United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-86/015a June 1986
v°/ERA Project Summary
Coal Gasification
Environmental Data
Summary: Low- and
Medium-Btu Wastewaters
Frank J. Castaldi and F. Douglas Skinner
This report is a compilation of envi-
ronmental characterization data for
wastewaters from low- and medium-
Btu coal gasification facilities. Fixed-
bed, entrained-bed, and ash-agglomer-
ating fluidized-bed coal gasification
processes were examined. The fixed-
bed gasifiers are the Chapman,
Wellman-Galusha, Riley, Foster
Wheeler/STOIC, and Lurgi-type pro-
cesses. The entrained-bed gasifiers are
the Koppers-Totzek and Texaco pro-
cesses. The KRW-PDU was used as an
example of an ash-agglomerating
fluidized-bed process. The types of
wastewaters examined from the vari-
ous coal gasification processes are
product gas quench condensates, cy-
clone dust quench waters, ash pan
waters, gas compression and cooling
condensates, acid gas removal waters,
and leachates from slag and ash dis-
posal facilities. The available waste-
water quality and quantity data for
these aqueous waste streams are as-
sembled, and the associated environ-
mental significance is addressed. The
report describes gasification process
characteristics and how they relate to
wastewater quality and discusses the
biodegradability of quench conden-
sates from the different gasifier types.
This Project Summary was devel-
oped by EPA's Air and Energy Engineer-
ing Research Laboratory, Research Tri-
angle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
As a result of the Energy and Security
Act, EPA is one of the Consulting Agen-
cies that review Environmental Moni-
toring Outlines and Plans as required by
the Synthetic Fuels Corporation (SFC)
for coal gasification projects receiving
financial assistance. As part of this con-
sultation, EPA advises on the adequacy
of proposed Environmental Monitoring
Plans and participates in Monitoring Re-
view Committee activities for the
projects.
In the past decade, EPA has con-
ducted many environmental data acqui-
sition studies at coal gasification facili-
ties in the United States, Europe, and
Africa. Both fixed- and entrained-bed
coal gasification facilities were exam-
ined. Comprehensive data on the char-
acteristics of process and waste
streams have been obtained from these
sampling programs. These data were
used to estimate the wastewater pollu-
tant characteristics from commercial
coal gasification facilities and provide a
basis for the evaluation of applicable
control technologies.
The EPA's Environmental Assess-
ment data, when properly compiled and
summarized, can provide information
to:
• Identify environmental and health
issues requiring further definition
through data acquisition at SFC-
supported facilities.
• Recognize process-specific charac-
teristics for both synfuels produc-
tion and pollution control technolo-
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gies which would influence the
scope and areas of emphasis in the
planned monitoring.
• Define data interpretation and pre-
sentation approaches which will fa-
cilitate the evaluation of the data
addressing particular areas of con-
cern in mitigating environmental
and health problems with future fa-
cilities.
To support this effort, several docu-
ments which address specific environ-
mental pollutant or discharge cate-
gories characteristic of coal gasification
technologies have been prepared.
Areas are: sulfur and nitrogen species,
organics, trace elements, solid wastes,
and wastewater. The documents sum-
marize environmental data for the
Chapman, Wellman-Galusha, Riley,
Foster-Wheeler/STOIC, Lurgi, Lurgi-
type, Koppers-Totzek, KRW Energy Sys-
tems, and Texaco gasification pro-
cesses. These data are compared and
contrasted to develop trends and/or cor-
relations that can be used to assess the
environmental impacts associated with
the different coal gasification pro-
cesses.
This report is a compilation of data on
wastewater quality from the subject
coal gasification processes. It presents
background on the gasification tech-
nologies, defines major aqueous waste
streams, summarizes all available
wastewater quality and quantity data,
assesses environmental impacts, de-
scribes gasification process characteris-
tics and how they relate to wastewater
quality, and discusses the biodegrad-
ability of quench condensate streams
from the different gasifier types.
Objectives
The objective of this report is to
present an environmental analysis of
pollutant species in coal gasification
wastewaters. The data available from
environmental assessment efforts, sup-
plemented by literature data, are com-
piled, summarized, evaluated, and doc-
umented to provide:
• A consolidated summary of the
available wastewater quality data
for commercial-scale coal gasifica-
tion processes.
• An interpretive evaluation of the
data including:
(1) Trends in pollutant behavior
between processes.
(2) Identification of unique or
specific characteristics of indi-
vidual processes.
(3) Identification of particular envi-
ronmental issues, both those
common to all processes and
those unique to individual pro-
cesses.
(4) Recommendations for monitor-
ing of commercial scale sys-
tems to further define environ-
mental issues or apparent
trends in pollutant behavior.
• A basis for the evaluation of syn-
fuels facility Environmental Moni-
toring Plans relative to wastewater
characteristics.
• A resource for EPA Regional Offices
and state agencies involved in per-
mitting of gasification facilities.
Results and Conclusions
Wastewater characterization data on
the aqueous wastes from both fixed-
and entrained-bed commercial coal
gasification processes were gathered
from many source test and evaluation
studies at synthetic fuels facilities to
identify environmental and health is-
sues requiring further definition. These
gasification facilities are the Wellman-
Galusha (Glen - Gery), Wellman-
Galusha (Fort Spelling), Chapman-
Wilputte, Lurgi (Westfield, Scotland),
Lurgi-type (Kosovo), Lurgi (Sasolburg),
Foster Wheeler/STOIC, Riley Gas Pro-
ducer, Koppers-Totzek, and Texaco
processes. Information on the test peri-
ods and coals gasified is presented in
Table 1. Results of wastewater charac-
terization studies performed on the
KRW-PDU are also included for com-
parison with the Koppers-Totzek and
Texaco entrained-bed gasifiers because
the quench condensates from this ash-
agglomerating gasifier have similar
chemistries.
The environmentally significant spe-
cies evolved from coal during gasifica-
tion in low- and medium-Btu processes
can be broadly grouped into five cate-
gories: heavy hydrocarbons (C6+, oils,
and tars), volatile nonmethane hydro-
carbons (C2 - 65), inorganic sulfur com-
pounds, inorganic nitrogen com-
pounds, and trace elements. The
process areas that generate waste-
waters with these contaminants are
coal preparation, coal pretreatment
(thermal drying, mild oxidation, slurry
preparation), coal gasification, particu-
late removal and gas cooling, shift con-
version, and acid-gas removal. Waste-
waters from these process areas
contain some or all of the categories of
pollutants identified above.
Results
Much of the data developed from the
environmental characterization sam-
pling programs did not yield waste-
water quality data for the different gasi-
fication processes that were directly
comparable because they were de-
signed to focus on streams of potential
environmental significance. However,
these environmental characterization
test programs did provide a listing of
pollutants common to the different coal
gasification processes, and these data
were used to select wastewater dis-
charge pollutants for environmental
monitoring.
The heterogeneous nature of coal
gives rise to a wide variety of organic
and inorganic compounds in aqueous
streams resulting from coal conversion
processes. These pollutants are sum-
marized in Tables 2 and 3 for the fixed-
and entrained-bed gasification pro-
cesses, respectively. These aqueous
phase pollutants are characteristic of
wastewaters from the Wellman-
Galusha, Chapman, Lurgi-type, Texaco,
and Koppers-Totzek gasifiers. Many of
the substances listed in Tables 2 and 3
were detected and are typically present
in coal gasification wastewaters, albeit
at relatively low concentrations.
Process condensates from coal gasifi-
cation have long had a reputation for
being highly polluting and difficult to
treat because they contain substantial
concentrations of ammonia, phenols,
and sulfur compounds. All of these
chemicals can be directly toxic to
aquatic life. They also exert an indirect
toxic effect, as they undergo biochemi-
cal oxidation in the aquatic environ-
ment which consequently becomes de-
ficient in dissolved oxygen.
Pollutants in aqueous wastes from
coal gasification processes represent-
ing the highest potential for environ-
mental (ecological) hazard are ammo-
nia, cyanide, and phenolics. Ammonia
represents the most severe potential
environmental hazard because of the
toxicity of undissociated ammonia to
aquatic organisms. This toxicity is pH
dependent and is directly related to the
concentration of undissociated ammo-
nia. Since most coal gasification pro-
cesses have the potential to discharge
large volumes of ammonia contami-
nated alkaline wastewaters, the undis-
sociated ammonia fraction could reach
toxic levels in the receiving water. Treat-
ment for ammonia removal is, there-
fore, a primary concern before aqueous
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Table 1. Coal anrfCOa/ Gasification Facility Type
Type of Gasifier
Chapman- Wilputte
Foster Wheeler/STOIC
Koppers-Totzek
Site
Kingsport, TN
U. of Minnesota
Duluth, MN
Modderfontein,
So. Africa
Type of Coal
Virginia bituminous
Bituminous coal from Pinnade Seam
Bituminous, high volatile coal from
So. Africa
Year of Study
1978
1981
1979
Product Gas
Heat Content3
low
low
medium
Lurgi, Dry Ash
Lurgi-type, Dry Ash
Lurgi, Tri-State Syn-
fuels Test
Riley (modification of
Morgan Gas Pro-
ducer)
KRW-PDU
Texaco
Wellman-Galusha
Westfield, Scotland
Kosovo, Yugoslavia
Sasolburg, So. Africa
Worcester, MA
Madison, PA
Ruhrkohle/Ruhrchemie
Federal Republic of
Germany
Glen-Gery Brick Co.
York, PA
Fort Snelling, MN
Rosebud, subbituminous coal from 1973-1974
Montana; bituminous coals from
Percy, Illinois; and Pittsburgh non-
caking and non-swelling coal from
Federal No. 1 mine
Lignite from Kosovo mine 1981
Western Kentucky coal 1981
North Dakota lignite 1979
Wyoming subbituminous, Pittsburgh 1983
No. 8 bituminous, and North Dakota
lignite
Illinois bituminous 1980
Pennsylvania anthracite 1978
North Dakota lignite (Indian Head) 1978
medium
medium
medium
low
medium
medium
low
low
"Low means less than 5500 kJ/m3; medium means about 11,000 kJ/m3.
wastes from coal conversion processes
are discharged.
In the case of cyanide, available data
on the acute toxicity of simple cyanides
to fish reveal that the minimum lethal
(threshold) concentrations of free
cyanide are usually less than 250 ppb. It
is generally acknowledged that free
cyanide concentrations in the range
from 50 to 100 ppb as cyanide have
proven eventually fatal to many sensi-
tive fishes and levels much above
200 ppb probably are rapidly fatal to
most fish species. Cyanide, a monoden-
tate ligand, will complex with many
metals and, as such, has the potential of
bioaccumulating in aquatic plants and
animals. The long-term effects of com-
plexed cyanide in the aquatic environ-
ment have not been investigated ade-
quately to determine separate water
quality criteria regarding chronic toxic-
ity impacts.
Phenolics represent an environmen-
tal hazard that is somewhat lower in
magnitude than that of cyanide. Pheno-
lic compounds can affect freshwater
fish adversely by direct toxicity to fish
and fish-food organisms, by lowering
the amount of available oxygen be-
cause of the high oxygen demand of the
compounds, and by tainting of fish
flesh. Phenolic toxicity in the aquatic
environment is enhanced by lower dis-
solved oxygen concentrations, in-
creased salinity, and increased temper-
ature. A major aesthetic problem
associated with phenolic compounds is
their organoleptic properties (i.e., ability
to affect one or more organs of the
body) in water and fish flesh.
The degree of hazard exhibited by sul-
fide to aquatic animal life is dependent
on the temperature, pH, and dissolved
oxygen level of the receiving water. At
lower pH, a greater proportion of the
sulfide is in the form of toxic undissoci-
ated H2S. In winter, when the pH is neu-
tral or mildly acidic, the hazard from sul-
fides is increased. This hazard is
exacerbated when dissolved oxygen
levels are low (but not lethal to fish).
The major metals in coal gasification
wastewaters are boron, cadmium, cop-
per, lead, selenium, and zinc. These
metals were found in each of the differ-
ent coal gasification wastewaters at
varying concentration levels. All are
toxic to animals and man, except boron
which (like cadmium) has phytotoxic
properties. Some of these metals
present a particular environmental con-
cern because they have the potential to
bioaccumulate, thereby producing a
chronic poisoning effect. Boron is a pol-
lutant that represents environmental
hazard only with regard to agricultural
water use.
Metals which have a measurable en-
vironmental impact and are also acutely
toxic to man are cadmium, selenium,
and lead. Allowable levels in domestic
water supplies are 10 (j.g/L for cadmium
and selenium and 50 jj,g/L for lead. How-
ever, the allowable concentrations in
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Table 2. Substances Identified in Fixed-Bed Gasification Wastewaters
Lurgi"
Gas Liquor
Aluminum
Ammonia
Antimony
Arsenic
Barium
Beryllium
Boron
Calcium
Catechols
Cerium
Chromium
Cobalt
Copper
Cresols
Cyanide
Fluorine
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phenol
Phosphorus
Resourcinols
Rubidium
Scandium
Selenium
Silicon
Silver
Sodium
Strontium
Thiocyanate
I Itanium
Uranium
Vanadium
Xylenols
Yttrium
Zinc
Zirconium
Chapman6
Separator Liquor
Ammonia
Antimony
Arsenic
Barium
Boron
Cadmium
Calcium
Carboxylic Acids
Cerium
Cesium
Chloride
Chlorine
Copper
Cyanide
Fluorine
Fused Aromatic Hydrocarbons
Heterocyclic Nitrogens
Heterocyclic Sulfurs
Iron
Lanthanum
Lithium
Magnesium
Mercury
Phenols
Phosphorus
Rubidium
Scandium
Selenium
Silicon
Silver
Thiols
Titanium
Tungsten
Yttrium
Zirconium
Wellman-Galusha0
Ash Sluice Water
Ammonia
Barium
Benzenethiol
Benzo(e)pyrene
Chromium
Cresols
Cyanide
Dibenz(a,h)pyrene
Iron
Lanthanum
Lithium
Phenols
Selenium
Thiocyanate
aFor various coals (e.g., bituminous and lignite).
^Virginia bituminous coal.
°Pennsylvania anthracite.
the aquatic environment for protection tion, nature
of product gas cleanup and
and tars, and processes that produce
little or none of these pollutants.
The types of wastewaters that are
generated by coal gasification pro-
cesses are product gas quench conden-
sates, cyclone dust quench waters, ash
pan waters, gas compression and cool-
ing condensates, acid gas removal
waters, and leachates from slag and ash
disposal facilities. The severity of the
contamination associated with the indi-
vidual effluents varies with the coal
gasification process. However, a gen-
eral assessment of pollutant strength
and stream volume places the quench
condensates above other aqueous
waste streams as the principal waste-
water source.
Quench condensates can be classified
by gasifier type (in this case, fixed- or
entrained-bed) and have relatively con-
sistent chemistries for a given gasifier
category. These waters are usually the
largest volume aqueous waste stream
from a gasification process, and (in the
case of fixed-bed gasifiers) they con-
tribute substantial organic pollutant
loads to wastewater treating facilities.
However, these aqueous wastes can be
treated for removal of most conven-
tional pollutants by biooxidation after
the appropriate pretreatment.
Most coal gasification wastewaters
from both fixed- and entrained-bed
processes can be controlled with re-
spect to the discharge of conventional
pollutants (e.g., BOD, COD, and pH). The
control of selected organics and trace
elements varies with the gasification
process. Fixed-bed gasifiers need to
have specific attention paid to the dis-
charge of phenolics, polynuclear aro-
matic hydrocarbons, ammonia,
cyanide, and many heavy metals.
Entrained-bed gasifiers need to have at-
tention paid to such nonconventional
pollutants as ammonia, thiocyanates.
free and complexed cyanides, and
boron.
of certain fresh water animals/fish are
considerably lower. Although these
metals are present in coal gasification
wastewaters at relatively low concen-
trations, they still present the potential
for severe environmental hazard due to
progressive, chronic poisoning.
Conclusions
There are considerable differences in
the quality of wastewaters produced
from the various coal gasification proc-
esses, both between and within gasifier
types. These differences are due to
process configuration, gasifier opera-
ash removal/handling, and the feed coal
used. However, representative waste-
water chemistries can be established
for similar gasifiers with similar product
gas cleanup and ash removal/handling
operations fed with similar coals. This
permits a categorization of wastewaters
into two functional groups: aqueous
wastes from tar producing (e.g., fixed-
bed) gasification and aqueous wastes
from non-tar producing (e.g., ash-
agglomerating/fluidized-bed and
entrained-bed) gasification. That is, coal
gasification processes that produce
substantial quantities of phenolics, oils.
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Table 3. Substances Identified in Entrained-Bed Gasification Wastewaters
Koppers-Totzek
Modderfontein
Texaco
Ruhrkohle/Ruhrchemie
Ammonia3
Anthraceneb
Barium b
Benz(a)anthraceneb
Benzo(b)fluorantheneb
Boron3
Bromineb
Chlorine8
Copper6
Cryseneb
Cyanide3
Fluorantheneb
Fluorineb-c
lronb-c
Magnesiumb'c
Nickel"
Phenanthreneb
Potassiumb-c
Pyreneb
Silicon3
Sodiumc
Thiocyanate3
Zincc
Ammonia
Barium
Boron
Bromine
Cerium
Chlorine
Cyanide
Fluorine
Iron
Lead
Magnesium
Molybdenum
Nickel
Potassium
Silicon
Sodium
Thiocyanate
Zinc
Zirconium
"Quench condensates.
bRectisol wastewater.
Compressor condensates.
Frank Castaldi and Douglas Skinner are with Radian Corporation, Austin, TX
78766.
William J. Rhodes is the EPA Project Officer (see below).
The complete report, entitled "Coal Gasification Environmental Data Summary:
Low- and Medium-Btu Wastewaters," (Order No. PB 86-192 267/AS; Cost:
$16.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U. S. GOVERNMENT PRINTING OfFICE:1986/646-l 16/20854
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