U.S. Environmental Protection Agency Industrial Environmental Research FPA-600/7-78-061
Office of Research and Development Laboratory
Research Triangle Park. North Carolina 27711 MdfCh 1978
LOW- AND MEDIUM-BTU
GASIFICATION SYSTEMS:
Technology Overview
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of. control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-78-061
March 1978
LOW- AND MEDIUM-BTU
GASIFICATION SYSTEMS:
Technology Overview
by
Paul W. Spaite Gordon C. Page
Paul W. Spaite Company and Radian Corporation
6315 Grand Vista Avenue 8500 Shoal Creek Boulevard
Cincinnati, Ohio 45213 Austin, Texas 78766
Contract No. 68-02-2149 Contract No. 68-02-2147
Program Element No. EHE624A Program Element No. EHE624A
EPA Project Officer: William J. Rhodes
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N.C. 27711
Prepared for:
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
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Abstract
This report gives an overview of systems which are most likely to
find commercial application for production of low- and medium- BTU
gas from coal. Present and projected applications of the technology
are reviewed. Individual processes are described and all potential
discharges to air, water or land are identified and discussed.
The coverage of the subject is felt to be complete in the sense that all
applications of the technology and all potentially polluting discharges
have been considered. The report does not, however, present detailed information
on composition of discharges, control technology, economics and the like.
It is designed for use in development of programs and studies needed
to quantify potential pollution control problems, prioritize environmental
protection needs and related activities. It was felt that inclusion of
all background data would detract from, rather than enhance, its usefulness
for broad analysis. For those needing more detailed information references
co background documents have been supplied.
11
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CONTENTS
Page
Abstract ii
Figures iv
Tables iv
I. Introduction 1
II. Status of Technology 3
Cost 5
Energy Efficiency 7
Applicability 9
Extent of Development Work 12
Commercial Prospects 13
III. Description of Technology 18
Gasification Systems 18
Gasification Processes 20
Raw Gas Cleaning Processes 24
Goal Pretreatment Processes 27
Raw Materials 27
Products 29
IV. Environmental Impacts 33
Goal Pretreatment 34
Gasification 38
Gas Cleaning 39
References 41
Appendices
A - Environmental Assessment/Control Technology A-!
Development Protocol
B - Nomenclature Definitions for Energy Technologies B-l
C - Population of Low/Medium-Btu Gasifiers c~l
D - Description of Processes for Low- and Medium BTU D-l
Gasification Systems
111
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LIST OF FIGURES
Figure 1 - Process Modules for Low-and Medium-Btu 19
Gasification Systems
LIST OF TABLES
Table 1 - Potentially Important Gasification Systems 16
Table 2 - Status of Low- and Medium-Btu Gasification 21
Technology
Table 3 - Promising Low- and Medium-Btu Gasification 23
Systems
Table 4 - Discharges From Low- and Medium-Btu 35
Gasification Systems
iv
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I. INTRODUCTION
The Environmental Protection Agency's Industrial Environ-
mental Research Laboratory at Research Triangle Park is con-
ducting a series of environmental assessments. These activities
involve continuing iterative studies aimed at 1) identification
and characterization of industrial process discharges, 2) eva-
luation of pollution control and waste disposal options, 3)
comparison of estimates for environmental loadings with applic-
able standards and projected environmental goals, and 4)
prioritization of potential pollution problems and control
technology needs. This overview report, which deals with low-
and medium-Btu gas, is one of a series which is being developed
for the technologies which deal with processing of coal. It
was developed in connection with activities to accumulate
current process technology for the overall assessment program
which is described in Figure 1 of Appendix A.
The objective of this report is to describe the system*
or combinations of processes which are likely to be used for
production of low- and medium-Btu gas from coal. This involves
Certain terms, such as "systems", which have a number of
commonly accepted meanings have been defined specifically for
use in environmental assessment activities of I.E.R.L/RTP.
A glossary of these terms is included in Appendix B.
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making judgments as to types of coal that will be processed,
types of gasifier (and auxiliary processes) which will be
employed, and markets which will develop for gas from coal.
After definition of the overall systems of greatest potential
for commercialization, it is expected that conceptual designs
will be developed for use in predicting and assessing potential
environmental impacts. Data supporting statements in the over-
view report are mainly contained in Radian Corporation's report
to the Environmental Protection Agency entitled "Environmental
Assessment Data Base for Low/Medium-Btu Gasification Technology1
(EPA-600/7-77-125a and b, November 1977) (1). Where other
sources of information were used, they are cited in the text.
The balance of the overview report is divided into three
sections. Section II, "Status of Technology", presents infor-
mation intended to define the future prospects for coal gasifi-
cation in relatively broad terms. Section III "Description of
Technology" presents more specific information on individual
processes which are considered likely to be employed commer-
cially and Section IV "Environmental Impacts" discusses the
kinds of pollutant discharges which must be anticipated.
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II. STATUS OF TECHNOLOGY
The production of low- (5.6 x 10s J/Nm3, 150 Btu/scf) and
medium- (13.1 x 106 J/Nm3, 350 Btu/scf) btu gas from coal has
been practiced for many years both in the U.S. and in other
countries where coal is an abundant resource. At one time an
estimated 11,000 coal gasifiers were in service in the U.S.
Most of these were retired when cheap natural gas became avail-
able. For many years the technology for gasification was
dormant. Improvements were limited to evolutionary changes in
the relatively few systems which were installed. Beginning in
the 1960's the Federal government, in concert with industry,
started programs to develop improved gasification systems which
would be more widely useful than those on the market. The
early programs were mainly aimed at development of processes
for production of high-Btu gas which could be used to supplement
supplies of natural gas used for home heating. Now, with gas
supplies dwindling and petroleum prices escalating, there is
increasing interest in evaluating the possibility of substituting
gas from coal for natural gas or petroleum derived fuels used
by industry.
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Low- and medium-Btu gasification systems being considered
are in varying stages of development. Also they are extremely
variable as far as scale of operation and other features are
concerned. Several now in operation involve fixed-bed gasifiers
about 8-10 feet in diameter which process about 15 tons per day
of low sulfur coal. The gas, not requiring sulfur removal to
meet present standards, is passed through a dust collector and
burned to provide process heat. The most complex system would
involve production of fuel for "combined cycles" in which
electricity is produced when the gas is burned, expanded through
a gas turbine, and then sent to a boiler where the sensible heat
is used to produce steam for a steam turbine. For a 500 MW
plant 5-10 gasifiers around 10 feet in diameter processing 50-80
Kg/sec (5000-8000 tons day day of coal) (2) would be required.
A number of the smaller systems are offered commercially
and a few are operating in the U.S. The larger systems are
strictly conceptual and it would require 7-10 years for design
and construction of such a plant. Neither the older systems,
such as those offered commercially, nor the new processes under
development, have been proved to be satisfactory solutions to
today's clean fuel supply problems. Information on their cost,
fuel efficiency, applicability to various markets, and environ-
mental impacts is lacking. Further, it is not known whether
they are representative of the best systems (from the standpoint
of either process considerations or environmental impacts)
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which could be built today. Hence, more information is needed
to determine the commercialization potentials of the various
candidate systems.
Because of the lack of information, it is difficult to
predict how the different systems will fare in competition with
each other or how low-Btu gasification will fare in competition
with other technologies such as direct coal combustion with flue
gas desulfurization and fluidized-bed combustion. It is
possible, however, to comment on some of the factors for judging
the status of development. The most important of these factors
are:
The cost of the fuel gas produced,
Energy efficiency of the process,
Applicability of process to different
end-use requirements,
Extent of on-going development work, and
Factors relating to possibilities for, and
potential rate of commercialization of
environmentally sound systems.
COST
Projecting the costs of low- and medium-Btu fuel gas pro-
duced from coal is difficult because of uncertainities in the
limited cost data available and because costs are sensitive to
the type of system and plant location. It appears, however,
that small, relatively simple gasification systems which convert
low sulfur fuels into fuel for direct process heat could pro-
duce gas for about $2.50/109J ($2.60/106 Btu). Such a system
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would employ a hot cyclone for particulate collection. If more
sophisticated gas cleaning including sulfur removal was required,
it could easily add an additonal $1.00-$2.00/109J ($1.05 to $2.10
per 106 Btu) to the cost of the fuel. Such a unit would produce
anywhere from 0.1 to 2.4 x 109J/sec (10 to 200 x 106 Btu/day).
The use of gasifiers in combined cycles to produce elec-
tricity presents a very different situation. Such a plant would
produce on the order of 1.8 x 109 J/sec (150 x 10s Btu/day) of
product gas. The gasification system would cost in the neighbor-
hood of $250-$400 million dollars and would produce gas costing
2 to 3 times as much as the coal supplied (3). These amounts
represent great increases over costs estimated when expanded
usage of low-Btu systems began receiving serious consideration
in the U.S. This continuing escalation is attributable to
rising construction costs, rising fuel costs, and a better
understanding of problems associated with commercialization of
the technology. Other developing energy technologies being
considered for electrical generation have undergone, or are
subject to, similar escalation of projected cost.
Despite the apparent high cost of gas from coal relative
to fuels available in the past, it appears that low- and
medium-Btu gasification systems will be competitive in numerous
critical applications where clean, gaseous fuels are required
but will not be available from other sources. For many
industrial applications the increased fuel cost will have to be
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weighed against the losses which would be suffered by not
operating and gasification at any cost that can reasonably be
foreseen will be attractive.
Energy Efficiency
Like costs, the energy efficiencies of the various gasifi-
cation systems being studied are difficult to determine.
Thermal efficiency is a cost factor with special significance
as far as the applicability of the technology is concerned.
Low efficiencies will tend, in specific applications, to make
the gasification non-competitive with technologies serving the
same need, e.g., the energy efficiency of a low-Btu
gasification/combined-cycle system must be high enough to make
it competitive with coal-fired power plants equipped with sulfur
and particulate emission control hardware. Efficiency will be
less critical in some of the other proposed industrial applica-
tions for gasification plants where gas must be used and is
either not available or prohibitively expensive. However, with
prices escalating, efficiency of coal utilization will be of
increasing importance in all applications.
At this point, many questions relating to the efficiency
of gasification systems still exist. The confusion associated
with efficiencies which have been quoted in the literature can
be illustrated by considering some of the variables involved.
In one study, it was reported that no more than 65 percent of
the heat content of the coal supplied to an entrained-bed,
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pressurized, slagging ash gasification system and the asso-
ciated boiler supplying electrical power could appear as product
heating value. A 4 percent penalty was estimated if the product
fuel was to be used for coal drying. This reduced the net pro-
cess efficiency to 61 percent. When the associated boiler was
assumed to be fired with product gas instead of coal, the
estimated overall plant efficiency dropped to 53 percent. If
the process operating pressure was assumed to be 0.10 MPa (15
psig) instead of 1.03 MPa (150 psig), the savings in compres-
sion energy increased the base efficiency of 61 percent to 69
percent (4). From these and other data it would appear that
the figures of 85 percent and above figures which have been
quoted in the literature are either optimistic or are not
taking into account all energy requirements. Efficiency of
60-65 percent for present day gasifiers and perhaps 75 percent
for improved gasifiers of the future are considered more
reasonable estimates.
The importance of process efficiency for both gasifiers
and gas turbines in combined cycles operation can be illustrated
by considering the advancement of turbine technology needed to
make combined cycle power using gas from present day gasifica-
tion processes economically competitive. Increasing present
tolerable turbine inlet temperatures of about 1400°K (2000°F)
to temperatures of about 1600°K (2400°F) has been estimated to
be necessary to make combined cycles about equal in cost to
8
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conventional boilers for production electricity. Further
success in turbine development would be required for a clear
economic advantage (3). Thus while combined-cycle power
generation from low-Btu gas offers substantially higher overall
cycle efficiencies, success in development of more efficient
turbines and gasifiers will be necessary to realize potential
advantages.
Applicability
At this point low- and medium-Btu gasification systems
appear to be of greatest near-term interest for their ability
to supply gases for industrial usage. The industrial applica-
tions of probable future importance are (1) synthesis gas for
ammonia and methanol, (2) fuel for direct process heat in
processes such as brick and lime kilns, glass furnaces, paint
drying ovens, etc. and (3) fuel for small and intermediate size
industrial boilers. Gasification, especially for synthesis gas
and direct process heat systems such as those now in operation
could become commercially important a few years in the future.
Use of coal gasification to produce medium-Btu gas as a
source of synthesis gas for ammonia and methanol could serve as
a replacement for 400 Nm3/sec (4.7 x 101l scf/yr) of natural
gas (5). This total market is small compared to other demands,
but substitution of gas from coal in this application would
probably be economically more acceptable because of the limited
number of alternatives which are available. Further, such a
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substitution of gas would represent a modest technical advance
since commercially available technology appears to be applicable
to design of plants which meet present environmental standards.
Production of low- or medium-Btu gas for production of
direct heating for industrial processes appears promising for
the same economic and technical reasons. However, the overall
market is greater, amounting to some 4 x 1015 Btu/yr (equivalent
to 340 Nm3/sec, 4 x 1012 scf/yr of natural gas) (6)-
The use of low- or medium-Btu gas in small industrial
boilers (<10MW equivalent) to replace distillate oil or natural
gas would require 2.1 x 101! J/sec (6.2 x 101s Btu/yr), an
amount far exceeding supplies which could be generated by gasifi-
cation in the foreseeable future. The extent to which gas from
coal would be in demand for existing boilers is doubtful.
Retrofit of gas fired boilers is not likely to be practical in
many situations. The cost of installing coal handling equip-
ment would be high even if space were available. Further,
reduced output of the boiler, compared to that which would be
obtained using natural gas, would result in additional economic
penalties. Technology being developed for production of gaseous
fuels from residual oil may however, find application where
feedstocks are available and the use of gas from coal for new
boilers may prove practical. Also on-site combustion of low-
Btu gas in boilers designed for its use may be economically
attractive for the near future and medium-Btu gas distributed
10
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to new and existing boilers from a central gas generating plant
to consumers within 100 miles appears to be a viable option (3).
The economic competitiveness of low- and medium-Btu gas
in industrial boilers will be strongly influenced by the advances
which are made in development of fluidized bed combustion systems
and in development of flue gas cleaning systems which are
applicable to boilers in the 5 to 50 MW equivalent size range.
At present large quantities of gas and petroleum derived fuels
are burned in industrial boilers of this size. It seems that
some method of burning coal will be substituted for gas and oil
in these applications as the shortages of energy become more
critical.
The only potential application of low- and medium-Btu gas
other than feedstocks, direct industrial process heat, and
industrial boilers is in production of electricity. In this
application conversion of existing boilers to gas produced from
coal will be impractical with available technology. Gasifica-
tion units could be designed for operation with new boilers of
conventional design but this is unlikely. In utility applica-
tions design of new units equipped with coal gasifiers must
compete.with existing technology, i.e., large conventional
boilers equipped with flue gas cleaning systems. Comparative
analysis of the two systems indicates that substantial improve-
ments in the economics of gasification will be required before
this potential market can be penetrated (3).
11
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The outlook for low-Btu gasifications systems integrated
in new combined cycle plants is, as indicated in the discussion
of gasification costs, somewhat more optimistic. If gas turbine
and/or gasifier efficiencies can be increased sufficiently, the
economics of combined cycles burning gas from coal will become
attractive.
Extent of Development Work
Gasifier operating experience, as indicated earlier, is
quite extensive. The applicability of some of this experience
to current U.S. needs, however, is questionable. This is
particularly true of the environmental aspects of gasification
technology since many of the systems which were utilized in the
past would not be environmentally acceptable by today's
standards.
Government agencies such as the Environmental Protection
Agency, Department of Energy and National Institute of
Occupational Safety and Health, as well as a significant number
of industrial organizations, are sponsoring research aimed at
understanding and improving the capabilities of gasification
systems. Work in this connection is being concentrated on
evaluations of both presently available and advanced gasification
system designs which utilize features enhancing the efficiency,
environmental acceptability, and the operability of systems
which are representative of currently available or developmental
technology. This research has been directed toward improved:
12
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0 Characterization of the environmental impacts
from gasification plant discharges,
0 High temperature product gas cleanup processes,
0 Coal feeding and ash removal devices (particularly
for pressurized systems),
0 Water treatment methods,
0 Materials of construction, and
0 Reactor designs.
Much of the on-going work is hardware oriented. Commercial
and demonstration projects are the subject of many projects.
At present most of the expenditures are for projects aimed at
fitting existing technology to newly identified markets in
environmentally sound systems. It is believed, however, that
fundamental studies of gasification are needed (3). Also, it
is clear that analysis of control technology for gasifier
discharges is needed. And studies to better define the level of
tolerable discharges of potentially harmful emissions are
essential to effective use of gasification for present and
future energy needs. Work to meet these needs has been initiated
and future activity will provide support for development programs
on large scale equipment.
Commercial Prospects
The prospects for expanded commercialization of low- and
medium-Btu gasification will be influenced by many factors.
Expanded use of presently available gasification systems to
produce medium-Btu gas for use in chemical synthesis or off-site
13
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combustion, and low-Btu fuel for use in on-site direct process
heat or as a reducing gas, will require demonstration that the
available systems can be installed with appropriate pollution
control equipment. The rate of installation of units demonstrated
to be adequately controlled will depend primarily on the rate at
which process suppliers can respond to demand for new units.
Until recently, there was a fairly small group of process vendors
who were actively marketing their gasification systems. Generally
these systems were based on designs which were widely used in
the past. Increasing awareness of the potential for the applica-
tion of gasification systems in recent years led to an expansion
in the number of groups that are actively developing and
marketing gasification systems. It is expected, however, that
the growth of the existing coal gasification industry during
the next few years will tend to be limited by the time required
to design and build the specialized equipment required in such
plants. For this reason, it will probably be several years
before there will be a significant increase in the number of
operating gasifiers in this country. The number of operating
gasification systems may increase substantially, however,
between 1980 and 1990.
Commercial application of medium-Btu gas systems supplying
fuel for off-site combustion may be more complicated. Even if
presently available, or advanced developmental gasification
systems, are successfully demonstrated in other service, a
14
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central plant large enough to supply fuel via pipeline to
customers within a one-hundred mile radius would present sig-
nificantly different problems. The time required to build the
plant would be longer. Business arrangements would be more
complicated. The number of sites where coal is available,
where capital for such a plant is available, and customers for
the product are available, may be limited. Finally, fluid bed
combustion may be more attractive to some customers who need
alternative sources of heat.
Successful development of combined cycle systems for gen-
eration of electricity in commercial systems may be dependent
on more intangibles than other potential applications. Large
scale gasification must be demonstrated to be economically
viable and environmentally sound. Improvements in efficiency of
the gasifier and the gas turbines which are available will be
needed to make the approach competitive with conventional power
boilers equipped with flue gas cleaning equipment. Further,
fluidized bed combustion systems which are being developed for
use in combined cycle systems for electrical generation could
prove to be more attractive.
In summary, it appears that low- and medium-Btu gasifica-
tion systems probably can be supplied to meet demand for fuels
when gas and oil are no longer available for some industrial
usage. The systems considered most likely to find wide
application are shown in Table 1. Fluid bed combustion may be
15
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Table 1. POTENTIALLY IMPORTANT GASIFICATION SYSTEMS
Type of gasification
system
Product
Pressurized (low-Btu)
Pressurized (medium-Btu)
Atmospheric (low-Btu)
Fuel for combined electrical
generating cycles
Fuel for off-site boilers
Fuel for off-site process heat
Synthesis gas for on-site use
Synthesis gas for off-site use
Fuel for on-site boiler firing
Fuel for on-site process heat
Reducing gas for on-site processes
16
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competitive for some of these markets but for others coal
gasification seems to be the only viable alternative. For
industrial boilers and electric utility fuels, gas from coal
may prove to be competitive. It will, however, have to be more
economical and effective than conventional boilers with avail-
able pollution control systems or other technologies which are
under development.
17
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III. DESCRIPTION OF TECHNOLOGY
The gasification systems which are most likely to be
employed for production of low- or medium-Btu gas are not, as
might be supposed from the many combination of processes which
might be visualized, numerous. In this discussion the most
promising systems (and their constituent processes) are identi-
fied and discussed from the standpoint of raw material require-
ments, and product gas characteristics.
Gasification Systems
The gasification process is a key element of a total
system comprised of three operations (coal pretreatment, gasifi-
cation, and raw gas cleaning) which are likely to be necessary
for any facility in which coal is converted to gaseous fuels or
chemical feedstocks. The specific processes employed for any
of the three operations will be determined by 1) the properties
of the feedstock coal, 2) product quality requirements, and 3)
the type of gasifier that is employed. All three operations
have potential for discharge of pollution. The discharges and
the potential severity of their environmental impact will
depend on the characteristics of the specific processes employed.
Figure 1 depicts the processes which would be employed for basic
systems with greatest potential for commercialization. These
are as follows:
18
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OAUOU* HAITI
iKHHO WAIT! ftTMJAUS
f ^ tOitt VACT1 ITHEAUt
Figure 1. PROCESSES FOR LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
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1) Pressurized gasifiers producing low-Btu fuel
"combined cycles",
i
2) Pressurized gasifiers for production of medium-Btu
synthesis gas for ammonia and methanol synthesis
for on-site or off-site usage,
3) Pressurized gasifiers for off-site combustion
of medium-Btu fuel,
4) Atmospheric gasifiers for production of low-Btu
fuel for on-site combustion, and
5) Atmospheric gasifiers for on-site production of
low-Btu reducing gas.
As shown in Figure 1, gas quenching and sulfur removal may
not be needed for production of combustion gases. Generally
direct combustion of gases without sulfur removal will be limited
to situations where low sulfur coal feedstocks are locally avail-
able hence such applications may be very limited in number.
Gasification Processes
On the order of 68 different gasification processes can
be identified which either have been used commercially in the
past or are currently under development. These are shown in
Appendix C. Twenty-five of the most prominent of these gasifi-
cation processes are shown in Table 2. All involve partial
oxidation of coal. Where the system is "air blown", low-Btu gas
with a heating value in the neighborhood of 5.6 x 106 J/Nm3
(150 Btu/scf) is produced. Where oxygen is used, medium-Btu gas
with heating value of about 13.1 x 106 J/Nm3 (350 Btu/scf) is
obtained.
Seven of the gasifiers in Table 2 are currently being used
20
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Table 2.
STATUS OF U.S. AND FOREIGN LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Gasifier
Lurgi
Wellman-Galusha
Woodall-Duckman/
Gas Integrale
Koppers-Totzek
Minkler
Chapman (Hilputte)
Riley Morgan
Mellman Incadenscent
BGC/Lurgi Slagging
Bi-Gas
Foster Wheeler/Stoic
Pressurized Wellman-
Galusha (MERC)
GFERC Slagging
Texaco
BCR Low-Btu
Combustion Engineering
Hygas
Synthane
COj Acceptor
Foster Wheeler
Babcock t Milcox
U-Gas
Nestinghouse
Coalex
Licensor/developer
Lurgi Mineralfilteehnik GmbH
McDowell Hellman Engineering Co.
Woodall-Duckham (USA) Ltd.
Koppers Company! Inc.
Davy Powergas
Hilputte Corp.
Riley Stoker Corp.
Applied Technology Corp.
British Gas Corp. and Lurgi
Mineraloltechnik GebH
Bituminous Coal Research, Inc.
Fostet'Wheeler/Stoic Corp
ERDA
ERDA
Texaco Development Corp.
Bituminous Coal Research, Inc.
Combustion Engineering Corp.
Institute of Gas Technology
ERDA
ERDA
Foster Wheeler Energy Corp.
The Babcock t Wilcox Co.
Institute of Gas Technology,
Phillips Petroleum Corp.
Wcstinghouse Electric Corp.
Inex Resources, Inc.
Number of gasifiers currently operating (No. .of gasifiers built)
Low-Btu gas Medium-Btu gas Synthesis gas Location Scale
5
8(ISO)
2(12)
1
(2*)«*
!•
1*
1*
1
1
1
1
1
(1*1
(39)
(23)'
(22) Foreign Commercial
US/Foreign Commercial
(8)** Foreign Commercial
(39)**
6(14)
-
-
-
-
-
_
!•
-
-
-
-
-
-
-
-
-
-
Foreign
Foreign
US
US
US/Foreign
Foreign
US
us
us
us
us
us
us
us
us
us
us
us
us
us
us
Commercial
Commercial
Commercial
Commercial
Commercial/
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
Demonstration
(High-Btu)
Demonstration
(High-Btu)
Demonstration
(High-Btu)
Pilot
Pilot
Pilot (400
Ib/hr coal)
Pilot
Pilot
Under construction.
Demonstration scale indicates 2000 to 10,000 Ib/hr coal feed.
Pilot scale indicates 400 to 1SOO Ib/hr coal feed.
Undetermined number overseas currently in operation.
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to satisfy some commercial demand for low- and medium-Btu gas.
These are:
Chapman (Wilputte),
Koppers-Totzek,
• Lurgi,
Wellman-Galusha,
Wellman Incandescent,
Winkler, and
Woodall-Duckham/Gas Integrale.
A number of the remaining gasifiers listed in Table 2
appear to have significant commercialization potential. For
example, a commercial-scale Riley-Morgan gasifier has been
operated as a development unit and a commercial-scale Coalex
plant and Foster Wheeler/Stoic gasifiers are or will be under
construction in the near future.
The seven commercial gasification processes together with
seven others, which are currently under development, make up a
population of fourteen, which on the basis of a screening
analysis have been identified as the most promising candidates
for satisfying near-term commercial needs for low- and medium-Btu
gas.
The fourteen which are considered to be members of this
"most promising" group are shown in Table 3. All fall into one
of six classes of gasifier (shown in Figure 1) which have
unique environmental impacts. These six classes and the pro-
prietary processes which comprise each class are as follows:
22
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Table 3. PROMISING LOW AND MEDIUM-BTU GASIFICATION
SYSTEMS
First group
Second group'
Third group"
0 Wellman-Galusha ° Chapman (Wilputte)
Lurgi
Woodall Duckham/
Gas Integrale
0 Koppers-Totzek
0 Winkler
0 Wellman Incandescent
0 Foster-Wheeler/Stoic
Riley Morgan
0 Pressurized Wellman-
Galusha (MERC)
0 BGC/Lurgi Slagging
Gasifier
0 Texaco
0 Bi-Gas
0 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.
23
-------
Fixed-bed atmospheric dry ash gasifier;
Chapman (Wilputte),
Foster Wheeler/Stoic,
Riley-Morgan,
- Wellman-Galusha,
Wellman Incandescent, and
- Woodall-Duckham/Gas Integrale
Fixed-bed pressurized dry ash gasifier;
Lurgi, and
- Pressurized Wellman-Galusha (MERC)
Fixed-bed pressurized slagging ash gasifier;
- BGC/Lurgi Slagging Gasifier
Fluid-bed atmospheric dry ash gasifier;
- Winkler
Entrained-bed atmospheric slagging ash gasifier;
Coalex, and
Koppers-Totzek
Entrained-bed pressurized slagging ash gasifier;
Bi-Gas, and
Texaco.
Raw Gas Cleaning Processes
As indicated earlier, the specific processes making up a
system will be determined mainly by type of coal processed and
product requirements. Where sulfur in the input coal is low,
sulfur removal may not be required if the gas is to be used for
24
-------
direct process heat or burned in boilers. Coals that are low
enough in sulfur to meet present air pollution requirements are,
however, scarce and more stringent standards would make the
applicability of such systems very rate. Where the gas is for
combined cycles, for synthesis gas, or for transportation in
pipelines, sulfur removal will be required. The type of gasifier
employed will also have an independent influence in that several
of the six basic types of gasifiers, as shown in Figure 1, may
meet the same input and output requirements. This influence
will be reflected mainly in the raw gas cleaning requirements.
Whether a gasifier is pressurized or operated at atmospheric
pressure and whether it operates at a high temperature, producing
a tar-free gas or at a low temperature producing gas with con-
densible hydrocarbons are important factors which dictate the
type of gas cleaning processes which will be used. For tar-free
gases, high temperature dust collectors and heat recovery equip-
ment will precede the gas quenching needed to adjust the
temperature for the sulfur removal process needed for present
day systems.
For gases containing tar, wet or dry systems may be
employed to remove contaminants and cool the gas. For pres-
surized systems "physical solvent" processes which are most
applicable at high pressures up to 7 MPa (1000 psia) would be
favored for sulfur recovery from gases which are generated for
combined power cycles, for distribution in medium-Btu gas
25
-------
transportation systems, or for use in synthesis of tnethanol or
ammonia. Systems delivering gas at these high pressures would
maximize the efficiency of the power production cycle and would
supply compressed gases, most economically, for pipeline trans-
port. Also they would be more compatible with the high pressures
used in the synthesis of chemicals than atmospheric systems.
Pressurized systems supplying medium-Btu gas for usage as
synthesis gas will be likely to employ gas cleaning systems
which operated as near as possible to the operating pressure of
ammonia synthesis units 20 MPa (2900 psia) or methanol synthesis
units 5-10 MPa (700-1500 psia). Cleaning systems operating in
this range would include physical solvents and hot carbonate.
Processes which appear attractive for cleaning sulfur from
product gases produced by atmospheric gasifiers include chemical
solvent and direct conversion. Examples of solvent used in
chemical solvent processes include amines and alkaline salts.
An example of a direct conversion system is the Stretford
process.
The primary advantage of using a direct conversion process
for cleaning sulfur from raw gases is that it produces sulfur
directly. Chemical solvent processes operate only as concentra-
tion steps. They produce tail gases containing sulfur compounds
which require subsequent processing to produce sulfur. The
primary disadvantage of using a Stretford process is that organic
sulfur compounds (COS, CS2, mercaptans, etc.) are not converted
26
-------
to sulfur and exit with the product gas. These factors along
with economic considerations must be considered when selecting
a sulfur cleaning system for atmospheric gasification systems.
Coal Pretreatment Processes
Generally any coal can be gasified if proper pretreatment
is employed, however, certain gasifier designs are better suited
to some coals than others, and the type of pretreatment will
vary for different coals. With some high moisture coals, coal
drying may be desirable. Also where caking coals are to be
gasified, partial oxidation may be employed to simplify gasifier
operation. Other pretreatment operations include crushing and
sizing and briquetting of fines for feed to fixed-bed gasifiers.
For fluid- or entrained-bed gasifiers, the coal feed is
pulverized.
Raw Materials
The properties which are important in determining the
suitability of a given coal for use in a specific gasification
process are:
Particle size and friability.
Moisture content,
Caking properties,
Ash content and fusion temperature,and
Sulfur content.
Particle size and caking properties are probably the most
critical factors as far as the operability of fixed-bed gasifiers
27
-------
is concerned. Since "fixed-bed" systems actually utilize
slowly moving beds to which coal is added and ash is withdrawn
regularly, uniform coal throughput, and good gas-solid contact
can be maintained only if both of these factors are maintained
within limits specified by the design of the gasifier. For
fixed-bed gasifiers, fines (<3mm in diameter) from the crushing
and sizing will generally have to be burned in a boiler or
briquetted if they are to be fed to the gasifier.
Moisture content and ash content are generally less critical
than particle size and caking properties. Coal feedstocks with
a high mosture content can, however, cause operational problems
for coal feeding devices. The high moisture content may also
result in low gas outlet temperature 400°K (300°F) which can
produce condensation of tars and oils in particulate removal
equipment. If the coal feedstock must be dried, the energy
requirement for drying the coal will result in lower thermal
efficiency of the overall process. Even if drying is not
required, coals with higher moisture content will result in
lower gasification efficiency because of the energy which must
be supplied to evaporate the moisture in the coal.
Caking coals may cause operating problems for fixed-bed
and some fluidized-bed gasifiers. Fixed-bed gasifiers may
require bed agitators in order to gasify caking coals. Partial
oxidation can make caking coals suitable for gasification.
Caking properties are not a limitation for entrained-bed gasifiers
28
-------
Ash content and fusion temperature are important factors for
gasifiers which operate above the ash fusion (slagging) tempera-
ture. Slagging fixed- and entrained-bed gasifiers may require
the addition of fluxing agents to the coal feedstock in order to
lower the fusion temperature of the coal ash. Slagging fixed-
bed gasifiers may also require the addition of slag to the coal
feedstock for coals with a very low ash content in order to
maintain adequate slag withdrawal rates.
Sulfur content can be a factor in selecting acceptable
coal feedstock if no acid gas removal operations are to be used.
If the product gas is to be used as a synthesis gas, fuel for
combined-cycle turbines, or as an off-site combustion fuel
transported by pipeline, acid gas removal will always be
required. For on-site combustion of the product gas, acid gas
removal may not be required if the coal sulfur content is
sufficiently low. The acceptable sulfur level will be deter-
mined by the federal, state, and local sulfur dioxide emission
regulations.
Products
The six potential end-use alternatives for coal gasifier
product gas are the following:
On-site combustion fuel (Low-Btu),
Off-site combustion fuel (Medium-Btu),
• Combined-cycle fuel (Low-Btu),
• Off-site use as synthesis gas (Medium-Btu),
29
-------
On-site use as synthesis gas (Medium-Btu),
and
Reducing gas (Low-Btu).
On-site combustion refers to a direct combustion process which
consumes the product gas within a relatively short distance,
i.e., within 16 Km (10 miles) of the coal gasification plant
(3). Although any of the fourteen gasifiers just discussed
would be used to produce on-site combustion fuel, the atmos-
pheric pressure systems appear to be the best suited to this
end-use.
Off-site combustion refers to a direct combustion process
which consumes the product gas at a site that can be up to 160
Km (100 miles) from the coal gasification plant (3). Pres-
surized gasifiers are well suited to this end-use option, since
it is cheaper to compress the air or oxygen and steam feed to
the gasifier than it is to compress the product fuel gas. Also,
air-blown gasifiers do not appear to be well suited to the
production of off-site combustion fuel because of the excessive
costs of transporting a gas with a low heating value.
The first step in a combined-cycle operation is the com-
bustion of a pressurized fuel gas and the expansion of the com-
bustion gases through a gas turbine to provide shaft work.
Then, the sensible heat of the gas turbine exit gas stream is
recovered in a conventional steam turbine cycle to provide addi-
tional shaft work. Combined cycles are primarily used in the
generation of electricity. Pressurized gasifiers are most
30
-------
applicable to this end-use option, since combined-cycle gas
turbines are designed to operate at high turbine inlet gas pres-
sures. Combined cycle plants will have to b_ quite large. To
be competitive, economy of scale advantages will have to be
maximized. For plants of this size, cost and complexity of
adding an oxygen plant will probably make oxygen blowing to
produce medium-Btu gas unattractive compared to firing of
low-Btu gas (3).
Synthesis gas is used as a raw material for the production
of chemicals. It seems unlikely that coal gasification will be
used extensively for chemical products other than ammonia or
methanol which is presently made in large quantities from
natural gas. Other chemicals such as benzene, ethylene,
propylene, etc. will continue to come from oil or perhaps in
the future from coal derived liquids. In most applications, a
gas having high concentrations of hydrogen and carbon monoxide
and low concentrations of methane and other hydrocarbons is
desired. Because of this composition requirement, an entrained-
bed, slagging ash gasifier is probably best suited to this
end-use option.
.Gas from coal is expected to find some application in
direct reduction of iron ore and may be used in other applica-
tions where a reducing gas is needed, e.g., to regenerate
sorbent materials used in flue gas cleaning systems for col-
lection of S02. Neither oxygen blowing nor pressurization would
31
-------
offer any advantage hence, atmospheric air blown systems are
most likely to be used.
32
-------
IV. ENVIRONMENTAL IMPACTS
The environmental impacts associated with coal gasifica-
tion operations range from conventional pollution problems such
as coal dust emissions to such ill-defined problems as fugitive
gaseous emissions (hydrocarbons, H2S, CO, HCN, etc.) which,
because of their probable noxious character, will require the
design of special systems for their control. The coal feed
will typically contain 5-15 percent ash and will have a large
number of trace metals which are potential pollutants. Also
the chemical structure of coal is such that thermal processing
tends to liberate toxic and carcinogenic organic materials. The
ash will probably contain a small amount of organics and the
disposal problem will be similar to that associated with ash
from a conventional power plant. The trace metals and organic
materials produced by thermal treatment must be controlled. The
point at which hazardous discharges appear, depends on the nature
of the coal gasification system, e.g. those systems which produce
raw fuel gas containing tars and particulate that are removed
with wet scrubbers, can produce both waste water and solid waste
which is contaminated with highly offensive organic and inorganic
materials. Even where processes are operated so that tars and
condensible organics are largely eliminated, gas quench water
33
-------
contaminated with materials such as cyanides, sulfides, etc.
will be produced.
The various points for discharge of emissions have been
identified for the important system configurations. These are
shown in Table 4. All of the three basic operations associated
with gasification technology (coal pretreatment, gasification,
and gas cleaning) can produce discharges with potential for
environmental impacts. At present the nature of most discharges
have been described only in qualitative terms. The minimum
amount of operating experience with gasifiers which we now have,
is in large part, not applicable to systems of the future.
However, it is possible through engineering analysis of present
gasification systems and related operations such as utility
boilers, coke ovens, and coal preparation plants to develop
some perspective on the overall problem. Such background
information has been used to develop this overview which will
serve as a tool in designing of programs for sampling and analysis
and conceptual design studies needed to quantify and prioritize
environmental control problems. General discussion of emissions
from the three basic operations is presented in the following
sub-sections.
Coal Pretreatment
Emissions from coal pretreatment processes generally fall
in the category of problems which appear to be solvable. Wastes
from coal storage, handling, size reduction, and classification
34
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Table 4. DISCHARGES FROM LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Operation
Discharge stream
source
Coal Pretreatroent
Storage, handling and
crushing/sizing
Discharge
streams
Dust emissions
CO
Ui
Coal drying, partial
oxidation and briquetting
Hater runoff
Solid wastes
from crushing
and sizing
Vent gases
Coal Gasification
Coal feeding device
Vent gases
Description
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 organics and inorganics in
runoff water produced for coal stor-
age piles and dust control or
suspression 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.
Theso emissions will contain coal
dust and combustion gases along
with a variety of organic compounds
liberated as a result of coal
devolitization reactions. There
arc currently little data on the
characteristics of those organic
spccioa.
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.
Remarks
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. En-
closures and hoods have been used for
coal crushing/sizing.
Proper runoff water management techni-
ques 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 nccJ to he
obtained to evaluate 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 con-
trolled. Afterburners in addition to
particulate collection devices may be
required.
Vent ganos front coal feeders can
represent a significant environmental
and health problem. Control of those
emissions is required; however, th.-
characteristics of these gases need
to be tint crfiinod to irjili-mont an
aiKi;i:itc crr-trol method.
-------
Table 4. DISCHARGES FROM LOW- AND MEDIUM-BTU CASI !• ICAHON SYSTM.'-'.S
Operation
Discharge stream
source
Discharge
streams
Description
Cont
Remarks
Ash removal device
Vent gases
ON
Coal gasifier
Spent ash
quench water
Ash or slag
Start-up vent
stream
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
organics and inorganics and will
require control.
There are limited data on the
characteristics of the ash and slag
especially concerning the amount of
unroacted 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.
sources of contaminated water
may be used for ash quenching. There-
fore, volatile organics and inorganics
may be released in these vent gases.
Characterization of emissions is need-
ed to define control technology re-
ments.
Characterization of this waste stream
is required to define control tech-
nology requirements. Further treat-
ment 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 combustile con-
stituents. 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.
Fugitive
emissions
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
sulfite, carbon monoxide, and hydro-
gen cyanide.
These emissions will determine the
extent of workers exposure to
hazardous species and define the
need for continuous area monitoring
of toxic compounds and personal pro-
tection equipment.
-------
Table A. DISCHARGES FROM LOW- AND MEDIUM-BTU GASIFICATION SYSTEMS
Operation
Discharge stream
source
Discharge
streams
Description
Coot
Remarks
Gas Purification
Particulate removal
CO
Gas quenching and
cooling
Acid gas removal
Collected
particulate
matter
Spent quench
liquor
Tall gases
Spent sorbents
and reactanta
There are little data on the
characteristics of this solid
waste stream. This stream will
contain unreacted carbon, sulfur
species, organics, and trace ele-
ment.
There are little data on the com-
position of this stream* however,
current data indicates that there
are significant quantities of sus-
pended and dissolved organics
(primarily phenols) and inorganics
present in this stream.
There are little data on the com-
position of these tail gases. These
gases will contain sulfur species
and hydrocarbons.
No data have been reported on these
streams. These streams will contain
hazardous species such as cyanides,
heavy metals, organics, etc. 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 fur-
ther treatment is necessary before
disposal. Current data indicate 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 scream will
determine the type of water pollution
control techniques required to treat
the spent quench liquor. These con-
trol 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.
-------
processes can be handled using available techniques for con-
trolling coal dust emissions, disposing of mineral wastes, and
handling runoff waters from storage piles. However, less costly
or, in some cases, more efficient controls are needed.
The control of air emissions from coal dryers, briquetting
and partial oxidation processes may present more difficult pro-
blems because of the volatile hydrocarbons and trace metals
which can be liberated as the coal is heated. The exact char-
acter of these materials has not be determined as far as their
potential toxicities are concerned. Hence, the limit to which
they must be controlled and the adequacy of available control
technology have not been determined.
Gasification
The coal gasification operation appears to be the most
serious source of potential gasification system pollution pro-
blems. Experience with coke ovens and other work with thermal
processing of coal has demonstrated that organic emissions from
the gasifier can be expected to contain toxic and carcinogenic
materials. For all systems, the feeding of coal and the with-
drawal of ash provide opportunities for the escape of coal or
ash dust and hydrocarbons which, being products of the thermal
processing of coal, must be considered to be potentially toxic.
These problems are similar for all gasifiers, but slagging
gasifiers because of their low production of tars and conden-
sible hydrocarbons may prove to be an easier pollution control
38
-------
problem at the inlet and outlet points. Also, it is certain
that gasifiers and associated equipment will be sources of fugi-
tive leaks from pump seals, flanges and the like. This leakage,
unless controlled to adequate levels, can be hazardous. High
temperature and pressurized gasifiers may be more difficult to
control from the standpoint of fugitive emissions.
Gas Cleaning
The gas cleaning operations also appear to present diffi
cult control problems. The particulate collection and gas
cleaning steps will, for many systems, produce ash and water
contaminated with organics and inorganics, many of which are
toxic. All sulfur collection systems will produce a bleed
stream of contaminated sorbent liquid. In addition volatiliza-
tion or carryover of sorbent can be a potential source of air
pollution.
The sulfur removal processes will also produce fugitive
emissions which are similar to those generated during gasifica-
tion. Where Glaus plants are used for sulfur recovery the tail
gases are a potential source of pollution. Pollution control
needs for the gas cleaning area are poorly defined and more
work-is needed to support judgments on the adequacy of available
control technology.
In summary, it can be said that work to better define
control technology is needed. It is apparent, however, that
work to keep the cost of control equipment (which is expected
39
-------
to amount to 10 to 25 percent of the total process cost) (3)
within tolerable limits will be needed. Experience with coke
ovens, coal preparation plants, power plants and related coal
processing operations indicate that given proper attention most
discharges from coal gasification systems should not produce
serious pollution. Development of in-depth understanding of
the character of the discharge streams and their potential for
harm to humans or the environment, is however, critical. Only
with such information available can adequate control methods be
developed and applied without jeopardy to the economic viability
and environmental acceptability of future systems.
Further details relative to the operating characteristics
and potential discharges from processes depicted in Figure 1
are presented in Appendix D.
40
-------
REFERENCES
1. Cavanaugh, E. C., W. E. Corbett, and G. C. Page, "Environmental
Assessment Data Base for Low/Medium-Btu Gasification Technology".
EPA-600/7-77-125a and b (NTIS # PB 274-844/AS and PB 274-843/AS)
November 1977.
2. Lacey, J. A., "The Gasification of Coal in a Slagging Pressure
Gasifier", Amer. Chem. Soc., Div. Fuel Chem., Prepr. October 1966.
3. National Research Council, National Academy of Science, "Assessment
of Low- and Intermediate-Btu Gasification of Coal". Washington,
D. C., 1977.
4. Magee, E. M., C. E. Jahnig, and H. Shaw, "Evaluation of Pollution
Control in Fossil Fuel Conversion Processes, Gasification; Section
1: Koppers-Totzek Process", EPA-650/2-74-009a, (NTIS # PB 231-675/AS)
January 1974.
5. Hess, Martin, "Aromonia: Coal vs Gas", Hydrocarbon Processing.
November 1976.
6. Putnam, A. A., E. L. Kropp, and R. E. Barrett, "Evaluation of
National Boiler Industry", Battelle - Columbus Laboratories.
October 1975.
41
-------
Appendix A
Environmental Assessment/Control Technology
Development Protocol
A-l
-------
ro
REGULATORY
HIQUIREMENTS
CURRENT PROCESS TECH
NOIOGY BACKGROUND
• PROCESS INFORMATION
• SCHEOUIIS
0 STATUS
• PRIORIIIESIORFUR
TH(RSTUDY
ENVIRONMENTAL OATA ACQUISITION
• EXISTING 0»!» f OR EACH PROCESS
• IDENTIFY SAMPLING AND «N»l YTI
CAl TECHNIQUES INCLUDING
IIOUSAVS
• TEST PROGRAM DEVELOPMENT
• COMPREHENSIVE VtMTI STREAM
CHARACIERIIAIION(LEVELS I II
Mil
• INPUT OUTPUT MATERIALS
CHARACTERIZATION
• CO»TROl ASSAYS
CURRENT ENVIROMIENTAL
IAHOROUNO
• rOTEDTIAl POILUIANTS
ANDIWACTSINAll
MEDIA
• DOSE (REVOKE DATA
• FED/STATE sins CRITERIA
• TRANSPORT MOOEIS
• SUMHARIIE INDUSTRY
RELATED OCCUPATIONAL
HEALTH/EPIDEMIDlOGICAl
LITERATURE
ENVIRONMENTAL OUECIIVES
DEVELOPMENT
• ESTAILISHPERMISUILE
MEDIA CONC IOR CONTROL
DEVELOPMENT GUIDANCE
ODEFINI DECISIONCRIIIRIA
FOR PRIORIII2IIIC SOURCES
PROILEMS
• OIIINI EMISSION COALS
• PRIORITItl POLLUTANTS
• NONPOLLUIANI IMPACT
COALS
• BIOASSAVCRIURIA
CONTROL TECHNOLOGY
DEVELOPMENT
0ENGINIERINO ANALYSIS
• IASIC AND APPLIED PROCESSES
DEVELOPMENT
• SPECIFIC PROCESS DEVELOP
MENT AND EVALUATION
CONTROL TECHNOLOGY ASSESSMENT
• CONTROL SYSTEM AND DISPOSAL
OPTION INFORMATION AND OE
SIGN PRINCIPLE
• CONTROL PROCESSPOLLUIION
AND IMPACTS
• PROCESS ENGINEERING 'Oil u!
ANTfCOSTSENSITIVITY SIUDI1S
• ACCIDENTAL RELEASE MALFUNC
HON. TRANSIENT OPERATION
STUDIES
• FIELD TESTING IN RELATED
APPLICATIONS
• DEFINE USTCONIHOl IICH
NIOUE FOR EACH GOAL
• POLLUTANT CONTROL SYSTEMS
STUDIES
• CONTROL TECHNOLOGY RIO
PLANS AND GOALS
ENVIRONMENTAL ALTERNATIVES ANALYSES
SELECT AND APPLY
ASSESSMENT ALTERNATIVES
ALTERNATIVE SETS OF MULTI
MEDIA ENVIRONMENTAL GOALS
(MEG-SI
• IISI TECHNOLOGY
• EIISIIKGAMIIINTSIDS
0ISIIMMID KHMISSHII
CONC
^NATURAL BACKGROUND
lEllMINAIIONOF DISCHARGE!
• SIGNIFICANT DETERIORATION
• MINIMUM ACUTE TOXICITV
EIFLUENI
00UANTIFIEOCON1ROI MUD Ml [is
00UANTII110 CONTROL AUiHN»TivfS
fOUANTIFItOMIOIA OEGRAOAIION
ALTERNATIVIS
• OUANTIFItO hOMF-OUUf AfcT KMCTS
ANOSITIHG CRITIfllA Al TIR*IATIVtS
0 DEFINED RESEARCH DAI A BASE * 0"
STANDARDS
INVIRONMENIAl ENGINEERING
ENVIRONMENTAL SCIENCES
^ENVII
TECI
IRONMENTAL SCIENCES
ECHNOLOGV TRANSFER
ENVIRONMENTAL SCIENCESRtO
• HEALTH/ECOLOGICAL irricts
RESEARCH
• TRANSPORI/IRANSIORMAIION
RESEARCH
H ENVIRONMENTAL ENCRC I
TECHNOLOGY TRANSFER |
,
MEDIA OIGRADATION AND
HtAlTH ECOLOClCAt
IMPACTS ANAlVSlS
^ AIR #*!( R AND I ANU
QUAtllV
AND DtATHS
• (COlOCV HllftliO
IfflCTS
I ou ANT IF it i) iff ins
AlURNATlVES
Figure A-l Emdrormental Assessment/Control Technology Development Protocol
-------
Appendix B
Nomenclature Definitions for Energy Technologies
B-l
-------
Nomenclature for Energy Technologies
1. Energy Technology
An energy technology is made up of systems which are
applicable to the production of fuel, electricity, or chemical
feedstocks from fossil fuels, radioactive materials, or natural
energy sources (geothermal or solar). A technology may be
applicable to extraction of fuel, e.g., underground gasification;
or processing of fuel, e.g., low-Btu gasification, light water
reactor, conventional boilers with fuel gas desulfurization.
2. Operation
An operation is a specific function associated with a
technology and consists of a set of processes that are used to
produce specific products from certain raw materials. For
example, the operations for low/medium-Btu gasification tech-
nology are coal pretreatment, coal gasification, and gas
purification. The processes used in each of these operations
are:
Coal Pretreatment - drying, partial oxidation, crushing
and sizing, briquetting, and pulverizing.
Coal Gasification - fixed-bed/pressurized/slagging;
fixed-bed/pressurized/dry ash; entrained-bed pressurized/
slagging; fixed-bed/atmospheric/dry ash; fluid-bed/
atmospheric/dry ash; and entrained/bed/atmospheric/slagging.
Gas Purification - wet or dry particulate and tar removal,
gas quenching, and acid gas removal.
B-2
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3. Process
Processes are basic units that make up a technology. A
process is used to produce chemical or physical transformations
of input materials into specific output streams. Every process
has a definable set of waste streams which are, for practical
purposes, unique. The term "process" used without modifiers
is used to described generic processes. Where the term "process"
is modified (e.g., Lurgi process), reference is made to a
specific process which falls in some generic class consisting of
a set of similar processes. For example, a generic process in
low/medium-Btu gasification technology is the fixed-bed/
atmospheric/dry ash gasification process. Specific processes
which are included in this generic class are Wellman-Galusha,
Woodall-Duckham/Gas Integrale, Chapman (Wilputte), Riley-Morgan,
Foster Wheeler/Stoic and Wellman-Incandescent.
4. Process Module
A representation of a process which is used to display
process input and output streain characteristics. When used with
other necessary process modules, they can be used to describe a
technology, a system or a plant. One example of the "process
module" approach to environmental studies of energy technologies
involved study of emissions from petroleum refining. A
description was developed for the basic processes which make up
a petroleum refinery, e.g., atmospheric distillation, catalytic
B-3
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cracking, etc. Information on air emissions, as a function of
throughput, was collected as descriptive information for each
process module. Individual process modules were assembled to
describe plants with the process configuration which is typical
of specific areas of the country, e.g., a refinery in the
Southwest United States, which maximized gasoline output and
another in the Northeast United States, which produced more
distillate fuel. Data on emissions and weather and air quality
information from specific locations, for assumed plant sites,
were used for diffusing modelling studies aimed at predicting
air pollution, which would be experienced if a refinery was in
operation at the assumed location.
5. Auxiliary Process
Processes, associated with a technology, which are used for
purposes that are in some way incidental to the main functions
involved in transformation of raw materials into end-products.
Auxiliary processes are used for recovery of by-products from
waste streams, to furnish necessary utilities, and to furnish
feed materials such as oxygen which may or may not be required
depending on the form of the end-product, which is desired.
For example, some auxiliary processes for low/medium-Btu gas-
ification technology include a) oxygen production used to
produce medium-Btu gas, b) the Glaus process used to recover
sulfur from gaseous waste streams, and c) the Phenolsolvan process
used to recover phenols from liquid waste streams.
B-4
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6. Sys tern
A specified set of processes that can be used to produce a
specific end-product of the technology e.g., low- and medium-Btu
gasification. The technology is comprised of several systems.
The simplest system is producing combustion gas from coal using
a small fixed-bed, atmospheric, dry ash gasifier coupled with a
cyclone. One of the most complex systems has very large
gasifiers with high efficiency gas cleaning being used to produce
a fuel clean enough to be fired in the gas turbines of a combined-
cycle unit for production of electricity.
7. Plant
An existing system (set of processes) that is used to produce
a specific product of the technology from specific raw materials.
A plant may employ different combinations of processes but will
be comprised of some combinations of processes which make up
the technology. For example, the Glen-Gery Brick Company low-
Btu gasification facilities are plants used to produce combustion
gas from anthracite coal.
8. 'Input Streams
Materials that must be supplied to a process for performance
of its intended function. Input streams will include primary
and secondary raw materials, streams from other processes,
chemical additives, etc. For example, the input streams to a
B-5
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Lurgi gasifier consist of sized coal, leek hopper filling gas,
oxygen, steam, and boiler feedwater. For auxiliary processes
a waste stream from which a by-product is recovered is an input
streams.
9. Output Streams
Confined discharges from a process which can be products,
waste streams, streams to other processes, or by-products. For
example, output streams from a Lurgi gasifier include coal
feeder vent gases, ash hopper vent gases, wet ash, steam blow-
down, and crude medium-Btu gas.
10. Raw Materials
Raw materials are feed materials for processes. They are
of two types: 1) primary raw materials that are used in the
chemical form in which they were taken from the land, water, or
air, and 2) secondary raw materials that are produced by other
industries or technoloiges. For example, primary raw materials
for low/medium-Btu gasification technology include coal, air,
and water. Secondary raw materials include fluxes, makeup
solvent, catalysts, etc.
11. Process Streams
Process streams are output streams from a process that are
input streams to another process in the technology. For example,
B-6
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the crude medium-Btu gas from the Lurgi gasification process is
the feed (input) stream to the tar and particulate removal quench
process.
12. Products
Process output streams that are marketed for use or consumed
in the form that they exit the process. For example, the product
from low-Btu gasification technology is the low-Btu gas exiting
the final gas purification process.
13. By-Products
By-products are auxiliary process output streams that are
produced from process waste streams and are marketed or consumed
in the form in which they exit the process. For example, tar
is a by-product produced by certain low-Btu gasification
facilities. It may either be consumed in a tar boiler or sold.
14. Waste Streams
Waste streams are confined gaseous, liquid, and solid
process output streams that are sent to auxiliary processes for
recovering by-products, pollution control equipment or final
disposal processes. Unconfined "fugitive" discharges of gaseous
or aqueous waste and accidental process discharges are also
considered waste streams. The tail gas from an acid gas
removal process is an example of a waste stream in low/medium-Btu
B-7
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gasification technology. This stream can be sent to an auxiliary
process, to recover the sulfur as a by-product.
15. Source
Equipment which discharges either confined waste streams
(solids, liquid, gaseous or combinations) or significant
quantities of unconfined, potentially polluting substances in
the form of leaks, spills, and the like. Examples of sources
include gasifier coal feed lock hoppers which discharge emis-
sions during coal feeding, the Glaus reactor which recovers
sulfur and discharges tail gases containing polluting sulfur
compounds.
16. Effluent Streams
Confined aqueous process waste streams which are potentially
polluting. These will be discharged from a source.
17. Emission Streams
Confined gaseous process waste streams which are potentially
polluting. These will be discharged from a source.
18. Fugitive Emissions
Unconfined process associated discharges, including
accidential discharges, of potential air pollutants. These may
escape from pump seals, vents, flanges, etc., or as emissions
B-8
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in abnormal amounts when accidents occur and may be associated
with storage, processing, or transport of materials as well as
unit operations associated with a process. They will escape
from a source.
19. Fugitive Effluents
Unconfined process associated discharges, including
accidental discharges, of potential water pollutants which are
released as leaks, spills, washing waste, etc., or as effluents
in abnormal amounts when accidents occur. These may be asso-
ciated with storage, processing, or transport of materials as
well as unit operations associated with industrial processes,
and may be disposed of to municipal sewers, and can lead gen-
eration of contaminated runoff waters. They will escape from a
source.
20. Accidental Discharge
Abnormal discharges (solid, liquid, gaseous or combinations)
which occur as a result of upset process conditions.
21. Unit Operation
Unit operations, like processes described above, are
employed to take input materials and perform a specific physical
or chemical transformation. The equipment making up a unit
operation may or may not have one or more waste stream(s). A
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process is made up of one or more ur.it operations which have at
least one source of waste stream(s) . Example of v:nit operations
are: distillation, evaporacion, crushinr,, screening, etc.
22. Final Disposal Processes
Processes that are used to ultimately dispose of liquid and
solid wastes from processes, auxiliary processes, and control
equipment employed in a technology. Examples of final disposal
processes are landfills and evaporation ponds.
23. Control Equipment
Equipment such as electrostatic precipitators, wet scrubbers,
adsorption systems, etc., whose primary function is to minimize the
pollution to air, water or land, resulting from process discharges.
While the collected materials may be sold, recycled or sent to
final disposal, control equipment is not essential to the economic
viability of the process. Where such equipment is designed to be
an integral part of a process, e.g. scrubbers which recycle process
streams, they are considered a part of the basic process.
24. Residuals
Gaseous, liquid, or solid discharges from control equipment
and final disposal processes. Examples of residuals include
gaseous emissions from control equipment,such as scrubbers,
cleaning the tail gases from an auxiliarv nrocess (e.g. a Glaus
sulfur recover" unit) nnd vapors from an evaporation pond.
B-10
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APPENDIX C
POPULATION OF LOW/MEDIUM-BTU GASIFIERS
Csslfler eyp«
Casltier name
Licensor/Developer
Status
Fixed-Bed. Dry Aah
Lurgl
Wellsum-Calusha
Chapman (Wllputte)
Wcodall-Duckham/Gaa Integrals
Rlley Morgan
Pressurized Wellman-Galusha
(MERC)
Foster Wheeler/Stoic
Kilngas
Kellogg Fixed Bed
CEGAS
Conaol Fixed Bed
IFE Two Stage
Kerpely Producer
Marlachka
Plntsch Rlllebrand
U.C.I. Blue Water Gas
Power Gas
Wellman Incandescent
BCR/Kalser
Fixed-Bed. Slagging Aah
BCC/Lurgl Slagging Gaslfler
GFERC Slagging Gaslfler
Luena
Thyssen Galocsy
American Lurgl Corp. (USA)
McDowell Wellman Engr. Co. (USA)
Wllputte Corp. (USA)
Woodall-Duckhan, Ltd. (USA)
Rlley Stoker Corp. (USA)
Morgantown Energy Research
Center/ERDA (USA)
Foster Wheeler Energy Corp. (USA)
Allls Chalmers Corp. (USA)
M. W. Kellogg Co. (USA)
General Electric Research and
Development (USA)
Consolidation Coal Co.
(DSA)
International Furnace Equipment
Co., Ltd.
Bureau of Mlnes/ERDA (USA)
Unknown
Unknown (Germany)
U.C.I. Corp./DuPont (USA)
Power Gas Co. (USA)
Applied Technology (USA)
Unknown
Present commercial operation
Present commercial operation
Present commercial operation
Present commercial operation
Present demonstration unit testing;
commercially available
Present development unit testing
Demonstration unit planned
Present development unit testing;
erclally available
Present development unit testing
Present development unit testing
Present development unit testing
Past commercial operation
Past commercial operation
Past commercial operation; anthracite
or coke only
Past commercial operation
Past commercial operation; coke only
Past commercial operation
Present commercial operation
Paat development unit testing
British Gas Council (GB)
Lurgl Mlneraloltechnlk (W. Germany) Present development unit testing
Grand Forks Energy Research
Center/ERDA (USA)
Unknown
Unknown
Present development unit testing;
lignite only
Past commercial operation; coke only
Past commercial operation; coke only
C-l
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POPULATION OF LOW/MEDIUM-BTU GASIFIERS
(concicua'd)
Caslfler type
Castfier name
Licensor/Developer
Status
FluldUed-Bed, Dry Ash
Hlnkler
Hygas
Synthane
Hydrane
Cogas
Exxon
BCR Lov-Btu
C02 Acceptor
Electrofluldic Gasification
LR Fluid Bed
HRI Fluldized Bed
BASF-Flesch-Deoag
CECB Harchwood
Heller
Fluldlzed-Bed, Agglomerating Aah
U-Ga»
Battelle/Carblde
Hestlnghouse
City College of NY Hark 1
Two-stage Fluldized
1CI Moving Burden
Entralned-Bed. Dry Ash
Garrett Flash Pyrolysls
Blanchl
Davy Powergas Co. (USA)
Institute of Gas Technology (USA)
Pittsburgh Energy Research
Center/ERDA (USA)
Pittsburgh Energy Research
Center/ERDA (USA)
Cogas Development Co. (USA)
Exxon Corp. (USA)
Bituminous Coal Research (DSA)
Consolidation Coal Co. (USA)
Iowa State Onlv./ERDA (DSA)
Unknown (Germany)
Hydrocarbon Research Inc. (USA)
Badlsche AnilIn und Soda Fabrlk
(West Germany)
Unknown
Unknown (Germany)
Institute of Gas Technology (USA)
Battelle Memorial Institute (USA)
Uestlnghouse Electric Corp. (USA)
Hydrocarbon Research Inc./
A.M. Squires (USA)
British Gas Council (England)
Imperial Chemical Industries, Ltd.
(England)
Present commercial operation
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Past commercial operation
Past development unit testing
Past development unit testing
Past development unit testing
Past development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Past development unit testing
Garrett Research and Development Present development unit testing
Co. (USA)
Unknown (France)
Past development unit testing;
lignite only
C-2
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POPULATION OF LOW/MEDIUM-BTU GASIFIERS
Caslfier type
Gaslfler none
Licensor/Developer
Status
Panlndco
USBM Annular Retort
USBM Electrically Heated
Entrained-Bed. Slagging Ash
Koppera-Totzek
Bl-Ca«
Texaco
Coalex
PAMCO/Foster Wheeler
Combustion Engineering
Brlghaa Young University
Babcock and Wilcoi
Ruhrgas Vortex
ICT Cyclonlzer
Inland Steel
USBM, Morgontovn
Great Northern Railway
FRS Cyclone
Molten Media. Slagging Ash
Kallogg Molten Salt
Atgu/Patgas
Rockgas
Runnel Single Shaft
Sun Gasification
Otto-Runnel Double Shaft
Unknown (France)
Bureau of Hlnes/EROA (USA)
Bureau of Hlncs/ERDA (USA)
Koppers Co. (USA)
Bltunlnous Coal Research, Inc.
(USA)
Texaco Development Corp. (USA)
Inex Resources, Inc. (USA)
Pittsburgh and Midway Coal Co./
Foster Wheeler (USA)
Combustion Engineering (USA)
Brlghaa Young University/
Bituminous Coal Research (USA)
The Babcock and Wilcox Co. (USA)
Ruhrgas A. G. (West Germany)
Institute of Gas Technology (USA)
Inland Steel Co. (USA)
Morgantown Energy Research
Center/ERDA (USA)
Great Northern Railway Co. (USA)
Unknown (England)
M. V. Kellogg Co. (USA)
Applied Technology Corp. (USA)
Atomics International (USA)
Union Rhelnlschc Braun Kohlen
Kraftstoff A. G. (West Germany)
Sun Research and Development Co.
(USA)
Dr. C. Otto and Co.
Past development unlc testing;
lignite only
Past development unit testing;
lignite only
Past development unlc testing
Present comnerclal operation
Present development unit testing
Present development unit testing
Present development unit testing;
commercially available
Present development unit testing
Present development unit testing
Present development unit testing
Past commercial operation
Past commercial operation
Past development unit testing
Past development unit testing
Past development unit testing
Past development unit testing
Past development unit testing
Present development unit testing
Present development unit testing
Present development unit testing
Past commercial operation
Past development unit testing
Past development unit testing
C-3
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Appendix D
Description of Processes for Low- and
Medium- BTU Gasification Systems
Page
No. 1 - Coal Drying D-2
No. 2 - Partial Oxidation D-3
No. 3 - Crushing and Sizing D-4
No. 4 - Pulverizing D-5
No. 5 - Briquetting D-6
No. 6 - Fixed Bed Pressurized Slagging D-7
No. 7 - Fixed Bed Pressurized Dry Ash D-9
No. 8 - Entrained Bed Pressurized Slagging D-ll
No. 9 - Fixed Bed Atmospheric Dry Ash D-13
No. 10 - Fluid Bed Atmospheric Dry Ash D-15
No. 11 - Entrained Bed Atmospheric Slagging D-17
No. 12 - Quench and Scrub Tar/Particulate (Pressurized) D-19
No. 13 - Dry Particulate Collection (Pressurized) D-20
No. 14 - Quench and Scrub Tar/Particulate (Atmospheric) D-21
No. 15 - Dry Tar and Particulate Removal (Atmospheric) D-22
No. 16 - Dry Particulate Removal (Atmospheric) D-23
No. 17 - Quench and Scrub Particulate (Atmospheric) D-24
No. 18 - Quench (Pressurized) D-25
No. 19 - Quench (Atmospheric) D-26
No. 20 - Sulfur Removal (Pressurized) D-27
No. 21 - Sulfur Removal (Atmospheric) D-30
D-l
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COAL PREITCEATMENT
Coal Drying Process No. 1
1. General Information
Coal drying may be a necessary step in producing gas from coal.
Coals with high moisture content, such as certain lignites, should generally
be dried until the coal moisture content is between 30 to 35%. Two types of
gasification processes that are more sensitive to coal moisture are entrained-
bed (Koppers-Totzek) and fluidized-bed (Winkler) gasifiers. Koppers-Totzek
gasifiers require a coal moisture content of less than 8% while Winkler gasifiers
specify less than 30% moisture for lignite coals and less than 18% for higher
grade coals.
2. Process Information
Thermal drying of coal is accomplished by contacting the coal with hot
combustion gases at temperatures around 755°K (900°F). Various types of thermal
dryers including rotary, cascade, reciprocating screen, conveyer, suspension
and fluidized-bed, are used. Fluidized-bed dryers are most frequently used
because of their high gas-solid contacting efficiency.
3. Waste Streams
Off-gases from the dryer are the only significant waste stream.
Bnissions may contain coal dust, volatile organics and combustion products
((XL, H20, S02, NO .) Particulates are usually controlled by cyclones or
baghouses. Scrubbers may be needed to reduce gaseous emissions such as SO*
The volatile organics are known to be potentially toxic. If they are present
in high concentrations afterburners may be needed for control.
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COAL PRETREATMENT
Partial Oxidation Process No. 2
1. General Information
For high caking coals, partial oxidation may be necessary to reduce
the coal caking tendencies for certain gasifiers. Gasification processes
that require coal with low caking tendencies are two-stage, fixed-bed,
atmospheric gasifiers (Wbodall-Duckham/Gas Integrale, Foster Wheeler/Stoic,
and Wellman Incandescent); fluidized-bed, atmospheric gasifiers (Winkler)
and single-stage, fixed-bed gasifiers without an agitator (Lurgi.) The most
stringent coal caking specifications are for two-stage, fixed-bed, atmospheric
gasifiers. For example, a Woodall-Duckham/Gas Integrale gasifier requires a
coal having a free swelling index of less than 2.5 and any coals having a higher
index would require treatment.
2. Process Information
Partial oxidation is carried out in thermal dryers (cascade, rotary,
reciprocating screen, conveyer, suspension, and fluidized-bed.) Conditions are
controlled so that coal drying and partial oxidation is accomplished
simultaneously.
3. Waste Streams
See Process 1.
D-3
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COAL PRETREATMENT
Crushing and Sizing Process No. 3
1. General Information
Crushing and sizing steps are used to produce sized coal feedstocks
for fixed-bed gasifiers (Lurgi, Wellman-Galusha, etc.) Particle sizes required
are generally in the range of 2-50 nm (0.1-2.0 inches) in diameter. Excessive
quantities of fines cannot be tolerated in fixed-bed systems because they can
cause excessive bed pressure drop, poor gas distribution and/or channeling.
Oversized coal particulates can reduce the maximum throughput of fixed-bed
gasifiers because of their lower reactivity (low surface area/volune ratio.)
Oversized coal particles are recycled to the crusher. Fines are rejected
and burned separately or briquetted.
2. Process Information
A wide variety of size-reduction equipment is available. The basic
types include jaw crushers, gyratory crushers, roll crushers, hammer mills and
ball mills. The sizing equipment employed includes gravity types (sieves and
screens) or centrifugal-type such as air classifiers.
3. Waste Streams
Waste streams include mineral wastes which are sent to landfill and
fugitive emissions which are controlled using hoods and cyclones or baghouses
for collection. Collected fines are combined with those rejected from crushing
and sizing.
D-4
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COAL PRmEATMENT
Pulverizing Process "fo. 4
1. General Information
Coal pulverizing is used to produce a coal feed for fluidized-
bed gasifiers (Winkler) and entrained-bed gasifiers (Koppers-Totzek.) Typical
coal size specifications for fluidized- and entrained-bed gasifiers are less than
9.4 rim (0.38 inches) and less than 0.07 run (0.003 inches) respectively.
2. Process Information
Pulverizing equipment which is used includes hammer mills, cage mills,
impactors and ball mills.
3. Waste Streams
The principal waste stream from pulverizing is fugitive emissions of
coal dust. These are controlled by using hoods and conventional particulate
control equipment (cyclones, baghouses. wet scrubbers) and ducts can be used
to collect and transport coal dust from the pulverizing oneration to conventional
control equipment such as cyclones, baghouse filters, or scrubbers. The coal
fines are consigned on-site as a fuel or recycled to the pulverizer.
D-5
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COAL PRETREATMENT
Briquetting Process No. 5
1. General Information
Excessive quantities of coal fines cause excessive bed pressure drop,
severe channeling, or poor gas distribution in fixed bed gasification processes.
Therefore, coal fines rejected from crushing and sizing or collected from
fugitive dusts must be compacted into briquettes which are of suitable size for
feed to a gasifier or used as fuel.
2. Process Information
To produce briquettes, coal fines are usually fed between a pair of
mated rolls with recessed surfaces. The fines are compacted in these recessed
areas as the rolls come together. A binder such as asphalt or tar may or may
not be needed in order to give the briquette sufficient structural strength.
The briquette may also need to be baked in hot gases to nrovide additional
structural strength. The nature of the operations needed will be determined by
characteristics of the coal. Typical equipment vrould include conveyor, cascade,
or reciprocating screen thermal dryers. Sizes of briquettes to be fed to fixed-
bed gasifiers range from 3.2 to 38.1 mm (0.13 to 1.5 inches).
3. Waste Streams
Waste streams from the briquetting process are air emissions consisting
of coal dust and, if baking is involved, volatile coal components. The coal dusts
are collected in conventional control equipment and is recycled to the briquetting
operation, or used as fuel. Hydrocarbon control may be required if the briquettes
are baked and volatile, potentially toxic hydrocarbons are emitted in sufficient
amounts. These can be controlled by afterburners or an adsorption process.
D-6
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GASIFICATION
Fixed-bed, Pressurized Process No. 6
Slagging, Gasifier
1. General Information
Experimental work on fixed-bed, pressurized, slagging ^asifiers has been conducted
by the U.S. Energy Research and Development Administration at their Grand Forks
Energy Research Center and by the British Gas Corporation which is working with
Lurgi Mneraloltechnik Gmbh. At Grand Forks, N.D. a pilot plant with capacity
of 40-190 g/sec (300-15001b/hr) was operated from 1958 to 1965 was reactivated
in 1977. This unit is operated solely to produce research data, and scale-up
for demonstration purposes is not anticipated. The British Gas Corp. operated
a pilot plant with capacity of 0.5 to 1.3 Kg/sec (4000-10,000 Ib/hr) from 1955
to 1964 and started up a demonstration plant in 1976. No operating data are
available for the demonstration unit.
2. Process Information
The process is operated with a bed temperature of around 1500°K (2300°F) depending
on the ash fusion temperature of the coal, and at pressures on the order of 2.07
to 2.76 MPa (300-400 psia). Coal is fed intermittently through a pressurized
lock hopper. Malten ash is drained into a water quench bath and slag lock. The
slag lock is discharged periodically. The raw gas is quenched and cooled in a
scrubber-waste heat boiler combination.
3.. Waste Streams
Waste streams with potential for pollution are as follows;
1) Vent gases (containing raw gas particulates, tars, phenols, ammonia)
which escapes from the coal feeder.
2) Wet ash and contaminated water discharged from the ash lock hopper.
3) Quench water and condensate from the waste heat boiler used in connection
with raw gas cooling. These waste waters contain tars, phenols, and
particulate matter.
D-7
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4) Slowdown water from the slag lock hopper water recirculation system.
Contaminates would include soluble ash components and impurities that
might he introduced with the make-up water.
5) Vent gases from the ash-lock hopper water recirculation system.
The high temperature of operation tends to reduce the amount of tars and oils
exiting with the ash. The lower temperatures in the upper zones do however
generate organics which leave with the raw gas. It is expected however that the
amount of organics produced will be less than those produced by low temperature
systems.
The composition of the blowdown water and vent gases from the slag lock hopper
water system will depend on overall water management practices. If make up water
contains impurities such as organics from other parts of the operation they will
exit with these streams.
The process condensate and quench water will contain significant amounts of tars,
condensible hydrocarbons, particulates, sulfur compounds and other constituents of
the raw gas stream. Processing for removal of by-products and intensive treatment
of any discharge waters will be needed.
D-8
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GASIFICATION
Fixed-bed, Pressurized Process No. 7
Dry-ash, Gasifier
1. General Information
Two fixed-bed, pressurized, dry ash gasifiers have been offered cotrmercially or are
under development. Lurgi Mineraloltechnik Gmbh has offered such gasifiers commercially
since 1936. Over 50 conmercial installations are being operated to produce
synthesis gas or medium-Btu fuel gas. The units range in capacity from about
0.6 to 6.0 Kg/sec (2.4 to 24 ton/hr) of coal. A pressurized Wellman-Galusha oilot
plant with capacity of 0.2 Kg/sec (1500 Ib/hr) has been in operation since 1958.
2. Process Information
These units operate below the fusion point of the ash fed. For the Lurgi plants
and the Wellman-Galusha pilot the respective bed temperatures of 1250-1650°K (1800-
2500°F) and 1600-1650°K (2400-2500°F) have been reported. Gas outlet temperatures
are reported to be 730°K (850°F) for the Lurgi and 750-920°K (900-1200°F) for the
Wellman-Galusha. The coal is fed intermittently through pressurized two-chamber
locks. The ash is also intermittently removed through a pressurized lock which
receives the ash from the gasifier and introduces it into cooling water sprays
or quench water.
3. Waste Streams
Waste streams with potential for pollution are as follows;
1) Vent gas from the coal feeder which contain all components of the raw
gas stream, i.e., tars, condensible hydrocarbons, particulates, sulfur
compounds and anmonia.
2) Wet ash and contaminated water from the ash cooling or ash quench operations
will contain mineral matter from coal, carbon and possible some organics.
3) Vent gases from the ash cooling or ash quenching steps will contain steam,
raw gas, and particulates.
D-9
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4) Particulates, mostly fine coal contaminated with organics, will be
collected when cyclones are used for raw gas cleaning.
5) Contaminated water produced by gas quenching and as process condensate.
Will contain large amounts of tars, condensible hydrocarbons, and particulatt.
plus some reduced sulfur compounds, amnonia and other components of the
raw gas.
The relatively low temperature of operation results in tars and hydrocarbons being
present in some amount in all gasifier discharges. The vent gases from coal feeding
are recycled to the process or incinerated. Where inert lock-hopper pressurizing
gas is used and the raw gas content is low they may be sent to cyclones for
particulate removal and vented. Vent gases from the ash quench are passed through
steam condensers, and in some cases cyclones as well, for particulate removal and
are then vented or incinerated.
The gas quenching liquor and process condensate contains about 95% water and 570 of
the impurities indicated above. It is generally combined with other waste water
streams or it may be used for ash transport. The liquor is then sent to by-product
recovery and for treatment prior to discharge. The ash, after transport to
dewatering equipment may require careful disposal since it may contain trace
elements, and potentially toxic organic materials.
D-10
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GASIFICATION
Entrained-bed, Pressurized Process No. 8
Slagging ash, Gasifier
1. General Information
Two entrained-bed, pressurized, slagging gasifiers are presently under development.
Bituminous Coal Research has been operating a pilot plant with coal capacity
of about 1.3 Kg/sec (10,000 Ib/hr) for their Bigas process at Homer City,
Pennsylvania. Texaco Development Corp. has operated a pilot plant with coal
capacity of .5 kg/sec (4000 Ib/hr) for their similar process at their Montebello,
California laboratories.
Both plants feed coal in a water slurry and are felt to be capable of operation
with any type of coal using either air and steam or oxygen and steam to gasify the
coal.
2. Process Information
This process operates at high temperature and pressure with bed temperatures up
to 1900°K (3000°F) and reactor pressure up to 8.3 to 10.3 MPa (1200-1500psia). For
both the mode of operation is such that a minimum of tars and condensable hydrocarbons
will be produced in the raw gas. Both processes use a water quench in connection
with slag raioval and water scrub of the raw gas to remove impurities and reduce
the temperature. For the Texaco pilot plant slag removal and gas quenching is
carried out in a combined step.
3. _ Waste Streams
The principal waste streams with potential for pollution from the Bi-Gas and
Texaco gasifiers are as follows:
1) Vent gases from preparation of hot water slurries of pulverized coal
for process feed.
2) Gases lost with discharge of slag quench water from gasifier.
D-ll
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3) Waste water from slag quench and raw gas cleaning operations.
4) Waste water from the raw gas quench used to condition the gas for
sulfur removal.
Because the high temperature of operation for Bi-gas and Texaco tends to minimize
the tars and condensible hydrocarbons which will be lost from any of the above
points of discharge some of the pollution control problems may be simplified, e.g.,
it is likely that control of vent gases from coal feeding will involve onlv collection
of particulate using available technology. The presence of tars and condensibles
would make control of emissions at this point much more difficult. This would
apply also to gases lost during the discharge of slag.
The character of problems associated with the water discharges from the slag quench
and raw gas quench operations will depend largely on overall water management
practices. If water is recycled for quench of raw gas or to slag quench, build up
of contaminants may necessitate treatment and/or disposal of a bleed stream. Also
it is possible that high concentration of impurities could build up in water
recycled to either slurry preparation or quenching operations. This could lead to
volatilization of hydrocarbons which could exit with air emissions in objectionable
quantities.
D-12
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GASIFICATION
Fixed-bed, Atmospheric Process No. 9
Dry ash, Gasifier
1. General Information
Fixed-bed, atmospheric, dry ash gasifiers have been offered conmercially since the
1940"s. Five are still being sold (Wellman-Galusha, Vfoodall-Duckham, Chapman/
Willputte, Wellman Incandescent and Foster-Wheeler/Stoic. One pilot plant which
is a modification to earlier designs is also in operation (Riley/Morgan). These
gasifiers typically are about 10 ft. in diameter with throughput rates from about
0.3 to 1.3 kg/sec (2000 to 10,000 Ib/hr). Applications include production of
fuel for direct process heat, synthesis gas, and town gas.
2. Process Information
This type of gasifier operates below ash fusion temperatures with maximun bed
temperatures in the neighborhood of 1250-150QOK (1800-220QOF) and gas outlet
temperatures of 700-1100°K (800-1500°F). Three of the processes Cfoodall-Duckham,
Foster-Wheeler/Stoic, and Wellman Incandescent) represents variations in which two
product streams are withdrawn from the gasifier. One is a tar-free side stream with
a temperature around 920°K (1200°F); the other is an overhead stream which contains
volatiles and tar and exits at about 400°K (250°F). All processes may produce tars
and condensible hydrocarbons from which by-products are recovered. Particulates
entrained in the raw gas will be removed in part by cyclones and most of the balance
will be removed when the gas is scrubbed to quench it. Coal feed is introduced
intermittently through devices such as lock-hoppers or rotary feeders which are
designed to limit gaseous emissions. Ash is removed either dry by similar mechanisms
or "plowed" from a water sealed ash pan. Waste water is generated when water in the
raw gas is raoived as condensate and by water scrubbing employed to quench the raw
gas and remove contaminants.
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3. Waste Streams
Waste streams with potential for environmental pollution are as follows.
1) Vent gases escaping when coal is fed. This gas contains all materials
found in the raw gas, i.e., tars, particulates, condensible organics,
sulfur compounds, ammonia, and hydrogen cyanide.
2) Wet ash and contaminated water from ash cooling or ash quenching. Mineral
matter from coal, unreacted carbon, and possibly some organics either from
the gasifier or introduced by recycled waste water used for quenching,
may be contained in the wet ash.
3) Vent gases escaping when ash is discharged and quenched. Steam, oxygen,
particulates or volatile impurities introduced with the quench liquor
may be present.
4) Process condensate and raw gas quench water will contain tars, condensible
hydrocarbons, particulates, and other soluble components found in the raw gas
5) Particulate matter carried over in raw gas from the gasifier and collected
in cyclones will contain variable amounts of fine coal and ash contaminated
with tars and oils present in the raw stream.
The relatively low temperature of operation produces tars and condensible organics
which will tend to be present (along with sulfur compounds, ammonia, HCN, particulates
and raw gas) in any of the discharges from the gasifier. The gaseous wastes genera
will be recycled to the process, incinerated, or if amounts of contaminant are
small, simply vented.
The gas quench liquor and process condensates may contain all of the materials in
the raw gas and will be processed to recover by-products and will be given extensive
treatment before it is discharged.
The ash will contain mineral matter from the coal, unreacted carbon, and possibly
some organic residues coming from the gasifier or from the use of contaminated quench
water in ash handling. Other solid residues will be generated by removal of particulat
prior to the quench or from recovery of solids that are picked up by the quench water.
These residues may be contaminated with a considerable amount of potentially
hazardous organic materials and may require careful disposal.
D-14
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GASIFICATION
Fluidized-bed, Atmospheric Process No. 10
Dry ash, Gasifier
1. General Information
The Winkler gasifier is the only fluidized bed, atmospheric, dry-ash process now
being operated. It has been commercially available since 1926 and 36 units have
been built for production of synthesis or water gas. Seven are still in operation.
Capacity is around 4.2 to 4.5 Kg/sec (30,000-36,000 Ib/hr).
2. Process Information
The process is operated at bed temperature of HOCPK to 125QOK (1500 to 1800QF) and
outlet temperature of 978°K (1300°F). Coal is transferred continuously from a
nitrogen blanketed hopper to the gasifier, by a screw conveyor. Part of the ash
(30%) is removed on a continuous basis when it settles to the bottom of the fluidized
bed and is carried by way of screw conveyor to a nitrogen blanketed ash hopper.
Most of the remaining ash is carried out of the reactor with the product gas and is
subsequently collected in cyclones and sent to the ash hopper. The remaining ash
is washed out in the quench scrubber and a downstream electrostatic precipitator (ESP)
which is used for final cleanup. The ash from the scrubber is combined with that
collected by the ESP and sent to a settling tank. The underflow from the settler is
combined with dry ash from the ash hopper and slurried for transport to disposal or
the wet and dry ash streams may be processed separately.
3. _J_ Waste Streams
Waste streams with potential for pollution are as follows.
1) Vent gases from the coal bin contain nitrogen used to blanket the coal
and fine coal particulates.
0-15
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2) Vent gases from the ash hopper contain nitrogen used to blanket the ash to
prevent further reaction or combustion of the char in the ash, participates,
and possible product gas or gases evolved from the hot char.
3) Vent gases from the ash slurry settlings tank may contain any components
of the raw gas stream which are dissolved in the direct contact scrubber-
cooler and evaporate in the settler. Entrained droplets of gas quench
liquor or particulates from ash may also be present.
4) Process condensate and gas quench liquor will contain all soluble components
in the raw gas stream including fine particulates, ammonia, sulfur compounds,
trace elements, and nitrogen compounds.
5) Dry ash from ash hopper contains coarse ash from the bottom of the gasifier
and an intermediate size fraction removed from the raw gas in the waste
heat boiler or the cyclones. The ash may contain mineral matter in the coal,
10 to 30% unreacted carbon and some adsorbed components from the raw gas.
6) Ash slurry (25-3570 solids) from the settler contain fine ash not removed
by the waste heat boiler or the cyclones preceeding the scrubber-cooler.
The liquid portion is composed of process condensate and gas quench liquor
containing soluble components in the raw gas stream.
The vent gases from the coal feeder and ash handling can be cleaned of particulate
matter using conventional dry collectors. If gaseous contaminants are present in
significant amounts the gases can be recycled to the process or incinerated.
The wastewater (process condensate and quench liquor) is drawn off the settler.
It contains fine particulate and other components of the raw gas such as ammonia,
hydrogen sulfide, hydrogen cyanide, and trace elements but is largely free of
suspended tars and hydrocarbons. A similar wastewater may be produced by dewatering
the ash slurry.
The ash will contain mineral matter from the coal and 10-30% unreacted carbon which
must be utilized as fuel or as an adsorbent to avoid economic penalties associated
with loss of fuel and higher disposal costs for the waste.
D-16
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GASIFICATION
Entrained-bed, Atmospheric Process No. 11
Slagging, Gasifier
1. General Information
Two processes, the Kopper-Totzek (KT) and the Coalex involve entrained-bed, atmospheric
pressure, slagging ash gasification. The KT process has been offered conmercially
since 1952. Over forty are in operation producing synthesis gas. These process
around 3.8-6.3 Kg/sec (25,000-70,000 Ib/hr) of coal. The Coalex process has been
studied on pilot scale since 1976. A comnercial unit which would process about
0.8Kg/sec (6000 Ib/hr) of coal is being designed to provide process heat. Many
process details of the Coalex process are considered proprietary.
2. Process Information
The gasifiers now in operation have maximum bed temperatures of about 2200°K (3500°F)
and raw gas outlet temperatures of about 1750°K (2700°F). The high temperature of the
exit gases necessitates the use of heat recovery to maintain satisfactory thermal
efficiency. Coal is fed from a nitrogen blanketed coal bin, by screw conveyor, to
mixing nozzles where it is entrained in steam and oxygen and injected into the
gasifier through burners. Ash leaves the gasifier partly (50%) as molten ash
which flows down the walls of the gasifier into a slag quench tank and partly (50%)
as fine particles entrained in the exit gas which can be collected by filtering
or when the gas is scrubbed in the quench step.
3. Waste Streams
The waste streams with potential for environmental pollution are as follows;
1) Vent gases exit from the coal bin and from the slag quench. Gases from
the coal bin contains nitrogen and entrained coal dust. Off gases from
slag quench may contain any components of the raw gas.
D-17
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2) Contaminated water from raw gas scrubbing, condensate from the waste heat
boiler and gas cooler, and overflow from the slag quench tank in a combined
stream. Contains fine slag particles and components of the raw gas, e.g.,
particulates, ammonia, hydrogen sulfide, tract elements, and hydrogen
cyanide.
3) One slag discharge consisting of the larger particles in the slag quench
tank and a second which consists of fine slag particles collected in the
quench wash cooler and separated in a settling tank. Slag contains 5-55%
carbon, minerals in the coal and components of the raw gas.
The operating conditions in the gasifier are such that none of the exit streams
will contain significant amounts of tars, oils and other condensible organics.
The ash will be similar to that produced by a coal fired power plant. Waste
streams will require application of conventional technology for disposal. Sulfur
is generally the only by-product produced from the raw gas.
D-18
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GAS PURIFICATION
Quench and Scrub Tar Process No. 12
and Particulates
(Pressurized)
1. General Information
Combined gas quenching and scrubbing of tars and particulates from raw cjas
streams is used with all pressurized f ixed-bed-gasifiers. The process involves
the direct contact of the hot raw gas with aqueous or organic auench liauor which
removes tars, oils, and Darticulate matter and cools the raw gas to levels soecified
by the gas end-use or temperature requirements for the sulfur removal process. The
amount of cooling required usually ranges between -35 to -t-38°C (-30 to 100°F) The
choice of gas quenching and cooling equipment deoends in part upon the tar and
particulate content in the gas and whether or not sulfur removal is required. Waste
heat recovery equipment may be used. Where it is, heavy tars are removed before
the gas enters the waste heat recovery eauipment.
2. Process Information
Quenching is usually carried out in pressurized soray towers or packed columns.
3. Waste Streams
The only waste stream is spent quench liquor containing suspended and dissolved
tars, oils, coal fines, ash, dissolved gases, and raw gas bubbles containing t^S,
CO, NH3, HCN, etc. Control equipment used includes:
1) Filtration, flocculation-flotation and gravity seoarators to remove
suspended tars, oils, and solids.
2) Extraction, stripping, adsorption, biological and cooling tower oxidation
to remove dissolved constituents.
The solids and liquids from the primary treatment processes are burned or
recycled. Residuals from further processing go to controlled rinal disposal sites.
D-19
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GAS PURIFICATION
Dry Particulate Removal Process No. 13
(Pressurized)
1. General Information
Removal of dry particulates from pressurized raw gas is practiced in conjunction
with entrained-bed, pressurized, slagging gasifiers (Bi-Oas, Texaco) which produce
tar-free gases. Dry removal simplifies waste heat recovery and minimizes problems
of treating spent quench liquor.
2. Process Information
Cyclones or electrostatic precipitators can be used for pressurized dry
participate removal. Because of the high temperatures of the raw gas (800 to
1500°K, 1000 to 220C£F) and the potential problems associated with pressurized
ESP's, cyclones may be preferred. However, the low efficiency (60-90%) of cyclones
allows greater ar.ounts of particulate matter to enter the gas quenching process.
3. Waste Streams
The only waste stream is the collected particulate matter consisting of
coal fines and ash which may be landfilled or used as a fuel, depending on coal
content.
D-20
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GAS PURIFICATION
Quench and Scrub Tar Process No. 14
and Particulates
(Atmospheric)
1. General Information
Combined quench and scrubbing is used for fixed bed atmospheric gasifiers
except for Woodall-Duckham, Foster-Wheeler/Stoic and Wellman Incandescent which
employ dry tar removal (Process No. 15). This group includes Wellman-Galusha,
Chapman Willputte, Riley-Morgan. General information for pressurized quenching and
scrubbing (Process 12) is applicable to atmospheric systems.
2. Process Information
Quench is carried out in atmospheric spray towers or packed columns.
3. Waste Streams
Spent quench liquor is the only waste stream. Its comnosition will be similar
to that of the liquor from pressurized systems (Process No. 12). However, the
amount of dissolved gases, being directly proportional to pressure, will be lower.
Treatment of the liquor will be the same as for pressurized systems. Treatment
technology described under Process No. 12 would be employed.
D-21
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GAS PURIFICATION
Dry Tar and Particulate Removal Process No. 15
(Atmospheric)
1. General Information
Dry tar removal processes are used to collect tars in the top gas from two-
stage, atmospheric, fixed-bed, dry ash gasifiers (Wbodall-Duckham/f&s Integrale,
Foster Wheeler/Stoic, and Wellman Incandescent) and from some one-stage fixed-bed
gasifiers (Wellman-Galusha). In current gasification plants that process low
sulfur coal to generate gas for on-site combustion, the only gas purification process
used is a cyclone to remove coal fines, ash, and heavy tars entrained in the
raw gas. These plants have been in operation for a number of years. Dry removal
results in minimal gas cooling thereby increasing thermal efficiency. Dry
removal also simplifies treatment spent quench liquor by removing a major portion
of the tars and oils prior to quenching.
2. Process Information
The types of equipment currently used for dry tar removal are cyclones, where
low tar collection efficiency can be tolerated, and electrostatic precipitators
(ESP's) where high efficiencies are needed to meet the end-use specifications for
the product gas.
3. Waste Streams
The primary waste stream from this process is the collected tars and oils.
These are generally used as combustion fuel, but they may be sold for recovery of
by-products. Neither the tars or residues from by-product recovery can be safely
discharged into the environment because of the hazardous nature of the tar and
oil constituents.
D-22
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GAS PURIFICATION
Dry Particulate Removal Process No. 16
(Atmospheric)
1. General Information
Atmospheric dry particulate removal is used in connection with fixed-bed,
atmospheric, dry ash and entrained-bed, atmospheric gasifiers except where
particulate removal is combined with gas quenching. (Winkler, Koppers-Totzek and
Coalex gasifiers may be operated with particulate removal and quench combined or
in separate steps) Dry removal simplifies waste heat recovery and minimizes
problems associated with treatment of spent quench liquor.
2. Process Information
Discussion for pressurized particulate removal (Process 13) is also applicable
for atmospheric removal.
3. Waste Streams
Discussion for pressurized particulate removal (Process 13) is also applicable
for atmospheric removal.
D-23
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GAS PURIFICATION
Quench and Scrub Particulate Process No. 17
(Atmospheric)
1. General Information
Combined quenching and scrubbing of particulate is practiced for fluid-bed,
atmospheric, dry ash gasifiers where particulate collection is not a separate step.
(Winkler, Koppers-Totzek and Coalex gasifiers may be operated with combined or
separate quench and particulate removal steps).
This process is basically the same as the pressurized quenching and scrubbing
(Process No. 12). However, the gasification systems that utilizes this process
produce only trace amounts of tars in the raw gas. Atmospheric quenching and
scrubbing is generally used in conjunction with sulfur removal processes or a
specific end-use that require a low temperature less than about 311°K, 100°F gas.
2. Process Information
Quenching and scrubbing is carried out in spray towers or packed columns
operated at atmospheric pressure.
3. Waste Streams
The spent quench liquor is the only waste stream. Its composition will be
similar to spent liquors from pressurized quenching and scrubbing (Process No. 12)
except for a reduced tar and oil content.
D-24
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GAS PURIFICATION
Quench (Pressurized) Process No. 18
1. General Information
Pressurized quenching in an independent step is employed with entrained bed,
pressurized, slagging ash gasifiers (Bi-Gas, Texaco) which produce gases low in
tars which can be processed to gain the advantages associated with dry particulate
collection (Processs No. 13). It is used to reduce gas temperature for sulfur
removal and to remove trace amounts of tars and oils. Sulfur removal is required
for all end uses except direct combustion of gases produced from low sulfur fuels.
2. Process Information
Quenching is carried out in pressurized spray towers or packed columns.
3. Waste Streams
The only waste stream is the spent ouench liquor. Its composition will be
similar to that of the spent quench liquor from quenching and scrubbing operations
(Process No. 12) except that concentrations of tars, oils, and particulates
will be much lower. Treatment technology described under Process No. 12 would
be employed.
D-25
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GAS PURIFICATION
Quench (Atmospheric) Process No. 19
1. General Information
Atmospheric quenching in an independent step is employed for all atmospheric
systems in situations where gases are processed to gain advantages associated with
dry tar and particulate collection (Process No. 15, Process No. 16). It is used
to reduce the gas temperature for sulfur removal which is required for all end-uses
except for direct combustion of gases produced from low sulfur fuels.
2. Process Information
Quenching is carried out in spray towers and packed columns.
3. Waste Streams
The only waste stream is the spent quench liquor. The components of the liquor
will be similar to those in liquor from quenching and scrubbing operations (Process
No. 12). However, the amounts of heavy tars and particulate matter should be much
lower. The overall composition would be close to that from pressurized quenching
(Process No. 18) except that dissolved materials will be lower in atmospheric
systems. Treatment technology described under Process No. 12 would be employed.
D-26
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GAS PURIFICATION
Sulfur Removal Process No. 20
(Pressurized)
1. General Information
There are many commercially available processes for pressurized (1.4 to 6.9 MPa,
200 to 1000 psia) removal of reduced sulfur species such as F^S, COS, CS2, etc.
These processes have been used to clean natural gas and coke oven gases. One
process, the Rectisol Process, is currently being used in comnercial gasification
plants. Other pressurized sulfur removal processes vail probably be used in future
comnercial systems to clean low- and mediun-Btu gas. These are 1) physical solvent
processes (Rectisol, Selexol, Purisol, Estasolvan, and Fluor Solvent) that operate
between 2.1 and 6.9 MPa (300 to 1000 psia); 2) combination physical/chemical solvent
processes (Amisol and Sulf inol); and 3) the Stretford process. All of these
processes operate at temperatures below 420°K (300°F).
2. Process Information
Physical solvent processes remove sulfur compounds from gas streams by physical
absorption in an organic solvent. These processes operate at high pressures
because the solubilities of these sulfur compounds are not sufficiently high at
low pressures. The operating conditions such as temperature and liquid flow rate
depend upon the type of organic solvent used.
Combination chemical/physical solvent processes use a physical solvent together
with an alkanolamine chemical solvent additive. The physical solvent absorbs
sulfur compounds such as €82, COS, and mercaptans which are not easily removed by
chemical solvents while the chemical solvent removes the bulk of compounds such as
H2S. As before, the operating conditions are dependent upon the combination of
solvents used.
D-27
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Both the physical solvent and combination chemical/physical solvent processes
function as concentration steps which require treating of the regenerator off-gas
streams to recover the sulfur as elemental sulfur. The Stretford process recovers
sulfur directly from gas streams containing ^S. The major disadvantages of the
Stretford process are that 1) it removes only I^S and is not effective for removing
other sulfur compounds such as COS, C^, or mercaptans, and 2) HCN will form non-
regenerable complexes with the Stretford solution.
3. Waste Streams
The principle waste streams from the pressurized sulfur removal processes are:
1) Gaseous emissions from the processes which are used to recover sulfur
from the regenerator off-gases. These off-gases will contain COS,
CSg, C02, NH3, HCN, hydrocarbons (including solvent vapor) along with
H2§ in concentrations high enough for economical recovery of sulfur.
While most of the I^S will be removed, some unreacted H2S and S02 will
exit along with other impurities in the regenerator off-gases.
2) Gaseous emissions from the Stretford process oxidizer vent which will
contain water vapor, oxygen, nitrogen, ammonia, and other trace impuri
3) Liquid effluents that are withdrawn from the process to prevent buildup
of solvent impurities. This waste stream will contain the solvent,
solvent degradation products, hydrocarbons, trace elements, etc. which
are removed from the product gas stream.
The tail gases from the sulfur recovery units may require scrubbing to remove
S02 and other impurities. If the organic content is high in these gaseous waste
streams, afterburners may be required. Afterburners can also be used to control
tail gas emissions of compounds such as CD and NH3 by thermal decomposition.
D-28
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Liquid effluents containing oils, tars, and organic compounds may require
several treatment steps. These include oil-water separation and/or flocculation-
flotation for removing suspended tars and oils and extraction, adsorotion, biological
treatment and/or cooling tower oxidation for removing dissolved organic compounds.
Final or ultimate disposal of liquid effluents containing residual organic and
inorganic contaminants is usually an evaporation pond. The liquid effluent from
the Stretford process may contain thiosulfates, thiocyanates, sulfates, and
vanadium salts. Techniques are under development to recover the vanadium present
in this stream.
D-29
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GAS PURIFICATION
Sulfur Removal (Atmospheric) Process No. 21
1. General Information
There are many commercially available processes which have been used to remove
sulfur compounds from natural gas, refinery gases, and coke oven gas. The
sulfur removal processes that have the greatest potential for cleaning of low-
and medium-Btu gas at atmospheric pressure are the chemical solvent processes.
These include amine absorption processes (monoethanolamine, methyl diethanolamine,
diethanolamine, etc.) the Benfield molten carbonate absorption process, and the
Stretford process. All processes in this class operate at temperatures below
420°K (300°F)
2. Process Information
Chemical solvent processes remove acid gases by forming chemical complexes. In
most of these processes, the solvent is regenerated by thermal decomposition of the
chemical complex. These processes are generally identified by the type of solvent
used. Amine and alkaline salt solutions are solvents in common use. The operating
conditions such as temperature and liquid flow rate depend upon the type of solvent
used.
The amine and molten carbonate processes collect H2S from relatively dilute
streams and discharges them in concentrations high enough for economical conversion
to sulfur. The Stretford process is a direct conversion process which removes and
recovers elemental sulfur from l^S by liquid phase oxidation. This process is not
very pressure sensitive and can be used for both pressurized and atmospheric
applications.
3. Waste Streams
The principal waste streams associated with gas cleaning for atmospheric operations
are essentially the same as those associated with pressurized operation. These
are discussed under Process No. 20.
D-30
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Liquid effluents from absorber blow-down can be treated bv the same
techniques discussed for the pressurized process. However, some chemical
solvents produce nonregenerable complexes which may require special treatment
before they are disposed of.
D-31
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-78-061
2.
3. RECIPIENT'S ACCESSION NO.
_ and Medium-Btu Gasification
Systems: Technology Overview
5. REPORT DATE
March 1978
6. PERFORMING ORGANIZATION CODE
AUTHOR1S)
8. PERFORMING ORGANIZATION REPORT NO.
Paul W. Spaite and Gordon C. Page*
PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
Paul W. Spaite Company
6315 Grand Vista Avenue
Cincinnati, Ohio 45213
(*) Radian Corporation
8500 Shoal Creek Blvd.
Austin, Texas 78766
EHE624A
11. CONTRACT/GRANT NO.
68-02-2149 and 68-02-2147*
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 9/77-1/78
14. SPONSORING AGENCY CODE
EPA/600/13
5. SUPPLEMENTARY NOTES j£RL-RTP task officer is William J. Rhodes, Mail Drop 61, 919/
541-2851.
6. ABSTRACT
The report gives an overview of low- and medium-Btu gasification sys-
tems. It describes systems or combinations of processes which are likely to be used
for production of low- and medium-Btu gas from coal. This involves making judg-
ments as to types of coals that will be processed, types of gasifiers (and auxiliary
processes) which will be employed, and markets which will develop for gas from
coal. The report is divided into three main sections: Status of Technology gives a
relatively broad definition of future prospects for coal gasification; Description of
Technology gives more specific information on processes that are likely to be used
commercially; and Environmental Impacts discusses the kinds of pollutant dischar-
ges that must be anticipated. Low- and medium-Btu gasification systems can be
supplied to meet some industrial fuel requirements. Work is needed to develop a
better understanding of both the potential of discharge streams for adverse effects
and control technology and development needs.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Coal Gasification
Coal Gas
Marketing
Pollution Control
Stationary Sources
Industrial Fuels
13B
13H
21D
05C
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
92
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
D-32
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