Submitted to
UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION
Submitted by
DEVELOPMENT ENVIRONERGY SERVICES LTD
819, Antriksh Bhawan, 22 Kasturba Gandhi Marg, New Delhi -110001 Tel.: +91 11 4079 1100 Fax : +91 11 4079 1101; www.deslenergy.com
DECEMBER 2016
Policy Advisory Services in Biomass Gasification Technology in Pakistan
MINIMUM QUALITY STANDARDS FOR BIOMASS GASIFICATION PLANTS
SECOND DRAFT Version 1
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 2 of 52
DISCLAIMER
This report (including any enclosures and attachments) has been prepared for the exclusive use and
benefit of the addressee(s) and solely for the purpose for which it is provided. Unless we provide
express prior written consent, no part of this report should be reproduced, distributed or communicated
to any third party. We do not accept any liability if this report is used for an alternative purpose from
which it is intended, nor to any third party in respect of this report
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 3 of 52
ACKNOWLEDGEMENT
This document has been prepared for the United Nations Industrial Development Organization (UNIDO)
under the project title “Policy advisory services (Biomass gasification technologies)” under the SAP ID
100333: “Promoting sustainable energy production and use for biomass in Pakistan”.
Development Environergy Services Ltd. (DESL) acknowledges the consistent support provided by the
following UNIDO officials:
Mr. Alois Mhlanga, Project Manager
Mr. Ali Yasir, National Project Manager, Sustainable Energy, Biomass - Pakistan
Mr. Masroor Ahmed Khan, National Project Manager, Sustainable Energy RE & EE
Study Team
Team leader Dr. GC Datta Roy, DESL , India
Team member(s) Mr. R Rajmohan, Biomass technology expert, DESL, India
Mr. Qazi Sabir, PITCO, Pakistan
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 4 of 52
TABLE OF CONTENTS
1. INTRODUCTION ............................................................................................................................................. 8
2. APPROACH .................................................................................................................................................... 9
3. METHODOLOGY ............................................................................................................................................ 9
4. BIOMASS ENERGY TECHNOLOGIES .............................................................................................................. 11
4.1 COMBUSTION BASED RANKINE SYSTEM ................................................................................................................ 11
4.2 GASIFICATION AND GAS ENGINE BASED SYSTEM ..................................................................................................... 12
5. TECHNICAL STANDARDS & DATA SHEETS .................................................................................................... 13
5.1 TECHNICAL PERFORMANCE ................................................................................................................................ 13
5.2 TECHNICAL DATA SHEETS .................................................................................................................................. 14
6. QUALITY STANDARD-MANUFACTURING & TESTING .................................................................................... 17
7. SAFETY CONSIDERATIONS ........................................................................................................................... 19
6 ANNEXES ..................................................................................................................................................... 21
6.1 ANNEX-1: TERMS OF REFERENCE AND STAKEHOLDERS CONSULTED ............................................................................ 21
6.2 ANNEX -2: BIOMASS GASIFICATION TECHNOLOGIES & EQUIPMENT ........................................................................... 23
6.3 ANNEX-3: MANUFACTURING QUALITY STANDARD- GASIFIER REACTOR ....................................................................... 35
6.4 ANNEX-4: STANDARDS & CODES ....................................................................................................................... 42
6.5 ANNEX-5: GOOD ENGINEERING PRACTICES ........................................................................................................... 44
6.6 ANNEX-6: DEFINITIONS OF TERMS ...................................................................................................................... 47
6.7 ANNEX-7: CASE STUDIES .................................................................................................................................. 49
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 5 of 52
LIST OF TABLES
TABLE 1: PERFORMANCE STANDARDS-CERC REGULATIONS 2014 .............................................................................................. 13
TABLE 2: RECOMMENDED PERFORMANCE STANDARDS ............................................................................................................. 14
TABLE 3: TECHNICAL DATA SHEET-BOILER .............................................................................................................................. 15
TABLE 4: TECHNICAL DATA SHEET-TURBO-GENERATOR SET ....................................................................................................... 15
TABLE 5: TECHNICAL DATA SHEET-GASIFIER INCLUDING GAS CLEAN UP SYSTEM ............................................................................. 16
TABLE 6: TECHNICAL DATA SHEET-GAS ENGINE ....................................................................................................................... 17
TABLE 7: RELEVANT PAKISTAN STANDARDS ............................................................................................................................ 18
TABLE 8: FUEL PROPERTIES FOR FIXED BED GASIFIER ................................................................................................................ 23
TABLE 9: FUEL CHARACTERISTICS-REQUIREMENT FOR FLUIDIZED BED GASIFIER8 ............................................................................. 24
TABLE 10: CLEANING SYSTEMS ............................................................................................................................................ 29
TABLE 11: TYPICAL CHARACTERISTICS OF PRODUCER GAS COMPARED TO OTHER GASES ................................................................... 31
TABLE 12: FACTORS AFFECTING GAS QUALITY ......................................................................................................................... 32
TABLE 13: MAXIMUM TEMPERATURE OF ANCHOR TIPS ............................................................................................................ 37
TABLE 14: INSTRUMENTATION AND AUXILIARY CONNECTIONS ................................................................................................... 41
LIST OF FIGURES
FIGURE 1: WORK METHODOLOGY ........................................................................................................................................ 10
FIGURE 2: SCHEMATIC REPRESENTATION OF RANKINE CYCLE ..................................................................................................... 11
FIGURE 3: SCHEMATIC DIAGRAM OF GASIFIER COUPLED WITH PRODUCER GAS BASED GENERATOR SETS ........................................... 12
FIGURE 4: PROCESS OF GASIFICATION ................................................................................................................................... 12
FIGURE 5: DIFFERENT GASIFICATION TECHNOLOGIES ................................................................................................................ 23
FIGURE 6: TYPES OF FIXED BED GASIFIERS .............................................................................................................................. 24
FIGURE 7: FLUIDIZED BED GASIFICATION ................................................................................................................................ 25
FIGURE 8: GASIFIER SIZE BY TYPE ......................................................................................................................................... 25
FIGURE 9: TYPICAL PROCESS CHAIN OF A BIOMASS GASIFICATION PLANT ...................................................................................... 26
FIGURE 10: CYCLONE SEPARATOR ........................................................................................................................................ 29
FIGURE 11: WET SCRUBBING SYSTEM ................................................................................................................................... 30
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 6 of 52
ABBREVIATIONS
AEDB Alternative Energy Development Board ANSI American National Standards Institute APC Air Pollution Control APTMA All Pakistan Textile Mills Association ASME American Society of Mechanical Engineers ASTM American Society for Testing And Materials BGP Biomass gasification plant BGTs Biomass Gasification Technologies BIS Bureau of Indian Standards CERC Central Electricity Regulatory Commission CH4 Methane CHP Combined heat and power CO Carbon Monoxide CO2 Carbon Dioxide CPPA-G Central Power Purchasing Agency (Guarantee) CS Cast steel DESL Development Environergy Services Ltd. DP Dye Penetrant ERW Electric resistance welding ESP Electrostatic Precipitator EU European Union FAO Food and Agriculture Organization FBC Fluidized Bed Combustion GCV Gross Calorific Value GDP Gross development product H2 Hydrogen H2S Hydrogen Sulphide HAZOP Hazard and Operability Study HCl Hydrochloric acid HSE Health, Safety and Environment IEC International Electrotechnical Commission ISO International Organization for Standardization MCR Maximum continuous rating MOC Material of Construction MP Magnetic Particle MTDF Medium Term Development Framework N2 Nitrogen NDT Non-Destructive Testing NEPRA National Electric Power Regulatory Authority O&M Operation and Maintenance PADFA Pakistan Agriculture and Dairy Farmers Association PAH Polycyclic Aromatic Hydrocarbons PITCO PITCO (P) Ltd., Pakistan PLC Programmable Logic Controller PS Pakistan Standard PSMA Pakistan Sugar Mills Association PSQCA Pakistan Standards and Quality Control authority REAP Rice Exporters Association of Pakistan SAE Society of Automobile Engineers SBP State Bank of Pakistan SH Superheated/ super heater
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 7 of 52
SME Small Medium Enterprises SMEDA Small and Medium Enterprises Development Authority SS Stainless steel TG Traveling grate UNIDO United Nations Industrial Development Organization UPS Uninterrupted Power Supply
UNITS OF MEASUREMENTS
Parameters Unit
Atmosphere atm
Centimeter cm
Degree Celsius °C
Fahrenheit °F
Hours H
Inch Water Column WC
Kilo Calorie kCal
Kilogram/ square Centimeter kg/cm2
Kilogram/hour kg/h
Kilo Newton/ square meter kN/m2
Kilo Watt kW
Mega Watt MW
Mega Joule/kilogram MJ/kg
Mega Joule/Newton cubic meter MJ/Nm3
Micrometer µm
Milligram/Newton cubic meter mg/Nm3
Millimeter mm
Parts Per Million ppm
Tons per hour TPH
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 8 of 52
1. Introduction Pakistan is endowed with abundant availability of biomass resources, which can be economically
exploited for developing a sustainable biomass energy system. The country has been perennially facing
power demand-supply gap, which is currently estimated at 4,500 to 5,500 MW1. The system is being
maintained by resorting to load shedding; often extending to 12 to 16 hours2. Pakistan has plans to add
9,700 MW of electricity generation capacity by 2030 as per the Medium-Term Development Framework
(MTDF)2, which would partly take care of the current shortages. It would be necessary to expand and
diversify the resource base; particularly in the context of universal access to electricity in all regions of
the country. Large numbers of industries in Pakistan are currently dependent on liquid fuels for meeting
their captive demand for electricity and heat. The situation is therefore, ideally suited for promoting
biomass energy system as a sustainable and renewable alternative for the industrial sector. Power
generation through biomass can also play an important role in bridging the overall demand-supply gap
and universal energy access.
Considering the potential contribution of biomass energy system to the power sector, the United
Nations Industrial Development Organization (UNIDO) is providing technical assistance to and working
with Government of Pakistan for promoting biomass energy technologies in Pakistan.
Small and medium enterprises (SME) in Pakistan constitute 90% of the industrial enterprises and
contribute to 40% of GDP. Electricity supply to SME’s is also erratic and inadequate. A number of the
industries have high demand for process heat too. Many SMEs are looking for alternative solutions for
energy supply to achieve energy security, including biomass energy technologies.
UNIDO has contracted the Consultant through an international competitive bidding process for
providing various services including recommendations on policy support, incentives such as improved
access to finance and development of quality standards for biomass gasification equipment.
The first draft of this report was prepared based on desk research, review of global case studies on
quality standards and initial feedback from UNIDO and Alternative Energy Development Board (AEDB).
The first draft was discussed with the key stakeholders through one-on-one consultations. This second
draft report has been revised to address feedback and suggestions received during this consultation.
This report includes specific information and technical data sheets with a view to assist:
AEDB, Government of Pakistan to set the technical criteria for qualifying biomass energy
projects for promotional supports under various Government schemes
Prospective project developers in preparing their procurement specification sheets for key
components for a project to deliver the target outputs and efficiencies
1National Power Policy 2013, Government of Pakistan 2“Policy for development of renewable energy for power generation”, Government of Pakistan, 2006
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 9 of 52
2. Approach Various stakeholders use ‘minimum quality standards’ for different purposes, such as:
Setting criteria by policy makers and regulators for qualifying projects for promotional support
Verifications of equipment and systems by fiscal and monetary authorities for management of
incentive schemes
Project developers for preparing procurement specifications
Manufacturers to set up the quality management process
Plant operators to monitor efficiency and safety in operations
These objectives have been addressed in a comprehensive manner in the report. However, setting
performance standards and technical specifications play much more important role in the initial stages
of market development. Manufacturing quality standards are required much later in the journey when
the market size is large enough to support local manufacturing capability. Taking the Indian example-
biomass gasification system has been operating in India for over two decades; yet the draft of standards
has been prepared in 2014 only. Performance standards and technical data sheets have therefore, been
given primacy and constitute the main body of the report. Brief review of manufacturing quality
standard has also been provided in the main body of the report. More detailed notes on manufacturing
quality standards and good engineering practices have been prepared capturing the important and
relevant provisions from the EU and Indian drafts and annexed (Annex-3 & 5).
The process of prescribing minimum quality standard in Pakistan can be set in motion by introducing
minimum performance standards for projects and then introduction of more comprehensive standards
covering all aspects-manufacture, construction and operation and maintenance. Further, most of the
equipment and systems required for biomass energy projects are already covered under different
Pakistan or international Standards (Annex-4). Equipment for which such standards are not available can
be covered by manufacturers/exporters defined quality standards and inspection report until such time
Pakistan institutes its own standards for these.
3. Methodology The detailed tasks for the Consultant have been clearly laid out in the terms of reference (TOR) of the
study (Annex-1). The Consultant accomplished the tasks in a sequential manner as illustrated below.
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 10 of 52
Figure 1: Work methodology
The structure of this report is as follows:
Section 4: Brief review of the biomass combustion & gasification technologies
Section 5: Technical standards & data sheets
Section 6: Quality standard-manufacturing & testing
Section 7: Safety
Annex-1: Terms of reference and stakeholders consulted
Annex-2: Detailed presentation on biomass gasification technology
Annex-3: Capsule summary on manufacturing quality standards-gasifiers
Annex-4: Standards and codes
Annex-5: Good engineering practices-gasifiers
Annex-6: Definitions of terminologies used for gasification plants
Annex-7: Case studies
Preparation of the 1st draft
•Desk research on global development
•Preparation of the draft for consultation with UNIDO
•Revision of draft and circulation to key stakeholders
Stakeholders consultation
•Identification of key stakeholders & circulation of list for endorsement from UNIDO
•Interaction meetings with individual stakeholders
•Collation and circulation of report on inputs from stakeholders
Preparation of 2nd draft
•Consultation with UNIDO & AEDB on feedback reports
•Finalisation of key points for inclusion in the revised report
•Preparation of second draft
Stakeholders workshop
•Finalisation of stakeholders list for the national workshop
•Preparation of workshop agenda in consultation with UNIDO
•Assist UNIDO in organising the workshop
•Preparation of workshop recommendations report
Submission of final report
•Preparation of annotated outline of final report and getting the approval from UNIDO/AEDB
•Submission of final report along with recommendations on implementation measures
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 11 of 52
4. Biomass energy technologies Biomass resources are amenable to application of a wide array of conversion technologies for producing
thermal and electrical energy. In the context of the terms of reference for the project, these can be
broadly categorized under two different models:
Combustion based Rankine system
Gasification and gas engine based system
4.1 Combustion based Rankine system The combustion-based systems are most versatile and can utilize all kinds of biomass resources
including wastes. Biomass is fired in a boiler to produce steam and the same is used in steam turbine for
generation of power.
The technology and specifications of the various components of the project are quite akin to normal
thermal power plants except for the boiler. Several technologies have been developed for biomass-fired
boilers considering the biomass characteristics and the plant capacity. Traveling grate (TG) is the most
versatile as it can practically handle all kinds of biomasses. However, efficiency of this technology is
lower as compared to fluidized based system. The fluidized bed combustion (FBC) system is highly
sensitive to physical and chemical qualities of fuel. FBC technology is a preferred option for grainy
biomasses such as chips, shells and rice husks due to high efficiency performance. Traveling grate
technology on the other hand, is a better option for other types of leafy and non-uniform biomasses
such as stalks and straws, bagasse etc.
Figure 2: Schematic Representation of Rankine Cycle
The capacity of such projects usually range from about 1 MW to 10 MW except for bagasse, where
higher capacity projects can be configured based on cane crushing capacity and bagasse generation. The
techno-economic consideration decides the lower limit, whereas the higher limit is governed by
availability of fuel within the catchment area of the project.
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 12 of 52
4.2 Gasification and gas engine based system Smaller projects of size ranging from few kWs to about one (1) MW can be developed under the
decentralized distributed generation concept based on gasification technologies. Biomass gasification is
the process of partial combustion of biomass under controlled air supply, thus producing a mixture of
gases generally called as producer gas. Biomass gasification projects would be based on locally available
biomass resources thereby reducing the fuel management cost as well as carbon footprint as a very
small quantity of fuel would be required for transportation of biomass. Such projects can be developed
both on grid-connected and off-grid mode as captive projects for industries and energy access projects
in the rural areas.
In gasification process, biomasses such as rice husk, wood, cotton sticks etc. are gasified (incomplete
combustion with air) to produce so called ´producer gas´ containing carbon monoxide, hydrogen,
methane and some other inert gases.
Figure 3: Schematic Diagram of Gasifier coupled with Producer Gas Based Generator Sets
There are four main sub-processes in gasification, which are described below:
Figure 4: Process of gasification3
Gasification of coal and woody biomass is over 75 years old and matured technology. A number of
institutions has been working globally to improve the technology more efficient and versatile with a
3http://biomasspower.gov.in/document/download-lef-tside/Biomass%20gasification.pdf
• This includes the removal of moisture from fuel & conversion into steam.
Drying
•After biomass is heated, it undergoes pyrolysis. It is the thermal decomposition of biomass fuels in the absence of O2
Pyrolysis •Air is introduced in a gasifier in the oxidation zone. The oxidation takes place at about 700-1400°C
Oxidation
•Reducing conditions, the following reactions take place resulting in formation of CO, H2, and CH4.
Reduction
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Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 13 of 52
view to utilize locally available biomasses in cost effective manner. The gross calorific value (GCV) of
producer gas is very low at about 1,000 kCal/m3 against close to 10,000 kCal/m3 for petroleum gases.
Consequently, this requires much higher volume of the gas engine for producing the same amount of
power. The engines are specifically designed for utilizing producer gas as fuel. The gas generated in the
reactor contains harmful impurities such as particulates, tar, etc., which are harmful for gas engines. Gas
clean up system must be therefore, designed specifically for fuel types.
A more detailed description on the gasification technology has been annexed (Annex-2).
5. Technical standards & data sheets
5.1 Technical performance Setting the overall performance standards and the broad specifications of major equipment usually
serve the purpose of ‘minimum quality standard’ from the policy and regulatory perspectives. It is quite
challenging to set the overall performance standard for biomass energy technologies due to the
diversity factors. Both physical and chemical characteristics vary widely for different types of biomasses.
The GCV varies from about 2,000 kCal/kg for bagasse to close to 6,000 kCal/kg for nutshells. Size
distribution is uniform for rice husk but vary widely for bagasse, straws etc. Moisture in bagasse is over
50% but is as low as 5% in case of nutshells. Ash on the other hand is extremely low in bagasse at 2 to
3% compared to over 15% for rice husk. These variations have direct impact on choice of conversion
technologies and consequently conversion efficiencies. The regulators in India, both at the federal and
provincial levels, have been continuously addressing these issues for determination of feed-in-tariffs.
Based on extensive research and public deliberations, Central Electricity Regulatory Commission (CERC)
in India has taken the pioneering initiative of setting the performance standards for different biomass
fuel and technologies in 20144, key performance parameters are shown in the following table.
Table 1: Performance standards-CERC regulations 2014
S. No. Parameters Unit Values
Boiler Gasification
1 Fuel calorific value kCal/kg 3100 3100
2 Overall heat rate
Fluidized bed
Traveling grate
kCal/kWh
kCal/kWh
4125
4200
-
3 Specific fuel consumption kg/kWh - 1.25
4 Auxiliary power consumption
Water cooled condenser
Air cooled condenser
%
%
10
12
10
4The RE Tariff Regulations-CERC India, 15th May 2014
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Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 14 of 52
Biomass energy systems have been operating in India for over three decades. Conversion technologies
and operation and maintenance (O&M) practices have significantly improved over the years. The
performance standards determined by the CERC take into account these improvements and the
specified values are almost global benchmark. The consultants have provided consulting, engineering &
O&M improvement services for large number of biomass energy projects. Very few of these projects
have been able to achieve these standards. The consultants would therefore, recommend fixing of
standards that are more liberal during the initial stage of development of biomass energy technologies
in Pakistan. The following table shows the proposed recommendations from consultants against the
corresponding values from the CERC regulation and DESL database. Table 2: Recommended performance standards
Sl No Parameters Unit CERC DESL Data base
Recommended
A Combustion Technologies (Boiler/ Turbo-Generator)
1 Fuel calorific value kCal/kg 3,100 3.100 3,100
2 Overall heat rate
(i) Traveling grate boiler kCal/kWh 4,200 4,500-5,000 4,500
(ii) Fluidized bed boiler kCal/kWh 4,125 3,800-4,250 4,200
3 Auxiliary power consumption
(i) Air cooled % 12 13-15 14
(ii) Water cooled % 10 12-14 12
B Gasification Technologies
1 Fuel calorific value kCal/kg 3,100 3.100 3,100
2 Overall heat rate
(i) Updraft gasifier kCal/kWh - 4,600-5,000 4,600
(ii) Downdraft gasifier kCal/kWh - 5,280 5,280
3 Specific fuel consumption kg/kWh 1.25 1.5-2.5 1.8
4 Auxiliary power consumption % 10 10 10
For calorific value of fuel ranging between 2,500 to 4,000 kCal/kg, the calorific value of producer gas will
vary between 670 to 1,070 kCal/Nm3.
5.2 Technical data sheets
The key components for the two types of major biomass energy technologies are:
Combustion system
o Boiler including air pollution control (APC) system
o Turbo-generator unit
Gasification system
o Gasifier including gas clean up system
o Engine generators
Common items for all types of projects would include:
Fuel preparation and handling system
Ash handling system
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 15 of 52
Water system
Electrical and instrumentation system
For the purpose of this report, technical data sheets have been prepared for the major components i.e.
boiler including APC, turbine, gasifier, gas clean up system and gas engine.
The technical data sheets for the major components have been prepared capturing the minimum
specification requirements from performance perspectives and presented in the following sub-sections.
5.2.1 Combustion systems
The technical data sheet for combustion system i.e. boiler and turbine are tabulated below.
Table 3: Technical data sheet-boiler
S. No.
Description Units Value
1 Biomass fuel type (Rice husk, wood chips, corn cobs, straw, stalks, bagasse, others)
Name
2 Fuel gross calorific value kCal/kg
3 Fuel ultimate analysis*
4 MCR Evaporation (Gross) kg / h
5 SH Steam pressure at main steam stop valve outlet # kg / cm2 (g) 45-65
6 Steam temperature at main steam stop valve outlet# oC 410-480
7 Peak capacity of the boiler as a % of MCR capacity& %
8 Turn down ratio – travelling grate % 50-100
Turn down ratio – fluidized bed % 70-100
9 Boiler outlet flue gas temperature oC <160
10 Thermal efficiency at GCV % >68
11 Dust concentration at boiler outlet @ mg/Nm3 100
12 Auxiliary power consumption kW
The scope of supply would include the entire island including feed water and steam system, fuel and ash handling system and air and flue gas system and electrical and instrumentation and control system
Material of construction- as per relevant ASTM and Pakistan Boiler Regulations standard. Vendor to specify for different sections of the boiler
Manufacturing & testing standards-As per relevant ASME code * To be specified by the project proponent ** To be specified as per techno-economic feasibility report # To be determined as per techno-economic feasibility report. However, project at pressure <45 bar and temperature < 410oC to be discouraged &Vendor to specify @ (multi cyclone for traveling grate boilers of capacity <10 TPH, electro static precipitator or bag filters for rest
Table 4: Technical data sheet-Turbo-generator set
S .No. Description Units Value
1 Model
2 Capacity* MW
3 Configuration (Condensing/Bleed condensing/Extraction condensing/Back pressure*)
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Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 16 of 52
S .No. Description Units Value 4 Type (Reaction/Mixed/Impulse) **
5 Number of stages** Number
6 Inlet steam pressure (5% less than the SH steam pressure at the boiler outlet)
kg / cm2 (g)
7 Inlet steam temperature (10o C less than the SH steam temperature at the boiler outlet)
o C
8 Extraction/Bleed pressure* kg / cm2 (g)
9 Exhaust/Back pressure* kg / cm2 (g)
10 Turn down ratio** % 50
11 Specific steam consumption at 100% and 50% load ** kg/kWh
12 Auxiliary power consumption** kW
13 Cooling water temperature for the condensing plant o C 35
The scope of supply would include the entire island including turbo-generator unit with its auxiliaries, condensing plant along with cooling water system and the electrical and instrumentation and control system
Manufacturing & testing standards-As per relevant ASME code for turbine & IEC 34 for alternator; all electrical items to be as per IP 54 and F-class insulation
* To be specified as per techno-economic feasibility report
** Vendor to specify 5.2.2 *Impulse turbine to be allowed only for very low capacity machines
5.2.3 Technical data sheet – Gasification system
The technical data sheet for gasification system i.e. gasifier including clean up system and gas engine are
tabulated below.
Table 5: Technical data sheet-Gasifier including gas clean up system
S. No. Description Units Value
1 Biomass fuel type (Rice husk, wood chips, corn cobs, stalks, others)
2 Fuel moisture % <20
3 Fuel ash % <15
4 Model
5 Type of gasifier Downdraft
6 Rector conditions
Temperature oC 1000-1100
Pressure atm
7 Peak gas flow rate(To be specified as the techno-economic feasibility study)
Nm3/hour
8 Gas composition (%) CO-15+/-3, H2-20+/-5 CO2-13+/-3 CH4-1-4
9 Calorific value of gas kCal/Nm3 >1050
10 Peak rated thermal output kCal/hour
11 Average rated thermal output kCal/hour
12 Gasification temperature oC 850-950
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 17 of 52
S. No. Description Units Value
13 Gas temperature at gasifier outlet oC 300-500
14 Gasification thermal efficiency (hot gas mode) % >80
15 Gasification thermal efficiency (cold gas mode) % >70
16 Specific fuel consumption kg/Nm3
17 Turn down ratio % <50
18 Auxiliary power consumption kW
Gas clean up system
19 Type Wet
20 Filter material life h >1000
21 Interval between cleaning h >50
22 Particulate concentration in clean gas mg/Nm3 <15
23 Tar content in clean gas mg/Nm3 <15
24 Temperature of inlet gas to engine o C <40
The scope of supply would include the entire electro-mechanical system including fuel processing and feeding and ash removal systems and treatment plant for the liquid effluent
The hopper & body shall be of MS/SS/Ceramic with a minimum life of 5 years.
Reaction cone, throat and nozzles shall be of SS310/316/refractory/ceramic or high alumina and high temperature bricks
Table 6: Technical data sheet-Gas engine
S. No. Description Units Value
1 Fuel input (Biomass producer gas) CV kCal/Nm3 >1050
2 Particulate concentration in clean gas mg/Nm3 <15
3 Tar content in clean gas mg/Nm3 <15
4 Temperature of inlet gas to engine o C <40
5 Model
6 Capacity* kVA
7 Power factor Number .85
8 Auxiliary power consumption** %
9 Assured duty cycle & operating hours** /year
Conforming to relevant National Environmental Quality Standards for Gaseous Emission * to be specified in the techno-economic feasibility study ** vendor to specify
More detailed description of the various components of the gasification system have been provided in
Annex-2 taking into consideration that the technology is at the nascent stage of development in the
Pakistan market.
6. Quality Standard-Manufacturing & testing Well established international (IEC, ISO) and national standards exist for manufacturing quality and
testing protocols for equipment such as boilers, turbo-generator sets, gas engine generators. The
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Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 18 of 52
following table illustrates the Pakistan standards, which are applicable for equipment relevant to the
biomass energy projects except for a few systems such as gasifier.
Table 7: Relevant Pakistan standards
Examples of application (BGP equipment) Legal provisions in Pakistan
Quality of municipal and liquid industrial effluents S.R.O.742(I)/93
Quality of industrial gaseous emissions S.R.O.742(I)/93
Electrical instruments, drives, control systems, generator PS #1666-1985
Electrical instruments, drives, control systems PS #4158-1998, PS #2199-1989
Drives, pumps, blowers, moving mechanical parts, gas engine, fuel feeding system, ash removal system
PS # 2433-1989
Noise S.R.O. 1062(I)2010
Heat exchangers/boilers, compressed air system PS 2383-1989
Conveyor belts PS 2377-1989
ASME VIII and ASME PTC (different sections) codes are widely utilized for boilers and turbines (along
with IEC 34) across the globe including Pakistan. These standards can continue to be used for biomass
energy projects too.
It appears that no international comprehensive code has been developed for biomass gasifiers. Project
specific manuals have often been used primarily for monitoring of performance of donor-funded
projects. These have mostly dealt with construction and operation quality management as per the
protocol developed for the project such as World Bank sponsored CHP project in China and FAO
sponsored biogas project in Nepal5. A few specific testing protocols have been developed for particular
aspects of technology (for example ASTM standard for tar testing). An EU project “Guideline for safe
and eco-friendly biomass gasification”, Intelligent Energy for Europe Program, supported by the
European Commission seemed to have been the first major efforts towards development of an
international protocol on biomass gasifier. Several institutions in Europe were involved in developing
the protocol over two year’s period from 2007 to 2009. However, the focus of this program was
environmental and safety aspects of operation of biomass gasifier.
“The objective of the gasification guide project is to accelerate the market penetration of small-scale
biomass gasification systems (< 5 MW fuel power) by the development of a guideline and software tool
to facilitate risk assessment of HSE aspects. The guideline may also be applied in retrofitting or
converting old thermal plants in the Eastern European countries – with rich biomass resources – to new
gasification plants. The objective of this document is to guide key target groups identifying potential
hazards and make a proper risk assessment. The software tool is an additional aid in the risk
assessment”6
5FAO/TCP/NEP/4415-T for Nepal Bio-gas program in 90s 6Gasification guide-Intelligent Energy-Europe
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Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 19 of 52
Based on review of information available in the public domain, it appears that most comprehensive and
recent efforts for development of standard for biomass gasification system has been made in India
resulting in preparation of a draft protocol in 20147. Ministry of New & Renewable Energy, Government
of India had sponsored the program “advancement of research on biomass conversion technology and
end use devices” for wider adaptation of biomass energy by the industrial sector. Development of
specifications and standards for biomass energy devices and technical support for establishing test
center were amongst the key objectives of the program.
A number of specific protocols have been developed and forwarded to the Bureau of Indian Standard
(BIS) for development of a BIS document on biomass gasifier. Key amongst them include:
General information covering engineering practices
Specific protocols on safety such as gas flaring etc
Design considerations
Manufacturing tolerances
Specifications
Test procedures
Data sheets & reporting formats
The Indian protocol has been developed primarily for the manufacturers of gasifiers whereas the focus
of EU document is more on environment and safety aspects of construction and operation of gasifiers.
At the current stage of development in Pakistan, it may not be that relevant to adopt such detailed
quality protocol. A step-by-step process may be adopted as follows:
Issue of notification on overall performance specifications for promotion of biomass energy
technologies
Standardization of technical data sheets for the key components
Issue of notification on safety in work place deploying biomass gasifier
A capsule summary on manufacturing quality standard and good engineering practices have been
prepared capturing the relevant provisions in the EU and Indian documents and included at Annex-3 and
Annex-5 respectively.
7. Safety considerations General safety guidelines for operation of gasifier units:
Online oxygen sensor should be installed in the gasifier plant and online CO monitors should be
installed around the plant
Fixed online CO detectors should be installed in fuel storage buildings, gasifier building, gas
7Report of ABRC-CGPL, Department of Aerospace, IPSC, Bangalore, India, 2014
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Report Title Minimum Quality Standards for Biomass Gasification Plants Page 20 of 52
engine room (or noise hood)
CO monitors should be installed in control rooms if the same does not have positive pressure
ventilation.
A number of small portable CO monitors giving an indication and alarm should be kept in the
control room and should be provided to the operators working in the area.
Fire detection system and sprinkler system should be provided for the gasifier unit.
Automaticwatersprayingsystemshouldbeprovidedonashdischargedfromthegasifier reactor.
Fuel for gasifier should be stored in a separate room
Ventilation system should be well maintained to ensure adequate operations.
Portable fire extinguishers should be available near gasifier unit.
All motors depending on hazard-are classified-classification should be flameproof/ increased-
safety for the gasifier unit.
The following plant sections are recommended to be considered for occurrence of an ex-zone.
o Fuel storage and feeding with respect to dust explosions
o Fuel intake
o Ash and dust removal system
o Waste water removal system
o Flare and auxiliary firing system (e.g. misfiring)
o Engine and exhaust gas system
o Manholes and sampling ports
o Measurement and instrumentation points
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6 Annexes
6.1 Annex-1: Terms of reference and stakeholders consulted
Terms of reference
Objectives of the Study: The objective of the assignment is to provide advisory services and
recommendations for incentivizing investment in modern biomass conversion technologies, particularly
Biomass Gasification Technologies (BGTs), to the Alternative Energy Development Board (AEDB) and
other relevant stakeholders and to conduct the necessary activities for the establishment of rules and
regulations for BGTs under the prevailing RE Policy 2006. The consultancy firm will also provide similar
recommendations to be integrated in other existent policies/plans that could support the promotion
and adoption of biomass /BGTs in different sectors of the economy such as power generations,
industrial co-generations (combined heat and power) in SME Industries, rural electrification, etc., and
the minimum quality standards for import and local manufacture of biomass gasification equipment.
Overall scope of work: The overall scope of work for the project is as below:
Main Duties Measurable outputs to be achieved
1. Review of existing legislation, analysis and formulation of preliminary drafts
Preliminary drafts of IRRs, policy recommendations for promotion of BGTs, minimum quality standards, recommendations on capacity building for local manufacturers are prepared and shared with relevant organizations for onward discussions during the mission
2. Consultations with key stakeholders that include tri-partite meetings between AEDB, UNIDO and key stakeholders and consultation sessions to present/ explain the recommendations and collect feedback from a wider range of stakeholders
Mission plan including dates of meetings and consultations with relevant stakeholders are planned and arranged; Collection and compilation of feedback from the relevant stakeholders during the tri-partite meetings and half-day sessions in the form of meeting notes and mission report
3. Preparation of second drafts of the IRRs, Recommendations for other relevant policies/ plans
Final drafts of the (i) IRRs, (ii) Policy recommendations and (iii) minimum quality standards (iv) recommendations on capacity building for local manufacturers are prepared and shared with stakeholders for onward discussion during the workshop; Concept of the national stakeholder workshop prepared
4. Presentation of Final Drafts during a National Stakeholder Workshop
National Stakeholders Workshop conducted and final set of feedback from all relevant stakeholders collected
5. Submission of Final Policy document and Quality standards
Final IRRs, policy recommendations, quality standards and recommendations on capacity building for local manufacturers are prepared with all the feedback from the stakeholders incorporated for official endorsement
Client Name UNIDO DESL Project No. 9A0000005647
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Stakeholders consulted
The first draft of the deliverables have been shared with the following stakeholders, and the feedback
received has been incorporated in the second draft document.
Government, public sector organizations, institutions: AEDB, Ministry of Finance, NEPRA, CPPA-
G, SMEDA, PSQCA, State Bank of Pakistan Energy Deptt., Agriculture Deptt. Government of
Punjab, PBEPL
Academic: NUST, University of Agriculture, Government of Punjab
Trade associations: PADFA, APTMA, PSMA
International organizations: GIZ
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6.2 Annex -2: Biomass gasification technologies & equipment 6.2.1 Different types of technologies are being used for gasification of biomass as illustrated in the
following figure:
Figure 5: Different gasification technologies
Generally, both fixed bed and fluidized bed technologies are being deployed for biomass gasification.
Indirect heating technologies are still under development stages, internationally.
Fixed bed gasifier
In this technology, the fuel is fed into the chamber as it flows from top to bottom, during which it
decomposes into gases. These gasifiers are differentiated based on the direction of inlet of air with
respect to the exhaust of producer gas from the gasification chamber. These gasifiers can handle
moderate ash and moderate moisture fuel. Properties of biomass, which these gasifiers can handle, are
tabulated below:
Table 8: Fuel properties for fixed bed gasifier8
Description Range
Size of fuel 5- 100 mm
Moisture Content in fuel <60%
Ash content (weight %) <6%
Composition of Gas Producer gas
GCV of Gas 3-5 MJ/kg
Turn down Ratio 4:1
Temperature of operation 800-1200 o C
The pictorial representation of the fixed bed gasifier is shown below.
8https://www.epa.gov/sites/production/files/2015-
07/documents/biomass_combined_heat_and_power_catalog_of_technologies_5._biomass_conversion_technologies.pdf
Fixed Bed
Downdraft
Updrafft
Crossdraft
Fluidized bed
Circulating Bed
Bubbling Bed
Indirect Heating
Steam and Air
Plasma
Entrained Flow
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Figure 6: Types of fixed bed gasifiers9
Fluidized bed gasifier
In these types of gasifiers, the biomass fuel is combusted in suspension mode, wherein the pressure of
the air does the process of fluidization. For fluidization, the biomass needs to be prepared and fed into
the gasification chamber. In bubbling bed, the biomass is gasified in the suspension zone, whereas in
circulating fluidized bed the fines are carried by the gas and are circulated back into the furnace. These
types of gasifiers can handle biomass fuel with the following properties:
Table 9: Fuel characteristics-requirement for fluidized bed gasifier8
Description Range
Size of fuel 0.25-20 mm
Moisture Content in fuel <20%
Ash content in fuel Low 5-25%
Composition of Gas Producer gas
GCV of Gas 5-6 MJ/kg
Turn down Ratio 3:1
Temperature of operation 750-1000 o C
9http://www.bios-bioenergy.at/en/electricity-from-biomass/biomass-gasification.html
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Figure 7: Fluidized bed gasification10
One of the key characteristics of gasifiers, in addition to the producer gas that they produce, is the size
range to which they are suited. The figure below provides details of the typical size for the different
technologies:
Figure 8: Gasifier size by type11
Fixed bed downdraft gasifiers do not scale well above 1 MW in size due to difficulty in maintaining
uniform reaction conditions. Fixed bed updraft gasifiers have fewer restrictions on their scale while
atmospheric and pressurized fluidized bed and circulating bed and entrained flow gasifiers can provide
large-scale gasification solutions11. The types of gasifiers that are predominantly used at small scale are
the updraft and downdraft ones.
10http://www.oil-gasportal.com/gasification-process/ 11http://costing.irena.org/media/2793/re_technologies_cost_analysis-biomass.pdf
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This document is intended to be a source for buyers/users/manufacturers of the technology to verify the
technical specifications taking into consideration the project requirements. The document highlights
the prerequisite that needs to be taken care of during manufacturing as well as during procurement of
the biomass gasifier systems. The document is applicable for fixed bed gasifiers.
Biomass gasification plants (BGP) also need to comply with the prevailing environmental and safety laws.
In the development of this document, the following systems have been reviewed,
Biomass storage and handling on site
Biomass conveyance and feeding
Gasification reactor
Gas conditioning (cleaning and cooling)
Gas utilization in process heating & power generation
Automation and controls
Auxiliaries and utilities
Biomass gasification process chain
Biomass gasification with a downstream gas engine is particularly suitable for decentralized biomass
utilization and high efficient combined heat and power production. Figure 9 shown below presents a
simplified diagram of a biomass gasifier plant illustrating the main components, which describe and
classify the process.
Figure 9: Typical process chain of a biomass gasification plant
Biomass as fuel is fed into the gasification reactor through an air/gas-tight closure (exception is an open
top gasifier) by appropriate fuel conveying systems. The conversion of the biomass fuel into producer
gas takes place in the gasification reactor, where the thermo-chemical conversion steps of drying;
pyrolysis, partial oxidation and reduction, and ash formation take place. However, for smaller size
projects, currently in commercial operation air is the gasification agent.
biomass storage- utilities storage- intermediate storage of gasification residues- conveying technology- input units or rotary valves, vibro conveyor etc.
fixed bed gasi-fication- fluidized bed
- gasification utilities(water vapour, air, additives)- gasification boundaries(pressurised,atmospheric)
cyclone- bag house- filtering- wet dedusting/cleaning- residues treatment- etc.
- gas engine
- gas turbine
- micro gas
turbine
- synthetic
fuel
applications
- etc.
Process Automation System
Fuel supply/storage
GasifierGas cooling &Gas cleaning
Gas-utilisation
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The producer gas leaves the reactor at elevated temperatures (600-800°C) with a certain heating value.
In the subsequent steps of the process chain, sensible heat contained in the producer gas can be used
for internal process heat, drying of the biomass as well as for industrial heating purposes. In various
cleaning and cooling applications, the producer gas is subjected to dry and/or wet cleaning to achieve
the required specifications for the gas engine. However, in case of wet gas cleaning, often the sensible
heat remains unutilized.
According to the “Guideline for safe and eco-friendly biomass gasification”, during operation of a
biomass gasification plant there is an increased hazard potential due to the fact that a potentially
explosive, toxic and combustible gas mixture is produced and consumed. The producer gas and residues
(ash, liquids, and exhaust gases) may cause the following major hazards/risks:
Explosion and/or fire
Health damage to humans (poisoning, danger of suffocation, noise, hot surfaces, fire and
explosion)
Pollution of the environment and plant vicinity
Safety in design and operation therefore, remain a key consideration while promoting biomass
gasification technologies.
Biomass storage, pre-treatment, transport and feeding
Biomass storage, transport and pre-treatment may influence the fuel quality (e.g. drying during
storage), as well as the gasification process stability (e.g. producer gas quality, stability of heat and
power production, etc.). Biomass is normally stored in a separate building adjacent to the main gasifier
building or at a place with suitable cover. In most cases, the size of the storage area is chosen based on
the uncertainty of the fuel procurement mechanism/availability situation. From the storage area,
biomass is transported to the pre-treatment section. The main technologies available for pretreatment
of biomass to meet the requirements of the gasification system are drying, sizing or compacting,
depending on the origin of the fuel.
After pre-treatment, the fuel may be transported to a daily storage bunker. The most common means
of transport of biomass is belt conveyor and screws. From the storage area, the fuel is further
transported to the feeding system, which is mostly equipped with a dosing unit. The fuel conveyor may
have integrated features like sieving, a magnetic belt, removal of contaminants and foreign materials,
and/or a drying unit. A speed-controlled screw, a double-sluice lock hopper system or a rotary valve
usually does the actual feeding of the fuel into the gasification reactor.
An important aspect is to avoid the escape of gas through the feeding section during the actual feeding
and/or the airing during the same period. Anti-backfiring systems can be used or purging, using inert
gases to avoid this risk of potentially explosive atmospheres, as well as physically separating the fuel
storage and gasification reactor, minimizing fire risk potentials.
Auxiliary fuel and plant utilities
Auxiliary media/fuels such as natural gas, diesel, etc. and plant utilities such as water for cooling of
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producer gas, electricity for blowers/conveyors/fans are required during normal operation as well as
maintenance period.
Gasification reactor
The thermo-chemical conversion of solid biomass into raw producer gas takes place in the gasification
reactor (gasifier). The sequence of the biomass conversion steps of drying, pyrolysis, partial oxidation
and reduction depends on the type of gasifier. Recently, concepts have been developed and
implemented where different zones are physically separated. The main reason behind this separation is
the optimization of each step and minimization of the tar production. “Tar” has been operationally
defined in gasification work as the material in the product stream that is condensable in the gasifier or in
downstream processing steps or conversion devices. Tar is unpleasant constituents of gas, which tends
to deposit/stick on the equipment causing troublesome operations. At the exit, the producer gas
contains desired products and by- products, which are as follows:
Desired products: Producer gas (Mainly H2, CO, CH4, CO2, N2) and ashes with low carbon
content
Undesired products: Particulate matter, dust, soot, inorganic (alkali metals) and organic
pollutants (tars or PAH, Polycyclic Hydro Carbons)
Gas cooling
The purpose of gas cooling is to decrease gas temperatures to a certain level for:
Producer gas treatment (e.g. condensation of tar at lower temperatures, thereby gas cleaning
in bag filters) or
Utilization in the gas engine; cooling increases the energy density of the gas
It is recommended to recover the sensible heat in the gas, which allows the supply of internal process
heat (steam supply, evaporation energy, etc.) and the process heat for industrial applications.
Gas cleaning
Gas cleaning is required to meet the specifications set by the engine supplier, even under varying
conditions like gas flow, producer gas compositions, level of contamination, etc. Major contaminants in
the raw producer gas are particulate matter (soot, dust) and tar. Other impurities may include ammonia
(which will be converted to NOx during combustion in the engine), HCl, H2S, alkalis, and acids, all
dependent much on the process conditions, fuel and type of the gasifier.
There are different technologies for the gas cleaning: hot gas cleaning, dry cleaning and wet cleaning.
There are subsequently a number of equipment to meet the final discharge gas properties. Thus,
cleaning system must be optimized.
Gas generated is in range of 500-600oC. Gas is laden with tar and fly ash. Gas engine requires gas free
from these impurities thus gas needs to be conditioned and cooled to the desired temperature before it
is fed into the engine.
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Table 10: Cleaning systems12
Techniques Temperature(°C) Particle Reduction (%) Tar Reduction (%)
Sand bed Filter 10 to 20 70-99 50-97
Wash Tower (Gas Scrubber and Chiller)
50-60 0-98 10 to 25
Wet electrostatic precipitator 40-50 >99 0-60 Fabric filter 130 70-95 0-50
Fixed bed Tar absorber 80 NA >95 Catalytic air cracker 900 NA >95
Cyclone separator
This is most effective solution to remove the high-density material form low density gas. Gas is blown
into the equipment, centrifugal forces causes heavy dust particles to move outwards and then they
collide with the internal surface of the metal and slides down, whereas gas lighter than dust experiences
less force, moves upwards. Hot gas is used in the cyclone as higher temperature gas is lighter thus
providing the higher cleaning efficiency.
This separation causes the reduction of 70-80% of the fines in the gas. Lighter weight fine particles and
tar is carried with gas. These are not separated in this stage.
Figure 10: Cyclone separator
Gas cooler
Gas needs to be cooled to the room temperature, as the desired temperature at the inlet of gas engine
is ambient. Small quantity of tar condenses during the cooling of gas, and less quantity of fine particles
are removed with water.
12Journal of Applied Fluid Mechanics, Vol. 5, No. 1, pp. 95-103, 2012
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Wet scrubber
Cooled gas is made to contact with jet of water. Velocity of water jet carries away the fine particles and
wet particles heavy in weight falls down and conveyed with water in the return channel. Moist gas is
discharged from the system. Gas temperature further decreases in this system.
Almost all fines are removed in equipment and discharged gas is contains the dust and tar in the
permissible limit of gas engine.
Figure 11: Wet scrubbing system
Gas chiller
Discharged gas from the gas cooler is sent to chiller section where
the temperature is decreased to the range of the gas temperature
required for the gas engine.
Chilled gas contains moisture and passes through the demister and
chilled gas is sent to the receiver, from where it is fed to the engine.
Slight amount of tar is condensed and is carried away with
discharged water from the chilling tower. Temperature of the
chilled gas is limited to 7-8 oC.
This temperature is limited by the gas temperature required at the
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engine as per SAE norms and engine design. Ambient air and gas temperature needs to be 25oC for best
performance13.
Gas utilization
The gas engine entails a conditioning of the biomass-derived gas, providing gas parameters determined
by the specifications of the engine (nearly constant producer gas temperature, sufficient heating value,
purity level, humidity as well as gas-engine inlet pressure). Gas engine is a commercial commodity,
which means that the gasifier manufacturer must fulfill the requirements set by the engine supplier.
HSE aspects
Small-scale biomass gasifiers operate normally with air as the gasification agent. This results in a certain
gas composition that differs largely from other gases like biogas or natural gas. As per the “Guideline for
safe and eco-friendly biomass gasification”, typical characteristics of producer gas are given in the table
below:
Table 11: Typical characteristics of producer gas compared to other gases
Parameters Producer gas
CO (vol %) 12-20
H2 (vol %) 15-35
CH4 (vol %) 1-5
CO2 (vol %) 10-15
N2 (vol%) 40-50
Heating value MJ/Nm3 4.8-6.4
Explosion range (vol%) 5-59
Air to gas ratio 1.1-1.5
Performance considerations
The following performance considerations are to be taken care of for fixed bed biomass gasifiers14.
Cold gas efficiency = Energy content in the gas per kg of biomass/energy content in the biomass.
Computation of cold gas efficiency shall be carried out as under:
Compute/measure the gas calorific value per kg of biomass using the gas output rate; biomass
feed rate, gas composition and Junker’s calorimeter measurement.
Compute the biomass calorific value using the Bomb calorimeter measurement. Measure cold
gas efficiency = Energy content in the gas per kg of biomass/energy content in the biomass.
13Cumin’s Specification sheet 240 kWe Producer Gas engine 14“Advanced Biomass Research Centre (ABRC)”, Indian Institute of Sciences (IPSc) Bangalore, supported by the
Ministry of New & Renewable Energy (MNRE)
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In case of conflict in the energy content in the gas with respect to computed gas calorific value
derived from gas composition and Junker’s calorimeter readings, Junker’s calorimeter reading is
to be considered as final.
Computation of calorific valve of both biomass & gas should be done considering biomass
moisture content agreed as basis of design/ performance.
Gas fed into the engine should conform to the following limits for the impurities.
Table 12: Factors affecting gas quality
S. No. Factors Affecting Units Values
1 Tar ppm <5
2 Particulate Matter ppm <10
3 Condensate 0
4 Dust Particle –max size µm 5
5 Dust-Quantity Mg/Nm3 5
6 Tar-Dew point °C Min 5°C bellow gas temperature
The various components of the system are briefly described as follows.
Gasifier reactor
The reactor is a cylindrical vessel made of mild steel, with an inner lining of cold face insulation bricks
and ceramic tiles composed largely of alumina. Air nozzles, provided around the combustion zone, are
kept open during the running of the system. To allow for uniform air availability across the reacting bed,
an additional air nozzle called the central nozzle is directed to the reactor core. A water seal with a
removable cover forms the top of the reactor, which is kept open during the entire operation of the
system, to facilitate primary air induction and loading of feedstock. A grate is provided at the reactor
bottom to hold the char or ash as the case may be, with a mechanism for intermittent extraction of
char/ash.
Gas cooling system
It consists of a direct water impingement cooler, which is meant for cooling the hot gases from the
gasifier reactor to ambient for engine applications and scrubbing the gas to remove the entrained tar
and particulate matter. When the gasifier system is operated at the rated load, the system requires 80-
100 m3/h on a continuous basis for a one (1) MW rating. The coolers perform the twin functions of
cooling and cleaning the producer gas.
Gas filtering system
This sub system consists of a series of quartz based gas filter, a bag filter, a catalytic converter and a fine
quality paper filter. The purpose of the filtering system is to reduce the quantity of tar, particulate
matter and moisture in the gas to levels that are acceptable for direct admission into gas engines.
Burner
This is provided to check the initial quality of the combustible gas as also for emergency flaring.
Instrumentation & control automation
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The Instrumentation consists of automatic gas flow meter and pressure indicators located on-line to
monitor the quantity and rate of gas production. Instrumentation is also provided for monitoring
temperatures in the reactor, automatic retraction of top cover, automatic start/stop of the bucket
elevator, automatic control of gas feed into the engine and automatic char/ash extraction. Relevant
parameters such as system pressures along the gas flow path, gas consumed by the engine and
operating parameters such as pressure, temperature, etc. are also displayed for operational
convenience.
Controls & safety features
The following instrumentation and control systems are desirable for efficient and safe operation of the
system.
1. Oxygen monitoring system - to indicate if there is any leakage of air into the system,
forewarning the operator to take necessary preventive action
2. Water seals - most of the system elements are provided with water seals to release pressure in
the event of the system being pressurized. The water seals, with their low-level bubbling noise,
also act as adjunct annunciators of system pressure build-up.
3. Automatic reactor shut off - to shut off the reactor automatically in the event of power failure.
4. The automation for start-up consists of a PLC based control system, which controls the
following actions
Automatic retraction of top cover with pneumatic arms
Automatic positioning of two-way chute
Automatic cut-on and cut-off of biomass loading in the reactor using ultrasonic sensors
Automatic control of blower operation providing secondary air to the reactor
Automatic extraction of ash from the grate bottom
Automatic control of air blower speed to suit engine requirements
Automatic emergency flaring of gas
Automatic emergency shutdown of reactor
Computerized data acquisition system The following relevant data pertaining to systems operation can be recorded and acquired online on the
computer:
Reactor temperatures at different zones
Biomass consumption rate
Gas-flow rate
Technical trouble-shooting
Maintenance schedule, both preventive and breakdown
Auxiliaries
The plant should incorporate size reduction unit for cutting the biomass into smaller pieces prior to
feeding into the gasifiers. The biomass can be transported with the help of a front-end loader, which
consists of a tractor provided with front-loading articulated arms fitted with loading bucket, for loading
it onto the hopper of the bucket elevator. Operation of the gasification plant requires loading of biomass
into the reactor in a continuous batch wise basis. A bucket elevator of suitable capacity to facilitate
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continuous loading of biomass into the reactors via two-way chute may be used. Cooling water is
required for cooling and scrubbing of the gas prior to supply of gas to the engine. To optimize the
utilization of limited resources, the system will recycle the wash water. A water treatment plant for
continuous filtration and purification of water is provided. A cooling tower is provided for cooling the
recycled cooling water, after water treatment, to maintain its temperature within the prescribed limits.
The system is provided with char extraction unit consisting of a screw blender for intermittent extraction
of char/ash. The coconut charcoal, which has commercial value as an industrial adsorbent, is milled to
the required size, bagged and sold.
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6.3 Annex-3: Manufacturing quality standard- gasifier reactor Reactor wall thickness should be calculated as per good engineering practices and considering
internal pressure / vacuum of 1000 WC. Minimum thickness should be 5 mm
The manufacturer should specify minimum corrosion allowance
Reactor should be designed and manufactured as per attached data sheet
All nozzle connections on the shell should be made seamless
Use of cast-iron for any pressure part or any part attached to the reactor shell by welding is
prohibited
All plates should be manufactured by open hearth, electric furnace or basic oxygen process should
adhere to mentioned in PS equivalent, E250 at its minimum
For components inside the reactor, suitable MOC should be selected based on the service
temperature
Suitable device / door / seal should be provided to ensure against fire, explosion
A suitable grate / system in the bottom should be provided for periodical removal of ash without
disturbing the process
Adequate access for cleaning and maintenance of refractory should be provided
Man-hole cover should be provided with a davit or hinge
Adequate number of peep-holes should be provided for process observation and temperature
estimation as long as it does not affect the safety in operations
Lifting lugs should be designed and located in such a manner that no part of the reactor gets
over-stressed during transportation & erection. Height of the reactor from ground should provide
for convenient disposal of ash and wastewater. Minimum clearance below the reactor or any
auxiliary equipment where people movement is envisaged should be 2.2 meters.
Material to be used should conform to:
a) ASME Section 11
b) PS equivalent grade
Minimum quality acceptable should be: (Reference for these recommendations)
a) Plates: PS equivalent
b) Forgings: SA-105
c) PS equivalent tested & inspected as per SA-181 or SA-105
d) Nozzle pipes: SA-106, PS equivalent
e) Fittings: SA-234, SA-420
f) Elbow should be long radius type
g) Bolting: SA-193 Gr.B7, SA-194 Gr.2H
Piping and terminals
Material of construction
Gas Piping : SS Seamless
Air / Water Piping : CS ERW
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Corrosion allowance
Unless otherwise specified in purchaser’s piping material specification, the following corrosion
allowance should be provided as a minimum parameter in all the process and utility systems:
Carbon Steel : 3.0 mm
Ferritic Alloys : 3.0 mm
Austenitic steel : NIL
Non-Ferrous : NIL
Design temperature
Minimum and maximum design temperature should be determined in accordance with the provisions
of ANSI B 31.3 and in no case should be less severe than those specified.
Design pressure
The design pressure of piping should be determined in accordance with the provisions of ANSI B
31.3 and in no case should be less than the following:
a) 3.5 kg/cm2
b) Design pressure of the equipment to which the piping is connected.
c) Set pressure of safety valve, which protects the system.
d) For piping at the discharge of centrifugal pump, it should be higher than
1. 2 times the maximum pump differential pressure plus the maximum suction pressure
Total shut off pressure plus the maximum suction pressure
e) Design pressure for piping systems operating under vacuum should be full vacuum
Criteria for piping supports
All piping should be adequately anchored, guided or supported to prevent undue deflection /
expansion, vibration or loads on connected equipment & piping and leakage at joints. Piping at
equipment such as heat exchangers and pumps, and valves requiring periodic maintenance should be
supported in such a way that the equipment and valves could be removed, with a minimum necessity
of installing temporary pipe support.
Suitable supports should be provided for lines, which do not need any support, but otherwise
become unsupported by opening of flange, etc. for maintenance; and thus may transfer load on
attached equipment, etc.
Threaded connections are not acceptable
Suitable vents & drains should be provided
Testing requirements- Non Destructive Testing (NDT) requirements
Depending on the severity of application, extent of NDT should be decided. As a rule, all alloy
steel, hydrogen, oxygen, NACE, and any other high pressure and lethal service should have
100% radiography on weld joints. Castings used in these services should have 50%
radiography/ultrasonic.
All piping should be hydro tested at 1.5 x design pressure.
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Allowable movement and loads
Reactor process nozzle/terminals should be designed to accept moments & forces or the
movement from external piping/ducting
Piping should be designed as per prevalent standard engineering practices for such applications
Refractory and insulation
The temperature of outside casing should not exceed 82°C at an ambient temperature of 27°C
in still air
All parts of refractory should be designed to allow for proper expansion of all parts. Where
multilayer or multi component linings are used, joints should not be continuous through the
lining
Any layer of refractory should be suitable for a service temperature of 167°C above its
calculated hot face temperature
Maximum temperature for anchor tips should be as per the specification given in the table below
Table 13: Maximum temperature of anchor tips
Anchor Material
Maximum Anchor Temperature
°F °C
Carbon Steel 800 427
TP 304 stainless steel 1400 760
TP 316 stainless steel 1400 760
TP 309 stainless steel 1500 815
TP 310 stainless steel 1700 927
RA 330 stainless steel 1900 1038
Alloy 601 2000 1093
Ceramic studs and washers >2000 >1093
Brick and tile construction
Brick construction could be used for gravity walls, floors, or as hot-face layers
Gravity walls should be of mortared construction. The mortar should be non-slagging, air-
setting, and chemically compatible with adjacent refractory, including the rated temperature of
the brick
Gravity walls should be of mortared construction. The mortar shall be non-slagging, air-
setting, and chemically compatible with adjacent refractory, including the rated temperature of
the brick
Minimum service temperature for a hot face brick layer should be at least 10% more than the
inside design temperature
Brick linings should be supported by metal support shelves (lintels) attached to the casing on
vertical centers not to exceed 6 feet (1.8 meters). Support shelves should be slotted to provide
for differential thermal expansion. Shelf material will be defined by the calculated service
temperature; carbon steel is satisfactory up to 700°F (317°C).
Expansion joints should be provided in both vertical and horizontal directions of the walls, at
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wall edges, and about burner tiles, doors and sleeved penetrations.
Castable construction
Hydraulic-setting castables are suitable as lining for all parts of fired heaters. Minimum
castable construction is a 1:2:4 volumetric mix of Lumnite-Haydite-Vermiculite, limited to a
maximum service temperature rating of 1038°C (1900°F) and clean fuel applications. This
castable should be limited to 8-inch (20.3 cm) maximum thickness on arches and walls.
For dual layer castable construction, the hot face layer should be minimum 3 inches (7.6 cm)
thick. The anchoring systems should provide independent support for each layer when in arch
or other overhead position.
Anchoring penetration should not be less than 70 percent of the individual layer being anchored
for castable thickness greater than 2 inches (5 cm). The anchor should not be closer than ½
inch (1.3 cm) from the hot face.
The anchoring spacing should be maximum three times the total lining thickness but should
not exceed 12 inches (30 cm) on a square pattern for walls and 9 inches (23 cm) on a square
pattern for arches. The anchor orientation should be varied to avoid creating continuous shear
planes.
Anchors for total castable thickness up to 6 inches (15.2 cm) should be minimum of 3/16 inch
(4.8 mm) diameter. Greater refractory thicknesses require a minimum of ¼ inch (6.3 mm)
diameter anchors.
Castable linings in header boxes, breechings, and lined flue gas ducts and stacks should not be
less than 2 inches (5 cm) thick.
Anchors in 2-inch (5 cm) thick castable linings should be held in place by 10 gauge minimum,
carbon steel chain-link fencing, wire mesh, or linear anchors welded to the steel casing.
When metallic fibre is added for reinforcement, it should only be used in castables of 880 kg/m3
(55 lbs./cft.) or greater density. Metallic fibres shall be limited to not more than 3% by weight of
the dry mixture.
Low iron content (maximum of 1.5%) materials should be used when total heavy metal
content within fuels exceeds 100 parts per million.
Hydraulic setting castables, in particular lightweight and medium weight insulating castables,
are susceptible to the development of alkaline hydrolysis (carbonization) when placed under
high ambient temperatures and/or high humidity conditions shortly after placement.
To reduce the tendency for hydraulic setting castables to develop alkaline hydrolysis, an
application of an impervious organic coating should be applied immediately after castable
placement and reapplication of the same coating shortly after the twenty-four (24) hour cure.
The use of forced drying by air movement or low temperature to remove a percentage of
the mechanical water prior to the application of the impervious coating could further reduce
the possibility of development of alkaline hydrolysis. Alkaline hydrolysis is a natural occurring
phenomenon such that the use of either or both of the above procedures may not entirely
prevent the formation thereof.
In instances where alkaline hydrolysis has occurred, the loss in refractory thickness is usually
less than 10 mm (3/8 inch). When this occurs, the loose material should be brushed off and an
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impervious organic coating applied.
Structure and Appurtenances
Structures
Structural steel should be designed to permit lateral and vertical expansion of heater parts.
Gasifier casing plate should be seal welded externally to prevent air and water infiltration.
When fireproofing is specified, the main structural columns from the base to the floor level plus
the main floor beams should allow for 3 hours fire resistance and/or 2 inches (50mm) of
fireproofing.
Duct structural systems should support ductwork independent of expansion joints during
operation, when idle or with duct sections removed.
Ladders, platforms, and stairways
Platforms should be provided as follows:
o At fuel feeding point
o At nozzles having any operating control
o At nozzles having local indicators
o At any other maintenance requirements
Gasifier reactor with shell diameters greater than 3 meters (10 feet) should have a full circular
platform at the floor level. Individual ladders and platforms to each observation door may be
used when shell diameters are 3 meters (10 feet or less).
Platforms should have a minimum clear width as follows:
o Operating platforms, 900 mm (3 feet)
o Maintenance platforms, 900 mm (3 feet)
o Walkways, 750 mm (2 feet, 6 inches)
Platform should be designed for 5KN/m2 live load.
Platform decking should be 6 mm (l/4 inch) checkered plate or 25 mm by 5 mm (1 inch by 3/16
inch) open grating. Stair treads should be open grating with checkered plate nosing.
Dual access should be provided to each operating platform except when the individual platform
length is less than 6 meters (20 feet).
An intermediate landing should be provided when the vertical rise exceeds 9 meters (30 feet)
for ladders and 4.5 meters (15 feet) for stairways.
Ladders should be caged from a point 2.3 meters (7 feet, 6 inches) above grade or any platform.
A self–closing safety gate should be provided for all ladders serving platforms and landings.
Stairways should have a minimum width of 750 mm (2 feet, 6 inches), a minimum tread width
of 240 mm (9l/2 inches), and a maximum riser of 200 mm (8 inches). The slope of the stairway
should not exceed a 9 (vertical) to 12 (horizontal) ratio.
Headroom over platforms, walkways, and stairways should be a minimum of 2.1 meters (7
feet).
Handrails should be provided on all platforms, walkways, and stairways.
Handrails, ladders, and platforms should be arranged so as not to interfere with any item
removal.
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Where interference exists, removable sections should be provided.
Materials
Materials used in the fabrication of gasifier should conform to the following specifications or
purchaser’s approved equivalent specifications:
o Structural shapes, ASTM A 36, A 242, A 572, PS equivalent
o Plate, ASTM A 36, A 283 Grade C, A 242, or A 572, PS equivalent. A
o Structural bolts, ASTM A 307, unfinished or equivalent.
o High-strength bolts, ASTM A 325 or ASTM A 490 or equivalent.
o Pipe for columns and davits, ASTM A 53 Grade B or equivalent.
Materials for service at design ambient temperatures below -30°C (-20°F) should be as specified
by the purchaser.
Flare stack
Flare stack shall be governed by Central & State pollution control boards
Stack design shall be as per PS (latest edition)
Electrical
Electrical equipment viz., motors, junction boxes, instruments should conform to
requirement of area classification to be identified as per the requirement of API-500 or PS standard
for classification of hazardous area.
Gas cooling & cleaning
The extent of dust removal requirement depends on the final use of gas, i.e. whether (a) as fuel for
gas engine or (b) for generating process heat, i.e. burnt gas coming in contact with product or (c) for
generating utility heat.
Gas cooling
Heat exchangers should be designed as per applicable codes and standards whenever cooling with heat
exchangers is envisaged.
Gas cleaning
Gas cleaning may be achieved in the following manner:
Combined gas de-dusting and gas cleaning by suitable scrubber columns
Separate gas de-dusting and gas cleaning by means of a preliminary hot/warm filtration for
particle separation with subsequent gas cleaning of tarry compounds.
Dry gas cleaning: Dry gas cleaning can be hot gas cleaning with heat-resisting filters and into
dry gas cleaning in fabric filters, depending upon the temperatures.
The cleaning steps in the hot gas cleaning process can be the following:
o Cyclone - primary de-dusting (prior to gas cooling)
o Hot gas filter - fine de-dusting (prior to gas cooling)
o Bag filter system - fine de-dusting (after gas cooling)
o Other filters (sand bed filter, active coke bed)
Wet gas cleaning: Wet gas cleaning is purification by liquid scrubbing agents in a suitable
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scrubber system and this additionally cools the gas.
Tar treatment systems are used to reduce the tar from producer gas and may be of the
following types depending upon the end usage of producer gas.
Fixed bed absorbers, thermal tar treatment, Catalytic tar treatment systems, Wet Scrubbers,
ESPs, etc.
Dust treatment systems used to remove the dust in producer gases may be Dust ESPs,
Filtration de-duster, etc.
Water and air pollutants generated from the gasifier plant should be treated to meet the
pollution control requirements
Instrumentation and control
Under the current economic conditions, a biomass gasifier plant needs to be fully automated, allowing
for unmanned operation. Full automation has the advantage that safety procedures can be included in
the system. Any plant needs an automation and control system. However, for small-scale systems, the
instrumentation and control system may become relatively expensive. The following items are mostly
automated:
Fuel feeding (rotational speed controllers, or opening of valves);
Fuel level in the gasifier reactor;
Oxygen supply to the gasifier reactor (linked to the fuel feeding);
Cleaning sequence of filters(dependent on pressure drop);
Air-gas ratio to the gas engine
Following table describes the instrumentation and auxiliary connections required: Table 14: Instrumentation and auxiliary connections
S. No. Item Function
1 Thermocouple with Digital display and controller
Hot gas temperature measurement and high temperature warning signal Cooled gas temperature measurement Circulating water temperature measurement Biomass drier temperature measurement and control
2 Manometers Pressure measurements across each equipment
3 Pressure transducers with digital output
Pressure measurements at critical points for process control (optional if specified by purchaser)
4 Biomass Level sensors To maintain the biomass level in the reactor (optional if specified by purchaser)
5 Load Cells/Weighing scales
To maintain the char extraction To record biomass loading
6 Flow Meters For gas flow measurements For water flow measurements
7 Oxygen Monitor To measure level of Oxygen in producer gas
8 Gas Analyzer Gas composition measurement (optional if specified by purchaser)
9 Flue Gas Analyzer Measure engine exhaust (optional if specified by purchaser)
10 CO monitor To measure CO levels at work area (personal safety)
11 Moisture meter Biomass moisture control
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6.4 Annex-4: Standards & Codes A. Mechanical Pakistan Standards International Standards
Blowers ISO 5389; ISO 1217
Boiler PS 2383-1989 ISO 1129:1980
Compressors PS 2482-1-1989/ 2482-2-1989/ 2482-3-1989
ISO 3857-2:1977
Condenser PS 1326-1974 ASTM A214 / A214M - 96(2012)
Conveyors PS 2377-1989 ISO/TC 41/SC 3
Cooling tower *BS 4485 ISO 16345:2014
Crane PS 4430-1999 ISO 4301-1
Fans PS 663-1987 ISO 5801:2007
Heat exchangers PS 3386-2-1993 ISO 1129:1980
Gear box PS 4084-1998 ISO/TC 60
High pressure valves & fittings PS 1008-1974/ 558-1992/911-1991
ASTM A961 / A961M - 15; ASTM A694 / A694M - 16
Low pressure valves & fittings PS 1008-1974/ 558-1992/911-1992
ASTM A961 / A961M - 15; ASTM A694 / A694M - 16
Pressure vessels PS 3386-2-1993 ISO 16528-1:2007
Pumps PS # 2433-1989 ISO 5199:2002; ISO 9905:1994
Turbine PS 893-1987 ISO 14661:2000/ IEC-34/ ASME PTC-6S
Siesmic considerations PS 4642-3-2000 ISO/DIS 3010
Wind load PS 4427-1999 ISO/FDIS 4302
B. Electricals & instruments
Current transformer PS 826-2000 IEC 60044
DC Battery PS 434-1964 IEC 62133
Earthing PS 4083-1998 IEEE 80
Generator PS 1666-1985 IEC 34
HV Cables PS 1176-1989
HV switchgears PS 2109-1989 IEC 298
Illumination systems PS 2111(845)-1989 IEC 61547
Lightning protection PS 1046-1974 IEC 61024
LV Busduct *IS 8623 IEC 61439
LV Cables *IS 1554 IEC 60055
LV switchgears PS 1300-1974 IEC 60439/IEC 61915
Motors PS 186-1987 IEC 60034-30-1:2014
Potential transformer PS 1602-1983 IEC 60076
Power transformers PS 563-1-1996 IEC 76
Protection relay PS 307-1963 IEC 55
UPS PS 2899-5-1991 IEC 146
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A. Mechanical Pakistan Standards International Standards
Electrical instruments, drives ,generator
PS #1666-1985 IEC 61922/IEC 61800
Electrical instruments, control systems
PS #4158-1998, PS #2199-1989
IEC 60546
C. MOC for piping
>500 oC *SA335 Gr P22 ASTM A106/A106M
400 to 485 oC *SA 335 Gr P11
< 400 oC *SA 106 Gr B ASTM A320/A320M
Pipe fittings PS 911-1991 ASTM A 234 ANSI B 16.9/ B 16.28/ B 16.11
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6.5 Annex-5: Good engineering practices15 Good engineering practice related to process is the responsibility of the manufacturer.
Choice of material
Reactor vessels, valves and piping material should be constructed from good quality materials
Heat resistant stainless steel or other appropriate material shall be chosen for the gasifier and
gas cooling device
Chemical resistant stainless steels recommended for gas scrubbing and washing media
circulation
Gas tightness
Gas tightness is important to avoid gas escape and air intake, which may lead to the formation of
explosive mixtures and/or the release of toxic gas. The following engineering practices are suitable to
ensure gas tightness.
The use of welded connections is preferred above flanges, in particular for hot pipes above
500°C. In all cases, proper flange sealing like chemical and thermal resistant material need to be
used.
All pipes, aggregates, measurements, devices have to be of proper materials
Proper material should be used with regard to chemical resistance, temperature and pressures
corrosion, particle size.
Valves
All air inlets to the gasifier and gas outlets the same, including fuel feeding section, flare and
engine should be equipped with block devices or anti-back firing valves in series (after the other
in the same line)
When valves are in contact with pyrolysis or gasification gas, they may get stuck
Valves used to ensure a safe mode in case of failure and emergency stop must be of the fail-
safe type
Valves at air pipes, filters and cylinders should have position micro switches
Faulty settings of manual valves should not be possible. Malfunction of critical valves should be
detected
Electrical devices
It is recommended to electrically ground all gas conduction parts
PLC should be properly grounded in order to avoid malfunction and accidents
Galvanic separation of electrical supply of measurements devices is strongly recommended
It is recommended to supply PLCs with uninterrupted power supply units(UPS)
Duplicate plant key operation measurement points (critical temperatures, pressures, etc.) are
recommended for monitoring using a secondary measurement system during emergency case
or in failure of the main PLC system
15“Final guideline for safe and eco-friendly biomass gasification” European standard
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Gasifier inlet into engine should be earth grounded, and shielded cables should be used to
avoid electrical break downs that would cause back firing in the inlet system
Control and safety devices
CO detectors, giving indication and alarm at about 25/50 ppm CO, must be installed in rooms
with equipment containing pyrolysis or gasification gas
Pressure and temperature sensors included in the safety concept should be duplicated or
tripled.
The failure probability regarding the influence of operation/ installations must have been
estimated.
Heat exchangers between gas and air from a possible hazard source in case of leaks between
the media e.g., thermal cracks or corrosion. Similarly, for expansion joints in long welded pipes.
Hazards from this possible malfunctioning should be avoided by well-designed equipment and
by temperature and oxygen sensors downstream to be able to detect the leakages
It should not be possible to tamper safety related leakages.
All alarm values should be specified in the manual before start-up of the plant
Temperature sensors should be installed before and after the main plant reactor system
components. Preferred and allowable operation temperatures shall be available for the
operators in plant manuals and secured with proper alarm levels
Movable or rotating parts
The plant movable parts, such as conveyor belts, motors, engines could generate a risk of gas
explosions. They should be shielded and equipped with visible signs and emergency stop
At standby, the gas blowers and other rotating equipment in the product gas-line should be
maintained, otherwise it may corrode or seize through the condensation of tar, which will lead
to breakdown
Hot surfaces
The plant can have several hot surfaces. These could generate a risk of gas or dust explosion and
present a risk of accidental contact with operators. The plant equipment
that can pose an occupational risk due to high temperatures should be adequately identified
and protected (shielded)to reduce risks
Training should be provided to educate operators regarding the hazards related to hot surfaces
and the use of personal protective equipment (e.g. gloves, insulated clothing, etc.)
Gas flaring systems
The flare or a similar device for burning the gas is used when the gas quality is poor and cannot
be used in the gas engine, or in case of engine failure
In case where valves in contact with pyrolysis or gasification gas stuck, the gas should
automatically be flared
Gasifier will have to vent gases as they purge pipe-work from the gasifier to the engine. At Start-
up, the gasses they purge pipe-work from the gasifier to the engine
The flare should be equipped with
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o An automatic ignition system
o Flame monitoring with alarm
o Water seal
A HAZOP study is recommended to understand the issues relative to the gas flaring system and
then identify the suitable counter-measures, for instance inert gas purging
Safety equipment
The following safety equipment or tools should be present in each separate part and/or building of the
gasifier plant:
Fire detection and suppression equipment that meet the internationally recognized technical
specifications for the type and amount of flammable and combustible materials stores at the
facility
CO detection system
Fire-fighting equipment
Personal protective equipment: ear protectors, eye glasses, gloves, respiratory equipment,
personal
CO detectors
Emergency equipment: showers, first aid kit
Inspection standards
Non-destructive tests need to be carried out for establishing that all the material, workmanship and
performance of the equipment are as per the agreed purchase conditions. These tests include:
Reviewing material test certificates to establish physical and chemical properties. In the absence
of original manufacturer’s test certificates to establish physical and chemical properties.
Welding procedure qualification record and welding processes should be certified and
verified.
NDT, viz. DP, MP, radiography and UTC should be carried out if applicable as per the purchase
specifications.
Hydrostatic testing of vessels and piping should be carried out as specified in purchaser’s data
sheet.
Tests viz., utility consumption and equipment and system performance should be carried out
during pre-commissioning stage.
All stage tests & the vendor should maintain inspection record and copies certified by the inspection
authority should be supplied as part of documents by the vendor.
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6.6 Annex-6: Definitions of terms Anchor or Tieback – is a metallic or refractory device that holds the refractory or insulation in place.
Back up Layer – is any refractory layer behind the hot face layer.
Casing – is a metal plate used to enclose the reactor
Castable – is an insulating concrete poured or gunned in place to form a rigid refractory shape or
structure
Ceramic Fibre – is a fibrous refractory insulation composed primarily of silica and alumina.
Applicable forms include blanket, board, module, rigidized blanket, i.e., insulation board, and
vacuum-formed shapes.
Corrosion Allowance - is the additional material thickness added to allow for material loss during
the design life of the component. It is the corrosion rate times the design life, expressed in mm
(inches).
Corrosion rate – is the reduction in the material thickness due to the chemical attack from the
process fluid or flue gas or both, expressed in mm per year (inches per year). Minim um Corrosion
allowance shall be (a) For Carbon Steel - 1.5 mm and (b) For Stainless Steel – NIL
Damper/valve – is a device for introducing a variable resistance for regulating volumetric flow of
flue gas or air
Butterfly Damper – is a type of damper consisting of a single blade pivoted about its centre
Louver Damper – is a type of damper consisting of several blades each pivoted about its centre
and linked together for simultaneous operation
Duct – is a conduit for air or flue gas flow
Erosion – is the reduction in the material thickness due to mechanical attack from a fluid.
Forced Draft – is a process in which the air is supplied under positive pressure by a fan or other
mechanical means
Hot Face Temperature – is the temperature of the refractory surface in contact with the syn–gas
or heated combustion air. The hot face temperature is used to determine refractory or insulation
thickness and heat transmitted. The design temperature is used to specify the service temperature
limit of the refractory materials
Induced Draft – Uses a fan to remove produced gas and maintain a negative pressure in the
reactor to induce combustion air without a forced draft fan
Manifold – is a chamber for the collection and distribution of fluid to or from multiple parallel flow
paths
Metal Fiber-Reinforcement – is Stainless steel needles added to castable for improved toughness and
durability
Monolithic Lining – is a single component lining system
Mortar – is a refractory material preparation used for laying and bonding refractory bricks
Multi-Component – is a refractory system consisting of two or more layers of different refractory
types for example, castable and ceramic fiber
Multi-Layer Lining – is a refractory system consisting of two or more layers of the same refractory
type
Protective Coating – is a corrosion resistant material applied to a metal surface (e.g., on casing plates
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behind porous refractory materials) to protect against sulfur in the flue gases
Setting or Refractory Setting – is the heater casing, brickwork, refractory and insulation, including the
tiebacks or anchors
Stack: A vertical conduit used to discharge waste gas to the atmosphere
Syn-Gas or Producer Gas – is the gaseous product containing CO, H2, CH4, CO2 & N2
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6.7 Annex-7: Case studies There are more than 272 operating
gasification plants worldwide with 686
gasifiers. There are currently 74 plants
under construction worldwide, which
have total 238 gasifiers producing 83
MWth. 33 gasification plants are located
in the United States. Currently, China has
the largest number of gasification
plants. Worldwide gasification capacity is
expected to grow significantly by
2018, with the primary growth occurring
in Asia (primarily China, India, South
Korea, and Mongolia)16.
The details of few biomass gasification plants with advanced technologies are summarized below17.
Case -1 : Bioliq
Developing Companies/Institutions
Forschungszentrum Karlsruhe (FZK)/Karlsruhe Institut für Technologie (KIT), Lurgi GmbH
Owner FZK/Lurgi
Gasification Technology High temperature entrained-flow gasification of pyrolysis oil, which is produced in a Lurgi fast pyrolysis process to"Biosyncrude"
Primary Purpose Biomass to Fischer-Tropsch fuels, methanol, chemicals, SNG
Technology Status Demonstration gasifier completed in 2012
Power Throughput 2 MWth of demonstration unit
Location Karlsruhe, Germany
Brief Description In a joint development between Forschungszentrum Karslruhe (FZK) and Lurgi GmbH, a combined pyrolysis/entrained-flow gasification system has been developed. The idea is to produce a pyrolysis oil (name “BioSynCrude” by Lurgi) on a decentralised location upon which the energy density is increased, where after it is transported to a centralised entrained flow gasification plant where it is gasified. Entrained-flow gasification is generally favoured by scale so this is a suitable approach to save on transportation cost and energy.
Case -2 : Bioneer
Developing Companies/Institutions
Technical Research Centre of Finland (VTT), Bioneer Oy
Owner Various
Gasification Technology Updraft fixed bed
Primary Purpose Lime kilns, district heating
16 http://www.gasification-syngas.org/resources/the-gasification-industry/ 17 Rapport 234 – Biomass Gasifier Database - Jens Hansson, Andreas Leveau och Christian Hulteberg, Nordlight AB
August 2011 Rapport SGC 234 • 1102-7371 • ISRN SGC (Svenskt Gastekniskt Center)
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 50 of 52
Technology Status Commercial system in operation but no new development
Power Throughput 4-6 MWth input
Location Kankaanpää, Kempele, Kauhajoki, Hämeenlinna, Parkano, Kitee, Jalasjärvi (Finland) and Lit and Vilhelmina (Sweden)
Brief Description The development of an updraft gasifier for peat and wood was initiated at the Technical Research Centre of Finland (VTT) in the late 1970s. The idea was to replace imported fuels with domestic. The Finnish Ministry of Trade supported and sponsored the venture. During the mid 80s, the VTT conducted extensive tests with a variety of feedstocks, including wood, forest wastes, peat, straw, RDF pellet etc. at a pilot plant in Kankaanpää. Since 1984 Bioneer Oy manufactured and sold the gasifiers under the trademark Bioneer. Eight commercial plants were then built during the 80s, in Finland and Sweden. Yet another commercial plant was built in 1996 in Finland.
Case -3 : Harboøre
Developing Companies/Institutions
Babcock and Wilcox Vølund
Owner Babcock and Wilcox Vølund
Gasification Technology Updraft counter-current moving bed gasifier
Primary Purpose CHP
Technology Status Commercial
Power Throughput 3.5 MWth input
Location Harboøre, Denmark
Brief Description Danish boiler manufacturer Ansaldo Vølund Energy built the Harboøre updraft countercurrent moving bed gasifier between 1988 and 1992. The updraft technology was chosen to include the drying step in the unit, and to achieve a high carbon conversion. Other benefit would include high heating value of the product gas and low dust content. The plant was actually constructed for district heating only at first but was optimized for gasification in 1997. Gas cleaning, wastewater cleaning and gas engines were installed during 1997-2002, thereafter-commercial operation commenced. The technology has also been transferred to a plant in Yamagata in Japan, which began operation in 2007. Since then two more Japanese plants have been added to the list.
Case -4 : Lahti
Developing Companies/Institutions
Foster-Wheeler
Owner Lahden Lämpäpövoima Oy
Gasification Technology Atmospheric CFB
Primary Purpose Heat and power to the local community, auxiliary system to the conventional boiler
Technology Status Commercial
Power Throughput 60 MWth input
Location Kymijärvi Power Plant, Lahti, Finland
Brief Description The FW CFB gasification technology was developed in the early 1980s, the driver for development being very high oil prices. The first commercial-scale CFB gasifiers, using 17 to 35 MW of dry waste wood as feedstock, were delivered for the pulp and paper industry in the mid 1980s, enabling oil to be substituted in the lime kiln process. During the 1990s, a gasification process producing raw gas from a variety of biomass and recycled fuels to be co-combusted in a pulverized coal (PC) boiler was
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 51 of 52
developed. Additionally, three commercial scale atmospheric CFB/bubbling fluidized-bed (BFB) gasifiers with fuel inputs from 40 to 70 MW were supplied during the years 1997-2003. In 1997-1998, a 60 MWth atmospheric Foster Wheeler CFB biomass gasifier was installed at the 200 MWth fossil fuel fired Kymijärvi power station, without any significant commissioning problems. The product gas is used in the boiler and the gasifier is flexible when it comes to type of fuel and with an availability of >95%.
Case -5 : Nexterra
Developing Companies/Institutions
Nexterra Systems Corp. (Vancouver, Canada)
Owner varies
Gasification Technology Updraft fixed bed gasifier
Primary Purpose Heat and Power
Technology Status Commercial
Power Throughput 30 MWth or 10 MWel (for cogeneration) output
Location Several plants in North America, including Oak Ridge (Tennessee, USA), Vancouver (British Columbia), Columbia (North Carolina, USA), Prince George (British Columbia), Victoria (British Columbia), New Westminster (British Columbia), Heffley Creek Plywood Mill near Kamloops (British Columbia), in Canada if not otherwise stated
Brief Description Nexterra develop, manufacture and deliver advanced gasification systems that enable customers to self-generate heat and power at industrial and institutional facilities using waste fuels. The technology is claimed to be based on a new generation of gasification technology suitable for “inside-the-fence” thermal and cogeneration applications. Nexterra has proven gasification solutions available for the forest industry, institutional (e.g. universities, hospitals, government facilities) and power generation where locally sourced wood waste can be found. Future applications include systems that operate on coal and other low cost fuels
Case -6 : TRI Steam Reformer
Developing Companies/Institutions
TRI (ThermoChem Recovery International, Inc.)
Owner TRI (licenses parts of the technology from MTCI)
Gasification Technology Indirect bubbling fluidized bed gasifier with steam reformer followed by partial oxidation of char – customizable H2/CO ratio
Primary Purpose Production of biofuels, biochemicals, power, heat, steam
Technology Status Commercial operation of black liquor gasifier and further development of biomass gasification in pilot
Power Throughput ~20 MWth black liquor (100 tpd)
Location Commercial plant in Ontario, Canada. Pilot plant at in Durham, NC, USA. Two biomass gasification demonstration plants in final engineering phase to be constructed in Wisconsin, USA (100 and 200 MWth input, respectively)
Brief Description MTCI/ThermoChem are the original developers of the technology and TRI was started with a license from them in 1996. Since then TRI have made many modifications and further development and have integrated the gasifier with a steam reformer, which they called ‘TRI Steam Reformer’. The Maryland-based (USA) TRI has a commercial black liquor gasification plant running in Ontario, Canada. There is currently research carried out to perform biomass gasification in their pilot plant in North Carolina. Two new biomass gasification plants with a thermal input of
Client Name UNIDO DESL Project No. 9A0000005647
Project Name Policy advisory services in Biomass gasification technology in Pakistan Version 2
Report Title Minimum Quality Standards for Biomass Gasification Plants Page 52 of 52
~100 MWth and 200 MWth, respectively are in the final engineering phase. These will be used to gasify dry forest residuals for the production of FT liquids. The current system targets 250-2000 tpd of feed but there are plans to develop the technology for the 5-250 tpd range as well. More trials using other feedstock will increase the flexibility of the system.
Case -7 : Värö
Developing Companies/Institutions
Götaverken, Tampella, Kvaerner, Metso Power
Owner Metso Power
Gasification Technology Atmospheric circulating fluid bed
Primary Purpose Generation of syngas to be burned in the lime kiln
Technology Status Commercial operation
Power Throughput 35 MWth input
Location Södra Cell Värö Pulp Mill, Sweden
Brief Description The Värö gasifier was installed in 1987 at the Södra Cell Pulp Mill In southwestern Sweden. It was designed by Götaverken in Göteborg, who had experience from atmospheric CFB gasification. Due to low oil prices during the early 1990’s, the gasifier was not operating. Tampella Power and Vattenfall founded the company Enviropower in 1992, which was later bought by Metso Power. New development began in 2002, with the primary purposes to supply heat to the limekiln and generate power. Waste gasification, fuel drying and new technologies for gas cleaning were/are also tested. The gasifier now has a role in the lime cycle of the pulping process and has over 90 000 hours of operating time
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