United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81-070 Aug. 1981
Project Summary
EPA Coal Cleaning Program
FY 1979 Progress Report
J. Moore, D. Sargent, and B. Hylton
The report describes work performed
by a dozen organizations to explore
opportunities for wider use of coal as
an environmentally acceptable energy
source. Many aspects of coal were
studied during 1979, including the
use of low sulfur coal, removal of coal
sulfur by coal cleaning, and measure-
ment of emissions from the cleaning
processes themselves. Seventeen
projects were active in three major
research categories: environmental
assessment, technology assessment
and development, and pollution con-
trol technology.
Several projects were directed to-
ward achieving a better knowledge of
the characteristics of estimated coal
resources. One approach was to de-
velop an understanding of the effects
of geologic formation processes on
the properties of the resulting coal-
especially sulfur and ash content.
Another approach was to develop
empirical data bases from multiple
source sampling programs, past and
present, to help identify constituents
of coal deposits and relate them to
environmental and economic concerns.
Other studies evaluated certain coal
cleaning techniques, equipment, and
systems to assess possibilities for
their improvement. Alternative strate-
gies for compliance with sulfur dioxide
(SO2) emission rules for coal combus-
tion were explored, as were assess-
ment and control of pollution from
coal cleaning processes.
This report was submitted in fulfill-
ment of Contract 68-02-3136 by
Versar Inc. under the sponsorship of
the U.S. Environmental Protection
Agency. The report covers the period
from October 1, 1978 through Sep-
tember 30,1979, and work was com-
pleted as of June 30, 1980.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, Research
Triangle 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
United States mineable coal resources
are estimated at 1.5 x 10'2 Mg, enough
to supply the U.S. with electric power for
800 years at 1976 comsumption rates.
In addition, coal is a versatile fuel which
can be tailored to many specific uses by
appropriate preparation and treatment.
The benefits of coal preparation have
not been fully explored, and to that end
the U.S. Environmental Protection
Agency (EPA) is coordinating a coal
cleaning program in conjunction with
the U.S. Departments of Energy and
Interior. This program aims to evaluate
the multiple possibilities of coal prepa-
ration and to assist in the development
of technologies for coal beneficiation
and concurrent pollution control. During
1979, EPA sponsored work on 17 projects
related to coal preparation, which were
carried out by a dozen organizations.
1979 Coal Cleaning Program
Highlights
Specific projects in the EPA ceal
cleaning program exhibit a variety of
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approaches to the achievement of envi-
ronmentally acceptable and economi-
cally feasible coal use.
Coal Quality
A program being performed by the U.S.
Geological Survey (USGS) under Inter-
agency Agreement EPA-IAG-DX-E685
addresses characterization of coal qual-
ity. The overall objective of this program
is to typify the chemical, mineralogical,
and physical properties of U.S. coal
resources. This knowledge is essential
to an assessment of the extent of i
particular deposit and its potential for
use under stringent environmental
regulations or sophisticated industrial
process requirements. Data and statisti-
cal summaries of 617 eastern coal
samples collected in FY 78 were re-
ported by Zubovic and others in USGS
Open-File Report 79-665. During FY 79,
660 samples of eastern U.S. coals and
approximately 500 samples of western
coals were analyzed. Statistical data
summaries on 19 chemical elements
considered to be deleterious to the
environment are presented. Comparison
of the FY 79 eastern coal averages with
averages for 4,810 samples of U.S.
coals shows that eastern coals have
higher average contents of most of
these elements. Only Cd and Mn are
significantly higher in the average U.S.
coal than in eastern coals. Detailed
analytical data on individual samples
will be available from Zubovic and
others in 1980.
Geology of Contaminants
in Coal
A second USGS effort in 1979, per-
formed under the same agreement,
correlated coal geology with coal con-
taminants. During FY 79, USGS focused
on the geologic controls on mineral
matter variation of the Homer City, PA,
dedicated reserves of the Upper Free-
port coal bed. Parametric statistics were
applied to the analytical data and re-
sulted in the following conclusions:
• Variation in mineral matter content
of the Upper Freeport reserves was
primarily controlled by inherent
plant ash and the surrounding
hydrologic environment.
• Low ash and low sulfur coal is the
product of peat that formed under
highly acid conditions (pH <4.5),
whereas coal with higher ash and
sulfur was formed under pH condi-
tions of 4.5 to 7.5.
Mineral Matter and Trace
Elements in Coal
The Illinois State Geological Survey is
also participating in EPA's coal cleaning
program under Grant No. R806654.
This project will establish an elemental
and mineralogical interpretation of the
Illinois No. 5 and No. 6 coals, which can
be used to locate coal with environ-
mentally hazardous or economically
recoverable elements. The interpreta-
tions can be used for selecting and
developing coal cleaning techniques.
Non-clay mineral analyses were com-
pleted in 1979 for 15 face channel and
drill core samples and for 27 float/sink
separations. Major minerals present
included pyrite, calcite, quartz, kaolinite,
illite, and expandable clay minerals.
Clay mineral analyses were completed
for 10 of the composite face channel
and drill core samples with the following
results:
Coal % Kaolinite % Illite % Expendables
No. 5
No. 6
29
31
37
40
34
29
As more data become available, indi-
vidual clay mineral percentages for both
coals will be mapped and interpreted for
trends.
Coal Environmental Profile
System
Research Triangle Institute (RTI) is
performing an environmental assess-
ment study within the EPA coal cleaning
program under Contract 68-02-3170.
The Coal Environmental Profile System
(CEPS) is a project activity under devel-
opment to provide a characterization of
the environmental effects of coal trans-
port/handling/storage systems, coal
cleaning processes, and coal combus-
tion processes. To implement this study,
RTI designed a generator to produce a
coal dust aerosol from raw coal, and
repeated runs in the dust generator with
western Kentucky No. 9 and North
Dakota Zap lignite that showed that coal
dust presents a significant inhalation
hazard.
When exposed to air, coal combines
with oxygen and releases heat. This low
temperature burning is incomplete and
generates a spectrum of organic com-
pounds of the same general type as
those arising from pyrolysis or devola-
tilization of coal. The lower rank western
coals, which represent the largest U.S.
reserves, are particularly prone to this
type of self-heating. Differential scanning
calorimetry (DSC) was used to identify
coals that require special attention. The
rate of heat absorption or generation
was measured as the temperature of a
coal sample increased linearly. A plot of
heat release vs. temperature for three
different fuels is shown in Figure 1.
Further refinements of these tests are
planned.
Environmental Assessment
Study
A major project begun by Battelle
Columbus Laboratories, under EPA
Contract 68-02-2163, was continued by
Versar, Inc. and Teknekron Research,
Inc. under EPA Contract 68-02-3136.
As documented in EPA Report EPA-
600/7-79-073b (NTIS PB 300671),
Battelle Columbus Laboratories provided
several automated data bases and two
computer models that are being used in
the ongoing effort by Versar and
Teknekron.
A major goal of the project is estab-
lishment of a strong emissions data
base for physical coal cleaning (PCC)
processes by a sampling and analysis,
program that includes physical, chemM
cal, and biological testing of pollutant
emission streams. Discharges already
identified as having potentially adverse
environmental effects are leachate and
runoff from waste ponds and piles;
fugitive dust from coal crushing and
sizing areas, storage piles, and refuse
piles; and thermal dryer emissions.
The Resource Process Assessment
Model (RPAM) developed by Battelle
Columbus Laboratories is being used by
Teknekron to project coal usage and
availability by SO2 emission parameter.
During FY 79, model capabilities were
extended, coal reserve data bases were
correlated to determine geographical
compatibility, and a production data
base for the year 1976 was formed
using annual reports submitted by coal
companies to state agencies. The revised
model is identified as the Coal Assess-
ment Processor (CAP) model.
Sulfur content and heating value data
for 53 different coal-source/cleaning-
plant combinations were statistically
analyzed to document the effectiveness
of commercially operating coal cleaning
plants in reducing sulfur and enhancing
heating value and to define the effect of
physical coal cleaning on sulfur variabil-
ity. Analysis showed that both the
absolute standard deviation and the
relative standard deviation for all three
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Rate of
Heat Release
(Exothermic)
Wyoming Smith-Roland
\
\
Pre-dried
N. Carolina'**
Peat
N. Dakota
Beulah-Zap Lignite
T
500
Degrees Centigrade
5OO
Figure 1. DSC results for carbonaceous fuels in air, 5°C/min.
coal characteristics were reduced by the
coal preparation process.
Battelle Hydrothermal Process
Battelle Columbus Laboratories, under
EPA Contract 68-02-2187, continued to
work for improvement of their chemical
coal cleaning (CCC) process. The Battelle
Hydrothermal Process treats a 70 per-
cent minus 200 mesh coal with aqueous
'sodium and calcium hydroxides at ele-
vated temperatures and pressures. This
treatment has been found to remove
nearly all pyritic sulfur and 25-50
percent of organic sulfur from Appala-
chian and eastern interior coals. Zinc
oxide, ferrous and ferric hydroxides,
reduced activated ferric oxide, and
ferrous carbonate were found to be
effective in removing the major portion
of the sulfide sulfur from the spent
leachant. Operating costs for a self-
contained hydrothermal treatment plant
were estimated at $30.34/Mg($27.52/
ton) for a typical eastern coal, and
$6.89/Mg ($6.25/ton) for a western
subbituminous coal. Certain coals with
low organic sulfur and high pyritic
sulfur can be cleaned more efficiently by
a combination of hydrothermal and
physical coal claining. Costs for this
scenario were estimated at $18.85/Mg
($17.10/ton).
Homer City Coal Cleaning
Plant
A project is being performed by the
Pennsylvania Electric Co. (Penelec)
(EPA Contract 68-02-3124) at the ad-
vanced coal cleaning pilot plant under
construction near the Homer City Gen-
erating Station Power Complex in Homer
City, PA.
During 1979, the effectiveness of the
electrostatic precipitator (ESP) equip-
ment was measured while firing run-of-
mine coal in the two types of precipitators
that are used at the Homer City Power
Station. The oldest precipitator per-
formed marginally well, while the new-
est and conservatively designed unit No.
3 performed outstandingly when run-
of-mine coal was burned. An additional
series of tests with ESP plate rapping
suspended for various periods of time
revealed that performance can be im-
proved markedly by controlled plate
rapping in sequence.
Another accomplishment was the
development of a system to compile
operating cost data from the plant. Also,
a coal laboratory was set up with spe-
cialized equipment for performing coal
washability, ash, and particle size
distribution analyses of large quantity
samples.
Dense-Medium Cyclone
Project
Under Interagency Agreement EPA-
IAG-D6-685, the Department of Energy,
in cooperation with EPA, EPRI, and the
Homer City preparation plant owners, is
conducting a comprehensive pilot plant
study on dense-medium cycloning of
fine coal at lower-than-normal specific
gravities of separation (~1.30).
During 1979, approximately half of a
series of 60 tests was done with
magnetite and water to define the
effects of various combinations of
pressure and flow rate. A comparison
was begun of techniques for analysis of
size distribution of magnetite below 325
mesh, and a newly designed device to
test slurry viscosity was being calibrated
and modified.
Coal Cleaning Technology
Assessment
During 1979, Versar Inc. performed a
study under EPA Contract 68-02-2199
to assess the applicability of using three
pollution control technologies—low
sulfur coals, PCC, and CCC—for com-
pliance with SO2 emission regulations
for industrial boilers (report EPA-600/7-
79-178c; NTIS PB 80-174055). Results
showed that representative low sulfur
western coals could meet all emission
levels down to 520 ng S02/J (1-2 Ib
SOz/106 Btu). The representative low-
sulfur raw eastern coal could achieve
emission levels above 860 ng SO2/J
(2.0 Ib S02/106 Btu), and, when physi-
cally cleaned, the coal could be used to
meet an emission level of 520 ng S02/J
(1.2 Ib SO2/106 Btu). The representative
high sulfur eastern coal could be cleaned
to meet the emission level of 645 ng
SO2/J (1.5 Ib S02/106 Btu), but chemi-
cal coal cleaning was required to comply
with more stringent limits.
Another part of the study was sampling
and analysis to evaluate the performance
of three types of coal cleaning equip-
ment—heavy-media cyclones, hydrocy-
clones, and froth flotation units—in
reducing pyritic sulfur content of fine
coal. Versar's subcontractor, Denver
Equipment Division of Joy Manufactur-
ing Co., submitted field reports contain-
ing the results from these tests in 1979,
and Versar began preliminary data
analyses.
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Evaluation of Physical and
Chemical Coal Cleaning
Under EPA Interagency Agreement
IAG-D9-E721 -Bl, the Tennessee Valley
Authority in Muscle Shoals, AL, com-
pleted a study (report EPA-600/7-79-
250; NTIS PB 80-147622} of seven coal
cleaning processes (three physical,
three chemical, and one combination) to
evaluate sulfur removal and economic
viability of the processes when used
alone and in combination with flue gas
desulfurization (FGD). From the anal-
yses, the following conclusions were
reached:
• Physical coal cleaning is a com-
mercial cost-effective method of
meeting an emission limit of 520
ng S02/J (1.2 Ib S02/106 Btu) for
coals with sulfur levels below
about 1.2 percent.
• Physical coal cleaning plus partial
scrubbing with limestone FGD is
generally cost effective in meeting
the above limit for feed coals with
sulfur contents below about 3
percent.
• Coal cleaning plus partial scrubbing
with limestone FGD is generally
less cost effective than limestone
FGD alone in providing 85 percent
S02 reduction.
• A potentially advantageous S02
emission control approach is pel-
letization of finely ground cleaned
coal with limestone.
Physical Coal Cleaning
Computer Economics
A second project being performed by
TVA (EPA-IAG-D9-E721-GP) is the
development of a computer program
that determines the most economical
approach for sulfur removal using
physical coal cleaning plus partial lime-
stone scrubbing. The program will
accept site-specific input variables such'
as coal composition, boiler size, trans-
portation costs, cleaning process details,
sulfur removal efficiencies, emission
standard goals, and economic premises.
No results are yet available, since the
project was approved during the last
week of FY 79 and scheduled for com-
pletion in early 1981.
Coal Cleaning Costs and
Benefits
In FY 79, under EPA Contract 68-02-
2603, PEDCo identified and quantified
the benefits of using physically cleaned
coal versus run-of-mine coal for utility
steam electric generation. It was found
that the combined total of all of the
benefits addressed by PEDCo usually
exceeded the cost of cleaning the coal.
PEDCo recommends additional projects
aimed at quantifying coal cleaning
benefits and presents an annotated
bibliography of related studies.
Coal Desulfurization Using
Microwave Energy
General Electric Company, under EPA
Contract 68-02-2172, is continuing
research into a process developed by
that company prior to 1979. The coal
cleaning process uses microwave energy
to remove 50 percent of the pyritic
sulfur. In combination with sodium
hydroxide, it removes more than 95
percent of the pyritic sulfur and about
60 percent of the organic sulfur. During
1979 further experiments have shown
that microwave heating (in the absence
of NaOH) converts pyrite (FeS2) to
strongly magnetic pyrrhotite (Fei-xS)
which can then be magnetically removed.
Another significant result is that the
atmosphere of the microwave treatment
has an important effect on the nature of
the conversion product. When treatment
was performed in the presence of air,
iron oxide was produced; in the presence
of argon, pyrrhotite resulted. The ex-
perimental correlation between the
microwave treatment atmosphere and
the new phases produced ambiguous
results, and more analyses and data
interpretation remain to be done. How-
ever, the potential for coal desulfuriza-
tion by the microwave process appears
to be promising.
Environmental Studies of
Coal Cleaning Processes
The Tennessee Valley Authority is
also conducting a project (EPA-IAG-D8-
E721-GA) which aims to characterize
the waste streams and leachate from
refuse piles generated by coarse coal
beneficiation. An additional goal is to
assess coal cleaning's effect on the ash
composition and wastewater character-
istics in a coal-fired power plant. Data
from a level C coal cleaning plant were
evaluated in 1979. For this plant, the
cleaned coal product contained less
ash, more energy per unit weight, and
approximately the same amount of total
sulfur as the raw coal.
Based on the single plant sampled,
the total quantity of trace metals re-
maining for disposal after the combus-
tion of cleaned coal would be less than
that from combustion of raw coal, but a
higher concentration of some tracef
metals would be found in the ash from
combustion of the cleaned coal. Mercury
appeared to be substantially concen-
trated in the cleaned coal, but this
observation was based on only one
sample of feed coal. The dissolved con-
centrations of Mn, Cu, Zn, Ba, and As in
the fine refuse slurry were below the
water quality criteria for domestic water
supply intakes proposed by EPA.
Preservation of Reactor Test
Unit and Desulfurization of
Gob Pile Samples
The development by TRW of the
Meyers Process for leaching of pyritic
sulfur from coal has been sponsored by
EPA (Contract 68-02-1880) through
construction and operation of a 7 Mg/d
(8 ton/d) test plant termed the Reactor
Test Unit (RTU). An inspection program
in 1979 showed that the reactor vessel,
the reactor internals, and the slurry
recirculation loop equipment were
severely corroded. It was recommended
that the original stainless steel reactor
be replaced with a new reactor made of
titanium.
A modification of the Meyers Process,
the Gravichem Technique, was investi- (
gated at bench scale in FY 79. TRW
concluded that application of the Gravi-
chem Process to eastern and midwestern
steam-coal resources would reduce
SO2 emissions in the United States by
45-58 percent. It was also found that
the Gravifloat portion of the Gravichem
Process can recover depyrited, very low
ash and low sulfur fuel from waste coal
fines found in slurry ponds. In addition,
the Gravifloat coal in oil or water slurry
is a potentially excellent fuel for use in
coal conversion units. Future work with
the RTU will be done under the direction
of the U.S. Department of Energy, to
whom the test unit was transferred in
September 1979.
Trace Element
Characterization and
Removal/Recovery from Raw
Coal and Coal Preparation
Wastes
The overall objectives of a Los Alamos
Scientific Laboratory (LASL) research
program (EPA-IAG-79-D-X-0521 )are to
assess the problem of trace element
contamination in coal waste drainage
and to identify suitable control technol-
ogies. In the past year, studies of the
mineralogy and elemental composition
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of low sulfur coal refuse samples col-
lected from the Appalachian area were
performed and the aqueous leaching
behavior of the materials was investi-
gated.
Leaching tests were conducted on the
refuse material and these data were
analyzed using Multimedia Environ-
mental Goals established by EPA. Based
on this criterion, LASL identified Al, Cu,
Fe, Mn, Ni, and Zn as those elements of
environmental concern in the leachates
from the sample of Appalachian region
refuse that was studied. Calcining (high
temperature treating of the refuse) and
co-disposal with lime or other attenuat-
ing agents or sorbents were found to be
the most promising control strategies
applied directly to the refuse. Preleach-
ing of the refuse and sealing of the pile
were found to be less effective.
LASL also initiated studies on the
effectiveness of using a variety of
sorbents such as clays, soils, and solid
coal combustion byproducts on high-
sulfur coal refuse leachates. Alkaline
neutralization was shown to be the
most effective and least costly of the
refuse drainage treatment options stud-
ied. Ion exchange and reverse osmosis
both proved to be technically feasible
methods for reducing the contaminants
in refuse drainage to acceptable levels;
however, the need to neutralize the
solutions sharply reduces the applica-
bility of these methods.
Relative cost effectiveness, treatment
duration, possible hazardous classifica-
tion, and permanency of the most
promising control method were also
studied and reported in DOE document
LA-8039-MS.
Oil Agglomeration for
Effluent Control
Battelle Columbus Laboratories is
investigating techniques to enhance the
efficiency of oil agglomeration for re-
covery of coal from preparation plant
wastes (EPA Contract 68-02-3108). A
previous laboratory study completed by
Battelle under EPA contract 68-02-
2112 demonstrated that coal recoveries
of 90 percent or greater can be realized
by using oil agglomeration on coal
cleaning wastes (report EPA-600/7-
79-025b; NTIS PB 293210). The present
Battelle effort is directed at evaluating
pretreatment techniques to enhance
separation of pyrite from coal in the oil
agglomeration process. The study also
aims to assess the performance of oil
agglomeration as an alternative or ad-
junct to existing effluent control of coal
cleaning plants.
The 1979 slurry samples from one
Kentucky and one Illinois coal cleaning
plant were characterized for their solids
content, settling characteristics, sieve
size distribution, and concentrations of
ash, sulfur, and coal. Surface pretreat-
ment methods for pyrite were screened
by using pyrites and cleaned coal col-
lected at the same place and time as the
slurry samples. The most effective pre-
treatment method determined by the
screening test was then used to treat
the blackwater sediments. When com-
pleted in 1980, these studies should
suggest agents and conditions which
give optimum pyrite rejection and maxi-
mum coal recovery from coal cleaning
blackwater.
J. Moore, D. Sargent, and B. Hylton are with Versar, Inc., 6621 Electronic Drive.
Springfield, VA 22151.
David A. Kirchgessner is the EPA Project Officer (see below).
The complete report, entitled "EPA Coal Cleaning Program: FY 1979 Progress
Report." (Order No. PB 81'-219 560; Cost: $9.50, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
US. OOTBWMENT PRINTING OFFICE t»«1 - 757-012/7278
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