Hazard and Operability Study Recontek Waste Recycling Facility Newman, Illinois

Prepared for: Recontek. Inc.

for Submiffal to: Illinois Environmental Protection Agency Office of Chemical Safety

April 1990

e ERC 3 Env i roil me 11 t a I and Energy Services Co.

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I Hazard and Operability Study Recontek Waste Recycling Facility Newman, Illinois

I Prepared for: Recontek, Inc.

for Submittal to: Illinois Environmental Protection Agency Office of Chemical Safety 2200 Churchill Rd. P.O. Box 19276 Springfield, Illinois 62794-9276

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Prepared by : ERC Environmental and Energy Services Co. 5510 Morehouse Drive Son Diego, California 92 12 1- 1709

) April 1990

TAIlLl< OF CONTENTS

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NllMDER 3- 1 3-2a 3-2b

INTRODUCTION

HAZARD AND OPERABILITY STUDY APPROACH Hazard and Operability Study Procedure Probability and Seventy of Offsite Consequences

PROCESS REVIEW Receiving and Analyzing Wastes Processing

Spill Control Process Control Philosophy Reactor Systems Ventilation System Mixed Acid Wastes (System 2) Zinc Sludge Wastes (System 5A) Copper-Nickel Sludge Wastes (System 5B) Iron Removal (System 9) Copper Electrowinning (System 7) Zinc Electrowinning (System 8) Nickel Sulfate and Sodium Sulfate Crystallization (System 12) Chrome Removal (System 10)

CONCLUSIONS AND RECOMMENDATIONS

LIST OF FIGURES

TLnE Recontek Building Layout Reactor System with Vaporization Reactor System without Vaporizalion

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2-1 2-2 2-5

3-1 3-1 3-3 3-4 3-4 3-4 3-5 3-7

3- 10 3-1 1 3-12 3-12 3-13

3-14 3-15

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!%X 3-2 3-6 3-6

TABLE OF CONTENTS (Conlinucd)

LIST OF TABLES

m u 2- 1 HazOp Study Participants 2-2 HazOp Study Information

LIST OF APPENDICES )

L.E” m A Process Descriptions B Process Flow Diagram C Piping and Instrumentation Diagrams D Building Layouts

EBGE. 2-3 2-6

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SECTION 1

INTRODUCTION

Recontek Corporation is currently designing and constructing a waste recycling facility in Newman, Illinois. The facility will accept wastes generated from metal finishing, plating, and electronics operations from the region, and will process these wastes into marketable products. The following wastes will be accepted for processing at the Newman facility:

- Mixed acid wastes (including sulfuric acid, hydrochloric acid, and nitric acid), shipped in tank trucks.

Wet sludges (40 to 60% moisture) containing metals, shipped in bulk containers and dump trucks.

Dry sludges (20 to 30% moisture) containing metals, shipped in drums.

The metals contained in the wastes received at the facility will include copper, nickel, zinc, iron, chromium, cadmium. tin, lead, and precious metals (e.g., gold and silver). The facility will produce the following products:

copper cathodes zinc powder nickel sulfate iron oxide leadcadmium concentrate tin-precious metal concentrate chromium phosphate scdium sulfate hydrochloric acid

This report presents the results of a hazard and operability study for the facility. This study focuses on identifying potential releases of hazardous materials that could impact the surrounding community. Although this study considers spills of liquid and solid hazardous materials, the emphasis is on releases of vapor releases. which would present the most significant impacrs.

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The study is based on i’nformation provided by Recontek, including process flow diagrams, piping and instrumentation diagrams, process descriptions, building layouts, and equipment lists. A major pan of the study was a meeting with representatives of Recontek, Pipeline Systems Inc (detailed engineering contractor), and ERC Environmental and Energy Services Company (HazOp study consultant).

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SECTION 2 IIAZARD AND OPERABILITY STUDY APPROACH

Hazards and Operability (Ha) Studies are used by engineers and operators of chemical processing plants for a wide variety of reasons, These reasons vary from identifying potential safety hazards to evaluating potential operational problems to characterizing potential consequences to the surrounding communities in the event of a release of a hazardous material. HazOp studies have been conducted throughout the life of a processing plant, beginning with conceptual design, through detailed design and construction, and during the operation of a plant. A number of different procedures have been developed to identify potential hazard and operability problems within a plant. The effectiveness of each of these procedures depends on the goal of the HazOp study and on the stage of the project life.

The Recontek Waste Recycling Facility at Newman, Illinois is currently in the detailed design and construction phase of the proje The objective of this HazOp study is to identify scenarios that would lead to releases of hazardous materials to the surrounding community.

This study has been conducted using a combination of two hazard evaluation procedures that are effective in identifying scenarios that could lead to accidental releases of hazardous materials. These two procedures are the cause-consequence analysis and the hazard and operubifiry srudy. These procedures are described in detail in Guidelines for Hazard Evaluation Procedum , prepared in 1985 by Battelle Columbus Division for the Center for Chemical Process Safety of the American Institute of Chemical Engineers.

The purpose of the cause-consequence analysis is to identify the causes of potential accidents and evaluate the consequences of these accidents. The general procedure for conducting a cause-consequence analysis consists of the six steps:

1. Select an event to be evaluated.

2. Identify the safety functions that influence the course of an accident resulting from the event.

3. Develop the accident paths resulting from [he event.

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4. Develop the event and the safety function failure event to determine basic causes.

5 . Determine the most probable accident sequences.

6. Rank or evaluate the results of the analysis.

The cause-consequence analysis focuses on the causes of accidents and the resulting consequences. The cause-consequence analysis also has the advantage over some other hazard evaluation procedures in that it can focus on hazardous material releases resulting from outside events, as well as releases resulting from process design or operational problems.

The general purpose of the hazards and operability (HazOp) study is to identify potential hazards and operational problems within a plant. The H a p study focuses on how a plant will respond to deviations from normal operation. As such, a HazOp study can be a very comprehensive evaluation of many issues dealing with the design and operation of a plant. With respect to the environmental and safety risks, this HazOp study specifically focuses on hazardous material releases resulting from misoperation or equipment failures within the process.

The HazOp is conducted by following that path of materials through the plant, using process flow diagrams (PFDs) and piping and instrumentation diagrams (P&IDs). The HazOp focuses on "study nodes" throughout the process. At these study nodes, the process operating and design parameters (such as flow rate, temperature, pressure, composition, etc.) are defined. The potential for deviations in these parameters to occur and the resulting consequences are studied and evaluated.

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HAZARD AND OPERABILITY STUDY PROCEDURE

The HazOp study was conducted as a series of meetings that took place at Recontek's engineering offices in San Diego, California. on February 22 and 23. Pmicipating in these meetings were employees of Recontek, Pipeline Systems Incorporated (PSI). and ERC Environmental and Energy Services Company (ERCE). The participants and their roles in the study are listed in Table 2-1. The Reconlek employees included both facility

Tablc 2-1

I-IAZOP STUDY PARTICIPANTS

Person Affiliation Tide HazOp Role ~

Harold Rajcevic

Douglas Basch

waam C0tte.P

Stephen Broz * David Freeland

Jay Chapman

Michael Turney

John Radcliffe

TeddDowd

Rccontek Technical Director

Recontek Chief Engineer

Recontek Construction Manager

Recontek Newman Plant Manager

PSI Business Development Manager

PSI Engineering Manager

PSI PipinglMechanical Design Supervisor

PSI Senior Instrumentation Engineer

PSI Project Manager

Process Specialist

Facility Specialist

Facility Specialist

Facility Specialist

Conml Specialist

Design Engineering Specialist

PipinglEquipment Specialist

Control Specialist

Facility Specialist

Gregory Lorton ERCE Chemical Engineering Manager HazOp Study Leader

Pankaj Garg ERCE Chemical Engineer H e Specialist

* denotes part-time pardcipant

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engineering. design, and'construction personnel. and designated operations personnel. Recontek is performing the process design of the facility. PSI is assisting Recontek in detailed engineering design. ERCE is responsible for conducting this HazOp study.

A follow-up meeting was held on February 27 to discuss several additional items and unresolved points. Participating in this meeting were Gregory Lorton and Pankaj Garg of ERCE and Harold Rajcevic and Douglas Basch of Recontek.

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The meetings were conducted with a number of different objectives:

1. Identify sources of potential releases of hazardous materials. Identify potential events that could lead to releases.

2. Based on the sources and events described above. determine how the plant systems and operators would prevent or mitigate the releases.

3. Identify plant operability problems that could disrupt n o d operations.

4. Discuss plant process control philosophy and responses to plant upsets and normal variations in operating conditions.

5 . Identify database requirements for all aspects of facility operations.

The meeting was conducted by sequentially discussing all steps that will take place at the Newman facility in order to conduct business and process the feed materials. In order, these steps included the following:

1. Receipt and acceptance of an application from a client to process its wastes.

2. Analysis of a characteristic sample of the client's waste.

3. Shipment of the waste from the client to Recontek.

4. Arrival of the waste at Recontek.

5. Analysis of the samples of the waste.

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6 . Unloading and storage of the waste within the facility.

7. Processing of the waste in the facility.

8. Analysis of in-process streams.

9. Sale of recovered materials and disposal of by-products.

The discussion of these steps was repeated for each type of waste received and processed by the facility (e.g.. dry zinc and non-zinc sludges, wet zinc and non-zinc sludges, and mixed acid wastes). Table 2-2 lists the information that was used in the study. A copy of this information is included in the Appendices.

PROBABILITY AND SEVERITY O F OFFSITE CONSEQUENCES ,

In evaluating scenarios that could result in the release of hazardous materials. the probability that the scenario could occur and the seventy of the release are considered. The method for assessing the probability and severity is presented in Techn ical Guidance for Hazards A n w . @PA 1987). The definition for the severity is given below:

SEVERITY OF CONSEQUENCE

Rank Examples of Severity

Low Chemical is expected to move into the surrounding environment in neglible concenmtions. Injuries expected only for exposure over extended periods OT when individual pcrsonal hwllh conditims create complications.

Chemical is expected to move into the surrounding environment in concentrations sulficicnt lo cause serious injuries and/or deaths unless prompt and effective corrective action is lakcn. Death and/or injuries expected only for exposure over extended periods or when individual personal health conditions create complications.

Chemical is expected to move into the surrounding environment in conccnmtions sulficicnt to cause serious injuries and/or deaths upon exposure. Large numbers of p p l e cxpcctcd to bc affected

Medium

High

Source: &hnical Guidance To r Hwads Analvsis, EPA 1987.

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Table 2-2 HAZOP STUDY INFORMATION

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Process Descriptions System 2 Mixd Acid Wasm System 5-A Zinc Sludge Wastes System 5-B Cop-Nickel Sludge Wastes System 7 Copper Electrowinning System 8 Zinc Electrowinning System 12 System 9 Iron Removal System 10 Chmne Removal

Nickel Sulfate - Sodium Sulfate Crystallization

Process Flow "lxt

DNP-038 DNPMO DNP-023 DNP-024 DNP-025 DNP-026 DNP-030 DNP-021 DNP-022

1 DW-032 DNP-033 DNp-034 DNP-035 DNP-028 DNP-027 DNP-031

Diagrams xi& proccSs Block Flow Diagram Mixed Acid Waste :System 2 Zinc Hydmxide Sludge - System 5A Metal Hydroxide Sludge - System 5B Copper Electrowinning - System 7 Zinc Electrowinning - System 8 . NiSO4 & Na2SO4 Crystallizers - System 12

Chrome Removal - System 10 V i i n Chemical Storage - System 14 Water - System 15 ; Cooling Water - System

H.V.A.C. - System 25

lron Removal - S y h 9: ' , : :'. , ,

s m system u::: ' . , : , , .

Naaval Gas -,System 24 , .

Scrubber - System 26 * ; .. .

. . .

Revision A G

. . G H E D C

, . . D C D

. D C

, , . , ' C , . . . ' . .

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' 1 C .~

) Piping and Instrumentation Diagrams (P&IDs) "

2MM-101 UnbadingArea 2%-M-102 256-M-103 2MM-104 2MM-105 2%-M-106 Metal Hydroxide Sludge Reactors 2%-M-107 Metal Hydroxide Sludge Tanks 2%-M-108 Copper Electrowinning Cell House 2%-M-109 Copper Electrowinning Cell House 2%-M-110 Zinc Elactrowinning Cell House B 256-M-111 cryslallizer 2%-M-112 Crystall ' i 256-M-113 VuginChemical Storage 2MM-114 Plant wale€ 2MM-115 Mixed Acid Waste 256-M-116 Mixed Acid Waste 256-M-117 Area andUnloadingSump 256-M-118 256-M-126 Scrubber

Metal Hydroxide Sludge Receiving and Digesting Metal Hydroxide Sludge Nm and Cementation Metal Hydroxide Sludge Fdlcrs and Cementation Metal Hydroxide Sludge Reactors '

Zinc Hydroxide Pre-Digester and Flux

Uuilding Layouts and Plot Plans "i?z m €mP- IO N P - I I Scrubbcr Ducting Arrangcmcnc

MAC-up Air lor Scrubber Exhaust

Revision 0 0 0 0 0 0 0 0 0 0 0 0 0 0

A A

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Similarly, the likelihood that a scenario will occur is defined below:

LIKELIHOOD OF OCCURRENCE

Rank Examples of Likcliood

Low Probability of occurrence considered unlikely during the expected lifetime of the facility assuming normal operation and maintenance.

probability of o c c m c e considered possible during the expected lifetime of the facility.

Robability of occurrence considered sufficiently high to assume event will occur at least once during the expected lifetime of the facility.

Medium

High

Source: pdukd Gu' idance Gx,&zards A n&&. EPA 1987.

Typically, a low likelihood of occurrence is considered to be once in 10,OOO years or less, at a particular facility. A medium likelihood event is one that is not likely to occur during the life of the plant but is considered likely to occur at least once in 10,ooO years.

The intent of the EPA's guidance is that a detailed offsite consequence analysis should be performed only for those scenarios that have a medium or high likelihood of occurrence and a medium or high severity of consequence. Events that are considered very unlikely or extremely unlikely ("low" likelihood, as defined above) do not warrant a detailed offsite consequence analysis. Similarly, events with low severity of consequences do not warrant a detailed offsite consequence analysis.

SECTION 3 PROCESS REVIEW

This section is a description of the process with a focus on potential releases of hazardous materials. A more detailed process description that discusses the chemisay of each process system is presented in Appendix A. Process flow diagrams are presented in Appendix B. Piping and instrumentation diagrams are presented in Appendix C. Building layouts are presented in Appendix D.

RECEIVING AND ANALYZING WASTES

Recontek will accept wastes only from selected customers that it believes will provide consistent materials in terms of quantity and composition. Before Recontek receives waste from a customer, Recontek will have a contract in place to receive and treat the customer's wastes. Part of Recontek's terms of the contract will be an analysis that characterizes the composition of the waste, described in acceptable ranges. The contract will list compounds that are prohibited from the wastesi such as cyanide solutions or soivents. Similarly, the conmct will specify that only transporters acceptable to Recontek may deliver the wastes to the Recontek facility. This is the first step taken by Recontek to ensure that incompatible chemicals do not enter the facility.

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Each mckload of waste that arrives at the facility will have been scheduled in advance to allow for efficient and smooth operation of the facility's processes. Once a rmckload of waste arrives at the plant, samples will be collected and analyses performed to ensure that the waste agrees with manifest description, contains no chemicals that will disrupt the process or create an operational hazard (such as cyanide solutions). and establish information necessary for efficient processing of the wastes.

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I Prior to acceptance of the waste, Recontek will ensure that the manifest information is correct, and that there is no evidence of leakage or other problems with the uuck. Wastes that do not meet Recontek's requirements will be returned to the generator.

Wastes will be received at the facility by tanker trucks of liquid acid wastes, bulk containers or dump trucks with wet sludges, or drums of dry sludges. Figure 3-1 is a sketch of the facility layout that shows the receiving areas for bulk shipments and drums. With bulk shipments. the trucks are moved into the unloading bays before sampling and analysis are

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done. The unloading area is inside the building and is connected to the main building ventilation system. All of the air from the building passes through caustic scrubbers to remove acid vapor from the air before the air is vented to the atmosphere.

The truck unloading area is paved with concrete and slopes downward into the building. Spills in the unloading area will flow into sumps that can be pumped into the raw material tanks. The sumps are designed to hold more than the entire contents of the largest truck to be allowed into the facility. The floor and walls of the unloading area are sealed with an epoxy coating that is resistant to acidic and alkalime solutions. Spills will be cleaned up and processed in the facility. As such, there is virtually no possibility that soil or groundwater contamination will occur from a spill occurring in the facility. At ambient temperatures, there is no significant hazard associated with vaporization of volatile compounds from any material that Recontek will receive.

Bulk truckloads of wet sludge are dumped into sludge tanks at the end of the unloading bays, where they are slumed. Sludges containing zinc are s l b i e d with an alkaline solution. Sludges without zinc are slurried with an acid solution. Bulk shipments of mixed acid wastes are pumped directly from the tank trucks into acid waste storage tanks

located in the process area.

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Drummed wastes will consist of dried sludges either with or without zinc. These drums will be unloaded from the truck onto the dock. Fork lifts will carry the drums on pallets into the receiving area for temporary storage. Drums will be processed according to the schedule that optimizes the processing of all materials received. To begin processing. the drums will be emptied into a hopper and slumed with an alkaline or acidic solution, depending on whether or not the sludge contains zinc.

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PROCESSING I

The Recontek facility has eight different waste processing systems, which are listed below:

System 2 Mixed Acid Wastes System SA Zinc Sludge Wastes System 5B Copper-Nickel Sludge Wastes System I Copper Electrowinning System 8 Zinc Electrowinning

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System 12

System 9 Iron Removal System 10 Chrome Removal

Nickel Sulfate and Sodium Sulfate Crystallization

In addition to these waste processing systems are auxiliary systems for virgin chemical storage (System 14); water (System 15); cooling water (System 20); steam (System 23); natural gas (System 24); heating. ventilation, and air conditjoning (System 25). and the scrubbers (System 26). Of these auxiliary systems, only the scrubbers play a potentially significant role in the control of hazardous materials.

Spill Control

All of the process areas within the facility are located in bermed containment areas. The berm walls are high enough to contain 120% of the contents of all of the tanks and reactors combined. The berm walls and the floor are made of high strength concrete and are sealed with an epoxy coating that is resistant to acidic and alkaline solutions. In the event of a spill resulting from a tank or pipe leak, the spilled material will be collected to the maximum extent possible for reprocessing. The floors will then be washed down with water, which will also be used in the processes. There is virtually no chance that soil or groundwater contamination will occur resulting from a spill in the building.

Process Control Philosophy

The process control philosophy for the Recontek facility was designed with the prevention and mitigation of hazardous material releases as a primary objective. This objective is important both from the worker safety perspective and a public health and safety perspective. The control system is designed to "fail safe". In essence, should the plant lose electric power, all electric equipment will shut down and valves will either open or close so as to prevent the release of materials. The control instrumentation is illustrated on the piping and instrumentation diagrams in Appendix C.

Reactor Systems

The Recontek facility uses a number of common processing operations and equipment configurations. In general, the method of operation and control of these systems of equipment is the same. Figure 3-2a is a simplified process flowsketch that shows a reactor

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system that is used throughbut the plant for processes involving vaporization. The reactor is jacketed with connections for both steam and cooling water. These glass-lined reactors are built by Pfaudler and are equipped with agitators.

The reactors operate at a slight negative pressure. Vapor generated during a reaction or during evaporation pass upward through the packed reflux column and through the water- cooled condenser. Condensed vapor is collected in the receiver and pumped to further processing steps or to product storage. Uncondensed vapor leaving the receiver goes first to the vacuum venturi and then to the main scrubbers. Sodium hydroxide (caustic) solutions circulate through both the venturis and the main scrubbers. Acid gases (such as hydrogen chloride) and acid mists from the reactors are removed in the receiver or in the scrubbers.

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Figure 3-2b illustrates a reactor system in which significant vaporization does not take place. This system does not include a packed reflux column, condenser, or receiver. The reactor vent, which handles working and breathing losses, is connected directly to the main scrubbers.

All reactors and process tanks are equipped with two level devices to prevent overfilling. The ftrst high level device activates an alarm to alert the operator that a high liquid level exists in the vessel. If the operator neglects this alarm or if the device fails, a second high level device automatically closes the valves on the lines into the vessel. Pumping into the vessel cannot be resumed until the liquid level is lowered, either by pumping out or draining the vessel. In addition to these control devices, the production schedule will account for vessel volumes and waste quantities. to avoid accidental overfilling of the vessels. The operator will know how much material is in the vessel before he starts pumping and he will know how much material he is pumping into the vessel. This represents an additional safeguard to prevent overfilling.

Ventilation System

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In addition to the process vents, all of the main building air is collected and drawn through the main scrubbers. The main scrubbers are illustrated on process flow diagram DNP-031 in Appendix B. Caustic solution (sodium hydroxide) circulates througt, the scrubber to remove acid gases and mists. The quantity of sodium hydroxide in the scrubber system is more than enough to neutralize all of the acid that could possibly reach the scrubbers. The

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main building air is tumed over at an average rate of twice per hour. The turnover rate in the truck unloading area is also approximately two times per hour.

Mixed Acid Wastes (System 2)

Mixed acid wastes are received at the facility as liquids containing up to 3% solids. These acid wastes are treated to concentrate the acid by evaporating water, and to remove and recover hydrochloric acid. The hydrochloric acid is sold as a product. Purified sulfuric acid is reused in the facility. Metals that are present in these mixed acid wastes are subsequently recovered in other systems.

Acids arc pumped from the acid waste storage tanks to one of the reactors (either R-505 or R-507 on the process flow diagram DNP-020 in Appendix B). The contents of the reactor (2ooo gallons each) are heated up to 200' to 210'F by sending steam through the steam jackets. The water evaporates and is drawn out of the reactor through the glass-lined reflux columns. and is condensed with cooling water in the condensers. The evaporation continues until the reactor contenware reduced to one-half of the original volume, or until the pH of the condensate leaving the condenser drops to 6.95. At this point, the reactor is cooled to 1 W F by pumping cooling water through the jacket. Monitoring the pH of the condensate ensures that acids are not volatilized in this reaction step. The final volume of solution is approximately lo00 gallons in each reactor.

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If the mixed acid wastes contain chloride ion (as salts or hydrochloric acid) the contents from R-505 and R-507 are pumped to the anion exchange reactor (R-506). In this step, the reactor contents are heated indirectly with steam to a temperature of 225' to 230'F. Once this temperature is reached, sulfuric acid is slowly metered into the reactor. The sulfuric acid displaces the chlorides in the acid, creating hydrogen chloride (HCl). which is volatilized by the following reaction:

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2MCl (aq) + H2S04 (aq) --> 2HC1 (v) + M2S04 (aq)

where M represents any metal, such as copper or nickel. This operation continues until the chloride is fully removed from the acid. This is indicated by a drop in temperature from 225'-230'F down to 205'-210'F, measured at the top of the reflux column. The addition of sulfuric acid is designed to take place over a two hour period. After the HCI is removed, sulfuric acid and/or water is added to the remaining sulfate solution to increase the quantity

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back up to 2000 gallons. *The solution is then filtered and pumped to surge tanks for processing in Systems 5B, 9, and 7.

This step could potentially lead to a release of hydrogen chloride into the facility, with a possible release out of the building. However, for a significant release to occur that could impact nearby receptors, a series of independent failures would have to occur. Two scenarios are identified below.

The fnst scenario would be an accidental release of HCI into the building and a subsequent release through the vent to the atmosphere. The following independent failures would have to take place.

1. A rupture of the reactor. reflux column, condenser, receiver. or a connecting pipe must take place. Since the process operates at essentially ambient pressures, the only credible cause of failure would be an impact from a moving object. This is unlikely, since large moving objects, such as forklifts or trucks, will not be present in the process area. Although failure from corrosion is plausible, this event is deemed exaemely unlikely to occur during the lie of the plant. All of the equipment has been fabricated from materials that are resistant to corrosion. Also, normal operating and maintenance inspections would identify any problem before a catastrophic failure would occur.

2. Once the rupture occurred. the flow of sulfuric acid would have to continue in order to generate a significant quantity of HCl. The amount of HC1 generated is a direct function of sulfuric acid added. Once the operator recognized that a release of HCI into the building was occurring, he would shut off the sulfuric acid pump or close the valve to prevent further reaction and generation of HCI. The installation of HC1 detectors in the vicinity of the equipment wired to alert the operator and shut off the sulfuric acid pump would further ensure that the m i n i u m possible quantity of HCI is released.

3. The main scrubbers must fail to remove HCI from the building air. This is very unlikely, since either both scrubber pumps must fail or the caustic solution must be fully depleted by acid before the HCI is released to the atmosphere. Even if both pumps failed, caustic solution on the scrubber trays wduld remove HCI as the exhaust air passed through the scrubbers. The quantity of caustic solution

in the main scrubbers is far in excess of the maximum amount of HCl that could be generated. Also, these scrubbers are equipped with pH indicators and a l m s to alert operators if the pH drops too low.

The maximum possible amount of HCI that could be generated is approximately 5,600 pounds. This is based on an initial mixed acid waste quantity of 4.000 gallons (prior to the water evaporation step), with a maximum chloride content of 15%. and a density of 9 pounds per gallon. However, the release would take place over two hours, which is the amount of time over which the sulfuric acid is metered into the system. A release inside the building would become immediately obvious to the operators. As a worst case, it is anticipated that the maximum time for an operator to respond to a release and stop the flow of sulfuric acid would be three minutes. This corresponds to a quantity of approximately 140 pounds of HCl. During this time the HCI would disperse within the building and gradually be exhausted to the atmosphere through the scrubbers. Since this HCI would be diluted with building air, the concentration of HCl vented to the atmosphere through the stack is estimated to be less than 100 ppm.

The second HCI release scenario is one that does not release HCI into the building air, but results from failures inside the process, with HCl ultimately vented to the atmosphere. The following failuns must take place for this to occw.

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1. The condenser must fail to condense HC1 vapor. This could occur if the cooling water was shut off or if the flow of vapor through the condenser was so high as to overload the condenser. Since sulfuric acid is metered into the reactor to conaol the vaporization of HCl in the reactor, it is unlikely that a high HCl flow situation would result

2. Uncondensed HCI vapor must pass through the receivers. This could occur if the solution level was too low in the receiver or the HCI concentration in the solution was too high to begin with. However, this would only occur as a result of a failure of level indicators or negligence on the part of an operator.

3. The vacuum venturis must fail to remove HCl. The vapor from the receivers is educted into the vacuum venturis. Caustic solution circulating through the venturi will absorb and neutralize the HCl. For this system to fail, either the scrubber circulating pump must fail. or the caustic solution must be exhausted

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by neubalizatidn with acid. These scrubbers are equipped with pH indicators and alarms to alert operators if the pH is too low to ensure removal of acid gases.

4. The main scrubbers must fail to remove HC1, as described in the first scenario.

In this scenario, four independent systems must fail before HCI is released to the atmosphere. The quantity of HCI released is likely to be greater than the previous scenario, since the release is not as likely to be detected immediately by the operator. As a worst case, a maximum of 5.600 pounds of HCI could be vented to the atmosphere over a two hour period. The HCI would be mixed with other process vents and with the building ventilation air. The resulting stack concentration of HCI would be a maximum of 600 ppm for two hours. Because this scenario requires multiple independent failures to occur within the process, the probability of a release of HC1 to the atmosphere is deemed to be very unlikely.

Zinc Sludge Wastes (System SA)

Zinc-bearing sludges arrive at the facility as dry sludges in drums and as wet sludges in bulk containers. This system is illustrated on DNP-023 in Appendix B. These sludges are processed by first repulping the sludges to a slurry containing 20% solids by weight. A variety of liquid waste streams from within the plant, such as scrubber blowdown. boiler blowdowns, or sludge pit sump contents will be used to make up the slurry, along with process water. Enough sodium hydroxide (NaOH) is added to give a final solution concentration of 25 to 30 grams per liter of NaOH.

The slurry is pumped to the pre-digester (T-158) where it is heated to 180'F and agitated for two hours. The slurry is then filtered. with the filtrate going to the copper-nickel sludge wastes system (System 5B). The solids from the filter are transferred to one of the two digesters (T-150 and T-152). In the digesters the solids are repulped with water and sodium hydroxide to form a slurry with 25% solids and a sodium hydroxide concentration of 25 to 30% by weight. The slurry is then heated to 180'F and agitated for three hours to dissolve the zinc. At the end of the three hours the slurry is cooled to 140'F and filtered. The solids from the filter are sent to the copper-nickel sludge waste system and the filtrate goes to the zinc cementation lank (T- 153).

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In the zinc cementation tarlk, zinc powder is added to solution causing those metals with an electronegativity higher than zinc to precipitate out. Those metals are primarily lead and cadmium, with small amounts of copper, tin, iron, and chromium. The zinc powder is dissolved in this step. Once the cementation is complete, the slurry is pumped to the filter press where the leadcadmium concentrate is recovered. This concentrate is transferred directly to a bagger where it is bagged wet, to avoid problems associated with lead dust. The concentrate is sold as a product. The filtrate is pumped to the zinc electrowinning system (System 8).

No hazardous material vapors are created in this system. As such, the operations in this system create no significant potential for releases outside of the facility.

Copper-Nickel Sludge Wastes (System 5B)

Whereas zinc-bearing sludges are treated with alkaline solutions, non-zinc sludges are treated with acidic solutions. The primary constituents in these non-zinc sludges will be copper, nickel, chrome, and iron. Wet sludges (-50% solids) will arrive in bulk containers or special dump trucks. Dry sludges (-75% solids) will arrive in drums. This system will also process solids filtered from the zinc sludge digesters (T-150 and T-152) and filtrate from the pre-digester (T-158).

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This system is illustrated on DNP-024 in Appendix B. The sludges will be slunied with water, rinse water from copper electrowinning (System 7). and sulfuric acid to produce a slurry containing 20% solids and 25 to 30% sulfuric acid by weight. The slurry will then be heated to 140'F and agitated for three hours. At the end of this time, the digested sluny will be cooled to 120'F. This process step will dissolve the copper and nickel. The solution will then be filtered. The solids collected during this filtration will contain precious metals (e.g.. gold and silver), which will be transferred to a bagger and sold as a

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J product.

The filtered solution from the sludge digesters may or may not contain chlorides. If the chloride content is less than 0.2 grams per liter, the filtrate goes directly to the copper elecmwinning system (System 7). If the solution contains more than 0.2 grams per liter, it is pumped to an anion exchange reactor. This reactor system is identical to the anion exchange reactor described in the mixed acid wastes system (System 2). As such, this system also could potentially release HCl. The same equipment and safeguards are in place

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in System 5 B as with Syitem 2. The seventy and probability of an HCI release from this system are estimated to be very low.

The solution leaving the anion exchange reactor, stripped of chlorides, goes to the iron removal system. Aside from the potential release of HC1 from the anion exchange reactor, the potential for releases of hazardous materials from the rest of System 5B is nearly nonexistent.

Iron Removal (System 9)

The acidic solution from System 5B is predominantly copper sulfate and nickel sulfate, with substantial amounts of iron and chrome. This stream goes to the iron removal system where the solution is treated to remove iron, which is detrimental to the subsequent electrowinning process. The iron removal system is illustrated on DNP-021 in Appendix B. Iron removal is accomplished by adding either phosphoric acid or sodium phosphate to the solution. according to the following reactions:

The iron phosphate is precipitated and filtered out of the solution. The iron phosphate is converted to iron hydroxide through reaction with sodium hydroxide:

FePO4 + 3NaOH --> Fe(OH)3 +Na3PO4

The iron hydroxide, in turn, is then dried to remove water and produce iron oxide:

Fe(OH)3 + Heat --> Fez03 + 3Hz0

The iron oxide will be bagged and sold as a product. This system presents no significant potential for hazardous materials releases.

Copper Electrowinning (System 7)

The solution from the iron removal step contains a copper concentratibn of 35 to 40 grams per liter. This solution flows into the copper electrowinning cells where electric current is

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applied across a series of cathodes and anodes. The anodes are flat sheets of lead. which is insoluble in theacidic solution. The cathodes are made out of thin sheets of copper, called starter sheets. During the electrowinning process, copper is plated onto the cathodes, by the following reaction:

2CuS04 (aq) + 2H20 (l) --5 2Cu (s) + 2H2so4 (q) + (g)

After seven days of operation, the cathodes will be lifted out of the cells, rinsed off, and sold as a product. During normal operations, approximately 500 pounds of copper per hour will be plated out. The solution leaving the cells will contain less than 1 gram per liter of copper. This solution will be pumped to the nickel sulfate and sodium sulfate crystallization system (System 12).

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The copper electrowinning system is similar to the technology commonly used by the copper industry to process acidic copper solutions generated by sulfuric acid leaching of copper oxide ores. This system is shown on DNP-025 in Appendix B.

The copper electrowinning system produces no volatile hazardous materials. However. in elecmwinning operations, an acid mist may be generated in the immediate vicinity of the electrowinning cells. The generation of mist will be reduced to the maximum extent feasible by reducing the exposed surface of solution in the cells. For example, this may be accomplished by floating plastic balls (e+, ping pong balls) on the surface. The mist that is generated will be removed from the building air in the main scrubbers. The probability and seventy of a significant release of acid mist from the facility is considered to be extremely unlikely.

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Zinc Electrowinning (System 8)

! Zinc-bearing solution from the zinc sludge system (System SA) will typically contain 50 to

75 grams per liter of zinc and 200 to 250 grams per liter of sodium hydroxide. Other metals represent impurities at this point, and are present at less than 1 gram per liter. The zinc electrowinning system is shown on DNP-026 in Appendix B.

) In this system, the solution is pumped to the elecuowinning cells comprised of insoluble nickel anodes and insoluble magnesium cathodes. As elecmc current is applied across the

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cells. zinc crystals are loosely deposited on the cathodes. according to the following reaction:

2Zn(ONa)2 (aq) + 4H20 (1) --> 2Zn (s) + 4NaOH (aq) + (g)

The cathodes are periodically vibrated, and the zinc crystals settle to the bottom of the cells. The zinc crystals will periodically be removed from the bottom of the cells by opening a drain valve and allowing the zinc crystal slurry to flow to the collection tank (T-259). In this tank, the crystals will settle and will be pumped to a centrifuge and a dryer. The resulting zinc powder will be sold as a product. (A portion of the zinc powder is returned to the zinc sludge waste system (System SA) where it is used in the cementation tank to precipitate out other metals.)

The solution leaving the electrowinning cells is depleted of zinc and is essentially a solution of sodium hydroxide. The solution will go to an evaporator to remove water and increase the sodium hydroxide concentration. This solution will then be returned to System SA or 5B as a caustic solution.

The zinc electrowinning system produces no volatile hazardous materials. However, a caustic mist may be generated in the immediate vicinity of the electrowinning cells. The generation of mist will be reduced to the maximum extent feasible by keeping the zinc concentration in the solution in the cells to a minimum and by reducing the exposed surface of solution in the cells. The mist that is generated will be removed from the building air in the main scrubbers. The probability and severity of a release of a caustic mist from the facility is considered to be extremely unlikely.

Nickel Sulfate and Sodium Sulfate Crystallization (System 12)

The solution leaving the copper electrowinning system (System 7) primarily contains nickel and chrome sulfate and free sulfuric acid. This solution goes to the nickel sulfate and sodium sulfate crystallization system shown on DNP-030 in Appendix B. Nickel sulfate crystallizes out of solution by evaporating the water out the solution in the evaporator crystallizers (R-351 and R-352). This crystallization takes place wnder a vacuum at temperatures below 210'F. The nickel sulfate is essentially all crystallized by the time the sulfuric acid concentration reaches 75%. The resulting slurry of nickelmlfate crystals and sulfuric acid is pumped to a filter press. The nickel sulfate crystals are bagged while moist

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and sold as a product. The sulfuric acid filtrate is sent to the sulfuric acid tank for reuse in the facility, unless the chromium concenmtion justifies chrome removal (in System 10).

This system can also be used to produce sodium sulfate. This occurs when the sodium sulfate concentration in the solution from the zinc electrowinning system (System 8) is too high. The water is evaporated from the sodium sulfate-sodium hydroxide solution, causing the sodium sulfate to crystallize. The slurry of sodium sulfate crystals and sodium hydroxide solution is pumped to the filter. The sodium sulfate is dried and bagged for sale as a product. The sodium hydroxide solution is sent to the sodium hydroxide tank for reuse in the facility.

Both sodium hydroxide and sulfuric acid have a very low volatility. As such, only water is evaporated in the evaporator crystallizers. The potential for volatile hazardous material releases from this system is essentially nonexistent.

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> Chrome Removal (System 10)

Removal of chromium from the sulfuric acid solution leaving the nickel sulfate and sodium sulfate crystallization system may be justified to recover chromium as a by-product and to minimize the build-up of chromium with the facility's processes. The chrome removal system is shown on DNP-022. Chromium is precipitated out of solution using either phosphoric acid or sodium phosphate in the following reactions:

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The chromium phosphate is filtered, dried, and baggeb for sale as a product. No volatile hazardous materials are generated in this system and no significant release can occur from

1 this system.

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SECTION 4 CONCLUSIONS AND RECOMMENDATIONS

The Recontek facility will routinely handle a number of hazardous materials. These materials are primarily toxic metals and corrosive acidic and alkaline solutions. Most of these materials will be present in the facility as solids or liquids. These materials are essentially nonvolatile, and the most plausible contamination migration pathway would be a spill that contaminated the groundwater. However, the processes and structure of the facility are designed to prevent any such release of these materials from the facility. This is ensured through the following:

1. Proper design of the equipment, including the proper selection of materials of construction to avoid spills resulting from equipment failure due to corrosion.

2. Proper operating procedures and process contrd systems to avoid spills from accidental overfilling or other misoperations.

3. Full containment with epoxy-sealed concrete that could hold 120% of the entire contents of all process vessels in the event of an accidental spill.

In essence, the accidental spill of hazardous solids or liquids will be contained and cleaned up with no impact outside the facility. Spilled materials would be collected and reprocessed in the facility. These likelihood of spills occurring within the facility is minimized through the safeguards designed and built into the facility.

The most plausible release that could impact the surrounding community would be the release of a volatile compound from the facility's stack. The only volatile hazardous compound handled in the facility is hydrogen chloride gas (HCl), an intermediate in the processes, which is absorbed into water to form hydrochloric acid, one of the facility's products. Recontek's analytical pmgram will prevent other potential volatile compounds, such as cyanides, sulfides, or solvents, from entering the facility. Any shipment that is shown by analysis to contain significant levels of these compounds will not be accepted into the facility.

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Two separate scenarios have been identified in this study that could lead to a release of HCI from the facility. One, involves the accidental rupture of equipment handling the HCI.

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leading to a release into th'e building, followed by a failure of the main scrubber System. The second scenario involves a series of failures within the process itself, that would lead to a release out the stack

Each scenario would require multiple separate equipment and/or operational failures to occur before the HCl would be released outside the facility. Each individual failure is considered unlikely, and the combm.ation of a l l of the failures occurring at the same time is consider& extremely unlikely. The adverse impact upon the surrounding community resulting from hazardous materials releases is believed to be minimal. Because of the low likelihood and relatively low severity of a release, an offsite consequence analysis was not

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) warranted.

ERC Environmental and Energy Services Company offers several recommendations that will further minimize the likelihood of an HCl release occurring, and/or reduce the magnitude of a release.

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1. Install level indicators and/or pH indicators on the receivers for the anion exchange reactors to alert the operators if the HCl concentration exceeds a maximum value, such as 30%. in these tanks.

2. Install HCl detectors in the open building area in the vicinity of the anion exchange reactors and the receivers to detect possible leaks of HCl from the process vessels.

3. Install HCl detectors in the inlet and the outlet of the main scrubbers to detect the possible breakthrough of HCl.

To some extent these recommendations are duplicative. However, they will allow the operators to ensure that releases of HCl from the facility do no occur. Recontek has indicated that these recommendations will be implemented.

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APPENDIX A

PROCESS DESCRIPTIONS

System 2 Mixed Acid Wastes System 5-A Zinc Sludge Wastes System 5-B Copper-Nickel Sludge Wastes System 7 Copper Elemowinning System 8 Zinc Electmwinniing System 12 System 10 Chrome Removal

Nickel Sulfate - Sodium Sulfate Crystallization

I

l&m.t?a

DNP-038 DNP-020 ~~ ~ ~

DNP-023 DNP-024 DNP-025 DNP-026 DNP-030 _ . ~ ...

DNP-021 CNP-022 DNP-032 .I

DNP-033 DNP-034 DNP-035 DNP-028 DNP-027

) DNP-03 1

APPENDIX B

PROCESS FLOW DIAGRAMS

me Process Block Flow Diagram Mixed Acid Waste - System 2 Zinc Hydroxide Sludge - System SA Metal Hydroxide Sludge - System 5B Copper Electrowinning - System 7 Zinc Electrowinning - System 8 NiS04 & Na2S04 Crystallizers - System 12 Iron Removal - System 9 Chrome Removal - System 10 Virgin Chemical Storage - System 14 Water - System 15 Cooling Water - System 20 Steam - System 23 Natural Gas - System 24 H.V.A.C. - System 25 Scrubber - System 26

Revision

A G G H E D ~

C D C D D C c C B C

(These drawings ire provided in a separate package.)

APPENDIX C

PIPING AND INSTRUMENTATION DIAGRAMS

Number

256-M-101 256-M-102 256-M-103 256-M-104 256-M-105 256-M-106 ~~. . ~

2 5 6 - ~ - io7 256-M- 108 256-M-109 256-M-110 256-M- 1 1 1 256-M-112 256-M-113 256-M-114 256-M-115 256-M-116 256-M-117 256-M-118 256-M-126

m Unloading Area Metal Hydroxide Sludge Receiving and Digesting Metal Hydroxide Sludge Filters and Cementation Metal Hydroxide Sludge Filters and Cementation Metal Hydroxide Sludge Reactors Metal Hydroxide Sludge Reactors Metal Hydroxide Sludge Tanks Copper Ekctmwinning Cell House Copper Ekxxrowinning Cell House Zinc Ekmcwinning Cell House B crystauizer crystallizer V i Chemical Storage Plant Water Mixed Acid Waste Mixed Acid Waste Area and Unloading Sump Zinc Hydroxide Pre-Digester and Filter Scrubber

Revision

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

(These drawings are provided in a separate package.)

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, APPENDIX D

BUILDING LAYOUTS

t.h!Dh m HNP-10 NP-11 Scrubber Ducting h g e m e n t

Make-up Air for Scrubber Exhaust

(These drawings are provided in a separate package.)

Pevision

A A