Environmental Assessment of Coal Gasification:
IERL-RTP
by
William J. Rhodes
Program Manager, Synthetic Fuels
and
Thomas W. Petrie
Project Officer, Synthetic Fuels
Industrial Environmental Research Laboratory
Office of Energy, Minerals and Industry
Environmental Protection Agency
Research Triangle Park, North Carolina 27711
This report.has been reviewed by the Industrial Environmental Research
Lab-RTP and approved for distribution within the Agency. Mention of
trade names or commercial products does not constitute endorsement
or recommendation for use.
March 1978
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1.0 INTRODUCTION
The United States Environmental Protection Agency has initiated
a comprehensive program to evaluate the environmental impacts of processes
capable of producing synthetic fuels from coal. This program is being
directed by the Fuel Process Branch of the Energy Assessment and Control
Division (EACD) of the Industrial Environmental Research Laboratory at
Research Triangle Park, North Carolina (IERL-RTP). Technologies being
assessed include low/medium-Btu gasification, high-Btu gasification and
liquefaction. The purpose of this document is to summarize the current
status and results of the low/medium-Btu and high-Btu gasification
segments of the program.
1.1 BACKGROUND
The United States has been fortunate in the past to possess
large reserves of the three major fossil-fuel energy sources: natural
gas, petroleum and coal. However, in recent years the nation's energy
picture has changed drastically due to increased fuels consumption leading
to increasingly severe shortages of domestic oil and natural gas and
very rapid escalations in the prices of imported oil and gas. Because
of these circumstances, there has been growing interest by government
and industry in the technologies used to produce "clean burning" gaseous
and liquid fuels from coal. The EPA'5 Synthetic Fuels Program is aimed
at ensuring that this country's synthetic fuel industry will be developed
in an environmentally acceptable fashion.
1.2 PROGRAM OBJECTIVES AND APPROACH
The primary objectives of IERL-RTP's Synthetic Fuels
Program are:
0 To define the environmental effects of synthetic fuel
technologies with respect to their multimedia discharge
streams and to assess their health and ecological effects,
0 To define control technology needs for an environmentally
sound synthetic fuel industry.
In order to achieve these program objectives, an assessment approach has
been adopted which involves work in the following six major areas:
0 Current Process technology Background
0 Environmental Data Acquisition
0 Environmental Objectives Development
* Current Environmental Background
0 Control Technology Assessment
0 Environmental Alternatives Analysis.
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The interrelationships between these areas are shown in Figure 1. Some
of the. information will be obtained from other EPA laboratories and
other researchers especially in health and ecological effects. The
following paragraphs briefly summarize the scope of the six areas.
Work in the Current Process Technology Background area involves
two major activities: conducting an information survey of literature
and industry sources; and performing an engineering analysis of the
available data. This analysis seeks to identify 1) which aspects of the
technology are most important and need further study, and 2) what
information is missing or incomplete.
The purpose of the Environmental Data Acquisition is to fill
the data gaps identified by the engineering analysis effort. This
information may be obtained from testing at commercial or pilot plant
facilities or by conducting laboratory experiments. These data acqui-
sition activities may also be used to verify data reported by industry
or in the literature.
After a technology's emission sources (i.e., its potential
problem areas) have been identified, the next step in an environmental
assessment program is determining which sources need to be controlled
and to what levels. To answer these questions, environmental goals must
be developed. These goals comprise the results of the Environmental
Objectives Development and may be based on:
0 best control technology
0 existing standards
9 estimated permissible concentrations
0 natural background pollutant levels
0 preventing significant deterioration
0 minimum acute toxicity.
Background data required in the development of environmental goals
include existing standards and ambient pollutant levels. Obtaining this
information is the purpose of the Current Environmental Background task.
These first four areas should define a technology's pollutant
emission sources which may require control and control goals for those
sources. Work in Control Technology Assessment involves identifying
applicable control techniques and assessing such factors as their control
effectiveness, costs and energy requirements. If control techniques are
not available,, control technology development will precede the assessment
activities.
Determining the best control option(s) for emission sources
and the: best set(s) of control options for a given plant is the aim of
the Environmental Alternatives Analysis task. This will be accomplished
by use of Source Analysis Models, which compare the emissions from a
plant employing a set of control options to the environmental goals.
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CURRENT PROCESS TECH
NOIOGV BACKGROUND
PROCESS INFORMATION
SCHEDULES
STATUS
(HER STUOX
i
to
REGULATOR*
REQUIREMENTS
CURRENT ENVIRONMENTAL
IACKGROUNO
rOIENIIAiraiLUIANTS
AND IMP ACTS IN All
UCOIA
OOSE/REStONSE OAIA
FED/STATE sios. CRITERIA
TRANSPORT MODUS
A SUMMARIZE INDUSTR*
RELATED OCCUTAIIONAL
HEAL1H/EPIDEMIDLOGICAL
LITERATURE
ENVIRONMENTAL ENGINEERING
ENVIRONMENTAL SCIENCES
IECUNOLOG« IRAKSFER
(NVIRDNMCNIAL DATA ACQUISITION
EXISTING OAIA FOR EACH PROCESS
IDENTIFY SAMPLING AND ANALYTI-
CAL TECHNIQUES INCLUDING
IIOASSA»S
TEST PROGRAM DEVELOPMENT
COMPREHENSIVE WASTE STRIAM
CHARACTERIZATION (LEVELS I. II.
Ill)
INPUT OUTPUT MATERIALS
CHARACTERIZATION
CONTROL ASSAVS
ENVIRONMENTAL OUECIIVES
DEVELOPMENT
ESTAILISH PERMISSIBLE
MEDIA CONC. FOR CONTROL
DEVELOPMENT GUIDANCE
DEFINE DECISION CRITERIA
FOR PRIORITIZING SOURCES.
PROBLEMS
DEFINE EMISSION COALS
PRIORITIZE POLLUTANTS
NONPOLLUIANT IMPACT
GOALS
BIOASSAV CRITERIA
ENVIRONMENTAL SCIENCES RIO
HEALTH/ECOLOGICAL EFFECTS
RESfARCH
TRANSPORT/I HANSFORMAIION
RESEARCH
CONTROL TECHNOLOGY
DEVELOPMENT
ENGINEERING ANALYSIS
BASIC AND APPLIED PROCESSES
DEVELOPMENT
SPECIFIC PROCESS DEVELOP
MEN! AND EVALUATION
CONTROL TECHNOLOGY ASSESSMENT
CONTROL SYSTEM AND DISPOSAL
OPTION INFORMATION ANO DE-
SIGN PRINCIPLE
CONTROL PROCESS POLLUTION
ANO IMPACTS
PROCESS ENGINEERING POLLUT
ANT/COST SENSITIVITY STUDIES
ACCIDENTAL HELCASE. MALFUNC-
TION. TRANSIENT OPERATION
STUDIES
FIELD TESTING IN RELATED
APPLICATIONS
DEFINE BEST CONTROL TECH-
NIQUE FOR EACH GOAL
POLLUTANT CONTROL SYSTEMS
STUDIES
CONTROL TECHNOLOGY RIO
PLANS AND COALS
ENVIRONMENTAL ALTERNATIVES ANALYSES
SELECT ANO APPLY
ASSESSMENT ALTERNATIVES
ALTERNATIVE SETS OF MULTI-
MEDIA ENVIRONMENTAL GOALS
MEG'SI
BIST TECHNOLOGY
EXISTING AMBIENT SIOS
ESTIMATED PERMISSIBLE
CONC.
NATURAL BACKGROUND
(ELIMINATION OF DISCHARGE!
SIGNIFICANT DETERIORATION
MINIMUM ACUTE IDXICIIY
EFFLUENI
-i
OUANIIF IEO CONTROL RID NEEDS
QUANTIFIED CONTROL ALTERNATIVES
OUANIIFIEO MEDIA DEGRADATION
ALTERNATIVES
OUANIIF IEO NONPOllUIANI Eft ECU
ANO SUING CRIKRIA ALTERNATIVES
DEFINED RESEARCH OA1A BASE f OR
STANDARDS
ENVIRONUENfAl (NCRG
TECHNOLOGY TRANSFER
MEDIA OEC8AOAIION AND
HEALTH/ECOLOGICAL
IMP ACTS ANALYSIS
AIH.KAIEH. ANOIANO
DUALITY
0 INCREASED SICKNESS
Ada DEATHS
ECOLOGY RELATED
ttllCli
MATERIAL RELATED
EFFECTS
auANiiFiEOEFFECis
AlIERNAIIVES
,.-... . .. .. Figure 1
iEnvironmental Assessment/Control Technology Development Diagram
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Consideration must be given to the relative degree of hazard of the
various pollutants and to cost vs. benefit of controlling the.pollutants.
The results of the Synthetic Fuels Program will be communicated
in a series of information, transfer documents and used as IERL-RTP input
to standards setting and regulatory functions. In order to accomplish
the goals of the program, contracts have been signed to perform work in
the six areas. Radian Corporation is EPA's prime contractor for the
low/medium-Btu gasification program, while TRW, Inc. is the prime contractor
for the high-Btu gasification program. Table 1 lists the contractors
that are doing work in one or more of the six areas for the Synthetic
Fuels Program.
The sections which follow discuss the coal gasification related
activities of the contractors in the environmental assessment areas.
Sections 2.0 and 3.0 address the process technology background and data
acquisition activities. Since the majority of work to date in the
assessment program has been on these tasks, they have received major
emphasis in this document. Activities in the tasks which develop
environmental goals are discussed in Sections 4.0 and 5.0, while activities
in the tasks dealing with the assessment and analysis of control tech-
niques are discussed in Sections 6.0 and 7.0.
2.0 CURRENT PROCESS TECHNOLOGY BACKGROUND
The current process technology background task is aimed at
gathering and assessing the most current information available for the
processes under consideration. The activities undertaken in developing
the current process technology background include:
0 Technology characterization
0 Selection of processes having a high potential for near-
term commercialization
0 Determination of waste streams
0 Identification of control equipment requirements for
characterizing waste streams.
The results to date of these activities are discussed below. Progress
for low/medium-Btu gasification (Radian Corporation) in this task area
is further along than for high-Btu gasification (TRW, Inc.) because of
rthe earlier start date for thelow/medium-Btu project.
2.1 TECHNOLOGY CHARACTERIZATION
All gasification processes involve partial oxidation of coal.
Where the systemgis "air blown," gas with a low heating value of approx-
imately 5.6 x 10 J/Nm (150 Btu/scf) is produced. "Oxygen blown1'
systems produce gas with a medium heating value of about 13.1 x 10
J/Nm (350 Btu/scf). Medium-Btu gas can be further up-graded to high-
Btu gas (approximate heating value of 35.5 J/Nm or 950 Btu/scf) by
catalytically converting the CO and H2 contained in the gas into CH,.
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Table 1. EPA'S SYNTHETIC FUELS ASSESSMENT PROGRAM ELEMENTS -
PROJECT TITLES, CONTRACTORS, AND EPA PROJECT OFFICERS
Project Title
Contractor
EPA Project Officer
Environmental Assessment
of Low/Medium-Btu
Gasification
(March 1976-March 1979)
Environmental Assessment
of High-Btu Gasification
(April 1977-April 1980)
Environmental Assessment
of Coal Liquefaction
(August 1976-August 1979)
Control Technology for
Products/By-Products
(Sept. 1976-Sept. 1979)
Control Technology for
Converter Output
(January 1977-January 1980)
Waste Stream Disposal
and Utilization
(April 1977-April 1980)
Radian Corporation
8500 Shoal Creek Blvd.
Austin, Texas 78758
(512) 454-4797
(E.G. Cavanaugh/G.C. Page)
TRW, Inc.
1 Space Park
Redondo Beach, CA 90278
(213) 536-1116
(Chuck Murray)
t
Hittman Associates
9190 Red Branch Road
Columbia, MD 21043
(301) 730-7800
(Dwight Emerson)
Catalytic, Inc.
1500 Market Street
Center Square West
Philadelphia, PA 19102
(215) 864-8104
(A.B. Cherry)
Hydrocarbon Research, Inc.
P.O. Box 2391
334 Madison Avenue
Morristown, NJ 07960
(201) 540-0180
(Harold Stotier)
Pullman-Kellogg
Research & Development
Center
16200 Park Row
Industrial Park Terrace
Houston, Texas 77054
(713) 493-0291
(Louis Bostwick)
William J. Rhodes
IERL-RTP
(919) 541-2851
William J. Rhodes
IERL-TRP
(919) 541-2851
William J. Rhodes
IERL-RTP
(919) 541-2851
Chester A. Vogel
IERL-RTP
(919) 541-2134
Chester A. Vogel
IERL-RTP
(919) 541-2134
Chester A. Vogel
IERL-RTP
(919) 541-2134
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Table 1. EPA'S SYNTHETIC FUELS ASSESSMENT PROGRAM ELEMENTS -
PROJECT TITLES, CONTRACTS, AND EPA PROJECT OFFICERS
-...- Continued
Project Title
Contractor
EPA Project Officer
General Support
(April 1976-December 1977)
Cameron Engineers, Inc.
1315 South Clarkson Street
Denver, CO 80210
(303) 777-2525
(Ted Borer)
Acid Gas Cleaning North Carolina State Univ.
Bench Scale Unit Dept. of Chemical
(October 1976-Septemfaer 1981) Engineering
(Grant) Raleigh, NC 27607
(919) 737-2324
(Dr. James Ferrell)
L. David Tamny
IERL-RTP
(919) 541-2709
Thomas W. Petrie
IERL-RTP
(919) 541-2708
Water Treating Bench
Scale Unit
(November 1976-October 1981)
(Grant)
Pollutant Identification
From a Bench Scale Unit
(November 1976-October
1981)
(Grant)
Univ. of North Carolina
Dept. of Environmental
Sciences & Engineering
School' of Public Health
Chapel Hill, NC 27514
(919) 966-1052
(Dr. Philip Singer)
Research Triangle Institute
P.O. Box 12194
Research Triangle Park,
North Carolina 27709
(919) 341-5836)
(Dr. Forest Mixon)
Petrie
Thomas W.
IERL-RTP
(919) 541-2708
Thomas W. Petrie
IERL-RTP
(919) 541-2708
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2.1.1 Low/Medium-Btu Gasification Technology
The production of low/medium-Btu gas involves three basic
operations: coal pretreatment, coal gasification, and gas purification.
The specific processes used to satisfy the requirements of each of these
operations will be determined mainly by 1) the properties of the coal
feedstock, 2) the type of gasifier that is employed, and 3) the economic
factors associated with each site-specific application. A number of
processes and their interrelationships are depicted in Figure 2.
2.1.2 High-Btu Gasification Technology
High-Btu gasification involves the same basic operations that
are used in the production of medium-Btu gas plus additional processes
to produce a product gas having a high heating value. The additional
processes are shift conversion (to adjust the EL:CO ratio to 3:1) and
methanation (to convert CO and H_ to CH,). Quenching for tar and oil
removal and stringent acid gas removal are required in high-Btu gasi-
fication systems to meet product specifications and protect the metha-
nation catalyst from being poisoned.
2.2 PROCESS ASSESSMENT
An important aspect of the current process technology background
effort is the identification of processes which have a high potential
for commercialization. Criteria for selecting these processes include:
0 Development status
0 Process cost and energy efficiency
8 Applicability
0 Probability of successful development and application
0 Environmental impact.
The following sections discuss the status, cost, applicability and
environmental impact of gasification technology.
2.2.1 Development Status
The production of low- and medium-Btu gas from coal has been
practiced both in the United. States and overseas for many years. At one
time there were about 11,000 coal gasifiers in use in the U.S. As the
availability of natural gas. increased, the number of operating gasifi-
cation systems declined significantly. There are only a few coal gasi-
fiers now operating in the United States on a commercial basis. However,
in general the development status of low/medium-Btu gasification can be
regarded as commercial.
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COAl tfttIMAIUCHI
COAL OASinCAItON
OA8 PUMFICAIIOM
MOHMOKIUW
C041
VMIMK1I9
0*1
Figure 2
Low/Medium-BTU Coal Gasification Processes
-------
Economic reasons generally favor operation of high-Btu gasifi-
cation systems at high pressures. Of the commercially available processes,
only the Lurgi process operates at high pressure. Development work is
underway on several new high pressure processes which show promise for
having process, economic, and environmental advantages over the Lurgi
process.
Status of Coal Pretreatment Processes
The coal pretreatment processes which may be required in a
gasification plant (either low-, medium-, or high-Btu) include crushing
and grinding, sizing, partial oxidation, pulverization, drying, and/or
briquetting. The specific processes used will be determined by the
properties of the coal feedstock and the type of gasifier employed.
These processes, with the exception of partial oxidation, have been used
for years in the gasification, coal-fired electric utility and charcoal
industries. However, much work (e.g., the Synthane Process) has been
done to develop a reliable partial oxidation process for reducing the
caking tendencies of certain types of coal. Therefore, the development
status of all coal pretreatment processes is regarded as commercially
available.
Status of Gasification Processes
Approximately 70 different gasification processes can be
identified which either have been used commercially in the past or are
currently under development. Twenty-five of the most prominent of these
.gasification processes are shown in Table 2.
Eight of the gasifiers listed in this table are being used to
satisfy some commercial demand for low/medium-Btu gas. These are:
0 Chapman (Wilputte) ° Wellman-Galusha
°'. Foster Wheeler/Stoic0 Wellman Incandescent
0 Koppers-Totzek ° Winkler
0 Lurgi ° Woodall-Duckham/Gas Integrale.
A number of the other gasifiers listed in Table 2 appear to have sig-
nificant commercialization potential. For example, a commercial-scale
Riley-Morgan system has been operated as a development/test unit.
Radian Corporation has compiled a list of 14 gasifiers
which appear to be the most promising candidates for satisfying near-
term commercial needs for low/medium-Btu gas. This list is shown in
Table 3. The considerations which led to Radian's selection of this
group are described in their report Environmental Assessment Data Base
for Low/Medium-Btu Gasification Technology (EPA-600/7-77-125a and b),
issued in November.1977.
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Table 2. STATUS OF U.S. AND FOREIGN LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Number of Gasifiers Currently Operating (No. of Gaslflers Built)
Gasifler
Lurgl
Wellman-Galusha
Woodall-Duckham/
Gas Integrale
Koppers-Totzek
Wlnkler
Chapman (Wllputte)
Rlley Morgan
Wellman Incandescent
BGC/Lurgi Slagging
g Bi-Cas
Foster Wheeler/Stoic
Pressurized Hellman-
Galusha (MERC)
GFERC Slagging
Texaco
BCR Low-Btu
Combustion Engineering
Licensor /Developer
Lurgl Mineral tatechnlk GmbH
McDowell Wellman Engineering Co.
Woodall-Dickham (USA) Ltd.
Koppers Company, Inc.
Davy Powergaa
Hllputte Corp.
Rlley Stoker Corp.
Applied Technology Corp.
British Gas Corp. and Lurgl
Mlneraloltechnlk GmbH
Bituminous Coal Research, Inc.
Foster Hheeler/Stolc Corp.
DOE
DOE
Texaco Development Corp.
Bituminous Coal Research, Inc.
Combustion Engineering Corp.
Low-Btu Gaa Medlum-Btu Gas
5 (39)
8 (150)
(72)**
-
(23)**
2 (12)
1
(2*)**
1
1
1*(2)**
1*
1*
-
1*
1*
Synthesis Gas Location
(22) Foreign
US/Foreign
(8)** Foreign
(39)** Foreign
6(14) Foreign
US
US
US/Foreign
Foreign
US
US
US
US
1* US
US
US
Scale
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial/
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
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Table 2. STATUS OF U.S. AND FOREIGN LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Continued
Number of Gasifiers Currently Operating (No. of Gasiflera Built)
Gaslfler
Hygaa
Synthane
C°2
Foster Wheeler
Babcock & Wilcox
U-Cas
Westinghouse
Coalex
COCAS
Licensor /Developer
Institute of Gas Technology
DOE
DOE
Foster Wheeler Energy Corp.
The Babcock & Wilcox Co.
Institute of Gas Technology
Phillips Petroleum Corp.
Westlnghouse Electric Corp.
Inex Resources, Inc.
COCAS Development Co.
Low-Btu Gas Medlum-Btu Gas
1
1
1
1
1
1
1
1
(1*)
1
Synthesis Gas Location
US
US
US
US
US
US
US
US
US
Scale
Demonstration
(High-Btu)
Demonstration
(Hlgh-Btu)
Demonstration
(Hlgh-Btu)
Pilot
Pilot
Eftxlbt 400 Ib/hr
.(181 kg/hr)coal
Pilot
Pilot
Demonstration
(High-Btu)
* Under construction.
Demonstration scale Indicates 2000 to 10,000 Ib/hr. (907 to 4536 kg/hr) coal feed.
Pilot scale indicates 400 to 1500 Ib/hr (181 to 680 kg/hr) coal feed.
** Undetermined number overseas currently in operation.
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Table '3. PROMISING LOW/MEDIUH-BTU GASIFICATION SYSTEMS
First Group1
Second Group1
Third Group3
Wellman-Galusha
Lurgi
Woodall Duckham/
Gas Integrals
Koppers-Totzek
Winkler
Wellman Incandescent
Foster Wheeler/Stoic
Chapman (Wilputte)
Riley Morgan
Pressurized Wellman-
Galusha (MERC)
BGC/Lurgi Slagging
Gasifier
Texaco
I
Bi-Gas
Coalex
Commercially available; significant number of units currently
operating in the U.S. or in foreign countries.
Commercially demonstrated in limited applications.
Commercial or demonstration-scale units operating or being constructed;
technology is promising and should be monitored.
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In their environmental assessment of high-Btu gasification
technology, TRW, Inc. has selected nine high pressure gasification
systems for detailed analysis. These processses are:
8 Hygas ° Texaco
0 Bi-Gas ° C02 Acceptor
0 COGAS * Self-aggomerating ash
0 Hydrane ° Lurgi.
0 Synthane
These processes are in various stages of incomplete development.
The exception is the Lurgi process which has been used commercially in
foreign countries to supply medium-Btu gas for a variety of industrial
users. With the addition of shift conversion and methanation, the Lurgi
medium-Btu process is considered a proven high-Btu gasification process.
Status of Gas Purification Processes
The purpose of the gas purification operation is to remove
undesirable constituents from the product gas. Purification may include:
0 particulate removal
9 gas quenching and cooling
0 acid gas removal.
The intended end-use of the product gas determines which of these puri-
fication steps to use. For example, for on-site combustion of low-Btu
gas produced from a low sulfur coal, only particulate removal may be
required. For the production of high-Btu gas, all three purification
steps are required.
Removal of particulates from gasifier product gas is generally
accomplished through the use of dry collectors such as cyclones or
electrostatic precipitators and/or the use of water or oil scrubbers.
These processes are normally employed when tars and oils as well as
other impurities such as ammonia must be removed from the product gas.
The use of water or oil scrubbers will also cool the product gas. Other
candidate cooling processes include waste heat boilers and air or
'water cooled heat exchangers.
Acid gas removal processes remove compounds such as ELS,
COS, CS2, mercaptans, HCN and CQ~ from the product gas. In theory,
either nigh (>420°K or 300°F) or low temperature acid gas removal
processes can be used. High temperature processes utilize iron oxide,
dolomites, molten metals, etc. as sorbents. They should yield higher
efficiencies, but are only in the development stage. Thus, most
existing and proposed gasification plants use low temperature processes.'
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A variety of low temperature acid gas removal processes are
commercially available. Most were developed for use in the natural gas,
refinery and chemical process industries. There do not appear to be
any insurmountable problems associated with their use in coal gasification
plants. Radian has identified 14 acid gas removal processes as
the most likely candidates for near-term commercial use in coal gasification
systems:
0 Physical Solvent Processes
- Rectisol - Estasolvan
- Selexol - Fluor Solvent
- Purisol
0 Chemical Solvent Processes
- MEA - DIPA
- MDEA - DGA
- DEA - Benfield
0 Combination Chemical/Physical Solvent Processes
- Amisol - Sulfinol
8 Direct Conversion Process
- Stretford
2.2.2 Cost and Applicability
The potential uses for coal gasification technology are to
produce:
0 High-Btu or substitute natural gas
0 Low or medium-Btu combustion fuel
* .Low or medium-Btu synthesis or reducing gas.
The economics and applicability of gasification technology for some of
these uses are uncertain at this time. An assessment of current technolpgy
provides insight to this uncertainty.
Substitute Natural Gas - In view of the decreasing availability
of natural gas, one option for coal utilization is in the production of
substitute natural gas (SNG). Several consortiums of natural gas suppliers
and distributors.are considering constructing large scale substitute
natural gas plants using available technology. Actual construction
activities, however, are slow in getting underway.
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The major impediments to the construction of these plants
involve cost. First, investments which would seriously tax the finan-
cial resources of the consortium members are required in most cases.
For example, a 7 million m (250 million scf) per day plant would require
a capital investment on the order of $1.3-1.5 billion. Second, SNG
costs are predicted to be on the order of $4-5 per thousand cubic feet
(28 cubic meters) as compared to current intrastate prices of about $2
per thousand cubic feet (28 cubic meters) for new natural gas. These
higher product costs, combined with uncertainties in future natural gas
price regulations, have made financial institutions wary of lending the
large sums of money required to build substitute natural, gas plants.
Moreover, the actual plant and SNG vs. natural gas costs are still
controversial.
Given these cost impediments, there appear to be some real-
istic concerns about the applicability of current coal gasification
technology to the production of SNG. Nonetheless, an. analysis of the
advantages and disadvantages of SNG production seems to indicate that
there is a place for coal gasification in the supply of gas for resi-
dential heating (water, space heating, cooking). A recent American Gas
Association study (Ref. 1) concludes that SNG may have both energy
efficiency and cost advantages over electrification (the most viable
alternative).
Although this conclusion was reached by an industry group with
strong interests in promoting SNG production, it is certainly not totally
unrealistic. For example, using conventional technologies in the residential
end-use sector, the AGA data indicates the use of SNG has an overall
energy efficiency of 36% and costs the consumer about $7 per useful
million Btu (1.055 billion joules). The AGA data for coal electrification
with advanced technology (heat pumps) indicates overall energy efficiencies
ranging from 35 to 53% and costs ranging from $7 to $10.5 per useful
nfri.i-t.nn Btu (1.055 billion joules) depending on location within the U.S.
Thus, depending on location, 1) electrification appears to be slightly
favored based on energy usage, but 2) SNG is generally cheaper than
electrification. Considering that electric heat pumps are more expen-
sive and more failure-prone than gas furnaces, the balance may shift to
SNG production as opposed to electrification for residential use.
Combustion Fuel - A second use for coal gasification is in the
production of combustion fuel, either in large scale facilities for use
by the electric utility industry or in small facilities for industrial
applications. The cost and applicability of low/medium-Btu gasification
for the production of electrical generation fuel must be compared with
the most viable alternative. Direct combustion of coal and the use of
flue gas desulfurization (FGD) appears to be the most viable alternative.
A coal fired power plant using FGD will produce electricity with a
busbar cost of about 3.5-4.0 cents per kW-hr. A power plant using
gasified coal will produce electricity costing about 5.0 to 5.5 cents"
per kW-hr. Thus, it appears that, for large scale electrical generation
facilities where FGD is practical, direct combustion of coal with FGD
has economic advantages over combustion of gasified coal.
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A more likely possibility for the future production of elec-
tricity is gasification coupled with a combined, cycle generating system.
In such systems, gas from coal is produced at a high pressure, combusted
and expanded through a gas turbine. The turbine exhaust is then utilized
in a conventional steam boiler. The economics of combined cycle operation
may be better than conventional direct combustion because higher efficiencies
(46% as compared to 38% for conventional systems) can be obtained.
However, at this time the high temperature gas turbines needed to achieve
these high efficiency levels are not commercially available.
It now appears that there is significant potential for the use
of coal gasification to produce industrial fuel. There are many indus-
tries which require a gaseous fuel. These industries have low priority
for receiving natural gas and thus will be increasingly sensitive to
natural gas curtailments~ Consequently, they will be increasingly
amenable to the use of coal gasification.
The cost of supplying low/medium-Btu fuel gas to this class of
users will be highly dependent on site specific factors such as coal
cost, coal availability and gas purity requirements. However, in applications
where the gasifier output stream can be utilized without expensive gas
clean-up, costs of $2 to $3 per million Btu (1.055 billion joules) are
anticipated. Gas clean-up (acid gas removal) would boost this cost by
about $1 per million Btu. Although this cost is high compared to current
natural gas prices, there may be overriding factors to consider. For
example, the higher cost of gas from coal gasification may be recouped
by not having plant capacity idle during natural gas curtailments.
Synthesis or Reducing Gas - The production of synthesis or
reducing gas is a third option for utilizing coal via coal gasification.
Synthesis gas finds use in the production of ammonia, methanol, alde-
hydes, and oxo-alcohols. Hydrogen-rich reducing gases are widely used
in hydrodesulfurization and hydrocracking processes in the refining
industry. Other applications for reducing gases include various processes
in the metals industry and in the regeneration sections of some flue gas
desulfurization processes.
While several coal-based ammonia plants are currently operating
overseas, there does not appear to be significant interest in coal
gasification to produce synthesis or reducing gas in the U.S. This is
due principally to the fact that synthesis and reducing gases are currently
derived from natural gas or liquid fuel feedstocks which are much cheaper
than gas produced from coal. However, this situation may change in the
future as alternative gaseous and liquid feedstocks become more scarce.
2.2.3 Environmental Impact of Coal Gasification
The multimedia emissions from coal gasification operations
range from conventional pollution problems such as coal dust emissions
to such ill-defined problems as fugitive emissions. As part of Radian's
engineering analysis of low/medium-Btu gasification technology, a list
of environmental assessment data requirements was compiled. These are
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summarized in Table 4. The following paragraphs briefly discuss some of
the more significant problems which are highlighted in the table.
Problems with emissions from coal preparation processes
generally seem solvable with available technology. Wastes from coal
storage, handling, size reduction, and classification processes also can
be managed using available techniques for controlling coal dust emissions,
disposing of mineral wastes, and handling runoff waters from storage
piles. However, opportunities for the development of less costly or, in
some cases, more efficient controls clearly exist.
Air emissions occur from coal dryers, briquetting and partial
oxidation processes. Control of them may be difficult because volatile
hydrocarbons can. be liberated as coal is heated. The exact character of
these materials has not been determined as far as their potential health
and ecological effects are concerned. Hence, the limit to which they
must be controlled and the adequacy of available control technology have
not been determined.
The coal gasification operation appears to be the most serious
source of potential gasification system pollution problems. For all
systems, the feeding of coal and the withdrawal of ash provide oppor-
tunities for the escape of coal or ash dust and hydrocarbons. Since
they are products of the thermal processing of coal, they must be
considered to be potentially toxic. These problems are similar for all
gasifiers even though emissions from some types of equipment may consist
largely of coal or ash dust. Also, it is certain that gasifiers and
associated equipment will be sources of fugitive leaks from valves,
flanges, and fittings. This leakage, unless controlled to adequate
levels, can be hazardous.
The gas purification processes also appear to present difficult
control problems. The gas cooling steps will produce water contaminated
with suspended and dissolved organics and inorganics, many of which will
be toxic. The ability of conventional wastewater treatment processes
(e.g., API separators, sour water strippers, and biological oxidation) to
effectively treat this waste stream has not been demonstrated.
Except for the Stretford process,, all of the acid gas removal
processes previously identified will produce a H2S-rich vent stream
which needs to be controlled. In most cases this stream will be sent to
a sulfur recovery process (Glaus or Stretford). The tail gases from
these sulfur recovery processes may require further treatment, depending
upon the tail gas composition. Other waste streams from these acid gas
and sulfur recovery processes will include liquid blowdown streams and
sulfur. The sulfur can normally be sold as a by-product. However, the
blowdown streams will contain reactant degradation products and may
contain dissolved organics including phenols and dissolved inorganics
such as HCN and H_S. Effective control/disposal techniques for the
blowdown streams have not been demonstrated.
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Table I*. DISCHARGES FROM LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Operation
Discharge stream
source
Discharge
streams
Description
Remarks
Coal Pretreatment
Storage, handling and
crushing/sizing
Dust emissions
Water runoff
Solid wastes
from crushing
and sizing
Coal drying, partial
oxidation and brlquettlng
Vent gases
Coal Gasification
Coal feeding device
Vent gases
The air emission from coal storage
piles, crushing/sizing and handling
will consist primarily of coal dust.
The amount of these emissions will
vary from site to site depending on
wind velocities and coal size.
The amount of data on dissolved and
suspended organlcs and inorganics In
runoff water produced for coal stor-
age piles and dust control or
supresslon processes are minimal.
This stream consists of rock and
mineral matter rejected from crush-
Ing and sizing coal. There is
little data concerning the trace
components in this stream and the
potential of these components to
contaminate surface and ground-
waters is not known.
These emissions will contain coal
dust and combustion gases along
with a variety of organic compounds
liberated as a result of coal
devolatlzation reactions. There
are currently little data on the
characteristics of these organic
species.
There are currently no data on the
characteristics of these gases.
These vent gases may contain
hazardous species found in the
raw product gas exiting the gasifier.
Asphalt and various polymers have been
used to control dust emissions from coal
storage piles. Water sprays and enclosed
equipment have been used to control coal
handling emissions. Enclosures and hoods
have been used for coal crushing/sizing.
Proper runoff water management techniques
have been developed. More data on the
characteristics of this waste water need to
be obtained to determine the need for treating
this effluent.
This waste has been disposed of in landfills.
Leaching data need to be obtained to eval-
uate the potential environmental Impacts
associated with this solid waste.
The organic compounds need to be characterized
to determine whether this discharge stream
needs to be controlled. Afterburners in
addition to participate collection devices
may be required.
Vent gases from coal feeders can represent a
significant environmental and health problem.
Control of these emissions Is required; however,
the characteristics of these gases need to be
determined to Implement an adequate control method.
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Table A. DISCHARGES FROM LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Continued
Operation
Discharge stream
source
Discharge
streams
Description
Remarks
Ash removal device
f Coal gasifier
Vent gases
Spent ash
quench water
Ash or slag
Start-up vent
stream
Fugitive
emissions
There are currently no data on the
characteristics of this discharge
stream. This stream may contain
hazardous species found In the raw
product gas and may require control.
There are limited data on the
discharge stream. This stream will
contain dissolved and suspended
organlcs and Inorganics and will
require control.
There are limited data on the
characteristics of the ash and slag
especially concerning the amount of
unreacted coal, trace elements and
total organics. '
There are currently no data on the
composition of start-up vent stream.
Depending on the coal feedstock,
there may be tar and oil aerosols,
sulfur species, cyanides, etc. in
this stream; therefore,.control of
pollutants generated during start- .
up Is required.
There are no data available on these
emissions. They can be expected to
contain hazardous species that are in
the. raw product gas such as hydrogen
cyanide.
Many sources of contaminated water may be used
for ash quenching. Therefore, volatile organlcs
and inorganics may be released in these vent
gases. Characterization of emissions is needed
to define control technology .elements.
Characterization of this waste stream Is required
to define control technology requirements.
Further treatment of this stream is essential.
Leaching tests need to be done on this solid
waste to determine whether further treatment
is necessary before ultimate disposal. The
organic content of the liquor used to quench
the ash may affect the final disposal of the ash.
This stream can be controlled using a flare to
burn the combustible constituents. The amount
of heavy tars and coal participates in this
stream will affect the performance of the flare.
Problems with tars and coal particles can be
minimized by using charcoal or coke as the
start-up fuel.
These emissions will determine the extent of
workers' exposure to hazardous species and de-
fine the need for continuous area monitoring
of toxic compounds and personnel protection
equipment.
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Table 4. DISCHARGES FROM LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Continued
Operation
Discharge stream
source
Discharge
streams
Description
Remarks
Gas Purification
Particulate removal
Gas quenching and
cooling
o
l
Acid gas removal
Collected There are little data on the
participate characteristics of this solid
matter waste stream. This stream will
contain unreacted carbon, sulfur
species, organica, and trace
elements.
Spent quench There are little data on the corn-
liquor position of this stream; however,
current data indicate that there
are significant quantities of sus-
pended and dissolved organics
(primarily phenols) and inorganics
present In this stream.
Tall gases There are little data on the com-
position of these tall gases. These
gases will contain sulfur species
and hydrocarbons'.
Spent sorbents No data have been reported on these
and reactants streams. These streams will contain
hazardous species such as cyanides,
heavy metals, and organics and will
require further treatment before
disposal.
Characterization of this stream is needed to
determine whether it can be used as a by-
product or whether further treatment Is
necessary before disposal. Current data Indi-
cate that there Is a significant amount of un-
reacted. carbon in this stream and It may be
used as a combustion fuel.
Characterization of this stream will determine
the type of water pollution control techniques
required to treat the spent quench liquor.
These control techniques will vary depending
upon the quantity and composition of this
effluent stream.
These gases are the primary feedstock to the
sulfur recovery and control processes. Trace
constituents such as hydrocarbons, trace elements,
and cyanides will affect the performance of
these sulfur recovery processes.
Characterization of this stream is required
if it is to be treated using on-site pollution
control devices.
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Compared to any low/medium-Btu plant's processes, shift conversion
and methanation are additional processes found in a high-Btu plant.
They have negligible impact on the environmental problems of a gasification
facility. A high-Btu coal gasification facility should have environmental
problems similar to those of a low/medium-Btu facility which uses gas
cooling and acid gas removal processes. However, some differences
should be expected due to different pressures, temperatures, and other
system factors.
3.0 ENVIRONMENTAL DATA ACQUISITION
Environmental assessment data acquisition activities are
directed at acquiring information to fill data gaps such as those identified
in the current process technology background task. They also may verify
data reported in the literature or by industry. The results of the data
acquisition task, in combination with other available data, will help to
identify environmental problems, suggest potential controls for those
problems and project the effectiveness of those controls.
A three phased or three level approach to conducting environmental
assessment testing has been developed. Level 1 is a comprehensive
screening step that provides semi-quantitative data (accurate within a
factor of + 2 or 3) on all influent and effluent streams. Level 2
testing is intended to provide a more detailed analysis of the environmental
problems identified in the Level 1 tests. The third level of testing
involves continuous monitoring of selected priority pollutants identified
in Level 1 or 2 tests.
At this time, the program for environmental data acquisition
has involved site-specific field testing, pollutant identification, and
assay technique development.
3.1 LOW/MEDIUM-BTU GASIFICATION
Radian has tested or arranged for environmental tests to be
conducted at four low/medium-Btu gasification facilities: a) Holston
Army Ammunition Plant, Kingsport, Tennessee; b) Kosovo Kombinat, Pristina,
Yugoslavia; c) Glen-Gery Brick Company, York, Pennsylvania; and d)
University of Minnesota, Duluth, Minnesota. During visits to these and
several other potential environmental testing sites, Radian obtained
grab samples of selected liquid and solid waste streams. IERL-RTP
Level 1 analytical procedures plus some additional analyses were run on
these samples. The results of this analytical work have been summarized
in a report published in December 1977 and entitled Analyses of Grab
Samples from Fixed-Bed Coal Gasification Processes. (EPA-600/7-77-141).
Testing of the Holston plant was completed in September 1977.
This facility has been in operation over 30 years using Chapman (Wilputte)
gasifiers to convert bituminous coal into -low-Btu gas for use as a com-
bustion fuel for industrial furnaces. The objectives of the Holston
test program were:
1) To evaluate Level 1 sampling and analytical procedures
for their applicability to emission streams from low-Btu
gasification processes.
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2) To identify the origin and fate of potentially hazardous
components in a specific goal gasification plant.
3) To obtain control technology data relating to:
- Emissions from coal feed systems
- The effectiveness of a hot cyclone as a parti-
culate removal device.
The results of this test program are being evaluated. A complete report
on the test results should be available in the Spring of 1978.
An environmental test plan for the Kosovo plant has been
developed jointly by the Sudarski Institute (Belgrade, Yugoslavia), EPA,
and Radian as part of a cooperative environmental research program. The
Kosovo complex has been in operation since 1971, using Lurgi gasifiers
to convert lignite from adjacent mines to fuel gas and fertilizer plant
feedstocks. The test plan was completed in September 1977; sampling and
analytical activities at the Kosovo facility started in November 1977.
Radian is also providing on-site technical assistance during the tests.
Preliminary test plans have also been developed for the Glen-
Gery (Wellman-Galusha gasifier) and University of Minnesota (Foster
Wheeler/Stoic gasifier) sites. Testing at Glen-Gery is planned for
early 1978 and at the University of Minnesota for late 1978. Both of
these test programs will be conducted in cooperation with DOE's Gasifiers
in Industry program.
3.2 HIGH-BTU GASIFICATION
TRW, Inc., in planning its high-Btu gasification environmental
assessment program, has placed strong emphasis on environmental sampling
and analysis at selected sites. A list of domestic and foreign in-
stallations suitable for testing has been prepared. Candidate facilities
are being contacted to determine the best possibilities for field testing.
The lack of time since TRW began work on this program has prevented
further progress in data acquisition.
3.3 ENVIRONMENTAL ASSESSMENT TEST PROGRAM GUIDELINES
Radian Corporation is preparing a report which provides guidelines
for the development of environmental test programs. Major emphasis is
placed on the strategy involved in the selection of sample points and
specific sampling and analytical techniques. This material is being
incorporated into a comprehensive document, Guidelines for Preparing
Environmental Test Plans for Coal Gasification Facilities, which will be
available in early 1978.
3.4 GENERAL INVESTIGATIONS
In addition to Radian's and TRW's work in the areas of low/
medium- and high-Btu,gasification the EPA also has programs underway
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to assess on a more general basis the environmental effects of converting
coal into synthetic fuels. Highlights from two of these programs follow.
As noted in Table 1, Research Triangle Institute (RTI) has
initiated a program to characterize the pollutants contained in the
product gas output stream from a laboratory gasifier. The RTI program
will consist of three phases: screening studies, parametric control
evaluations, and reaction kinetics research. The screening studies will
consider, qualitatively, the variety of chemical compounds produced
during gasification reactions. RTI estimates that up to 300 different
compounds may be screened In the course of these tests. In the para-
metric studies, the impact of reactor operation upon product gas pollutant
levels will be examined. Parameters to be considered include coal type,
grind size, pretreatment method, bed depth, temperature, pressure,
steam flow rate, residence time and the presence of catalysts and
additives. Other variables such as bed type (fixed, entrained, fluidized)
and reactor type (batch, semi-batch, plug flow, mixed flow) will also be
considered. The reaction kinetics phase of the research program will be
planned in the coming year.
As part of the effort mentioned in Table 1, Catalytic, Inc. is
working on a Control Assay Development (CAD) program for coal conversion
processes. The objective of the CAD program is to develop and perform
quick screening treatments for streams suspected of containing pollutants
requiring control. Analyses will be made before and after treatment to
evaluate the.effectiveness of the pollutant control method. This
program is expected to shorten the period of time between problem
identification (e.g., through Level 1 testing) and. final recommendations
for control technology application.
4.0 CURRENT ENVIRONMENTAL BACKGROUND
Work in this area is designed to identify and summarize current
regulations applicable to coal gasification processes and to obtain data
on the ambient levels of pollutants expected to be emitted from coal
gasification facilities. Most of the programs mentioned in Table 1
began by establishing the current background relevant to.their area.
For example, Fullman-Kellogg has nearly completed the task of
gathering federal, state, regional and international environmental
standards. The compositions of effluents expected from processes using
current or developing control technologies will be checked against these
environmental- standards.
In another example, researchers at the University of North
Carolina at Chapel Hill collected data on the composition of wastewater
from coal conversion processes. They organized the data according to
major classes of compounds and specified a synthetic wastewater com-
position for ongoing work on biological treatment of coal conversion
wastewater.
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For a third example, Research Triangle Institute has produced,
in addition to work on pollutant identification from a bench scale
gasifier, a draft document entitled, Summary of Key Federal Regulations
and Criteria for Multimedia Environmental Control. It is designed to be
a guide for more detailed analyses of current regulations needed in the
assessment activities they and others are undertaking.
5.0 ENVIRONMENTAL OBJECTIVES DEVELOPMENT
In order to determine if an emission source requires control,
environmental goals must be identified. This is the purpose of environ-
mental objectives development. Environmental goals can be based on
several criteria including existing standards, best control technology,
and minimum acute toxicity levels. Goals can also be based on emission
levels or ambient levels.
At this time, the major effort in this area is being performed
by Research Triangle Institute. RTI has developed Multimedia Environ-
mental Goals (MEG's) for several hundred pollutants. These identify
many of the pollutants of which investigators need to be aware. They
also define the concentration levels at which these pollutants might be
of concern or to which they can be controlled.
Two major phases of work have been pursued in the development
of MEG's. First, ambient pollution levels have been related to corresponding
concentrations in humans, animals, and plants. These concentrations
have been related to toxic or other detrimental effects within the
organism. Second, substances have been characterized by their chemical,
physical, and other behavioral properties to provide a data base that
can be used by environmental assessment contractors.
RTI has published a two-volume document, Multimedia Environmental
Goals for Environmental Assessment, (EPA-600/7-77-136a and 136b). The
document explains the formats and nomenclatures used in the MEG charts
and presents MEG charts for some 200 pollutants. Future plans include
the development of MEG charts for over 400 additional compounds.
6.0 CONTROL TECHNOLOGY -ASSESSMENT
Pullman-Kellogg is working to develop control technology for
waste utilization and disposal. An early step taken in this program was
to define potential environmental problems associated with fuel conversion
processes. Information on the composition and quantity of typical
discharge streams from coal conversion processes was gathered through
literature searches and contacts with process operators. Most of this
information was primarily concerned with process operations and included
very little effluent stream data. Pullman-Kellogg will continue to
monitor the literature and identify where field data are most needed to
fill information gaps.
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HRI has prioritized a selected group of 16 acid gas removal
processes to arrive at appropriate choices for the following typical
end-uses: a) high pressure (1000 psig) (6895kPa) gasification for the
manufacture of SNG, b) intermediate pressure (400 psig) (2758kPa)
gasification for the manufacture of turbine fuel, c) low pressure gasi-
fication for the manufacture of low pressure fuel gas, and d) low pressure
gasification and compression for the manufacture of synthesis gas. An
overview of control technology for industrial gasifiers is also being
prepared by HRI. This overview will cover several important areas
including coal gasification technology, gas cleanup systems, and com-
parisons of conventional industrial gas cleanup processes to modern
technologies.
In addition to doing general overviews of control technology
requirements that are being developed in the programs listed in Table 1,
Cameron Engineers is compiling a Multimedia Environmental Control
Engineering Handbook (MECEH). This document will include a detailed
description of environmental control technologies that appear to be
applicable to coal conversion processes. This document will include
information on commercially available pollution control equipment. The
objectives of the handbook are to: a) categorize,all commercially
available control technologies into a systematic format, which can be
easily accessed; b) provide technical data for each process, including
process descriptions, ranges of application, efficiencies, and capital
and operating costs; and c) provide a list of those who supply the
specific equipment and/or license the technology.
Cameron has also edited and prepared individual sections of a
first generation standards of practice manual (SPM) for the Lurgi
process. This SPM is titled Evaluation of Background Data Relating
to New Source Performance Standards for Lurgi Gasification, (EPA-600/
7-77-057). The report, which was issued in June 1977, is the result of a
task group effort which reviewed state-of-the-art emission controls for
first generation coal gasification plants. The objective of this effort
was to provide a compilation of technical background information for use
in supporting reasonable levels for New Source Performance Standards for
coal gasification plants. Organizations involved in this effort included
Cameron Engineers, Inc., Catalytic, Inc., Hittman Associates, and Radian
Corporation.
7.0 ENVIRONMENTAL ALTERNATIVES ANALYSIS
Environmental alternatives analysis is aimed at providing a
methodology for identifying the best control options for an emission
source and the best set of control options for a given plant. Consid-
erations in this analysis will include cost and the relative degree of
hazard for the various pollutants. It is too early for much work in
this* area because programs in the other areas are not sufficiently
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advanced. Aerotherm is developing a. Source Analysis Model (SAM) that
can be used to relate the degree of hazard associated with a given
emission from a stream or plant to some defined environmental goals.
(This methodology is being developed outside of the Synthetic Fuels
Program but is one of the methodologies that will be used.) The report,
SAM/IA: A Rapid Screening Method for Environmental Assessment of Fossil
Energy Process Effluents , February 1978 (EPA-600/7-78-015) is available
and is one of the models under development.
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REFERENCES
Ref. 1 American Gas Association, A Comparison of Coal Use
for Gasification Versus Electrification. Arlington, Va.,
26 April 1977.
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