone or more bank,: of spray nozzles, andthrough a mist eliminator section. The misteliminator is usually necessary in a tower

54

operating at gas velocities of over 6 feet per

The base gas distributor plate may con-sist of a perforated plate with uniform holedistribution or a support plate covered withfrom 6 to 12 inches of tower packing.4.4.2.3 Centrifugal Spray ScrubbersTheefficiency of collection of particles smallerthan those recovered in a gravitationalspray tower can be improved by increasingthe relative velocity of the droplets and gasstream. This may be achieved by using thecentrifugal force of a spinning gas stream.

Centrifugal spray scrubbers are of twotypes. In the first type the spinning motionis imparted to the gas stream by a tangen-tial entry such as shown in Figure 4-16a.The principal benefit is derived from thewetted walls, which prevent reentrainmentof separated material. Best collection is ob-tained by spraying countercurrently to gasflow in the inlet duct at water rates offrom 5 to 15 gallons per 1000 cubic feet ofgas and at pressure drops in excess of 3inches of water. 37 Figure 4-16b shows thisprinciple employed with a tangential basegas inlet. The liquid spray is directed out-ward from sprays set in a central pipe. Anunsprayed section above the nozzles is pro-vided so that the liquid droplets containingthe collected particles will have time toreach the walls of the chamber before com-ing into contact with the gas stream.

In the scrubber desigu illustrated in Fig-ure 4-16c water is sprayed tangentially in-ward from the wall as an aid in impartingcentrifugal motion to the gas stream. Thescrubbing liquid is introduced through noz-zles at a pressure of 400 pounds per squareinch (gauge).

Water requirements are approximately 5gallons per 1000 cubic feet of gas. Operat-ing pressure drop ranges from 1.3 to 2.3inches of water with removal efficiencies ashigh as 96 percent for 2- and 3-micron par-ticles. 88

In the second design, (Figure 4-16d) therotating motion is given to the gas streamby fixed vanes and impellers, and the scrub-bing liquid is introduced centrally either asa spray or liquid stream."

This type of scrubber is used as a final

.41

.10101010wommOrmum/ \/\ N

TA AGAS IN --No'

STRAINER

PIPE

PIPE

MIST ELIMINATOR

GAS DISTRIBUTOR PLATE

Fiume. 445. Typical layout for spray tower.(Courtesy 01 Spraying Systems Company)

55

DUSTYGAS

CLEANED GAS

ANTICARRYOVER BAFFLE

SPRAY RINGWATER SUPPLY

a. LARGE DIAMETER IRRIGATED CYCLONE

VERTICALSPRAYRISERS

QUICKOPENINGNOZZLELATCHES

CLEAN GASOUT

f

TOWER NOZZLES,DIRECTEDCROSSFLOW

FLEXIBLEPIPING

RECTANGULARINLET

FLUSHING JETS,DIRECTEDDOWNWARD

66

WASTE OUT

FRESH WATERSUPPLY

c. CYCLONIC SPRAY SCRUBBER.(Courtesy of Buffalo Forge Company)

CLEAN GAS OUT

CORE BUSTER DISK

SPRAY MANIFOLD

DAMPER

WATER WATEROUT IN

b. PEASE ANTHONY CYCLONIC SCRUBBER(Courtesy of Chemical Construction Corporation)

SEPARATOR

BAFFLE

GASIN- GAS

WATER

WATER OUT

CLEAN GASOUT

WATER

IMPINGEMENTPLATES

d. MULTIWASH SCRUBBER.(Courts s y of Claud. B. Scitne.bl. Con.00ny)

FIOLTRZ 4-16. Centrifugal spray scrubbers.

cleanup after spray dryers, calciners, cool-ers, crushers, classifiers, and cupolas.

4.4.2.4 Impingement Plate ScrubbersIm-pingement plate scrubbers, shown in Figure4-17a, consist of a tower equipped with oneor more impingement stages, mist removalbaffles, an dspray chambers.37 The im-pingement stage (Figure 4-17b) consists ofa perforated plate that leas from 600 to 3000

IMPINGEMENTBAFFLE STAGE

AGGLOMERATINGSLOT STAGE

o. IMPINGEMENT SCRUBBER

holes per square foot and a set of impinge-ment baffles so arranged that a baffle islocated directly above each hole. The perfo-rated plate is equipped with a weir to con-trol the level of scrubbing liquid on the plate.The liquid flows over the plate and througha downcomer to either a sump or the lowerstage.

The dust-laden gas enters the lower sec-tion of the scrubber and passes up through

TARGETPLATE

ORIFICEPI. ATE

WATERLEVEL

GAS FLOW

ARRANGEMENT OF "TARGET PLATES"IN IMPINGEMENT SCRUBBER

WATER DROPLETS ATOMIZEDAT EDGES OF ORIFICES

GAS FLOW

DOWNSPOUT TOLOWER STAGE

b. IMPINGEMENT PLATE DETAILS

Flom 4-17. Imringement plate scrubber.

57

a spray zone created by a group of low-pres-sure sprays. As the dust-laden gas passesthrough the impingement stage, the highgas and particle velocity (from 75 to 100feet per second) effectively atomizes theliquid at the edges of the perforations. Thespray droplets, about 10 microns in size,enhance collection of fire dust.

Overall efficiency for a single plate mayrange from 90 to 98 percent for 1-micronparticles or larger, with pressure drops offrom 1 to 8 inches of water and waterrequirements of from 3 to 5 gallons per 1000cubic feet of gas. 374.4.2.5 Venturi Scrubbers Obtaining highcollection efficiency of fine particles by im-pingement requires a small obstacle diam-eter and high relative velocity of the par-ticle as it impinges on the obstacle. In aventuri scrubber this is achieved by intro-ducing tae scrubbing liquid at right angle3to a high velocity gas flow in the throat(versa contracta) of the venturi. Very smallwater droplets are formed by the gas flow,and high relative velocities are maintaineduntil the droplets are accelerated to theirfull speed.

In the venturi scrubber the velocity ofthe gases alone causes the disintegration ofthe liquid. The energy expended in thescrubber is accounted for by the gas streampressure drop through the scrubber, exceptfor tae small amount used in the spraysand mist separation chamber.

A second factor which plays a part inthe effectiveness of the venturi scrubberis the conditioning of dust particles by con-densation. If the gas in the reduced-pres-sure region in the throat is fully saturated,or (preferably) supersaturated, some con-densation will occur on the particles in thethroat due to the Joule-Thompson effect.Condensation will be more pronounced if thegas is hot, due to the cooling effect of thescrubbing liquid. This helps the particleto grow, and the wetness of the particlesurface helps agglomeration and separation.

Gas velocities of from 200 to 600 feetper second are attained in the venturithroat." Water is either injected into thethroat of the venturi as a spray (Figure4-18a) or by means of a weir box (Figures

58

4-18b and 4-18c) in quantities of from 5to 7 gallons per 1000 cubic feet of gas.

Figures 4-18b and 4-18c show a scrubberthat uses an overflow weir on the walls up-stream of the venturi. This method of wa-ter injection has the advantage of allowingthe scrubbing water to be recirculated tomuch greater exteet than is possible withsystems using ,mall jets.

Recent developments have taken the formof finding methods of injecting water toreduce nozzle wear and pump requirements,and in maintaining pressure drop with vary-ing gas flows. Methods of maintaining pres-sure drop and scrubbing efficiency with va-rying gas flow rates have been centered inthe development of variable venturi throats.

The flooded disk (variable-throat-orificescrubber) illustrated in Figure 4-19 is arelatively new development." Scrubbingliquid is fed to the centee of the orificeplate, which serves to distrIbute the liquidacross the orifice throat. The pressure dropand efficiency performance is comparableto other venturi scrubbers. The scrubbingefficienc,y and pressure drop may be ad-justed by changing the position of the

The operating pressure u. op across theunit ranges from 6 to 70 inches of water.Water recirculation rate is about 5 gallonsper 1000 cubic feet of gas; make-up waterrequired is about a gallon per 1000 cubicfeet.

In the venturi jet scrubber the scrubbingliquid may be supplied in the form of a high-velocity jet directed along the axis of aventuri throat. The ejector venturi scrub-ber uses the velocity of the contacting liquidto pump, scrub, and/or absorb the entrainedgas.

The mechanical efficiency of the venturijet stream in pumping the gas may rangeas high as 16 to 17 percent of the total en-ergy input. The energy requirements rangefrom 1 to 5 horsepower per 1000 cubic feetper minute. Correspending liquid require-ments range from 20 to 50 gallons per 1000cubic feet of gas. Increased collection effi-ciency requires increased energy expendi-ture. 42, 43

In the multiple-venturi jet scrubber (Fig-ure 4-20), a nozzle sprays a hollow cone of

water into the belled venturi entrance sothat the spray strikes the throat wall andrebounds in the form of a flue spray aright angler to the gas stream. The waterpasses through the gas stream twice beforepassing through the venturi diffuser sec-

tion. Features of the design are low waterusage and low pressure drop.

The vertical venturi differs from the con-vrtItional venturi scrubber in that the gasflow is directed upward to produce a turbu-lent mixing action of the gas stream and sus-

b.

c.

FIGURE 4-18. Venturi scrubber may feed liquid through jets (a), over a weir (b),or swirl them on a shelf (c).

(Courtesy of UOP Air Correction Divisior)

69

penaing scrubbing liquid in the diffuser sec-tion of the venturi (Figure 4-21). Liquidrecirculation occurs both internally by eddymixing action in the diffuser and externallyby return of the scrubbing liquid, after par-tial solids separation, to the venturi throat.The carryover slurry, when separated bythe centrifugal action of the gas streamcaused by the stationary impeller, returnsby gravity to the solids concentrator. Theprincipal advantages of this design are highsolids content of slurry, low water usage (1to 3 gallons per 1000 cubic feet of gas),elimination of a recirculation pump, rela-tively low pressure drop, and low operatingcosts. 15

4.4,2.6 Packed Bed ScrubbersA tower orbox packed with such packing as Raschigrings, saddles, tile, and marbles may beused for dust and mist collection as well asfor gas absorption (Figure 4-22). Twobasic packed bed designs, cross-flow (Fig-ure 4-23a) and countercurrent flow (Fig-

DUSTY GASINLET

ure 4-23b) exist. The packed bed may beheld in piaci., ;fixed), free to move (fluid),or covered with water (flooded). The irri-gating liquia serves to wet, dissolve, and/orwash the entrained particulate matter fromthe bed. Dry beds may he used for the elim-ination of mists. In general, smaller-diam-eter tower packing gives a higher particletarget efficiency than larger-sized packingfor a given gas velocity.

The cross flow, fixed bed, packed scrub-ber (Figure 4-23a) operates with the gasstream mol, ,g horizontally through thepacking while the irrigating liquid flowsby gravity vertically through the packing.This type of scrubber operates with a verylow pressure drop and water requirements,both of which are about 40 percent of thatrequired for cnnter flow operation. Theleading face of the packed bed is usuallyslanted from 7 to 10 degrees (depending ongas velocity) in the direction of the oncom-ing gas stream to ensure completc, wetting

CLEAN GAS OUTLET

CYCLONE MISTSEPARATOR

ADJUSTABLE DIE..< --

TANGENTIALINLET

STUFFING BOX

SCRUBBING WATER INLET

60

DISKPOSITIONING ROD

SCRUBBING WATER OUTLET

FIGURE 4-19. Flooded disk (variable throat orifice) scrubber.(Courtesy of Research Cottrell Incorporated)

FIGURE 4-20. Multiple-venturi jet scrubber.(Courteey of Buell Corporat(on)

61

FIGURE 4-21. Vertide venturi scrubber.(Courtesy of UOP Air Correction Division)

and washing of the face of the bed by thefalling irrigation liquid. Inlet sprays areusually included in this design to conditionthe inlet gas and scrub the face of thepacked bed. The first few inches of the bedmay be irrigated more heavily to preventbuild-up of The back of the LA isusually operated dry to act as a demistingsection."

Liquid requirements range from 1 to 4

62

gallons per 1000 cubic feet of gas, with pres-sure drops of from 0,2 to 0.5 inch of waterper foot of bed. Collection efficiency in ex-cess of 90 percent may be achieved whencollecting particles of 2 microns or larger,with dust loadings as high as 5 grains percubic foot." Higher dust loadings may behandled if the dust is readily soluble.

Countercurrent flow (Figure 4-23b) isthe most common design used in packedbeds. Gas is forced upward through thepacking against gravity flow of the liquid.

Countercurrent flow works best at a pres-sure drop and gas velocity that cause thebuildup of water in and on top of the bed,usually 0.5 to 1.0 inch of pressure drop perfoot of packing depth. '4 Pressure drop inexcess of this amount will usually result inexcessive liquid entrainment and reducedefficiency. Liquid flow rates of from 10to 20 gallons per 1000 cubic feet of gas arecommon. Water efficiency will then be ata maximum and bed clogging at a minimum.

In cocurrent, or parallel flow, the gasstream and liquid pass through the bed inthe same direction. In this type of oper-ation the irrigation liquid keeps the packedbed from being clogged, and the gas andliquid both assist in washing solids throughthe bed. The advantage of this type ofoperation is the small liquid requirement,7 to 15 gallons per 1000 cubic feet of gas.The operating pressure drop is on the orderof 1 to 4 inches of water per foot of packedbed.

The flooded-bed packed scrubber is oper-ated as a counterflow packed tower (Fig-ure 4-24). The packing consists of a 6-inch thick bed of spherical icking. Dust-and fume-laden air enters below the bed ofglass marbl.s and passes through a spraysection and up through the flooded bed ofspheres. Bubbles formed in the bed createa turbulent layer approximately 6 inchesin depth. The marbles have a constant, gen-tle rubbing action which makes them self-cleaning. Entrained moisture is removed byimpaction or inertial separation in a misteliminator section. The scrubber is reportedto be 99 percent efficient in removing par-ticles 2 microns and larger with a pressuredrop of from 4 to 6 inches of water.49

jr

.;

0 V

-1r IPALL RING

TELLERETTE

MASPAC

RASCHIGRING

fr

PLASTIC INTALOXSADDLE

LESSINGRING

.41

CROSSPARTITIONRING

SINGLE SPIRAL DOUBLE SPIRAL TRIPLE SPIRALRING RING RING

BERLSADDLE

INTALOXSADDLE

CERAMIC PACKINGS

FIGURE 4-22. Wet scrubber packings.

63

Scrubbing liquid requirements are from 2to 21/2 gallons per 1000 cubic feet of gas.Liquid with a high solid content can be re-circulated. The scrubber is capable of han-dling dust loads of up to 40 grains perstandard cubic foot. Flooded bed packedscrubbert, may be used to control emissionsof acid vapors, carbon black, ceramic frit,chlorine tail gas, cupola gas, and ferritedusts.

Fluid bed packed scrubber (Figure 4-25)packing consists of low density polyethyleneor polypropylene spheres about 11/2 inchesin diameter that are continually in motionbetween the upper and lower retaininggrid. 15

The scrubbing liquid is sprayed I.:5W11-ward over the balls in a countercurrentflow of dirty gas. Gas and liquid arebrought into contact on the surface of thewetted spheres and in the spray betweenthem.

The spheres are continually cleaned byconstant motion, and the bed is not readilyplugged.

Pressure drop ranges from 6 to 8 inchesof water, and collection efficiencies are inexcess of 99 percent for particles of 2 mi-crons and larger,'9 Liquid and dust han-

LIQUIDDISTRIBUTION UNWETTED

PACKING HEADERS , SECTION FOR

SUPPORT , , MIST ELIMINATIONGRID 1

-FL, PACKING SUPPORTGRID

DIRTYGAS IN

FRONTCLEANINGSPRAYS

64

a. CROSSFLOW SCRUBBER

CLEAN GAS

OUT

cluing capacities are comparable to the flood-ed bed packed scrubber. 45

4.4 2.? Self-Induced Spray Scrubbers.Theparticle collection zone of the self-inducedspray scrubber is a spray curtain that isinduced by gas flow through a partially sub-merged orifice or streamlined baffle. Mistcarryover is minimized by baffles or swirlchambers. In the submerged orifice scrub-ber (Tigure 4-26a) the impingement gasvelocity of about 50 feet per second createsdroplets in the 300- to 400-micron range. ,°Blaw Knox (Figure 4-26b) and Doyle (Fig-ure 4-26c) scrubbers operate with impinge-ment velocities of from 120 to 180 feet persecond. 51

Pressure drop ranges from 2 to 16 inche;,and water requieenent is about 1 gallonper 1000 cubic feet of gas when water isrecycled.

The chief advantages of this self-inducedspray scrubber design are its ability to han-dle high dust concentration and concentrat-ed slurries.

Sludge removal may be accomplished bydrag chains or by sluicing the sludge tosuitable separators.4.4.2.8 Mechanically Induced Spray Scrub-bersIn the mechanically induced spray

GAS OUTLET

MISTELIMINATORSECTION

LIQUID` INLET

'V' WEIRDISTRIBUTOR

GAS INLET--

PACKEDSCRUBBINGSECTION

PACKINGSUPPORT

LIQUIDOUTLET

b. COUNTERCURRENTFLOW SCRUBBER

FIGURE 4-23. Packedbed scrubbers.(Courtesy of Chemical Engineering Magazine)

scrubber (Figures 4-27a and 4-27b) high-velocity sprays are generated at right anglesto the direction of gas flow by a partiallysubmerged rotor. Scrubbing is achieved by

impaction because of both high radial drop-let velocity and vertical gas velocity. Liq-uid atomization occurs at the rotor and atthe outer wall. 52

I

,

MISTELIMINATOR

TURBULENTLAYER i; 1 4A

1

FIGURE 4-24. Flooded-bed scrubber.(Courtesy of National Dust Collector Corporation)

65

MIST ELIMINATOR

CLEAN GAS

FROMRECIRCULATION 4.4101-PUMP

SCRUBBING LIQUOR

RETAINING GRID

1:ASSUSSSCSS

Pit

FLOATING BED OF LOW-DENSITY SPHERES

RETAINING GRID

TORECIRCULATION +11.PUMP

66

FEEDGAS

soy. TO DRAINOR RECOVERY

Fict-RE 4-25. Floating t.$11 (Assid1-14) pat ktli terabbel(Cotrfttip of rOP Air Correction Pirition)

SCHuitei SwiRt.ORIf ICE DUST COLLECTORKw's, rA thlmot Ststo Mott C., Me.

WRIT CAS

GAS

RATER

OAS OUTLET

SEPARATORPLATES

PRIMARYSEPARATOR

GASCONTACTINGTUBE

GAStILET

S. LIOU10 VORTEX CONTRACTORICa.e.tr. 0114. C.

t. DOME SCRUBBERst 0-44. iver t

Ficras 4-26. Seltindated spray scrubbers.67

0. SCPANE0 VERTICALROTOR OUST COLLECTOR(Ceulet Unite/ Shoot Moil Co., frt.,

b. CENT ER SPRAY NIGHVELOCITY SCRUBBER(Ceolt -7 a 1t Eneineotino Msgetir9)

Ficuttn 4 27. Mechanically induced spray tcrubbers.

Power and liquid requirements rangefrom 3 to 10 horsepower and from 4 to 5gallons per 1000 cubic feet of gas for thehigh-velocity design (Figure 4-27b), de-pending on particle size and the desiredlevel of scrubbing efficiency."

Advantages of this type of scrubber arerelatively low liquid requirements, smallspace requirements, high scrubbing effi-

DIRT AND WATERDISCHARGED ATBLADE TIPS

c ency, and high dust load capacity. Therotor, however, is susceptible to erosionfrom large particles and abrasive dusts,and high-energy scrubbing applications mayrequire the use of additional mist elimi-nation equipment.

4.4.2.9 lYsintegrator ScrubbersA disinte-grator scrubber consists of a barred rotor

arDIRTY GASINLET

S" 1.-

0

WATER ANDSLUDGE OUTLET

CLEAN GASOUTLET

WATER SPRAYNOZZLE

FIGt1ts 4-28, Centrifugal fan *-et irrabbet.(Cortriery of Arntriean Air niter Compaay)

69

within a barred stator. Water is injectedaxially through the rotor shaft and is sep-arated into fine droplets by the high rela-tive velocity of rotor and stator bars. Dustparticles are impacted by the high velocityliquid droplets.

Water and power requirements rangefrom 4 to 9 gallons per minute and from7 to 11 horsepor. er, respectively, for each1000 cubic feet per minute of gas handlingcapacity. Scrubbing efficiency is about 95percent for 1-micron particles and may beimproved by increasing either the water rateor the number of stator and rotor bars.Scrubbing efficiency is independent of dustloading, and exit dust concentrations rangeas low as 0.001 grain per standard cubicfoot. Si

Advantages of this scrubber are highcollection .'fficlency for submicron particlesand low spare requirements. The principaldisadvantage is its large power requirement.

4.4.10 Centrifugal Fan Wet ScrubbersThis type of scrubber (Figure 4-28) con-sists essentially of a multiple-blade centrif-ugal blower.

Design pressure drop is about 6% incheswith a maximum pressure drop of 9 inches.Water requirements range from 3 to 1.6gallons per 1000 cubic feet of gas and power

requirements range from 1 to 2 horsepowerper 1000 cubic feet per minute. 53

The chief advantages are low apace re-quirements, moderate power requirements,low water consumption, and a relativelyhigh scrubbing efficiency.

4.4.2.11 Wine Wet ScrubbersIn this axial-fan.powered gas scrubber (Figure 4-29), awater spray and baffle screen wet the par-ticles, and centrifugal fan action eliminatesthe wetted particles through concentric

.louvers.Pressure drop is about 6 inches of water,

and water consumption is about 1 gaEonper 1000 cubic feet of gas. The moistureremoval capacit:. of the eliminator sectionis sensitive to .hanges in gas flow rate. Av-erage removal efficiency is in excess of 99percent for particles ranging in size from6 to 10 microns. 7's

Advantages of the inline wet scrubberare low installation space requirements andlow installation costs. Coal and metal min-ing industries use inline scrubbers.

4.4.2.12 Irrigated Wct Filters Irrigatedwet filters (Figure 4.30a) consist of anupper chamber, containing wet filters andspray nozzles for cleaning the gas, and alower chamber for storing scrubbing liquid.

70

Ftct-as 4-29. !aline wet scrubber.(Co/tasty of Joy Matufaetwriag Compaq')

1

SPRAY HEADER CONNECTION

ACCESS DOORS

IMPACTION

FLOAT VALVE

QUICK FILL

OVERFLOW

LIQUID LEVELINDICATORS

SUCTION CONNECTION

a. WETTED FILTER

OUST-LADEN GASVENAL CONTRACTA

WATER FILM

WATER DROPLETS

pu,PINGtvENT PLATE FILTER

WATER FILM

FIGt1tE 440. Wetted and impingemott plate filters.(Coln-ten, of Rojo to Porpe Coo Iran?)

71

Liquid is recirculated and sprayed onto thesurface of the filters on the upstream sideof the bed. Two or more filter stages con-structed in series are used. A dry bed con-taining small diameter fibers may be add-ed as a final cleanup stage to remove spraymist.s7.3/4 A wetted impingement plate maybe used in the first compartment to reducethe particle load on the following stage( Figure 4-30b) . 59. so

The number of cleaning stags to be usedIs determined by the characteristics of thegas stream and cleaning requirements. Gasvelocities range from 200 to 300 feet perminute with a liquid requirement of approx-imately three gallons per minute per squarefoot of filter area (8 to 10 gallons per 1000 cu-bic feet of gas). Pressure drop, which rangesfrom 0.2 to 3 inches of water per 4-inchbed depth, is dependent on the gas loading,liquid loading, and fiber bed density. Nor-mal bed thickness may range from 1 to 4inches, based on scrubbing requirements. 57

The chief mechanism of irrigated wetfilters involved in the capture of particulatematter is interception by individual fila-ments in the filter. Both particle removaland gas absorption can be accomplished, andthe irrigation feature aids in removal ofsolid particulate matter.

4.4.E.13 Wet Fiber Mist EliminatorsTwomechanisms, Brownian diffusion and iner-tial impaction, are involved in the separa-tion of mist and dust particles in wet fibermist eliminators.

Brownian diffusion dominates in mist col-lection in which fiber beds with large spe-cific surface areas are used, gas velocitiesrange between 6 and 80 feet per minute,and the mist consists largely of submicronparticles. A characteristic of Brownian dif-fusion control is that collection efficiencyincreases with decreasint gas velocity be-cause of increased filter ...rd retention time.This collection mechanism has some effecton the collection of 8-micron particles anda major effect on the collection of 0.6 mi-cron particles. Brownian motion is an im-portant factor in particle capture by directint irception.

72

4,,

Inertial impaction dominates in particlecollection above 3 microns in site at gasvelocities in excess of 30 feet per econd incoarse filter beds. Inertial impaction effi-ciency increases with increasing gas veloc-ity.

Fiber diameter and the distance betweenadjacent fibers are important in determin-ing collection efficiency and pressure drop.Because high mechanical bed stability isnecessary for operation in the high pres-sure drop range, design of mounting andsupport structures becomes critical."

Wetted filters are available in two de-signs, low-velocity (5 to 30 feet per min-ute), illustrated in Figure 4.31, and high-velocity (30 to 90 feet per minute), illus-trated in Figure 4.32. The low-velocity de-sign consists of a packed bed of fibers re-tained between two concentric screens. Mistparticles collect on the surface of the fibers,coalesce to form a liquid film that wets thefibers, and are moved horizontally anddownward by gravity and the drag of thegases. The liquid flows down the innerscreen to the bottom of the element andthrough a liquid seal to a collection reser-voir. Collection efficiencies are reported tobe in excess of 99 percent on particles small-er than 3 microns at operating pressuredrops of from 5 to 15 inches of water. Effi-ciencies increase when the scrubber is op-erated below design capacity.

The high-velocity filtering element (Fig-ure 4-32a) consists of a packed fiber bedbetween two parallel screens. A multiplemounting is shown in Figure 4-32b. Liquidflow patterns are similar to those of thelow-velocity filter, and removal efficienciesrange from 85 to 90 percent for 1- to 3-micron rsrticles and pressure drops of from6 to 10 inches of water."

This type of wet filter finds applicationin collection of sulfuric, phosphoric, andnitric acid mists and in the separation ofmoisture and oil from compressed gases.Disposable filters are used in the recoveryof platinum catalysts used in nit- i^ acidmanufacture and in the collection 04 drusesand bacteria, and radioactive and toxicdusts."

CLEANGAS OUT

SUPPORT PLATE

SCREENS

FIBER PACKING

LIQUID DRAINAGE

LIQUIDAr.SEAL

POT

LIQUID BACK TO PROCESS

e. LOW.VELOCITY FILTERING El EMENT

CLEAN GASESTO STACK

,k4 TUBE SHEET

I 41 110$8 1. 6

ACIDLADENOASES

51

BRINK MISTELIMINATOR

ELEMENTS

RECOVEREDH2SO4

b. MULTIPLE MOUNTING OF I beiVEL"ITY FILTER.ING ELEMENTS

Flom 4-31. Loelocit Altering elements.(Cosrfesy of Monsanto CoiApas))

The wire mesh filter consists of an even-ly spaced knitted wire mesh and is usuallymounted in horizontal beds (Figure 1-33).The principal collection mechanism Is iner-tial impaction. Rising mist droplets strikethe wire surface, flow down the wire to awire Junction, coalesce, and flow to thebottom surface of the bed, where the liquiddisengages in the form of large droplets andreturns by gravity to '-ve process equip-ment.*4

Operating pressure drop is usually lessthan 1 inch of water with gas velocities offrom 10 to 16 feet per second. Recent de-velopment has centered on the area of highenergy filtration in which pressure dropsof from 36 to 40 inches of water gauge havebeen used.

Factors governing maximum allowablepas velocities include gas and liquid density,sur:acc tension, viscosity, bed specific sur-face ar a, liquid !oading, and suspended sol-ids c.)nt ent. st

Advantages in the use of fiber (liters andwire mesh mist collectors are high reov-al efficiency, simplicity of operation, lowmaintenance in dust-free service, low initialcost, and recovery of valuable producis with-out dilution.

4.41.14 Imping(mcni Reiff,. Mist Elimina-torsBaffle mist eliminators offer one ofthe simplest methods of controlling large-diameter solid and liquid particulate emis-sions. A variety of designs are in use. Fig-ure 4 -34 shows the arrangement of baffles

73

e. 111014VELOCITY FILTERING ELEMENT

DIRTY GASIN

MANHOLES

AI /

CLEANGAS'OUT

FIBERELEMENTS

LIQUIDLEVEL

ACIDOUT

I. MULTIPLE MOUNTING OF HIGHVELOCITY FILTER.ING ELEMENTS

MUM 442. 1110relocity Altering elements.(Coxriesy of Moms:111k) CO 'Apo my)

EFFLUENT FROMABSORBER

0. MIST ELIMINATOR ARRANGEMENT IN VESSELABOVE ACID PLANT ABSORBER

(Cemooty of Chi 04.1 tri intern.. Prevost Masetic4)

'KIVU 4-32. Wire mesh mitt eliminators.

t. ONE-PIECE DEMISTER ®(Castity s. O. N. Yolk Cs., Inc.)

suecemfully used in the reduction of emis- achieved on particulate matter which rangedMons from coke quenching operations," An from 16 to 200 mg E gas velocities ranging85 to 90 percent reduction of emissions was to a high of 36 fc% .r second. A significant

74

A

-4

TOP VIEW

TOP OFQUENCHTOWER

SPRAYNOZZLES

WATER SPRAYMANIFOLD

BAFFLES

SECTION A-A SIDE VIEW b. MIST ELIMINATOR BAFFLES

e. DIAGRAM OF BAFFLE SYSTEM St olbiNt., (LEAN.ING VIER SPRAYS AND BAFFLE ARRANGEMENT

FioUtz. 4-34. Coke quench mist elimination baffle system.(Cowries), of V.S. Skit Corp.)

LIP

FLOW

40' BENT PLATE UNIT

ri OM 443. Details of baffle desip.(Comeitty of Chemical gogintethrg

Progress Magatiae)

reduction in water droplet fallout was alsoachieved. The baffles were operated drywith short spray periods to prevent thebuildup of solids." Figures 4-35, 4-36, and437 show the common layouts of mist elim-inator baffles used In spray chamber scrub-bers.". " Mist removal efficiencies of ashigh as 95 percent may be achieved for theremoval of 40-micron spray droplets up toa maximum gas velocity of 25 feet per sec-ond and pressure drops of from 1 to 2

OASFLOW

rIaltE 1-36. Streamline mist eliminator baffle&

inches a water. Velocities in excess of 25feet per second result in the re-entrainmentof liquid droplets.4.4.Y.IS Vont-Type Mist EliminatorsVane-type mist eliminators have a range of op-eration of from 10 to 50 feet per second, withcollection efficiencies reported to be as highas 99 percent for 11-micron particles andwith pressure drops from 0.1 to 2 inches ofwater. The principal advantage of vane type

75

FLUEGAS

16 GAUGE PLATE

WIRE MESH317 STAINL

}:cuss 4-37. Screen and mist eliminator details.(Comrtesy of Paper Trade Journal)

BERL SADDLES

"kit) INIA.1%.1%.I ts 1, tr ........

riot as 4-35. fled of Berl saddles addedstack.

(Courtesy of Chemical EngineeringProgress Magntirre)

to discharge

over baffle mist eliminators is the widerrange of operation at comparable collectionefficiencies."

4.4.t.16 I (irked Red Mist EliminatorsFigure 4-88 shows a packed bed Mack misteliminator. Removal efficiencies of suchdevices may range to as high as 65 percentAt gas velocities from .7 to 10 feet per sec-ond. Mist re-entrainment occurs at highergas velocities because of the turbulent na-ture of gas flow in packed beds. This typeof mist eliminator is often used for tail gas

76

cleanup in sulfuric and phosphoric acidmanufacture. 65.70

.$,4.2.17 .list and Vapor SuppressionMistformation from bubbling solutions, such asplating baths and acid pickling baths, maybe reduced by the addition of wetting agents.Foaming and non-foaming types are pres-ently used to reduce both surface tensionand bubble size."" Smaller bubbles es-cape the treated bath with less violenceand with a corresponding reduction in theformation of mist particles. Foaming agentsreduce mist formation by reducing bubbleescape energy and by trapping the mist par-ticles in a dense foam. The use of surfac-tants in chrome relating baths can reducechromic acid losses by as much as 45 per-cent with a corre:ponding reduction in airand water pollution.

Foam, which has the disadvantage oftrapping hydrogen gas, can create 6 firehazard and must be continually replaced.Floating plastic objects such as polyethyleneballs, hollow rods, and cylinders are alsoused." The floating plastic used to coverthe surface serves as a trait top and misteliminator and reduces heat losses and ven-tilation requirements.

in one case the use of 4.i-inch balls tocover 90 percent of the surface area of sul-furic acid solutions used in the electro-refining of copper resulted in a 90 percentreduction in evaporation losses and a 70percent reduction in heat loss. The savingsfrom the reduction in loss of methylatedspirits (an addition agent) over a 2-weekperiod paid for the balls. In addition to a90 percent reduction in air pollution fromsulfuric acid mist, there was a noticeablereduction in corrosion rates. The approx-imate cost of the ball cover is $1.5G to $2.00per square foot of tank surface area."4.4.2.18 Liquid Distribution --Wet scrubbersrequire a uniform and consistent liquid dis-tribution pattern for the maintenance ofhigh scrubbing efficiencies at minimumwater rates. Liquid distribution in wetscrubbers is accomplished by spray nozzlesor spinning disk atomizers. Weir box orsieve plate distributors may be used forpacked towers.

4.42.19 Spray Nozzles Spray scrubbers re-quire liquid droplets that are closely sizedin order to avoid liquid entrainment at max-imum gas flow rates, Since the scrubbingliquid is often recirculated, the spray noz-zles must be capable of handling liquidswith fairly high solids content.

The basic functions of liquid spray noz-zles and atomizers are to create small drop-lets with large surface areas, to distributethe liquid in a specific pattern, to controlliquid-flow metering, and to generate high-velocity droplets."' At least one of theabove functions is involved in every indus-trial spraying prix mss, and spray nozzleselection depends on the specific functionto be performed. The spray devices used inwet scrubbers may be classified as pres-sure nozzles (hollow and solid cone and im-pingement and impact), rotating nozzles(spinning atomizers), and miscellaneousnozzles.

In hollow-cone spray nortles, the fluid isfed to a whirl chambe a tangential inlet(Figure 4.39a) or a fixed spiral (Figure4.39b)so that the fluid acquires rapid ro-tation. The mike is on the axis of thechamber, and the fluid exits as a hollowconical sheet and then breaks up into drop-lets. The angle of the spray is determinedby the dimensions of the swirl chamber andthe pitch of the nozzle. A spiral with a shortpitch produces a wide-angle spray; con-versely, a long pitch produces a narrow-angle spray. The spray angle may rangefrom 15 to 135 degrees.

Hollow cone spray nozzles with cone an-gles of from 15 to 20 degrees (Figures 1-39band 449c) are used in venturi jet scrub-bers for maximum turbulence and mixingin the throat and diffuser section. Largernozzle angles are used in air washers andhumidifiers.

The solid cone nozzle (Figure 4-39d) isa modification of the hollow cone nozzleused when complete coverage of fixed areais desired. The nozzle is essentially a hol-low-cone nozzle with the addition of a cen-tral axial jet. The jet strikes the outer ro-tating fluid inside the nozzle orifice and isbroken into droplets. The angle of the sprayis a function of nozzle design and is nearly

independent of pressure. A second type ofsolid cone spray nozzle (Figure 4-39e) con-sists of an orifice and external helicalspiral. The nozzle is essentially non-clog-ging and finds use in packed column distrib-utor design. Commercial solid cone nozzlesare available with included angles of from30 to 100 degrees. Wet scrubbers nearlyalways use nozzles with large angle sprays.Solid-cone sprsy nozzles are frequentlymounted in clusters (Figure 4-39f). Liquiddistribution is enhanced by using severalsmall rflays instead of one large spray ofthe same capacity. Liquid distribution isalso improved by the proper selection ofpipe manifold size. '8

In the impingement-type nozzle (Figure4.39g), a high-velocity liquid jet is directedat a solid target or a liquid stream. Properorientation and shape of the target or con-trol of the size and shape of the two fluidstreams produces a ham cone, fan, ordish-shaped spray pattern. The nozzles arerobust and simple in shape, and despitehigher cost, they are frequently used in wetscrubbing towers because of their more uni-form distribution of droplet size.

Rotating nozzles (spinning atomizers) area type of liquid distributor (Figure 4.39h)less frequently used in gas scrubbing thaneither hollow cone or solid cone nozzles.The droplets produced by rotating nozzlesare uniform in site and can be controlledwithout regard to liquid feed rate by chang-ing the disk speed. Spinning atomizers areused in some wet scrubbers and have theadvantage of being able to handle slurriesthat could clog conventional nozzles. Amongmiscellaneous atomizers, the fan jet (Fig-ure 4.391) is used in wetting and light hu-midification operations.

In packed tower and cross flow &rub-ber liquid distributor design, spray nozzlesand drilled pipe headers may be used todistribute liquid. Most packed tower liquiddistributors are of the weir box V-notchtype (Figure 4-10a). For low rates of gasflow, weir risers (Figure 4-40b) map beused. Submerged orifice plate distributors(Figure 4-40c) are also used. Liquid dis-tribution is critical in determining scrub-ber performance. 79

77

o. HOLLOW CONE SPRAYNOZZLE(Courtesy of Spray SystemsCompany)

d. SOLIO CONE SPRAYNOZZLE(Courtesy of SproyfAgineering Company)

h. SPINNING DISK SPRAYNOZZLE(Courtesy of Schutt* &Kaerting)

78

b. HOLLOW CONE SPRAYNOZZLE(Cototesy of Schutt. &Kaerting)

e. SOLID CONE SPRAYNOZZLE(Courtesy of Bete Compony)

i. MONOFAN NOZZLE(Courtesy of Sproy Engineer-ing Company)

c. HOLLOW CONE SPRAYNOZZLE(Courtesy of Schutt. &Kaerting)

f. CLUSTER SPRAY NOZZLE(Courtesy of Spray EngineeringCompany)

..$

g. PIN JET IMPINGEMENTSPRAY NOZZLE(Cowries, of Spray Engineering Company)

FIGIR 4-39. Spray nozzles commonly used in wet scrubbers.

o. PACKED 'POWER WEIR BOX LIQUID DISTRIBUTOR(Courtesy of Koch Engineering Company)

b. PACKED TOWER "WEIR RISER" LIQUID DISTRIBUTOR(Courtesy of U. S. Stemma, Company)

pr

e. "SUBMERGED ORIFICE" PLATE. DISTRIBUTOR

79

c.>

a

0

0yV

elel

'to

ref

Because spray nozzles frequently wear orclog and produce an uneven liquid pattern,they require frequent replacement and main-tenance. Weir box distribution, on the otherhand, is dependable and requires little main-tenance after initial leveling. Pumpingheads are also lower and result in lowerpower requirements and less maintenance.

Liquid distribution within a packed bedis also very important. Initial distributionof liquid onto the top of the bed is oftenenhanced by the use of small sized packingin the top of the bed.

Normal drip point requirements for weirbox distribution range from 8 to 10 pointsper square foot for vertical packed bedsand from 15 to 30 points for cross flowscrubbers.

Cross flow scrubbers normally containbaffles or corrugated walls around the pe-riphery of the packed bed to prevent gas

channeling. Packed beds above 15 feet inheight frequently require liquid redistribu-tion.

4.4.3 Typical Applications of WetScrubbers

ypical applications of wet scrubbers aretabulated in Table 4-6.

4.4.4 Water DisposalWater usage and waste disposal may be-

come critical factors in the final selectionof a wet scrubber. Waste quantity, particlesize distribution in the slurry, recovery val-ue, corrosiveness of the solutions, and mate-rials of construction are important factors,The final selection of a water treatmentor disposal system should not result in wa-ter, soil, or air pollution. Refer to refer-ences 80 through 92 for additional infor-mation.

Table 4-6.TYPICAL INDUSTRIAL APPLICATION OF WET SCRUBBERS

Scrubber type Typical applicationSpray chambers Dust cleaning, electroplating, phosphate fertilizer, kraft paper,

smoke abatementSpray tower Precooler, blast furnace gasCentrifugal Spray drier., calciners, crushers, classifiers, fluid bed processes,

kraft paper, fly ashCupolas, driers, kilns, fertilizer, flue gasImpingement plate

Venturi:Venturi throatFlooded diskMultiple jet

Venturi jetVertical venturiPacked bed:

FixedFlooded

Pulverized coal, abrasives, rotary kilns, foundries, flue gas, cupolagas, fertilizers, lime kilns, roasting, titanium dioxide processing,odor control, oxygen steel making, coke oven gas, fly ash

Fertilizer manufacture, odor control, smoke controlPulverized coal, abrasive manufacture

Fluid (floating) ball

Self-induced spray

Mechanically-induced sprayDisintegratorCentrifugal fan In line fanWetted filtersDust, mist eliminators:

Fiber filters

Wire meshBafflesPacked beds

80

Fertilizer manufacturing, plating, acid picalingAcid vapors, aluminum inoculation, foundries, asphalt plants,

atomic wastes, carbon black, ceramic hit, chlorine tail gas, pig-ment manufacture, cupola gas, driers, ferrite, fertilizer

Kraft paper, basic oxygen steel, fertilizer, aluminum ore reduction,aluminum foundries, fly ash, asphalt manufacturing

Coal mining. ore mining, explosive dusts, air conditioning, incin-erators

Iron foundry, cupolas, smoke, chemical fume control, paint sprayBlast furnace gasMetal mining, coal processing, foundry, food, pharmaceuticalsElectroplating, acid pickling, air conditioning, light dust

Sulfuric, phosphoric, and nitric acid mists; moisture separators;household ventilation; radioactive and toxic dusts, oil mists

Sulfuric, phosphoric, and nitric acid mists; distillation and absorp-tion

Coke quenching, kraft paper manufacture, platingSulfuric and phosphoric acid manufacture, electroplating spray

towers

4.4.4.1 Settling Tanks and PondsThismethod of disposal may be applied to scrub-ber discharges containing solid particulatematter that readily settles or is easily floc-culated by chemical treatment. Tank orpond size may be easily determined by labo-ratory sedimentation tests.'" Separation bysedimentation is usually limited to particleslarger than 1 micron or to particles thatreadily flocculate. Advantages are thatwaste products to be disposed of may besluiced to a burial pit, waste water may hechemically treated and reused, operationalcosts are low, and abrasi,/ solids can behandled. Disadvantages F ; that a largearea is required for the settling of smallparticles, ground water contamination fromponds is possible, and natural evaporationto the atmosphere occurs.

4.4.4.2 Continuous FiltrationThis methodof slurry treatment is usually applied wherethe solids have some recovery value or areporous or incompressible." Advantages area dewatered waste product and moderatespace requirements:Disadvantages are highinitial cost and relatively high maintenanceand operational costs.

4.4.4.3 Liquid CyclonesThe wet cyclonehas come into prominence in the last fewyears as a method -for concentrating solids.The advantages are low initial cost, lowmaintenance, ability to handle abrasive sol-ids, and low space requirements. Disadvan-tages are the production of high solids fil-trate or overflow and relatively high powerrequirements. 82

4.4.4.4 Continuo:a CentrifugeThis methodof solids separation can sometimes be ap-plied to submicron slurries at fairly highcollection efficiencies." The advantages arelow space requirements and a large varietyof designs for special requirements. Disad-vantages are high capital and operatingcosts and susceptibility to abrasion and cor-rosion.

4.4.4.5 Chemical TreatmentChemical treat-ment of liquid wastes includes treatmentwith chlorine, lime, soda ash, carbon dioxide,ammonia, corrosion inhibitors, coagulants,and/or limestone soak pits."-"

4.5 IIIGII-VOLTAGE ELECTROSTATICPRECIPITATORS

4.5.1 IntroductionThe high-voltage electrostatic precipitator

(ESP) is used at more large installationsthan any other type of high-efficiency par-ticulate matter collector. For many opera-tions, such as coal-fired utility boilers, thehigh-voltage electrostatic precipitator is theonly proven high-efficiency control deviceavailable today. High-voltage single-stageprecipitators have been used successfully tocollect both solid and liquid particulate mat-ter from smelters, steel furnaces, petroleumrefineries, cement kilns, acid plants, andmany other operations. Figures 4-41 and4-42 show typical electrostatic preciOtatorinstallations.

Electrostatic precipitators are normallyused when the larger portion of the particu-late matter to be collected is smaller than20 microns in mean diameter. When par-ticles are large, centrifugal collectors aresometimes employed as precleaners. Gasvolumes handled normally range from60,000 to 2,000,000 cubic feet per minute.Operating pressures range from slightly be-low atmospheric pressure to 160 pounds persquare inch gauge and operating tempera-tures normally range from ambient air tem-peratures to 760° F.

4.5.2 Operating PrinciplesSeparation of suspended particulate matter

from a gas stream by high-voltage electro-static precipitation requires three basicsteps:

1. Electrical charging of the suspend-ed matter.

2. Collectic., of the charged particulatematter on a grounded surface.

3. Removal of the particulate matterto an external receptacle.

A charge may be imparted to particulatematter prior to the electrostatic precipitatorby flame ionization or friction; however, thebulk of the charge is applied by passing thesuspended particles through a high-voltage,direct-current corona." The corona is es-tablished between an electrode maintainedat high voltage and a grounded collecting

81

FIGURE 4-41. Multiple precipitator installation in basic oxygen furnace plant.(Courtly of Koppers Co. Inc.)

82

1;11:0

a tVi -14 . t .e% )1. , 1-02,

11

dine 1w1C'

4r

' frih

'41o.

0.1,;Ii!tjr;o

l'sk;f.11.t.vi: I. .,,.4e t ,

; r.r

il -:,,..:j.11.1)1)1..

- 1_ r-,,;ii:,

..r,... 1 ;;st t..If i0k 1

..f., Y ." ryli ePi: r ''' '' 74fir.1retA.z:r " '' 11

V q Vii.:A r" ,

t' i' ./.0,. l f' i -

-f.: tr 1-, *11.1

5.

nri 1 "irate',

14r

FIGURE 4-42. Detarrer precipitators installed in steel mill.(Courtesy of Koppers Co. Inc.)

83

surface.'` Particulate matter passingthrough the corona is Eubjected to an in-tense bombardment of negative ions thatflow from the high-voltage electrode to thegrounded collecting surface. The particlesthereby become highly charged within afraction of a second and migrate towardthe grounded collecting surfaces. This at-traction is opposed by inertial and frictionforces.

After the particulate matter deposits onthe grounded collecting surface, adhesive,cohesive, and primary electrical forces mustbe sufficient to resist any gas stream actionand counter electrical forces that wouldcause reentrainment of the particulate mat-ter. Free flowing liquids are removed fromthe collecting surface by natural gravityforces. Successful removal of other particu-late matter depends on a complex interrela-tionship of particle size, density, and shapeand electrical, cohesive, adhesive, aerody-namic, and rapping forces. This particu-late matter is dislodged from the collectingsurfaces by mechanical means such as byvibrating with rappers or by flushing withliquids. The collected material falls to ahopper, from which it is removed.

4.5.3 Equipment DescriptionTwo major high-voltage electrostatic pre-

cipitator configurations are used: the flatsurface and tube types. In the first, par-ticles are collected on flat, parallel collect-ing surfaces spaced from 6 inches to 12inches apart with wire or rod dischargeelectrodes equidistant between the surfaces.In tube-type high-voltage electrostatic pre-cipitators, the grounded collecting surfacesare cylindrical instead of flat with the dis-charge electrode centered along the longi-tudinal axis. Figures 4-43 and 4-44 showtypical electrode and collecting surface lay-outs for both types of high-voltage electro-static precipitators. A complete precipita-tor consists of many of these units asshown in Figures 4-45 and 4-46.

44.3.1 Voltage Control and Electrical Equip-ment-1-Egh-voltage electrostatic precipita-

*The terms "collecting electrode" and "groundedcollecting surface" are often used synonymously.

84

tors operate with unidirectional current andwith voltages of from 30 to 100 peak kilo-volts. Transformers are used to providehigh-voltage current. Rectifiers convert thealternating current to unidirectional cur-rent. In addition, precipitators are usuallyequipped for automatic power control. Elec-trical rower energization and control equip-ment is usually furnished in the form of sev-eral packaged units complete with instru-mentation.

Transformers are usually oil cooled andare integrally connected to silicon rectifiers.The transformer single-phase output maybe rectified to either double-half-wave orfull-wave direct current. Earlier types ofhigh-voltage sets consisted of separatetransformers using either vacuum tube ormechanical rectifiers. Silicon rectifier con-version equipment is available for modern-izing existing vacuum tube or mechanicalrectifiers.

Figure 4-47 shows one type of transform-er-rectifier unit, and Figure 4-48 shows onetype of power control unit.

4.5.3.2 Discharge ElectrodesThe dischargeelectrodes, which are almost always ener-gized, provide the corona. Although roundwires about 1/8-inch in diameter are usu-ally used, discharge electrodes can betwisted rods, ribbons, barbed wire, andmany other configurations. Steel alloys arecommonly used; other materials includestainless steel, silver, Nichrome®, alumi-num, topper, Hastelloy®, lead-covered ironwire, and titanium alloy. Any conductingmaterial with the requisite tensile strengththat is of the proper configuration is afeasible discharge electrode. Figure 4-49shows some common discharge electrodeconfigurations.

4.5.3.3 Collecting SurfacesA variety offlat collecting surfaces is available. Theuse of smooth plates, with fins to strength-en them and to produce quiescent zones,has become common in recent years. Spe-cial shapes are designed primarily to pre-vent reentrainment of dust. Figure 4-49shows some types of collecting surfaces.Essentially all tubular collecting surfacesare standard pipe.

CHARGING FIELD HIGH-VOLTAGE DISCHARGE ELECTRODE ( )

CHARGED ( ) PARTICLES

s%k

PARTICLE PATH

COLLECTING BAFFLE

GROUNDED (4) COLLECTING SURFACE

DISCHARGE ELECTRODE TENSION WEIGHT

FIGURE 4-43. Schematic view of a flat surfacetype electrostatic precipitator.

fi

- -

....--...,

GASFLOW

ill

GROUNDEDCOLLECTING SURFACE

CHARGED PARTICLES

HIGH- VOLTAGEDISCHARGE ELECTRODE

(NEGATIVE - )

GROUNDED COLLECTING SURFACE

FIGURE 4-44. Schematic view of tubular surfacetype electrostatic precipitator.

85

SAFETY RAILING

HIGH VOLTAGE TRANSFORMER/RECTIFIER

RAPPER H. V. ELECTRODE

RAPPER - COLLECTING SURFACE

PENTHOUSE ENCLOSING INSULATORS AND GAS SEALS

ACCESS PANEL

INSULATOR

H. V. WIRL SUPPORT

H. V. DISCHARGE ELECTRODE

PERFORATED DISTRIBUTION BAFFLE

GROUNDED COLLECTING SURFACE

SUPPORT COLUMNS

QUICK OPENING DOOR(INSPECTION PASSAGE BETWEEN STAGES)

WIRE WEIGHTS

HOPPERS

FrcuRE 4-45. Cutaway view of a flat surface-type electrostatic precipitator.(Courtesy of UOP Air Correction Division)

HIGHVOLTAGECONDUCTOR

DIFFUSERVANES

GAS OUTLET

GAS INLET

INSULATOR COMPARTMENT

HIGH-VOLTAGE SYSTEMSUPPORT INSULATOR

ELECTRIC HEATER

WATER SPRAYS

DISCHARGE ELECTRODESUPPORT FRAME

WEIR PONDS

DISCHARGE ELECTRODES

TUBULAR COLLECTINGSURFACES

CASING

WEIGHTS

DISCHARGE SEAL

FIGURE 4-46. Cross-sectional view of irrigated tubular blast furmace precipitator.(Courtesy of Koppers Co. Inc.)

87

FIGURE 4-47. Typical double half wave silicone rec-tifier with twin output bushings.

4.5.3.4 Remoral of Collected ParticulateMatterCollected particulate matter mustbe dislodged from the collecting surfacesand discharge electrodes and moved fromthe electrostatic precipitator hopper to astorage area.

Liquid collected particulate matter flowsdown the collecting surfaces and dischargeelectrodes naturally and is pumped to stor-age.

Solid collected particulate matter is us-ually dislodged from collecting surfaces bypneumatic or electromagnetic vibrators or

88

rappers. At times, motor driven hammersare used for this purpose or sprays are usedto flush materials from collecting surfaces.Solid materials are transferred from thehopper to storage by air, vacuum, or screwconveyors. Swing valves, slide gates, or ro-tary vane-type valves are installed at thehopper outlet. Figures 4-50 and 4-51 showsome types of hopper valves and rappermechanisms.

4.5.4 iligliNoltage Electrostatic Precipitafor Equipment Design

Design of high-voltage electrostatic pre-cipitator equipment is a highly complex andspecialized field. It is therefore importantthat design decisions be made only by thosequalified by extensive knowledge and ex-perience.

The basic elements of design of electro-static precipitators involve both perform-ance requirements and physical require-ments. Voltage, electrical energy, gas ve-locity, flow distribution, sectionalization,collecting surface area, treatment time, num-ber and type of discharge electrodes, num-ber and type of collecting surfaces, collect-ing surface and discharge electrode spacingand number and type of rappers are someperformance requirement factors to consid-er. Layout, structure, materials handling,and construction material requirements aresome physical factors to consider.

Information on the design of high- ,oltageESP is reported by Ramsdell, White, andArchbold. 91-98

4.5.4.1 Conditioning SystemsConditioningsystems that change the properties of thegas stream or the particulate matter aresometimes installed ahead of the electro-static precipitator. The need for such asystem depends on the applicatiol. Condi-tioning may involve gas cooling, gas humid-ification, air dilution, or the injection ofagents such as sulfur trioxide and ammonia.

4.5.4.2 Voltage, Electrical Energy, and Sec-tionalization RequirementsVoltage, elec-trical energy, and sectionalization are inter-related. The design of the high-voltageelectrostatic precipitator should provide fora peak voltage sufficient for consistent op-

-- IIII--

A)

Flamm 4-48. Internal view of one type of rectifier control console showing component parts.(Courtesy of Koppers Co. Inc.)

89

SQUARE

CPZEL EXPANDED METAL

90

0

ROUND

ROD CURTAIN

e. COLLECTING PLATES

BARBED

D. DISCHARGE ELECTRODES

STAR

nava 4-40. Electrostatic precipitate.* collecting plates and discharge electrodes.

PUNCHEDRIBBON

eration of the unit within required perform-ance limits. The design should also providefor automatic power control and sufficientelectrical power to handle all load condi-tions. When necessary, the desigii shouldprovide for sectionalization so that voltagemay be adjusted t compensate for differentconditions in different sections of the elec-trostatic precipitator.

The peak voltage requirements of a high-voltage electrostatic precipitator depend onthe application and design, and usuallyrange from 30 to 103 kilovolts. Peak volt-age requirements depend largely on thespacing of electrodes and collecting sur-faces. The composition, pressure, and tem-perature of the gas stream and the concen-tration of particulate matter in the gasstream also influence peak voltage designrequirements.

For continuous high-efficiency perform-ance, sectionalization usually is required.Tl' power supply and controls for each pre-cipitator section are energized separatelyto prevent power fluctuations from spread-ing from section to section. The power con-trols regulate current, voltage, and spark-ing. The number of sections required de-pends on performance requirements and theapplication. For some applications spark-ing is not desirable. Where sparking is de-sirable, there is often an optimum sparkrate that will give the best performance.An example of this effect is shown in Fig-ure 4-62.'t

e. ROTARY VALVE

4.5.4.3 Gas Velocity, Treatment Time, ondFloiv DistributionGas velocities rangefrom 3 to 16 feet per second. Low lineargas velocities promote deposition and helpminimize re-entrainment of particulate mat-ter. The cross-sectional area of the electro-static precipitator determines the linear gasvelocity for a given gas volume. Longertreatment time promotes more effective dep-osition of particulate matter. The lengthof the treatment section of the electrostaticprecipitator determines the treatment timefor a given linear gas velocity.

Uniform flow distribution is an importantdesign factor. Perforated plates are installedat the inlet and sometimes at the outlet of theelectrostatic precipitator, and vanes are ofteninstalled in the inlet fold outlet ductwork todistribute the flow of the gas stream. Whenit is necessary to install bends or elbows nearthe inlet or outlet, fuming vanes are helpful.Experimental gas flow models are most usefulas an aid to flow distributor design.

4.5.4.4 Collecting Surfaces and DischargeElectrodesThe number, type, size, andspacing of collecting surfaces and dischargeelectrodes required is dependent on the ap-plication and desired performance. For agiven application, an increase in the totalcollecting surface area will usually improveperformance provided adequate corona poweris supplied.

4.5.4.5 Materials of ConstuctionChoice ofmaterials for shells, collecting surfaces, elec-

SWING VALVE

From 4 -IA Hopper direharge valve*. (a) Rotary vslre mkt (b) wing rah-e.

91

net=

4-5

2. E

lect

rost

atic

pre

cipi

tato

r ra

pper

mec

hani

sms.

(a)

Pne

umat

ic im

puls

e ra

pper

. (b)

Mag

netic

impu

lse

rapp

er. a

nd (

c) p

neum

atic

rec

ipro

-ca

ting

rapp

er.

(Cou

rtes

y of

Kop

pers

Co.

Inc

.)

SO 100

SPARKS PER MINUTE

FIGURE 4-52. Variation of precipitator efficiency withsparking rate for a given 11)-ash precipitator.

trodes, hoppers, and other surfaces is gov-erned by cost and serviceability. Corrosionand temperature resistance are the two mostimportant factors to consider. Steel con-struction is used wherever possible; how-ever, aluminum, lead, concrete, wood, ce-ramics, plastics, plastic coated metals, andmany other ..-naterials can be employed.

4.5.4.6 Collected Particulate Matter Han-dling SystemsElectrostatic precipitatorhopper walls should be sloped to dromotefree flow of collected material. When ma-terials stick or bridge in the hopper, vibra-tors or rappers should be attached to theoutside of the hopper walls at strategiclocations.

Hopper outlet valves should be designedto operate freely under all conditions. Thehopper discharge system should also be de-signed to minimize gas leakage into or outof the electrostatic precipitator to preventre-entrainment of the collected particulatematter.

4.5.4.7 Controls and InstrumentsUsefulcontrols and instruments are:

1. Individual electrical set controls andindicators.

2. Spark rate indicators.3. Rapping cycle, frequency, intensity,

and duration controls and indicators.4. Outlet opacity indicator.6. Line voltage indicators.

Recorders are useful for providing a per-mnient record of performance. Alarms areused to signal when control variables devi-

ate from normal and when control valves,gates, or conveyors fail to function properly.

4.5.4.8 LayoutAn electrostatic precipita-tor system should be designed to conservespace and to minimize costs. Other factorsto consider are provision for future addi-tions of equipment and the effect of the lay-out on gas flow distribution.

.5.5 Specifications and Guarantees

Little published information is availableon design criteria for electrostatic precipi-tators. It is therefore advisable for personswithout extensive knowledge of and ex-perience with the application of electro-static precipitators to rely on several dif-ferent vendors or consultants to furnishspecifications. Forms used by members ofthe Industrial Gas Cleaning Institute arehelpful for reporting and tabulating neces-sary information. These forms specify theinformation that the vendor needs to makea comprehensive proposal. This form in-cludes information on:

1. The purchasing company.2. The proposal.3. The application.4. Operating and design conditions.6. Properties of the particulate matter

and the gas stream.6. Inlet particulate matter loadings.7. Desired outlet loadings.8. Desired efficiency.

When the purchaser lacks sufficient in-formation to complete the form, the vendorcan often draw on his knowledge and experi-ence to supply the missing information orcan advise the purchaser on further action.The purchaser may also retain consultantsfor guidance.

Industrial Gas Cleaning Institute publi-cation No. EP-4 is useful for bid evaluation.Major sections of this form relate to:

1. Operating and performance data.2. Precipitator arrangement.3. Collecting system.4. Electrical systems.6. Other auxiliary equipment and soy-ices.

The purchaser should select specificationsfrom the information submitted by the sev-

93

eral vendors. Any differences in equipmentor services proposals should be reconciledby consultation with the vendors or otherexperts. The specifications selected shouldbe used to solicit final bids.

The purchase agreement should include aperformance guarantee (when desirable),conditions for measuring performance, andspecifications. Information that may be usedfor guidance in the preparation of purchaseagreements is published by the IndustrialGas Cleaning Institute."-t"

.4.5.6 Maintaining Collection Efficiency

A well designed precipitator properlymaintained and operated within design lim-its will perform consistently at or abovedesign efficiencies throughout its service-able life.

Loss of efficiency is commonly caused byoverloading, process changes, or inadequatemaintenance. Increasing output or processgas flows without adding precipitator sec-tions usually reduces electrostatic precipita-tor efficiency. Changes in raw materials,products, fuels, tied gas stream conditionscan also lead to poor i..)rformance. If thesefactors are anticipated in the original de-sign, lass of efficiency can often be avoided.

It is not always possible to anticipatechanges in the properties of particulate mat-ter and the gas stream. It is therefore im-portant that collector performance be mon-itored frequently by sampling the outlet gasstream. When inspection and maintenancefail to bring performance to within designlimits and overloading is not a factor, thecause of poor performance is usually trace-able to changes in properties of the particu-late matter or the gas stream. Should thisoccur, consultation with the manufacturerof the equipment or ss th other experts is inof der.

-1.5.7 improlcmen; of Collection EfficiencyProcess changes or changes in air pollu-

tion control requirements may make it nec-essary to improse the efficiency of an elec-trostatic pv.eptator. When no provisionhas been made fur future additions, it maybe less c--ety t) scrap the older unit andto katall a modern, more efficient unit.

94

.10

If provision has been made originally forlayout and installation of additional unitsto increase capacity, the changes may bemade at nominal cost.

Before action is taken to improve effi-ciency, all of the elements of design men-tioned in Section 4.6.1 should be consid-ered and compared with process require-ments. The modifications required will de-pend on the degree of improvement requiredand the application.

When process conditions have changed,changing the voltage or power supply ofthe unit may improve the performance.Increasing the number of high-tension bussections may at times improve performance,The installation of automatic power controlsalone seldom results in significant improve-ment; however, use of this technique inconjunction with other techniques such asincreased sectionalization is often effective.

Installing additional high-voltage electro-static precipitator sections is the most com-mon technique for improving collection effi-ciency. At times efficiency may be improvedsufficiently by distributing the flow moreunit.,rmly within the unit or in the duct-work leading to the unit. In exceptionalcases, modification of material handling sys-tells may bring about the necessary im-rovement.

Changing the temperature of the gasstream or injecting of ler materials intothe va:, stream may improve efficien-cy. 1^2 Whenever foreign materials areinjected the air pollution aspects of thesematerials should be considered.

4.5.8 Typical Applicationhigh-seltage electrostatic precipitators

have been used successfully to collect a widevariety of solid and liquid particles. Vari-ous applications for high Pottage electro-static precipitators are included in Table4-2.

4.5.8.1 Parr ritrd Coal-Firrd Poorrr PlantsThe arrangement in Figure 1-63 depicts artiverized coal unit. Typical of older systems,the mechanical precleaner (multiple cyclone)and the electrostatic precipitator are locateddownstream of the air heater. Gases range in

STACK

COALPULVERIZER

PLATETYPEESP2S0-)00-FGAS

mECHArICALCOLLECTOR

GASFLOW --

.IrkaAMR AVILT -STEEL SUPPORT LEVEL

FDFAN

meiASH CONVEYORffimI.O.FAN

COALSTORAGE

AIRNEATER

SOO /OD FGAS

POlLER

HOTAIR

ROOF LEVEL

SASE LEVEL

1FIGt-tx. 443. Eteetrostatie preeipilatet installed after at heater in pover plant steam !tenet:ter system.

temperature from 220° to 350° F. The bestprecleaners seldom exceed 80 percent efficien-cy. Assuming an 80 percent cleanup, the elec-trostatic precipitator would have to collect 95percent of the remaining particulate matterto achieve an overall efficiency of 99 peg cent.When soot is blown, particulate matter con-centrations are well in excess of averageemission levels.

A recently installed collection system lo-cates the electrostatic precipitator before, in-stead of behind, the air heater on a largesteam generator. The collector is rated at99 percent efficiency and handles gases atfrom G00° to 700° F. In this temperaturerange resistivity of particles is favorable forcollection; particularly for fly ash gener-ated from low sulfur coals and residualfuel oil. Installations of this type musthandle greater volumes of gases and, there-fore, are more expensive. Long-term evalu-ations are necessary to compare the per-formance of this unit with cold-side electro-static precipitators of the same rating.

4.5.8.2 Infrarn Ird Serr Ininkiup OprcationsIligh-voltage electrostatic precipitators arefrequently used in integrated steel plants.A common application is the detailing ofcoke oven gas. Wet-type electrostatic pre-cipitators are used for final cleaning of blastfurnace gases. Exit loadings as low as 0.005grain per standard cubic foot have been re-ported for this application.'" Highvoltage electrostatic precipitators applied tosintering strands reportedly reduce partic-ulate emission concentre' ons to less than0.04 grain per standar( .bic foot. '01-1^1,

Precipitator equipment applied to oxygen-lanced open hearths, bask oxygen furnaces.and electric are furnaces reduces particulateemission levels to less than 0.05 grain perstandard cubic foot. '"' "4' ""'"'

4.5.8.1 Crnunt /r/drIsttyElectrostatic pre-cipitator system efficiencies in excess of98 percent have been reported for dry-proc-ess rotary cement kiln applications. 'Is Ef-ficiencies exceeding 99 percent have beenreported for electrostatic precipitator sys.(ems applied to wet - process rotary cementkilns. III

96

4.5.8.4 Kraft Pulp MillsThe electrostaticprecipitator is a common gas cleaning de-vice used on kraft mill recovery furnaces.A survey of 50 plants indicated that therated efficiency of electrostatic precipita-tors installed ranged from 90 to 98 per-cent."' In some applications efficienciesof at least 99 percent have been reported.Electrostatic precipitators have been ap-plied to emissions from kraft mill lime kilns.

3.5.8.5 Sulfuric AcidThe efficiency of elec-trostatic precipitators in removing acid mistfrom contact-type sulfuric acid manufac-turing processes ranges from 92 to 99.9percent.'"

.6 LOW.VOLTAGE ELECTROSTATICPRECIPITATORS

4.6.1 Introduction

The low-voltage, two-stage, electrostaticprecipitator is a device originally designed topurify air, and is used in conjunction withair-conditioning systems. Cleaning of incom-ing air at hospitals and industrial and com-mercial installations is also a major use forthe low-voltage precipitator, and it is some-times called an air-corslitioning precipitatoror electronic air (Merl:" As an industrialparticulate matter collector, the device isused for the control of finely divided liquidparticles discharged from such sources asmeat smokehouses. asphalt paper saturators.pipe coating machines. and high-speed grind-ing machines.

Low-voltage precipitators are limited al-most entirely to the collection of liquid par-tides, which will drain readily from collectorplates. Two-stage precipitators cannot con-trol solid or sticky materials, and become in-effective if concentrations exceed 0.4 grainper standard cubic foot.

There is a limited number of ways of re-m% ing collected materials from the two-stage precipitator. This limitation causes theprimary use of the equipment to be restrictel.to systems with low grain loadings in whichthe collector plates need to be cleared onlyat infrequent intervals. This has been a de-torrent to widespread use of two-stage pre-cipitators in air pollution control. Also, elec-

trostatic precipitators do not collect or re-move gases or vapors responsible for ob-jectionable odors and eye irritation.

4.6.2 Major Components of Low-VoltageEleetrostatie Precipitators

The feature of the low-voltage precipitator(Figure .1- 51 ) that distinguishes it from thehigh-voltage electrostatic precipitator is theseparate ionizing zone located ahead of thecollection plates.':' The ionizing stage con-sists of It series of fine (0.007-inch diameter)positively charged wires equally spaced atdistances of from 1 to 2 inches from parallelgrounded tubes or rods. A corona dischargebetween each wire and a corresponding tubecharges the particles suspended in the airflowing through the ionizer. The direct-cur-rent potential applied to the wires amountsto 12 or 13 kilovolts. Positive polarity is reg-ularly used to minimize the formation ofozone.

The second stage consists of parallel metalplates usually !as than an inch apart. Insome designs, alternate plates are chargedpositively and negatively, each to a poten-tial of 6 or 61/2 kilovolts direct current, sothat the potential difference between adja-cent plates is 12 or 13 kilovolts.

In other cases, plates are alternatelyiliarged to a positive potential of 0 to 13ltilovolts and grounded. (The lower voltagesare used with closely spaced plates.) Thisarrangement is shown in Figure 4 -51. Theillustration shows particles entering at theleft, receiving a positive charge in the ion-izer, and being collected at the negativeplates in the second stage. Liquids drain bygravity to a pan located beneath the plates.Rapping or shaking is not employed, pri-marily because of the close spacing of plates.

The package unit shown in Figure 4-Mis used to collect oil mist from grinding ma-chines.'" Oil droplets agglomerate on theplates and drain to the bottom. Because solidsor viscous liquids will not drain freely. sys-tems removing such materials have to beshut down occasionally for cleaning of theplates to prevent arcing.

Semi: scous materials can be collected bythe low-1 ()Rage precipitator if an adequatewashing system is provided. The frequency

1

of washing will depend on the inlet loadingand the characteristics of the collected par-tictdate matter.

4.6,3 Auxiliary Equipment

Pretreatment of particles may be requiredto improve their electrical properties beforethey enter the precipitator. The systemshown in Figure .1-56 includes a low-pies.sure scrubber, mist eliminator, and temper-ing coil to control temperature and hu-midity. Removal of large particles by thescrubber allows longer operating periodswithout shutdown for cleaning of the elec-trostatic precipitator. Mist eliminators re-move water droplets and prevent excessivesparkover. Heating coils allow flexibility insetting optimum conditions. For many ma-terials, a relative humidity greater than 50percent in the gas stream is beneficial.

1.6.1 Design Parameters

When a low-voltage electrostatic precipi-tator is used in conjunction with air condi-tioning, velocities range between 5 and 10feet per second (fps). However, for pollu-tion control purposes, where the particulateloadings are much higher, the superficial gasvelocity through the plate collector sectionshould not exceed 1.7 fps. The relationshipbetween air velocity and collection efficiencyis illustrated by the Penney equation whichassumes streamline flow. The Penney (1937)equation for two-stage precipitation is:

Fvd

where:F = efficiency expressed as a decimal.w= drift velocity, feet per second.L = = collector length, feet.v =gas velocity through collector, feet

per second.d , distance between collector plates.

feet.

The upper limit for streamline flow throughthese t' o-stage nrecipitators is 600 feet perminute (fpm). Mechanical irregularities inunits now manufactured may reduce this up-per limit.

The effect of gas velocity on collection ef-ficiency for several industrial operations is

97

IONIZERSTAGE

DUSTPARTICL EPATH

: (5 ,(O-hi t-- -------,,:-

GAS °. 141-- (4/FLOW--on. 4 : I'M

I

.01Is) ", 1,

:Iii (4)

DUST

FIELDRECEIVE1'ELECTRODE

EMITTER WIRE (41

OASFLOW

98

to

DUST

(4)

DUSTPATH

0

COLLECTORSTAGE

()

1st STAGEEMITTER WIRES ANC.ELECTROSTATIC FIELD10,00042,000 VOLTS

)

2nd STAGEEMITTER PLATES (4)6,000.8,000 VOLTS

GROUNDEDCOLLECTOR PLATES (.)

EMITTER PLATE6,000.4,000 VOLTS (41

FIELD RECEIVERELECTRODES (.)

r/GlltK 4 '7,1. Operating principle of two slag* electrostatic precipitator.

GROUNDEDCOLLECTOR PLATES (

AIR

OUT

MOTOR

AIR &OIL MIST

IN !",'INLET

MANGE

FAN

COLLECTOR

CELL

IONIZER

FILTER

cm OMITDAMPER 10_1

PACKR Oft)

01 OUT

.1\FILTER

DRA AttINO *4 BOTTOMOr WAN PM

rictits 4-44. Two-stage precipitator used to control ad mist tram mac)lnings operations,(Cotertery of Wertioegkomte

Electric Corporation)

MISTELIMINATOR

PERFORATED_PL ATE

0I

CLEANGAS IN-FLOW

DIRTYGAS

FLOWLOW

PRESSURESCRUBBER TEMPERING

COIL IONIZERSTAGE COL'.ECTOR

STAGE

COLLECTEDOILS OUT

FIGt RE 4-56. Two-stage electrostatic precipitator with auxiliary scrubber, mist elimitAtor, tempering coil, andgas distribution plate (top view).

100

90

80

70

60

50

10

30

20

10

A.

B.C. 0,

B

I I I

SMOKEHOUSES, EXTRAPOLATED WITH PENNEY EQUATION (OPERATING TEST DATAFOLLOW CLOSELY/.ASPHALT SATURATOR, OPERATING TEST DATA.AIR CONDITIONING, MANUFACTURERS RECOMMENDATION.

1.5 2 3

GAS VELOCITY, ft/set

Fici wr: 4 57. Efficiency of two-stage precipitator as function of velocity for sevvral

4

I I IS 6 7

shown in Figure 1 57. Efficiencies of 80 per-cent and greater are shown for the collec-tion of oil mist at asphalt paper saturatorsand for air conditioning applications. Col-lection efficiencies ranging from 60 to 80percent are possible for meat smokehousesat a velocity of 1.5 fps. For smokehouses.collection decreases rapidly at higher veloci-

100

in.t istrial operations.

ties. Test data for typical installations areshown in Table 4 -7.

The practical voltage limit for low-volt-age precipitators is 18 kilovolts. Most unitsoperate at 10 to 13 kilovolts. Current flowunder these conditions is small (4 to 10 milli-amperes). The collecting plates Pre usuallyenergized at 5.5 to 6.5 kilovolts. but poten-

Table 4-7.INDUSTRIAL OPERATION OF TWO-STAGE PRECIPITATORS'

Contaminantsource

Contaminant1)Te

Ionizingvoltage

Tool grinding. .

Meat smokehouse.

Meat smokehouse.

Deep fat cooking..

Asphalt saturator(roofing paper.

Muller-type mixer.

Oil aerosol.Wood smoke,

vaporized fats.Wood smoke,

vaporized fats.Bacon fat aerosol...

13,00013,00:

10,000

13,000

Oil aerosol 12,000

Phenol-formal-dehyde resin.

13.000

Numberof ionizer

banksCollectorvoltage

Efficiencyvt percent

Velocity,fpm

Inletconcen-trationgr/scf

1 6,500 90 3332 6,00 90 60 0.103

1 5,00) 50 1.181

2 6,506 175 percentopacity

reduction)

68

1 6,000 145 0.384

1 6,500 87 75 0.049

(Ws tip to 13 kilovolts ,,1L possible. Actualcurrent flow is small because no corona ex-ists between the plates.

The degree of ionization may be increasedby increasing the number of ionizing elec-trodes. either by decreasing spacing or byinstalling a second set of ionizing wires inseries. Because decreased spacing requiresreduced voltage to prevent sparkover, thereappears to be an advantage in the series ar-rangement. Decreased spacing. however.lowers first cost and space requirements.

Low-voltage precipitators of :,tandard de-sign for capacities up to 20.000 cfm are sup-plied by manufacturers in preassembledunits requiring only external wiring and ductconnections. The installed weight of the pre-cipitator is approximately 80 pounds petsquare foot of cross-sectional area measuredperpendicular to the gas flow. These stand-ard units are usually sized so that the airflow for air pollution applications is about100 fpm.

4.6.. Materials of Construction

The standard material used in the con-struction of low-voltage precipitator (*fleefor cells is aluminum. The precipitator holm-ing is usuilly made of galvanized steel andframes are of aluminum. Where washing isto be frequent and even mildly corrosive con-ditions exist ionizer wires should be madeof stainless steel.

Soo

1.6.6 Typical Applications of Low-VoltageElectrostatic Precipitators

Applications of low-voltage precipitatorsto air pollution control have developed slowlysince 1937 when the first installation wassuccessfully used to collect ceramic over-spray from pottery glazing operations. Otherapplications have been the collection of oilmist from high-speed grinding machines andthe cleaning of gases from deep fat fryers,asphalt saturators. rubber curing oven, a dcarpet mill dryers. See Table 4-7 for oper-ational data...6.6.1 Machining Op raticusIligh speedgrinding machines generate mist from cut-ting oils, which must be vented from theworking area. Package units of the typeshown in Figure 4-65 are used to collet themist. A filter is provided ahead of the pre-cipitator to remove metal chips and anyother large particles. Concentrations of solidsand tars are usually low enough to be flushedfrom the plates with the collected oil drop-lets.

1.6.6.1 .lspholt SaturatorsIn thA manufac-ture of roofing paper, low-voltage electro-static precipitators are used to remove thesteam-distilled organic materials from hotliquid asphalt. Moisture evolved from thepaper carries oil from the process. Oils thatare collected flow readily from the plates ofthe electrostatic precipitator; only occasionalcleaning is required.

101

4.6.6.3 Meat Smokehouses Smokehouses areused by meat packing houses to cook andsmoke a variety of products. During thecooking cycle, exhaust products are reason-ably innocuous and exhaust gases can be dis-charged directly to the atmosphere. Smokegenerated from hardwood sawdust containsliquid aerosols, most of which are partiallyoxidized organics. In addition to aerosols,odorous, eye-irritating gases and vapors aredischarged in exhaust products.

Two-stage precipitators have been usedwith limited success to control visible aero-sols from smokehouses. All such operationsuse the design of Figure 4-56 with a scrub-ber, mist eliminator, and tempering coil.Under optimum operation, these units havereduced visible emissions to about 10 per-cent onacity. Maintenance is a problem, how-eve; and the exhaust gases have a strongodor and a lachrymose character.

The collected particles are principAy tarsand gums. When the unit is warm (; 20 to180° F), at least some of these tars drainfrom the plates. When the plates are notcleaned regularly, arcing occurs in the col-lector section, particularly near the loweredges of the plates.

4.6.6.4 Other Applications Two -stage pre-cipitators offer the promise of a low-costcontrol device for such operations as rubbercuring and carpet mill drying, where oilmists are generated. Conceivably, these de-vices can be used wherever the liquid sepa-rates easily from the plates and whereverother considerations such as odors and eyeirritants are not a problem.

4.6.7 Air DistributionProper air distribution through the pre-

cipitator is essential for efficient collection.PrecipitatorP are usually installed with hori-zontal air flow and frequently in positionsrequiring abrupt changes in gas flow pre-ceding the unit. Installations of this typecan result in turbulent and uneven flow withhigh local velocities, leading to low overallefficiencies.

Where a straight section of at least 8 ductdiameters is not available ahead of the pre-cipitator, mechanical means for balancing

102

the air flow must be used. Several types ofdistribution baffles and turning vanes havebeen devised. The most effective device hasbeen found to be one or more perforatedsheet metal plates fully covering the crosssection of the plenum preceding the ionizers.The optimum open area for the plate is about40 percent of the cross-section.

4.6.8 Maintenance

To assure optimum performance, the in-ternal parts of the precipitator must be keptclean enough to prevent arcing. In addition,voltagcs have to be held within properranges, and plate and wire spacings have tobe maintained within reasonably small tol-erances.

The frequency of internal washing will de-pend on the application. High particulateloadings in the gas stn.. ;Ili and sticky ma-terials present the greatest problems. On theother hand, two-stage precipitators can beoperated indefinitely where relatively clean,free-flowing oils are collected.

4.7 FABRIC FILTRATION

.1.7.1 introduction

One of the oldest and most positive meth-ods for removing solid particulate contami-nants from gas streams is by filtrationthrough fabric media.'1" The fabric filter iscapable of providing a high collection effi-ciency for particles as small as 0.5 micronand will remove a substantial quantity ofparticles as small as 0.01 micron."'

With a fabric filter, the dust-bearing gasis passed through a fabric in such a mannerthat dust particles are retained on the up-stream or dirty-gas side of the fabric whilethe gas passes through the fabric to thedownstream or clean-gas side. Dust is re-moved from the fabric by gravity and/ormechanical means.' The fabric filters orbags are usually tubular or flat.

The structure in which the bags hang isknown as a baghouse. The number of bagsmay vary from one to several thousand. Thebaghouse may have one compartment ormany so that one may be cleaned while oth-er. are still in service. Figure 4-58 illustratesone type of baghouse.

CLEAN AIROUTLET

DIRTY AIRINLET

CLEAN AIRSIDE

COLLECTIONHOPPER

FIGURE 4-58, Typical simple fabric filter baghousa design.

103

4.7.1.1 Range of ApplicationApproximate-ly 80 percent of all manufacturing plantscontain operations that produce dust andparticles of such a small size that use of ahighly efficient collection device such as abaghouse is desirable.'" In many cases, afabric collector is an integral component ofthe plant operation. For example, filters areused to collect metal oxides, carbon bl-and dehydrated milk, and to recover reusablematerials such as nonferrous grindingdusts.'-"

In other casei, fabric collectors are usedto reduce equipment maintenance, to im-prove product quality, to filter ventilationair entering a clean room, to prevent physicaldamage to the plant or equipment, and us-ually to collect mists, fumes or particulatematter that contribute to atmospheric pol-lution.,"

The initial selection of gas cleaning equip-ment for a given plant frequently is madeon the basis of past performance of theequipment. However, in making a choice, theability of the equipment to continue satis-factory operation under anticipated condi-tions must also ba considered. In 'hort, de-sign collection efficiency is not the sole cri-terion of performance. The ability of theequipment to continue high collection effi-ciency throughout its lifetime is also im-portant. Other parameters considered in theselection are the costs of purchase, oper-ation, and maintenance (detailed in Section6), as well as a variety of technical factors(listed in Section 4.7.4).

4.7.2 Mechanisms of Fabric FiltrationThe particulate matter is removed from

the air or gas stream by impinging on oradhering to the fibers.12T, 12$ The filter fibersare usually woven with relatively large openspaces, sometimes 100 microns or larger.The filtering process is not simple fabricsieving, as can be seen by the fact that highcollection efficiency for dust particles 1 mi-cron or less in diameter has been achieved.Small particles are initially captured and re-tained on the fiber of the fabric by directinterception, inertial impaction, diffusion,electrostatic attraction, and gravitationalsettling. Once a mat or cake of dust Is ac-

104

cumulated, further collection is accomplishedby mat or cake sieving as well as the abovemechanisms. Periodically the accumulateddust is removed, but some residual dust re-mains and serves as an aid to further filter-ing.

4.7.2.1 Direct InterceptionAir flow in fab-ric filtration is usually laminar.," Direct in-terception occurs whenever the fluid stream-line, along which a particle approaches a filterelement, passes within a distance from theelement equal to or less than one half theparticle diameter. If the particle has a verysmall mass it will not deviate from thestreamline as the streamline curves aroundthe obstacle, but because of van der Waalforces it will be attracted to and adhere tothe obstacle if the streamline passes suffi-ciently close to the obstaele.,3" (See path Ain Figure 4-59 for illustration.)

C ELECTROSTATIC ATTRACTION

A DIRECTINTERCEPTION

IP

B INERTIAL IMPACTION

Eternal 4-59. Streamlines and particle trajectoriesapproaching filter elements. (I), represents the fil-ter element diameter; 1),, the diameter of the par-ticles; V. is the velocity of the gas stream.)

4.7.2.2 Inertial ImpactionInertial impac-tion occurs when the mass of the particleis so great that it is unable to follow thestreamline rapidly curving around the ob-stacle and continues along a path of lesscurvatlire,"" so that the particle comes closerto the filter element than it would have .:0M13if it had approached along the streamline.Collision occurs because of this inertia effecteven when flow line interception would nottake place. (See path B in Figure 4-59). Im-paction is not a significant factor in collect-

ing particles of 1 micron diameter or less.Impaction is considered significant for thecollection of particles of two microns diam-eter and becomes the predominant factor asparticle size increases."'

4.7.2.3 DiffusionFor particles ranging insize from less than 0.01 to 0.05 micron di-ameter, diffusion is the predominaat mecha-nism of deposition. Such small particles donot follow the streamline because collisionwith gas molecules occurs, resulting in a ran-dom Brownian motion that increases thechance of contact between the particles andthe collection surfaces. A concentration gra-dient is established after the collection of afew particles, and acts as a driving force toincrease the rate of deposition. Lower airvelocity increases efficiency by increasing thetime available for collision and herefore thechance of contacting a collecting surface."'

4.7.2.4 Electrostatic AttractionElectrostat-ic precipitation will result from electrostaticforces drawing particles and filter elementtogether whenever either or both possess astatic charge. (See path C in Figure 4-59.)These forces may be either direct, when bothparticle and filter are charged; or induced,when only one of them is charged. Suchcharges are usually not present unless de-liberately introduced during the manufac-ture of the fiber. Electrostatics assists filtra-tion by providing an attraction between thedust and fabric, but it also affects particleagglomeration, fabric cleanability, and col-i"etion efficiency. A triboelectrie series offilter fabrics may be useful in selecting fab-ric with desirable electrostatic properties."'

4.7.2.5 Gravitational SettlingSettling ofparticles by gravity onto the filter surfacemay zesult from particle weight as the par-ticle passes through the filter. A simplemethod of judging the usefulness of a mecha-nism, based on particle size, is shown inTable 4-8.'"

4.7.3 Filter Resistance

Two forms of resistance, clean cloth re-sistance and dust mat resistance, affect thedesign of baghouses containing fabric filters.4.7.3.1 Clean Cloth ResistanceThe resist-

Table 44.--CONTROL MECHANISM FORPARTICLE SIZE COLLECTION'

DiameterPrimary collection mechanism of particle,

mIcrorl

Direct interception >1Impingement >1Diffusion 0.001 to 0.6Electrostatic 0.01 to 6Gravity >1

ante to air flow offered by clean filter clothis determined by the fiber of the cloth andthe manner in which the fibers are woventogether. A tight weave offers more resist-ance than a loose weave at the same airflow rate and, because the air flow is laminar,resistance varies directly with air flow. Oneof the characteristics of filter fabrics fre-quently specified is the American Societyfor Testing and Maeda Is (ASTM) perme-ability, which expresses the air volume incubic feet per minute passing through asquare foot of clean new cloth with a pres-sure differential of 0.50 inch water gauge.The usual range of values is from 10 to 110cfm per square foot."' With normal designconditions, the resistance of tY e clean clothdoes not exceed 0.10 inch of water gauge andis often less. The average flow rate in usefor an operating cloth is 1,5 to 3.0 cubic feetper minute per square foot of woven cloth.This is known as the air-to-cloth ratio orthe filtering velocity in feet per minute.",4.7.3.2 Dust Mat Resistance- -The pressuredrop of the dust mat at tha end of anyelapsed time is related to the concentrationof dust in the gas stream, the mass densityof the gas, and the face velocity of the gasthrough the fabric by the equation!

Gpgv't{op,) wxe =Kt

where:

(Apt) ,,,,, = pressure drop of the dust mat,inches of water

t =elapsed time, secondsG,----dust concentration in gas stream,

lb/ft'p mass density of gas, slugs/ft'g=--- acceleration of gravity, ft/sec'

105

v =face velocity of gas through the fab-ric, ft/sec

K = resistance coefficientC = dimensional constant

The values of K, the resistance coefficientmodified to include a factor for conversionof dust cake thickness to mass with constantviscosity, must be determined experimen-tally. C is a dimensional constant adjusted asrequired for the actual units used.'", 1"

K values are usually determined by meansof a scale model unit either in the laboratoryor in the field. Care must be exercised in ap-plying such results to a full-scale unit.'" Ifa vertical bag is used, elutriation of particlesmay,occur so that the true value of K varieswith time and position on the bag." Themeasured value of K is an average value thatmay not be the same when the scale or theconfiguration is changed. This is borne outby failure of some full-scale units to func-tion as anticipated on the basis of pilotstudies.

Table 4-9 gives K values for a numberof dusts,'" These data were obtained by lab-oratory experiments using an air flow of 2cubic feet per minute through 0.2 squarefoot of cloth area (equivalent to a filteringvelocity of 10 ft/min). The tests were termi-

nated at a maximum pressure differential of8 inches of water column.

Investigators have found that K varies asa power function of the filter velocity,"1 andvelocities greater than 2.3 ft. /min, seriouslyaffect the K value of the fly ash beingstudied."' These recent studies indicate thatK values listed in Table 4-9 should be usedonly for erAinates. Further research isneeded to definif more precisely the factorsaffecting the resistance coefficients of filtercakes. The values in Table 4-9 may be usedwhen such limitations are considered.

The pressure drop across the collected dustincreases uniformly with time, indicating alinear relationship between resistance andthe thickness of the accumulated dust mat.The data clearly show a treed of increasingresistance with decreasing particle size. In afull-scale baghouse, particularly if relativelylong vertical bags are used, a substantialamount of elutriation can be expected.'" Thedust-laden gas usually enters the filter bagat the bottom and travels upward. As thegas filters through the cloth, its upward ve-locity decreases so that only very fir', dustremains airborne to in deposited on ale up-per portion of the bag. Because the actualpressure loss through the bag must be the

Table 4-9.FILTER RESISTANCE COEFFICIENTS (K) FOR INDUSTRIAL DUSTS ON WOVEN FABRICFILTERS'

Filter resistance coefficients (K) for particle size smalle thanDusts

LO mesh b. 140 mesh b. 376 mesh b'd 90 pc 45 p 20 p 2p

Granite 1.58 2.20 19.8

Foundry 0.62 1.68 3.78

Gypsum 6.30 18.9

Feldspar 6.30 27.3

Stone 0.96 6.30

Lampblack 47.2

Zinc oxide 15.7Wood 6.30

Resin (cold) 0.62 25.2

Oats 1.58 9.60 11.0

Corn 0.62 1.58 3.78 8.80

KmInchex water gauge per pound ot dust per square toot per toot per minute ot filtering velocits.b U.S. standard sieve.

Coarse, smaller than 20 mesh or 140 mesh.Medium, smaller than 350 mesh, 90 p or 46 p.Theoretical size of silica; no correction made for materials having different densities.Fine, smaller than 20 a or 2 p.Flocculated material, not dispersed, size actually larger.

106

'

same through all areas, the volume and fil-tering velocity through some portions of thebag reach high values. Investigators "9found that local filtering velocities vary bya factor of 4 or more throughout a singlefilter bag. This, in turn, may lead to collapseor puncture of the fiber cake."9 Punctures(small holes in the dust mat) are usuallyself-repairing because the increased air flowthrough the small area of low resistancebrings more dust with it. Collapse of the fil-ter cake, on the other hand, is a shift in cakestructure to a more compacted condition witha greater resistance.

Collapse and puncture of the filter cakeare phenomena caused by excessive filter-ing velocities. Some dust is embedded and re-mains in the interstices of the cloth whenpuncture or collapse occurs so that normalcleaning does not completely remove thisdust. The embedded dust "blinds" or plugsthe fabric pores to such an extent that thefabric resistance becomes permanently ex-cessively high. Once begun, blinding be-comes worse rapidly. For example, transientlocal filtering velocities of 100 ft/minthrough areas of puncture were found when

BAG ECONOMICS

DUST AND GAS CHEMISTRY

OF DUST AND GAS STREAM --1

FABRIC SELECTION

DUST AND GAS TEMPERATURE

PHYSICAL CHARACTERISTICS

DUST PARTICLESIZE DISTRIBUTION

DESIRED COLLECTIONEFFICIENCY

GAS DEW POINT

GAS TEMPERATURE -----*

EQUIPMENTMAINTAINABILITY

ECONOMICS

the average filtering velocity was only 0.76ft/min.'"4.7.3.3 Effect of Resistance on DesignRe-sistance of the cloth filter and dust cake can-not be divorced from the total exhaust sys-tem. The operating characteristics of theexhaust blower and the duct resistance de-termine the ways in which increases in thebaghouse resistance affect the gas rate. Ifthe blower performance curve is steep, thegas flow rate may be reduced only slightlywhen the resistance of the filter bags changesmarkedly."' Some variation in resistance andair volume occurs normally in all baghouses.Proper design requires that the volume besufficient to capture the emissions at thesource when the Eystem resistance is maxi-mum and the gas volume minimum. To pre-vent blinding of fabric from partic!e im-paction, the filter ratio must not be excessiveimmediately after cleaning when the pres-sure drop is at a minimum and the air vol-ume at a maximum.

4.7. Equipment Description and DesignThe selection or desian of industrial Bust

collection equipment requires consideration

4 PROCESS FACTORS-.

AIR TO CLOTH___). FILTER SURFACERATIO AREA

PRECOOLFRS

L-PRECLEANERS

< VOLUME

4 4 INLET DUSTLOADING

PRODUCTRF.QUIREMENTS

FILTRATION CYCLF.4_BAG CLEANINGTECHNIQUE

ENERGY ECONOMICSBAGHOUSE_,FALRIC FILTERHOUSING -COLLECTOR DESIGN

DESIREDCOLL ECTIONEFFICIENCY

BAG ECONOMICS

PRODUCT HANDLING

Ficus,: 4-60. System analysis for fabric filter collector design.

107

of many factors. Figure 4-60 illustrates 'hecomplex nature of the final selection of afabric collector. Exhaust system design con-siderations include:

1. Determination of the minimum vol.Ime to be vented from the basicequipment.

2. Estimation of the maximum desir-able resistance.

3. Selection of the blower operatingpoint that will provide the minimumrequired volume at the maximum sys-tem resistance.

4. Estimation of the minimum resist-ance for the condition immediatelyafter a thorough cleaning of the fil-ter bags.

5. Determination of a second operatingpoint on the blower characteristiccurve for the clean bag condition.

6. Determination of the minimum fil-tering area required by the maximumfiltering velocity permissible for theparticular dust or fume being col-lected.

7. Rechecking of the calculations, withthe filtering area thus determined,to assure compatibility.

The rule of thumb for air-to-cloth ratiosfor conventional baghwises with woven-clott,, fabric filters is 1.5 to 3.0 cubic feetper minute per square foot for dusts and1.0 to 2.0 cubic feet per minute per squarefoot for fumes. The pressure drop for thewoven cloths normally ranges from 2 to 8inches of water. Physical characteristics ofbag fabrics tested in a pilot plant are givenin Table 4-10. Typical relationships between

Table 4-10.-PHYSICAL CHARACTERISTICS OFBAG FABRICS TESTED IN PILOT PLANT"'

Fabric

Material ASiliconized Siliconized Salconized

glass Dacron glass

Thread count 54X52 73X63 65X35Yarn Type:

Warp Filament Filament FilamentFill Filament Filament Staple

Weave Crowfoot Twill TwillWeight, oz/sq yd 9.36 4.69 9.00ASTM

permeability 15-20 25-36 60-80

108

Pe-

filter ratio and pressure drop across bags forthe three fabrics in Table 4-10 14° aro shownin Figure 4-61.11°

Typical filter ratios and dust conveyingvelocities for various dusts and fumes col-lected in woven z!oth bags are shown inTable 4-11.3"

47

C

vi 6

4

3

--I--I201 2 3 4 5

FILTEI4ING RATIO, 83/ft2 min

Roc A and C arc silIconited gloss fabrics, 8 Is asl!iconized Dacron faErIc.

FICUM 4-61. Presoure drop versus elter ratio forfabrics on 60minute clearing cycle for electricfurnace dust.

(Courtesy of the Journal of the Air PollutionControl Association)

Table 4-I1.-RECOMMENDED MAXIMUM FILTER-ING RATIOS AND DUST CONVEYING VELOCI-TIES FOR VARIOUS DUSTS AND FUMES. INCONVENTIONAL BAGHOUSES WITH WOVENFABRICS"'

Dust or fumes

Maxim4m Branchfiltering piperatios, velocity,cfm/ft' fpm

cloth area

AbrasivesAluminaAluminum oxideAsbestosBaking powder

3.02.262.02.75

215-2.50

430045004500

3500-400u4000-4500

Batch spouts for grains 3.0 4000Bauxite 2.6 4500Bronze powder 2.0 5000Brunswick clay 2.25 4000-4500Buffing wheel operations 3.0-3.25 3500-4000Carbon 2.0 4000-4600Cement crashing mid

grinding 1.6 4500Cement kiln

(wet process) 1.6 4000 -4500

Table 4-11 (Continued).-RECOMMENDED MAXI-MUM FILTERING RATIOS AND DUST CONVEY-ING VELOCITIES FOR VARIOUS DUSTS ANDmins IN CONVENTIONAL BAGHOUSESWITH WOVEN FABRICS'

Dust or fumes

Maximurnfilteringratios,cfm/tV

cloth area

BranchPipe

velocity,fpm

Ceramics 2.6 4000-4600Charcoal ... 2.25 4500Chocolate .... 2.25 4000Chrome ore 2.6 5000Clay 2.25 4000-4500Cleanser 2.25 4000Cocoa 2.25 4000Coke 2.26 4000-4500Conveying 2.6 4000Cork 3.0 3000 -350aCosmetics 2.0 4000Cotton 3.5 3500Feeds and grain 3.26 3500Feldspar 2.6 4030-4500Fertilizer (baggilg) 2.4 4000Fertilizer (cooler, dryer) 2,0 4600Flint 2.5 4600Flour 2.5 .-500Glass 2.5 4000-4500Granite 2.6 4500Graphite 2.0 4500Grinding and separating. 2.25 4000Gypsum 2.6 4000Iron ore 2.0 4500 -5000Iron oxide 2.0 4500Lampblack 2.0 4500Lead oxide k.25 4500Leather 3.6 3600Lime 2.0 4000Limestone 2.76 4500Manganese 2.25 5000Marble 3.0 4600Mica 2.25 4000Oyster shell . 3.0 4600Packing machines 2.75 4000Paint pigments 2.0 4000Paper 3.6 3500Plastics 2.6 4600Quartz 2.75 4500Rock 3.25 4500Sanding Machines 3.25 4500Silica 2.75 4600Soap 2.26 3500Soapstone 2.26 4000Starch 2.25 3600Sugar 2.25 4000Talc 2.25 4000Tobacco 3.5 3600Wood 3.5 3600

The rule of thumb for air-to-cloth ratiosfor reverse jet baghouses with felted ornapped woven fabric filters is 10 tc 16 cubicfeet per minute per square foot of cloth fordust, and 6 to 10 cubic feet per square footof cloth for fumes. Table 4-12 shows typicalfilter ratios of fabrics used for various dustsand fumes being collected in reverse jet bag-houses."'

A typical range of dust loading for wovenbag filters is from 0.1 to 10 grains per cubicfoot of gas. Higher concentrations of par-ticulate matter in some industries are re-moved by a pre-cleaning device, such as alow efficiency cyclone. Maximum dust load-ing reported for felted bag filters with re-verse jet or pulse jet cleaning is 80 grainsper cubic foot. Figure 4-62 presents dustloading versus filter ratio data for typicalproducts.'"

4.7.4.1 Baghouse Design-Many design con;siderations for handling waste gases from

4,1

z

. aal

60

cr

Lu 40

0)- 20

0

FILTERING RATIO, 113/112 - min

KEY

1. MAGNESIUM 6. KAOLINTRISILICATE 7. CEMENT OR

2. CARBON BLACK LIMESTONE DUST3. STARCH DUST 8. COAL DUST4, RESINOX 9. LEATHER BUFFING5. DIATOMACEOUS EARTH DUSTFOR NUMBERS 1 THROUGH 6, 99.94 99.99 PER-CENT PASSING 325 MESH. FOR NUMBERS 7 AND8, 95 PERCFNT PASSING 200 MESH. NUMBER 9,60MESH AVERAGE.From 4-62. Typical performance cf reverrejet

baghouses using felted fabrics on a variety ofdusts (dust load versus filtering ratio at 3.5 in.

.c. pressure drop).(Courtesy of the Industrial Chemist magazine)

109

Table 4-I2.RECOMMENDED MAXIMUM FILTER.ING RATIOS AND FABRIC FOR DUST ANDFUME COLLECTION IN REVERSEJET BAG.HOUSES"'

Niaterialor operation Fabric

Filteringratios,elm /ft'

Afurnin lir oxideBauxiteCarbon, calcined.... _

Carbon, green _ . _

Carbon, banburymixer.

Cement, raw. ......Cement, finiahedCement, millingChrome. (ferro)

crushing.Clay, green... _

Clay, vitrified.sIlicious.

Enamel, fp gcels in1 _

Fl ourGrain

GraphiteGypsum

Lead oxide fume____.

LimeLimestone (crushing).Metallurgical fumes._

MicaPaint pigmentsPhenolic molding

powders.Polyvinyl chloride

(PVC).Refractory brick

sizing (after firing).Sandblasting_

Silicon carbideSoap and detergent

powder.Soy beanStarchSugar

TalcTantalum fl uoride...TobaccoWood flourWood sawing

operations.Zinc, metallic.

110

r

Nappen cotton_ 11

Cotton lateen 10Napped cotton, 8

wool felt.Orlon felt.... 1

Wool felt 8

Cotton sateenCotton sateenCott on sateen. _Cot ton sateen._ _ _

Cotton sateenCotton sateen

Napped cotton_Cotton sateen._Wool felt,

cotton sateen.Wool feltCotton sateen,

orlon feli.Orlon felt,

wolf felt.Napped cottonCotton sateenOrlon felt,

wool felt.Napped cottonCotton sateenCotton sateen

Wool felt

Napped cotton

Napped cotton,wool felt.

Cotton sateenDacron telt,

orlon felt.Cotton sateenCotton sateenCotton sateen,

wool felt.Cotton sateenOrlon feltCotton sateenCotton sateenCctfrn sateen

Orlon felt,dacron felt.

Table 4-12 (Continaed).RECOMMENDED MAXI.MUM FILTERING RATIOS AND FABRIC FORDUST AND FUME COLLECTION IN REVERSE.JET BAGHOUSES"

Materialor operation "abrIc

Filteringratios,

elm/ft

Zinc oxide Orlon feltZirconium oxide Orlon felt 8

Decrease 1 cim/ft: if t"ist concentration is orparticle size is small.

9 various operations are the same regardless10 of the process involved. However, this is not

8 n,,icessarily true of baghouse typea most10 important design decisionwhich tanges10 from the open-pressure type to the closed,12 welded, fully insulated baghouse. Generally

the type of baghouse required is dictated bythe moisture in the wt.ste gas. The higherthe dew point, the greater the precautionthat must be taken to prevent condensationwhich can moisten the filter cake, plug thecloth, and corrode the housing and hoppers.Three designs, open pressure, closed pres-sure, and closed suction are used in fabric

to filter baghouse construction.", The cost ofto the open pressure system is the least of the10 three; that of the closed suction system is

the greatest.Open pressureAn open pressure bag-

house, in which the fan is located on the dirtygas side of the system, can be operated with

o open sides as long as protection from the12 weather is provided. Under some circum-

stances, a completely open baghouse is satis-6-8 factory,'" and allows hotter inlet gas tem-

peratures to be used because the cooling is9-11 better in an open baghouse. Better cooling

allows lower temperature filter media to be14 used with higher inlet gas temperatures than10 might otherwise be possible." In an open10 pressure system, the blower must handle the

entire dust load, which causes the blower towear substantially. Thus, maintenance costis higher than that for a blower on the cleangas side of a baghouse. Because air flowsfrom the inside of the filter bags, bag re-

1t placement is facilitated because a leaky bagis easier to locate. The open pressure unit is

121416

7

10

8

11

1010

12

11

6121012

DIRTYGASFROMFAN

CLEANED GAS) OUTLET

I'It

COR:'.UGA7EDHOUSING

OPEN4GRATING

OUTSIDE AIR

SIDE VIEW

FIGURE 4-63. Open pressure baghouse.

normally constructed with corrugated steelor asbestos cement walls. It may have opengratings at the cell plate level and may notrequire hopper insulation. Figures 4-63 and4-64 illustrate the open pressure bag -house.144, 143

Closed pressure - -A closed pressure bag-house is also constructed with the fan on thedirty gas side of the system, but the structureis closed.

The closed pressure unit is used for gaseswith high dew points and for toxic gases,that cannot be released at low elevations.Blower maintenance problems are identicalto those of the open pressure baghouse. As-bestos cement walls without insulation aresometimes used to construct closed pressurebaghouses. The floor of such a unit is closedand the hoppers are insulated. Figure 4-65and 4-66 illustrate the cl'v,ed pressure bag-hause.111, "3

Closed suctionA closed suction baghouseis one in which the fan is located on the cleangas side of the closed, all-welded, air tightstructure. The closed suction unit is used forgases with dew points between 165° F and180° F. The floor of such a unit is closed andthe structure walls and hopper are insulated,particularly for dew points in the upperrange. Blower maintenance is cheaper be-cause the blower is on the clean gas side of

the system. The inspection for holes in thebag is difficult. Figures 4-67 and 4-68 illus-trate the closed suction baghouse."4."'

Structural considerationsMetal used toconstruct the baghouse walls and hoppersmust be strong enough to withstand the pres-sure differ tials involved. A pressure differ-ential of 8 inches water column representsapproximately 42 pounds per square foot.The total air pressure !"Yor.ted on a side panelof a closed suction baghouse may be in excessof 2 ions.,"

Easy access to the baghouse Interior mustbe provided to change bags and to performmaintenance. The open pressure unit haseasy access to the cell plate at the bottom ofthe barhouse, even when the unit is operat-ing. However, at the bag top level, the hotand possibly toxic gases prevent bag chang-ing without taking the unit off stream. Toovercome this difficulty, many units are fur-nished with internal partitions between com-partments so an individual compartment canbe isolated. Thus, the remaining compart-ments continue to filter while the one re-moved from service is maintained.

Hoppers are sized to hold the collecteddust while or until it is removed for disposal.The slope of the sides of the hopper must besteep enough to permit the dust to slide orflow freely. The designer must also considerthe possibility of bridging. Continuous re-moval of dust will help to prevent bridgingof material, and will prevent operating diffi-culties with materials that become less fluidwith time.

4.7.4.2 Fabric Filter ShapeFilter shape isdependent on the use to which the filter willbe put. Two major bag shapes, the envelope(flat) and the tube, are used.

The envelope bag is illustrated in Figure4-69.143 Dust is coilected on the outside of thebat, which is prevented from collapsing bythe use of internal screens or frames. How-ever, the internal screen complicates bagchanging and the contact of the screen andfabric reduces cloth life. The envelope baghas the advantage of providing more filteringsurface per volume than the tubular bag be-cause of the close spacing of the envelopes.If the dust has a tendency to bridge, every

1111

1

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AIMMIrfil W

Fronts 1 -51. °pat pressure beet...nee 'Ana ttl-,owing installation scithont a separate doss+ tat twining.(Ceirrtesi e/ flee likteletrest C.rpotatist)

112

DIRTYGASFROMFAN

CLEANED nAsOUTLET

CORRUGATEDHOUSING

CLOSED

SIDE VIEW

FIGVRE 4 65. fluted pleasure baghouse.

other bag may be removed to prevent plug-ging.

The tubular bag, illustrated in Figure4 -70, is open at one end and closed at theother.'" Tubular bag design is more variedthan flat bag design. Multi-bag and bottom ortop entry uni-bag filters are in widespreaduse. Mr flow may be either from the outsideor inside.

A niriti-bag is a group of either three orsix tubular bags sewn together as shown inFigure 4-71.1" Multi-bag suspension is lim-ited to a top loop suspension. A disadvantageof the top loop suspension is the difficult ad-justment required occasionally because of themulti-bag dimensional instability.

The uni-bag is a single tubular bag. not at-tached to other bags, into which gag; mayenter from the top or bottom. Bottom entryallows gas to enter from the hopper sectionand flow upwards into the filtering area asshown in Figure 4-72.1"

Bottom entry allows pre-separation of thecoarse partici% in the hopper, and the fabrichandles the suspended dust. Gas flows dosnin a top entry unit into the filtering area asshown in Figure 4-73.'" The entire dust loadpasses through the entire tube of the topentry design before dust reaches the hopper.A cell plate ceiling, as well as a cell platefloor, increases the difficulty of adjusting topentry bags. The top entry baghouse creates a

dead gas pocket in the hopper than can be asource of trouble because of condensation ofwater vapor in moisture-laden gases.

The direction of gas flow in tubular bagscan be either inside out or outside in. If thedirection is outside then a frame is insertedin the bag to prevent the bag from collapsing.Collecting the dust en the outside of the bagrequires that the unit be inspected on thedirty gas side and increases the difficulty ofbag replacement. Also, shorter bag life is ex-perienced because of bag and frame contact.

4.7.4.4 Cloth Type --Two basic types of clothare used in fabric filters. They are wovencloth or "cake" filter media, and felted clothor "fiber" filter media."4.

Woven fabric acts as a support on which alayer of dust is deposited to form a micro-porous layer capable of removing additionalparticles by sledng and other basic filtrationmechanisms.'" Cake filtration is the mostimportant removal mechanism when new fil-ter cloth becomes thoroughly impregnatedwith dust. A wide variety of woven and feltedfabrics are used in fabric filters. Clean feltedfabrics are more efficient dust collectors thanclean woven fabrics, but woven materials arecapable of giving equal filtration efficiencyafter a dust layer accumulates on the surface.AVlieti PW woven fabric is placed in service,visible penetration of dust may occur untilthe cake builds up. This takes a period of afew hours to a few days for industrial appli-cations, depending oft the dust loading andthe nature of the particles. When dealingwith extremely low grain loadings and finedusts, fabrics may be preloated with asbestosfloats or similar materials to form an arti-ficial filter cake to prevent dust leakage.

Another method of reducing dust leakagein fabrics is based on the use of electrostatics.Electrostatic forces used in dust collectingmechanisms are explained in Section 4.7.2.4.Electrostatics not only assists filtration kproviding an attraction between the dust andfabric but also may affect particle agglomera-tion, fabric cleanability and collection effi-ciency.

Electrostatic charges are induced in bothfabrics and dusts by friction. The maximumcharge and the charge dissipation rate are

113

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DIRTYGASFROPROCESS

CLEAN GASTO FAN

CLOSEDALL WELDEDHOUSING

SIDE VIEW

Flom: 4-67. Closed suction liaghouse.

Fictwfi 4 -'44. Closed suction concrete bagbouso unit.(Coarfeity of lie Illet/obroter Corporntion)

measured for each fabric and dust. Fabricsare arranged in relation to each other in atriboelectric series)" Attempts to developsuch a series for dusts have not been success-ful.

Agglomeration of some charged dusts maybe aided by selection of a fabric with an op-pcite charge. For example, a negativelycharged dust would agglomerate with a posi-tively charged fabric.

TOP VIEW

SIDE VIEW

ViGt-an 4 69. TypivAl flat or envelope dust collec-tor bac.

TOP VIEW

SIDE VIEW

rIGI RF. 4 70. Tpical round or tubular dust col-lector hair.

Dust leakage through a fabric may be re-duced by maximizing the electrostatic differ-ential between dust and fabric, thus maxim-izing the electrostatic attraction forces. Leak-age may also be reduced by selecting a fabricwith a low dissipation of electrostatic charge.A fast dissipation of charge reduces tooquickly the electrostatic attraction betweenfabric and dust. When this occurs, fabricovercleaning during the cleaning cycle ispossible with no residual dust remaining onfabric to act as a precoat.

Electrostatic charging has been introducedin some bonded fiberglass fabrics used forair conditioning installation. However, until

115

I'I 1

I I !

'I

I tI I I I II I I SIDE VIEW

I 1 I

I I I I

t I

TOP VIEW

Floras: 4 -7r.4-71. Typical multitag dust collectionsystem.

INSIDE OU1FtL.TERING

r.

SIDE VIEW

Ftut-as 4-72. Bottom entry design uni-bag.

116

CI 0THCLEANINU BYREPRESSURINO

INSIDE OUTFALTERING

SIDE VIEW

Fiat RE 4-73. Top entry design uni.bag.

more information is available for large in-dustrial fabric filters, the relative import-ance of electrostatics in determining the bestfilter fabric for a specific installation cannotbe evaluated. Certainly, if one fabric does notv.ork effectively, other fabrics should betried, Both the physical characteristics andthe electrostat!c properties of the fabricsmay serve as guides.

Waren fabricsWoven fabric filters inconventional baghouses usually have air-to-cloth ratios of 1:1 to 5:1.1m "* Woven fabricpermeability can be varied, which, in turn,varies the operating air-to-cloth ratio. Per-nteabifity and air-to-cloth ratio have beezidiscussed in Section 4.7.8.1.

Woven fabric permeability or porosity isvaried by using different yarns, fabric count,cloth weights (expresed as ounces per squareyard), And *ye patterns. The three basicforms of yarn used for woven fabrics aremonofilament, multifilament, and spun-sta-pie.'" ktonofilament yarn is a synthetic fibermade in a single, continuous filament, Multi.filament yarn is made by twisting two ormore monofilamenta together. Spun-stapleyarn is made by twisting short lengths ofnatural or synthetic fiber into a continuousstrand. Warp is the yarn that runs length-wise in a cloth and fill (pick) is the yarnthat interlaces with warp yarn to form awoven fabric." The count of a fabric is thenumber of warp and fill yarns per squareinch in a woven fabric.

Another method for deo casing wovenfabric porosity is to weave cloth from nappedyarn or plied yarn. The napped yarn is madeby abrading the surface of the filament yarnto produce a fuzzy, fibrous condition.'" Theplied yarn is made by twisting lighter weightyarns together in a single, continuous strandof yarr."' For example, a fabric made from800 denier yarn (weight in grams of a singlecontinuous strand of yarn, 9000 meters long)may be made from plied yarn by using fourstrands of 200 denier yarn. These four 200denser strands of yarn may be twisted to-gether to give the plied strand of yarn whichmay be used to weave the 800 denier cloth.The weight of the cloth remains unchangedwhile its dust retentivity is improved.

The basic weaves usually used for fabricfilters are plain, twill, and sateen.'" Theseare illustrated in Figure 4-74. The plainweave has a simple "one up and one down"construction. This construction permits max-imum yarn interlacing per square inch, and,if woven tightly, allows high impermeability.If the count is lowered, this weave can be Asopen as desired. The plain weave is commonin certain cotton ducks and many syntheticfibers.'"

The twill weave is recognized by the sharpdiapaal "twill" line formed by the passageof a warp yarn over two or more fill or pickyarns with the interlacing advancing onepick with each warp. In equivalent construc-tion, twills have fewer interlacings than theplain weave and, hence, greater porosity, al-

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though this naturally depends on the count.Cotton and synthetic filter twills are com-monly used.'"

The sateen weave with even fewer nickinterlacings, spaced widely and regul ,rly,provides h smooth surface with increasedporosity. These (nllities make them particu-larly valuable in dust collection. Cotton fab-rics in this weave are commonly known assateens. Cotton sateen is probably more com-monly used than any other fabric in fabricfilters operated at ambient temperatures.

Dimensional stability is an important fac-tor in filter fabric. Colton and wool fabricsmust be preshrunk, and synthetics are usu-ally given a corresponding treatment knownas "heat-setting"."' This process contributesto a more even balance of warp and fillingyarn tension, controlr porosity, and virtuallyeliminates shrinkage. Dimensional stabilitymay be lost if the fabric is subjected to tem-peratures near that used in th,: original heat .setting process. Excessive temperatures inoperation can cause a shrinkage of 3 or 4percent. Shrinkage may cause a bag to pullloose from it3 connection to the floor pate orthe upper support structure.

Woven natural fabrics may be treated withflameproofing, moldproofing, thrinkproofing,and/or dust - releasing coatings, such as sili-cone to increase service life.'" Woven syn-thetic fibers are often treated with flame-proofing and dust releasing coatings..

Woven fabric bags are made from cotton,

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Frctas 4-74. Bark fabric weaves steed for woven filter bag&

(Ceitricrp el West Point Pepperell, IRdmsfri41 ribries nirishoo

117

wool, Dacron, Nylon, Orion, Nomex, polypro-pylene, Teflon, and fiberglass.

Fiberglass fabric bags are treated withsilicone, mixtures of silicone and colloidalgraphite, and Teflon lubricants to orovideprotection against abrasion and flex failurescaused by fiber-to. fiber rubbing.'" These lu-bricants are effective at temperatures offrom 100°F to 550°F.

Felled fabricsFelted fabrics serve as fil-ter media and are used in reverse jet andpulse jet baghouses with air-to-cloth ratiosof 5: 1 to 10:1,114 or ratios 5 to 0 times '"those woven fabric filters.

Felted bags are more expensive thanwoven hags. Wool is the only fiber that willproduce a true felt. However, synthetic fiberscan be needled to function as a feat filterfabric. Hence, felt is limited to wool and suchsynthetic fibers as Dacron, Nylon, Nomex,polypropylene, and Teflon. Cotton and fiber-glass fibers do not make felted fabrics.

Feted fabrics are complex, labyrinthinemasses of randomly oriented fine fibers. Therelative thickness provides the advantages ofmaximum dust impingement and changes ofdirection of flow to entrap small dust andfume particles Felted fabric filters operatewith extremely high collection efficiencies.'"

In some cases, felted bags do not functionwell in the collection of extreme6- fine fumesbecause the fine pat tides are embedded inthe felt and are very difficult to remove in thecleaning cycle. In general, felted bags arecleaned by high-pressure reverse jet arid jetpulse devices that operate at frequent inter-vals. In one unit, each felted bag is cleanedindividually by reverse air flow from a pres-sure blower and a burst of compressed airreleased when the bag has been expanded.'"

Principal considerations for proper selec-tion of the most economical felt fora particu-late process include,'"

1. Necessary characteristics of the fiberto meet chemical and thermal resist-ance needs.

2. Type of construction.3. Such physical properties of the felt

as density, breaking strength, elonga-tion, bursting strength, air permea-bility, and particle site retez.:ion.

118

4.7.4.4 Fabric Clcaning Fabric flexing andreverse air flow through the cloth are twomethods of cleaning collected particulatematter from fabric filters.

Fabric flexingManual shaking, mechani-cal shaking, and air shaking are three meth-ods of fabric flexing used in cleaning filters.Air shaking is further broken into four meth-ods: bubbling, jet pulsing, reverse airflexing and sonic vibration.

Manual shaking is used in baghouses ofabout 500 to 500 square feet of cloth. A rap istransmitted to the framework from whichthe filtering bags are suspended. Vibrationfrom the rap shakes the dust loose. Thoroughcleaning is rarely achieved because the shak-ing action is dependent on the operator'svigor.'" This method is the least expensiveand least desirable.

'Mechanical shaking (Figure 4-75) re-moves dust from woven fabrics in a mannersimil;r to that achieved by hand shaking arug.'" The shaker mechanism provides agentle but effective cleaning action on theLags without exerting undue stresses on thefabric.

The shaker design must allow for easy in-stallation, alignment, and maintenance.shaking is usually used for inside out filter-ing and is considered too vigorous for fiber-glass bags unless special provisions are madefor reducing the intensity of shaking.'"

IN9DE OUTFILTEPING

SIDE view

Pistil 1-T5 Measnical INakinir of bottom entry&sign airbag dist collector.

Mr shaking (Figure 4-76) is done byflowing air between rows of bags, indwhip-ping the bags to make a dancing, cleaningaction.'" Bags are overcleaned near the ori-fice or jet and undercleaned in blind areas outof the windhipping action. This methodrequires a minimum of hardware but is usu-ally too vigorous for fiberglass bags.'"

Air bubbling is done by releasing a travel-ing air 'nibble at the top of the bag duringthe cleaning cycle, as ;,!sown in Figure 4-77.The !rubble travels down the bag during re-prersuring and causes it to ripple, thus clean-

PRESSURE qLCWER

8881f88o8tom0008o0,fi1[88§11841

00%. TOP VIEW

MP JETSErik SHAKING

FiGltg 4-7E. Air shaking fluFtcollector hags.

UP IRAG

INSIDE OutFILICRING

JET

SIDE VIEW

1

Pict at 4-T7. Rabble cleaning et (last collector bags.

ing the bag by shaking. The compressed airrequirements are high and cleaning at higherair-to-cloth ratios has not been fully proven.This method is used for inside out filteringand sometimes for fiberglass bags."'

The jet pu'AQ method employs a jet actionof compressed air through a venturi sectionat the top of the bag (Figure 4-78). Smallerdinmaer tubular bags are held in place over

a supporting screen, and dust is collected onthe outside of an open-endup tubular bag.Compressed air released at frequent intervalsto a row of bags causes the bags to pulse out-ward, thus vibrating the fabric, and remov-ing the dust. The dust is cleaned off by a flick-ing action on the collection surfaces ratherthan a reverse flow through the fabric. Feltedfabrics usually are Ilsed with outside-in fil-tering. The jet pulse provides uniform pres-sure drop end continuous and automaticcleaning with no moving parts and permitshigher air-to-cloth ratios, resulting in smallerunits for equivalent capacity. The cost of asupporting frame and higher replacementcosts of felted fabrics over woven fabricsare disadvantages of this method.'"

Reverse air flexing is achieved by a double

or triple cycle deflation of the bags followedby gentle inflating through low-prey. ure re-verse flow, as shown in Figure 4-79. The

cleaning is not (xclusively shaking, be-

caose some backwashing occurs. This methodis used for inside out filtering with fiberglassbags.

COMPRESSED MR

OUTSIDE INFILTERING

SIDE VIEW

rtstAS 4-78. Jet pile. diet collector hag cleaning.

111.9

EXHAUST

REPRESSURINGVALVE

SIDE VIEW

FILTERING

Fict.nE 4-79.

COLL APSIt'G CLEANING

Reverse Cs flexing to dean (lust collector bags by reprtssuring.

Occasionally, sonic generators are used toprovide additional fabile vibrations forcleaning action.'" Sonic generators vibratethe dust loose from the collecting fabrics asshown In Figure 4-80. They are sometimesused to supplement repressuring and reverseflow cleaning. Some carbon black and zincoxide installations are using repressuringand sonic horns to clean fiberizia.s bags.'"

Pcrersc air /low is Divided into three meth-ods: repressuring cleaning, atmosphericcleaning. atmospheric cleaning, and reverseJet cleaning.

AIR HORN

FILTER PAO

OUST

SOUND WAVES

SIDE WE*

frog 4- ZO. Softie cleaning of dust collettot tsgs,

120

INLETVALVE

liepre..suring cleaning is a low-pressure,high-volume, reverse flow of air through thebags as shown in Figure 4-81. It is used forwoven or felted bags.

Atmospheric cleaning is used in closed sue.tion baghouses. An atmospheric vent isplaced into the damper of the fan so thatwhen the compartment damper valve closes,the vet opens to the atmosphere allowing abackwash of air to clean the cloth, as shownin Figure 4-82. This action is gentle and isonly used with fiberglass cloth and easily re-moved dust. Sonic horns may be used to sup-

INSIDE OUTFILTERING

SIDE VIEW

rfulltt 4-51. Repref..41,ting cleaning of dust collec-tot bags.

EXHAUST CLOSED

PENT OPEN

OPERATING

FIGURE 4-82 Cloth cleaning

plement the cleaning action. The amount ofbackwash air ix dependent on cloth resist-ance. If the resisthnce is high the amount ofbackwash air is diminished, thus reducingthe cleaning action.'"

Reverse jet cleaning uses a travel:..ir com-pressed air ring which moves up and downthe outside of a tubular filter bag, thus Wm-

lOP ENTRY

HIGH PRESSUREAIR BLOWRING

natio 443.

INSIDE OUTFILTERING

CROSS-SECTION

Reverse let &waning of dui collectorbap.

CLEANING

TO NEXTCOMPARTMENT

SIDE VIEW

by reverse flow of ambient air.

ing the dust back through the cloth and offthe inside of the bag with compressed air asshown :n Figure :-88. Re-entrainment offine dust during cloth cleaning has causedhigh pressure drops across some baghousescollecting fine fumes. The design is used suc-cessfully with felted bags with high air-to-cloth /iiii(13 collecting relatively coarse, nor.abrasive dusts The replacement cons of bagsis somewhat high. The unit allows a compactInst

The volume of air blown through the slotof the blow ring usually ranges from 1.0 to

cubic feet per minute per linear inch ofzJ .t."' Slot widths range from 0.03 to 0.2binch."'

Pabrie ScirctioaFabrica that areprezently applied in commercially availablebagh)uses are shown in Table 4-18.1",'"- l"The finish adplied to these fabrics is de-scribed in Section 4.7.4.8.

When comparing fabric cost ranks givenin Table 4-18, other t "ctors also should beconsidered. Use of a high-temperature fabricreduces the amount of dilution cooling re-q iired.'" A high - temperature fabric requiresless filtering area. For example, when coolinggases from 400°F to 260°F with ambient airat 90°F, the final gas volume is increased byCO percent, The filter operating at 400°F re-

121

Table 4-I8.FI1.TER FABRIC CHARACTERISTICS "11 "'

Operating Mrexposure Supports perme-

Resistance

Composition Mineral Organic CostFiber cf.-. corn- abilitybuatfon Abrolon adds adds Alkali tankcfm/fti

Lor.g Short

Cotton , 226 yes 10-20 Cellulose 0 P 0 0 1

Woo; 200 260 no '2 0 6 0 Protein 0 I' IP p 7

Nylon 4 200 260 yes 16-80 Polyamide E P F 0 2Orlon 4 240 276 yes 20 -/6 Polyserylonit rile 0 0 0 F 8Dacron 4 276 326 yea 10-60 Polyester E 0 0 0 4

Polypropylene 200 260 yea 740 Olefin E E E E 6

Nomex 4 426 600 no 76-64 Polyamide i F E 0 8

Fiberglass.. 660 600 yes 10-70 Glass P-F E E P 6

Teflon'.... 4150 600 no 16-65 Polyfluoroethyiene F l E E 9

email at 0.6 In. W.G.P. Poor. F. Fair, -Good, E F:xcelient.

Coat rank, 1 et lowest coat, highest cost.+Dupont registered trademark.

quires only 61.5 percent as much cloth area asat 250°F. These reductions will also lowerpower costs for operating the filter."'

Fabric materirls less commonly used arecarbon, metals and ceramic fibers that willfilter gases at temperatures up to 1600°F."NBeta fiberglass, a relatively new product, ismore flexible than regular fiberglass andabrades less in service.'"

414.4 Auxinary h'quipment---Auxiliaryequipment that is selected during the originaldesign includes dust handling equipment andprecooling equipment.

Dust handling rcuipmrntFor collectorsthat are regularly cleaned and re-used, suchdust handling equipment as hoppers must beprovided for the collected dust. Hoppersempty through $1 dust gate, rotary lock ortrickle valve into a screw or belt conveyor, atruck body or a tote bin.'" The dust is thenconveyed to the final disposal point.

Careful consideration must be Oven to thedust handling system at the time the fabriccollector is originally designed.'" Failure todo so may result in leakage in the system thatwill redisperse the collected dust and createair pollution problems. Inaccessibility of thehandling equipment for servicing will makemaintenance difficult. Under-siting of the dustdisposal mechanism may block the upstreamflow of process materials.

Praooling ercipoirtifThe application ofcloth filtration to the cleaning of furnacetrues in most cases requires that the gases be

122

cooled in order to protect the filter fabric andto ensure economical bag life. The followingthree cooling methods are employed zingly orin various combinations:"4

1. Radiation and convection cooling, thisrequires a relatively large Investmentin ti-tube coolers, or heat exchangers.

2. Admission of outside air for cooling,this results in relatively large filtra-tion volumes with a resultant in-crease in the size of the gas cleaningcquii;iment.

3. Spray cooling. this is the most eco-nomical with respect to capital in-vestment, but requires careful con-trol of cooling water sprays in orderto keep the temperature of gases highenough (75C}' i.b:ve dew point) toprevent condensation, which causesplugged filters.

Radiation and convection cooling, andspray cooling cannot be used for a gas ofhigh moisture content. Only the temperingair method can be used to avoid condensationof the moisture. Regulation of temperatureis accomplished easily by this method. How-ever. ihe outside air used for cooling alsomust pass through the filter, so the filtermust be considerably larger than a filter usedwith t' -tubes or spray coolinr, methods.

Sp.tiy cooling of hot gases is the least ex-pensive method because the initial cost isreasonable, the maintenance is relative4easy, and the increase in gas volume to be

filtered is nominal. However, careful controlof cooling is needed to hold the temperatureof hot gases 60°F to 75°F above the dewpoint.'"4.7.4.7 Individual Collectors Versus LargeCollecting SystemsThe individual fabriccollector has several advantages over a largecentral collecting system in manufacturingplants where relatively few dust sources mustbe controlled." The unit collector is self-contained, and has a lower erection cost be-cause the unit is shipped erected, or nearlyso, and because !t can be installed at the pointof need with minimum duct work. The unitcollector's mobility is often economically im-portant in a plant with idle batch processeswhere idle unit collectors may be moved tosites requiriv.g dust control. The large centralcollecting system requires considerable floorspace and is often erected outdoors. Outdoorerection of a central system may require in-sulation and even supplementary heat inputto avoid chilling the gas to the dew point. Thelarge central system is preferred in largemanufacturing plants where many dustsources of continuous processes must be con-trolled.

4.7.5 Typical App Prailena

The following examples of fabric collectorapplication are presented to show how theymay be applied to control particulate matterfr ?tit various sources. The use of fabric filtershas been extended by the introduction offiberglass bags capable of operations at tem-peratures up to 6501F. The use of syntheticfabric bags has resolved many problems as-sociated with corrosive or moderate tempera-ture dust emissions.

1.73.1 Cement KilnsThe collection of thedust from rotary cement kilns has long been.a difficult problem. The difficulty arises fromthe large volumes of gas involved, the heavyloading of vet-) fine particles, the high gastemperatures, and in the case of wet-processkilns, tile presence of a large amount ofwater vapor.'"

The conventional cyclone will collect a highpercentage of the dust, but beyond this pointthe electrostatic precipitator is the only de-

vice besides the fabric collector capable offinal and complete cleanup.'"-"' Efficienciesas high as 99.6 percent, outlet loadings below.02 grains per standard cubic foot, and plumeopacities less than 10 percent have been re-ported for fabric filter applications to cementkilns.'"4.7.52 Fo 14 ',dory CupolasEmissions from agray Iron cupola are a prime example of par-ticulate matter than can be controlled withhigh temperature fabric filtration. Cupola ex-haust temperatures range from 1000° F to2200° F with an average effluent loading ofabout 1 grain per cubic foot.'" Me' of theemission is fine metal oxide fume less than0.5 micron in diameter. Gas cooling and high..temperature fabric filters are required.Evaporation cooling by water sprays is themost common technique used in gas cooling.Off-gas temperatures are reduced to about450° F before filtration through fiberglassbags. In a typical installation the gas is Al-tered at rates of about 2.5 feet cfm /ft'through tubular bags that are 111/2 inchesin diameter and 151,4 feet long. A bag life ofone or two years can be expected if bags areused continuously. In noncontinuous service,averaging 20 to 40 on-otrearn.hours per week,bags have been reported to last four or flv,years.'"

4.7.5.3 Klectric it re Steel FurnacesThe elec-

tric arc steel furnace presents an emissioncontrol problem that is characterised by fineparticulate matter containing a high per-centage of oxides of iron, dispersed in a gasstream that is highly variable in tempera-ture, loading, and volume during the differ-ent process cycles. Effluent volume is de-

pendent on the type of hooding arrangementemployed because the dilution air fib,- is ad-justed to provide for gas cooling and in-plantdust control. Stack temperatures may reach760° F or higher with closed, hooded units.'"

The first large-scale fiberglass filter in thesteel industry was installed in 1959 at a Se-attle steel mill.'" This unit handles 105,000cfm at temperatures up to 600° I using fiber-glass bags 111,4 inches in diameter and 28feet long that operate at an air-to-cloth ratioof 1.4. The fiberglass bags are cleaned by co'.

123

Another example is a furnt.....: melting 46tons of steel scrap in four hours and usingan Orlon fabric filter to handle a volume of60,000 cfm at 200°F. The bag replacementcosts are approximately $1400 per year witha five year bag life.'"

4.7.5.4 Open Hearth FurnacesA majorsteel company conducted a study which foundthat iron oxide fumes generated by an oxy-gen-lanced open hearth furnace could be col-lected efficiently by fiberglass bags."1

The 10-compartment baghouse used in thestudy handles 145,000 cfm at 500° F, basedon a filter ratio of 2 cfm/ft2 when nine of theten compartments are in operation. Each ofthe ten compartments contains 80 fiberglassbags, 111/2 inches in diameter and 34 feetlong (or 8070 square feet of filter surface percornpartment). Reverse air flex cleaning,supplemented by sonic horns, is used. Theefficiency of the baghouse is well over 99 per-cent under all conditions of inlet gas volumeand dust loading. Inlet particulate loadinghas been as high as 20 grains per cubic footduring periodic cleaning of heat regenerativesurfaces. The outlet dust loaf.;ng has beenmeasured at 0.007 grains per cubic foot.'

4.7.5.5 Nonferrous Metal FurnacesOne ofthe largest secondary lead smelters in thecountry has converted from synthetic fiber tofiberglass bags to permit fume collection attemperatures higher than 400° F. This in-stallation cleans the combined effluent from areverberatory furnace and a lead blast fur-nace. Higher filtering temperatures weredesired in order to eliminate the deposition oforganic tars on the bags. After 16 months'experience with fiberglass bags, operated at1.2 cfm /ft' and cleaned by shaking, resultsare reported as satisfactory."'

After completion of pilot-scale studies withboth synthetic and fiberglass media at an in-tegrated smelter producing primary copperand zinc, a baghouse equipped with 222,000square feet of fiberglass bags was con-structed to clean the effluent streams from areverberatory furnace and copper convert-ers." Fiberglass fabric was selected becauseof its corrosion resistance and because opera-tion at 460° F reduced by 50 percent the ra-diation-convection heat transfer area that

124

would have been required for cooling to tem-peratures safe for organic media. The aver-age filter ratio is 1.6 cfm /ft'. Bags 6 inchesin diameter and 10 feet long are used. Bagcleaning involves collapse every half hoursupplemented by mechanical shaking everyeight hours. Sonic cleaning equipment hasbeen tried experimentally. Based on presentknowledge, an average bag life in excess oftwo years is anticipated.

4.7.5.6 Carbon Black PlantsBaghousesequipped with fiberglass bags are reportedto be in use for the final cleaning in 35 of the37 carbon black plants in the United States.'"Earlier baghouses used synthetic bags andkept the filtration temperature below 250° Fto protect the media. However, the tempera-ture was regulated by evaporative cooling,which brought the gas stream close to theacid dewpoint and caused serious corrosionof fabric. The introduction of fiberglass in1953 minimized this problem by allowing op-eration at temperatures of 400° F to 500° F.Bag collapse, with some supplementary vi-bration from sonic horns or other gentlemeans is the most common technique used forcleaning the fiberglass filters. Air-to-cloth ra-tios are usually 1.6:1. The average baghousecapacity is around 50,000 cfm, and bag lifeis 12 M 18 months.'"

4.7.5.7 Grain Handling OperationsThe im-portant sources of grain dust emissions arecleaning, rolling, grinding, blending, and theloading of trucks, rail cars, and ships. Con-veying and storing grains also cause dustemissions.

Low- and medium-efficiency cyclones onlyhave been used because of the increased op-erating costs and maintenance problems as-sociated with high-efficiency multiple cy-clones. For grain dusts larger than 10 mi-crons in diameter, medium-efficiency cyclone,.are satisfactory. For grain dusts smaller than10 microns, the fabric filter is preferred."Often, air streams containing large amountsof dust are passed through a cyclone to re-move coarse particles before being directedto a fabric filter. This technique relieves thefabric filter from handling a high volume oflarge particles. Recei'..ing, handling, andstoring operations require hooding the emis-

sion source and conveying the dust-laden airto dust collection equipment. For receivinghoppers used in unloading rail cars andtrucks, a method of control is to exhaust airfrom below the grating. The indraft velocityrequired will range from 100 to 300 feet perminute depending on whether the hopper isin a building or outside and exposed to winds.

The fabric filters with the open pressureor closed pressure baghouse with mechan-ically shaken woven cotton bags are reportedto remove 99.9 percent of grain particles inthe size range of 1 to 5 microns.," The air-to-cloth ratios are about 6:1,

Reverse jet filters which use felted fabricsare reported to remove 99.9 percent of grainparticles in the size range of 1 to 5 micronswith an air-to-cloth ratio as high as 15:1,although ratios of 12:1 are more common.168

4.7.6 Operational Practices

Operational practices are somewhat differ-ent for woven fabrics and felted fabrics. Thebag life of woven fabrics is related to clean-ing frequency. The more often a fabric, es-pecially fiberglass, is cleaned, the shorter thebag life; this assumes that cleaning is con-ducted often enough to avoid fabric blindingby a dust overload. Fabric cleaning may bedone when the pressure drop across the bag-house, or one of its compartments, increases.to 6 inches of water."' In large baghouses,fabric cleaning is scheduled by compartmentbased on previous operating experience.

To avoid plugging of woven fabrics be-cause of condensation, the gas temperaturein the baghouse should be 50° F to 75° Fhigher than the dew point of the gas.," Insome cases, insulated duct work and bag-houses are needed to maintain gas tempers-tures. In some installations, a small auxiliaryheater is used to prevent condensation in abaghouse when it is shut down.

The bag life of felted fabrics is pro-longed by reducing the frequency of clean-ing. The cleaning cycle may be scheduled tohold the pressure drop across a reverse jetbaghouse with felted bags to 3-5 inches ofwater."' Figure 4-48 illustrates the effectof pressure control on filter resistance in areverse jet filter for dusts and fumes.'"

DUST AT 5 TO 10 gr/fe3OR METALLURGICAL FUMEAT 1 gr/i13

20 40 60 80

REVERSE JET OPERATION, percent

FIGURE 4-84. Effect of cleaning frequency on filterresistance in reversejet baghouse.(Courtesy of Air Conditioning, Heating, and

Ventilating magazine)

To avoid plugging of felted fabrics whenhandling gases with high moisture content,the use of preheated air for reverse jet clean:ing may be necessary."'

4.7.7 Maintenance ProceduresMaintenance of a fabric collector is often

related to adequacy of the original design.The installation of filters with high air-to-cloth ratios is often responsible for rapid re-:placement of bags. The replacement may beneeded because of blinding of fabric or ex-cessive bag wear.

An unusually heavy grain loading maycause excessive wear or blinding of a wovenfabric. As a rule of thumb, particulate load-ings above 10 grains per cubic foot are oftenhandled by a precleaner such as a medium-or low-efficiency cycloi, !."° The cyclone willremove a large amount of particulate mattergreater than10 microns in diameter. Reversejet and pulse jet collectors can handle, with-

125

100

out a precleaner, dust loadings up to 80grains per cubic foot for particulates largerthan 00 microns.'"

Many b:tghouses are designed with com-partments so that, one compartment can beshut down while the rest of the dust collectorcontinues operating. Means for easy access tothe bags should be included in the originaldesi;!n.

Leakage through the filter is perhaps themost important service problem. Each bagmust be regularly inspected for holes ortears. Regular measurement of down-strenmdust concentration should be made eithermanually or with an electronic-eye, to warnof an increase in dust content of the

Bag spacing is important. Sufficient clear-ance must be provided so that one bag doesnot rub another. A minimum clearance of 2inches is needed between bags 10 or 12 feetlong," while longer bags require greatrclearance distances.

The fan motor and bearings, shaking de-vice, reverse jet blow rings, valves, anddampers must be lubricated regularly andchecked for wear.'" To avoid extended down-time, worn parts should be replaced beforethey fail in service.

Regular inspection of ducts, hoods, frame-work, and housing for signs of wear fromcorrosion, erosion, excessive heat, and exces-sive moisture should be made. '3°

Pressure guages, thermocouples, flow me-ters, and all other instruments must bechecked regulary to ensure that they arefunctioning accurately.'3n

A preventive maintenance program shouldbe established and followed. Regular routineinspection of major lubricant locations isneeded. The schedule may be altered to fitspecific installations of dust collectors.'3°

4.7.8 Safety

Whenever dust is a combustible material,the principal hazard in the operation of fab-ric collectors is that of explosion and fire.Other hazards may arise in special cases, de-pending upon the toxicity or abrasiv,mess ofthe dust, i.e., human health hi zards such asmetal poisoning and silicosis. Continuous

126

monitoring of discharge effluents is needed toavoid any mishaps.'''''

18 AFTERBURNERS

1.8.1 IniroluctionAfterburners are gas cleaning devices

which use a furnace for the combustion ofgaseous and particulate matter. Combustionis accomplished either by direct flame incin-eration or by catalytic combustion.

The disposil of particulate matter by com-bustion is limited to residue-free vapors,mists, smoke, and particulate matter which isreadily combustible, as well as to particlesizes which require short furnace retentiontime and small furnace size. Afterburners areusually used to dispose of fumes, vapors, andodors when relatively small volumes of gasesand low concentrations of particulate matterare involved.

4.8.1.1 Definition of TermsDirect flamecombustionThe use of a separately-firedburner in direct flame contact with the par-ticle-laden gas to sustain rapid oxidation.Heat transfer occurs by conduction, convec-tion, and radiation.

Catalytic combustionA method of oxi-dizing combustible gases and vapors on thesurface of a catalyst, without flame and ata lower temperature than correspondingflame temperatures.

CatalystA substance which increases thecombustion rate and theoretically is un-changed by the combustion process.

Flash point temperatureThe lowest tem-perature at which the vapors above a volatilecombustible substance ignite momentarily inair, tested usually by applying a small flameunder specific test conditions. Flash pointtemperatures are dependent on the geometryof the vapor-filled space, and differ fromopen and closed containers.

Auto-ignition temperatureThe lowesttemperature at which a volatile flammablesubstance will ignite and sustain combus-tion."'

4.8.1.2 Advantages and Disadvantages of Af-terburnersThe advantages and disadvan-tages of direct flame and catalytic afterburn-ers are cited to allow a comparison to be

made of the two types of gas cleaning de-vices.

Direct flame Advantages of the directflame incineration afterburner include: (1)high removal efficiency of submicron odor-causing particulate matter, (2) simultaneousdisposal of combustible gaseous and particu-late matter, (3) compatibility with existingcombustion equipment, CO relatively smallspace requirements, (5) simple construction,(6) and low maintenance.

Disadvantages include: (1) high opera-tional costs including fuel and instrumenta-tion, (2) fire hazards, and (3) excessiveweight.

Catalytic Advantages of the catalytic af-terburner include: (1) reduced fuel require-ments, (2) and reduced temperature, insula-tion requirements, and fire hazards.

Disadvantages include: (1) high initialcost, (2) sensitivity to catalytic poisoning,(3) inorganic particles must be removed andorganic droplets must be vaporized beforecombustion to prevent damage and pluggingof the catalyst, (4) catalysts may requirefrequent reactivation, and (5) lower effici-ency at the usual catalytic afterburner oper-ation temperature.

Catalytic afterburners frequently requirea direct flame air preheater to initiate andsustain catalytic combustion, thereby furtherreducing the relative advantage of the cata-lytic afterburner. Methane from the incom-plete combustion of the direct flame pre-heater fuel is not oxidized at low temperaturein the catalyst bed. Incomplete combustionand the formation of oxygenated compoundsmay be prevented by operating the catalystbed at elevated temperatures with a conse-quent reduction in the thermal advantage andfuel savings over direct flame combustion.

Catalytic afterburners frequently are un-able to meet the local code requirements asto combustion efficiency at the usual cata-lytic afterburner operating temperature.

4.8.1.3 Combustion ThcoryCumbustion isthe chemical reaction of a fuel with an oxi-dant, involving the disappearance of the

* Los Angeles County Rule No. 66: 90 percent ormore of the carbon in the organic material being in-cinerated must be oxidized to carbon dioxide.

original reactants and the production ofheat and oxides. Combustion usually takes'dace in a thin reaction zone.

When solid fuels burn, the reaction zoneis confined to the surface of the particle.At low temperatures the combustion rate islimited by the chemical reaction rate, where-as at higher temperatures the chemical-reac-tion rate is so rapid that the rate of airsupply controls the combustion rate.'". '"

Combustion of liquid droplets and volatilesolids occurs away from the surface of theparticle and combustion rate may be depend-ent on the rate of heat transfer to the sur-face, which causes evaporation and thermaldecomposition of the solid. Combustion isinfluenced by the gas velocity, the rate ofmixing, and the supply of oxygen.'",

The temperature in the combustion zonesurrounding the particulate matter may ex-ceed the temperature at the interior of theparticle and in the surrounding gas by sev-eral hundred degrees. Heat transfer is large-ly by radiation from the incandescent surfaceof the particle, or from the incandescent car-bon formed as an intermediate step in thecombustion process.'"

Cat«lytir combustionThe mechanism ofsurface catalysis is very complex. The cata-lytic combustion process occurring on thesurface of the catalyst involves diffusion ofthe reacting molecules to the surface of thecatalyst through a stagnant gas film whichsurrounds the surface of the catalyst, adsorp-tion of the reactants on the surface, chemicalcombination of the reactants, desorption ofthe combustion products, and diffusion of thecombustion products from the surface of thecatalyst to the main gas stream. The rateof catalytic oxidation is usually controlledby adsorption, chemical combination, desorp-tion, or a combination of these.""

Catalytic combustion occurs at a lowertemperature than direct flame oxidation bysubstituting catalytic adsorption energy forthermal energy of activation (energy neces-sary for chemical combination) and by in-creasing the concentration of the reactantson the surface of the catalyst.

The chemical union of the oxygen with theorganic compounds occurs without flame onthe surface of the catalyst, with the transfer

127

of the heat of combustion from the catalyticbed to the gas stream.

Many substances exhibit catalytic proper-ties, but metals in the platinum family arerecognized for their ability to produce com-bustion at minimum temperatures. Becausecatalysis is a surface phenomenon, relativelysmall amounts of metal are used and sup-ported to expose a maximum of surface area.Other catalysts include copper chromite, andthe oxides of copper, chromium, vanadium,manganese, nickel, and cobalt."6,

Catalysts may be subject to poisoningfrom such materials as zinc, arsenic, lead,mercury, copper, iron, antimony, and phos-phates. Other materials which commonlysuppress catalysis include halogen, and sul-fur compounds.us. 1i9 Poisoned catalysts maybe reactivated by periodically washing thecatalyst with acid solutions.

4.8.2 Aftt rburner Design Criteria.4.8.2.1 GeneralVariables which must beconsidered in the selection and/or design ofafterburners for particle-containing gaseouswastes are heat transfer, reaction temper-ature, particulate size, mixing, flame contact,residence time, inlet gas temperatures, andcomposition. The variables are interdepend-ent and, as a consequence, design criteria aresemi-em Arica! because of the large rangeof materials dealt with, the lack of designdata, and the relatively loose control of op-erating conditions.

4.8.2.2 Heat TransferThe transfer of heatfrom burner flame to gaseous and particulatematter is an important factor in determiningthe furnace size, operating temperatures,and fuel requirements of direct flame con-tact incinerators. Heat transfer is begachieved by mixing when gases are burned,and best achieved by radiant heat transferwhen particulate matter is burned.1"91"

For purposes of burning particulate mat-ter, radiant heat transfer and furnace tem-perature uniformity may be increased by in-creasing the emissivity of the burner flame.This can be accomplished by limiting theair supply to produce a sooty flame, by usinghigh carbon-to-hydrogen ratio (C/H) fuels,by adding soot or fuel oil (by carburetion)

128

to gas flames, by using low-velocity burners,through poor mixing of air and fuel, and byaltering furnace design."'J -"I

4.8.2.3 Reaction TemperatureMost directflame burners operate in the 1200° to 1500°F temperature range in order to obtain maxi-mum combustion within the limits of flamecontact, mixing, and residence time in thefurnace."

Figure 4-85 illustrates the effect of airvelocity and particle diameter on the com-bustion rate of carbon."6 1" The effects ofparticle size, reaction temperature, combus-tion gas composition, and gas velocity on thecombustion rate of carbon, coal, and a num-ber of other compounds have been investi-gated.171-174, 1,9-1511

Adsorption catalysts are used in fumeburners operated in the 800°F to 1200°Ftemperature range. Furnace and catalysttemperatures, space, velocity, and bed depth

1000

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000 1400 1600 1800 2000 2200

TEMPERATURE (°K)

FIGURE 4-85. Effect of air velocity and particlediameter on the combustion rate of carbon. (Don.particle diameter)

are used to achieve the desired level of com-bustion efficiency (Figures 4-86 and 4-87).19: 191

Compounds such as methane, which aredifficult to oxidize, require a catalytic bedtemperature approximately 200° F higherthan ethane, propane, butane, and othermembers of the paraffin series. "' Carbonmonoxide, which is difficult to oxidize by di-rect flame combustion at low temperatures,is easily oxidizer, by platinum at a temper-ature of approximateiy 300° F and by hop-calite catalysts at room temperature.1T6. 196

100

90

80

70

60

50

40

30

20

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FIGURE 4-86.terburner.

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REACTOR INLET TEMPERATURE. 'F

900 1000 1100

TEMPERATURE, °F

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Combustion efficiency of catalytic af-

SP1RAL-WOUND_METAL FOILS

4 in. DEEPBED

FIGURE 4-87. Effect of temperature and velocity onabatement effectiveness: spiralwound metal foilscatalyst support.

(Courtesy of the Journal of the Air Pollution Con-trol Association)

4.8.2.4 Retention TimePre-heat (induc-tion) and combustion times will dictate theoverall residence time of the particulate. mat-ter in the afterburner. Residence time re-quirement will determine both combustionchamber dimensions and efficiency.

The time required to heat the waste gasto pc* furnace temperature is dependent onthe burner combustion chamber dimensionsand efficiency.

The time required to heat the waste gas topeak furnace temperature is dependent onthe burner combustion intensity and inletgas temperature and may be computed asfollows:

heat up time (seconds) -=heat capac. of gas (Iltu/ft'-°F) x temp. rise ( °F)

(1)combustion intensity (Rtu /ft' -sec)

Values of combustion intensity will varyfrom 1 Btu per cubic foot per second for low-pressure gas jet mixers to 500 Btu per cubicfoot per second for premix mechanical burn-ers. A typical value is 140 Btu per cubic footper second for premix high-pressure gas jetmultiple-port burners.

The time required to heat a gas with aheat capacity if 0.0182 Btu /ft' - °F, from200° F to 1800° F in a furnace with a com-bustion intensity of 140 Btu per cubic footper second would be:

Time (seconds) =0,0182x (1800200) /140 = 0.268 seconds

Combustion time required is dependent onparticle oxygen content of the furnaceatmosphere, furnace temperature, particlecomposition, gas velocity, and mixing of com-bustibles. Combustion times for a number ofdifferent materials have been determined andcorrelated on the basis of the followingequations:196

td = pRiT,x2,,/ (960Dpg) for diffusion-controlled combustion rate (2)

t,..px./(2K,,p6) for chemical reaction-con-trolled cumbustion rate (3)

Where: t,, = diffusion-controlled combustiontime (seconds);L.= chemical reaction rate-controlled com-

bustion time (seconds);p=-- density of carbon residue or coke (gm/

cm');

129

universal gas law constant (82.06 atmcm1/mole/°K);

mean temperature of stagnant gasfilm (°K) ;

x-= original diameter of particle (cm);0 combustion mechanism =1 for CO and

2 for CO2 formation;D= diffusion coefficient of oxygen at tem-

perature T,,, (gm/cm2);p,= partial pressure of oxygen in combus-

tion air (atm); andK. = surface reaction rate coefficient (gm/

cm2 sec atm).

K. me- 1,1 calculated by means of the follow-equations:

K1 =1.035 x 10,x Ts-v.1 x e-211,220 /RTS (for soot)

(4)

K.= 3710 x e-85,700/RTs (for coke and (5)carbon residue)

Where: T.= surface temperature of the car-bon.

Equation 2 holds at high temperature, zerogas velocity, and large particle sizes. Theequation can be corrected for the effects ofgas velocity and turbulence by use of the di-mensionless Nusselt conventional heat trans-fer relationship for spherical particles:1"

Neu =2+ 0.68 Npr1/2 X NRe1/2

Where: NNu = Nusselt Number;

Npr =Prandtl Number, a function ofthe physical properties of thegas; and

NR,, = Reynolds Number, a functionof the physical properties ofthe gas, particle diameter, andgas velocity.

The Nusselt Number NNu=h x/k=2 atzero gas velocity where: h=convectionalheat transfer coefficient (cal/cm2 °C sec);x = particle diameter (cm). h is an inversefunction of the stagnant gas film thickness,x/2, surrounding the particle and directlyproportional to the thermal conductivity ofthe furnace atmosphere, k (cal/cm2 °C cmsec).

The film thickness decreases with increas-ing velocity and decreasing particle size to

130

such an extent that the combustion rate forparticles smaller than 100 microns is limitedonly by chemical kinetics at normal after-burner temperatures.

Equation 2 is of limited value in after-burner design because particles larger than100 microns are easily collected by other gascleaning devices and would require excessiveretention time and furnace volume.

Equation 3 holds for particle sizes smallerthan 100 microns and for temperatures atwhich the combustion rate is determined Lychemical kinetics.

Total combustion time for a carbon resi-due-forming particle then becomes:

tr=ti+tdKv+t, (7)

Where: tr=total residence time (see);

ti =induction time (sec) ; and

K =volatile matter correction factordetermined by the equation:

K,= (1 + E/100) /(1 + E/100V/100) (8)

where: E= percent excess air andV= percent volatile matter

The combustion time for hydrocarbon liq-uid droplets larger than 30'microns at zerogas velocity may be computed using the fol-lowing equation:"'

td= (29,800/pg) Mw T-1.75-x20 (9)

Where: AL.= molecular weight andT= furnace temperature (°K)

The combustion time of particles smallerthan 30 microns is dependent on the com-bustion rate of the hydrocarbon vapors.

The time required to burn a 5 x 10-4 cmsoot particle of 2 grams/cubic centimeterdensity in a furnace atmosphere containing0.20 atmosphere of oxygen at 1800°F canbe f.emputed using the equations 3 and 4. Thetime required would be 0.51 second.

Total residence time in the furnace, in-cluding heat up time from 200° F, would beinduction time + combustion time = totaltime, or:

t,=0.208 +0.510=0.718 second

In practice, minimum gas furnace reten-tion time is about 0.30 second at tempera-

ture of 1200°F. Particle retention time maybe increased by designing the combustionchamber in the shape of a cyclone using asmall tangential inlet, and by introducing tl:egases at a high velocity (Figure 4-88).""

Cyclone furnace dimensions are chosenusing a gas velocity of from 15 to 30 feet persecond."' '91 Good mixing is attained byusing appropriate design parameters to pro-vide turbulent flow in the afterburner.

A tangentially fired, portable hood, smokeafterburner is shown in Figure 4-89.

The combustion constants for a number oforganic compounds are presented in refer-ences 171 through 175,186 through 191, and195 through 197.

4.8.2.5 Heat RecoreryInlet waste gas tem-peratures should be as high as possible tominimize additional fuel and preheat require-ments."`-"' The maximum recoverable en-ergy in afterburner stack gases as ,E; functionof exhaust gas temperature is shown in Fig-ure 4-90, with waste gas energy content andtemperature as parameters.

Heat recovery equipment used to recoverheat from the flue gas may be grouped under

REFRACTORYLINEDSTEEL SHELL

REFRACTORYRING BAFFLE

GAS BURNERPIPING

BURN RBLOCK

INLET FOR CONT/MINATEDGAS STREAM

FiGURE 4-88. Typical directfired afterburner vithtangential entries for both fuel and contaminatedgases.

two classifications: recuperative and regen-erative. Recuperative (recovery) heat ex-changers recover heat on a continuous basisand include cross flow, countercurrent flow,and cocurrent flow heat exchangers (Fig-ures 4-91 through 4-93). For a given heatflow and temperature drop, heat exchangersurface requirements will be at a minimumin the counterflow heat exchanger (Figure4-91)."2

Cocurrent flow heat exchangers are oftenused where a moderate level of heat recov-ery is required. Cour .r.:tirrent flow heat ex-changer construction may be more costlythan that for cocurrent flow, because of op-eration at lower temperatures (near the dew-point), which may require use of special al-loys or alloy steels.

Regenerative heat exchangers recover heatby intermittent heat exchange by the alter-nate heating and cooling of a solid. Heatflows alternately into and out of the same ex-changer, as air and flue gas flow are periodic-ally reversed. Regenerat' z heat exchangersare of fixed and moving bed types.

A fixed-bed, pebble-stove, regenerativeafterburner is shown in Figure 4 -94. Whengas is passed through the pair of pebble-typeregenerators connected back to back, the gasis heated on the upstrem side and cooled onthe downstream side. When the upstreambed and gas temperature drop, gas flow isreversed and the heat transfer process is re-peated. Particulate matter is effectively re-tained and incinerated. Heat recovery effi-cinecies in excess of 95 percent can beachieved."'

A commonly used rotary regenerative heatexchanger consists of a partitioned rotatingcylinder containing heat sink and heat trans-fer surface area. The cylinder is partitionedalong its axis by appropriate gas seals sothat hot flue gas and cold '.caste gas may bepassed through the heat exchanger on op-posite sides of the cylinder. Heat is absorbedfrom the hot flue gas by the heat exchangersurface and transferred by the continuous ro-tation of the heat f.:.xchangr; surface to thecold waste gas side where the heat is ab-sorbed by the incoming cold gases. Heat re-covery efficiency ranges from 85 to 95 per-cent."'

131

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FiGuai: 4-89. Portable canopy hood with stack afterburner.(Courtesy of Eclipse Fuel Engineering Company)I AFTERBURNER TEMPERATURE

1350°Fin"

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1122070

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100 200 300 400 500

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1242

1135

1028

927

814

707

600

PROCESS EXHAUST TEMPERATURE, FFIG u.t: 4-90. Afterburner energy requirements

with fume energy content and temperature pa-rameters.

132

AIR

IiAIR

STACK GASES

AIR

FIGURE 9-91. Counter-flow type.

STACK GASES)

AIR AIR

FIGURE 4-92. Parallel-flow type.STACK GASES

STACK GASES

Ficuar. 4-93. Crossnow type.

NATURAL GAS

TO CHIMNEYBLOWER

FROM KILN

Fi GuRE 4-94. Fixed-bee!, pebble-stone, regenerative destencher.(Courtesy of Research Cottrell)

4.8.2.6 Fuel RequirementsMaximum fuelconsumption for one-pass catalytic after-burners may be as high as 10 Btu per stand-ard cubic foot of waste gas flow, while sys-tems with heat exchangers can economicallyreduce heat requirements to about 4 Btu perstandard cubic foot.1D9 The heating value ofthe waste gas stream is usually limited by in-surance underwriters to combustible vaporconcentrations of less than one-fourth of thelower explosive limits of the gas mixture. Fororganics, this is equivalent to about 13 Btuper standard cubic foot and represents a totaltemperature rise of approximately 675° F,equivalent to 52° F to 55° F per Btu perstandard cubic foot. Catalytic combustors areusually equipped with automatic safety con-trols when treating high organic concentra-tions.

The heat generated by the combustion ofsol.. ent and paint fumes may be directly re-covered by recirculating the combustiongases to the oven (Figure 4-95), or indirectlyrecovered by means of heat exchangers (Fig-ure 4-96). Direct heat recovery may be ad-vantageous in the case of catalytic combus-tion because of lower oxygen requirementsin the catalytic combustion zone.9°' 999 This

can be advantageous with materials havinga low explosive limit.

Fuel savings from the use of the heats ofcombustion of paint bake-oven solvent vaporsmay be large enough to provide a 50 per-cent return on investment in the case ofcatalytic combustion.291

Fuel requirements and burner capacitymay be determined by means of a heat bal-ance, using the heat of combustion of the fueland the sensible heat needed to raise the tem-perature of the waste gas and the productsof combustion up to the desired combustiontemperature. The heating value of the con-taminant must be deducted to determine netfuel requirements."% = -'="

4.8.2.7 Modified Furnace AfterburnersEx-isting boilers, rotary kilns, and furnaces havebeen successfully modified and used for directflame incineration. Requirements for success-ful operation are:

1. Contaminants must be combustibleand non-corrosive.

2. The oxygen content of the contami-nated gas must be high, or of suchvolume that it does not upset or re-duce furnace capacity.

133

PREHEATBURNER

ALL-METALCATALYST ELEMENTS

FRESH MAKE-UP AIR

FROM SOLVENTEVAPORATION ZONE

CLEAN GASES

FROMBAKE ZONE

PAINT BAKE OVEN

SUPPLYFAN

HEATED DECONTAMINATED

7AIR RETURN TO OVEN

FIGURE 4-95. Direct recirculation of combustion gases to recover heat.

HEAT EXCHANGER

COLOFRESHAIR

CATALYTIC SYSTEM

,SUPPLY FAN

AO'

HEATED MAKE-UP MR

PREHEAT BURNER

PAINT BAKE OVENFiGuRE 4-96. Heat exchanger to recover heat from combustion gases.

(Courtesy of Universal Oil Products Co.)

3. The furnace must be operated con-tinuously or modulated to ensure ade-quate furnace temperatures.

4. The furnace must be large enough toensure adequate residence time.

6. Conditions must be such that there islittle or no deposition of particulatematter on the burner or furnacewalls.

134

Furnace modifications, design calculations,and proven methods for introducing wastefumes are given in the literature.'

Odors from kraft pulp manufacture havebeen successfully disposed of by introductioninto a modified furnace kiln with fuel savingsof over $450 per month.")", "°

4.8.2.8 Hood and Duct Design Considera-tionsFurnace inlet gases, and vapors from

1 EXHAUSTER2 PREHEAT BURNER3 CATALYST4 RECYCLING DAMPER5 HEAT EXCHANGER

STACKDISCHARGE 1 COLD OUTSIDE

AIR

0

1.1\WAX

COOLINGSTATION

\\\N\COOKINGSTATION

N\N\NNN\

PREHEATEDFACTORYSUPPLY AIR

FIGURE 4-97. Integration of fume disposal from a kettle cooking operation with flctorymake-up air heating.

(Courtesy of Catalytic Combustion Co.)

paint and varnish cooking kettles, as well asfrom other sources, must be maintained attemperatures above condensation to avoidexhaust duct fouling. Collection ductwork isusually insulated and may be heated bymeans of an external duct which serves torecover heat from the flue gas, effecting areduction in combustor fuel requirements(Figure 4-97).24'

Duct gas velocities are usually high, rang-ing from 4000 to 5000 feet per minute, toprevent the settling of particulate matter, toeffect a high heat recovery rate between theflue gas and furnace feed gas, and to minimizethe danger of flashback and fire hazards.2w,"

Other safety devices to minimize fire haz-ards may include diluting vapors to belowthe lower explosivetliniits, using flame ar-restors, and including a %Vet scrubber be-tween the direct flame combustor and thevapor source. Dilution of the vapors may beaccomplished by recirculation of a portionof the flue gas, with a substantial reductionin fuel requirements, as shown in Figure

Flame arrestors may consist of a packedbed of pebbles, metal tower packing, alumi-num rings (Figure 4-98), or corrugated

metal gridwork (Figure 4-99),. in conjunc-tion with a blast gate or other pressure re-lease device. Flashback through the bed isprevented by bed gas velocities in excess offlame propagation velocities, by pressuredrop, as well as by cooling the flame tobelow combustion temperatures."' 2"

Other types of flame arrestors includespray chambers, wet seals, and dip legs (Fig-

-4"TO

COMBUSTOR

FIGURE 4-98. Packed bed flame arrester.

n 11rrirre77...... //,/

oveeie,/#/

PACKING...Oe/e ......

WASTE GAS

BLAST GATE

135

me 4-100). Wet flame arrestors have the dis-advantage of cooling and humidifying theexhaust gas, with a consequent increase infuel requirements. Wet sprays are capable ofremoving up to 80 percent of the solids in-volved in paint making; there is no notice-able reduction in odor level."

TUBE BANKSHELL

Other safety devices include high- and low-temperature combustion and flame-out con-trol instruments.

Exhaust hoods should be close fitting tominimize ventilation requirements. Guidanceon hood design and ventilation rates is of-fered by the Amer Iran Conference of Gov-ernmental Industrial Ilygienists."1

4.8.2.9 Gas Darnel sFigure 4-101 shows across-sectior,1 view of an open-type inspira-tion (venturi mixer) premix burner. Thismixer uses the ene qty of the gas to induceprimary air in Drop irtion to the gas flow andis limited to cases in which high pressuregas (6 to 10 pounds per square inch) is avail-able.

F oun 4-99. Corrugated metal name arrester withmile removed and tube bank pulled partly outof body.

(Coarttsy of General Pete laion Systems, /rte.)

WASTE GAS

flows: 4-100. Dip leg flame amster.

186

SPIDER LOCK SPUDNUT AIR INLET

Fict-an 4-101. Cross-sectional view of open type in.spirational premix burner.

Luminous flames may be produced by con-ventional burners by operation at low ca-pacity and by restricting air supply. Mini-mum burner capacity is determined by theburner throat velocity at which flashbackcan occur."' "*. "' The turndown ratio (ratioof maximum to minimum flow rate for satis-factory burner operation) will range from311 to 5:1.

Pressure-type burners, illustrated in Fig-ure 4-102, permit a higher rate of heat re-lease withir a relatively small space and areAvailable in a multitude of designs for specialapplications. They are .cl,aracterized by asingle mixing port or nozzle which producesa short hot flame. Gas premixing is accom-plished by use of forced inlet combustion air.usually supplied by a fan. This type of burnerhas a high turndown ratio and is capable ofproducing an accurate control of the gas comebustion mixture.

%Taste pPS may be used as a source ofprimary and secondary air, with a consequentreduction in fuel requirements, if the oxygen

NM s 1111(1L*

RATIO DIAL COMBUSTION

AS INLET AIR INLET

loi."1-,All -aft=.11I, _ a.m.. prIb......._-#.:, ...iiim"-

RATIO VALVE 1141BURNER ,-'

HOLE FOR PILOT TIP

TILE

MOUNTING PLATE

Itct.an 4-102. Cross.sectional %.iew of forced air,premix, multiple-port burner.

content is high and the gas is free from de-posit-forming solids.

Burners of the cyclone design, shown inFigure 4-88, are usually mounted to fire tan-gentially into the combustion chamber and toassist in the cyclonic motion and mixing ofthe furnace atmosphere. Burners must becapable of continuous modulation to accom-modate changes in waste gas flow rates."

To prevent the emission of smoke whenthe flame is operated to produce a luminousflame, secondary air or waste gas may beintroduced above the burner.

Combustion intensity may be further in-creased by the use of forced air, premixing,multiple-port burners of the type shown inFigure 4-103. Combustion intensities as highas 500 Btu per cubic foot per second havebeen obtained using a combination of multi-ple port burners and flame impingement on

Fictitt: 4-10.4. ultiple-port high-inter.sity premixtnittltt.

(Cox, ropy of Moron Pre Pais FiRratr Company)

the surface of refractory brick which acts asa catalytic surface.''' Typical uses and com-bustion characteristics for a number of burn-ers are listed in Table 4-14.

The combustion intensity of a given burneris related to the furnace temperature andfuel composition as indicated in the equa-tion:'"

CI = k yr T, C co . e-A/RT, (10)Where: CI =combustion intensity (Blu/ftl

sec atm);k is a constant;

p,,atmosplieric pressure;T. furnace atmosphere tempera-

ture 'absolute;Cr, C.= fuel and oxygen concentra-

tion;e natural log base;

A energy of activation (approxi-mately .12,000 calories'gmatom); anduniversal gas law constant.

A heat loss of approximately 5 percentfrom the combustion gas can reduce com-bustion gas temperature and reduce combus-tion intensity by as much as 20 percent, witha consequent reduction in afterburner com-bustion efficiency. Hence it is important thatcombustion zone heat losses be kept at a mini-mum. Heat losses can be reduced by properinsulation and by shielding the burner fromcold objects, such as it onwork, heat exchang-ers, masonry or even the sky.

Combustion efficiency is improved if com-bustion takes place at the base of the furnaceand the waste gases pass upward. This mini-mizes opportunity for channeling and by-passing.4.5.1.10 Consfrarfioa MOE- riaisAfterburn-er surfaces exposed to high temperatures anderosive or etarosive conditions must be con-structed of alloys capable of withstandinghigh temperatures or must be lined with re-fractory materials.

.1. toffTemperatures at which alloysteels are used Are limited by Underwriters'Laboratories, Inc, to approximately 200' Fbelow the temperature at which scale forma-tion oectits. Niattensitic and ferritic stainlesssteels are recommended for use in areas thatare exposed to wide ranges of temperature

137

Tab

le 4

-14.

GA

S B

IM=

CL

ASS

IFIC

AT

ION

S

Com

bust

ion

,...

Vel

ocity

inte

nsity

,to

ofap

prox

imat

eoo

xten

t of

mix

ture

mix

ture

Req

uire

d R

e-0'

NA

Tem

pera

- C

ombo

s-m

axim

umT

ypic

:ir

ner

Cla

mill

eatio

nof

air

and

vas

thro

ugh

Mix

ing

met

hod

Os

air

Lur

etic

she

at r

elea

seas

st:o

Aie

sno

zzle

.pr

essu

repr

essu

rera

nge,

'Tsp

eed

per

cubi

cft

/min

foot

of

cim

bwiti

onch

ambe

r sp

ace

Atm

osph

eric

or

low

-Pa

rtia

l. us

ually

less

50 to

Gus

jet r

n...e

r or

Und

er0

100*

toV

ery

slow

10

Btu

/ft'

/see

Rin

g bu

rner

spr

essu

re b

urne

rth

an 5

05, o

f ai

w1,

200

inje

ctor

usi

ng :o

w-

I Ib

.I2

00°

Pipe

bur

ners

syst

em.

requ

id f

orpr

essu

re g

as.

Tor

ch b

urne

rsC

OT

E e

untio

n.B

ox b

urne

rsIm

mer

sion

bur

ners

Whe

el b

urne

rs

Bla

st o

r hi

gh-

pron

oure

bur

ner

syst

em.

Air

and

gas

not

400

toN

ot m

ixt':

;ant

i in

Und

erU

nder

600°

toSl

ow28

Btu

/ft'

/sec

Dif

fusi

on b

urne

rsm

ixed

: low

-vet

oe-

10,0

00co

mbu

stio

n zo

ne.

4 oz

.4

oz.

2400

'R

adia

nt f

lam

e bu

rner

sity

str

atif

ied

orV

arif

lam

e bu

rner

sdi

ffus

ed in

con

s-R

adia

nt tu

be b

urne

rsbu

nion

cha

mbe

r.St

atic

pre

xtur

e bu

rner

s

Air

and

gas

not

400

toN

ot m

ixed

unt

il4

to4

to10

00' t

oFa

st70

Btu

/ft'

/sec

Noz

zle

mix

ing

mix

ed: t

urbu

lent

36,0

00in

com

bust

ion

zone

.IS

oz.

32 o

z.28

00'

burn

er.

mix

ing

clos

e to

nozz

le b

ut in

com

-bu

stio

n ch

ambe

r.

Com

piet

ely

mix

ed2,

200

toPr

emix

ed b

y ai

r4

oz.

4 to

1200

' to

Ver

y fa

st70

Btu

/ft'

/sec

Ope

n bu

rner

sor

nas

ty s

o be

fore

36.0

00j.1

: mix

er.

32 o

z.30

00"

reac

hing

noz

zle.

Gas

jet m

ixer

I to

0H

P ga

s.25

ib.

Mec

hani

cal m

ixer

4 oz

.0

555

to 1

400

Tun

nel b

urne

rs

Com

bina

tion

of th

eB

tu /f

t' /s

ecab

ove.

and to corrosive conditions." Temperaturelimitations for other metals and alloys aredetermined by design stress and safety re-quiren,ents."'

Refractories Refractories used in directflame afterburners increase radiant heattransfer, insulate, act as a support structure,and resist abrasion and corrosion. In sodoing, they must be capable of withstandingthermal shock. Fire clay refractories are com-monly used in incinerator and afterburnerconstruction because of low cost, spill resist-ance, and long service life. Fire clay refrac-tory bricks are classified (Table 4-15) intomaximum service classes according to Amer-ican Society for Testing and Materials stand-ards (ASTM)."2 lheir softening points, as

Table 4-I5.ASTM CLASSIFICATION OF FIRECLAY REFRACTORIES

Temperature.Refractory type PCE

Low heat duty . 19 2768

Intermediate heat duty 29 2984

nigh heat duty 21-32 3056-3092Super duty V. 33 8173

S000

4300

1000

3500

3000

3300

1500

I000

determined by pyrometric cone equivalent(PCE) help determine their maximum serv-ice class.:" Other requirements include limitson shrinkage, spalling loss, and deformationunder load. Castable fire clay refractoriescommonly used (Table 4-16) are of twoASTM classes.":

Table 4-16.COMMONLY USED CASTABLE FIRECLAY REFRACTORIES

ASTM Temper. Density. SpecialNo. attire. `F thift' properties

24 2400 70-85 Insulating light weight27 2700 110-125 General purpose

Service temperature range and physicalproperties of various refractories for cor-rosive conditions are shown in Figures 4-104and 4-105 and in 'Table 4-17. The literaturecontains further information.t".",_"4.8.2.11 Typical it pplira fionsA summary ofthE afterburner applications is presented inTable 4-18. The information was taken frompublished literature and manufacturers' bul-letins.

GRAPHITE, 6400' F

SILICA CASIABLES, INSULATING HIGH CHROME, ZIRCONIA, GRAPHITEMORTARS, BRICK ALUMINA MAGNESITE ZIRCON CARBIDES;PLASTICS BORIOES,

NITRIDES

Flogs 4-104. Service temperature rouges for refractories.(Couttetty of McGroor-hilt Book Co.)

139

Tab

le 4

- 17

.- G

EN

ER

AL

'PH

YSI

CA

L A

ND

CH

EM

ICA

L C

HA

RA

CT

ER

IST

ICS

OF

CL

ASS

ES

OF

RE

FRA

CT

OR

Y B

RIC

K

Typ

o of

bri

ck

Ap-

Typ

ical

pros

. Fus

ion

chem

ical

bulk

poin

t,co

mpo

sitio

n de

n--F

sity

,Ib

ilti

Che

mic

alna

ture

Def

or-

mat

ion

unde

rho

tlo

adin

g

App

arel

%po

rosi

ty,

';,Pe

rme-

abili

tyH

otst

reng

th

The

rmal

shoc

kre

sist

ance

Che

mic

al r

esis

tanc

e

to a

cid

to a

lkal

i

Silk

s31

07.9

6%11

5 31

00A

cid

Exc

elle

nt21

Hig

hE

xcel

lent

Poor

Goo

dG

ood

at lo

w te

mpe

ra-

ture

s.H

igh-

duty

fir

eela

y.. _

SiO

,, 54

%13

4 31

25A

cid

Fair

I8M

oder

ate

Fair

Fair

Goo

dG

ood

at lo

w te

mpe

ra-

A1,

01.4

0%tu

res.

Supe

r-du

ty f

iree

lay

SIG

,. 32

%14

0 31

70A

ied

Goo

dIS

Hig

hFa

irG

ood

Goo

dG

ood

at lo

w te

mpe

ra-

A1,

0). 4

2";

ture

s.A

cid-

resi

stan

t31

0,, 5

9%14

230

40A

cid

Poor

7L

owPo

orG

ood

Inso

lubl

e in

aci

dsV

ery

resi

stan

t in

(typ

e H

).A

1,0)

, 34%

exce

pt H

F an

dbo

iling

phr

epho

ric.

mod

erat

e co

ncen

-tr

atio

ns.

Insu

latin

g br

ick_

_V

arie

s30

-75

Var

ies

__

_Po

or65

-86

Nig

hPo

orE

xcel

lent

Poor

Poor

H ig

h-al

umin

a ,

A1,

0,.

170

3200

-Sl

ight

lyG

ood

20L

owG

ood

Goo

d50

445%

3400

acid

.E

xtra

-hig

h al

umin

a_A

!,0,.

185

3000

-N

eutr

alE

xcel

lent

23L

owE

xcel

lent

Goo

dG

ood

exce

pt f

orV

ery

slig

ht a

ttack

90-9

9%38

50H

F an

d aq

ua r

egia

.w

ith h

ot s

olut

ions

.71

%15

332

90Sl

ight

lyac

id.

Exc

elle

nt20

Low

Goo

dG

ood

Inso

lubl

e in

mos

tac

ids.

Slig

ht r

eact

ion

Chr

ome-

fire

dC

hrom

e19

6V

arie

sN

eutr

alFa

ir20

Low

Goo

dPo

orFa

ir to

goo

dPo

oram

100

%M

agne

site

-chr

ome

bond

ed. "

190

Goo

d12

Ver

ylo

w.

Goo

dE

xcel

lent

Mag

nesi

te-c

hrom

eA

M S

O-

180

Var

ies

Bas

icE

xcel

lent

20H

igh

Goo

dE

xcel

lent

Fair

exc

ept t

oFa

ir r

esis

tanc

e at

fire

d.80

%st

rong

aci

ds.

low

tem

pera

ture

s.C

R70

..5-

18%

3-13

%

5-11

%M

agnw

eite

-chr

ome

high

-fir

ed.

310,

,O

180

Exc

elle

ntI8

Hig

hE

xcel

lent

Exc

elle

nt

Mag

nem

ite-

bond

ed.

181

Goo

d11

Low

Goo

dG

ood

Solu

ble

in m

ost

acid

s.G

ood

resi

stan

ce a

tlo

w te

mpe

rseu

res.

Mag

nesi

te-f

ired

Mgr

), 9

6% 1

78 3

900

Bas

icG

ood

19M

oder

ate

Goo

dG

ood

Zir

con

ZrO

,, 67

% 2

00 3

100

Aci

dE

xcel

lent

25V

ery

low

Exc

elle

ntG

ood

Ver

y sl

ight

Ver

y sl

ight

310,

, 33%

Zir

eoni

aZ

rO,.

94%

245

480

0(s

tabi

lised

),C

aO. 4

%Si

licon

-car

bide

SiC

, NO

-t6

0 41

7590

%G

raph

iteC

. 97%

Wily

6400

Slig

htly

acid

.Sl

ight

lyac

id.

Neu

tral

Exc

elle

nt 2

3

Exc

elle

nt15

Exc

elle

nt16

Low

Exc

elle

ntE

xcel

lent

Ver

y lo

wE

xcel

lent

Low

E-c

elte

nt

Ver

y sl

ight

Exc

elle

ntSl

ight

rea

ctio

nw

ith H

F.E

xcel

lent

Inso

lubl

e

Ver

y sl

ight

Atta

cked

at h

igh

tem

pera

ture

s.In

solu

ble

Goo

d ab

ove

1200

° F.

h C

hem

ical

ly b

onde

d.D

isso

ciat

es a

bove

310

0' F

.

Tab

le 4

-18.

SUM

MA

RY

OF

Arr

ozar

tmot

APP

LIC

AT

ION

S A

ND

lir/

own-

RE

RE

FER

EN

CE

S

APp

licat

iorl

aR

efer

ence

sA

pplic

atio

nsC

atal

ytic

Flam

eC

atal

ytic

Ref

eren

ces

Flam

e

Acr

ylat

e po

lym

eriz

atio

nA

spha

lt bl

owin

g an

d sa

tura

ting*

Aut

omot

ive

pain

t bak

ing

Bak

elite

man

ufac

turi

ngB

ondi

ng a

nd b

unio

n'B

urno

ff o

vens

Car

bon

furn

aces

Che

mic

al p

roce

ssin

gC

.,.'n

e ro

astin

gC

oil a

nd s

trip

coa

ting_

Cor

n po

ppin

gC

upol

a ga

s -

Dee

p fa

t fry

ing

Fabr

ic c

urin

gFi

sh a

nd v

eget

able

oil

proc

essi

ngFo

od p

ro c

eiw

ing

Foun

dry

core

bak

ing

Fung

icid

e m

anuf

actu

reG

rind

ing

whe

el s

inte

ring

Har

dboa

rd c

oatin

g an

d cu

ring

_In

cine

rato

rsK

raft

pap

er m

anus

.-ct

ure

Met

al *

wor

stin

gM

etal

chi

p dr

ying

204

178

Nat

roa

stin

g_20

4

204

Oil

hydr

ogen

atio

n20

4

227

h 20

4, t9

5O

il qu

ench

ing

204

225

Oil

sulf

uriz

atio

n20

417

8, 1

95, 2

2020

4. 2

21".

Pain

t and

var

nish

coo

king

204,

=7

209.

220

.5.

226

204

:78

Pape

r co

atin

g20

4

204.

=17

8P'

harr

nace

utic

al m

anuf

actu

re_

204

294

192,

201

Phth

alic

and

rna

leic

anh

ydri

de m

ann-

18S,

204

. 22?

178,

=0

204.

224

209.

224

fact

ure

204

179

Pota

to c

hip

cook

ing

-20

4

204

Prin

ting

204.

221

209

Ren

deri

ng -

204

204

Res

in m

anuf

actu

ring

and

acr

ylat

e po

ly-

204

'185

185

rner

izat

ion

204

Ric

e br

owni

ng20

4

204

Sew

age

trea

tmen

t20

4

186.

204

Smok

e ab

atem

ent

204

Smok

e ho

uses

194

Stat

iona

ry d

iese

l eng

ines

194.

=7

204

Synt

hetic

rub

ber

man

ufac

ture

204

228

Tar

coa

ting

204

209.

222

Tex

tile

fini

shin

g19

8

185.

204

178

Vita

min

man

ufac

ture

204

204

Wax

bur

nout

, inv

estm

ent c

astin

g18

5. 2

04W

ire

enam

elin

g19

4. 2

04, 2

2717

8, 2

26

178

178

178.

185

178,

=0

203,

229

. 230

!P5,

209

200

Invo

lve*

dis

char

ge o

f pa

rtic

ulat

e m

atte

r.It

alic

ized

ref

eren

ces

cont

ain

quan

titat

ive

data

.

200r`

1900

1800

1700

SILICA1600

BRICK

0,1203 ()

"eS;02 100

a,

SILICIOUS* FIRBRICK - AI.UMINOUS BRICK -BRICKBRICK

10 2090 80

FIG1 RE 4-105.

I I I I I I I30 40 SO 60 70 8070 60 SO 40 30 20

COMPOSITION BY WEIGHT

Degree of refraction for alumina-silica system products.(Coartepy of chernient Engineering Metgn:inej

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1.12

9010

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0

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66. Houghton, H. G. and Radford, W. H. "Measure-ments on Eliminators and the Development of aNew Type for Use at High Gas Velocities."Trans!. Amer. Inst. Chem. Eng., Vol. 35, pp.427-433, May 1939.

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127. -Control of Particulate Emissions." TrainingManual, U.S. Public Health Service, NationalCenter for Air Pollution Control, Cincinnati,Ohio, April 1961.

128. Spaite, P. W., Stephan, D., and Rose, A., Jr."High Temperature Fabric Filtration of In-dustrial Gases." J. Air Pollution Control Assoc.,11(6) :243-247, May 1961.

129. Rosebush, W. H. "Filtration of Aerosols." In:Handbook on Aerosols, U.S. Atomic EnergyCommission, Washington, D.C., Chapt. 9, 1950.Reprinted 1963, pp. 117-122.

130. I,icht, W. "Removal of Particulate Matter fromGaseous Waste.Filtration." Univ. of Cincinnati,Ohio. (Prepared for American Petroleum In-stitute, New York), 1961.

131. Simon, H. "Air Pollution Engineering Manual."County of Los Angeles Air Pollution ControlDistrict, Chapt. 4, Section C. Jan. 1964 (Un-published).

132. Frederick, E R. "How Dust Filter SelectionDepends upon Electrostatics." Chem, Eng., 6r(13) :107-114, June 26, 1961.

139. Silverman, L. "Technical Aspects of With Tem.perature Gas Cleaning for Steel-Making Proc-esses." Air Repair, Vol. 4, p. 159, Feb. 1956.

134. Strauss, W. "Inciultrial GIs Cleaning." Per-gamon Press, London, 1966, No. 8, p. 230.

135. Williams, C. E., Hatch, T. and Greenburg, L."Determination of Cloth Area for IndustrialAir Filters." Heating, Piping, Air Conditioning,Vol. 12, pp. 259-263, April 1940.

136. Stephan, 0. G. and Walsh, G. W. "ResidualDust Profiles in Air Filtration." Ind. Eng.Chem., Vol, 62, p. 999, Dec. 1960.

137. Borgwardt, 11. H. and Durham, J. F. " FactorsAffecting the Performance Fabric Filters-"( Presented at the 60th Annual Meeting, Amer-ican Institute of Chemical Engineers, NewYork, Nov. 29, 1967.)

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139. Stephan, D. G., Walsh, G., and Herrick, R.' Concepts in Fahrie Air Filtration." J. Am.

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142. American Air Filter Co, Inc. Bulletin 279E,Louisville, Ky., Feb. 1967,

143. Hersey, H. J., Jr. "R-tverse-Jet Filters." In-dustrial Chemist, Vol. 31. p. 362, March 1955.

141. Adams, R. L. "High Temperature Cloth Col-!cetera." Chrm. Eng. Proc., 6*(4) :67, April1966.

145. Culhane, F. R. "Air Pollution Control Produc-tion Doghouses." Chem. Eng. Prog., 44(1) :65,Jan. 1968.

146. "The MikroPulsaire Dust C.Iloctor." Slick In-dustrial Co., Bulletin PC-2, Pulverizing Ma-chinery Div., Summit, N.J., 1967, p. 9.

147. French. R. C. -Filter Media." Chem. Eng., 70-(21) :171-192, Oct. 14, 1963.

148. Gusman, I. J. and Hatton, R. C. "Fiber GlassFabric Filters for High Temperature Dust antsFume Control." J. Air Pollutism Control Assoc.,14(6):266-267, June 1963.

149. "Engineering Fabrics for Industry." Welling.ton Sears Co., West Point-Pepperall inc, NewYork, 1966, p. 7.

150. Spaite, P. W., Hagan, J. E., and Todd, W. F."A Protective Finish for Glass-Filer Fabrics."Chem. Eng. Frog.. 39(4):5447, April 1963.

151. "Carter Day Dust Filter, Type CS." CarterDay Co., Dulletin L-1120R2, Minneapolis,Minn., June 1968.

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153. Sommerlad, R. E. "Fabric Filtration, State ofthe Art." (Presented at Electric GenerationSeminar on Air Pollution, the Graduate School,U S. Dept. of Agriculture, March 6, 1967.)(Available from Foster Wheeler Corp., Livings-ton, NJ.)

154. "Dust Collection with Fabric of NornezPit-liminary Information." E. 1. DuPont Co., Bul-letin No. 87, Wilmington, Delaware, Aug. 1,1966.

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157. Chase, F. 11. "Application of Self-ContainedDust Collectors." (Presented at the 12th An.twat Michigan Industrial Ventilation Confer-ence, Michigan State University, East Lans-ing, Alich., 1963.) (Available from Torit Manu-facturing Co., 1.133 Rankin St., St. Paul, Minn.)

158. "Southwestern Portland Filters Hot KilnGases." Pit and Quarry, Oct. 1968.

159. :ones, A. 14. "Ho* to Get Your Mo4ey's WorthWhen Drying and Its:talling Cloth Dust Col-lection Equipment." (Presented at the RockProducts Seminar, Chicago, 111., Nov. 27, 1967.)

160. Kreichelt, '1'. K, Kemnitz, D. A., and Cut Te,S. T. "Atmospheric Emissions from the Maim-facture of Portland Cement." U.S. Dept. ofHealth, Education, and Welfare, National Cen-ter for Air Pollution Control, Cincinnati, Ohio,PHS-Pub 999-AP-17, 1967.

161. Harrison, B. P., Jr. "Baghouse Cleans 500°Cement Kiln Gases." Air Eng., 5(3):14-16,March 1963.

162. Spaite, P. W.. Stephan. D. 0.. and Rose. A. H..Jr. "High Temperature Fabric Filtration ofIndustrial Gases." J. Air Pollution ControlAssoc., 11(6) :243.258, May 1961.

163. Adams, R. L. "Application of Baghouses toElectric Furnace Fume Control." J. Air Pollu-tion Control Assoc., 14(81:299-302, Aug. 1964.

164. Herrick. R. A. "A Baghouse Test Program forOxygen Lanced Open Hearth Fume Control."J. Air Pollution Control Assoc., JIM t2g-32.Jan. 1963.

165. Hetrick. R. A.. Olsen, 3. W.. and Ray. F. A."Oxygen-Lanced Open Hearth Furnace FumeCleaning with a Glass Frhric Doghouse." J.Air Pollution Control Assoc.. 14(1) :7-10, Jar,.1966.

166. Drogin. I. "Carbon Black." J. Air Pollution Con-trol Assoc.. 14(4) :216-228. April 1968.

167. Cote, W. A. 'Grain Dust Emissions and OurAtmosphere." Proc. National Symposium on AirPollution, Washington. D.C., Jan. 11-12, 1967,pp. 65-74.

168. Noland. R. "Technological Developments inPlant and Equipment Designs tot' Air PollutionControl." Proc. National Symposium on AirPollution. Washington. D.C., Jan. 11-12. 1967,pp. 81-92.

169. "Aerotron Dust Collectors. Type B." BuffaloForge Co. Bulletin AP654. Buffalo, New York.Dec. 1962.

170. Thomas. N. J. "Auto-Ignition Temperatures ofFlammable Liquids" /rid. Eng. Chem.. 1/(2):134-139. Feb. 1929.

171. Kobayashi. K. -Combustion of a Fuel Droplet."In: Fifth Symposium on Combustion. Pitts-burgh, Reinhold Publishing Co. New York.Pub. No. 1936, 19$4, pp. 141-148.

172. Spaulding. D. D. "Heat and Mass Transfer inthe Combustion of Liquid Fuels." AmericanSociety of Mechanical Engintera. published bythe Institution of Mechanical Engineers. Story'sGale. London. England, Sept. 11 -13. 1951. pp.345-348.

173. Hottel, H. C. Williams. G. C. and Simpson.H. C. "Combustion of Droplets of Heavy Liq-uids Feels." In: Fifth Symposium on Combus-tion Pittsburgh, Reinhold Publishing Co- NewYork. Pub. No. 1933. 1954. pp. 101-129.

174. Nithiwaki, N. -Kinetics of Liquid CombustionProcesses. Evaporation and Ignition Lag ofFuel Droplets." In: Fifth Symposium on Com-bustion, Pittsburgh, Reinhold Publishing Co..New York, Pub. N'o. 1933, 1954, pp. 148-158.

a

175. Orning, A. A. "Combustion of Pulverized Fuel-Mechanism and Rate of Combustion of LowDensity Fractions of Certain BituminousCoals." Trans. Am. Soc. Mech. Eng., Vol. 61,pp. 997-508, 1942.

176. Griffiths, J. C.. Thompson, C. W., and Weber,E. J. "New or Unusual Burners and Combus-tion Processes." American Gas Assoc. Labora-tories. Research Bulletin 96, pp. 18-28, 83, Aug.1963.

177. Innes, W. B.. and Duffy, R. "Exhaust Gas Ox-idation on Vanr.diaAlumina Catalyst." J. AirPollution Control Assoc.. 11(8):3b3 -373, Aug.1961.

178. Decker. L. D. "Odor Control by Incineration."Universal Air Products Div. Form No. 6-048,p. 16. (Presented at Middle States Air PollutionControl Association, Wilmington. Del., Nov.1965.)

179. "Catalyst Deactivation and Poisoning Agents."Universal Oil Products, Air Correction Div.Form No. 6-039.

180. Topper. I,. -Radiant Heat Transfer fromFlames in a Turbojet Combustor." Ind. Eng.Chem.. 46(12) :2551-2558. Dec. 1954.

181. Eckert, E. R. G. and Drake, R. M.. Jr. "Heatand Mass Transfer." 2nd edition, McGraw-Hill,New vork. 1959. 630 pp.

182. Trinks. Of. and Keller. 3. D. "Tests of Radiationfrom Luminous Flames." Trans. American So-ciety Mechanical Engineers, Vol. 68, pp. 203-210. 1936.

183. Sherman. R. A. "Radiation from Luminous andNon-Luminous Natural Gas Flame." Trans.American Society Mechanical Engineers, Vol.66. pp. 177-185. 1934.

184. Thring, M. W. "The Radiative Properties ofLumirous Flames.' In: Proceedings of the In-ternational Heat Transfer Conference. Aug.1960. pp. 101-111.

185. Danielson, 3. A. (ed.) "Air Pollution Engineer-ing Manual." U S. Public Health Service, Na:tional Center for Air Pollution Control.

Ohio. PHS Pub-999-AP-40. 1967. pp.171-193.

186. Yagi. Sakae and Kunii. D. 'Combustion of Car-bon Particles in Flame's and Fluidised Beds."in: Fifth Syropistrn on Combustion. Pitts-burgh. Reinhold Publishing Company, NewYork. 1954. pp. 231-44.

187. Browning. 3. A.. Tyler. T. L. and Km. W. G."Effect of Particle Site on Combustion of Uni-form Suspensions." Ind. Eng, Chem.. 45(l):142-147. Jan. 1937.

188. Godsave, G. A. E ''Studies of the Combustion ofDrops in a Fuel Spray -'The Burning of SingleDrops of Feel." In: Proceedings of the 4thSymposium on Combustion. Cambridge. Mass-Williams and Wilkins Co,. Baltimore, M.i., Pub.No. 1933, Sept. 1932. pp. 818430.

it,. Gregory. C. A., Jr. and Cakote. H. F. "Comb,,s-lion Studies of DropletVapor Systems." In:

147

Proceedings of the 4th Symposium on Combus-tion. Cambrige. Mass.. Williams and WilkinsCo.. Baltimore. Mil. Pub. No. 1953. Sept, 10u2.pp. 830-837.

190. Smith. D. F. and Guttmundsen, A. -Mechanismof Combustion of Individual Particles of SolidFuels." Ind. Eng. Chem., 2.1(3) :277-285 March1931.

191, Parker. A. S. and liottel, H. C. "CombustionRate of Carbon.- Ind. Eng. Chem 28 (11):1334-1341, Nov. 1936.

192. Krenz, W. B.. Adrian. IL C.. and Ingels. R. M."Control of Solvent Losses in Los Angeles Coun-ty." (Presented at the 50th Annual Meeting ofthe Air Pollution Control Association. St. Louis.Mo., June 5, 1967.)

193. Miller, M. R. and Wilhoyte, H. J. "A Study ofCatalyst Support Systems for Fume-Abatementof Hydrocarbon Sol-ents." J. Air Pollution Con-trol Assoc.. 17(12) :791-795, Dec. 1967.

194. Volheim. G. "The Catalytic Afterburning ofIndustrial Effluents." 25(11) :20-26, Nov. 1965.

195. Gamble, B. L. "Control of Organic SolventEmissions in Industry." Paper 68-48, 61st An-nual Meeting, Air Pollution Control Assoc.. St.Paul, Minnesota, June 23-27, 1968.

196. Field, M. A.. Gill. D. W Morgan, B. B. andHawksley. P. G. W. "Combustion of PulverizedCoal." British Coal Utilization Research As-sociation, Leatherhead, England, 1967, 413 pp.

197. Mills, J. L., Hammond, W. F., and Adrian, R.C. "Design of Afterburners for VarnishCookers." (Presented at the 5 ?nd Annual Meet-ing of the Air Pollution Control Association,Los Angeles, Calif., June 1959.) J. Air Pollu-tion Control Assoc., Vol. 10, pp. 161-168, 1960.

198. Thring, M. W. "The Science of Flames andFurnaces." 2nd edition John Wiley and Sons,1962, 625 pp.

199. Benforado, D. M., Paulette, C. E., and Hazzard,N. D. "Economics of Heat Recovery in Direct-Flame Fume Incineration." Air Eng., Vol. 9, pp.29-32, March 1967.

200, Sandomirsky, A. G., Benforado, D. M., Grames,L. D. and Paulette, C. E. "Fume Control ;nRubber Processing by Direct-Flame Incinera-tion." J. Air Pollution Control Assoc., 16(12):673-676, Dec, 1966.

201. Myers, F. D., and Waitkus. J. "Fume Incinera-tion with Combustion Air at Elevated Temper-tures." J. Air Pollution Control Assoc., 16(7):378-382, July 1966.

202, Trinks, W. and Mawhinney, M. H. "IndustrialFurnaces," 5th edition Vol. I, John Wiley andSons, 1961, 486 pp.

203. Perry, R. H.. Chilton, C. H. and Kirkpatrick,S. D. "Chemical Engineers' Handbook." 4thedition, McGraw-Hill, 1963, 1911 pp.

204. "Catalytic Combustion Systems for Ovens andDryers." Universal Oil Products Bulletin 602,Air Correction Division, 11 pp.

148

205. Goodel P. H. "Industrial Ovens Designed forAir Pollution Control." J. Air Pollution ControlAssoc.. Vol. 10, pp. 234-238, 1960, (Presentedat the 52nd Annual Meeting of the Air PollutionControl Association, Los Angeles, Calif., June22-26, 1:)59.)

206. Vamlaveer, F. E. and Sedeler, C. G. "Combus-tion of Gas." American Gas Assoc.. Inc.. NewYork, 1965, 53 pp.

207. Ingels, It M. "The Afterburner Route to Pol-lution Control.- Air Eng.. No. 6. pp. 39-42,June 1964.

208. Ruff'. R. J. 'Profits from Waste Gases Reprint.Catalytic Combustion, Detroit. Mich., 4 pp.

209. Caplan, K. J. (ed.) "Air Pollution ManualPart IIControl Equipment." American In-dustrial Hygiene Association, Lansing, Mich.,19E8. pp. 112-135.

210. DeHaas, G. G., and Hansen, G. A. "The Abate-ment of Kraft Pulp Mill Odors by Burning."TA PP!. 38(12):732-738, Dec. 1955.

211. Industrial Air Pollution Control. Sly Manu-facturing Co., Cleveland, Ohio. Bulletin 204,1967, 35 pp.

212. Weil, S. A. "Burning Velocities of HydrocarbonFlames." Inst. Gas Tech., Chicago, Illinois, Re-search Bulletin 30, 1961, 48 pp.

213. "Standards for Ovens and Furnacee." NationalBoard of Fire Underwriters," NBFU No. 864,Aug. 1963.

214. Radier, H, H. "Flame Arrestors." J. Inst. Petr.,Vol. 25, pp. 377-381, 1939.

215. "Industrial VentilationA Manual of Recom-mended Practice." 10th edition, American Con-ference of Governmental Industrial Hygienists,Lansing, Mich., 1968, 150 pp.

216, Barr, J. "Diffusion Flames." In: F ..oceedings ofthe 4th Symposium on Combustion, Cambridge,Mass. Williams and Wilkins Co., Baltimore,Maryland, 1952, pp. 765-771.

217, Griffiths, J. C. and Weber, E. V. "Influence ofPort Design and Gas Composition on FlameCharacteristics of Atmospheric Burners."American Gas Association Laboratories, Cleve-land, Ohio, Research Bulletin 77, 1958. 63 pp.

218. "Standards for SafetyCommercialIndus-trial Gas Heating EquipmentUL. 795." Un-derwriters Laboratories, Nov. 1952, Revised1969.

219. Burst, J. r., and Spieckerman, J. A. "A Guideto Selecting Modern Refractories." Cnem. Eng.,74(16) :85-104, July 1967.

220, Benforado, D. M. "Air Pollution Control byDirect Flame Incineration in the Paint Indus-try." J. Paint Tech., 39(508) :265-266, May1967.

221. Wallach, A. "Some Data and Observations onCombustion of Gaseous Effluents from BakedLithograph Coatings." J. Air Pollution ControlAssoc., 12 (3) :109-110, March 1962.

V"?

222. Beriforado. 1). M. and Cooper, 0. -The Applica-tion of Direct-Flame Incineration r s an OdorControl Process in Kraft Pulp Mills." Preprint.(Presented at the 22nd Engineering Confer-ence, Process Systems and Controls. Water andAir Pollution. TAPPI, Atlanta. Ga., Sept. 19-22, 1967.)

223. Banner. A. P.. and Ilgenfritz. E. M. -Disposalof Coal Tar Pitch Distillate Obtained from Car-bon Baking Furnace by Catalytic Combustion."J, Air Pollution Control Assoc., 1.3(12) :616-612,Dec. 1963.

224. Sullivan. J. L. "An Evaluation of Catalytic andDirect Fired Afterburners for Coffee and Chic-ory Roasting Odors. J. Air Pollution ControlAssoc., 15(12) :583-586. Dec. 1965.

225. Jares, J. "Fume Oil and Varnish Disposal byCombustion." Chem. Eng.. Vol. 56, pp. 110-111.Jan. 1949.

226. Benforado, D. M. and Waitkus, J. "Exploringthe Applicability of DirectFlame Incinerationto Wire Enameling Fume Control." Wire Prod.,Vol. 42, pp. 1071-1978. 1967. (Presented beforethe Electrical Conductor Division of the WireAssociation, Chicago, Illinois, Oct. 23, 1937.)

227. Moody. R. A. "Examples of Catalytic After-burning in Stationary Installations and MotorVehicles." Staub. 25 (11) :26-30, Nov. 1965.

228. Truitt. S. M. 'The Application of Gas BurnerEquipment for Elimination of Smoke andOdors from Flue-Fed Incidera tors." NorthAmerican Manufacturing Co., Cleveland, Ohio,Reprint CB- 552- 44 -I). 4 pp.

229. McKenzie, D. "Burn Up Those Lift-StationOdors." North American Manufacturing Co.,Cleveland, Ohio.

230. Bailey. J. M. and Reed, R. J. "Fume Disposalby Direct Flame Incineration." North AmericanManufacturing Co.. Cleveland. Ohio.

149

tat*

5. EMISSION FACTORS FOR PARTICULATE AIR POLLUTANTS

An emission factor is a statistical averageof the rate at which pollutants are emittedfrom the burning or processing of a givenquantity of material. Emission factors canalso be established on the basis of some othermeaningful parameter, such as the numberof miles traveled in a vehicle. To determineemission factors, available reliable data onemissions from a particular source or groupof sources are gathered and correlated withinformation on process use. The individualemission factors derived are tabulated, andeither an average or a range of values isselected for use.

Some emission factors are based on verylimited data; others are based on extensivedata that are highly variable; and still othersare based on extensive, consistent data. It is,

therefore, important that the accuracy ofthe data on which an emission factor is basedbe evaluated before the factor is used for esti-mating emissions.

In general, the emission factors for particu-late air pollutants are not precise indicatorsof what particulate emissions might be fromany single process even though all the de-tails of the process are known. Emission fac-tors are more valid when applied to a num-ber of processes.

Emission factors listed in Table 5-1 aretaken from Compilation of Air PollutantEmission Factors, Public Health Service pub-lication No. 999-AP-42, except where noted.The factors are for uncontrolled sources ex-cept as qualified in the table. Examples ofhow emission factors are used follow.

Table 5-1.PARTICULATE EMISSION FACTORS'

Source Particulate emission rate

Fuel combustionstationary sources:Coal:

Pulverized:General (anthracite and bituminous)Dry bottom (anthracite and bituminous)Wet bottom (anthracite and bituminous):

Without fly ash reinjectionWith fly ash reinjection

Cyclone (anthracite and bituminous)Spreader stoker (anthracite and

bituminous) :Without fly ash reinjectionWith fly ash reinjection

All other stokers (anthracite andbituminous):

Greater than 10X10' Btu/hrLess than 10X101 Btu/hr

Hand-fired equipment (bituminous coal only)Residual oil:

Greater than 100X10' Btu/hrLess than 100X104 Btu/hr

Distillate oil:10 to 100X10' Btu/hrLess than 10X10' Btu/hr

150

16Ab tb/ton of coal burned17A lb/ton of coal burned

13A lb/ton of coal burned24Ac lb/ton of coal burned2A4 lb/ton of coal burned

13A lb/ton of coal burned20Ac lb/ton of coal burned

5A lb/ton of coal burned2A4 lb/ton of coal burned20 lb/ton ,.)f coal burned

10 lb/1000 gallons of oil burned23 lb/1000 gallons of oil burned

15 lb/1000 gallons of oil burned8 lb/1000 gallons of oil burned

Table 5-1 (Con linuA).PARTICULATE EMISSION FACTORS'


Fuel combustionstationary sources (continued) :Natural gas:

Greater than 100X 10' litu/hr10 to 100X10' ritu/hrLess than 10X10' litu/hr

Wood'Fuel combustionmobile sources:

Gasoline - powered motor vehicleDiesel-powered vehicleAircraft:

Jet (fan-type) :4 engine ....3 engine2 engine1 engine

Jet (conventional) :4 engine3 engine2 engine1 engine

Turboprop:4 engine2 engine

Piston:4 engine2 engine1 engine

Solid waste disposal:Open burning of leaves and brushOpen-burning dumpMunicipal incinerator

On-site commercial and industrial multiplechamber incinerator(Los Angeles design)

Single-chamber incineratorDomestic gas-fired incineratorOn-site residential flue-fed incineratorProcess industries(specific examples) :

Chemical industry:Paint and varnish manufacture:

Varnish cookerAlkylresin productiontotal operationCooking and blowing of oilsHeat polymerization acrylic resins

Phosphoric acid manufacturethermal process absorber tailgas with control (acid mist).

Sulfuric acid manufacturecontact process (acid mist)Food and agriculture industries:

Coffee roasting:Direct fired roasterIndirect fired roasterStoner and cooler.Instant coffee spray dryeralways controlled with

cyclone and wet scrubber.Cotton ginning operation (includes cotton gin and incinera-

tion of cotton trash).Feed and grain mills:

General with 90 percent efficient cyclonesWheat air cleaner with cyclone

15 lb/million ft of gas burned18 lb/million ft of gas burned19 lb/million ft of gas burned10 lb/ton of wood burned

12 110000 gallons consumed110 111/1000 gallons consumed

7.4 lb/flight5.6 lb/flight3.8 lb/flight1.9 lb/flight

34.0 lb/flight25.5 lb/flight17.0 lb/flight8.5 lb/flight

2.5 lb/flight e0.6 lb/flight

1.4 lb/flight e0.6 lb/flight0.3 lb/flight

17 lb/ton of refuse burned16 lb/ton of refuse burned17 lb/ton of refuse burned

3 lb/ton of refuse burned10 lb/ton of refuse burned15 lb/ton of refuse burned28 lb/ton of refuse burned

60-120 lb/ton of feed80-120 lb/ton of feed20-60 lb/ton of feed20 lb/ton of feed0.2-10.8f lb/ton of phosphorus burned

0.3-7.5 lb/ton of acid produced

7.6 lb/ton of green beans4.2 lb/ton of green beans1.4 lb/ton of green beans1.4 lb/ton of green beans

11.7 lb/bale of cotton (500 lb)

6 lb/ton of product0.2 lb/ton of product

151

Table 5-1 (Continued).PARTICATIATE EMISSION FACTORS'

Source Particulate emission rate a

Feed and grain mills (continued) :Barley flour mill with cycloneAlfalfa meal mill with settling chamber and cycloneOrange pulp dryer with cyclone

Starch manufacturenatural gas directlired flash tinier .

Primary metal industry:Iron and steel manufacture:

Sintering machine gasesSinter machine discharge

Open hearth furnace:Oxygen lanceNo oxygen lance

Basic oxygen furnace sElectric arc furnace:

Oxygen lancesNo oxygen lances

Blast furnace:Ore chargingAgglomerate charging

ScarfingCoking operationscharging, pushing, quenching

Secondary metal industry:Aluminum smelting:

Chlorinationlancing of chlorine gas into moltenmetal bath

Crucible furnaceReverberatory furnaceSweating furnace

Brass and bronze smelting:Crucible furnaceElectric furnaceReverberatory furnaceRotary furnace

Gray iron foundry:CupolaElectric induction furnaceReverberatory furnace

Lead smelting:CupolaPot furnaceReverberatory and sweating furnace

Magnesium smelting: Pot furnaceSteel foundry:

Electric arc furnaceElectric induction furnaceOpen hearth furnace

Zinc smelting:Galvanizing kettlesCalcine kilnsPot furnacesSweating furnace

Mineral product industry :Asphalt saturatorsAsphalt batch plantrotary drierCalcium carbide plant:

Coke dryerElectric furnace hoodFurnace room vents

3.1 lb/ton of product1.0 lb/ton of product

lb/ton of product8 lb/ton of starch

...

15:2

20 11)/ton of sinter22 lb/ton of sinter

22 Ilt/ton of steel14 11)/ton of steel-16 lb /ton of steel

11 11)/ton of steel7 11)/ton of steel

110 11)/ton of iron40 lb; ton of iron3 lb/ton of steel processed2 lb/ton of coal

1000 lb/ton of chlorine used1.9 lb/ton of metal processed4.3 lb /ton of metal processed32.2 lb/ton of metal charged

:1.9 lb/ton of metal charged3.0 lb/Lon of metal charged26.3 lb/ton of metal charged20.9 lb/ton of metal charged

17.4 lb/ton of metal charged2.0 lb/ton of metal charged2.0 lb/ton of metal charged

300 lb/ton of metal charged0.1 lb/ton of metal charged154 lb/ton of metal charged4.4 lb/ton of metal charged

15.0 lb/ton to metal charged0.1 lb/ton of metal charged10.6 lb/ton of metal charged

5.3 lb/ton of metal charged88.8 lb/ton of metal charged0.1 lb/ton of metal charged10.8 lb/ton of metal charged

3.9h lb/ton of asphalt5.0 lb/ton of mix

0.2 lb/ton of product1.7 lb/ton of product2.6 lb/ton of product

Table 5-1 (Continued).PARTICULATE EN1ISSION FACTORS'


Secondary metal industry (continued) :Calcium carbide plant (continued):

Main stack (vents to atmosphere) exhaust from fur-nace hoods always passes through impingementscrubbers

Cement manufacture:Dry processkilnWet processkiln

Ceramic and clay processes:Ceramic clayspray drier with cycloneBisque with scrubberCatalytic materialdried, kiln and cooler with cyclone

and scrubberConcrete batch planttotal operationFrit manufacturefrit smeltersGlass manufacturesoda-lime process with direct fired

continuous melting ...Lime production:

Rotary kiln .....

Vertical kiln ................ ..........Per lite manufactureexpanding furnace

Rock wool manufacture:CupolaReverberatory furnace .

Blow chamberCuring ovenCooler

Rock, gravel and sand production:CrushingConveying, screening. shakingStorage pileswind erosion

Petroleum industry:Fluid catalytic crackersMoving bed catalytic crackers:

TCC-type unitHCC-type unit

Kraft pulp industry:Smelt tank:

UncontrolledWater spray::esh demister

Lime kilnRecovery furnace with primary stack gas scrubber

........

........ ..........

......... ........ .................

2M Ili/ton of product

16 lb/loarrel of cementlb /barrel of cement

15 lb/ton of charge2 lb/ton of charge

6 lb /ton of charge0.2 lb /yard of concrete1615 lb/ton of charge

2.0 lb/ton of glass

200 lb/ton of lime20 lb/ton of lime21 lb/ton of chary

21.6 lb/ton of charge4.8 lb/ton of charge21.6 lb/ton of charge3.6 lb/ton of charge2.4 lb/ton of charge

20 lb/ton of product1,7 lb/ton of product20 lb/ton of product

0.1 to 0.21 lb/ton of catalyst circulated

0.05 to 0.151 lb/ton of catalyst circulated0.15 to 0.25/ lb/ton of catalyst circulated

20 lb/ton of dry pulp produced5 lb/ton of dry pulp produced1-2 lb/ton of dry pulp produced94 lb/ton of dry poll_ produced150 lb/ton of dry pulp produced

& Emission sates are those from uncontrolledsources, unless otherwise noted.

b Where letter A is shown, multiply number givenby the percent ash in the coal.

c Value should not be used as emission factor. Values represent tho loading reaching the control equip-ment always used on this type of furnace.

d Revised from 5A.e Flight is defined as a combination of a landing

and a takeoff.

Depends on type of control.

g Based on data from NAPCA Contract No. PH22-68-65.

h Includes only solid particulate matter. In addi-tion, about 65 lb/hr of oil mist may be evolved fromasphalt saturators.

Revised from 0.1.

i Revised from 0.04.

153

Coal Combust ion

Given: Source burns 10,000a spreader stokerinjection,85 percent efficientAsh content-10pressed as the numberthe computation).

From Table 5-1:Emision factor = 13A

coal, where A equals ashTherefore:

Particulate emissions.(Emission factor) Collectionfactor)

Particulate emissions,tone of coal]

tons per yearwithout fly ash

multiple cyclones,percent (Note:

10 in making

pounds per toncontent.

(Process weight)efficiency

particulate

pounds of particulate

per-

of

in tons of refusere-

=6,000pounds of particulate

year

Ex-Process Industries

Given: Secondary brass and bronze smeltingoperation with fabric filter 99

cent efficientof Furnace typeelectric.

Metal charged into furnace-20,000tons per year

From Table 5-1:

Emission factor .3 pounds per tonmetal charged

Therefore:Particulate emissions=

tons of metal charged

year

[ (13) (10)pounds of

[20,000tons of coal yearpounds of particulate pounds of particulate[1-0.85] =195,000 [1-0.99]year .

[ 30

tons of metal chargedSolid Waste DisposalGiven: Commercial operation burning 2,000

tons per year of refuse in multiple-cham-ber incinerator.

From Table 5-1:Emission factor-3 pound per ton of ref-

useTherefore:

Particulate emissions =

tons of refuse]year

154

=600 pounds of particulateyear

REFERENCES FOR SECTION 5

1. Duprey, R. L. "Compilation of Air PollutantEmissions Factors." U.S. Dept. of Health, Edu-cation, and Welfare, National Center for AirPollution Control, Durham, N.C., PHS-Pub-999-AP-42, 1968.

2. 'Procedure for Conducting Comprehensive AirPollution Surveys." New York State Dept. ofHealth, Bureau of Air Pollution Control Serv-ices, Albany, New York, Aug. 18, 1965.

6. ECONOMIC CONSIDERATIONS IN MR POLLUTION CONTROL

6.1 SELECTION OF CONTROL SYSTEM

Most air pollution emission control prob-lems can be solved in several ways. In orderto select the best method of reducing pol-lutant emissions, each solution should bethoroughly evaluated prior to implementa-tion. Steps such as substitution of fuels amiraw materials and modification or replace-ment of processes should not be overlookedas possible solutions. Such emission reduc-tion procedures often can improve more thanone pollution problem. For example, particu-late matter and sulfur oxides emissions bothmay be reduced by switching from high-sul-fur coal to natural gas or low-sulfur oil.Such steps also may have the benefit of re-ducing or eliminating solid waste disposaland water pollution problems. Often it ischeaper to attack two air problems togetherthan to approach each problem individually.If steps such as process alterations and sub-stitution of fuels are not feasible, it may benecessary to use gas cleaning equipment.

Figure 6-1 shows the factors to be con-sidered in selecting of gas cleaning system.The first consideration is the degree of re-duction of emissions which may be requiredto meet emission standards. The degree ofemission reduction or the collection efficiencyrequired is dependent upon the relationshipbetween emissions and emission standardsas shown at the top of the figure. This is animportant factor in making the choice amongcontrol equipment alternatives. Although acontrol system may include two or morepieces of control equipment, collection effi-ciency, as used in this chapter, applies to in-dividual pieces of control equipment. The us-ual ranges of collection efficiency for variousequipment alternatives are shown in Table6-1. The important factors to be considerednext are the gas stream and particle char-acteristics of the process itself, as shown inthe center of Figure 6-1. High gag temper-

Table 6-I.AIR POLLUTION CONTROLEQUIPMENT COLLECTION EFFICIENCIES '''

Efficiency Range(on a total

Equipment type weight basis)percent

Electrostatic precipitator a 80 to 90.5+Fabric filters b 95 to 99.9Mechanical collector 50 to 95Wet collector .. . 75 to 99+Afterburner:

Catalytic c 50 to 80Direct flame 95 to 99

Most electrostatic precipitators sold today aredesigned for 98 to 99.6 percent collection efficiency.

b Fabric filter collection efficiency is normallyabove 99.5 percent.

c Not normally applied in particulate control; haslimited use because most particulates poison or de-sensitize the catalyst.

atures without cooling, for example, precludethe use of fabric filters; explosive gasstreams prohibit the use of electrostatic pre-cipitators; and suirmicron particles cannotgenerally be efficiently collected with mechan-ical collector. A number of factors that re-late to the plant facility should also be con-sidered, some of which are listed in Figure6-1. Each alternative will have a specific costassociated with it, and the components ofthis cost should be carefully examined. Thosealternatives which meet the requirements ofboth the process and the plant facility canthen be evaluated in terms of cost; on thisbasiF the gas cleaning system may be se-lectee.

6.2 COST-EFFECTIVENESSRELATIONSHIPS

Meaningful quantitative relationships be-tween control costs and pollutant reductionsare useful in assessing the impact of co;i-trol on product prices, profits, investments,and value added to the product. With such

Value added is generally considered to be theeconomic worth added to a product by a particularprocess, operation, or function'

155

EMISSIONS AND EMISSIONSSTANDARDS

DETERMINES COLLECTION EFFICIENCY

CONTROL EQUIPMENT ALTERNATIVES

ELECTROSTATICPRECIPITATOR

GAS STREAMCHARACTERISTICS

VOLUMETEMP ERATUREMOISTURE CONTENTCORROSIVENESSODOREXPLOSIVENESSVISCOSITY

WETCOLLECTOR

DR:jCOLLECTOR

CENTRIFUGAL

PARTICLECHARACTERISTICS

AFTER-BURNER

PROCESS

IGNITION POINTSIZE DISTRIBUTIONABRASIVENESSHYGROSCOPIC NATUREELECTRICAL PROPERTIESGRAIN LOADINGDENSITY AND SHAPEPHYSICAL PROPERTIES

WASTE TREATMENTSPACE RESTRICTIONPRODUCT RECOVERY

PLANTFACILITY

WATER AVAILABILITYFORM OF HEAT RECOVERY

(GAS OR LIQUID)

ENGINEERING STUDIESHARDWAREAUXILIARY EQUIPMENTLANDSTRUCTURESINSTALLATIONSTART-UP

156

COST OFCONTROL

4

POWERWASTE DISPOSALWATERMATERIALSGAS CONDITIONING!LABORTAXESINSURANCERETURN ON INVESTMENT

wwwwIrle

SELECTEDGAS CLEANING SYSTEM

DESIRED EMISSION RATE

FIGURE U-1. Criteria for selection of gas cleaning equipment.

relationships at hand the alternates for so-lution of an air pollution problem can beevaluated for move effective program imple-mentation by the user of the control equip-ment and by the enforcement agency. Thesecost-effectiveness relationships sometimesare applied collectively to a meteorologicalor air quality control region, where they de-scribe the total cost impact on polluters asa result of controlling sources; the discus-sion here, however, centers around cost-effec-tiveness as applied to an individual source.Cost-effectiveness is a measure of all coststo the firm associated with a given reduc-tion in pollutant emissions. For computingthe costs for a given system, one should con-sider ( 1) raw materials and fuels used inthe process, (2) alterations in process equip-ment, (3) control hardware and auxiliaryequipment, and (4) disposal of collectedemissions.

Figure G -2 shows an example of a theo-retical cost-effectiveness relationship.' Theactual total costs of control may depart fromthis curve because some cost elements, suchas research and development expendituresand fixed charges (taxes, insurance, depre-ciation) are not directly related to the oper-ation of the equipment and to the level ofemissions in a given year. The cost of con-trol is represented on the vertical axis andthe quantity of pollutants emitted on thehorizontal axis. Point P indicates the uncon-trolled state, in which there are no controlcosts. As control efficiency improves, the

.1410.

QUANTITY OF POLLUTANTS

FicVnn 6-2, Cost of control.

quantity of emissions is reduced and the costof control increases. In most cases, the mar-ginal cost of control is smaller at the lowerlevels of efficiency, near point P of the curve.The curve also illustrates that as the cost ofcontrol increases, greater increments of costusually are required for corresponding incre-ments of emission reduction. Process changessometimes may result in emission reductionwithout increased costs. Research and de-velopment expenditures resulting in new orimproved equipment design, improved proc-ess operations, or move efficient equipmentoperations will improve the economics ofcontrol. All these factors may substantiallyreduce control costs at most emission levelsand shift the cost of the control curve (CC)as illustrated by CC, in Figure 6-3. Notethat as control technology develops, the costof attaining a desired emission level will bereduced from C to C,,.

Cost-effectiveness information is useful inemission control decision making. Severalfeasible systems usually are available forcontrolling each source of emissions. In mostcases, the least-cost solution for each sourcecan be calculated at various levels of con-trol. After evaluating each alternative andafter considering future process expansionsand more rigid control restrictions, sufficientinformation should be available on which tobase an intelligent control decision.

Cost-effectiveness relationships vary fromindustry to industry and from plant to plantwithin an industry. The cost for a given

Ca

Cb

I-ces

O

q

QUANTITY OF POLLUTANTS

FIGURE 6-3. Expected new cost of control.

157

control system is significantly dependent onthe complexity of the installation and thecharacteristics of the gas stream and pol-lutant. Geographical location is another sig-nificant factor that influences the total an-nual cost; for example, the components ofannual cost, such as utilities, labor, and theavailability of desired sites for waste mate-rial, vary from place to place.

6.3 COST DATA

It is the purpose of this chapter to de-velop basic information and techniques forestimating the costs of installing and operat-ing control equipment. Such information canbe useful in developing cost-effectiveness re-lationships for application of various con-trol systems.

The control cost information included inthis chapter is based on experience, a care-ful study of the literature, and a survey ofmore than 250 suppliers, users, installers,and operators of air pollution control equip-ment. The cost information was reviewed bya panel from the gas cleaning equipment in-dustry for reasonableness of data and meth-odology. The cost data reported reflects 1968prices, except as noted.

6.4 UNCERTAINTIES IN DEVELOPINGCOST RELATIONSIIIPS

Cost information for control devices is in-dicated in Section 6.7 where, for varioustypes of equipment, operating capacity isplotted against cost. The upper and lowercurves indicate the expected range of costs,with the expected average cost falling ap-proximately in the middle. Although quan-titative values for collection efficiency andgas volume capacity are not listed, highercollection efficiency, which involves more in-tricate engineering design, results in hithercosts. Control equipment is designed for anominal gas volume capacity, but under ac-tual operating conditions the volume mayvary. Similarly, the efficiency of controlequipment will vary from application to ap-plication as particle characteristics, such aswettability, density, shape, and size distri-bution, differ. For example, a control devicedesigned to operate on 50,000 acfm of gaswith a nominal collection of 95 percent mayhave an effective operating range of from45,000 to 55,000 acfm, and its collection effi-ciency may range from 90 to 97 percent.

The effect of these independent variationsis to make single point estimates of cost ver-

Table 6-2.-APPROXIMATE COST OF WET COLLECTORS IN 1965°

Type of collectorCost, dollars/cfm

Capacity, cfm

1,000 5,000 20,000 40,000

Cyclonic: b. aSmall diameter multiples 0.50 0.30 0.20 0.20Single chamber, constant water level 1.40 0.45 0,55 0.26Single chamber, multiple stage, overhead line pressure

water feed.0.95 0.40 0.25 0.20

Single chamber, internal nozzle spray 3.00 1.60 1.00 0.76Self-induced spray b. e. d 0.80 0.40 0.25 0.26Wet impingement b. c 1.00 0.60 0.26 0.26Venturi c. d 3.00 1.60 1.20 0.60Variable pressure drop inertial c. d t. 1.00 0.30Mechanical e. d 1.76 0.75 0.35

Basic designs, mild steel construction.b Add 30 to 40 percent to base price for fan, drive, and motor (standard construction materials).

Special materials construction costs for 1000 to 40,000 cfm range units are approximately as follows:Rubber lining-base increase of 66 to 116 percent.Type 304 stainless steel-base increase of 30 to 60 percent.Type 316 stainless steel-base increase of 45 to 100 percent.

d Add from 10 to 40 percent to base price per additional stage as in some cyclonic and wet impingement designs.

158

sus size and efficiency difficult to determine.Based on the data available, all estimatesmust be constructed over an interval of un-certainty for each of the three variables. Tomake the cost estimation problem manage-able in this report, nominal high, medium,and low collection efficiencies have been se-lected for each type of control equipment,except fabric filters. For fabric filters, thenominal high, medium, and low curves re-flect construction variations. The purchase,installed, and total annualized costs of oper-ation are plotted for each of the three effi-ciency levels over the gas volume range in-dicated. Purchase, installed, and total an-nualized costs for fabric filters are plottedfor variations in filter construction and clean-ing methods.

Generalized categories of control equip-ment are discussed rather than specific de-signs because of uncertainties in size, effi-ciency, and cost. If required, more detailedinformation on the cost, of various engineer-ing innovations (e.g., packed towers of spe-cific design to accommodate a corrosive gasstream) should be requested from the manu-facturers of the specific equipment. Cost vari-ations associated with wet collectors are re-ported in Table 6-2.3

Other 'difficulties exist in developing costinformation for existing control devices, es-pecially cost estimates on the maintenanceand operation of control equipment. Indivictual iirms may remember what a controldevice cost originally, but they may forgetwhat it costs to install and operate. In addi-tion, internal bookkeeping and auditing sys-tems often bury these expenditures in totalplant operating costs. For example, waterand electricity used by a control operationare not always separately metered and ac-countable as a specific air pollution controlcost item. Some of these costs can be identi-fied and assessed on the basis of industrialexperience or engineering estimates.

6.5 DESCRIPTION OF CONTROL COSTELEMENTS

6.5.1 General

The actual cost of installing and operatingair pollution control equipment is a functionof many direct and indirect cost factors. An

analysis of the control costs for a specificsource should include an evaluation of allrelevant factors, as outlined in Figure 6-4.The control system must be designed andoperated as an integral part of the process;this will minimize the cost of control for agiven emission level. The definable controlcosts are those that are directly associatedwith the installation and operation of controlsystems. These expenditure items from thecontrol eqt.ipment user's point of view havea breakdown for accounting purposes as fol-lows:

Capital Investment:Engineering studiesLandControl hardware*Auxiliary equipment*Operating supply inventoryInstallation*StartupStructure modification

Maintenance and Operation:Utilities*Labor*Supplies and materials*Treatment and disposal of collected

materialCapital Charges:

Taxes*Insurance*Interest*

Of the expenditure items shown above,only those denoted by an asterisk were con-sidered in developing the cost estimates usedin this chapter. Othee factors, such as engi-neering studies, land acquisition, operatingsupply inventory, and structural modifica-tion, vary in cost from place to place andtherefore were not included. Costs for thetreatment and disposal of collected material,while also not included, are discussed in somedetail in Section 6-8.

6.5.2 Capital Investment

The "installed cost" quoted by a manu-facturer of air pollution equipment usuallyis based on his engineering study of theactual emission source. This cost includesthree of the eight capital investment items

* Denotes cast items considered in this report.

159

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Table 6-3.TOTAL INSTALLATION COST ['ORVARIOUS TYPES OF CONTROI, DEVICES EX-PRESSED AS A PERCENTAGE OF PURCHASECOSTS

Equipment type

Cost, percent

Low Typical HighEx-

Cremehigh

Gravitational 83 67 100Dry centrifugal 36 60 100 400Wet collector:

Low, mediumenergy.. ... 60 100 200 400

High energy 100 200 400 600Electrostatic

precipitators... 40 70 100 400Fabric filters 60 76 100 400Afterburners 10 26 100 4C0

High-energy wet collectors usually require more ex-pensive fans and motors.

control hardware costs, auxiliary equipmentcosts, and costs for field installation.

The purchase cost curves that are shownin Section 6.7 illustrate the control hardware

costs for various types of control equipment.These purchase costs are the amountscharged by manufacturer for equipment ofstandard construction materials. Basic con-trol hardware includes built-in instrumenta-tion and pumps. Purchase cost usually varieswith the size and collection efficiency of thecontrol device. The purchase costs plotted onthe curves are typical for the efficiencies in-dicated, but these costs Mr: vary -.±20 per-cent from the values shown. 01 course, equip-ment fabricated with special materials (e.g.,stainless steel or ceramic coatings) for ex-tremely high temperatures or corrosive gasstreams may cost much more.

The remaining capital investment items,auxiliary equipment and installation costs,are aggregated together and referred to as"total installation costs." These costs areshown in Table 6-3, expressed as percentagesof the purchase costs. These costs include areasonable increment for the followingitems: (1) erection, (2) insulation material,(3) transportation of equipment, (4) site

Table 6-4.COND1TIONS AFFECTING INSTALLED COST OF CONTROL DEVICES

Cost category Low cost

Equipment transportation.. Minimum distance; simpleloading and unloadingprocedures.

Plant age Hardware designed as anintegral part of new plant.

Available space Vacant area for loci.Iion ofcontrol system.

Corrosiveness of gas Noncorrosive gas

Complexity of startup S mile startup, no extensiveadjustment required.

Instrumentation Little required

Guarantee on performance.. None neededDegree of assembly Control hardware shipped

completely assembled.Degree of engineering design. Autonctnous -package con-

trol system.

Utilities Electricity, water, waste dis-posal facilities readilyavailable.

Collected waste material No special treatment facili-handling. ties or handling required.

Labor Low wages in geographicalarea

High cost

Long distance; complex procedcee 'or loading and un-loading.

Hardware installed into confines of old plant requiringstructural or process modification or alteration.

Little vacant space requires extensive rteel supportconstruction and site preparation.

Acidic emissions requiring high alloy accessory equip-ment using special handling and construction tech-niques.

Requires extensive adjustments; testing; considerabledown time.

Complex instrumentation required to assure reliabilityof control or constant monitoring of gas stream.

Required to assure designed control cfrciency.Control hardware to be assembled and erected in the

field.Control system requiring extensive integration into

proce. insulation to correct temperature problem,noise abatement.

Electrical and waste treatment facilities must be ex-panded, water supply must be developed or ex-panded.

Special treatment facilities and/c4 handling requirel.

Overtime and/or high wages In geographical arms.

161

preparation. (5) clarifiers and liquid treat-ment systems (for wet collectors). and ((i)auxiliary equipment such as fans. ductwork.motors. and control instrumentation. Thelow values listed in the table are for minimaltransportation and simple layout and instal-lation of control devices. High values are forhigher transportation cost and for difficultlayout and installation problems. The ex-treme high values are for unusually complexinstallations on existing process equipment.Table 6 .1 lists the major cost categories andrelated conditions that establish the instal-lation cost range from low to high. The "in-stalled cost" estimates reported in Section6-7 are the sum of the purchase costs andthe total installation costs.

6.5.3 Maintenance and Operation

The following sections describe the work-ing equations for the operation and mainte.trance costs of various control devices. Numerical values for the variables expressed inthese equations are found in Tables 6 5 and6 6.

Table 6 3.-ANNFAI, NlAINTENANCE COSTS rollALL GF.NERIC T1 PES OF CONTROL DEVICES

Generic typeDollars per acfm

Low Typical High

Gravitational and drycentrifugal collectors..... 0.005 0.015 0.025

Wet collectors _.. 0.02 0.04 0.06Elect rettat ic precipitators:

High voltage.. . 0.01 0.02 0.03Low .... q.00S 0.014 0.02

Fabric filters 0.02 0.05 0.05Afterbur nets:

Direct name 0.03 0.06 " 0.10 "Catalytic.... 0.07 0.20 0.35

Metal liner with outside insulation." Refractory lined.

Grnmr/---The costs of operation andmaintenance will vary widely because of dif-ferent po!icies of control equipment users.This variance will depend on such factorsas the quality and suitability of the controlequipment. the user's understanding of itsoperation. and his vigilance in maintainingit. Maintenance and operation usually arevery difficult to define and assess, but often

162

Table 6- 6.-MISCELLANEOUS COST AND EM7I.NEERING FACTORS

(Fan efficiency-60 pereert: Pump efficiency-50percent)

rower rogt, rhillorA/loclor

Low Typical High

All lcV ices 0.005 0.0 1 1 0.020

11,,ofrA nl ovirtifiwr. 8760 hortro pct. war, 24 bridnyX365 daii+,, yr . 8760

Low Medium High

I'oNer requirements %a effi-ciency for high voltageelectrostatic precipitators, 10 'kw/aefrn 0.19 0.26 0.40

Low High

Power requirements vs efficiencyfor lowvoltage electrostaticprecipitators 110 'kw/acfm/ 0.015 0.040

Low Typical High

Liquor cost in 10 ' dollars pergallon per hour (for%vet systr nil -Wet scrubber(make -up liquor require-ments, 0.0005 galjh r.ac f m 0.35 0.50 1.00

rower rrviremtnix

Low Medium Highefficiency efficiency efficiency

-Scrubbing" (contact)power, horsepower/acfm 0.0013 0.0035 0.015

Strolfibrr liquor delfo

Low Typical High

Liquor circulation rate.gal/acfm

Minimum head require-ments. feet water .

0.001 0.008 0.020

30 60

Preigoirr drop I1 roe r(poipmcnt, leaches of wafer

Generic type Low Typical High

Dry centrifugal collector 2-3Fabric filter 2-3 4-5 6-8Afterburners 0.5 1.0 2

Electrostatic precipitators andgravitational collectors 0.1 0.5 1

*Rased on national average of large cons.uMers.'1 psig0.2.1 ft water.

may be a significant portion of the overallcost of controlling air pollutant emissions.Although the combined operating and main-tenance costs may be as low as 10 percent ofthe annualized total cost for a gravitationalsettling chamber, for example, they may b?as high as 90 percent of the total annualize('cost for a high-efficiency wet col:ector.

Maintenance cost is the expenditure re-quired to sustain the operation of a controldevice at its designed efficiency with a sched-uled maintenance program and necessary re-placement of any defective parts. On an an-nual basis, maintenance cost in the follow-ing equations is assumed proportional tothe capacity of the device in acfm. Table6-5 shows annual maintenance cost factorsfor all types of particulate control devices.Simple, low- efficiency control devices havelow maintenance costs; complex, high-efli-clency devices have high maintenance costs.

Annual operating costs is the expense ofoperating a control device at its designedcollection efficiency. This cost depends on thefollowing factors: (1) the gas volumecleaned, (2) the pressure drop across thesystem, (3) the operating time, (4) the con-sumption and cost of electricity, (5) the me-chanical efficiency of the fan, and (6) thescrubbing liquor consumption and costs(where applicable).

rrritationai and Centrifugal Me-chanical Collectors-1n general, the only sig-nificant cost for operating mechanical col-lectors is the electric power cost, which va-ries with the unit size and the press. ure drop.Since pressure drop in gravitational collee-tots is low, operational costs associated withthese units are considered to be insignificant.Maintenance cost includes the costs of serv-icing the fan motor, replacing any liningworn by abrasion, and, for multiclone col-lectors, flushing the clogged small diametertubes.

Cost equationThe theoretical annual cost(G) of operation and maintenance for cen-trifugal collectors can be expressed as fol-lows:

G,s0.7457 PI1K mi6356E

where:S design capacity of the collector, acfmP pressure drop inches of water (see

Table 6-6)1.: fan efficiency, assumed to be 60 per-

cent (expressed as 0.6)0.7457 = a constant (1 horsepower -=0.7457

kilowatt)11= annual operating time (assumed 8760

hours)K poorer et-At, dollars per kilowatt -hour

(see Table 6-6)maintenance cost, dollars per acfm

(see Table 6-5)For computational purposes the cost formulacan be simplified as follows:

G-S[195.5x 10 PI1K +M) (2)

6.5...) CotiretorsThe operating costsfor a wet collector power and scrubbing liq-uor costs. Power costs vary with equipmentsize, liquor circulation rate, and pressuredrop. Liquor consumption varies with equip-ment size and stack gas temperature. Main-tenance includes servicing the fan or com-pressor motor, servicing the pump, replacingworn linings, cleaning piping, and any nec-essary chemical treatment of the liquor inthe circulation system.

Cost «motionthe theoretical annual cost(G) of operation and maintenance for wetcollectors can be expressed as follows:

G S[0.7157 11K P + +6356E 1722F 3960F

+ M l (3)

where:S,-design capacity of the wet collector,

acfm0.7457,a constant (1 horsepower =0.7457

kilowatts)11= annual operating time (assumed 8760

hours)K = power costs, dollars per kilowatt-hour11, pressure drop across fan, inches of

water (see Table 6-6)Q = liquor circulation, gallons per acfm

(see Table 6-6)g, liquor pressure at the collector, psig

(see Tab'e 6 -6)

163

h = physical height liquor is pumped incirculation system, feet (see Table 6 .6),-- make-up liquor consumption, gallonsper acfm (see Table 6-6)liquor cost, dollars per gallon (see

Table 6 6)M = maintenance cost, dollars per acfm

see Table 6-5)fan efficiency, assumed to be 60 per-

cent (expressed as 0.60)F pump efficiency, assumed to be 50 per-

cent (expressed as 0.50)

The above equation can be simplified ac-cording to Semrau's total "contacting power"concept.4Semrau shows that efficiency is pro-portional to the total energy input to meetfan and nozzle power requirements. Thescrubbing (contact) power factors in Table6-6 were calculated from typical perform-ance data listed in manufacturers' brochures.These factors are in general agreement withdata reported by Semrau. Using Semrau'sconcept the equation for operating cost canbe simplified as follows:

G ...---S[0.7157 11K ( 980) Willa+ M]

where Z contact power (i.e., total power in-put required for collection efficiency),horsepower per acfm (see Table 6-6). Itis a combination of:

1. fan horsepower per acfm

6356 E and

2. pump horsepower per act m

Qg Vie power to atomize)1722 l+

'cater through a noz-:le

The pump horsepower. Qh 1980, requiredto provide pressure head is not included inthe contact power requirements.C.5.3.4 Mrefrostatir Precipitators Theonly operating cost considered in the oper-ation of electrostatic precipitators is thepower cost for ionizing the gas and oper-ating the fan. As the pressure drop acrossthe equipment is usually less than ti inchof water, the cost of operating the fan is as-sumed to be negligible. The power cost varies

164

with the efficiency r.nd the size of the equip-ment.

Maintenance usually requires the servicesof an engineer or highly-trained operator, inaddition to regular maintenance personnel.Maintenance includes servicing fans and re-placing damaged w iv es and rectifiers.

Cost (4/notionThe theoretical annualcost (G) for operation and maintenance ofelectrostatic precipitators is as follows:

G -S (.111K + M) (4)where

S design capacity of the electrostatic pre-cipitator. acfm

.1 power requirements, kilowatts peracfm (see Table 6.6)

II= annual o; :rating time (assumed 8760hours)

K power cost. dollars per kilowatt-hour(see Table 6-6)

11 maintenance cost, dollars per Reim(see Table 6-5)

Ffilwir PilfersOperating costs forfabric filters include lower costs for operat-ing the fan and the bag cleaning device.These costs vary directly with size of equip-ment and the pressure drop. Maintenancecosts include costs for servicing the fan andshaking mechanism, emptying the hoppers,and replacing the worn bags.

Cost rviationThe theoretical annual cost(G) for operation and maintenance of fabricfilters is as follows:

0.707 tit,ot(;=" S r (5)

6356Ewhere:

S= design capacity of the fabric filter,acfm

P pressure drop. inc.es of water (seeTable 6 -6)

E -- fan efficiency. which is assumed to be60 percent (expressed as 0.60)

0.7457 =a constant (1 horsepower 0.7157kilowatt)

H ,annual operating time (assumed 8760hours)

K power cost, dollars per kilowatt-hour(see Table 6-6)

M =maintenance cost, dollars per acfm(see Table 6 -5)

Table 6-7. 1101111Y MA. COSTS

DeviceTemperature. `F

Temperature.Inlet Outlet

Fuel cost.'dollars/acfmhr

Direct flame (DF) . 380 1400 1020 ;0.00057OF with heat exchanger 1000 1400 400 0.0002:3ektalytic afterburner (CAB) 380 900 620 0.00018CAB with heat exchanger 650 900 250 0.00014

These figures include the cost of heating an additional 60 percent excess air. It is assumed there i3 noheat content in the material or pollutant being consumed.

For computational purposes, the cost for-mula can be simplified as follows:

G=S[195.5x10-" PIIK +I'd] (6)6..5.3.0 eificrenancrsThe major operatingcost item for afterburners is fuel. Fuel re-quirements are a direct function of the gasvolume, the enthalpy of the gas, and thedifference between inlet and outlet gas tem-peratures. For most applications, the inletgas temperature at the source ranges from300° to 400° F. Outlet temperatures mayvary from 1200° to 1500° F for direct flameafterburners and from 730° to 1200° F forcatalytic afterburners.2 The use of heat ex-changers may bring about a 50 percent re-diction in the temperature difference.'.`Table 6-7 lists hourly fuel costs based on anatural gas cost of $0.60 per million Btu.No credit was given for heat of combustionof particulate or other matter. These costswere developed from enthalpies (heat con-tent) of the process gas at given temper-atures' Maintenance includes servicing thefan, repairing the refractory lining, washingand rinsing the catalyst, and rejuvenatingthe catalyst.

The equation for calculating the operationand maintenance costs (G) is as follows:

0.7457 PIIKC=S[6356 +I1F+111] (7)E

where:S= design capacity of the afterburner,

acfmP=pressure drop, inches of water (see

''able 6-6)E----fan efficiency. assumed to be 60 per-

cent (expressed as 0.60)0.7457=a constant (1 horsepower = 0.7457

kilowatt)

I1 `annual operating time (assumed 8760hours)

K = power cost, dollars per kilowatt-hour(see Table 6-6)

F =fuel cost, dollars per acfm per hour(see Table 6-7)

M =maintenance cost, dollars per acfm(see Table 6-5)

For computational purposes, the cost for-mula is simplified as follows:

G,S[195.5x 10 4 PIIK + IIF+ 11] (8)

Caplial ChargesCapital charge includes overhead expenses

such as taxes, insurance, and interest in-curred in the operation of a control device.Such costs frequently lose specific identitybecause of internal I.:counting practices. Itis possible, however, by reasonable assump-tions, to include capital charges in the an-nualized cost of control.

6,5.3 Annualiration of CoatAnnualized capital costs are estimated by

depreciating the capital investment (totalinstalled cost) over the expected life of thecontrol equipment and adding the capitalcharges (taxes, interest, and insurance).Adding the recurring maintenance and op-eration costs to this figure gives a total an-nualized cost of control. Total annualizedcost estimates are shown in Section 6.'7.

6.5.6 Assumptions in Annualized ControlCost Elements

Annualized conttol costs will differ frominstallation to installation and from regionto region, and certain simplifying assump-tions have been necessary to develop the costfigures of this section. if more information

165

for a given location is available, it is de-sirable to substitute this for the assumptionsused here.

6.5.6.1 Annualizrd Capital Cost Assump-tionsThe simplifying assumptions for com-puting the total annualized capital cost areas follows:

1. Purchase and installation costs aredepreciated over 15 years, a periodassumed to be a feasible economiclife for control devices.

2. The straight line method of deprecia-tion (OA percent per year) is usedbecause it is the most common meth-od used in accounting practices. Thismethod has the simplicity of a con-stant annual writeoff.

3. Other costs called capital chargeswhich include interest, taxes, insur-ance, and other miscellaneous costsare assumed to be equal to the amountof depredation. or percent of theinitial capit:d cost of the controlequipment installed. Therefore, de-predation plus these other annualcharges amount to 131,11 percent ofthe initial capital cost of the equip-ment.

Opurtinu Cost AssumptionsThefollowing assumptions were taken into account for computing operation and mainte-nance costs.

1. Power costs included in annual (Ter-atg expense reflect electricity usedby all systems directly associatedwith the control equipment. Electri-cal power requirements are computedon a constant usage basis at a sped-fied gas volume.

2. For wet collectors. it is assumed thatthe liquor is recirculated in a closedsystem. Liquor consumption consistsof the makeup liquor which must beadded from time to time. Stack gastemperature influences the rate of liq-uor loss; this influence is partially ac-counted for by assuming a constantloss per cubic foot of stack gas vol-ume. This assumption is necessarybecause of the extremely wile rangeof stack gas temperatures.

166

3. The costs for electricity and waterare computed on the marginal rateclasses for each size user. which as-sumes that any additional consump-tion will be priced at the lowest rate-highest volume class available. Ex-cept where specifically indicated, thetypical values for the pressure dropand cost of electricity (see Table 6-7)were assumed in all control cost cal-culations and illustrations.

1. The disposal cost and or recoveredvalue of collected effluents are notincluded in the operating cost calculations because of cost differencesfrom process to process. Disposal costfigures for several major industrialcategories are reported in Section6.8.

6.5.6..1 Maintenance Cost AssuptionsItis assumed that a user of control equipmentestablishes a preventive (scheduled) main-tenance program and carries it out to main-thin equipment at its designed collection effi-ciency. Further, it is assumed that unsched-uled maintenance, such as replacement of de-fective parts, is undertaken as requir'd. Thecost incurred far equipment modification orretail due to an operational accident is notincluded.

6.6 1IET1101) FOR LSTIMAIIING ANNUALCOST Or CONTROL FOR A SPE.ClFIC SOURCE

6.6.1 General

As previously indicated. it is beyond thescope of this report to identify and assessthe cost of control for a specific source. Suchassessments can. however, be calculated byapplying the steps outlined below.

6.6.2 Procedure

The following procedure can be used todetermine the expecte(' cost of control forany source.

Step 1. Describe the source (includingcharacteristics of the process). the charac-teristics and consumption of fuel for com-bustion. and the total number of hours inoperation annually. Emissions can be deter-nvir.ed by making stack gas tests or can be

.?stimated by making calculations using theemission factors.

Step 2. Select the applicable types of con-trol equipment. Figure 6- I illustrates whatmust be considered in selecting the optimumiyi)e of control equipment.

Step 3. Specify pressure drops. efficiencies.construction material, energy and fuel re-quirements. and size Ihnitations for the se-lected control equipment. taking into accountany existing equipment.

Step .1. Determine the gas How in acfmat the point of collector location. For wetcollectors, this would be the water saturatedgas volume. This should be done by takingmeasurements at maximum operating con-ditions.

Step 5. Determine the estim tied total pur-chase cost for the specific selected device(curves found in Section 6.7) at the requiredgas volume and control efficiency, For fab-ric filters, select the proper filter medium forthe process.

Step fi. Multiply the cost found in step5 by the low, typical. and high installationcost factors (Table 6 -3), and add the resultto the estimated total purchase cost to ob-tain the corresponding low, typical, and hightotal installed costs. Conditions affecting thecost of installation are listed in Table 6-1.

Step 7. Calculate the total annual capitalcost as follows:

annualized capital costeepreciation 4- capital charges

total investment costaStep 8. Compute the cost of electricity.

maintenance, and liquor consumption.Step 9. Compute low, medium, and high

operating and maintenance costs from theappropriate formulas:

Dry centrifugal collectorsG =S[195.5 .).; 10-0 PIIK + M]Wet scrubbers

G,S[0.71571980

+ WM+ MElectrostatic precipitator(3,SPi1k + MI

litts,.41 oft the assumptions in Section 6.5.6.1.

Fabric filtersG z: S[195.5 10 4 M)

Afterburnersz S[195.5 \ 41)111: +

where:tlworetical value for operating and

maintenance costsS the design capacity of the collection

device, acfmP pressure drop of the gas. inches of

II annual operating timepower costs, dollars per kilowatt-hou

Q liquor circulation, gallons per acfmh z physical height that liquor is pumped

in circulation system, feetZ total power input required for scrub-

bing efficiency, horsepower per acfmM maintenance cost, dollars per acfmW liquor consumption, gallons per hour

per acfmcost of liquor. dollars per gallon

z power requirement. kilowatts per acfm')ased on efficiency

F fuel cost, dollars per hour per acfm

Step 10. Add the typical annualized capi-tal cost to the typical operating and mainte-nance cost to yicId the estimated total an-nualized cost of control.

Step It. Because the above calculation isa point estimate, the range of costs shouldbe investigated. For this, a variance is cal-culated and applied to the total estimatedannual cost. The low cost variance (VI) andhigh cost mimic.? (V%) of an equipmentcombinat on can be computed by using thesquare root of the sum of the squares. Thet'ormulas for these variances are as follows:

(C.C1):+-----

where:

C,. and CI, are the low, typical. and highannual capital cost estimates. respectively,and G1. and (1,. and G), are the low, typical,and high operation and maintenance cost es-timates. These formulas are taken from theusual definition of the -_,tandard error of alinear combination of statistically independ-

167

rr

ent variables. They permit computation ofthe most probable, rather than the extreme,range of costs.

Step 12. The high cost variance (V.) isadded to the total estimated annual cost toyield the high cost limit.

Step 13. The low cost variance (V1) issubtracted from this total estimated annualcost to yield the low cost limit.

6.6.3 Sample Calculation.The following calculations illustrate the

method used to determine the total estimatedannual cost of control. The following exam-ple shows the estimation of annualized costfor a 60,000 dm, 90 percent (medium effi-ciency) wet collector.

Step 1. Annual operating time= 8760hours (11)

Step 2. Wet collector (given)

Step 3. 90 percent efficiency (given)Scrubbing power required-0.0035

hot.,epower per acfm (Z)

Step 4. Actual gas flow -60,000 acfm(given)

Step 5. Purchase cost = $17,000 (from Sec-tion 6.7.4 for wet collectors)

Step 6. Installation factors from Table 6-3are 50 percent, 100 percent and 200 per-cent

Installation factor 60% 100% 200%Installation cost $8,500 $17,000 $34,000Purchase cost $17,000 $17,000 $17,000

Total capital costIII*101.11111m.

$28,800IN...101100111

$34,000/11111$51,000

Step 7. 0.133x (Total capital cost] an-nual capital cost (C)

CI. 0.133 x $28,400 = $3400C.,---- 0.133 x $34,000 = $4630C.6.0.133 x$51,000,--$6800

Step 8. Power cost, dollars/kw-hr (K)Low Typical High0.005 0.011 0.020

Maintenance cost, dollars/acfm, (M)Low Typical High0.02 0.04 0.08

168

Liquor cost, 10-' dollars/gal, (L)Low Typical High0.35 0.50 1.00

Head required for circulation in sys-tem, feet, (h)

Low Typical High1 30 60

Liquor circulation, callons per acfm,(Q)

Low Typical High0.001 0.008 0.020

Makeup liquor rate, 10 gal/hr-acfm,(W) =0.5

Step 9. Using the following formula to de-termine annual operating cost (C),

G.SRZ+-9h ) (0.7457 HK)1980

+WilL+M]

the low, typical and high operating and main-tenance costs are as follows:

CI =$8200 $18,100 0, = $35,900

Step 10. From the steps 7 and 9,

Cm =$4630 Gm= $18,100

Then, the total estimated annual cost isas follows:

C. + G. 822.600

Step 11. Using the square root of the sumof the squares of the differences, the hig'i andlow cost variances are as follows:

V1 .V(Cm (G.-01)3V(4530-3100)3+ (18,100- 8200)'

VI =810,000

Ni(C. C.)3+ (08-0.P.v(6800=4630) I + (35,900 18,100) I

V.--= $17,900

Step 12. From Step 10, the total estimatedannual cost $22,600

From Step 11, VI ---- $10,000Low cost limit $10,000,2$12,600

Ir.

Step 13. Total estimated annual cost=$22,600

From Step 11, V,,.$17,900High cost limit = $22,600 + $17,900$10,500

Step 14. The amount of particulate matteremitted may be calculated if the inletconditions are known.

6.6.4 Annualized Cost Variation

The previous section illustrated the prob-able high and low cost limits for a single in-stallation, taking into account the variationin cost for installation, maintenance, and op-eration. To compute the annualized cost fora given emiszion reduction system, one musttake into account four variables: (1) collec-tion efficiency of the system, (2) cost of in-stalling the system, (3) cost of operation, and(4) maintenance cost. A more complete sum-mary of the range ..sf total annualized costs isshown in Table 6-8 for a 60,000 acfm wet col-lector. This table illustrates cost figures for81 possible combinations of each of the fourvariables, with each variable taking on threeindependent values-low, typical, and high.It is constructed by the procedure outlined inSteps 1 through 10 in the previous section.The constants for computing these values are

taken from Tables 6-5 and 6-6. Table 6-8shows that a low-efficiency 60,000 acfm wetcollector with low installation, maintenance,and operation costs will cost approximately$6100 per year to operate (extreme upperleft hand corner). The most efficient (99 per-cent efficiency) wet collector, according to thetable, will cost as high as $137,400 per yearto operate. The most likely costs for efficien-cies of 75 percent, 90 percent, and 99 percentare $11,300; $22,700; and $74,600, respec-tively. The type of data shown in Table 6-8 isuseful in developing cost-effectiveness rela-tionships. Note that this table does not showthe variances, V, and V,; these should be usedonly when the probable cost limits are de-sired.

6.7 COST CURVE:1 BY EQUIPMENTTYPE

6.7.1 GeneralFor the convenience of those vho may use

the cost information ,lescribed in this chap-ter, the following sections contain a seriesof control cost curves (see Figures 6-5through 6-24). For each type of controlequipment, a series of curves is presented:(1) purchase cost curves, (2) installed costcurves, and (3) annualized cost curves.

The estimated purchase cost curves show

Table SAL-ILLUSTRATIVE PRESENTATION OF ANNUAL COSTS OF CONTROL FOR 60,000 acfm WITSCRCRRER (dollars)

El 76 percent I. E. =90 percent F,99 percent11. 1. 1, 1, 1, 1. 1,

MI 6,100 6,800 8,100 11,800 13,000 16,200 35,1100 37,800 42,800ht. 7,300 8,000 9,800 18,000 14,200 16,400 36,700 89,000 43,60024, 8,600 9,200 10,600 14,200 16,100 17,600 37,90) 40,200 44,700MI1 3,500 10,100 11,600 20,800 21,600 23,700 71,100 78,300 77,900

0, M. 10,700 11,300 12,700 21,600 22,700 24,900 72,800 74,600 79,100M1, 11,900 12,500 13,900 22,700 23,900 26,100 73,600 76,700 80,300MI 18,300 20,800 36,900 88,100 40,300 128.200 130,600 136,000

01 14,,, 19,600 20,100 21,600 36,100 39.300 41,600 124,400 131,700 136,200M, 70,700 21,800 11,720 39,300 40,600 42,700 180,000 182,900 18:,400

E efficiency factor.Subscripts 1, m, and h indicate low, medium, and hlitt ranges, respectively.1. installation factor.

a NI .trraint*hance factor.0 operating factor.

Nor' A similar table can be generated to stow the various control costa for any type of control equipment byopecifyie operating conditions and calculating each entry. This procedure provides complete information to aid t-lb. Reetkenettt of existing controls ot other control ietettatives.

169

the dollar amounts charged by manufactur-ers for basic control equipment, exclusive oftransportation charges to the installationsite. This basic control equipment includesbuilt-in auxiliary parts of the control uni,,such as instrumentation and solution pumps.The installed cost curves include the pur-chase costs, additional auxiliary equipmentcosts, and installation costs, as described inSection 6.5.2. The annualized cost curves in-clude elements discussed in Section 6.5.3through 6.5.6. The assumptions, sources ofdata, and the limitatiors used to developthis information are discussed in Sections6.3 and 6.4.

6.7.2 Gravitational Collectors

In computing the cost of gravity collectors,three collection efficiencies were considered.These efficiencies were based on the assump-tion of essentially complete removal of 87-micron, 50-micron, and 25-micron particles,and are designated as low, medium, and high

Celts s.p v f 20 wont.0.1 111111 1, i 1 1 1 11

1 S 10 30 100

GAS VOLUME tHROUGH COLLECtOR, 103 oefat

Frotits 64. f'atchsoe tost of grarhational collectors.

170

efficiencies, respectively. The low and me-dium efficiency collectors are simple expan-sion chambers, and the high efficiency col-lector is a multiple-tray settling chamber,commonly called a Howard separator.

In actual operation, the collection efficiencyfor a gravitational collector depends on theparticle size distribution. In cleaning the fluegas from a stoker-fired coal furnace, for ex-ample, low-, medium-, and high-efficiency col-lectors would have particle removal efficien-cies of approximately 64 percent, 75 per-cent, and 88 percent, respectively. In clean-ing the flue gas from a pulverized coal fur-nace, these same collectors, because of thesmaller-sized particles emitted by the com-bustion unit, would have approximate effi-ciencies of 21 percent, 34 percent, and 56percent, respectively.

The purchase costs of gravitational col-lectors are shown for three different effi-ciencies in Figure 6-5. These are apprlxi-mate costs for typical installations. If it werenecessary to include insulation or a corro-sion-resistant lining, the costs would behigher. The total installed cost was alsocalculated for each efficiency and is shownin Figure 6-6. The total installed cost is thesum of the purchase and installation costs.The installation costs were assumed to rangefrom 33 percent to 100 percent of the pur-chase cost (see Table 6-3), and this rangeresults in a cost band for each efficiency. asshown in the figure. No annualized costcurves are presented for these collectors be-cause operation and maintenance costs, otherthan for removal and disposal of collectedmaterial, usually are negligible, except wherecorrosion ma :' be a problem. Section 6.8 pro-vides specific information on the disposalof collected material.

6.7.3 Dry Centrifugal Collectors

The costs of purchasing, installing, andoperating mechanical centrifugal collectorsare given in Figures 6 -?, 6-8, and 6-9 re-spectively. The curves in these figures showcosts for collectors that operate at nominalefficiencies of 50 percent, 70 percent, and95 percent (see Section 6.4). Costs are plot-ted for equipment sizes ranging from 10,000to 1,000,000 'term. The as_surnutions used in

100

50

10

5

1.0

Lao

0.5

1 1 I I 11111 I 1 1 1 111'-, 100

0.11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 S 10 SO 100 11

GAS VOLUME THROUGH COLLECTOR, 103 ach,

Fict Rs; 6-6. Installed cost of graitatiGp.%1 collectors.0-

0U 10

SO

10 100

SO

10

ltilSOO 800

1 1 1 1 1111 1 1 1 1 1111

SO 100 5C3 1000

GAS VOLUME THROUGH COLLECTOR, 103aeIm

FIGURE 6-S. Installed cost of dry centiifugal col.lectors.

100

SO

0

o 10

V

Z 3V3

1

10 SO 100 sois 1000

GAS VOLUME THROUGH COLLECTOR, 103 Sem

not-RE f Purchase cost of dry centrifugal col-lectors.

100

0

4

S

HIGH EFFICIENCYMED1UM EFFICIENCY

LOW EFFICIENCY--

100

so

1 I 1 IA300 SOO

1

1 1 1 11111 1 1 1 1 till10 S0 100 5G3 1000

GAS VOLUME THROUGH COLLECTOR, 103 sem

FiGt-StE 6-9. Annualiwd cost of operation of drycentrifugal collectors.

calculating annual operation and mainte-nance costs for dry centrifugal collectors areas follows:

1. Annual operating time.87130 hours2. Collector pressure drop=3 inches of

water3. Power cost = $0.011 /kw-hr4. Maintenance cost =10.016 facfm

171

6.7.4 Wet Collectors

The costs of purchasing, installing, andoperating wet collectors are given in Fig-ures 6-10, 6-11, and 6-12, respectively, as afunction of equipment size. The curves inthese figures show costs for collectors thatoperate at normal efficiencies of 75 percent,90 percent, and 99 percent (see Section6.4). The basic hardware costs for mediumand high collection efficiency equipment arereported by manufacturers to lie in the same1000

500

100

50

10

5

=111111 1 171 Ilfli T 1 1-111(±

Costs moy very by 20 percent.

I 1 1 1 11111 1 1 1 1 11111 1 1 1 1 1 111

5 10 50 100 500 1000

GAS VOLUME THROUCH COLLECTOR, 103 acfm

FIGURE 6-10. Purchase cost of wet collectors.

1000

500

100

50

10

5

= I I I 111111 1 I 1 111111 1TTITE

HIGH

LOW

EFFICIENCY1 1 1 111111 fill11111 1 1 111111

5 10 50 100 500 1000

GAS VOLUME' THROUGH COLLECTOR, 103acfm

FIGURE 6-11. Installed cost of wet collectors.

172

MEDIUM

EFFICIENCY

=

cost range and both appear on the samecurve in Figure 6-10. The higher installedcost of a high collection efficiency system inFigure 6-11 results from the need for larger,more expensive auxiliary equipment (basedon Table 6-3). The assumptions used in cal-culating annual operating and maintenancecosts for wet collectors are as follows:

1. Annual operating time=8760 hours2. Contact power requirements:

0.0013 horsepower/acfm for 75percent efficiency



3. Power cost= $0.011/kw-hr4. Maintenance cost= $0.04/acfm5. Head required for liquor circulation

in collection system= 30 feet6. Liquor circulation =0.008 gallon/

acfm7. Liquor consumption =0.0005 gallon/

hour -acfm8. Liquor cost =$0.0005/gallon

6,7.5 High-Voltage ElectrostaticPrecipitators

The costs of purchasing, installing, andoperating high-voltage electrostatic precipi-

1 000

500

0

° too

0 5°U0N:J

10

3

1111111ETTIT1111 1 1 1 1111

I 1 1 1 1 1 1 1 1 1 1 I 11111

5 10 50 100

I 1 1 111111

500 1000

GAS VOLUME THROUGH COLLECTOR, 103 acfmFIGURE 6-12. Annualized cost of operation of wet

collectors.

tatora are given in Figures 6-13, 6-14, and6-16, respectively. The curves in these fig-ures show costs for collectors that operateat nominal efficiencies of 90 percent, 95 per-cent, and 99.5 percent. These costs are plot-ted for equipment sizes ranging from 20,000to 1,000,000 acfm. The assumptions used incalculating annual operation and -mainte-nance costs for high-voltage electrostatic pre-cipitators are as follows:

1. Annual operating time 8760 hours2. Electrical power requt..3ments:

aged modular low-voltage precipitators withflow rates of less than 1500 acfm are usedto collect oil mist from machining operations.Purchase cost of such a unit usually is lessthan $1200. The assumptions used in cal-culating annual operation and maintenancecosts for low-voltage electvostatic precipita-tors are as follows:

r.

0.00019 kw/acfm for low effici-ency 0

0.00026 kw/acfm for medium 7,efficiency

0.00034 kw/acfm for high effi- 3ciimcy

3. Power cost $0.011/kw-hr4. Maintenance cost -,---$0.02/acfm

6.7.6 Low-Voltage ElectrostaticPrecipitators

The curves in Figures 6-16, 6-17, and 6-18indicate purchase cost, installed cost, and op-eration cost of low-voltage electrostatic pre-cipitators for low and high collection effi-ciencies based on design gas velocities of 160and 125 feet per minute, respectively. Pack-

1000

500

100

50

Costs may vary by ± 20 percent.

10 1 I 1 1 11111 I 1 1 1_11

10 50 100 500 1000

GAS VOLUME THROUGH COLLECTOR, 103 acfm

FIGURE 6-13. Purchase cost of high-voltage electro-static precipitators.

1000

500

100

SO

1

1000

500

300 SOO

10 I Ili 1 I I 1 11 111110 50 100 500 1000

GAS VOLUME THROUGH COLLECTOR, 103 acim

FIGURE 6-14. Installed cost of high-voltage electro-static precipitators.

oo

in 50

0-0

(-)0

0o 10aw

5

zz

I1

10 50 100 500 1000


FIGURE 6-15. Annualized cost of operation of high-voltage electrostatic precipitators.

173

100

50

0

0

10

1. Annual operating time= 8760 hours2. Electrical power requirements:

0.000015 kw/acfm for low effi-ciency

0.000040 kw/acfm for high effi-ciency

3. ewer cost = $0.011/kw-hr4. Maintenance cost = $0.02/acfm

50

L.

80

Costs may vary by ± 20 percent.

5 10 50 100

GAS VOLUME THROUGH COLLECTOR, 103 ocfm

FIGURE 646. Purchase cost of low-voltage electro-static precipitators.

1000

.1 500

-0NO

100

50

105 10 50 100


FIGURE 6-17. Installed cost of low-voltage electro-static precipitators.

.a

174

6.7.7 Fabric FiltersFigures 6-19, 6-20, and 6-21 show pur

chase cost, installed cost, and annualized costof control for three different tyres of filters.Each of the three filters is designed with

!00I

500

0-0

O

N

UO

5

zz

I I 1 1 I I I 1 I 1 1 1 1 1 1 1

5 10 50 100


FIGURE: 6-18. Annualized trust of operation of low -s oltage electrostatic precipitators.

100

LA 500

00,)0I

V 10 100iy

0

50

100 500

Costs moy vary by ± 20 percent.

VIII I I I

10 50 100 500 1000

GAS VOLUME THROVGH COLLECTOR, 103 ocfm

A - HIGHTEMPERATURE SYNTHETICS, WOVEN ANDFELT. CONTINUOUS AUTOMATIC C1 tANING.

B MEDIUM-TEMPERATURE SYNTHETICS, WOVEN ANDFELT. CONTINUOUS AUTOMATIC CLEANING.

C - WOVEN NATURAL FIBERS. INTERMITTENTLYCLEANED SINGLE COMPARTMENT.

FIGURE 6-19. Purchase cost of fabric filters.

about the same efficiency-99.9 percent.Costs are plotted for equipment sizes rang-ing from 10,000 to 1,000,000 acfm.

The control cost curves represent the fol-lowing different types of filter installations:

1. Curve A represents a fabric filter in-stallation with high-temperature syn-thetic woven fibers (including fiber-glass) and felted fibers cleaned con-tinuously and automatically.

2. Curve B represents an installationusing medium-temperature syntheticwoven and felted fibers, such as Or-lon or Dacron, cleaned continuouslyand automatically.

3. Curve C is the least expensive instal.lation. Woven natural fibers are usedin a single compartment. Filters areintermittently cleaned. This equip-ment is rarely designed for processeshandling over 150,000 acfm.

These control cost curves do not includedata for furnace hoods, ventilation ductworkand pre-coolers that may appear only in cer-

100

50

I0

5

--10 50 100


500 1000

A - HIGH - TEMPERATURE SYNTHETICS, WOVEN ANDFELT. CONTINUOUS AUTOMATIC CLEANING.

-MEDIUM-TEMPERATURE SYNTHETICS, WOVEN ANDFELT. CONTINUOUS AUTOMATIC CLEANING.

C - WOVEN NATURAL FIBERS. INTERMITTENTLYCLEANEDSINGLE COMPARTMENT.

F/OURE 6-20. Installed cost of fabric filters.

thin installations. The e numptions for cal-culating operating and maintenance costs areas follows:

1. Annual operating time= 8760 hours2. Pressure drop of the gas through the

three types of fabric filters =4 inchesof water

3. Power cost = $0.05/acfm4. Maintenance cost = 05/acfm

6.7.8 AfterburnersAfterburners are separated into four cate-

gories: (1) direct flame, (2) catalytic, (3)direct flame with heat recovery, and (4)catalytic with heat recovery. Equipment andinstallation costs were obtained from boththe literature and manufacturers of after-burners. Sufficient.data were received on cata-lytic afterburners to define the narrow pur-chase cost range shown in Figure 6-22. Thefigure shows that, purchase costs of directflame afterburners have a wider range thanthose of catalytic afterburners.

Figure 6-23 shows the installation costsfor afterburners. Heat exchangers are con-

1" ITT I I IL

50


A HIGH-TEMPERATURE SYNTHETICS, WOVEN ANDFELT. CONTINUOUS AUTOMATIC CLEANING.

8 MEDIUM-TEMPEFATURE SYNTHETICS, WOVEN ANDFELT. CONTINJOUS AUTOMATIC CLEANING.

C -WOVEN NATURAL FIBERS. INTERMITTENTLYCLEANED -SIFGLE COMPARTMENT.

FIGURE 6-21. Annualized cost of operation of fabricfilters.

175

sidered accessory equipment and appear aspart of the installation cost. Installation costsmay range from 10 percent to 100 percentof the purchase costs, although in some sit-uations they may be as high as 400 percent.Differences in installation coats are due to100

50

T 1 1 1 1 1 1 1 1 1 1 1 1 1 1-31-

1

Il

1 1 1 1 1 1 1 1 1 1 1 1 1 1 11

5 10 100

GAS VOLUME THROUGH COLLECTOR, 103 ocfm

FIGURE: G -22. Purchase cost of afterburners.

11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 RI

5 10 50 100


CABHE . CATALYTIC AFTERBURNER WITH HEATEXCHANGER

DFHE DIRECT FLAME AFTERBURNER WITH HEATEXCHANGER

CABDF

CATALYTIC AFTERBURNERDIRECT FLAME AFTERBURNER

FIGURE 6-23. Installed cost of afterburners.

176

the differences in burner locations relativeto the emission source, and differences instructural supports, ductwork, and founde.-tions. Installation costs for the addition ofequipment to existing plant facilities willbe higher than similar costs for new plants.Other factors accounting for different in-stallation fees are the degree of instrumenta-tion required, engineering fees in manufac-turers' bids, startup tests and adjustments,heat exchangers, auxiliary fans, and utili-ties. The assumptions for calculating oper-ation and maintenance costs are as follows:

1. Annual operating time= 8760 hours2. Fuel cost:

$0.57/1000 acfm-hour for directflame afterburner with no heatrecovery$0.23/1000 acfm-hour for directflame afterburner with heat re-covery $0.28/1000 acfm-hour forcatalytic afterburner with noheat recovery$0.14/1000 acfm-hour for cata-lytic afterburner with heat re-covery

3. Maintenance cost:$0.06/acfm for direct flame af-terburner$0.20/acfm for ca talytic after-burner

4. Pressure drop throrgh all after-burner types =1 inch of water

5. Power cost =$0.011/W-hrCost comparisons presented in Figure 6-24

show that the direct flame afterburner with-out a heat exchanger is the most expensive.The tower curve in Figure 6-24 shows thatthe annualized cost of a (Erect flame after-burner with heat recovery is lower than thecost of a catalytic afterburuer without heatrecovery.

6.8 DISPOSAL OF COLLECTED PARTIC-ULATE EMISSIONS

6.8.1 General

The installation of any pollution controlsystem designed t) collect particulate mat-ter demands a decision regarding the dis-posal of the collected particulate material.

I I 111J111 I I 1 1 Ill)5 10 50 100


CABHE CATALYTIC AFTERBURNER WITH HEATEXCHANGER

DFH:. - DIRECT FLAME AFTERBURNER WITH HEATEXCHANGER

CAB CATALYTIC AFTERBURNEROF DIRECT FLAME AFTERBURNER

Frame 6-24. Annualized cost of operation of after-burners.

This section discusses the relevant factorsand illustrates the economic consequences ofdisposal of the collected material.

In the past, pollution control equipmentoften was installed either to reduce a severenuisance or to recover valuable material.Such equipment not only prevented valuablematerial from escaping to the atmospherebut also reduced costly cleaning of the plantgrounds and facilities.

As industrial plants become more crowdedtogether and as the public desires a higherquality of air, more emphasis will be placedon intensive control activities. This empha-sis will increase the demand for more effec-tive air pollution control. Generally, mostair pollution control systems collect materialthat has little economy, worth.

Basically, the Alternatives for handlingcollected particulate material are as follows:

1. Return the material to the process.2. Sell the material directly as collected.3. Convert the material to a saleable

product.4. Discard the material in the most eco-

nomical manner.

The process of selecting an alternativeshould take into account the following ques-tions:

1. Can the material be used within thecompany?

2. Is there a profitable market for thematerial?

3. What is the most economical methodof disposal?

4. is there land available for a landfill?5. is there a source of water available

for:a. a wet pipeline systemb. disposal at seac. transportation by barge

6. Is there space available for a settlingbasin or filtering system?

7. Ic there process-related equipmentpresently available for transportingor treating the collected material?

8. Is there access to a municipal wastetreatment system?

9. Can technology and/or markets bedeveloped for utilization of the wastematerial?

6.8.2 Elements of Disposal SystemsAfter examining feasible solutions to the

disposal problem, the least costly alternativethat is most compatible with other operat-ing factors in the plant should be chosen.The decision should result from considerationof each of the four functional elements ofthe disposal system described below and theirrelationships to the manufacturing process.

1. Temporary storage, which allowsgathering sufficient quantities of thecollected material to make final dis-posal more economical. The unit costof disposal usually is lower for greaterquantities. Temporary storage maybe convenient at many points in theoverall disposal scheme, such as in thehopper or settling chamber of a pollu-tion control device, or in a silo somedistance from the plant.

2. Transportation that moves the col-lected material from the particulatecontrol device to some location wheredisposal is relatively economical. Inmost cases, transportation displaces

177

the material to a location where ac-cumulation minimizes any potentialinterference with plant activities.Any single disposal system may re-quire more than one method of trans-porting the material. For example,a conveyor system may be used atthe control device, a truck may beused to transport the material to alandfill area, and a bulldozer may beused to push it to its final disposallocation.

3. Treatment that changes physicaland/o7 chemical characteristics foreasier disposal. Such treatment maysimplify operations and reduce costsfor handling and disposal of wastes.Frequently, for easier transport, par-ticulat;., matter is made into a slurryby adding water to it. This permitsthe use of a pipeline, which is oftenthe most economical method fortransporting wastes over long dis-tances. Slurries from wet scrubbingpollution control systems frequentlyare treated in an opposite manner:the water is removed and the par-ticulate mattes is concentrated by fil-tration or sedimentation. This per-mits the ultimate disposal of a solidwaste, rather than a sludge or aslurry. The method of treatmentshould be selected with a view tominimizing contamination of the ?,n-viromnent. Examples of such treat-ment methods are the wetting of finedust to prevent air pollution, the neu-tralization and filtration of slurriesto prevent contamination of receiv-ing waters, and the proper burial ofsolid material in a sanitary land-fill.

4. Final disposition, which pertains todiscarding the unusable material. Ma-terial which cannot be sold, con-verted, or re-used ultimately can bediscarded in landfills; or sometimesit can be disposed of in lagoons orthe sea.

The following list shows some examplesof the four functional elements for both wetand dry disposal systems:

178

A. Starage(1) Slurry of suspended particulate

matter in water(a) Settling basin(b) Lagoon(c) Tank

(2) Dry collected particulates(a) Mound(b) Rail car(c) Bin(d) Silo

B. Transportation(1) Slurry of suspended particulates

in water(a) Barge(b) Pipeline(c) Truck(d) Rail

(2) Dry collected particulates(a) Truck(b) Rail(c) Front-end loader(d) Conveying system(e) Barge

C. Treatment(1) Slurry of suspended particulate

in water "(a) Sedimentation(b) Filtration(c) Flotation(d) Thickening; wet combustion(e) Lagoons and drying beds(f) Vacuum filtration(g) Centrifugal,ion; incineration(h) Neutralization

(2) Dry collected material(a) Comjvessirg(b) Wetting

D. Final Disposition(1) Landfill

(a) Public or private disposalsites

(b) Quarry(c) Evacuated coal mine

(2) Lagoon(3) Dump at sea

The arrangement of these elements in anoverall disposal scheme is shown in Figure6-25. This flow diagram shows the move-ment of the collected material through vari-ous stages toward final disposal.

Environmental factors such as space, utili-

P RUCE SS

1120

PRODUCT

COLL ECTIONEQUIPMENT

STORAGE

TRANSPORTMETHOD

STORAGE

H2O

TREATMENTOPERATION

STORAGE

DISPOSAL METHOD

VII11111111101011p

CONVERSIONTO

SALEABLEPRODUCT

Finn 6-25. Flow diagram for disposal of collected particulate material from air pollution control equip-ment.

ties, disposal facilities, and the desired formof collected waste material usually have animportant bearing on the selection of a dis-posal system compatible with a specific typeof particulate pollution control equipment.Therefore, a specific type of particulate pol-lution control equipment may not always callfor the same waste disposal system.

6.8.3 Disposal Cost for Discarded Material

Table 6-9 describes various disposal sys-tems and the related costs within specific in-dustries. Each system listed is specificallydesigned to cope with the disposal problemand available facilities of the individual plantshown. Therefore, drawing general conclu-sions about the relative costs of systemslisted in the table ould be erroneous. Thedisposal costs shown include capital chargesand costs for labor and material. The dis-posal cost per ton will be higher the smaller

the quantity of material, because capitalcharges for investment in facilities will re-main the same regardless of quantity.

Fly ash, a residue from the combustionof coal and residual oil, probably is the mostcommon material collected in emission con-trol systems. An estimated 20 million tonsof fly ash was produced in the United Statesin 1965. Only 3 percent of this total was soldas a marketable product." If the cost fordiscarding the remaining 97 percent of thefly ash as unusable waste were $1.00 perton or more, this would represent a total costof $20 million or more. Based on the datain Table 6-9, a cost of $1.00 per ton is atypical unit cost.

In certain situations, the disposal cost offly ash can be a major portion of the totalannualized cost for a complete pollution. con-trol system (including dispcsal facilities).For example, the disposal costs can be as

179

Tab

le 6

-9.C

OST

S O

F SP

EC

IFIC

DIS

POSA

L S

YST

EM

S

Indu

stry

Col

lect

ed m

ater

ial

Tre

atm

ent

Tra

nspo

rtSt

orag

eFi

nal d

'apo

aal

Cos

t eitt

in_4

2,do

llars

/ton

Pow

er g

ener

atio

nFl

y as

hSe

dim

enta

tion

Pipe

line_

Settl

ing

pond

Lan

dfill

(F.

Nlim

ent)

_0.

-.-

5

Pow

er g

ener

atio

nFl

y as

hT

ruck

Mou

ndL

andf

ill0.

55Po

wer

gen

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ion

Fly

ash

Tru

ckM

ound

City

dum

p1.

11;

Pow

er g

ener

atio

n_Fl

y as

hFo

rm p

elle

tsV

acuu

m s

yste

m.

truc

k, b

a!ge

.T

rans

fer

bins

,st

orag

e si

lo.

Lan

dfill

or

dum

pat

sea

.2.

00

Pow

er g

ener

atio

nFl

y as

hFo

rm s

lurr

yPi

pelin

eSe

ttlin

g po

ndL

andf

ill (

Sedi

men

t)_

2.00

Pow

er g

ener

atio

nFl

y as

hW

ette

dPn

eum

atic

pip

elin

etr

uck.

Stor

age

silo

Lan

dfill

2.00

Pow

er g

ener

atio

n fo

r ch

emic

alpl

ant.

Fly

ash

Sedi

men

tatio

nPi

pelin

eL

agoo

n1.

60

Pow

er g

ener

atio

n fo

r ch

emic

alpl

ant.

Fly

ash

Tru

ckSi

los

Lan

dfill

0.90

Che

mic

alSl

urry

(10

0,00

0ga

l /da

y)B

arge

Tan

k_D

ump

at s

ea3.

00

Che

mic

alW

eak

acid

(la

rge

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me)

.B

arge

Tan

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ump

at s

ea_

_1.

00

Pow

er g

ener

atio

n fo

r pu

lp a

ndpa

per.

Fly

ash

Sedi

men

tatio

nPi

pelin

eL

agoo

n2.

30

Gra

y u

on f

ound

ry _

Cup

ola

dust

Wat

er c

lari

fica

tion_

Sedi

men

t by

truc

k_D

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ter

dum

p_L

andf

ill1.

40Pe

trol

eum

ref

inin

gN

on-d

ewat

erec

lsl

udge

.C

ontr

act h

aulin

g_L

andf

ill4.

75

Petr

oleu

m r

efin

ing

Dew

ater

ed s

ludg

e..

Con

trac

t hau

ling

Lan

dfill

2.50

Petr

oleu

m r

efin

ing

Slud

ge, f

ilter

cak

e,oi

ly s

olid

s.T

ruck

In-p

lant

land

fill_

_ . _

20.0

0

Petr

oleu

m r

efin

ing

Oily

sol

ids

Bar

geD

ump

at s

ea7.

50Pe

trol

eum

ref

inin

gC

atal

yst f

ines

Con

trac

t hau

ling_

Lan

dfill

2.75

Port

land

cem

ent_

Was

te d

ust

Slig

ht w

ettin

gC

onve

yor,

truc

k_B

ins

Lan

dfill

1.05

Soap

s an

d de

terg

ents

Susp

ende

d so

lids

Pipe

line

Mun

icip

al tr

eat-

men

t pla

nt.

2.50

high as 80 percent of the total annualizedcost for an emission control system witholder electrostatic precipitators which areno longer depreciated. The disposal cost stillcan he as high as 60 percent for similar sys-tems with newly installed electrostatic pre-cipitators, which usually have high depre-ciation charges,

Table 6-10 shows a summary of fly ash

Table 6-10, COST OF ASH DISPOSAL BY ELEC-TRIC UTILITIES

Disposal costs, dollars/tonType and collection method

Low Medium High

Fly ash (mechanicalcollector) $0.16 $0.69 $1.67

Fly ash (electrostaticprecipitator) 0.12 0.77 1,74

Bottom ash 0.16 1.04 4.76

disposal costs for material collected fromelectrostatic precipitators and mechanicalcollectors installed in electric utilities and istaken from a recent survey." This surveyanalyzed the costs of disposal, the sales, andthe uses of fly ash collected by 54 electricutilities and reported an average disposalcost of $0.74 per ton. Analysis of the datafor individual utilities revealed that disposal

fY

-1-J00

1

ASSUME: CFM, GRAIN LOADING CONSTANT

cost is partly a function of geographical lo-cation. The average disposal cost per ton inthe heavily-populated East is higher tht.athat reported elsewhere.

6.8.4 Return of Collected Material to theProcess

In some process operations, collected ma-terial is sufficiently valuable to warrant itsreturn to the process In these situations, thevalue of the recovered ma'erial can partiallyor wholly pay for the collection equipment.In many applications, however, the cost forthe high efficiency control systems necessaryto achieve desired ambient air quality willbe greater than the revenue returned for re-covery of the material collected. This is illus-trated by the hypothetical example in Fig-ure 6-26.

The figure shows a linear relationship be-tween collection efficiency and value of ma-terial recovered. It also shows a curvilinearrelationship between collection efficiency andrelated equipment costs. Up to the break-even point D (which corresponds to an effi-ciency of about 97 percent), the recoveryvalue of material collected is greater thanthe cost to achieve the recovery. Equipmentdesigned for efficiencies greater than 97 per-cent, according to the curve, would have ahigher cost than the potential recovery value.

I

VALUE OF ..:ATERIALRECOVERED

PROFIT MAXIMUM

BREAK EVENPOINT

"PROFIT"

65 70 75 80

EFFICIENCY, %

85 90 95

FIGURE 6-26. Theoretical effect of dust value on control cost.

181.

100

If profit were the only control incentive, 85percent collection efficiency would achieve themaximum profit, as illustrated by the profitline AB. If however, emission standardsmade 97 percent collection efficiency neces-sary, no profit would be achieved at thebreak-even point D. For collection efficiencygreater than 97 percent, equipment costswould exceed recovery costs. At 99 percentefficiency, for example, control equipmentwould cost the amount shown by FII, andthe value recovered would be the amout.tGIL The difference FG would represent anexpense and can be considered as the netcontrol cost.

The cement industry is one example wherereturn of the collected material to the proc-ess is commonly practiced. A survey con-ducted in 1956 shows that, out of 383 kilns,a total of 349 return collected dust to theprocess." Not only does recovered dust, insuch situations, have value as a raw material,but its recovery also reduces disposal costsand decreases other related costs for thepreparation of raw materials used in theprocess.'1

6.8.5 Recovery of Material for Sale

Although material collected by air pollu-tion control equipment may be unsuitablefor return to a process within the plant, itmay be suitable for enother manufacturingactivity. Hence, it may be treated and soldto another firm that can use the material.Untreated pulverized fly ash, for example,which ca: not be reused in a furnace, can besold as a raw material ton cerneht manu-facturer. It also can be used as a soil con-ditioner, or as an asuhalt filler, or as land-fill material. For such uses, pulverized flyash requires no treatment ard can be soldfor as much as $1.00 per ton. Pulverized flyash which is treated can yield an even morevaluable product. A !milted number of u ili-ties, for example, sinter pulverised fly ashto prodJee a lightweight aggregate whichcan be used to manufacture bricks and light-weight building blocks.

At the present time, however, the sale ofraw or treated collected process material us-

182

ually does not offer an opportunity to offsetcontrol costs to a significant extent,


1. Wilson, E. L. "Statement Presented at Hearingsbefore the Subcommittee on Air and Water Pol-lution of the Committee on Public Works, U.S.Senate, 90th Congress, First Session on S. 780,Part 4." U.S. Government Printing Ofnce, Wash-;ngton, D.C., 1967. p. 2639.

2. Danielson. John A. (ed.) "Air Pollution Engi-neering Manual." U.S. Dept. of Health, Educa-tion, and Welfare, National Center for Air Pol-l:Won Control, Cincinnati, Ohio, PIES- Pub -999-AP -40, 1967.

3. "Air Pollution Manuall'art 11Control Equip-ment." American Industrial Hygiene Association,Detroit, Michigan, 1968.

4. "Census of Manufacture 1963." Volumes 1, 2,and 3, U.S. Bureau of Census.

6. Ridker, Ronald G. "Economic Costs of Air Pol-lution." Frederick A. Praeger Publishers, NewYork, 1967.

6. Semrau, Konrad T. "Oust Scrubber DesignACritique on the State of the Art." J. Air Poi-;ntion Control Assoc., Vol. 18, pp 687-504, Dec.1963.

7. Sandomiraky, Alex G., Benforado, D. M., Grames,L. D., and Paulette, C. E. "Fume Control inRubber Processing by Direct-Flame Incinera-tion." J. Air Pollution Control Assoc., Vol. 16,pp. 673-676, Dec. 196F.

8. Hein, Glen M. "Odor Control by Catalytic andIlighTemperature Oxidation." Annals, NewYork Academy of Science, 114(2) :6,.6-662, July1964.

9. "No. th Amerit-an Combustion Hanbook." h:edition, North Amer ', an ManCacturing Co.,CLIveland, Ohio.

10. broker, L. P. "Odor Control by Incineration."(Presented at the Meeting of the Middle StatesAir Pollution Control Association Section, Nov.1A5.)

11. Eckenfelder. W. Wesley. "Industrial Water Pol.lotion Control." McGraw-Hill, New York, 1966,p 4.

12. Gatr.t,s, Gerard C. "Report on Flyash in England,Europe, and Soviet Union." Research Div. Li-brary, Consolidated Coal Co., July 1, 1966, p. 1.

19. "59 Utilities Give Data on FlyasS Sates andUses." Electrical World, Vol. 168, pp. 61-63,Aug. 21, 1967.

14. Kennewurt, A. S. and Ciaysen, C. F. "1956 Sur-vey, Portland Cement Associatioti" Report MP-54, Chicago, May 1958, p. 37.

lb. Gale, W. M. "Technical Aspects of a ModernCement Plant." Clean Air, (2)!7-18, 1967.

7. CURRENT RESEARCH IN CONTROL OF PARTICULATE MATTER

A total of 501 identified projects relatingto air pollution research were active in 1966.'Of these projects, only 16 related directly toresearch on the control of particulate matter.Five of the 16 projects were financed by theFederal Government (both as in-house andcontract projects), and the rest were per-formed by control equipment manufacturers,public utilities, and some of the larger basicindustries.

To provide the research and developmentnecessary to keep pace with the particulatepollution problem and the increasing require-ments for improved control, the NationalMr Pollution Control Administration (NA-PCA has undertaken a series of pollutiondevice development system studies. Thesestudies will be conducted by industrial or-ganizations under contract to NAPCA. Theirpurpose is to systematically identify andcarry out research needed to improve theperformance and extend the application ofmajor pollution control equipment.

These studies include research on high-temperature bag filtration directed towardincreasing bag life and determining themechanisms that cause bags to rupture.'Additional studies are under way to deter-mine performance under various dust inletfeed modes and the effects on filtration ofparticle size distribution along the filter bag.In another study, the potential of fabricfilters for controlling fly ash emissions fromt)wer plants burning pulverized coal .vas!nvestigated.'

Combustion research at the NAPCA in-cludes an evaluation of emissions from apilot trench incinerator.' Laboratory investi-gations into the effects of fuel additives,burner operation, and burner modificationson particulate emissions from oil combustionare being conducted.'

Five basic types of wet scrubbers are be-

ing studied in an attempt to relate collec-tion efficiency to cost of operation, to im-prove scrubber effectiveness in the controlof incinerator emissions, and to evaluate thescrubber as a gas-liquid contactor. A 100 -to 500-cfm test unit was constructed to carryout these investigations.'

Contract studies currently being conductedby NAPCA pertain to systems analysisstudies covering Loth theory and applicationof the various modes of control of particu-late matter.

A research program in the field of high-temperature electrostatic precipitation is be-ing conducted by the U.S. Bureau of Mines.Data from a pilot plant at which fly ash iscollected show collection efficiencies in the90 to 98 perceti% range at a temperature of1460°F. and a pressure of 80 psig.t

Research by universities and manufac-turers is under way to determine the effectsof sparking rates and gas and dust flow oncollection efficiencies of electrostatic. precipi-tators.'.'

Wet scrubber research includes a study ofthe parameters affecting particle collectionin a venturi scrubber '° and removal of par-ticles by foam in a sieve plate column." In-vestigations into the performance param-eters of the flooded disc scrubber have beenreported." "

Cloth filtration application studies by pri-vate companies are under way on large oil-and coal-fired steam generators "." and sin-ter plants."

Additional research is being conducted byequipment manufacturers in an effort to im-prove technology on the collection of par-ticulate matter.

The October 1968 issue of the Journal ofthe Mr Pollution Control Association is de-voted entirely to current aerosol researchprogress reports.

188


1. "Guide to Research in Air Pollution." U.S. Dept.of Health, Education, and Welfare, NationalCenter for Air Pollution Control, Washington,D.C. PHS-Pub-981.1966.

2. Spaite, P. W. and Harrington, R. E. "Enduranceof Fiberglass Filter Fabrics." J. Air PollutionControl Assoc., 77(6) :310-313, :day 1967.

3. Borgwardt, R. H., Harrington, R. E., and Spaite,P. W. "Filtration Characteristics of Fly Ashfrom a Pulverized Coal Fired Power Plant." J.Air Pollution Control Arsoc., 18(6) :387-390,June 1960. (Presented at the 60th Annual Meet.ing of the Air Pollution Control Association,Cleveland, Ohio, June 1967, Paper No. 67-36.)

4. Burckle, J. 0., Dorsey, J. A., and Riley, B. T."The Effects of the Operating Variables and theRefuse Types on the Emissions from a PilotScale Trench Incinerator." In: Proceedings ofthe 1968 National Incinerator Conference, American Society of Mechanical Engineers, Ns. York,pp. 34-41.

6. Watser, J. H., Hangebrauck, R. P., and Schwartz,A. J. "Effect of Air.Fuel Stoichiometry on AirPollutant Emissions from an Oil Fired TestFurnace." J. Air Pollution Control Assoc.. 18(5) :332-337, May 1968.

6. Private communication from Chief, ControlEquipment Research Unit, Process Control En-gineering Program, National Center for Air Pollution Control, 1968.

7. Shale, C. C. "Progress in High TemperatureElectrostatic Precipitation." J. Air PollutionControl Assoc., 17(3) :1159-160, March 1967.

184

8. Penney, G. W. "Electrostatic PrecipitationStudies at Carnegie Institute of Technology." J.Air Pollution Control Assoc., Vol. 17, pp. 588-689, Sept. 1967.

9. Robinson, M. "Electric Wind Turbulence in Elec-trostatic Precipitation." J. Air Pollution ControlAssoc., Vol. 17, pp. 605-606, Sept. 1967.

10. Theodore, L. "A Study of Venturi Scrubbers." J.Air Pollution Control Assoc., 17(9) :598-599,Sept. 1967.

11. Taheri, M. and Calvert, S. "Removal of SmallParticles from Air by Foam in a SievePlateColumn." .. Air Pollution Control Assoc., 18(9):240-245, April 1968.

12. Walker, A. B. and Hall, R. M. "Operating Ex-perience with a Flooded Disc Scrubber- A NewVariable Throat Orifice Contactor." J. Air Pol-lution Control Assoc., 18(5):319-323, May 1968.

13. Orr, C., Burson, J. H., and Keng E. Y. 11 "Aer-osol Research in Chemical Engineering atGeorgia Tech." J. Air Pollution Control Astoc.,17(9) :690-592, Sept. 1967.

14. Felgar, D. N. and Ballard, W. E. "First YearsExperience with Full -Scald Filterhouse atAlamitos Bag Filterhouse." Southern CaliforniaEdison Company, Los Angeles, 1965.

16. Smith, R. 1. "Baghowe Collectors on Oil andCoal Fired Steam Generating Plants." PublicElectric and Gas Company, Newark, New Jersey.(Unpublished.)

16. Smith, J. H. "Testin, Feasibility of Baghouse onWindbox End of Sinter Plant." Kaiser SteelCorp., Fontana, California. (Unpublished.)

B. BIBLIOGRAPHY

The following bibliography contains a broadlisting of articles pertaining to particulateair pollution control. The articles are ar-ranged according to specific source categor-ies. The following arrangement of categoriesis intended to aid the reader in locating ar-ticks in specific areas.

Food and Agricultural Sources:Page

Coffee Roasting 206Cotton Ginning 206Feed and Grain 207Fish Meal Processing . 207Other 207

Intern21 Combustion Engines:Piston EnginesGasolineAutomotive

TypePiston EngincsDiesel

Heat and Power Sources:Coal Combustion

,,,,Oil CombustionGas CombustionNuclear Power

Refuse Disposal Sources:Open BurningMunicipal Ineineratots

........... ......OnSite Incinerators......Other Disp sal Methods

Metallurgical Process Sources:AluminumCopperIron and SteelLeadZinc

Chem;cal Process Sources:Mineral AcidsPulp and PaperOil RefineriesPaint and VarnishPlastics and ResinsOther Chemicals

Mineral Process Sources:Ritumino-is Concrete ManufacturingCalciu al CarbideCement.Concrete Batch PlantsCeramic, Clay, and RettattotiesGlass and Frit .

Gypsum . .

LimePits and QuarriesOther

') pc

185187

188192193193

191191195197

197198198201201

201202202203203203

204204204203205205205205205206

IN'TEIINAL COMBUSTION ENGINES

Piston Erigincs--Gasoline--Automotive TypeBeckman, E. W., Fagley, W. S., and Sarto,

J. 0. "The Cleaner Air Package ExhaustEmission Control by Chrysler." In: Hear-ings before the Subcommittee on Air andWater Pollution of the Committee on Pub-lie Works, U.S. Senate, 90th Congress,1st Session, Feb. 13-14 and 20-21, 1967,pp. 411-424.

Bush, A. G., Glater, R. A., Dyer, J., andRichards, C. "The Effects of Engine Ex-haust on the Atmosphere When Automo-biles Are Equipped with .Afterbniners."Univ. of Calif. Report 62-63, Dept. of En-gineering, Los Angeles, Dec. 1962, 38 pp.

Derndinger, Hans-Otto. "Motor Vehicle En-gines." [Kraftfahrzeugmotoren.) VIM (Ver.

Deut. Ingr.) Z. (Duesseldorf), 108(19):842445, July 1966. (Text in German.)

Ebersole, G. D. and McReynolds, L. A. "AnEvaluation of Automobile Total Hydrocar-bon Emissions." In: Vehicle Emissions,Part 11, SAE Progress in Technology Se-ries, Society of Automotive Engineers,New York, 1966, Vol. 12, pp. 413-428.(Presented at Mid-Year Meeting, Societyof Automotive Engineers, Detroit, Michi-gan. June 6-10, 1966, Paper 66048.)

Eldib, I. A. "Problems in Air Pollution andTheir Solutions with New Technology,"In: Technical and Social Problems of AirPollution, Symposium of Metropolitan En-gineers Council on Air Resources, NewYork, 1966, pp. 7-28.

185

Fiala, E. and Zeschmann, E. G. "The Ex-haust Gas Problem of Motor Vehicles,Part I." (Zum Abgasproblem der Strassen-fahrzeuge, Teil 1.] Automobiltech. Z.

(Stuttgart), 67(9:302-308, Sept. 1965.

Fiala, E. and Zeschmann, E. G. "The Ex-haust Gas Problem of Motor Vehicles,Part II." (Zum Abgasproblem der Stras-senfahrzeuge, Tell 2.] Automobiltech. Z.(Stuttgart), 67(12):419-422, Dec. 1965.

"The Control of Automobile Emissions(Ford Crankcase Emissions Control Sys-tem, Ford Thermactor System for Ex-haust Control)," Ford Motor Co., Dear-born, Michigan, 1966, 6 pp.

Gardner, J. W. "Automotive Mr Pollution."8rd Report of the Secretary of Health, Ed-ucation, and Welfare to the U.S. CongressPursuant to Public Law 88-206, The CleanAir Act, 89th Congress, 2nd Session, Docu-ment No. 83, March 26, 1966, 17 pp.

Grant, E. P. and Nissen, W. E. "California'sProgram for Motor Vehicle Emission Con-trol." In: Proceedings, International CleanAir Congress, Part I, London, 1966, PaperV11/19. pp. 210-212.

Heinen, C. M. "The Developmett and Manu-facture of Control Equipment." Arch. En-viron. Health, 1A(1) :98-104, Jan. 1968.

Ilirao, 0. "Problems of Air Pollution Dueto Vehicle Emission Gases." J. Japan Soc.of Mechanical Engineers (Tokyo), 69-(676):1568 -1672, 1966.

Hunigen, E., Jaskulla, N., and Wettig, K."The Reduction of Carcinogenic Contami-nants in Exhaust Gases of Petrol Enginesthrough Fuel Additives ar.d Choice of Lu-bricants." In: Proceedings, InternationalClean Air Congress, Part I, London, 1966,Paper VI/12, pp. 191-193.

Jackson, M. W. "Effects of Some EngineVariables and Control Systems on Com-position and Reactivity of Exhaust Hy-drocarbons." In: Vehicle Emissions, PartII, SAE Progress in Technology Series,Vol. 12, Society of Automotive Engineers,New York, 1966, pp. 241-247.

Jackson, W. E. "Air Pollution from Automo-Mar; in Philadelphia." Preprint. (Pre-sented at the 68th Annual Meeting of theAir Pollution Control Association, Toron-

36

to, Canada, June 20-24, 1965, Paper 65-137.)

Jensen, D. A. "Sources and Kinds of Con-taminants from Motor VehiclesInform-ative Report No. 4." J. Air Pollution Con-trol Assoc., 14 (8) :327-328, Aug. 1964.

Jensen, D. A. "Separating Fact from Fic-tion in Auto Smog Control." Arch. En-viron. Health, 1.4(1):150 -154, Jan. 1967.(Presented at the American Medical Asso-ciation Air Pollution Medical ResearchConference, Los Angeles, March 2-4,1966.)

Kopa, R. D., Tribus, M., Scope, S., and Treat,R. "Exhaust Control Devices: An Investi-gation of Exhaust 'Scrubbing' Devices."In: 1st Report of Air Pollution Studies,Univ. of Calif. at Los Angeles, Dept, ofEngineering, July 1955, 22 pp.

Larsen, R. I. "Motor Vehicle Emissions anuTheir Effects." Public Health Rept.,77(11):963-969, Nov. 1962.

Lohner, Kurt, Muller, Herbert, and Zender,W. "About the Process Technique for theCombustion of Exhaust Gases in GasolinrEngines in Stationary Operations." (Uberdie Verfahrenstechnik der Nachvei bren-flung der Abgase von Ottomotoren bei sta-tiontirem Betrieb.) VIM (Ver. Deut Ingr.)Z. (Duesseldorf), 109(81):1488, Nov.1967. (Text in German.)

Ludwig, J. II. "The Vehicle Pollution Prob-lem." Preprint. (Presented at the Amer-ican Public Power Association Conference,Denver, Colo., May 8-11, 1967.)

Ludwig, J. H. "Progress in Control of Ve-hicle Emissions." J. Sanit. Eng. Div., Am,Soc. Civil Engrs., 93 (SA-4):73-79, Aug.1967.

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HEAT AND POWER SOURCES

Cool Combustion

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"Restricting bust Emission from Natural-Draft Steam Generators, Capacity 25ton/hr and Less, Lignite-Fired with Sta-tionary or Mechanical Grates." [Stanbaus-wurf Dampferzeuger Ober 10 t/h LeistungBraunkohlen-Rostfeuerungcn feststehendeRoste oder mechanische Roste ohne Un-terwind.] VDI (Verein Deutscher In-genieure) Kommission Reinhaltung derLu ft, Duesseldorf, Germany, VDI No. 2098,July 19 i8, 17 pp. (Translated from Ger-man.)

"Restriction of Dust Emission in Anthra-cite-Briquet Factories." [Staubauswurf-begrenzung Steinkohlen-Brikettfabriken.]%PI)! (Verein Deutscher Ingenieure) Kom-mission Reinhaltung der Luft, Duessel-

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Schueneman, J. J. "Air Pollution from Useof Fuel Curren'. Status and Future ofParticulate Emissions Control." Nat.Engr., 69 (3)11-12, March 1965.

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Krikau, F. G. "Effective Solids Removal forBasic Oxygen Furnace Flue Dust Pollu-tion Control." (Presented at the 28th An-nual Meeting, American Power Confer-ence, April 26-28, 1966.)

Lemke, E. E., Hammond, W. F., and Thomas,G. "Air Pollution Control Measures forHot Dip Galvanizing Kettles." J. Air Pol-lution Control Assoc., 10 (1) : 70-77, Feb.1960.

Lloyd, H. B. and Bacon, N. P. "OperatingExperience with Oxygen-Assk,i.ed Open-Hearth Furnaces." In: Fume Arrestment,Special Report 83, William Lea and Co.,London, 1964, pp. 65-70.

Loszek, W. "The Problem of MaintainingClean Air in a Zone Polluted by WasteGases from Metallurgical Works." In:Part I, Proceedings of the InternationalClean Air Congress, London, 1966, PaperIV/10, Pp. 105-111.

Mitchell, R. T. "Dry Electrostatic Precipita-tors and Waagner-Biro Wet Washing Sys-tems." In: Fume Arrestment, Special Re-port 83, William Lea and Co., London,1964, pp. 80-85.

Namy, G., Dumont.Fillon, J., and Young,P. A. "Gas Recovery Without Combustion

199

from Oxygen Converters: The II12,1D-CAFL Pressure Regulation Process." In:Fume Arrestment, Special Report 83, Wil-liam Lea and Co., London, 1964, pi). 98-103.

Ochs, II. I. "Purification of Air in RollingMills." [Umluftreinigung in Walz-Betrie-ben.] Metall. (Germany), 19 (4) :348-351,April 1965.

Pallinger, J. "A New Wct Method for Sepa-ration of Very Fine Dust." Staub (Dus-seldorf) , 22(7 ): 270-275, 1962.

Parker, C. M. "BOP Air Cleaning Experi-ences." J. Air Pollution Control Assoc.,16(8): 446-448, Aug. 1966.

Pottinger, J. F. "The Collection of DifficultMaterials by Electrostatic Precipitation."Australian Chem. Process Eng. (Sidney),20(2): 17-23, Feb. 1967.

Punch, G. "LD and Kaldo Fume CleaningCONSETT Developments." Iron and Steel(London), 38(2): 75-80, 86, Feb. 1965.

Rabe!, G., Neuhaus, H., and Vettebrodt, K."The Wetting of Dusts and Fine Ores forthe Purpose of Reducing Dust Formation."Staub (English translation), 25(6) :4-8,June 1965.

"Restricting Emission of Dust, Tar Mist andGas when Charging Coke Oven" [Aus-wurfbegrenzung fir Staub, Teernebel undCase beim Ftillen von Koksofen; Kokereienund Gaswerke.] VDI (Verein DeutscherIngenieure), Kommission Reinhaltung derLuft, Diisseldorf, VDI 2302, June 1962,26 pp.

Sem, M. 0. and Collins, F. C. "Fume Prob-lems in Electric Smelting and Contribu-tions to Their Solution." J. Air PollutionControl Assoc., 5 (3): 157-158, 187, Nov.1955.

Schneider, R. L. "Engineering, Operationand Maintenance of Electrostatic Precipi-tators in Open Hearth Furnaces." J. AirPollution Control Assoc., 13 (8) :348-353,Aug. 1963.

Schueneman, J. J., High, M. D. and Bye,W. E. "Air Pollution Aspects of the Ironand Steel Industry." U.S. Dept. Health,Education and Welfare, Div. of Air Pol-lution, Cincinnati, Ohio, PHS-Pub-999-AP-1, June 1963, 129 pp.

Smith, J. H. "Air Pollution Control in Oxy-

200

gen Steelmaking." J. of Metals, 13(9):-632 -634, Sept. 1961.

Smith, W. M. and Coy, D. W. "Fume Collec-tion in a Steel Plant." Chem. Eng. Progr.,62(7):119 -123, July 1966.

Spenceley, G. D. and Williams, D. I. T."Furneless Refining with Oxy-Fuel Burn-ers." Steel Times (London), 193(5115): -150-158, July 29, 1966.

Storch, 0. "Experiences with the Applica-tion of Wet Collectors in the Iron and SteelIndustry." [Erfahrungen mit der Anwen-dung von Nassabscheidern in Eisen andStahlhiitten- Werken.] In: Part I, Proceed-ings of the International Clean Air Con-gress, London, )66, Paper V/2, pp. 119-122.

Starch, O. "A New Venturi ScrubLzr to Sepa-rate Dust Particles less than 1 Micron,Especially of Brown Smoke." Staub (Eng-lish translation), 26(11): 32-34, Nov.1966.

Sullivan, J. L. and Murphy, R. P. "The Con-trol of Fume from a Hot Blast Cupola byHigh Energy Scrubbing without Appre-ciable Thermal Buoyancy Loss." In: Part1, Proceedings of the International CleanAir Congress, London, 1966, Paper V/10,pp. 144-146.

Thom, G. W. and Schuldt, A. F. "The Col-lection of Open Hearth Dust and Its Recla-mation Using the SL/RN Process." Can.Mining and Met. Bull., 59 (654) :1229-1233, Oct. 1566.

Tulcinsky, S. and Lemaire, A. "Cooling andScrubbing of Smoke Emitted by LD SteelConverters in Sidmar Ironworks." Rev.de Metallurgie (France), 63 (9) : 659-665,Sept. 1966.

Underwood, G. "Removal of Sub-Micron Par-ticles from Industrial Gases, Particularlyin the Steel and Electricity Industries."International J. of Air & Water Pollution,Vcl. 6, pp. 229-263, 1962.

Wheeler, D. H. "Fume Control in L-D Piant."Preprint. (Presented at the 60th AnnualMeeting, Air Pollution Control Associa-tion, Cleveland, Ohio, June 11-16, 1967,Paper 67-96.)

Wheeler, D. H. and Pearse, D. J. "Fume Con-trol Instrumentation in Steelmaking Proc-

esses." Blast Furnace Steel Plant, 53-(12): 1125-1130, Dec. 1965,

Willett, II. P. "Cutting Air Pollution ControlCosts." Chem. Eng. Progr., 63 (3) : 80-83,March 1967.

Yokomiyo, K. "Air Pollution PreventionEquipment Installed in Muroran Steel andIron Works, Ltd." Clean Air Heat Man-agement (Tokyo), 15(7-8): 19-28, Aug.1966.

LeadDanielson, J. A. (ed.) "Air Pollution Engi-

neering Manual." U.S. Dept. of Health, Ed-ucation, and Welfare, National Center forAir Pollution Control, Cincinnati, Ohio,PHS-Pub-999-AP-40, 1967, 892 pp.

Snowball, A. F. "Development of an AirPollution Control Program at Cominco'sKimberley Operation." J. Air PollutionControl Assoc., 16(2, 3: 62, Feb. 1966.

"Restricting Dust and Sulfur-Dioxide Emis-sion from Lead Smelters." [Auswurfheg-renzung Bleihtitten.] VDI (Verein Deut-scher Ingenieure), Kommission Reinhal-tung der Luft, Duesseldorf (English trans-lation), VDI 2285, Sept. 1961.

ZincAllen, G. L., Viets, F. H., and McCabe, L. C.

"Control of Metallurgical and MineralDusts and Fumes in Los Angeles County,Calif." Bureau of Mines, Washington,D.C., Information Circular 7527, April1952, 79 pp.

Danielson, J. A. (ed.) "Air Pollution Engi-neering Manual." U.S. Dept. of Health,Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati,Ohio, PHS-Pub-999-AP-40, 1967, 892 pp.

"Restricting Emission of Dust and Sulfur-Dioxides in Zinc Smelters." [Auswurf-begrenzung Zinkhiitten.] VDI (VereinDeutscher Ingenieure), Kommission Rein-haltung der Luft, Duesseldorf, VDI 2284,Sept. 1961, 27 pp.

CHEMICAL PROCESS SOURCES

Mineral AcidsNitric Acid"Atmospheric Emission from Nitric Acid

Manufacturing Processes." U.S. Dept. of

Health, Education, and Welfare, Div. ofAir Pollution, Cincinnati, Ohio, PHS-Pub-999-AP-27, 1966, 89 pp.

"Nitric Acid Manufacture-Informative Re-port No. 5." J. Air Pollution Control As-soc., 14 (3) :91-93, March 1964.

Toyama, T. "Air Pollution and Health Im-pediment." Japan J. Ind. Health (Tokyo),8(3) :45-48, March 1966.

Zanon, D. and Sordelli, D. "Practical Solu-tions of Mr Pollution Problems fromChemical Processes." [Realizzazioni nelcampo della prevenzione dell'inquinamentoatmosferico di origine industriale.] Chim.Incl. (Milan), (English translation), 48-(2) :251-261, March 1966.

Phosphoric AcidBrink, J. A., Jr., Burggrabe, W. F., and

Greenwell, L. E. "Mist Removal from Com-pressed Gases." Chem, Eng. Prog., 62 (4) :-60-65, April 1966.

Danielson, J. A. (ed.) "Air Pollution Engi-neering Manual." U.S. Dept. of Health,Education and Welfare, National Centerfor Air Pollution Control, Cincinnati, Ohio,PHS-Pub-999-AP-40, 1967, 892 pp.

Sulfuric AcidArkhipov, A. S. and Boystsov, A. N. "Toxic

Air Pollution from Sulfuric Acid Produc-tion." Gigiena Sanit. (English transla-tion), Vol. 31, pp. 12-17 Sept. 1962.

"Atmospheric Emissions from Sulfuric AcidManufacturing Processes." U.S. Dept. ofHealth, Education, and Welfare, Div. ofAir Pollution, Cincinnati, Ohio, PHS-Pub-999-AP-13, 1965, 127 pp.

"Blocks Air Pollution. Snares 1700 lb. ofH,SO4 per Day." Chemical Proc., Feb.1962,

Brink, J. A., Jr., Burggrabe, W. F., andRauscher, J. A. "Fiber Mist Eliminatorsfor Higher Velocities." Chem. Eng. Prog.,60 (11) : 68-73, Nov. 1964.

Brink, J. A., Jr. "Air Pollution Control withFibre Mist Eliminators." Canadian J. ofChem. Eng., Vol. 41, pp. 134-138, June1963.

Brink, J. A., Jr., Burggrabe, W. F., andGreenwell, L. E. "Mist Removal from Com-pressed Gases." Chem. Eng. Prog., 62-(4): 60-65, April 1966.

201

Danielson, J. A. (ed.) "Air Pollution Engi-neering Manual." U.S. Dept. cf Health,Education, and Welfare, National Cen-ter for Air Pollution Control, Cincinnati,Ohio, PITS- Pub 999- AP -40, 1967, 892 pp.

Meinhold, T. F. "Three -Way Payout forII,SO, Gas Cleaner." Chem. Proc., 29 (3) : -63 -64, March 1966.

Stastny, E. P. "Electrostatic Precipitation."Chem. Prog., 62 (4) :47-50, April 1966.

Stopperka, K. "Electroprecipitation of Sul-furic Acid Mists from the Waste Gas of aSulfuric Acid Production Plant." Staub(English translation), 25 (11) :70-74, Nov.1965.

"Teflon Monofilament Cleans Up Acid StackGases." Chem. Eng., 72(22):112 -i11, Oct.25, 1965.

Toyama, T. "Air Pollution and Health Im-pediment." Jaan J. Ind. Health (Tokyo),8 (3):45-I8, March 1966.

Willett, H. P. "Cutting Air Pollution ControlCosts." Chem. Eng. Prog., 63(3):80 -83,March 1967.

Zanon, D. and Sordelli, D. "Practical Solu-tions of Air Pollution Problems fromChemical Processes." [Realizzazioni nelcampo della prevenzione dell'inquinamentoatmosferico di origine industriale.] ChinaInd. (Milan) (English translation), 48-(2) :251-261, March 1966.

Pulp and PaperBlosser, R. 0. and Cooper, H. B. H. "Par-

ticulate Matter Reduction Trends in theKraft Industry." National Council forStream Improvement, Atmospheric Pollu-tion Technical Bulletin 32, New York,April 4, 1967, 26 pp.

Boyer, R. Q. "The Western PrecipitationRecovery System." Tappi, 43 (8) :688-698,Aug. 1960.

Collins, T. T., Jr. "The Venturi Scrubber onLime 1Liln Stack Gases." Tappi, 42 (1) : 9-13, Jan. 1959.

Cooper, S. R. and Haskell, C. F. "CuttingChemical Ash Losses in a Kraft RecoverySystem." Paper Trade J., 151(13) :58,March 27, 1967.

Gehm, H. W. Statement Presented at theHearings before Subcommittee on Air andWater Pollution of the Committee on Pub-

202

.*

lic Works, U.S. Senate, 90th Congress,1st session on S. 780, May 15-18, 1967,Part IV, 1)1). 2361-2382.

Harding, C. 1. and Landry, J. E. "FutureTrends in Air Pollution Control in theKraft Pulping Industry." Tappi, ;9(8) :-61A -67A, Aug. 1966.

Landry, J. E. and Longwell, D. H. "Advancesin Air Pollution Control in the Pulp andPaper Industry." Tappi, 48(0:66A-70A,June 1965.

Owens, V. P. "Considerations for Future Re-covery Units in Mexican and Latin Amer-ican Alkaline Pulping Mills." Combustion,38 (5) :38-11, Nov. 1966.

Saha, I. S. "New Flue-Gas Scrubbing SystemReduces Air Pollution." Chem. Eng., 24-(7) :84 -86, March 27, 1967.

Stuart, II. H. and Bailey, R. E. "Perform-ance Study of Lime Kiln and Scrubber In-stallation." Tappi, 48(5) :101A-108A, May1965.

Walker, A. B. "Enhanced Scrubbing of BlackLiquor Boiler Fume by Electrostatic Pre-agglomeration: A Pilot Plant Study." J.Air Pollution Control Assoc., 13 (12) : 622-627, 1963.

Oil Refineries"Atmospheric Emissions from Petroleum Re-

fineriesA Guide for Measurement andControl." U.S. Public Health Service, Div.of Air Pollution, Cincinnati, Ohio, 1960,64 pp.


Gammelgard, P. N. "Current Status and Fu-ture ProspectsRefinery Air PollutionControl." Proc. of the National Confer-ence on Air Pollution, Washington, D.C.,Dec. 13, 1966, pp. 260-263.

Harrison, A. F., Louden, W. L., and Jones,G. "The Disposal of Chemical Effluentsfrom Refineries Utilizing Acid TreatmentProcesses." [Die Aufbereitung von Raf-finerieabwassern aus der Siiure-Raffina-tion] Erdal Kohle (Hamburg), 19 (8) : -587-591, Aug. 1966.

Hess, K. and Stickel, R. "Soot-Free Combus-

tion of Petrochemical Waste Cases." [Zurrussfreien Verbrennung petrochemischerAbgasel Chem. Ng. Tech. (Weinheim),39(5-6:331-310, March 20, 1967.

Kropp, E. P. and Simonsen, R. N. "Scrub-bing Devices for Air Pollution Control."Paint Oil Chem. Rev., 115(14):11, 12, 16,July 3, 1952.

London, D. E. "Requirements for Safe Dis-charge of Hydrocarbons to Atmosphere."In: Proceedings of Midyear Meeting,American Petroleum Institute, Div. of Re-fining, Philadelphia, Pa., May 15, 1963,Section III. 43, 1963, pp. 418, 433.

Miller, P. D., Jr., Hibshman, II. J., and Con-nel, J. R. "The Design of Smokeless Non-luminous Flares." In: Proceedings of the23rd Midyear Meeting, American Petro-leum Institute, Div. of Refining, Los An-geles, Calif., May 14, 1958, Section III,pp. 276-281.

"The Petroleum Refining IndustryAir Pol-lution Problems and Control Methods, In-formative Report No. 1." J. Air PollutionControl Assoc., 14 (1) : 30-33, Jan. 1964.

Rose, A. H., Jr., Black, H. H., and Wanta,R. C. "Air and Water Pollution StudiesRelated to Proposed Petroleum Refineryfor Sand IslandOahu, Territory of Ha-waii (Report to Board of Health, Terri-tory of Hawaii)." Public Health Service,Div. of Air Pollution, Cincinnati, Ohio,Dec. 1965, 60 pp.

Termeulen, M. A. "Air Pollution Control byOil Refineries." In: Part I, Proceedingsof International Clean Air Congress, Lon-don, 1966, Paper IV/5, pp. 92-95.

Wilson, J. G. and Miller, D. W. "The Re-moval of Particulate Matter from FluidBed Catalytic Cracking Unit Stack Gases."J. Air Pollution Control Assoc., 17(10) :-682-635, Oct. 1967.

Paint and VarnishBoulde, M. J., Severs, R. K., and Brewer,

G. L. "Test Procedures for Evaluation ofIndustrial Fume Converters (Samplingand Analytical Techniques Reviewedfor)." Air Eng., 8 (2) :20-23, Feb. 1966.

Danielson, J. A. "Air Pollution EngineeringManual." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-

.t

lution Control, Cincinnati, Ohio, PITS-Pub-999-AP-40, 1967, 892 pp.

Morash, N., Krouse, 1%)., and Vosseller, W. P."Removing Solid and Mist Particles fromExhaust Gases." Chem. Eng. Progr., 63-(3) :70-74, March 1967.

Stenburg, R. L. "Control of AtmosphericEmissions from Paint and Varnish Manu-facturing Operations." Public Health Serv-ice, Div. of Air Pollution, Cincinnati, Ohio,Technical Report A58-4, June 1938, 30 pp.

Plastics and ResinsDanielson, J. A. "Air Pollution Engineering

Manual." U.S. Dept. of Health, Education,and Welfare, NIS -Pub-999-AP-40, 1967,892 pp.

First, M. W. "Control of Haze and Odoursfrom Curing of Plastics." In: Part I, Pro-ceedings of International Clean Air Con-gress, London, 1966, Paper VI/11, pp. 188-191.

Kenagy, J. A. "Designing a 'Clean Room' forPlastic Processing." Mod. Plastics, 44 (3) :-98-99, Nov. 1966.

Parker, C. H. "Plastics and Air Pollution."Soc. Plastics Engrs. J., 23 (12) :26-30, Dec.1967.

Other ChemicalsAmmoniaKaylor, F. B. "Air Pollution Abatement Pro-

gram of a Chemical Processing Industry."J. Air Pollution Control Assoc., 15(2): 65-67, Feb. 1965.

FertilizerGrant, II. 0. "Pollution Control in a Phos-

phoric Acid Plant." Chem. Engr. Prog.,(1):53-55, 1964.

Sachsel, G. F., Yocum, J. E., and Retzke, R.A. "Fume Control in a Fertilizer PlantA Case History." J. Air Pollution ControlAssoc., 6 (4) : 214-218, Feb. 1957.

Sauchelli, V. "Chemistry and Technology ofFertilizers." ACS Monograph 198, Rein-hold, 1960.

Miscellaneous Chemicals"Air Pollution Control in Connection with

DDT ProductionInformative Report No.6." J. Air Pollution Control Assoc., 14-(3) :94-95, March 1964.

203

Boulde, M. J., Severs, R. K., and Brewer,G. L. "Test Procedures for Evaluation ofIndustrial Fume Converters (Samplingand Analytical Techniques Reviewedfor)." Air Eng., 8 (2): 29-23, Feb. 1966.

Kaylor, F. B. "Air Pollution Abatement Pro-gram of a Chemical Processing Industry."J. Air Pollution Control Assoc., 15 (2) : 65-67, Feb. 1965.

Massiello, F. "Air Pollution Control at DrewChemical Corporation." In: Proceedingsof Technical Conference, Mid-AtlanticStates Section, Air Pollution Control Asso-ciation, Newark, N.J., 1962, pp. 8-12.

Sandomirsky, A. G., Benforado, D. M.,Grames, L. D., and Pauletta, C. E. "FumeControl in Rubber Processing by Direct-Flame Incineration." J. Air Pollution Con-trol Assoc., 16 (12) : 673-676, Dec. 1966.

Storch, H. C. "Product Losses Cut with aCentrifugal Gas Scrubber." Chem. Engr.Prog., 62(4): 51-54, 1966.

MINERAL PROCESS SOURCES

Bituminous Concrete ManufacturingDanielson, J. A. (c.) "Air Pollution Engi-

neering Manual." U.S. Dept. of Health,Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati, Ohio,PHS-Pub-999-AP-40, 1967, 892 pp.

Gallaer, C. A. "Fine Aggregate Recovery andDust Collection." Roads and Streets, pp.112-117, Oct. 1956.

Hankin, M., Jr. "Is Dust the Stone Industry'sNext Major Problem?" Rock Prod., 70-(4): 80-84, 110, April 1967.

Hayes, S. C., McGrane, N. M., and Perlis, D,B. "Visual Clarity in Kiln DischargeGases." J. Air Pollution Control Assoc.,5 (3): 171-172, 186, Nov. 1955. (Presentedat the Annual Meeting of the Air Pollu-tion Control Association, Detroit, Mich.,May 22-26, 1955, Paper 55-33.)

"Low Dust Despite Heavy Fines, High Pro-duction." Roads and Streets, Aug. 1960.

Lundberg, G. R. "Summary of Dust Collec-tion Systems in Asphalt Plants." (Pre-sented at the 10th Annual Convention ofthe National Bituminous Concrete Asso-ciation, Miami Beach, Fla., Feb. 3, 19e5,14 pp.)

204

McKin, W. A. "Dust Control Check on anUrban Asphalt Plant." Roads and Streets,pp. 173-175, Aug. 1959.

Mitchell, R. D. "Primary Dust Collectors."(Presented at the 10th Annual Conventionof the National Bituminous Concrete As-sociation, Miami Beach, Fla., Feb, 1965,8 pp.)

Mundy, L. W. "Multiple Tube Dust Collec-tors as Applied to Asphalt Plant Oper-ation." (Presented at the 10th AnnualConvention of the National BituminousConcrete Association, Miami Beach, 'la.,Feb. 1965, 4 pp.)

Von Lehmden, D. J., Hangebrauck, R. P.,and Meeker, J. E. "Polynuclear Hydrocar-bon Emissions from Selected IndustrialProcesses." J. Air Pollution Control As-soc., 15 (7) : 306-312, July 1965.

Walter, E. "The Dust Situation at MixingPlants Used in Bituminous Road Construc-tion in Western Germany." Staub (Eng-lish translation), 26(11) :34-40, Nov.1966.

Weatherly, D. "Controlling Dust from RoadBuilding Material Plants." In: Proceed-ings of the Technical Conference, Mid-Atlantic States Section, Air Pollution Con-trol Association, Newark, N.J., 1962, pp.13-18.

Wiemer. "Dust Removal from the WasteGases of Preparation Plants for Bitumi-non.) Road-Building Materia:s." Staub(English translation), 27 (7) :1-22, July1967.

Calcium CarbideSem, M. 0. and Collins, F. C. "Fume Prob

lems in Electric Smelting and Contribu-tions to Their Solution." J. Air PollutionControl Assoc., 5 (3) :157-158, 187, Nov.1955.

Cement

Aleksynowa, K. "Chemical Characteristics ofWaste Cement Dust on Their Value forAgriculture." [Charakterystylca chemiczacementowych pytow odotowuch i ich was-tose dla solnict.} Cement, Wolmo. Gips,11/20 (3): 62-64, 1955.

Kreichelt, T. E., Kemnitz, D. A., and Cuffe,S. T. "Atmospheric Emission from the

Manufacture of Portland Cement." U.S.Dept. of Health, Education, a,ld Welfare,National Center for Air Pollution Control,Cincinnati, Ohio, PHS-Pub-999-AP-17,1967, 47 PP.

Chamberlin, R. L. and Moodie, G. "WhatPrice Industrial Gas Cleaning?" In: PartI, Proceedings of the International CleanAir Congress, London, 1966, Paper No.V/7, pp. 133-135.

"Control at Santee Cement." Southern Eng.,pp. 50-51, March 1967.

Danielson, J. A. "Air Pollution EngineeringManual." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-lution Control, Cincinnati, Ohio, PHS-Pub-999-AP-40, 1967, 892 pp.

Doherty, R. E. "Current Status and FutureProspects-Cement Mill Air PollutionControl." In: Proceedings of 3rd NationalConference on Air Pollution, Washington,D.C., 1966, pp. 242-249.

"Dust Prevention - Cement Industry."[Staubauswurfbegrenzung ZementIndus-tile.] VDI (Verein Deutscher Ingenieure)Kommission Reinhaltung der Luft, Dues-seldorf, VDI 2094, June 1961, 51 pp.

Kohler, W. "Method for the Abatement ofAir Pollution Caused by Cement Plants."[Verfahren zur Verminderung der durchdie Zementindustrie verursachten Luft-verunreinigungen.] In: Part I, Proceed-ings of the International Clean Air Con-gress, London, 1966, Paper IV/12, pp. 114-116.

Rayher, W. and Middleton, J. T. "The Casefor Clean Air." (Federal GovernmentPlans for Nationwide Control.) Mill Fac-tory, 80(4) :41 -56, April 1967.

Tomaider, M. "Dust Collection in the CementIndustry." In: Part I, Proceedings of theClean Air Congress, London, 1966, PaperV/4, pp. 125-128.

Concrete Batch PlantsDanielson, J. A. (ed.) "Air Pollution Engi-

neering Manual." U.S. Dept. of Health.Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati, Ohio,PHS-Pub-999-AP-40, 1967, 892 pp.

Hankin, M., Jr. "Is Dust the Stone Industry's

Next Major Porblem?" Rock Prod., 70-(4) :80-84, 110, April 1967.

Ceramic, Clay and RefractoriesAizenshtadt, B. M. "Extensive Introduction

of Advanced Experience with Dust Ex-traction in the Refractories Industry." Re-fractories, No. 10, pp. 425-426, Oct. 1965.

Luxon, S. G. "Atmospheric Fluoride Contam-ination in the Pottery Industry." Ann. Oc-cupational Hyg. (London), 6 (3) :127-130,July 1963.

Mori, H. "Hanshin Wet Type Dust Collec-tors." Clean Air and Heat Management(Tokyo), 15 (5) : 5-11, May 1966.

Rutman, Z. M. "Purification of Waste Gasesfrom Heat Units in Refractory Factories."Refractories, No. 10, pp. 429-432, Oct.1966.

Glass and FritDanielson, J. A. "Air Pollution Engineering

Manual." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-lution Control, Cincinnati, Ohio, PHS-Pub-999-AP-40, 1967, 892 pp.

Elliott, J. H., Kayne, N., and LeDuc, M. F."Experimental Program for the Controlof Organic Emissions from ProtectiveCoating Operations." Los Angeles CountyAir Pollution Control District, Calif., In-terim Report 7, Jan. 1961, 2311:

GypsumHankin, M., Jr. "Is Dust the Stone Indus-

try's Next Major Problem?" Rock Prod.,70 (4) : 80-84, 110, April 1967.

LimeKaylor, F. B. "Air Pollution Abatement Pro-

gram of a Chemical Processing Industry."J. Air Pollution Control Assoc., 15(2): 65-67, Feb. 1965.

Pottinger, J. F. "The Collection of DifficultMaterials by Electrostatic Precipitation."Australian Chem. Process Eng. (Sidney),10 (2) :17 -23, Feb. 1967.

Pits and QuarriesDanielson, J. A. "Air Pollution Engineering

Manual." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-lution Control, Cincinnati, Ohio, PHS-Pub-999-AP-40, 1967, 892 PP.

205

Davydov, S. A., Aksel'rod, M. B., Mar'Yash,L. R., find Kiimenko, E. I. "Contaminationof the Atmospheric Air with the Waste ofOre-Concentrating Works." [Zagryaznenieatmosfernogo vozdukha vybrosami gorno-obogatitei'nykh kombinatov.] Hyg. andSanit., 29 (2) :115 -118, Feb. 1965.

Hankin, M., Jr. "Is Dust the Stone Indus-try's Next Major Problem?" Rock Prod.,70(4) :80-84, 110, April 1967.

Renninger, F. A. "A Monitoring System forthe Detection and Control of AirborneDust." Dust Tt ,.acs Mag., 3(4) :6.8, Oct.1966.

Schrauf, R. E. "Dust Suppression at St.Mary's Quarry." Mining Minerals Eng.(London), 3(1) :32-33, Jan. 1967.

Walter, E. "Dust Control in Quarrying andRock Processing by Means of Suction De-vices." Staub (English translation), 25-(6): 1-4, June 1965.

OtherGabinova, Zh. L., Vasil'eva, A. A., Sklyar-

skaya, N. Kh., and Manita, M. D. Gigiehai Sanit. (English translation), 28 (6): 65-69, June 1963.

Mori, H. "Hanshin Wet Type Dust Collec-tors." Clean Air and Heat Management(Tokyo), 15(5):5 -11, May 1966.

Agricultural Operations"Wastes in Relation to Agriculture ar. For-

estry." U.S. Dept. of Agriculture, ,scel-laneous Pub. 1065, March 1968, 112 pp.

Paltla.'k, V. K. and Pady, S. M. "Numbersand Viability of Certain Airborne FungusSpores." Mycologia, Vol. 67, pp. 301-310,March-April 1965.

Ilewson, E. W. "Air Pollution by RagweedPollen, 1. Ragweed Pollen as Air Pollu-tion." J. Air Pollution Control Assoc.,17(10): 651-652, Oct. 1967.

Went, F. W. "Formation of Aerosol Particu-lates Derived from Natural Occurring Hy-drocarbons "roduced by Plants:' J. AirPollution Cotitroi Assoc., p. 679, 1967.

Wsnt, F. W. "Blue Hat ." Nnt.ure, 187-(4738): 641-643, 1960.

"Soil Erosion by Wind, and Measures for its

206

Control on Agricultural Lands." Food andAgriculture Organization, 1960.

"Shelterbelt Influence on Great Plains Fields,Environment, and Crops." U.S. ForestService, Production Research Report 62,Oct. 1962.

"How to Control Soil Blowing." U.S. Dept.of Agriculture, Farmers Bulletin 2169,1961.

"Soil Conditions Influence Wind Erosion."U.S. Dept. of Agriculture, Technical Bul-letin 1185, June 1958.

"Suggested Guide for Use of Insecticides isControl Insects Affecting Crops, Livestock,Households, Stored Products, Forests, andForest Products." Agriculture Handbook331, 1968.

Coffee RoastingDanielson, J. A. "Air Pollution Engineering

Manual." U.S. Dept. of Health, Educa-tion, and Welfare, National Center forAir Pollution Control, Cincinnati, Ohio,PHS-Pub-999-AP-40, 1967, 892 pp.

Partee, F. "Air Pollution in the Coffee Roast-ing Industry." U.S. Dept. of Health, Edu-cation, and Welfare, Div. of Air Pollution,Cincinnati, Ohio, PHS-Pub-999-AP-9,1964, 15 pp.

Sullivan, J. L., Kafka, F. L., and Ferrari, L.M. "An Evaluation of Catalytic and DirectFired Afterburners for Coffee and Chic-ory Roasting Odors." J. Air Pollution Con-Ito] Assoc., i5(12):683-586. Dec. 1965.

Cotton Ginning"Airborne Particulate Emissions from Cot-

ton Ginning Operations." U.S. Dept. ofHealth, Education, and Welfare, Div. ofAir Pollution, Cincinnati, Ohio, TechnicalReport A60 -5, 1960, 20 pp.

"Control and Disposal of Cotton GinningWastes." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-lution Control, Cincinnati, Ohio, PHS--Pub-999- AP-I0, 1967, 103 pp.

Paganild. 0. "Control of Cotton Gin N'astein Texas." Preprint. (Presented at the67th Annual Meeting of the Air Pollu-tion Control Association, Houston, Tex.,June 24, 1964, Paper 61 -94.)

"What We Know About Air Pollution Con-trol." Texas Cotton Ginners' Association(Dallas), Special Bulletin 1, March 1965,43 pp.

Feed end GrainBarfield, S. "Harbor Bulk-Loading Grain

Terminals." J. Environ. Health, 28 (2):-151-155, Sept.-Oct. 1965.


"Proceedings of the National Symposium onAir Pollution." Grain and Feed DealersNational Association, Jan. 11-12, 1967,103 pp.

McLouth, M. E. and Paulus, H. J. "Air Pol-lution from the Grain Industry." J. AirPollution Control Assoc., 11(7) :313-317,July 1961.

Fish Meal ProcessingDanielson, J. A. (ed.) "Air Pollution Engi-

neering Manual." U.S. pt. of Health,Education, and Welfare, National Centerfor Air Pollution Control, Cincinnati, 0:ilo,PITS -Pub-999-AP-40, 1967, 892 pp.

Mandell, L. C. "Air Pollution Control for theFish Dehydration Industry." (Presentedat the 54th Annual Meeting of the Air Pol-lution Control Association, New York,June 11-15, 1961.)

OtherDanielson, J. A. "Air Pollution Engineering

Manual." U.S. Dept. of Health, Education,and Welfare, National Center for Air Pol-lution Control, Cincinnati, Ohio, NIS-Pub-999-AP-40, 1967, 892 pp.

Store'', II. L. "Product Losses Cut with aCentrif:tgal Gas Scrubber." Chem. Eng.Prog., 62 (4) : 51-54, April 1966.

207

Ackley, C., 120Adams, R. L, 110, 111,122,124,198Adrian, R. C., 129, 131, 141Aize,ishtadt, B. M., 205A ksel'rod, M. B., 206Albinus, G., 195Aleksynowa, K., 204Allen, G. L., 201Alliot, L., 192Alpiser, F. M., 28Archbold, M. J., 88Archer, A., 198Arkhipov, A. S., 201Arnold, 0. NI., 69Asiander, A., 187Auclair, NI., 192Axtman, W. H., 192

B

Bacon, N. P., 96, 199Bailey, J. 51., 141Bailey, R. E., 202Ballard, W. B., 183Banner, A. P., 141Barber, J. C., 18913arenstein, M., 197Barfield, 8., 207Barker, K., 188, 192, 193Barr, J., 186Hasse, B., 198Batter, W. A., 94Beckman, E. W., 185Beiser, F. R., 199Belyea, H. A., 192Bender, R. J., 194Benforado, 1). 51., 131, 133, 141, 204Bennett, K. W., 29Bears*, B., 194Betty, E., 72Beta, L D., 81Bets, W. H., 81Bigelow, C. 0., 70Billings, C., 61Bins, R. V., 188Black, H. H., 203Black, R..1., 25, 26, 27, 29, 30, 33, 34131xsearitt, A.G., 72Blether, K. J., 192Bloomfield, B. D., 198Blosser, R. 0., 75, 202Boabel, It W., 194, 196Bogus, M. D., 34

AUTHOR INDEX

Bolduc., M. J., 203, 204Borg-wardt, R. H., 106, 183, 188Bovier, R. F., 188Bowerman, F. R., 197Boyer, R. 11., Jr., 34, 194Boyer, R. Q., 202Boystsov, A. N., 201Brandt, A. D., 14, 16, 20, 96, 198Braubacher, H. L., 187Bremser, L. W., 26Brewer, G. L, 20`, 204Brief, R. S., 193Brink, J. A., Jr., 72, 201Brogan, T. R., 13Broman, C., 198Brooke, 61., 81Brooks, A. F'., 64Brooks, R. NI., 81Brown, R. S., 196Browning, J. A., 128, 131Bugher, R. D., 197Bull, W. C., 190Bump, R. L., 194Burckle, J. (1., 30, 183Burggrabe, W. F., 72,Burke, S. A., 188Burson, J. H., 183Burst, J. F., 139Busch, A. W., 81Busey, H., 193Bush, A. F., 185, 194Bye, W. E., 13, 14, 15, 16, 200

201

C

Ca8ero, A. S., 195Cahill, W. J., Jr., 188Calaceto, R. R., 194, 195Caleote, H. F., 128, 131Calonge, A. B., 186Calvert, S., 183Campbell, W. W., 108, 198Caplan, K. J., 121, 125, 134, 135,141Cederhotm, C., 194Challis, J. A., 19!Chamberlin, R. 1.., 198, 205Chase, F. R., 123Chase, R. L, 31, 189, 193, 197Chilton, C. H., 47, 76, 131, 183, 139,

141

Chipman, R. D., 19411. S., 187, 192

Clarke, S. 11., 194

Clement, R. L, 108, 109, 126Collins, F. C., 200, 204Collins, K. E., 188Collins, T. T., Jr., 202Connel, J. R , 203Conners, E., 51

Cooper, R.A.,

81Cooper, H. B. H., 232Cooper, H. B. H.. Jr., 75Cooper, 198C. oper, S. R., 202Copp, W. R., 25Corey, R. C., 19,4Cosby, W. T., 198Cote, W. A., 31, 124Coy, U. W., 96, 200Cuffe, S. T., 15, 96, 123, 189, 204Cuihane, F. R., 111, 113, 118, 119,

120, 121, 123, 125

D

Danielson, J. A., 19,101, 128, 130-131,137, 141, 155, 165,201, 202, 203, 204,

Dave, N. R., 187Davies, E., 198Davis, A. L, 4Davydov, S. A., 206Deaty, J. 0., 196bebrun, G., 189Decker, L. D., 128, 141, 165DeHaas, G. G., 134, 135Dennis, R., 51, UDerndinger, H. 0., 185Dickerson, B. W., 81Doherty, R. E., 18, 205Dorsey, J. A., 30, 183Douglas, I. 11, 198Doyle, 11., 64bragoumis, P., 13Drake, R. NI., Jr., 128, 130Drinker, P., 51Drogin, 1., 15, 22, 124Dubinskaya, F. B., 198Duffy, R., 128Dument.Fillon, J., 199Dunn, C. W., 96Duprey, R. L, 4, 33, 89, 154Durham, J. F., 106Dyer, J., IRS

44, 46, 47, 97,133-134, 138,189, 192, 193,

205, 206, 207

0 r209

E

Ebersole, G. D., 185Eckenfelder, W. W., 178Eckert, E. R. G., 128, 130Eckert, J. S., 62, 77Edwards, V. II., 81Ekberg, G., 187Eldib, i. A., 185Elliott, A. C., 96, 198Elliott, J. II., 205Ellison, W., 198Elson, R. J., 199Engelberg, F., 199Engelbrecht, H. L., 189Engels, I,. II., 192, 199Etoc, P., 192Ettinger, if. J., 193

F

Fagley, W. S., 185Fauth, U., 192FawcII, H. D., 187Felgar, D. N., 183Fenforado, D. M., 165Fernandes, J. H., 189, IA, 195Ferrari, L. M., 206Feuss, J. V., 33Fiala, E., 186Field, M. A., 129, 131Fife, J. A., 34, 194, 196linter E. Z., 192First, M. W., 51, 72, 203Fischer, G. I , 61Flodin, C. R., 189Flood, L. P., 191, 196Flory, F., 187Flower, F. B., 33Foote, E. H., 77Four, R., 192Fournier, M., 189Frame, C. P., 96, 199Frederick, E. R., 105, 113French, R. C., 113, 116, 121, 122Friedlander, S. K., 51Friedrick, H. E., 104, 113, 121, 122,

125Frieling, G., 9, 10, 190Fullerton, R. W., 74, 108, 193, 199

a

Gabinova, Zh. L., 206Gallaer, C. A., 204Gamble, H. L., 131, 141Gambs, G. C., 179Gammelgard, P. N., 202Gardner, J. W., 186Garirell, F. E., 189Gehm, H. W, 20'2George, R. E., 189, 193

210

Gerstle, R. IV., 189Gilbert, N., 50, 51Gill, D. W., 129, 131Glasgow, J. A., 96Glater, R. A., 185Glensy, N., 189Glover, I., 187Godsave, G. A. E., 128, 130, 131Goldberger, W. M., 189Golothan, D. W., 187Golueke, C. G., 28, 197Goode!, P. 11, 133Gosselin, A. E., Jr., 189Gould, R. H., 194Gourdine, M. C., 13Grames, L. D., 131, 141, 165, 204Grant, E. P., 186, 187Grant, H. 0., 203Greaves, N. J., 199Greco, J., 10, 94Greeley, S. A., 194Greenburg, L., 106Greenwell, L. E., 201Gregory, C. A., Jr., 128, 131Griffiths, J. C., 128, 129, 136, 139Griswold, S. S., 189, 192, 193Groebler, If., 187Giuber, C. W., 191Gudmundsen, A., 128, 131Gusman, J., 117

It

Haaland, If. li., 189Haedike, E. W., 196Hagan, J. E., 118Ilagiwara, I., 192Hales, J. N., 15, 96Halitsky, J., 26Hall, M. C., 197Hall, R. M., 68, 183Hamming, W. J., 61Hammond, IV. P., 131, 199Hangebrauck, R. P., 183, 189, 192,

193, 195, 204Rankin, M., Jr., 204, 205, 206Hansen, G. A., 134, 135Hanson, V. W., 69Harding, C. I., 4,197, 202Harrington, R. E., 106, 181, 188Harris, E. R., 199Harris, L. S., 58Harrison, A. F., 202Harrison, R. P., Jr., 123Haskell, C. F., 202Hatch, T., 106Hatchard, R. E., 197Hattori, 1, 192Rau,. L., 197tiusherg, G., 198Hal -ksley, P. G. W., 129, 131Ilaye.2. S. C., 204

Hazzard, N. D., 131, 133Hedlund, F, 187Hein, G. N., 165Heinen, C. M., 186Hemun, W. C. L., 199Henderson, J. J., 4Henschen, Ii. C., 199Herrick, R. A., 106, 107, 124, 199Hersey, H. J., Jr., 109Hess, K., 202Hewson, E. W., 206Hibshman, H. J., 203Hickman, H. L., 27, 34Hickman, H. L., Jr., 25, 26, 27, 29,

30, 33, 34High, M. D., 14, 15, 16, 200Hirao, 0., 186Hoff, 11., 199Hofmann, II., 187Holden, F. R., 96Holland, M., 199Holland, W. J., 192Horton, R. C., 117Hottel, II. C., 127, 128, 131Houghton, H. G., 75Houry, E., 196Howell, G. A., 96Howells, H. E., 187Hoy, D., 199Hughson, R. V., 47Hunigen, E., 186Huntington, R. I,., 77

1

lehle, F., 192Ilgentritt, E. M., 141Ingels, R. M., 19, 128, 13.3, 139, 141Innes, W. B., 128Intelmann, W., 44, 47

Jackson, A., 199Jackson, J., 76Jackson, N. W., 186Jackson, N. 11., 198Jackson, R., 43, 81Jackson, W. E., 186Jacobs, H.1., $1Jacol,s, M. B., 26Jacquinot, P., 189Jamison, R. M., 69Dares, J., 141Jaskulla, N., 186Jens, W., 191Jensen, D. A., 186Johnson, 0. A., SIJohnson, J. E., 199Johnson, K. R., I87Johnson, R. K., 198Jonakin, J., 190Jones, A. H., 123

Joneu, G., 202Judfeon, B. F., 71Juliker, E., 197

K

Kafka, F. L., 206Kaiser, E. R., 26, 29, 194, 196Kapitulskii, V. B., 199Katz, J., 10, 19tKa vlor, F. B., 203, 205

N., 205Keller, J. D., 128, 137Kemnitz, D. A., 15, 96, 123, 204Kenagy, J. A., 203Keng, E. Y. H., 183Ken line, P. A., 15, 96King, D. T., 190Kirkpatrick, S. D., 47, 76, 131, 139,

141Kirov, N. Y., 190, 192, 194Kirsh, J. B., 27Kitani, S., 193Klee, A. J., 25, 26, 27, 29, 30, 33, 34Kleeberg, U., 198Klimenko, E. I., 206Kloepper, D. L., 190Knudson, J. C., 31Kobayashi, K., 127, 128, 131Kogan, L. A., 199Kohler, W., 205Koin, H. W., 196Kopa, R. D., 186Kowalczyk, J. F., 31Kran, W. G., us, 181Kreichelt, T. E., 15, Ho, 96, 123

195, 204Krenz, W. B., 129,141Krikau, F. G., 19f,Kristal, E., 68Krochtittky, 0. W., 197Kropp, E. P., 203Krouse, M., 72, 203Kunii, D., 128, 131Kurtz, P., 194

L

Labardin, A., 192Lafreniere, A. J., 96, 198Lair, J. C., 187Lambe) W. H., 188Landry, J. E., 202Lapple, C. E., 41, 42, 44Laroche, NI., 190Larsen, R. I., 186Larson, 0. P., 81Lawson, S. O., 6Leavitt, J. M., 190Lebec, M. F., 205Lem, G. W., 198Lem.tire, A., 5/00

a

Lemke, E. E., 199Lemon, L. W., 189Lenehan, J. Vt., 195Lepisto, P., 188Licht, W., 104, 116, 122, 125, 126Lieb, H., 196Lieberman C., 28Lloyd, H. B., 96, 199Lock, A. E., 190, 193Lohner, K., 186London, D. E., 203Longwell, D. H., 202Loquerclo, P. A., 27Loszek, W., 199Louden, W. L., 202Ludwig, J. II., 186, 187Lundberg, G. R., 204Luzon, S. G., 205

NI

Nlaatsch, 3., 199MacFarlane, W. A., 188, 192, 193MacKnight, R. J., 31, 195, 11:16, 197Magill, P. L., 96Magnus, M. N., 190Mandell, L. C., 207Manito, M. D., 206Martin, R., 190Mar'Yaah, L. R., 206Masciello, F., 204Massey, 0. D., 76Mauro, F., 192Mawhinney, M. H., 151, 137, 139Mayer, M., 27, 29, 31McCabe, L. C., 26, 201McConnell, 0., 18?McGannon, H. E., 14McGaughey, P. H., 28, 197McGrane, N. M., 204McKee, H. E.,14Kentie, D., 141McKim, W. A., 204ItcLouth, M. E., 207McMahon, W. A., Jr., bMcReynolds, L. A., 185Meeker, J. E., 189, 192, 204Mtinhold, T. F., 202Meissner, H. G., 195Meland, B. R., 194Meurer, S., 187Meyer, W. E., 188Meyers, F. D., 181, 141Middleton, .1. T., 205Miller, D. W., 203Miller, 14. R., 129Miller, P. 13., Jr., 203Mills, .1. L., 131Mitchell, IL 13., 204Mitchell, It T., 96, 199Mitushima, J., 194Monroe, E. S., Jr., 30

Montross, C. F., 64Moodie, G., 189, 198, 205Moody, R. A., 141Moore, J. F., 6Moore, W. W., 8, 9, 190Morash, N., 72, 203Morgan, B. B., 129, 131Morgenthaler, A. C., 193Mori, H., 205, 206Morris, J. P., 186gortstedt, S. E., 187Moschella, R., 61, 72Moser, E., 197Moss, W. D., 193Mowbray, K. D., 196Muhich, A. T., 25, 26, 2;,,19, 30, 33,

34Mukai, M., 191Mukhlenov, I. P., 76Muller, H., 186Mundy, L. W., 204Murphy, R. P., 200

N

Namy, G., 199Netzley, A. B., 196Neuhaus, H., 200Nishiwaki, N., 127, 128, 131Nissen, W. E., 188, 187Noland, R., 128Norman, G. R., 6Northcraft, M., 196

0

Ochs, H. J., 200O'Conner, C., 29, 195Oiestad, A., 193Olsen, J. W., 121, 199O'Mara, R. F., 98Orning, A. A., 127, 131, 189Orr, C., 183Ott, R. R. 197Owens, V. P., 202Otolins, 0., 4

P

Pady, S. NI., 206Paganini, 0., 206Pallinger, J., 89, 200Papovich, M., 196Parker, A. S., 128,181Parker, C. H., 203Parker, C. M., 200Parte., P., 206Pascual, S. J., 195Pathak, V. K., 206Paulette, C. E., 131, 133, 141, 165,

204Paulus, H. J., 207

211

Pearse, D. J., 200Penney, G. W., 183Perlis, D. B., 204Perry, J. IL, 50Perry, R. H., 47, 76, 131, 139,Pesterfield, C. H., 193Peterson, D. G., 189Pieratti, A., 195Plumley, A. L., 190Pollock, W. A., 9, 10, 190Poppelc, E. W., 13Pottinger, J. F., 190, 200, 205Powers, E. D., 76Pozin, M. E., 76Prindle, R. A., 25Pring, R. T., 122Punch, G., 96, 200Ptirsglove, J., Jr., 190

Quack, R., 190

S

Sableski, J. J., 31Sableski, J. .1., Jr., 196

141 Sachsel, G. F., 203Saha, I. S., 202Sandomirsky, A. G., 131, 141, 165,

204Sarto, J. 0., 185Sauchelli, V., 203Scheldhammer, A., 76Schenk, R., 187Schneider, R. L., 200Schnitt, 11., 197Schrauf, R. E., 206Schueller, H. M., 25Schueneman, J. J., 14, 16, 13, 191,

193, 200Schuldt, A. F., 200Schute, W., 192Schwartz, A. J., 183, 193Schwartz, C. II., 189Schwarz, K., 191Schwendiman, L. C., 194Scope, S., 186Sedeler, C. G., 13Seely, R..1., 27, 197Sem, M. 0., 200, 204Semrau, K. T., 52, 164Senecal, J. E., 17Sensenbaugh, J. D., 189Severe, R. K., 203Shaffer, N. R., 19Shale, C. C., 183Sheehy, J. P., 4Sheppard, S. V., 62Sherman, R. .1., 128Shutko, F. W., 190Sibel, J. T., 28Silverman, L., 51, 58, 72, 102, 105,

194Simon H., 105, 106, 107, 110, 111,

117, 118, 121, 125, 126

Rabel, G., 200Radford, W. IL, 75Radier, H. H., 135Rammler, E., 44, 47Eamsdell, R. C., Jr., 88Rao, T. V. L, 188Rather, J. B., Jr., 6Rauscher, J. A., 72, 201Ray, F. A., 124, 199Rayher, W., 205Reed, L. E., 188Reed, R. J., 141Reese, J. T., 10, 94Rehm, F. R., 194Reichenbach, G. S., Jr., 51Reminiczky, K., 193Henninger, F. A., 206Retake, R. A., 203Rice, 0. R., 70Richards, a, 185Rickle, R. N., 81Ridgway, S. L., 187Ridker, R. G., 157Riley, B. T., 29, 183Rispler, L, 187, 188Robinson, M., 183Rodebush, W. H., 104Rogers, T. F., 190Rogu, C. A., 195Rose, A. H., 187, 188Rose, A. H., Jr., 104, 123, 193, 203Rosin, P., 44Ross, C. R., 187, 188R01,44110, A. T., 51Rothman, S. C., 197Ruff, R. J., 135Russell, R. R., 197Rutman, Z. M., 205

212

Simonsen, R. N., 203Simpson, H. C., 127, 128, 131Sklyarskaya, N. K., 206Smith, D. F., 128, 131Smith, J. H., 183, 200Smith, R. I., 183Smith, S., 196Smith, W. M., 96, 200Smith, W. S., 191, 193Snowball, A. F., 201Sornmerlad, R. E., 9. 121, 122Sordelli, D., 201, 202Sorg, T. J., 27Spaite, P. W., 104, 106, 118, 123,

121, 181, 188Spauling, D. 13., 127. 128, 131Spenceley, G. D., 200Spencer, J. D., 191Spieekerman, J. A., 139

Springer, K. J., 188Stahenow, G., 195Stairmand, C. J., 39, 54, 57, 68Starkman E. S., 187Stastny, E. P., 202Stenburg, R. L., 195, 196, 203Stephan, D. G., 39, 104, 106, 107,

116, 118, 119, 123, 124Stephenson, J. W., 195Sterling, M., 17, 195Stern, A. 50Stickel, R. 202Stoker, R. L., 50Stopperka, K., 202Storch, H L., 76, 204, 207Storch, O., 200Strauss, W., 41, 44, 63, 105Strove, W., 191Stuart, H. IL, 202Sullivan, J. L., 141, 200, 206Swinehart, G., 29, 195Syrovatka, Z., 195

Taheri, 183Talens, P. 0., 196Tarat, E. Y., 76Tate, R. W., 77Tebbens, B. D., 191Teller, A. J., 52, 63, 62, 198Ter meulen, M. A., 203Theodore, L., 183Thieme, W., 191Thom, G. W., 200Thomas, G., 199Thomas, J. F., 191Thomas, N. J., 126Thornburg, G. E., 196Thompson, C. W., 128, 129Thring, M. W., 128, 131, 137, 141Tigges, A. J., 188Todd, W. F., 118Tolciss, J., 196Tomaides, M., 205Tomany, J. P., 9, to, 190Topper, 1., 128Toyama, T., 201, 202Treat, R., 186Trenck, H. M., 191Tribus, M., 186Trinks, W., 128, 131, 137,139Truitt, S. M., 141Tulcinsky, S., 200Tyler T. I, 81, 131

1.1

Underwool, G., 200

V

Vandaveer, F. E, 133

Van Doornum, G. A. W., 192Varchayski, I. L., 187Vasil'eva, A. A., 206Vasselter, W. P., 72Vaughn, R. It, 25, 26, 27, 29, 30,

:33

Venezia, R., 4Verrochi, W. A., 188Vet tebrodt, W., 200Vickerson, G. L., 196Viets, F. H., 201Voelker, E. M., 31, 196Vogely, W. A., 197Voinov, A. N., 192Volheim, G., 129, 131, 141VonBergen, .1. M., 16VonLehmden, D. J., 189, 192, 195,

204Vosselter, W. P., 203

Wagner, K., 198Waitkus, J., 131, 141Walker, A. B., 58, 183, 195, 202Wallach, A., 141Wallin, S. C., 188Walsh, G. W., 106, 107Walter, E., 204, 206

Walters, D. F., 196Tanta, R. C., 203Waple E. R., 81Warner. D. L., 81Wasser, J. H., 183, 1931Vatson, K. S., 192Weatherley, D., 204Weaver, L., 197Weber, E. J., 128, 129Weber, E. V., 136, 139Wechselblatt, P. M., 198Wegman, L. S., 195Weil, S. A., 135, 136Wene, A. W., 197Went, F. W., 206Wentink, G., 193Weston, R. F., 27, 197Wettig, K., 186Weyers, W., 192Wheeler, D. H., 200Whiddon, 0. D., 190White, H. J., 81, 88, 91Whitsam, K. B., 199Wiemer, P., 204Wiley, J. S., 197Wilhoyte, H. J., 129Willett, H. P., 201, 202Williams, C. E., 106Williams, D. L T., 200

Williams, G. C., 127, 128, 131Williams, R. E., 196Williamson, J. E., 195, 196, 197Williamson, J. T., 31Wilson, E. L., 38, :39, 40, 52, 96,

155

Wilson, J. G., 203Wood, C., 188Woodland, R. G., 197Woodruff, P. H., 197Wright, C. H., 190

Y

Yagi, S., 128, 131Yamaki, N., 187Yocum, J. E., 203Yokomiyo, K., 201York, 0. II., 73Young, P. A., 96, 199

zZaitaev, M. M., 1987anon, D., 201, 202Zavodny, S., 196Zender, W., 186Zeschmann, E. G., 186Zhevnovat)1, A. N., 81Zhigalina, 1. S., 198

213

A

Acid manufacturing. (See specificacid.)

Aerosoldefinition of, 2

Afterburnersdiscussion of, 126-139typical applications of, 139, 141

Aircraftparticulate emission sources, 3

Apartment house incineratorsgeneral cliscussion of, 32-33

Asphalt batch plantsemissions from, 18-19control device used in, 18-19

Automobile disposal, 28-29Automobiles

emission sources, 3, 4-5Automotive emission control sys-

tems, 4-5B

Baffles (impingement), 73-75Baghouse filters. (Ste Fabric Mrs.

tion.)Blast furnaces

control devices used in, 14-16

C

Carbon black manufacturingemissions from, 22control devices used in, 22

Cement manufacturingemissions from, 17-18, 123control devices used in, 96, 123

Centrifugal collectors (dry)discussion of, 9, 44-50applications of, 60

Cleaning of fabric filters, 118-121Coffee processing

emissions from, 23control devices used in, 23

Coke manufacturingemissions from, 19-20control devices used in, 19-20

Collection efficiency of controlequipment, 41, 46-47, 52, 94, 155

Combustion sources, 3Commercial and industrial inciner-

liter.description of, SO-32

214

SUBJECT INDEX

Federal assistance for solid wasteprograms, 34

Compostingdescription of, 28

Contaminant. (See Pollutant.)Costs of control equipment

general, 155-182maintenance and operating, 162gravitational collectors, 163centrifugal collectors (dry), 163wet collectors, 163electrostatic precipitators, 164filtration, 164-165afterburne.s, 165

Cotton ginningemissions from, 23control methods in, 23

Cyclone collectors. (Ste Centrifu-gal collectors.)

D

Demolition of masonryemissions from, 24

Design of combustion systems, 4-6Diesel-powered vehicles

emissions of, 5-6Disposal of collected particulate

material, 176-182Domestic incinerators, 30Dust

definition of, 2

Eiectrestatic precipitators (highvoltage)

uiscussion of, 10, 81-96applications of, 40-41, 94

Electrostatic precipitators (lowvoltage)

dismission of, 10, 96-102applications of, 101

Emission factorsgeneral, 150-154coal combustion, 153process industries, 154

Energy conservation, 12-13Engery source fuels, 8Energy substitution, 10-12

Fabric filtrationdiscussion of, 10, 102-126application of, 104, 123-125

Fabrics (filter), 110, 113-118Filters (irrigated wet), 70-72Flue fed incinerators. (Ste Apart-

ment house incinerators.)Fly ash

definition of, 2Fog

definition of, 2Foundries (gray iron)

emissions from, 6-17, 123control devices used in, 16-17,

123Fume

definition of, 2

aGas cleaning devices, 9-10, 38-39Gasolinefueled vehicles

emissions of, 3, 44Glass manufacturing

emissions from, 22process description of, 22

Gypsum processingemissions from, 22-23control devices used in, 22-23

1

Incineration of solid wastes, 29-33incinerator control equipment

efficiency of, 29-3.3Incinerators. (Ste specific type.)Industrial sources of particulates, 3Iron and steel mills

emissions from, 14-16control devices used in, 14-16

K

Kraft pulp millsemissions from, 18control devices used in, 18, 96

LLandfills

general description of, 26-27

M

Mistdefinition of, 2

Mist eliminators, 72-73Motor vehicles

emission sources, 3, 4-fMunicipal incinerators

general discussion of, 33-34control devices for, 33-34

0

Open burning, 24, 29-30Open top incinerators, 30

Particledefinition of, 2

Particulate matterdefinition of, 2

Petroleum refineriesemissions from, 17control devices used in, 17

Phosphoric acid manufacturingemissions from, 19control device used in, 19

Pollutantdefinition of, 2

R

Research (current) in controlmethods, 183

Road dustcontrol of, 24

Road gradingdust generation from, 24

SSandblasting

control of particulates from, 24Scrubbers

centrifugal spray, 54-57disintegrator, 69-70impingement plate, f7 -b8inline wet, 70

mechanically induced spray, 64-69packed bed, 60-64peloormance of, 9-10, 50-70self induced spray, 64-65venturi, 58-60

Settling chambersdiscussion of, 9, 39-43applications of, 42-43

Shutdown of emission sources, 14Sintering plants

control devices used in, 14Smelters

emissions from, 14, 20-21Smoke

definition of, 2

0. ElINVECT FIANTIVO MrK[; IS,E, -34/.%1 In,

Soap and detergent manufacturingemissions from, 21control devices used in, 21

Solid wastedefinition of, 25-26quantity produced, 25-26

Sootdefinition of, 2

Source relocation, 10Sources of particulate matter, 2-3Spray chambers, 52-54Spray nozzles

types of, 77-80Sprays

definitions of, 2Spray towers, 64Stationary combustion sources, 6-8Steel furnaces

control devices used in, 16emissions from, 16

Sulfuric acid manufacturingemissions from, 19control devices used in, 19, 9b

W

Wet collectorsdiscussion of, 5041

Wood waste incineratorsemissions from, 30

216

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