United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 2771 1
EPA-600/7-79-072
February 1979
EPA-lnteragency Coal
Cleaning Program:
FY 1978
Progress Report
Interagency
Energy/Environment
R&D 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-600/7-79-072
February 1979
EPA-lnteragency Coal Cleaning
Program:
FY 1978 Progress Report
by
Robin D. Tems
PEDCo Environmental, Inc.
P.O. Box 20337
Dallas, Texas 75220
Contract No. 68-02-2603
Task No.
Program Element No. EHE623A
EPA Project Officer: James D. Kilgroe
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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11
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CONTENTS
TABLES .......... v
ILLUSTRATIONS ......... vi
ABBREVIATIONS . . . . . . . . . vii
UNITS .......... viii
ACKNOWLEDGMENT ......... ix
EXECUTIVE SUMMARY ........ x
SECTION 1: INTRODUCTION ....... 1
SECTION 2: REGULATORY AND TECHNICAL STATUS ... 2
2.1 Regulatory Status ...... 2
2.1.1 Air Quality Regulations . . . 2
2.1.2 Water Pollution Control Regulations . . 4
2.1.3 Solid Waste Disposal Regulations ... 7
2.2 Technical Status ....... 8
SECTION 3: DEVELOPMENT DIRECTIONS ..... 11
3.1 Market for Coal Cleaning ..... 11
3.2 Some Research and Development Objectives . . 12
3.2.1 Short Term Objectives . . . . . 12
3.2.2 Long Term Objectives ..... 13
SECTION 4: RESEARCH AND DEVELOPMENT PROGRESS . . 14
4.1 Technology Assessment and Development . . 14
4.1.1 Assessment of Coal Cleaning as an SO2
Emission Control Technique .... 19
4.1.2 Coal Cleanability ...... 28
4.1.3 Technology Assessment . . . . . 28
4.1.4 Homer City Coal Cleaning Plant . . . 42
4.1.5 Dense-Medium Cyclone Pilot Plant . . . 47
4.1.6 Coal Pyrite Flotation Circuit
Demonstration . . . . . . 47
4.1.7 Adsorption/Desorption Reactions in the
Desulfurization of Coal by a Pyrite
Flotation Technique . . . . . 48
4.1.8 High-Gradient Magnetic Separation of Coal
and Pyrite . . . . . . . 49
4.1.9 Surface Phenomena in the Dewatering of
Coal ........ 51
Xll
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CONTENTS (continued)
4.1.10 Reactor Test Project for Chemical Removal
of Pyritic Sulfur from Coal .... 52
4.1.11 Microwave Desulfurization of Coal . . 56
4.1.12 Battelle's Hydrothermal Process ... 58
4.1.13 Coal Cleaning Test Facility .... 61
4.1.14 Coal Preparation Plant Computer Model . . 62
4.1.15 Engineering/Economic Analysis of Coal
Preparation, Operation, and Cost ... 63
4.1.16 Chemical Coal Cleaning ..... 64
4.1.17 Hydrodesulfurization of Coal ... 64
4.1.18 Environmental Studies on Coal Cleaning
Processes ....... 66
4.2 Environmental Assessment ..... 66
4.2.1 Environmental Assessment Project ... 67
4.2.2 Coal Contaminants . . . . . . 79
4.2.3 A Washability and Analytical Evaluation of
Potential Pollution from Trace Elements . 81
4.2.4 Evaluation of the Effects of Coal Cleaning
on Fugitive Elements . . . . . 81
4.3 Development of Pollution Control Technology . 82
4.3.1 Control of Trace Element Leaching from Coal
Preparation Plant Wastes . . . . 82
4.3.2 Control of Blackwater in Coal Preparation
Plant Recycle and Discharge .... 86
4.3.3 Stabilization of Coal Preparation Waste
Slurries ....... 91
REFERENCES ......... 94
BIBLIOGRAPHY ......... 97
IV
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TABLES
1. Active interagency coal cleaning projects . . 15
2. SO- emission standards for coal-fired steam
generators ........ 20
3. Estimated 1985 coal consumption and S02 emission
regulations . . . . . . . .25
4. Summary of physical coal cleaning unit operations . 30
5. Summary of coal cleaning processes .... 34
6. Process performance and costs of major chemical
coal cleaning processes ...... 36
7. Operating costs of major chemical coal cleaning
processes . . . . . . .38
8. Cost effectiveness and other characteristics of
chemical coal cleaning processes . . . . 40
9. Typical moisture content of products by equipment
or process . . . . . . . 41
10. Homer City Plant product specifications ... 44
11. Homer City Plant - Phase-one acceptance tests
results ......... 46
12. Summary of preparation plant costs .... 65
13. Physical coal cleaning plants categorized by
states ......... 68
14. Proposed Priority 1 pollutants for coal cleaning
processes ......... 70
15. Pollutant effects on vegetation .... 75
16. Principal minerals from blackwater solids, Eastern
coal fields ........ 88
17. Characteristics of a typical Eastern blackwater
sample . . . . • • • • • 92
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ILLUSTRATIONS
1. Estimated cleanability of Northern Appalachian
COcl-L S • • » • * • • * * £ £
2. Estimated cleanability of U.S. coals ... 24
3. Annualized costs of SO2 and particulate control . 27
4. Preliminary block flow diagram for the Homer City
Coal Cleaning Plant in its interim configuration . 43
5. Meyers Process flow sheet ..... 53
6. Reactor test unit, Meyers Process . . . . 55
7. Gravichem Process flow sheet ..... 57
8. G. E. Microwave Process flow sheet .... 59
9. Battelle Hydrothermal Process flow sheet . . 60
10. Total dissolved solids vs. leachate volume
from column leaching study of limestone refuse
mixtures . ...... .85
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ABBREVIATIONS
AEP American Electric Power Service Corporation
BACT Best available control technology
BAT/BATEA Best available control technology economically available
BPT Best practical control technology currently available
CCC Chemical coal cleaning
CPPDF Coal preparation process development facility
DOE U. S. Department of Energy
EPA U. S. Environmental Protection Agency
EPC Estimated permissible concentration
EPRI Electric Power Research Institute
FGD Flue gas desulfurization
FWPCA Federal Water Pollution Control Act
HGMS High-gradient magnetic separation
IERL-RTP EPA Industrial Environmental Research Laboratory,
Research Triangle Park
IGT Institute of Gas Technology
JPL Jet Propulsion Laboratory, California Institute of
Technology
LASL Los Alamos Scientific Laboratory
MEG Multimedia environmental goal
NEP National Energy Plan
NSPS New source performance standards
PCC Physical coal cleaning
Penelec Pennsylvania Electric Company
PZC Point of zero charge
RCRA Resource Conservation and Recovery Act, 1976
ROM Run-of-mine
RTU Reactor test unit
SIP State Implementation Plan
TSS Total suspended solids
TVA Tennessee Valley Authority
USBM U. S. Bureau of Mines
UMW United Mine Workers of America
Vll
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UNITS
The Systems International d1Units (S.I.) is used as far as
practicable in this report.
The basic units with their equivalents are:
meter (m) =
kilogram (kg)
newton (N) =
joule (J) =
Fractions and multiples:
3.281 feet
2.205 pounds
4.5 poundals (approximately)
9.47 x 10~4 Btu
10 3 milli
10
10
10
-6
-9
-12
micro
nano
pico
m
y
n
P
10
10
10
kilo
mega
9
giga
12 tera
k
M
G
T
In addition the following conversions are used:
metric ton* (tonne) = 1000 kg = 1 Mg
short ton* = 2000 pounds = 0.907 metric ton
long ton* = 2240 pounds
* In this report ton1 always denotes a short ton1.
Vlll
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ACKNOWLEDGMENTS
This report presents summaries of work funded under the EPA
interagency coal cleaning program. The author acknowledges the
work of government and contractor personnel whose work is documen-
ted here. They are listed in Table 1, page 16, and in the refer-
ence list.
The author also wishes to acknowledge James D. Kilgroe {EPA
Project Officer) and Richard Hucko, authors of the paper entitled
"Interagency Coal Cleaning Technology Developments", upon which a
major portion of this report is based.
IX
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EXECUTIVE SUMMARY
The progress of the interagency coal cleaning program for
1977 has been reviewed. The year has been one of transition.
Potential applications of coal cleaning, and hence research and
development goals, have been greatly affected by new environmen-
tal legislation and impending energy legislation. The Clean Air
Act Amendments of August 1977 have significantly modified previous
clean air legislation, especially as related to its potential
impacts on the use of coal cleaning technology. Regulations
proposed by EPA effectively preclude the use of coal cleaning as
a sole method for complying with SO- standards in new electric
utility boilers. New water regulations limit the concentration
of pollutants in effluents from mining and coal preparation
facilities.
Research into the methodology and economics of physical coal
cleaning has continued. The first phase of a physical coal
cleaning plant at Penelec's Homer City Generating Station has
been commissioned and has undergone acceptance tests. Further
operation awaits the completion of the second phase of the plant,
which is expected soon. The plant will be capable of producing
medium- and low-sulfur coals to meet Federal and Pennsylvania
emission standards of 0.52 yg SO-/J (1.2 Ib SO^/IO Btu) and
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1.7 yg SO-/J (4.0 Ib SO-/10 Btu) respectively. In conjunction
with the Homer City project, investigations are being carried out
in order to optimize the performance of dense-medium cyclones.
The U. S. Department of Energy (DOE) is conducting these tests at
Bruceton, Pennsylvania. Coal cleaning by flotation is also being
studied. A two-stage coal/pyrite flotation demonstration circuit
has been installed in the Lancashire No. 25 preparation plant.
In an associated project, the University of Utah is studying
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adsorption/desorption reactions in the desulfurization of coal by
flotation. The technique of high-gradient magnetic separation,
which has been utilized commercially in the purification of
kaolin clay, is being studied by the General Electric Company for
application in coal cleaning. A DOE physical coal cleaning test
facility has been designed and is soon to be constructed. The
facility is needed so that technology or equipment developed by
DOE can be demonstrated to industrial representatives in a fully
integrated coal preparation plant. Unbiased engineering data
thus can be provided on a scope not previously possible. The
University of Pittsburgh has completed the first phase in the
development of a computer program that will simulate coal prepara-
tion plant operations. The program will predict outputs of clean
coal and refuse for given plant designs and raw coal feed.
Hoffman-Muntner Corporation has recently completed a study to
identify the costs associated with various physical coal cleaning
processes. Eight preparation plants are discussed.
The development of chemical coal cleaning technology has
been studied. A major review of the process technologies and the
economics of the most advanced chemical coal cleaning processes
have been discussed in detail. For the Meyers Process, a
0.3 Mg/h (1/3 ton/h) Reactor Test Unit (RTU) has been commissioned
and operated for a period of 4 months to evaluate various key
process steps. However, the RTU has been closed down due to
corrosion problems in the main reactor vessel. Continued testing
will be dependent upon an evaluation of potential process market
applications as affected by the Clean Air Act Ammendments of 1977.
Microwave desulfurization of coal, developed by General Electric,
is discussed. The Battelle hydrothermal process is also reviewed.
This process is still only at a laboratory scale stage of develop-
ment but significant progress has been made in improving unit
operations dealing with leachant-coal separation, leachant regen-
eration, and dewatering resulting in reduced moisture content of
the coal product. The Institute of Gas Technology's hydrodesul-
furization process is reported. This process could prove to be
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extremely important in the treatment of coal with a high organic
sulfur content.
An extensive review of the environmental impact of coal
cleaning has been started. Programs to characterize the possible
hazardous pollutants and to establish their maximum permissible
concentrations in coal preparation plant waste streams have been
initiated. The effects of coal preparation pollutants upon
humans, aquatic biota, terrestrial biota, and the total ecosystem
are being studied. Programs designed to control these pollutants
have been inititated and are reported in detail.
Xll
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SECTION 1
INTRODUCTION
Expanded coal production and use is a major goal of our
National Energy Plan. A corollary goal is the containment of
adverse environmental effects from coal use.
Coal beneficiation or cleaning is an important step in the
coal energy cycle. Coal cleaning is used to remove extraneous
mineral matter and mining residue. It can also be used as a
cost-effective means of removing sulfur from metallurgical coke
and from boiler fuels burned to comply with SO- emission regula-
tions.
Coal cleaning processes generate waste products that must be
controlled and disposed of in an environmentally sound manner.
In 1976, more than 330 Tg (370 million ton) of coal were physi-
cally cleaned, generating more than 97 Tg (107 million ton) of
coal cleaning residues. Leachates from improper waste disposal,
particulate emissions from thermal drying, and fugitive dust from
coal handling pose health and ecological threats.
Tve U. S. Environmental Protection Agency (EPA) is conducting
an interagency energy/environmental program, divided into three
basic elements. The principal objectives of these subprograms
are to (a) assess and develop coal cleaning technology for removing
pollutant-forming contaminants from coal, (b) evaluate the environ-
mental impacts of coal cleaning processes, and (c) develop
improved methods of controlling pollution from coal preparation.
This annual report summarizes the progress of the interagency
coal cleaning research and development program in 1977 and
regulatory activities related to coal cleaning. It includes an
analysis of future coal cleaning research and development prior-
ities.
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SECTION 2
REGULATORY AND TECHNICAL STATUS
Research and development activities under the interagency
coal cleaning program are responsive to changing regulatory
requirements and energy goals. A review of current regulatory
activities and the status of coal cleaning technology provides
the context for discussion of progress on recent coal cleaning
research and development.
2.1 REGULATORY STATUS
2.1.1 Air Quality Regulations
In accordance with provisions of the Clean Air Act Amend-
ments of 1970, EPA has set primary and secondary ambient air
quality standards, which regulate pollutant levels in order to
protect human health and public welfare (property, plant life,
and animal life). Ambient air pollutants specified in current
EPA regulations relating to coal use include sulfur oxides,
nitrogen oxides, and total suspended particulates.
Section 111 of the 1970 Clean Air Act Amendments requires
that EPA promulgate emission standards for new stationary sources
(sources constructed after the date the regulations are proposed).
These new source performance standards (NSPS) specify emission
limits only; they do not prescribe types of control systems.
Therefore, the owner/operator may select any type of control
system, but the standards must be achieved without the privilege
of variances or exemptions. The Clean Air Act Amendments of
August 1977 significantly modified previous clean air legislation,
especially as related to potential impacts on the use of coal
cleaning technology. These Amendments specify that all new
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stationary sources regulated by EPA must: (a) use best available
control technology (BACT); (b) use a method of continuous pollu-
tion control; (c) achieve a percentage reduction of the regulated
pollutants from fossil-fuel-fired boilers. In the case of fossil-
fuel-fired steam generators, any reduction of a pollutant by
post-extraction fuel processing may be credited to the percentage
reduction requirement.
EPA will soon propose revised NSPS for fossil-fuel-fired
boilers used to generate electrical energy. The regulations under
consideration require an 85 percent reduction in sulfur between
extraction and stack gas emissions, and specify that the sulfur
emissions cannot exceed 520 ng S02/J (1.2 Ib SO2/10 Btu) of
boiler heat input. Emissions below a minimum level
(86 to 214 ng S02/J [0.2 to 0.5 Ib S02/106 Btu]} would be exempted
from the percentage reduction requirement. Promulgation of these
regulations would effectively preclude the use of coal cleaning
as a sole method for complying with SO2 standards in new electrical
utility boilers.
Other important provisions of the 1977 Clean Air Act Amend-
ments that relate to coal cleaning include the prevention of
significant deterioration of air quality in clean air regions,
the siting of sources in nonattainment areas, the periodic review
of State Implementation Plans (SIP) for complying with National
Ambient Air Quality Standards, and the setting of emission stand-
ards for potentially hazardous pollutants. The stringency of
regulations for nondeterioration and clean air regions may neces-
sitate the use of coal cleaning in combination with flue gas
desulfurization (FGD) to comply with SO- emission standards.
Tightening and strict enforcement of emission standards under SIP
may expand the market for physically or chemically cleaned coals.
Potentially hazardous pollutants that EPA must consider
regulating include arsenic, beryllium, mercury, lead, and poly-
cyclic organic matter, all of which are emitted from coal-fired
boilers. If EPA decides that these pollutants from coal combustion
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must be regulated, then removal of some of these contaminants by
coal cleaning may be an effective control method.
2.1.2 Water Pollution Control Regulations
Federal control of water pollution sources associated with
coal production, preparation, and consumption is achieved through
the issuance of discharge permits that specify limits on dis-
charged effluents. Effluent guidelines are presently based on
the best practicable control technology currently available (BPT)
and must be based on the best available technology economically
available (BATEA or BAT) by 1983, except where modified require-
ments are in order, pursuant to Section 301 (c) of the Federal
Water Pollution Control Act (FWPCA). Effluent regulations are
also being issued for new sources. These new source performance
standards, mandated by FWPCA Section 306, are intended to be the
most stringent standards applied.
State control of water pollution sources associated with
coal preparation is achieved through the issuance of permits
independently or under the National Pollutant Discharge Elimina-
tion System. The permits, which contain limits on the effluents
discharged, are issued to each discharger. The objective of such
control systems is to achieve or maintain specified ambient water
quality standards, which are primarily a state responsibility.
The Federal laws are intended to aid in achievement of state
standards; however, EPA retains the authority to veto state
plans.
On May 13, 1976, EPA promulgated interim final effluent
guidelines for four subcategories of existing sources: coal
preparation plants; coal storage, refuse storage, and coal
preparation plant ancillary areas; acid or ferruginous mine
drainage; and alkaline mine drainage. More than ten lawsuits
were consolidated and are now pending before the U.S. Court of
Appeals for the Fourth Circuit.
On April 26, 1977, EPA promulgated final regulations that
incorporated several revisions to the interim final effluent
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guidelines published in 1976. Subpart B of these regulations
addresses discharges from coal preparation plants and associated
areas, including discharges that are pumped, siphoned, or drained
from coal storage, refuse storage, and coal preparation plant
ancillary areas. Included under these regulations are discharges
related to the cleaning or beneficiation of coal of any rank,
including bituminous, lignitic, and anthracitic.
The regulations establish the concentrations of pollutants
that may be discharged after application of BPT treatment. These
limitations differ for discharges that are normally acidic prior
to treatment as opposed to those that are normally alkaline. For
acidic conditions, the regulations specify limits on pH and the
discharge of total iron, manganese, and total suspended solids
(TSS). For alkaline conditions, the regulations limit pH and the
discharge of total iron and TSS.
On September 19, 1977, EPA published proposed NSPS for the
coal mining point source category. These standards establish the
concentrations of the pollutants that may be discharged after
application of the best available demonstrated control technology.
These limitations apply to discharges from facilities that recycle
process wastewater and differ according to whether discharges are
normally acidic or alkaline prior to treatment. Pollutants
regulated include total iron, manganese (acidic conditions only),
TSS, and pH. The regulations stipulate that discharges shall not
be made from facilities that do not recycle process wastewater.
In 1975, EPA was taken to court by several environmental
groups who claimed that EPA had not done a complete job in
assessing the pollution of surface waters by industry. On
June 7, 1976, the courts decided in favor of the environmental-
ists, and the machinery for the review of effluent guidelines was
set in motion.
First of all, EPA must review its BAT guidelines in the
light of the priority pollutants. Designation of these priority
pollutants arose from the court case. They consist of approxi-
mately 65 compounds or classes of compounds that EPA had failed
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to regulate or to take into consideration in the earlier guide-
lines. The process of naming specific compounds within the
classes resulted in a list of 129 priority pollutants.
The courts set deadlines for EPA, aimed at implementing BAT
by 1983. The first step is a proposed rule-making by September 30,
1978. By December 31, 1978, after time for comment, EPA is to
publish its proposed revised guidelines. Six months later
(June 30, 1979), the revised guidelines are to be promulgated.
This will give industry four years to implement BAT. However, a
4-month strike by the United Mine Workers of America (UMW) inter-
fered with this schedule. Consequently EPA and the National Coal
Association are preparing to request a 6-month delay in the
deadlines.
The BAT Review is a three-phase study, the first two phases
dealing with technology and the third with economics. The
technology phases, centering on the priority pollutants, became
known as the screening and verification phases. The object of
the screening phase is to determine the presence or absence of
the priority pollutants; the object of the verification phase is
to confirm the presence of the pollutants and to determine the
concentrations. During these two phases, plants are being visited
to obtain both technical and economic data. Factors that would
affect the economics of a treatment technology are being deter-
mined at each site visited. These factors include plant capacity,
age, and location; type of process; source of raw materials; end
use of product; capital cost; capital recovery; and operating
costs. This information is then used to determine the impact and
cost-effectiveness of a treatment technology.
The screening phase for the coal mining industry has been
completed. Plans are being made to begin the verification phase,
which has been delayed by the UMW strike.
In the screening phase, 18 coal preparation plants were
visited. Of these, only two were not sampled, one because the
plant was closed by a strike and the other because there was no
point of discharge.
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In addition to the screening tests for the 129 priority
pollutants, analyses were made for classic water pollutant
parameters and for some elements not on the priority pollutant
list. Of the 129 priority pollutants, 24 were found in water
from preparation plants and associated areas. Additionally,
12 elements of concern were found that were not on the priority
pollutants list. Some of the identified pollutants may be
artifacts of the analytical procedures; hence, additional tests
will be required to evaluate their authenticity.
2.1.3 Solid Waste Disposal Regulations
Solid wastes generated from coal preparation are generally
subject to land disposal. Although Federal guidelines for land
disposal of solid wastes are nonspecific with regard to quanti-
ties that can or cannot be disposed of, all facets pertaining to
land disposal sites are covered by requirements that the operator
conform to the most stringent water quality standards under the
provisions of the FWPCA. Leachate collection and treatment
systems are required at disposal sites as needed to protect
ground and surface water resources.
Provisions of the Solid Waste Disposal Act were signifi-
cantly modified by the passage on October 21, 1976, of the
comprehensive Resource Conservation and Recovery Act (RCRA) of
1976 (P.L. 94-580). Periods ranging from 90 days to 2 years were
provided for consummation of many of the actions called for by
the Act; hence, details of regulations to be promulated are not
yet available. Some of the general provisions of the Act are:
0 EPA must issue guidelines within 1 year defining sani-
tary landfills as the only acceptable land disposal
method that can be implemented. Open dumps are to be
prohibited.
0 Within 1 year EPA shall develop and publish proposed
guidelines for solid waste management.
0 Within 18 months EPA must propose: criteria for iden-
tifying hazardous wastes; regulations for generators of
hazardous wastes; regulations for transporters of
hazardous wastes; and performance standards for treat-
ment, storage, and disposal of hazardous wastes.
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0 Permit programs are to be managed by the states under
minimum guidelines, which are to be provided by EPA.
0 Each regulation promulgated shall be reviewed and,
where necessary, revised at least every 3 years.
It has not yet been determined whether coal refuse and
combustion ash will be classified as hazardous wastes. Such a
classification would require implementation of the most restric-
tive provisions of the Act.
2.2 TECHNICAL STATUS
Coal is a heterogeneous substance containing complex organic
molecules as well as inorganic molecules. It contains nearly all
of the naturally occurring elements. Some elements of environmen-
tal concern that are contained in significant quantities in coal
are arsenic, beryllium, cadmium, copper, lead, manganese, mercury,
nitrogen, selenium, sulfur, and zinc .
Elements of environmental concern may be classified by their
tendencies to occur either in the organic coal structure or in
the inorganic coal mineral phase. The relative amounts of
contaminants and the manner in which they are included in the
coal structure vary widely with different coals, thus affecting
the degree to which the various contaminants can be removed by
coal cleaning processes.
Physical coal cleaning (PCC) processess generally involve
crushing run-of-mine coal to a point where some of the mineral
impurities are released from the coal structure. The mineral and
coal particles are then separated by techniques usually based on
differences in the densities or surface properties of the particles,
Chemical coal cleaning (CCC) processes are being developed
to provide improved techniques for desulfurizing coals used for
steam and metallurgical applications. Chemical coal cleaning
processes vary substantially because of the different chemical
reactions that can be utilized to remove sulfur and other contam-
inants. Chemical coal cleaning processes usually involve grind-
ing the coal into small particles with or without chemical
8
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agents at elevated temperatures and pressures. The coal's
sulfur is converted into elemental sulfur or sulfur compounds
that can be physically removed from the coal structure. Some
chemical processes, such as the TRW-Meyers Process, remove only
pyritic sulfur. Others, such as the one under development by the
Department of Energy (DOE), are said to be capable of removing
organic sulfur as well.
Approximately half of all domestically consumed coal is
physically cleaned to remove mineral matter and mining residue.
A large proportion of metallurgical grade coal is cleaned to
remove sulfur, but cleaning operations for steam coal have not
previously been designed and operated to remove sulfur for
compliance with state and Federal SO2 emission standards. The
first steam coal preparation plant designed for such a purpose is
nearing completion at Homer City, Pennsylvania. The Tennessee
Valley Authority (TVA) is planning two other sulfur-removing
plants. None of these steam coal plants incorporates the most
advanced beneficiation techniques now used in the metallurgical
and mineral industries.
A number of coal cleaning processes are currently under
development. These processes are being developed to produce
desulfurized coals for use in complying with SC^ emission stand-
ards ^ . The Meyers chemical coal cleaning process, which is at
an advanced development stage, is being evaluated in a 0.3 Mg/h
(1/3 ton/h) test unit at Capistrano, California. At least eight
other processes are in various stages of laboratory development.
Many of these are reportedly capable of removing organic as well
as pyritic sulfur. With accelerated development, several chemical
processes could be ready for commercial demonstration within
5 or 10 years.
Coal preparation plants annually generate more than
90 million Tg (100 million ton) of waste. Interaction of air and
water in pyrite-rich wastes converts the pyritic sulfur to a
dilute sulfuric acid leachate. This leachate may have high
concentrations of dissolved trace elements or other potentially
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hazardous pollutants . Drainage of the leachate into ground
and surface waters may degrade water quality and affect human
health. Current knowledge of the relationships between coal
mineral properties, coal trace element concentrations, the
effects of weathering on the release of trace elements, and the
effects of various technologies in controlling trace element
pollution is rudimentary.
Coal and mineral dusts generated by handling, transporting,
and storing coal may contain high concentrations of hazardous
trace elements and compounds. Little is known about the composi-
tion of these dusts, their effects on human health, and the
degree to which dust emissions can be controlled.
Sludges from coal preparation plants present a disposal
problem. Some sludges are not easily dried, and others are
thixotropic. Either condition requires containment in a storage
pond. Techniques to solidify and dispose of sludge from coal
preparation plants are in an early stage of development.
Spent chemicals used in chemical desulfurization contain
many potentially hazardous trace elements and compounds. Little
is known about the techniques that will be needed to neutralize
and dispose of these wastes.
10
-------
SECTION 3
DEVELOPMENT DIRECTIONS
3.1 THE MARKET FOR COAL CLEANING
Requirements for control of SO2 pollution have created a
primary short-term market for coal cleaning. The degree to which
coal cleaning is used to meet these requirements depends upon the
specific sulfur emission standards, the desulfurization potential
of available coals, the costs of coal cleaning, and the costs of
alternative pollution control techniques. Other applications for
coal cleaning include the upgrading of subbituminous coals and
lignites and the preparation of coals for synthetic fuel conver-
sion processes. The primary emphasis of the interagency coal
cleaning program has been on environmental considerations.
The applicability of coal cleaning for compliance with SO2
emission regulations is contingent upon a number of regulatory
and technical uncertainties. Once these uncertainties have been
resolved, the use of coal cleaning will be defined largely by
market considerations (i.e., a determination of the most cost-
effective method of coal energy production considering the costs
of all pollution control requirements). Near-term applications
for compliance with SO2 emission standards are in doubt primarily
because of changing regulatory requirements mandated by the 1977
Clean Air Act Amendments. The Amendments require periodic review
of emission standards under SIP. Some regulations will be
tightened, especially in non-compliance regions and in areas
wishing to offset emission increases resulting from industrial
growth by reducing emissions from existing boilers.
Proposed revisions of NSPS for utility boilers would require
an 85 percent reduction in sulfur between extraction and emission.
11
-------
This would preclude physical coal cleaning as a sole method for
compliance with SO2 emission standards by these boilers. In some
instances a combination of coal cleaning and FGD may be more
cost-effective than FGD alone. Cases for which this combination
may be the most cost-effective strategy cannot be adequately
defined because of various uncertanties. The standards have not
been promulgated, and the emission averaging time has not been
specified. Moreover, some of the potential cost benefits and
liabilities associated with coal cleaning have not been quantified.
These include (a) the degree to which coal cleaning will reduce
coal sulfur variability, (b) the comparable costs for controlling
sulfur variability in coal by FGD, and (c) boiler operating and
maintenance cost benefits resulting from coal cleaning.
EPA also plans to set BACT standards for industrial boilers.
The level at which these standards are set will determine the
applicability of coal cleaning as an SO~ emission control strat-
egy in these boilers.
3.2 SOME RESEARCH AND DEVELOPMENT OBJECTIVES
Consideration of the above factors along with the current
status of coal cleaning technology allows projection of the near-
and long-term objectives for coal cleaning research and develop-
ment.
3.2.1 Short-Term Objectives
The short-term objectives of this program are listed as the
following:
0 Characterization of coal sulfur variability and the
degree to which coal preparation attenuates this vari-
ability.
0 Assessment of the potential of U.S. coals for desulfuri-
zation by physical methods, including techniques that
rely on surface properties as well as density differences
0 Development of improved fine coal cleaning techniques
that will provide for maximum pyrite removal with
minimum coal energy losses.
12
-------
0 Development of improved techniques for fine coal dewater-
ing and drying.
0 Evaluation of the environmental impacts of coal cleaning,
0 Development of technology to control trace elements in
leachate from coal preparation plant wastes.
0 Determination of the effects of coal cleaning on boiler
operating and maintenance costs.
0 Establishment of pollution control costs for coal
preparation processes.
0 Establishment of costs of alternative strategies for
compliance with SO,, emission standards by industrial
and utility boilers.
3.2.2 Long-Term Objectives
The following long-term objectives of this program have been
defined:
0 Characterization of U.S. coals and their mineral and
organic contaminants.
0 Development of advanced physical/chemical processes for
removing inorganic and organic contaminants from coal.
0 Development of techniques for the control of newly
regulated pollutants and pollutants from developing
coal cleaning technologies.
13
-------
SECTION 4
RESEARCH AND DEVELOPMENT PROGRESS
The interagency coal cleaning program is divided into three
major subprograms:
1. Assessment and development of coal cleaning processes;
2. Assessment of environmental impacts from coal cleaning;
3. Development of pollution control technology for coal
cleaning processes.
Government organizations participating in the program include
the Environmental Protection Agency, the Department of Energy,
the Department of Interior, and the Tennessee Valley Authority.
The program budget for fiscal 1978 was approximately $8 million.
The program is directed for EPA by the Industrial Environmental
Research Laboratory, Research Triangle Park, North Carolina.
Table 1 summarizes projects active during 1977-78 and cites the
sections of this report in which they are discussed.
4.1 TECHNOLOGY ASSESSMENT AND DEVELOPMENT
Improved techniques for preparation of fine coal are needed
to enhance sulfur removal and recovery of energy from coal. The
primary objectives of the technology assessment and development
activities are to evaluate the potential cleanability of U.S.
coals and the performance and costs of commercial equipment that
can be used for the beneficiation of fine coal. The program also
supports developments of chemical coal cleaning processes and
applied research to characterize the basic mechanisms governing
beneficiation processes.
14
-------
TABLE 1. ACTIVE INTERAGENCY COAL CLEANING PROJECTS
Project title (contract, grant,
or
interagency agreement)
TECHNOLOGY ASSESSMENT AND DEVELOPMENT
Coal Cleanability IAG-D6-E685
Coal Cleaning Technology Assessment
and Development (68-02-2199)
Interim Support for Homer City
Test Program (68-02-2639)
Dense-Media Cyclone Pilot Plant
(IAG-D6-685)
Demonstration of Coal-Pyrite
Flotation ( IAG-D6-E635)
Adsorption-Desorption Reactions
in Pyrite Flotation (IAG-D6-E685)
High-Gradient Magnetic Separation
(IAG-D5-E685)
Surface Phenomena in Dewatering
of Fine Coal (IAG-D6-E685)
Reactor Test Project for Chemical
Removal of Pyritic Sulfur from
Coal (68-0201880)
Discussed
in
Section
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.7
4.1.8
4.1.9
4.1.10
Organization
directing
work
DOEa
EPA
EPA/DOEb
DOEa/EPR!/
penelec/EPA
DOE3
DOE3
DOE3
DOE3
EPA
Organization
performing
work
DOE3
Versar, Inc.
Chem Systems/
Pennsylvania
Electric Co.
DOE3
Heyl and Patterson
Co. /Barnes and
Tucker Co.
University of Utah
General
Electric Co.
Syracuse
University
TRW Defense and
Space Systems
Group
Objectives
Determine desulfurization potential of U.S. coals by
size reduction and specific gravity separation.
Evaluate performance and costs of equipment for
removing sulfur from coal.
Provide test planning and initial test support for
the Homer City Coal Cleaning Demonstration Program.
Evaluate effects of cyclone design and operation
variables on separation of fine coal and pyrite.
Conduct commercial testing and operation of two-stage
coal -pyrite flotation process developed by DOE.
Evaluate the adsorption-desorption mechanisms that
control performance in the DOE two-stage coal-
pyrite flotation process.
Evaluate technical feasibility of high-gradient
magnetic separation for renoving pyrite from coal.
Evaluate phenomena governing the effectiveness of
surfactants in reducing the final moisture content
of coal vacuum filter cakes.
Evaluate Meyers chemical coal cleaning process in a
1/3 ton/h test reactor unit.
h--
Ul
Department of Energy, Coal Preparation and Analysis Laboratory, Pittsburgh, Pennsylvania
Department of Energy, Office of Environment, Washington, D.C.
(continued)
-------
TABLE 1. (continued)
Project title (contract, grant,
or
interagency agreement)
Microwave Desulfurization of
Coal (68-02-2172)
Battelle Hydrothermal Process
Improvement Studies (68-02-2187)
Coal Cleaning Test Facility
Coal Preparation Plant Computer
Model (IAG-D6-E685)
Engineering/Economic Analysis of
Coal Preparation Operation and
Cost (IAF-D6-E685)
Evaluation of Chemical Coal
Cleaning Processes ( IAG-D5-E685)
Hydrodesulfurization of Coal
(68-02-2126)
Environmental Studies on Coal
Cleaning Process (IAG-D5-E721
Discussed
in
Section
4.1.11
4.1.12
4.1.13
4.1.14
4.1.15
4.1.16
4.1.17
4.1.18
Organization
directing
work
EPA
EPA
DOEa
EPA/DOEa
DOEa
DOEC
EPA
EPA
Organization
performing
work
General
Electric
Battelle Columbus
Laboratories
Birtley Engineer-
ing Corp.
Williams,
Trebilocic and
Whitehead
DOEa, University
of Pittsburgh, and
Battelle
Hoffman-Muntner
Corp.
Bechtel
Institute of Gas
Technology
Tennessee Valley
Authority (TVA)
Objectives
Evaluate the feasibility of coal desulfurization
by microwave treatment.
Evaluate methods for liquid/solid separation and
leachant regeneration.
Design a DOE coal cleaning test facility. Provide
architectural and engineering plans.
Develop computer model capable of predicting
performance of coal preparation plants.
Determine costs of cleaning for eight represen-
tative coal preparation plants - from jig plants
to complex dense-medium plants.
Evaluate relative costs and performances of
selected chemical coal cleaning processes.
Evaluate desulfurization of coal by mild oxidative
treatment followed by devolatil ization.
Evaluate technology for controlling pollution at
TVA coal preparation plants.
C0epartment of Energy, Office of Energy Technology, Washington,
(continued)
D.C.
-------
TABLE 1. (continued)
Project title (contract, grant,
or
interagency agreement)
Discussed
in
Section
Organization
directing
work
Organization
performing
work
Objectives
ENVIRONMENTAL ASSESSMENT
Environmental Assessment of Coal
Cleaning Processes (68-02-2163
Trace Element Characterization of
Coal Preparation Wastes
(IAG-05-E681)
Trace Elements and Mineral
Matter in U.S. Coals (R804403)
Geology of Contaminants in Coal
(IAG-D6-E685)
A Washability and Analytical
Evaluation of Potential
Pollution from Trace Elements
(IAG-D6-E685
Evaluation of the Effects of Coal
Cleaning on Fugitive Elements
(IAG-D6-E685)
4.2.1
4.2.2
4.2.2
4.2.2
4.2.3
4.2.4
EPA
EPA/DOE3
EPA
EPA
DOE3
DOEa
Battelle Columbus
Laboratories
Los Alamos
Scientific Lab-
oratory (LASL)
Illinois State
Geological Survey
U.S. Geological
Survey
DOE"
Bituminous Coal
Research, Inc.
Evaluate pollution resulting from coal cleaning
transportation, and storage. Evaluate coal cleaning
as an S02 emission control technique.
Characterize trace element and mineralogic associa-
tions in coal preparation wastes.
Characterize the elemental constituents and miner-
alogy of U.S. coals.
Characterize coal resources west of the Mississippi
as to their elemental and mineralogic composition.
Evaluate the geological factors that affect or
control coal clcapability.
Evaluate partitioning of trace elements in 10 U.S.
coals during specific-gravity separation.
Evaluate partitioning of trace elements during
preparation and use.
(continued)
-------
TABLE 1. (continued)
Project title (contract, grant,
or
interagency agreement)
DEVELOPMENT OF POLLUTION
CONTROL TECHNOLOGY
Control of Trace Element
Leaching from Coal
Preparation Wastes
(IAG-D5-E681)
Control of Blackwater in Coal
Preparation Plant Recycle
and Discharge (IAG-D5-E685
Stabilization of Coal
Preparation Waste Sludges
(IAG-D5-E685)
Discussed
in
Section
4.3.1
4.3.2
4.3.3
Organization
directing
work
EPA/DOEb
DOE3
DOEa
Organization
performing
work
LASL
Pennsylvania
State University
Oravo Lime
Objectives
Determine Teachability of trace elements from
coal preparation wastes and evaluate pollution
control methods.
Characterize blackwater generated by coal
preparation plants and assess potential
potential control methods.
Collect coal preparation plant sludges and
perform laboratory stabilization tests.
oo
-------
4.1.1 Assessment of Coal Cleaning as an SO,, Emission Control
Technique
Passage of the 1977 Clean Air Act Amendments provides new
emphasis for the assessment of coal cleaning as an SO- emission
control technique. New regulatory actions in response to this
legislation will significantly change the conditions under which
coal cleaning can be used as a method of complying with SO-
emission standards. Studies are in progress to assess the appli-
cability of coal cleaning to reduce SO- emissions to the required
levels in the following regulatory circumstances:
0 Existing boilers regulated under SIPs.
0 Current Federal NSPS for coal-fired utility boilers.
0 Revised NSPS for coal-fired utility boilers.
0 NSPS to be promulgated for industrial boilers.
The results of portions of these studies, although prelimin-
ary, warrant discussion.
Table 2 summarizes the SO- emission standards that are
expected to be applicable to coal-fired boilers by 1980. Import-
ant new mandates by the 1977 Clean Air Act Amendments are require-
ments for the use of BACT and for a percentage sulfur reduction
in addition to an emission limit.
(4)
An evaluation of U.S. Bureau of Mines (USBM) data suggests
that application of BACT to specific gravity separation, now
commonly used for coal de-ashing, can remove 25 to 55 percent of
the pyrite from U.S. coals. Moderate reductions in the coal top
size and density of separation to correspond to the best current
technology would reduce pyrite by 40 to 80 percent. Assuming
that all the sulfur remaining in the coal were converted to S02
upon combustion, burning of these coals would result in SO- emis-
~ g
sions ranging from 0.4 to 1.9 ug SO2/J (0.9 to 4.4 Ib S02/10 Btu) ,
Although more pyritic sulfur can be removed at these smaller
particle sizes and densities of separation, coal Btu losses would
increase to unacceptably high levels unless the high-density sink
fractions were upgraded (desulfurized) by further processing.
19
-------
TABLE 2. S02 EMISSION STANDARDS FOR COAL-FIRED STEAM GENERATORS
Application
Existing boilers
Current NSPS for
steam generators
Revised NSPS for
utility boilers3
NSPS for industrial
boilers
Sulfur
reduction, %
85b
Unkown
Emission limits,
ug so2/J
0.1 - 3.4
0.5
0.5 max.
0.1 - 0.2
floor
Unknown
Ib S02/106 Btu
0.2 - 8.0
1.2
1 .2 max.
0.2 - 0.5
floor
Unknown
Values under consideration.
85% minimum for 24-hour average. A provision of the standard
will permit a 75% minimum reduction and an exemption from
the 0.5 yg SCL/J level 3 days per month. This provision is to
allow for variations in fuel sulfur levels and in performance of
pollution control device.
20
-------
Probable operations would include pulverization, density separa-
tion, froth flotation, oil agglomeration, or chemical cleaning.
An alternative means of reducing loss of heating value is for the
preparation plant to produce multiple product streams to be used
in different boilers; high-sulfur coals could be used in boilers
with FGD or in boilers subject to less stringent S02 emission
regulations.
If experiments by Min and Wheelock on Iowa coals are applica-
ble to other U.S. coals, the best combination of physical cleaning
techniques are potentially capable of removing up to 90 percent
of the pyritic sulfur* . Combustion of coals cleaned to these
levels would produce emissions ranging from 0.3 to 1.5 yg S02/J
(0.8 to 3.5 Ib S02/106 Btu).
Chemical coal cleaning processes can remove 95 to 99 percent
of the pyritic sulfur and 25 to 40 percent of the coal organic
sulfur. Removal of 95 percent of the pyritic sulfur and 25
percent of the organic sulfur from U.S. coals would result in
(4)
total sulfur reductions in the range of 53 to 77 percent .
The sulfur content and sulfur removal potential of coal by
physical and chemical techniques vary among coal regions and
among coal beds in the same region* '. Figure 1 presents the
estimated energy content of the recoverable Northern Appalachian
coal reserves which can be cleaned to meet various S02 emission
levels. Less than five percent of the raw coal is capable of
meeting a standard of 0.4 yg SO2/J (1.0 Ib SO2/106 Btu). Crushing
to 10 mm (3/8 inch) and physically cleaning coal at a density of
1.6 or 1.3 Mg/m3 would increase the relative energy content of
coals available for compliance with an emission standard of
0.4 yg SO2/J (1.0 Ib SO2/106 Btu) to approximately 20 percent.
Chemical cleaning of appropriate coals by processes that can
remove 95 percent of pyritic sulfur and 20 percent of organic
sulfur would provide more than 6.5 x 10 J (6.2 x 10 Btu);
i.e., more than 26 percent of the total reserves would be capable
of meeting a standard of 0.4 yg SO2/J (1.0 Ib SO2/10 Btu).
21
-------
to
10
u
U-
o
o
ee.
COAL SULFUR EMISSION ON COMBUSTION. Ib SOg/106 Btu
2.0 4.0 6.0 8.0
/// .-•• /
'I •' /
'
/ RAW COAL
— • - PCC 38mn (1-1/2 INCH) 1.6 SP. GR.
PCC 9.5mm (3/8 INCH) 1.6 OR 1.3 SP. GR
MEYERS PROCESS
0.95 PYRITE S, 0.20 ORG. S REMOVED
'BEST' FOR RESERVE
/ -.:.-.
/ —
f / /
ENERGY CONTENT OF RECOVERABLE
RESERVES:
1.82 x 10 J (1.7 * 1018Btu)
1.0 1.5 2.0 2.5 3.0
COAL SULFUR EMISSION ON COMBUSTION, ug SO^/J
Figure 1. Estimated cleanability of Northern Appalachian coals,
-------
Figure 2 presents similar data on the cleaning potential of
U.S. coals. Although Figure 1 and Figure 2 indicate that physi-
cal and chemical coal cleaning can be used to provide coals
capable of meeting a variety of emission standards, new Federal
standards requiring sulfur reductions above about 50 percent
would generally preclude the use of physical cleaning as a sole
method of complying with SO2 emission standards. Sulfur reduc-
tion requirements of 80 percent or more would eliminate the use
of chemical coal cleaning as an effective technology for compli-
ance with these standards.
The demand for physical or chemical coal cleaning will
depend upon the relative amounts of coals capable of meeting
various sulfur emission control standards and the relative costs
of other SO2 emission control techniques. In 1975, approximately
423 Tg (467 million ton) of coal were consumed, primarily in
utility, industrial, and commercial boilers . Under the
National Energy Plan (NEP) coal consumption for these uses and
for non-boiler, industrial applications is expected to exceed
958 Tg (1057 million ton) per year in 1985.
In 1975, virtually all coal-burning boilers were subject
only to state regulations for existing boilers. Table 3 presents
estimates of the 1985 coal consumption by boiler capacity and the
emission levels with which each boiler must comply. Even consid-
ering that few coals could be desulfurized to levels below
0.5 yg S02/J (1.2 Ib SO2/106 Btu), physically cleaned coals could
provide complying fuels to meet 79 percent of the projected steam
coal demand in 1985 (if a high percentage sulfur removal is not
required). These projections are, of course, highly dependent
upon impending energy legislation and new emission standards to
be promulgated by EPA.
Comparisons of pollution control costs are complex. Factors
unique to a given application and site often determine which
pollution control option is most cost-effective. Simplified cost
comparisons can be made by evaluating the ranges of annual costs
for coal cleaning and FGD.
23
-------
COAL SULFUR EMISSION ON COMBUSTION. Ib S02/106 Btu
4.0
6.0
100
8.0
80 -
o
UJ
£
60 -
o
u_
o
5
DC
TREATMENT METHOD
RAW COAL
PCC 9.5imn (3/8 INCH) 1.3 SPECIFIC GRAVITY
0.95 PYRITE S, 0.40 ORG. S REMOVED
'BEST1 FOR RESERVES
ENERGY CONTENT OF RECOVERABLE
RESERVES:
9.3 x 1021J (8.8 x 1018Btu)
0.0
0.5
1.0 1.5 2.0 2.5 3.0
COAL SULFUR EMISSION ON COMBUSTION, u9 S02/J
Figure 2. Estimated cleanability of U.S. coals.
-------
TABLE 3. ESTIMATED 1985 COAL CONSUMPTION AND S02 EMISSION REGULATIONS
to
Ul
Boiler category
Utility
Industrial and commercial c'c'
Total
Projected 1985 consumption9 listed by emission interval,
yg S02/J (Ib S02/106 Btu)
<0.52
H.2)
204 b
14
218
0.52 to <0.86
( 1.2 to <2.0)
403
203
606
0.86 to <1.72
(2.0 to <4.0)
113
52
165
>1.72
(>4.0)
59
9
68
Total
779
278
1057
Projected total 1985 consumption corresponding to NEP (million short tons, approximately
equivalent to Tg).
One-third utility boilers constructed after 1975 are assumed to comply with revised NSPS
of 0.21 to 0.34 S02/J (0.48 to 0.8 Ib S02/10 Btu). Two thirds of all new utility boilers
constructed after T975 are assumed to comply.
"The distribution of use for all categories of existing boilers is assumed to comply as
follows: <0.52 yg SO./J (<1.2 Ib SO,/10D Btu), 20%; 0.52 to <0.86, (1.2 to <1.48), 35%;
0.86 to <1.72, (1.48 to <4.0), 30%; a.72 (>4.0), 15%.
All new industrial and commercial boilers are assumed to comply with emission standards
of 0.64 to 0.86 yg S09/J (1.48 to 2.0 Ib S09/10D Btu).
-------
Utility and industrial FGD systems now in use have demon-
(8 9 10)
strated S07 removal efficiencies that exceed 90 percent ' '
FGD costs are sensitive to the type of FGD system, boiler capa-
city, boiler capacity factor, and level of desulfurization
required. Annual FGD costs increase with decreasing boiler
capacity factor, and increasing sulfur removal.
Annual coal cleaning costs are sensitive to plant capacity,
plant complexity, and coal replacement costs. Coal replacement
costs are defined as the costs of coal energy that must be
discarded with the plant residue (carbon and mineral matter),
Plant complexity increases with the number of different process
operations involved.
Figure 3 presents estimates of cost ranges for annualized
SO, and particulate control costs for PCC, CCC, and FGD. Parti-
6
culate control costs of $0.095/GJ ($0.10/10 Btu) are included so
that the costs of coal cleaning can be compared with the costs of
FGD, which include costs for particulate control. An analysis of
the cost ranges in Figure 3 and of the desulfurization potential
of physical and chemical cleaning indicates the following:
1. Where technically feasible and where a low percentage
sulfur extraction is satisfactory for meeting the
emissions regulations, cost savings can be realized by
the use of PCC for coals fired in utility and industrial
boilers, especially small boilers with low capacity
factors.
2. PCC probably cannot be used to meet revised NSPS for
utility boilers, unless it is used in combination with
FGD.
3. Where a high S0_ removal efficiency is required, FGD
appears to be more competitive than CCC, especially in
the case of large base-load utility boilers. CCC could
possibly be used in a cost-effective manner in small
industrial boilers with low capacity factors.
4. The most probable use of CCC is in combination with PCC
to yield lower sulfur levels than are available by PCC.
In some cases, under current state and Federal standards,
the S02 control costs of using FGD in combination with PCC may be
lower than those for using FGD alone . Studies comparing
26
-------
3.00
CO
2.00
to
1.00-
OO
I—
OO
o
o
O
o;
o
o
oo
oo
0.50
0.40
0.30
0.20
I
100
200
500
1000
2000
5000
10,000
BOILER CAPACITY, GJ/h (~10°Btu/h)
Figure 3. Annualized costs of SO0 and particulate Control.
-------
the costs of a combination of PCC and FGD with those of FGD alone
in meeting a standard of 80 to 90 percent sulfur removal are not
complete.
4.1.2 Coal Cleanability
The DOE Coal Preparation and Analysis Group at Bruceton,
Pennsylvania, is continuing laboratory experiments to determine
the effect of crushing and gravimetric separation on the libera-
tion and removal of pyritic sulfur from coals from the principal
coal fields of the United States. Information generated from
this study is necessary to assess the impact that physical coal
cleaning would have on emissions from stationary combustion
sources.
In 1976, a report was published on the sulfur reduction
potential of 455 coal samples from six major U.S. coal fields .
Since then an additional 220 samples have been collected from the
Western and Appalachian Region States. During the past year
washability analyses were completed on 31 raw coal channel
samples collected from Maryland, Ohio, and Pennsylvania. In
addition, 4 lignite samples from Arkansas and 7 lignite samples
from Texas were tested.
The data show that, on average, the lignite samples contained
15.9 percent ash, 0.23 percent pyritic sulfur, and 1.09 percent
total sulfur on a moisture-free basis. The average moisture was
30.9 percent, and the average heating value was 24.1 MJ/kg
(10,377 Btu/lb). The survey shows that only two samples from
Arkansas, those which contained less than 0.7 percent organic
sulfur, could be upgraded to meet the NSPS of 0.5 yg SO-/J
c *•
(1.2 Ib SO-/10 Btu). All but one of the Texas lignite samples
contained more than 1 percent sulfur; however, since most of this
sulfur was organic, none of the Texas samples could be upgraded
to meet current NSPS.
4.1.3 Technology Assessment
A major 3-year project to assess technology for physical and
chemical desulfurization of coal began in January 1977. The
28
-------
project is being conducted by Versar, Inc., with the assistance
of Joy Manufacturing Company's Denver Equipment Division. The
program includes six major technical tasks:
1. Collection of existing data on sulfur removal by physical
coal cleaning equipment.
2. Generation of new data and evaluation of physical coal
cleaning technology for sulfur removal.
3. Evaluation of equipment for fine coal dewatering and
handling.
4. Assessment of coal preparation requirements for synthetic
fuel conversion processes.
5. Performance of studies of physical coal preparation
processes to evaluate the trade-offs between sulfur
removal and costs.
6. Evaluation of chemical coal cleaning processes.
The task methodology includes literature and field surveys,
compilation of data from many representative sources (Bureau of
Mines and other governmental organizations carrying out research
in the field, industrial research facilities, and commercial
sources), testing and evaluation of currently operational equip-
ment, and cost evaluation of various processes.
More than 55 percent of the coal used in the United States
is subjected to PCC. The degree of cleaning varies widely, and
the process technologies range from simple mechanical removal of
rock and dirt to operation of complex coal benefication plants
for removal of heavier contaminants and noncombustible minerals.
At the present time, however, most plants are designed primarily
for removal of ash and not for removal of pyrite from coal.
Sophisticated systems for recovering fines and pyrite are still
under development. Versar has extensively reviewed various
physical coal cleaning processes ranging from established techno-
logies such as hammermills, crushers, and jigs to recent develop-
ments and variations of the dense-medium cyclone and the applica-
tion of froth flotation to coal cleaning. The processes are
summarized in Table 4.
29
-------
TABLE 4. SUMMARY OF PHYSICAL COAL CLEANING UNIT OPERATIONS
Unit operation
Jigging
Tables
U)
o
Dense-medium
HydrocycTones
Description
A pulsating fluid stratifies coal
particles in increasing density
from top to bottom. The cleaned
coal overflows at the top.
Pulverized coal and water are
floated over a table shaken with
a reciprocating motion; lighter
coal particles are separated to
the bottom of the table, while
heavier, larger, impure particles
move to the sides.
Coal is slurried in a medium with
a specific gravity close to that at
which separation is to be made;
lighter, purer coal floats to the
top and is continously skimmed off.
The separating mechanism is de-
scribed as taking place in the
ascending vortex. The high and
low specific gravity particles
moving upward in this current
are subjected to centrifugal
forces effecting separation.
Remarks
Most popular and least expensive
coal washer available, but may not
give accurate separation. Sizes:
3.4 to 76 mm (6 mesh to 1 in.)
Sizes: 0.15 to 6.4 mm (100 mesh to
1/4 in.)
Advantages: ability to make sharp
separation at any specific gravity
within the range normally required;
ability to handle wide range of
sizes; relatively low capital and
operating costs relative to high
capacity and small space requirements;
ability to handle fluctuations in
feed quantity and quality. Sizes:
0.59 to 200 mm (28 mesh to 8 in.)
If maximum pyrite reduction and
maximum clean coal yield are to be
obtained, supplemental processes such
as cyclone classifying, fine-mesh
screening and froth flotation are
necessary (on-stream process). Hydro-
cyclones presently are used in the U.S.
to clean flotation-sized coal, but can
be used for coal as coarse as 64 x 0 mm
(1/4 x 0 in.)
(continued)
-------
TABLE 4. (continued)
Unit operation
Humphrey spiral
Launder-type
washers
U)
Pneumatic
Description
Coal-water slurry is fed into
a spiral conduit. As it flows
downward stratification of the
solids occurs with the heavier
particles concentrated in a band
along the spiral. An adjustable
splitter separates the stream into
two products - a clean coal and
the middlings.
Raw coal is fed into the high end
of a trough with a stream of
water. As the stream of coal and
water flows down the incline,
particles having the highest
settling rate settle into the
lower strata of the stream.
These are the middling or refuse
particles. The clean coal par-
ticles gravitate into the upper
strata before separation.
Coal and refuse particles are
stratified by means of pulsating
air. The layer of refuse formed
travels forward into pockets or
wells from which it is withdrawn.
The upper layer of coal travels
over the refuse and is removed
at the opposite end.
(continued)
Remarks
Has shown significant ash and sulfur
reduction on 0.42 x 0 mm (35 x 0 mesh)
Middle Kittanning coal.
Three types of launders are recognized
based on mode of transport. Sizes:
4.76 to 76 mm (4 mesh to 3 in.)
Most acceptable preparation method
from the standpoint of delivered
heating value cost. Sizes: up to
6.4 mm (1/4 in.)
-------
TABLE 4. (continued)
Unit operation
Froth flotation
u>
to
Two-stage flota-
tion for pyrite
Description
A coal slurry is mixed with a
collector to make certain frac-
tions of the mixture hydrophilic.
A frother is added and finely
disseminated air bubbles are
passed through the mix. Air-ad-
hering particles are floated to
the top of the remaining slurry,
and are then removed as a concen-
trate.
Experimental coal flotation
process in which the coal is
floated while high-ash impurities
are rejected. The froth concen-
trate is then repulped in O,
treated with an organic colfoid to
depress the coal. A xanthate col-
lector and alcohol frother are
added and then refloated.
Remarks
Froth flotation is used to reduce
pyrite in English coals; the flo-
tation of coal refuse to obtain
salable pyrite is uneconomical in
view of today's poor sulfur market;
if ethyl xanthate is used as the
collector, it is aborbed into coal
pyrite in such a manner as to make
it ineffective for flotation. Sizes:
1.17 to 0.044 mm (14 to 325 mesh)
Frothing agent is methylisobutyl
carbinol; pH regulators are NaOH and
HCl. Coal depressant is Aero depres-
sant 633. Pyrite flotation col-
lector is potassium amyl xanthate. In
general the ratio of readily
floatable coal to total float-
able coal increases with an increase
in fixed carbon content. Therefore,
increased rank yields an increased
ratio.
-------
An evaluation of current chemical coal cleaning processes
has also been completed. Twenty-nine different processes were
reviewed, eleven of which were selected for comparative evaluations.
Estimated annual operating costs for the eleven processes (includ-
ing the cost of coal, calculated at $23/Mg ($25/ton) ranged from
$36/Mg ($40/ton) to $60/Mg ($66/ton). Chemical coal cleaning
processes are still under development, however, and none of the
processes has been tested in a unit larger than 8 Mg/day
(9 ton/day). Consequently, performance and cost comparisons are
relatively uncertain. The CCC processes vary substantially
because of the many possible reaction mechanisms and chemicals
that can be used to remove sulfur and other reactive impurities
from coal. Most chemical processes reportedly remove 90 percent
of the pyritic sulfur, and several remove up to 40 percent of the
organic sulfur as well.
The major chemical coal cleaning processes exhibit a great
deal of diversity with respect to such variables as kinds and
amounts of sulfur removed, type of coal successfully desulfurized,
degree of coal crushing and grinding prior to chemical processing,
state of process development, process chemistry, major process
steps, and prospects for technical and economic success.
The various processes are summarized in the following tables.
Table 5 gives details of the 11 major processes with respect to
some of the above variables. Table 6 lists process costs and
performance, and Table 7 itemizes costs for each process. The
chemical coal cleaning processes are summarized in Table 8.
Versar also includes an extensive discussion of current
process technology for fine coal dewatering and drying. Fine
coal is produced in the various mining operations and is also a
major by-product of physical coal cleaning, which is accomplished
almost exclusively by wet processes. It has been estimated that
for each percent of water in coal, approximately 29 kJ/kg
(25,000 Btu/ton) is required to evaporate that moisture.
33
-------
TABLE 5. SUMMARY OF COAL CLEANING PROCESSES
Process
and
sponsor
"Magnex"
Hazen Research,
Inc. , Golden,
Colorado
"Syracuse"
Syracuse Re-
search Corp. ,
Syracuse, N.Y.
"Meyers" TRW,
Inc. , Redondo
Beach, Calif.
"LOL" Kennecott
Copper Co. ,
Ledgemont, Ma.
"ERDA" (PERC),
Bruceton, Pa.
Method
Dry pulverized coal
treated with Fe(C05)
causes pyrite to
become magnetic. It
is then removed
magnetical ly
Coal is comminuted by
exposure to NH.,vapor;
conventional physical
cleaning separates
coal/ash
Oxidative leaching
using Fe~(SO.),
oxygen in water
Oxidative leaching
using 0~ and water
at moderate temp, and
pressure
Air oxidation and water
leaching at high temper-
ature and pressure
Type sulfur
removed
Up to 90?,'.
pyritic
50-70"4
pyritic
90-95%
pyritic
90-95":;
pyritic
95?' pyritic;
up to 40 %
organic
Stage of
development
Bench and 91 kg/day
(200 Ib/day) pilot
plant operated
Bench scale
G Mg (9 ton) /day
for reaction sys-
tem; lab or bench
scale for other
process steps
Bench scale
Bench scale 11 kg
day (25 Ib/day)
continuous unit
under construction
Problems
Disposal of S-containing
residues; continuous re-
cycle of CO to produce
Fe(COr) requires demon-
stration
Disposal of sulfur-contain-
ing residues
Disposal of acidic FeSO. &
CaSO. in extraction step
requires demonstration
Disposal of gypsum sludge;
acid corrosion of reactors
Gypsum sludge disposal; acid
corrosion at high tempera-
tures
Annual
operating
costs, $/Mg
clean coal
(S/ton)a
44.8
(40.7)
43.4
(39.5)
47.9
(43.4)
50.9
(45.3)
56.9
(51.6)
U)
flValue shown includes cost of raw coal at $27.5/Mg ($25/ton)
(continued)
-------
TABLE 5. (continued)
Process
and
sponsor
"GE" General
Electric Co. ,
"Battell e"
Battell e-
Columbus, Ohio
"JPL" Jet
Propulsion
Laboratory,
Pasadena, Calif.
"IGT" Institute
of Gas Technol-
ogy, Chicago,
"KVB" KVB, Inc.
Justin, Calif.
"ARCO" Atlantic
Richfield Co.,
Harvey, 111.
Method
Microwave treatment of
coal permeated with NaOH
solution converts sulfur
forms into soluble sul-
fides
Mixed alkali leaching
Chlorinolysis in organic
solvent
Oxidative pretreatment
followed by hydrodesul-
furization at 800"C
Sulfur oxidezed in
NCL-containing atmoshere;
suffates washed out
Not given
Type sulfur
removed
75% total S
95% pyritic;
25-50% organ-
ic
907. pyritic;
up to 70%
organic
95% pyritic;
up to 85%
organic
95% pyritic;
un to 407
organic
95% pyritic;
Some organic
Stage of
development
Bench scale
9 kg/hr (20 Ib/hr)
pilot plant and
bench scale
Lab scale, pro-
ceeding to bench
and mini pilot
plant
Lab and bench
Laboratory
Continuous 0.45
kg/hr (1 Ib/hr)
bench-scale unit
Problems
Process conditions not estab-
lished; caustic regeneration
process not established
closed loop regeneration pro-
cess unproven; residual
sodium in coal
Environmental problems; con-
version of HC1 to Cl~ not
established
Low Btu yield (55%);
change of coal matrix
Disposal of waste and possibly
heavy metals; possible explo-
sion hazard via dry oxidation
Unknown
Annual
operating
costs, $/Mg
clean coal
($ton)a
44.3
(40.2)
62.0
(56.1)
50.3
(45.9)
72.4
(65.7)
53.8
(4S.8)
51-64
(46-58)
e^ M ma ted
U)
Ul
-------
TABLE 6. PROCESS PERFORMANCE AND COSTS OF
MAJOR COAL CLEANING PROCESSES
Net coal yield, Tg/day
( ton/day )b
Sulfur, %
Heating value, MJ/kg
(Btu/lb)
Emission rate yg SO«/J
(Ib S02/106 Btu) *
Btu recovery, %
Costs
Capital, million $
Annual , million $
$/Mg of clean coal
(I/annual ton)c
S/GJC ,
(S/10b Btu)C
Processes that remove pyritic sulfur only
Feed9
7110
(7840)
1.93
28.5
(12300)
1.33
(3.1)
TRW
6400
(7056)
0.83
29.7
(12835)
0.56
(1.3)
94
109
37.2
47.9
(43.4)
0.72
(1.69)
LOL
6400
(7056)
0.83
29.7
(12835)
0.56
(1.3)
94
114.1
45.3
50.6
(46.9)
0.78
(1.82)
Magnex
5645
(6225)
0.97
28.9
(12400)
0.69
(1.6)
80
37.8
19.2
44.8
(40.7)
0.70
(1.64)
Syracuse + PCC
6915
(6271)
1.50
33.9
(14600)
0.90
(2.1)
95
50.4
17.6
43.4
(39.5)
0.58
(1.35)
Pittsburgh seam coal from Pennsylvania, which contains 1.22 weight percent
pyritic sulfur, 0.01 weight percent sulfate, and 0.70 weight percent organic
sulfur. Heating value of 28 MJ/kg (12,300 Btu/lb) is assumed.
All values reported on moisture-free basis.
Includes coal costs at $27.6/Mg ($25/ton).
-------
TABLE 6. (continued)
Net coal yield, Tg/day
(tons/day)0
Sulfur, %
Heating value, MJ/kg
(Btu/lb)
Emission- rate, yg S09/J
(Ib S02/106 Btu) i
Btu recovery, %
Costs
Capital, million $
Annual , million $
$/Mg of clean coal
(I/annual ton)
$/GJc ,
($/105 Btu)C
Processes that remove pyritic and organic sulfur
ERDA
6400
(7056)
0.65
29.7
(12835)
0.4
(0.9)
94
166.8
56.6
56.9
(51.6)
0.86
(2.00)
GE
6826
(7526)
0.5
28.5
(12300)
0.35
(0.8)
96
102.0
35.9
44.3
(40.2)
0.70
(1.63)
Battell e
6755
(7448)
0.65
26.4
(11350)
0.52
(1.2)
88
168.1
74.8
62.0
(56.1)
1.06
(2.46)
JPL
6470
(7155)
0.6
28.5
12300)
0.4
(1.0)
91
103.0
44.3
50.3
(45.9)
0.80
(1.87)
IGT
4270
(4704)
0.55
27.2
(11685)
0.39
(0.9)
57
134.6
38.1
72.4
(65.7)
1.21
(2.81)
KVB
6070
(6690)
0.61
30.6
(13120)
0.39
(0.9)
91
67
44.0
53.8
(48.8)
0.80
(1.86)
ARCO
6400
(7056)
0.69
28.9
(12400)
0.47
(1.1)
91
58.7
-------
TABLE 7. OPERATING COSTS OF MAJOR CHEMICAL
COAL CLEANING PROCESSES
u>
00
Labor and G&A
Amortization
Taxes and Insur-
ance
Maintenance and
supplies
Utilities
Chemicals
Waste disposal
Annual process-
ing cost
Raw coal
Total
GE
$1000
1830
11980
3790
5310
7170
5860
35900
66000
101900
$/Mg
clean
coal
0.8
5.3
1.65
2.33
3.13
2.56
15.7
28.9
44.7
Battell e
$1000
2100
19700
5000
17800
23100
7100
74800
66000
140800
$/Mg
clean
coal
0.93
8.72
2.21
7.88
10.2
3.14
33.1
29.3
62.3
JPL
$1000
3700
6900
1400
2300
1400
28600
44300
66000
110300
$/Mg
clean
coal
1.71
3.2
0.64
1.06
0.64
13.3
20.5
30.5
51.0
IGT
$1000
4925
15600
4050
6732
3300
3300
38107
66000
103707
$/Mg
clean
coal
3.45
11.1
2.86
4.7
2.31
2.2
26.73
46.5
73.0
KVB
$1000
1445
7870
2010
3350
17271
11909
131
43987
66000
109987
$/Mg
clean
coal
0.72
3.9
0.99
1.65
8.5
5.87
0.07
21.7
32.6
54.3
(continued)
-------
TABLE 7. (continued)
vo
Labor and G&A
Amortization
Taxes and insur-
ance
Maintenance
supplies
Utilities
Chemicals
Waste disposal
Annual process-
ing costs
Raw coal
Total
Meyers
$1000
3962
12820
3270
5460
5764
4692
1275
37243
66000
103243
$/Mg
clean
coal
1.84
5.98
1.53
2.54
2.7
2.2
0.6
17.4
30.9
48.3
Ledgemont
$1000
1600
13400
3400
7300
10600
8200
800
45300
66000
111399
$/Mg
clean
coal
0.74
6.3
1.6
3.41
4.95
3.83
0.37
21.18
30.9
52.05
Magnex
$1000
786
4444
1135
1891
1400
9144
498
19218
66000
85238
$/Mg
clean
coal
0.42
2.35
0.6
1.0
0.74
4.84
0.23
10.2
35.0
45.2
Syracuse
$1000
620
5919
2016
3780
1040
4220
--
17592
66000
83595
$/Mg
clean
coal
0.28
3.1
1.1
1.97
0.54
2.21
--
9.25
34.7
44.0
ERDA
$1000
3255
19600
5004
8340
13224
6932
240
56595
66000
122595
$/Mg
clean
coal
1.22
9.2
2.3
3.9
6.2
3.24
0.11
26.5
30.9
57.3
-------
TABLE 8. COST-EFFECTIVENESS AND OTHER CHARACTERISTICS OF
CHEMICAL COAL CLEANING PROCESSES
Process
Magnex
Syracuse and
physical
cleaning
TRW
LOL
ERDA
GE
Battelle
JPL
IGT
KVB
ARCO
Type of
sulfur
removed
pa
P
P
P
P0a
PO
PO
PO
PO
PO
PO
w
Sulfur0 in
product, %
0.97
1.50d
0.83
0.83
0.65
0.50
0.65
0.60
0.55
0.68
0.69
Sulfur
removed, %
0.96
0.43
1.10
1.10
1.28
1.43
1.28
1.33
1.38
1.25
1.24
Process Costs,
$/Mg
Including
cost of coal
44.8
43.4
47.9
50.6
56.9
44.3
62.0
50.3
72.4
53.8
f
Cost-
effectiveness,
$/3S S removed
46.6
100
43.5
46.0
44.5
31.0
48.4
37.8
52.5
43.0
f
Cost-
effectiveness
ranking
3
4
1
2
4
1
5
2
6
3
f
Meets
EPA
NSPS
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Probable
success, X.
based on
available
Information
85
70
90
50
70
60
35
55
20
ioe
f
Time to
commercial
availability,
years
2 - 3
2-3
3
4-5
5
5
4-5
5
5
5
f
P-pyr1t1c; PO-pyrltlc and organic.
Based on Plttsburgn seam coal from Pennsylvania which contains 1.22 weight percent pyrltlc, 0.01 percent sulfate, and
0.70 percent organic sulfur.
Time frame assumes continuing effort or renewed effort starting Immediately.
80 percent yeild of product assumed in cleaning plant.
Processes not currently active, partially accounting for low probability of success.
Insufficient data available to permit educated guess.
-------
Ancillary problems related to high moisture content are caking,
freezing, and increased transport costs. Moisture reduction,
however, also creates hazards, since dry fine coal requires
special handling techniques to prevent dust pollution and explo-
sions. Fortunately, technology is currently available for meeting
the problems associated with handling dry, fine coal.
Mechanical dewatering devices can be grouped into two
categories:
1. Those that do not produce a final product - hydrocyclones
and static thickeners.
2. Those that produce a final product - screens, centrifuges,
spiral classifiers and filters.
Coal dryers also are of two types:
1. Direct heat, in which the products of combustion make
direct contact with the coal.
2. Indirect heat, in which the products of combustion do
not make direct contact with the coal.
Table 9 summarizes the moisture ranges in product coal that
can be achieved by various moisture reduction systems, assuming a
coal top size of 10 mm (3/8 in).
TABLE 9. TYPICAL MOISTURE CONTENT OF PRODUCTS BY EQUIPMENT OR PROCESS
Type of equipment/process
Dewatering screens
Centrifuges
Filters
Hydraulic cyclones
Static thickeners
Thermal dryers
Oil agglomeration processes
Percent moisture in
discharge product
8 to 20
10 to 20
20 to 50
40 to 60
60 to 70
6 to 7.5
8 to 12
41
-------
The problems of fine coal processing, dewatering, drying,
and handling are not new, and established technology seems to be
capable of meeting the needs created by the increasing volume of
fine coal. The most important element to be determined is the
economics associated with dewatering the fines as necessary for
a high degree of sulfur removal.
Versar has also reported on coal slurry sampling and coal
preparation requirements for synthetic fuel conversion processes.
4.1.4 Homer City Coal Cleaning Plant
An advanced coal cleaning pilot plant is under construction
near the Romer City Generating Station Power Complex in Homer
City, Pennsylvania (Figure 4). The coal preparation facility is
jointly owned by Pennsylvania Electric Company (Penelec - a
subsidiary of General Public Utilities Corporation), and New York
State Electric & Gas Corp. The facility will process 4.7 Tg
(5.2 million ton) of run-of-mine (ROM) coal per year, with a
design capacity of 1.1 Gg/h (1200 ton/h). The plant has
four distinct process circuits: coarse coal, medium coal,
fine coal, and fine coal scavanging. Unique design features
of the Homer City plant include:
1. Selective crushing to maximize the amount of 6 mm by
0.149 mm (1/4 inch x 100 mesh) coal.
2. Use of small diameter (0.35 m) dense-medium cyclones to
process the 2 mm by 0.149 mm (9 x 100 mesh) size frac-
tions.
3. Computerized control of the magnetite slurry density.
The major purpose of the plant is to clean coal for compli-
ance with S02 emission standards. As is shown in Table 10, the
plant is expected to produce medium- and low-sulfur coals. The
medium-sulfur coal will be used in the two existing 600-MW
generating units to meet a Pennsylvania emission standard of
1.7 yg S02/J (4.0 Ib SO2/106 Btu) . The low-sulfur coal will be
used in a new 650-MW unit to meet Federal NSPS of 0.5 yg S02/J
(1.2 Ib S02/106 Btu).
42
-------
CONVERSION FACTORS
RAW COM
INPUT
REFUSE
1-1/4" x 28 mesh
U)
28 mesh x 0
COAL SLURRY TO
SULFUR REMOVAL
CIRCUIT
SULFUR REMOVAL CIRCUIT (12 1.8
s.g. H.M. 24" CYCLONES AND 13
SCREENS FOR ( 1-1/4 x 28 mesh)
CLEAN COAL OUTPUT
FROM SULFUR REMOVAL
CIRCUIT
COAL SLURRY TO
HYDROCYCLONES
HVDROCYCLONES
COAL SLURRY
OVERFLOW FROM
HYDROCYCLONES
COAL SLURRY
OVERFLOW FROM
HYDROCYCLONES
28 mesh = 0.595 mm
1-1/4 Inch = 31.75
STACK GASES AND
PARTICULATES
SCRUBBER EFFLUENT
STACK GASES
AND
PARTICULATES
2 THERMAL DRYERS AND
2 SCRUBBERS FOR POWER
UNITS #1 AND #2
CLEAN COAL FOR
POWER UNITS
#1 AND *2
Figure 4. Preliminary block flow diagram for Homer City Coal
Cleaning Plant in its interim configuration
-------
TABLE 10. HOMER CITY PLANT PRODUCT SPECIFICATIONS
Weight distribution, percent
Energy distribution, percent3
Energy content, MJ/kg (dry basis)
Energy content, Btu/lb (dry basis)
Ash content, percent
Sulfur content, percent
Emission factor, yg S02/J
Emission factor, Ib S02/10 Btu
Medium-sulfur
coal
56.2
61.6
29.2
12,549
17.75
2.24
1.53
3.57
Low-sulfur
coal
24.7
32.9
35.4
15,200
2.84
0.88
0.49
1.16
Refuse
19.1
5.5
7.8
3,367
69.69
6.15
15.7
36.54
Overall plant Btu recovery is 94.5 percent, including 1 percent
allowance for thermal drying loss.
44
-------
EPA, Penelec, DOE, and the Electric Power Research Institute
(EPRI) are providing cooperative support to a 3-year test project
at the Homer City complex with the following objectives:
1. To determine the variability of sulfur and other pollu-
tants in coal fed to the cleaning plant.
2. To determine the performance of equipment used for
separation of coal and pyrite.
3. To determine the capability of plant process controls
to maintain the coal product streams within specifica-
tions for sulfur, ash, and Btu content.
4. To characterize pollutant streams emitted from the
preparation and power plants.
5. To determine the need for development of improved
pollution control technology.
6. To evaluate the effects of using clean coal on the
performance of boilers and electrostatic precipitators
at the power plant.
7. To determine capital and operating costs of the prepara-
tion plants, i.e., the costs of using physical coal
cleaning to meet S02 emission standards.
The preparation plant is scheduled for construction in two
phases. The first phase, completed in October 1977, is capable
of cleaning coal to meet an emission standard of 1.8 yg S02/J
(4.0 Ib SO /106 Btu). It was shut down during the UMW strike and
remained closed to facilitate construction of the second phase of
the plant. The complete plant was scheduled to begin operations
in the fall of 1978.
Acceptance tests on the first-phase operation were completed
in 1977. Operation of the equipment and plant was near design
expectations. The average sulfur emission level of the clean
coal over the 3-day acceptance test period was 1.01 yg S02/J
(2.24 Ib SO-/106 Btu). The acceptance test results are summa-
rized in Table 11.
Tests are now being conducted to establish performance
characteristics of the electrostatic precipitator and boiler
while the power plant boilers are burning uncleaned coal.
Preparation plant performance tests and power plant operating
evaluations are scheduled to begin late 1978 or early 1979.
45
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TABLE 11. HOMER CITY PLANT, PHASE-ONE ACCEPTANCE TESTS RESULTS
(MOISTURE FREE BASIS)
Feed coal
Clean coal
Refuse
Ash, %
20.05
13.05
76.85
Total
sulfur, %
2.33
1.51
5.37
Heating value Emission level
kJ/
kg
14.2
15.7
3.1
Btu/
Ib
12,239
13,527
2,646
yg lb,S02/
S02/J 106Btu
1.64 3.82
0.96 2.24
17.55 40.81
Average Btu recovery: 97.80%
Average yield: 85.50%
Average sulfur removal: 41.36%
46
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4.1.5 Dense-Medium Cyclone Pilot Plant
Deep cleaning of medium-sulfur coal is one alternative
strategy for meeting the SO- NSPS. The Homer City preparation
plant is the first to employ this process. Washing the coal at a
density of 1.27 Mg/m produces a sharp, efficient separation of
large amounts of near-density material.
DOE is conducting a test program of a pilot-scale dense-
medium cyclone at Bruceton, Pennsylvania. This program is being
conducted in cooperation with EPA, EPRI, and the owners of the
Homer City plant.
The objectives of the test program are to determine and
optimize the performance of the dense-medium cyclones for fine
coal cleaning, and hence to evaluate the performance of the
dense-medium cyclones in the Homer City plant. The pilot plant
has been designed and constructed, and all necessary equipment
has been installed. Several shakedown tests were run in order to
check plant operation and to establish procedures for sample
collection, processing, and analysis. A 12-month test program is
planned to evaluate the effects of several variables on the
performance of the dense-medium cyclone. These variables include
medium-to-coal ratio, inlet pressure, orifice size, magnetite
grade and size distribution, medium additives, and viscosity.
4.1.6 Coal/Pyrite Flotation Circuit Demonstration
Froth flotation is used commercially to separate coal
and mineral matter. It is one of the most specific of the
separation processes, based on sensitive surface properties of
the individual minerals. Briefly, conditions are arranged so
that when a pulp is agitated and air bubbles are blown through
it, coal pyrite particles attach themselves to the bubbles, and
are floated out in a froth, which is skimmed off.
The surface property of interest is the surface energy, or
surface tension, manifest in what is more readily recognized as
wettability. Chemicals are added to the slurry of coal and
pyrite to facilitate the attachment of coal pyrite to the air
47
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bubbles. Collectors are added to physisorb or chemisorb onto the
coal pyrite surface and affect the wettability. Regulators or
conditioners are added to the slurry to maintain the pH within a
critical region. Activators and depressors are added to render a
surface more or less amenable to the action of a collector.
Frothers are added to insure the formation of a stable froth with
sufficient buoyancy to carry the load of floatable coal pyrite
out of the slurry.
Unfortunately, the surface properties of some coal and
pyrite particles are not sufficiently dissimilar to permit
efficient separation. In some cases, multiple stages of flotation
and proper combinations of reagents result in a separation ' .
In other cases, the coal does not appear to be amenable to
coal/pyrite separation by flotation. However, the DOE is develop-
ing a flotation process especially for coal/pyrite separation.
The process consists of a first stage flotation step to remove
coarse, free pyrite and other refuse and a second stage in which
clean coal froth concentrate is repulped and treated with a coal
depressant, a pyrite collector, and a frother to selectively
float the remaining pyrite. Under a cooperative agreement
between Barnes and Tucker Company and the DOE, a two-stage
coal/pyrite flotation circuit has been installed in the Lancashire
No. 25 preparation plant. It was completed in September 1977 and
a 1-year test program was started at the termination of the UMW
strike.
4.1.7 Adsorption/Desorption Reactions in the Desulfurization
of Coal by a Pyrite Flotation Technique
A study of adsorption/desorption reactions occurring in the
desulfurization of coal by the DOE two-stage flotation process
(see section 4.1.6) has been completed by the University of
Utah . This research has provided information concerning the
process of adsorption on coal of various organic depressants. It
has been shown that this adsorption is physical rather than
chemical and that the depressant cannot be removed by repeated
washing.
48
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Laboratory flotation tests demonstrated that the first-stage
coal flotation response is sensitive to the residual concentration
of the second-stage coal depressant (Aero Depressant 633) in the
recycled water. It was shown, however, that repeated contact
with fresh coal removes much of the residual depressant from the
water; this suggests that the contact of recirculated water with
fresh coal and refuse in a preparation plant might remove most of
the residual depressant.
Study of the second stage of the process showed that the
second-stage pyrite collector (potassium amyl xanthate) chemisorbs
onto the surface of the pyrite, and that the reaction effectively
goes to completion. In addition, it was demonstrated that the
coal/pyrite flotation response with amyl xanthate differs signifi-
cantly from that of ore pyrite. Consumption of the pyrite collec-
tor is about an order of magnitude greater by coal pyrite than by
ore pyrite. The reason for the high amyl xanthate requirement
for coal pyrite flotation appears to be related to surface hetero-
geneities in the marcasite component of the coal pyrite, particu-
larly clay inclusions, which contribute significantly to its
hydrophilic character.
4.1.8 High-Gradient Magnetic Separation of Coal and Pyrite
High-gradient magnetic separation (HGMS) is a practical, new
technique for separating small, weakly magnetic particles on a
large scale. This technology, used commercially in the purifi-
cation of kaolin clay, was investigated by General Electric
Company with the objective of establishing the technical feasibil-
ity of removing a substantial fraction of the inorganic sulfur
from dry coal powders at significant processing rates.
In work performed under the initial contract, only marginal
desulfurization in air streams was observed. Because of the poor
performance of the dry separator system, a 2-month funded exten-
sion was granted to obtain supplemental data that would indicate
why the earlier results were unsatisfactory and how they might be
improved.
49
-------
The earlier tests were performed by injecting pulverized
coal into a relatively high-velocity air stream, which then
passed through a high-gradient magnetic separator. The resulting
poor separations were thought to be due to agglomeration of coal
and mineral particles. The researchers observed that the separa-
tion was marginally better when the fines were removed and
hypothesized that the fines promoted agglomeration. It was also
suspected that there might be significant turbulent flow in the
neighborhood of individual matrix fibers which could result in
large viscous forces on the particles and would make the retention
of trapped particles on the matrix very difficult. Electrostatic
forces did not appear to be significant factors.
In dry separation tests carried out in the supplementary
program, the use of an air stream to propel the coal through the
matrix was abandoned. Instead, the coal was moved by gravity
feed assisted by a combination of mechanical and electromagnetic
vibration. The coal used in most of the tests was taken from the
same batch (0.25 mm [60 mesh] top size, Upper Freeport) used in
the earlier series of tests; some freshly mined coal was also
tested for comparison. In addition to the dry tests, some wet
separations were performed. The tests were conducted with rela-
tively small feed samples (approximately 20 grams in the dry
tests and 80 grams in the wet tests). In addition to using
0.25 mm by 0 feed, some of the material was separated into plus
and minus 0.07 mm (200 mesh) size fractions and tested separately.
The results of these tests on dry coal led to the following
conclusions:
1. Dry magnetic separation by HGMS is feasible if the coal
fines are first removed and if a suitable technique is
used for gravity feed.
2. Multiple passes may be desirable to increase coal
recovery (only single passes were taken in this work).
3. Pyrite removal by HGMS from oxidized and from freshly
mined coals is substantially the same.
50
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4.1.9 Surface Phenomena in the Dewatering of Coal
Fine coal handled or cleaned in slurry form is dewatered to
render it suitable for conveying and blending, to reduce the cost
of transporting it, and to increase its effective calorific
value. The removal of water from coal finer than 0.6 mm (28 mesh)
is difficult and expensive. Vacuum filters are relatively
economical and practical for dewatering coal in the minus 0.6 mm
(28 mesh) size range, but the product usually contains over 20
percent moisture. As a result, thermal drying is often required
to reduce the moisture content of the filter cake to acceptable
levels. Thermal dryers, however, are costly to install and
operate, are hazardous, and are a source of air pollution.
The purpose of this investigation, which is being carried out
under a DOE contract with Syracuse University, is to study the
dewatering of coal and to expand the knowledge of water-coal
separation. Through a clear understanding of the effects of the
molecular and ionic nature of various surfactants on the coal-
water interface and on the air-water interface, one should expect
to be able to improve dewatering process.
The activity of surfactants in effecting moisture reduction
in coal dewatering is usually characterized by the surface
tension of the water. This investigation indicates, however,
that the reduction in filter cake moisture content with addition
of surfactant to the coal slurry may be due not only to a change
in surface tension at the air-water interface but also to changes
in surface energies at the solid-liquid and solid-air interfaces.
Therefore, surface tension is not a unique criterion for predict-
ing the dewatering behavior of surfactant solutions. Test data
show, for example, that it takes the adsorption of six layers of
a nonionic surfactant at a surface tension of 3.09 x 10 N/m to
slightly surpass the final water content of coal achieved with
the adsorption of a monolayer of an anionic surfactant at a
surface tension of 4.07 x 10~2 N/m. The data further show that
the successful use of surfactants to promote dewatering in coal
51
-------
preparation plants will depend on control of the surfactant
concentration in the slurry. If micelles form on the coal
surface because of a large concentration of surfactant in the
slurry and if their structure incorporates large quantities of
water, then an increase in water retention would result.
4.1.10 Reactor Test Project for Chemical Removal of Pyritic
Sulfur from Coal
In previous years EPA supported bench- and laboratory-scale
development work on coal desulfurization by aqueous ferric salt
leaching<16'17>. This process, the Meyers Process, which has
been developed by TRW, has now advanced to the pilot plant
stage.
The process chemically removes essentially all of the
pyritic sulfur from coal through a mild, oxidative treatment.
Important pollutant trace elements such as lead, cadmium, and
arsenic are removed at the same time. The process is particu-
larly cost-effective for providing compliance coal for industrial
boilers and smaller electric utilities, and for recovering and
desulfurizing coal fines rejected from mining and washing opera-
tions .
The Meyers chemical coal cleaning process is shown schemati-
cally in Figure 5. Coal is mixed with an aqueous solution of
ferric sulfate (Step 1), previously extracted from coal, to form
a slurry. The slurry's temperature is then raised to 100° to
130°C (Step 2), and the ferric sulfate oxidizes the pyritic
sulfur in the coal to form elemental sulfur and a mixed iron
sulfate. At the same time oxygen or air is introduced to regener-
ate the reacted ferric sulfate. Ferric sulfate dissolves into
the leach solution, while the elemental sulfur is removed in a
solvent extraction step (Step 3). The coal is dried, and the
solvent is recovered (Step 4). The products of the process are
elemental sulfur and iron sulfate, which may be limed to give a
dry gypsum and iron oxide material. Trace elements from the coal
are rejected from the leach solution with the stabilized gypsum-
52
-------
'r 4
01
U)
COAL_
(FeS2)
CaO
Fe(S04>3
REACTOR
(2)
/
SOL V EN
FILTER
i
T
DRYER
•COAL
SOLVENT
SULFUR
REACTOR CONDITIONS
TEMPERATURE: 110° - 132°C (230° - 270°F)
o
PRESSURE: 260 - 550 kN/m gauge (30 - 80 pisg)
RESIDENCE TIME: 5-8 hours
PARTICLE SIZE: 1.19 mm (14 mesh)
Figure 5. Meyers Process flow sheet,
-------
iron oxide solid. Elemental sulfur is the most desirable product
obtainable in processes controlling SO- pollution, since it may
be marketed or easily stored. The solid gypsum byproduct is
reported safe and storable.
Construction of a pilot-scale reactor test unit (RTU) with a
capacity of 0.3 Mg/h (1/3 ton/h) has been completed at Capistrano,
California (Figure 6). The RTU incorporates equipment with which
to evaluate the key process steps of coal-leach solution slurry
formation, coal leaching, leachant regeneration, and coal leachant
filtration (separation). Checkout and shakedown of the RTU was
completed at the end of September 1977. Initial performance
tests were made on Appalachian Coal donated by American Electric
Power from its Martinka mine. Operation of the plant through
January 1978 demonstrated that the RTU could be run continuously
in three-shift operations. More than 254 hours of RTU test
operation have been completed and 22.5 Mg (49,700 Ib) of coal
have been processed. The input coal containing 1 percent inorganic
sulfur was continuously and reliably reduced to a pyritic sulfur
(18)
level of 0.16 percent . Although there was no measurable coal
loss, calculations indicate an overall process efficiency of
93 to 96 percent, including process heat and electrical energy
requirements. The average heating value of the processed coal
was increased by 814 kJAg (350 Btu/lb) .
The test unit was shut down in February 1978 because of
corrosion in the primary reactor. Extensive evaluations using
erosion-corrosion coupons indicated that fiber-reinforced plastics,
elastomers, and 316L stainless steel are suitable for leach
solution/coal service at temperatures up to 90° C, but that 316L
stainless steel is not suitable for the more severe conditions
encountered in the reactor. Titanium, Hastelloy, or rubber-lined
brick over mild steel are required for the reactor-regenerator
I TO \
service at temperatures up to 130°CV. Replacement of the
reactor vessel and resumption of testing are dependent upon a
possible transfer of project management to DOE. Meanwhile,
bench-scale tests are continuing in order to evaluate a process
modification called Gravichem.
54
-------
Figure 6. Reactor test unit - Meyers Process
Capistrano, California.
55
-------
Bench-scale experimentation showed that the iron sulfate-
sulfuric acid leach solution can be used as a homogeneous dense
medium to efficiently gravity-separate fine coal at specific
gravities of 1.2 to 1.35. A significant portion of the input
coal, which floats in the leach solution, is almost pyrite-free
and may bypass the reactor, elemental sulfur extraction, and
dryer portions of the Meyers Process, thereby reducing process
costs. A flow diagram of the Gravichem process is shown in
Figure 7. When the process was applied at bench-scale to a TVA
(Interior Basin) coal containing 12 percent ash and 3 yg SO2/J
(7 Ib SO.,/10 Btu) , two products were obtained: a 4 percent ash
6
float coal containing 1.3 ug SO2/J (3 Ib SO2/10 Btu), and an
11-12 percent ash sink coal containing 2 ug SO2/J
(4 Ib SO2/106 Btu) after treatment by the Meyers Process. Both
of these products met state S02 emission standards for the coal.
4.1.11 Microwave Desulfurization of Coal
Laboratory experiments by General Electric have demonstrated
the technical feasibility of coal desulfurization by microwave
energy . Microwave irradiation of an aqueous slurry of coal
and NaOH appears to convert both pyritic and organic sulfur into
water-soluble sulfides (Na2S, Na2Sx).
The basic steps of the desulfurization process are:
1. Pulverize coal to 0.6 to 0.15 mm (28 to 100 mesh).
2. Mix with solution to produce a thick slurry.
3. Partially dry the slurry.
4. Subject to microwave irradiation for periods of 30 to
60 seconds at 1 atmosphere pressure (nitrogen atmosphere).
5. Wash coal and dry for use.
6. Convert sulfides to elemental sulfur and recover.
The last step, sulfide conversion, may involve the use of
carbon dioxide either generated by a limestone calciner or directly
from the stack gases. The carbon dioxide converts the sulfides
to sodium carbonate and hydrogen sulfide. The carbonate is then
treated with lime to regenerate the sodium hydroxide, although
this step has not yet been demonstrated practically.
56
-------
L
Fe2(S04)3
GRAVITY
SEPARATOR
\
(FeS)
Fe2(S04)3
REACTOR
MEYERS PROCESS
T
DESULFURIZED
Ik
CaS04 + Fe2°3
SULFUR
Figure 7. Gravichem Process flow sheet.
-------
Further review including an economic evaluation is given in
section 4.1.3. The process is shown schematically in Figure 8.
4.1.12 Battelle's Hydrothermal Process
Battelle's hydrothermal process (Figure 9) is capable of
removing 95 percent of the pyritic sulfur and up to 40 percent of
the organic sulfur. A large fraction of the process costs
results from operations that occur after the reaction step con-
verts the pyritic and organic sulfur to water-soluble sulfides.
These operations include separation of liquids and solids,
regeneration of spent leachant, and dewatering and drying of the
product coal. EPA has supported laboratory experiments to
evaluate methods for reducing the costs of these unit operations.
The results are detailed below.
Significant progress has been made in improving the liquid/
solid separation rate and in reducing the moisture content of the
coal product. By use of larger coal particles, i.e., 100 percent
minus 0.8 mm (20 mesh) and 100 percent minus 0.3 mm (50 mesh)
instead of 70 percent minus 0.07 mm (200 mesh), the filtration
2
rate has been increased from less than 0.3 Mg/h per m
2
(0.03 ton/h per ft ) with the fine coal to greater than
2 2
5.8 Mg/h per m (0.6 ton/h per ft ) after the fourth wash with
the coarser coals. For this phase of work vacuum filtration was
employed and liquid/solid separation was conducted at 70°C.
Normally, the vacuum filtration cakes contained about 50 percent
solids.
Additional dewatering has been achieved by centrifugation.
Using a 0.15 m (6 inch) screen bowl centrifuge, the solids
content of the 100 percent minus 0.8 mm (20 mesh) coal product
was increased to approximately 60 percent.
From the results of the liquid/solid separation study, a
near-optimum washing circuit was designed. It consists of (1) a
washing circuit of four rotary vacuum disc filter stages and five
vacuum belt filter stages to separate the spent leachant from the
desulfurized coal, and (2) a screen bowl centrifuge stage to
58
-------
BINDER
CLEAN COAL
RLCYCLED
NdOH
SOLUTION
BY-PRODUCT
ELEMENTAL
SULFUR
CAUSTIC
GENERATOR
MICROWAVE
GENERATOR
AND
IRRADIATION
CHAMBER
MICROWAVE
GENERATOR
AND
IRRADIATION
CHAMBER
CLAUS OR
STRETFORD
PROCESS
PLANT
.»_NaOH
SOLUTION
LIME (CaO) RECYCLE
STEAM
CONCENTRATED
NaOH SOLUTION
TO BLENDER
FILTER "U2
Figure 8. General Electric Microwave Process flow sheet.
-------
WKEUP WE*
Ci
-------
dewater the coal product. Countercurrent washing would be
employed, using a saturated lime solution in the last stage to
reduce the sodium to an acceptable level at a water-to-coal ratio
of 1.5 to 1.75. These process improvements reduce the cost of
chemical coal cleaning by alkali leaching.
In desulfurization of coal using alkali, the sulfur in the
coal reacts with the alkaline leachant to form sodium sulfide
(Na^S). The Na2S, being water-soluble, is separated from the
coal as discussed above. In commercial practice, the resulting
spent leachant would be recycled after removal of the sulfide
sulfur.
Among the materials that have been screened as potential
candidates for regeneration of the spent leachant for recycle
are: (a) zinc compounds such as zinc oxide and sodium zincate,
(b) iron compounds such as ferric and ferrous hydroxides, ferric
and ferrous carbonates, and (c) activated carbon.
The leading candidate at present is ferrous carbonate. At
an Fe/S ratio of about 3, approximately 88 percent of the total
sulfur is separated from spent leachant. Ferrous carbonate does
not contaminate the regenerated leachant with foreign anions or
cations and yields a regenerated leachant for recycle. Although
other compounds are also effective, the sulfide sulfur removal
efficiency depends on the method employed to produce the iron
compounds, and some of the compounds cannot be easily regenerated
for recycle.
4.1.13 Coal Cleaning Test Facility
The physical coal cleaning research of DOE is widely recog-
nized for its depth and general applicability to the needs of
industry; however, the program has been hampered by the lack of
an available integrated preparation pilot plant facility in the
United States. Such a facility is needed so that technology or
equipment developed by DOE can be demonstrated to industrial
representatives in a fully integrated coal preparation plant.
Unbiased engineering data then could be readily scaled up to
61
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operation of a full-size commercial coal preparation plant.
Moreover, the expense of evaluating processes that prove to be of
limited value to the industry would be greatly reduced.
Preliminary and detailed decisions have been completed for
a coal preparation process development facility. The test
facility will include a pilot plant, a supporting bench-scale
laboratory section, and a coal analysis laboratory.
An update of progress on the Coal Preparation Process
Development Facility (CPPDF) shows two major steps:
1. The conceptual and engineering designs have been comple-
ted by Birtley Engineering Corporation, Salt Lake City,
Utah. The company has submitted the following:
a. Complete detailed engineering drawings.
b. Specifications for construction of the coal process-
ing equipment.
c. An operating manual.
2. The architectural and engineering design has been
completed by Williams/Treibilcock/Whitehead, Pittsburgh,
Pennsylvania. The following items have been completed:
a. Master project schedule and definitive cost esti-
mates .
b. Specifications for site preparation bid package.
c. Foundation investigation.
d. Specifications for general, mechanical, electrical
work for site development and building construction,
A proposal has been completed for Construction Management
Services for the CPPDF and, if approved, should be let by
September 1, 1978.
4.1.14 Coal Preparation Plant Computer Model
The University of Pittsburgh has completed the first phase
in the development of a computer program that will simulate coal
preparation plant operations ' . The program can simulate
the following washing devices:
62
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Concentrating table
Dense-medium cyclone
Dense-medium vessel
Hydrocyclone
Baum jig
Froth flotation cell
The program also contains mathematical models for a rotary
breaker and for various crushers such as the single-roll crusher,
gyratory/jaw crusher, and cage mill crusher. Mathematical
models also exist for wet and dry screen performance.
From input in the form of coal analysis by size and specific
gravity fractions, the program will predict the output clean coal
and output refuse from a given plant configuration.
Work is needed in the following areas:
1. Improvement of the simulation algorithm for froth
flotation.
2. Simulation of ash and mineral liberation through crush-
ing.
3. Simulation of thermal dryers.
4. Addition of cost data to allow evaluations of the
economic feasibilities of various coal preparation
circuits.
4.1.15 Engineering/Economic Analysis of Coal Preparation, Opera-
tion, and Cost
The Hoffman-Muntner Corporation recently completed a study
to identify the costs associated with the various types and
levels of physical coal preparation processes currently avail-
able. Although data of this type have been generated previously
in fragmented form, the objective was to give a comprehensive
presentation having a uniform time base. A methodology was
developed that permits meaningful comparison of the relative
costs of coal cleaning. This technique was applied to current
technology and economics and also can be used in the future with
appropriate index adjustment.
63
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Eight existing coal preparation plants were selected for
analysis. These plants range in complexity from a relatively
simple jig plant to a rather sophisticated preparation scheme
incorporating dense-medium cyclones, froth flotation, and thermal
drying. The report discusses each of these plants separately,
with an analysis of the individual process and the level of
cleaning achieved, as supported by specific washability data.
Additionally, the major cost components, such as capital, labor,
and materials are summarized to arrive at the total cost of
cleaning for each plant. These analyses are presented from the
perspective of the preparation plant operator and do not assess
the many user-oriented benefits resulting from coal cleaning. In
addition to higher heat content, such benefits include lower
costs for emission control, transportation, boiler maintenance,
and ash disposal.
Table 12 summarizes the major performance and cost elements
from the eight operating preparation plants examined in this
study.
4.1.16 Chemical Coal Cleaning
A project entitled, "Analysis of Chemical Coal Cleaning
Processes", which Bechtel carried out for the Bureau of Mines is
presently being updated. The update is to include the Low
Temperature Chlorinolysis Process being investigated at JPL.
Cost analyses for the initial preparation and final compaction of
the coal are being modified to reflect process differences. In
addition, the KVB process flow chart will include process infor-
mation that was unavailable at the time of the initial report.
When these changes are completed, the report will be pub-
lished.
4.1.17 Hydrodesulfurization of Coal
The Institute of Gas Technology (IGT), sponsored by EPA, is
developing a chemical coal cleaning process based upon flash
/ 22}
hydrodesulfurization of coal . The coal is first pretreated
at a temperature of 400°C (and atmospheric pressure) to reduce
64
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TABLE 12. SUMMARY OF PREPARATION PLANT COSTS
CTl
Process
Jig-
simple
Jig-
intermediate
Jig-
intermediate
Jig-
complex
Dense medium-
simple
Dense medium-
complex
Dense medium-
compl ex
Dense medium-
complex
Capacity,
Mg/h
(ton/h)
input
544
(600)
907
(1000)
907
(1000)
1451
(1600)
1269
(1400)
544
(600)
544
(600)
810
(900)
output
321
(351)
647
(714)
513
(566)
864
(953)
939
(1036)
396
(440)
324
(360)
696
(774)
Capital
costs,$pcr
Mg/h
(ton/h)
7276
(6600)
15104
(13700)
13230
(12000)
15766
(14300)
15435
(14000)
24888
(22400)
15555
(14000)
25777
(23200)
Btu
recovery
91.6
96.4
83.0
93.7
94.6
89.2
93.1
94.3
Annual i zed costs
Dollars
per Mg
(per ton)
of
raw coal
2.17
(1.97)
2.91
2.62
2.45
(2.22)
2.86
(2.60)
3.08
(2.79)
3.93
(3.54)
2.32
(2.09)
3.23
(2.91)
Dollars
per Mg
(per ton)
of
clean coal
3.69
(3.35)
4.04
(3.67)
4.31
(3.92)
4.81
(4.36)
4.18
(3.76)
5.36
(4.83)
3.86
(3.48)
3.75
(3.38)
Dollars
per
per GJ
(million Btu)
0.138
(0.146)
0.152
(0.160)
0.157
(0.165)
0.162
(0.171)
0.185
(0.195)
0.177
(0.187)
0.137
(0.145)
0.135
(0.143)
-------
caking, and is then processed at 800°C (and atmospheric pres-
sure) . The process is dependent upon the proper conditions of
temperature, heat-up rate, residence time, coal size, hydrogen
partial pressure, and treatment-gas composition. The high tem-
peratures cause considerable loss of heating value due to oxida-
tion, hydrocarbon volatilization, and coal gasification. Average
product recovery is about 60 weight percent.
To date, experiments have been carried out only on bench and
laboratory scales in order to determine the correct operating
conditions. No adequate data exist on the heat and materials
balances needed to conceptualize the process design. The labo-
ratory program is currently testing a 10 inch fluidized bed unit
which can operate at coal feed rates between 10 and 45 kg/h.
The process can reduce organic sulfur by up to 88 percent
and inorganic sulfur by up to 100 percent, depending upon the
coal treated. The benefits of the system are that: (a) it
produces coal which is burnable in accordance with NSPS without
further treatment such as FGD; (b) it reduces the nitrogen
content of the coal by 50 percent, thus lowering NO emissions;
X
and (c) it could prove to be a major technology for treating coal
with a high organic sulfur content. The drawbacks of the process
are that: (a) the process has a comparatively low yield; (b) the
heating content of the coal is reduced by about 5 percent; (c)
the process changes the coal matrix and combustion modifications
may be required; (d) H~S and SO are produced as by-products and
£• ««*•
require further treatment; and (e) the process costs are high.
4.1.18 Environmental Studies on Coal Cleaning Processes
No reports describing the results of this project were
available for inclusion in this report.
4.2 ENVIRONMENTAL ASSESSMENT
The overall objectives of the environmental assessment
activities are to characterize coal contaminants and to identify
the fate of these contaminants during coal processing and use.
66
-------
Initial studies have focused on sulfur and potentially hazardous
accessory elements (minor and trace elements) contained in coal.
Recent studies have been concerned with a wider range of pollu-
tants - those that may be considered hazardous or toxic under the
Water Pollution Control Act (priority pollutants), the Resource
Conservation and Recovery Act (hazardous wastes), the 1977 Clean
Air Act Amendments (hazardous air pollutants), or the Toxic
Substance Control Act. The basic intent of the environmental
assessment activities is to identify pollutants that pose health
or ecological threats, and to devise cost-effective strategies
for dealing with the pollutants.
4.2.1 Environmental Assessment Project
A major 3-year project to assess the environmental impacts
of coal preparation, coal transportation, and coal storage is
being conducted for IERL-RTP by Battelle-Columbus. Some of the
major project activities are:
1. Development of a technology overview describing all
current coal cleaning processes and the associated
pollution control problems.
2. Development and operation of an environmental test
program.
3. Development of criteria for assessing the potential
health and ecological impacts from coal cleaning pro-
cesses .
4. Performance of studies to determine the relative environ-
mental impacts of coal cleaning, FGD, and other S02
emission control methods.
Physical coal cleaning plants have been surveyed, and the
data have been analyzed on a geographic basis. The plants have
been categorized by state (Table 13). New developments in the
fields of physical and chemical coal cleaning have been reviewed
and are discussed briefly.
Studies are in progress to develop criteria for assessing
the relative environmental hazards associated with pollutants
resulting from coal preparation, coal transportation, and coal
storage. The set of potential pollutants depends upon the
67
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TABLE 13. PHYSICAL COAL CLEANING PLANTS CATEGORIZED BY STATES
State
Alabama
Arkansas
Colorado
I) Knots
Indiana
Kansas
Kentucky
Maryland
Missouri
New Mexico
Ohio
Oklahoma
Pennsylvania
(anthracite)
Pennsylvania
(bituminous)
Tennessee
Utah
Virginia
Washington
West Virginia
Wyoming
Total
Total
(bituminous
excluding Pa.
anthracite)
Estimated total
coal production
Go
19432
608
7408
53741
22604
516
133238
2532
4566
8382
40436
2512
4617
74329
8430
5986
33106
3356
99770
21400
546969
542354
1000 t9l)f _
21425
670
8168
39251
24922
568
146900
2792
5035
9242
46582
2770
5090
81950
9295
6600
36500
3700
110000
23595
603055
597965
Number
of
coal
cleaning
plants
22
1
2
33
7
2
70
1
2
1
18
2
24
66
5
6
42
2
152
1
459
435
Number of
plants
reporting
capacity
_ data
10
0
0
20
6
2
48
0
1
1
13
1
14
50
4
4
29
1
113
1
318
304
Total dally
capacity of
reporting plants
. Ma
36824
_
_
124055
38094
3447
222850
.
3175
5442
43194
499
11791
258504
7728
2095
130200
18140
523679
544
1499117
1487326
tons
40600
.
—
136775
42000
3800
245700
_
3500
6000
102750
550
13000
285010
8520
23100
143550
20000
377375
600
1652830
1639830
Estimated
annual capacity
Gg
9206
.
„
31015
9524
862
55711
_
794
1361
23300
127
2948
64628
1932
5238
32552
4535
130921
137
374791
371834
tons"
10150
-
.
34195
10500
960
61425
_
875
1500
25690
140
3250
71255
2130
5775
32552
5000
144345
150
413210
409960
Dense
medium
washers
8
1
2
17
2
-
43
.
.
1
6
1
21
30
I
2
26
1
104
-
266
245
Number of plants using various
cleaning mehtods
Jigs
10
-
-
20
5
-
27
.
2
.
11
1
4
19
1
4
15
1
55
-
177
173
Flotation
units
6
-
1
4
1
-
16
1
.
1
.
.
4
16
1
2
9
-
59
-
121
117
Air
tables
1
-
.
1
-
-
4
-
.
.
1
.
.
20
2
2
8
-
12
1
52
52
Hashing
tables
12
.
.
1
1
-
20
-
.
-
-
-
3
15
-
-
15
-
55
-
125
122
CO
* The estimated annual-capacity values for the reporting plants were calculated from the daily-capacity values by assuming an average plant operation of
250 days per year (5 days per week for 50 weeks per year).
-------
boundaries selected. Initially the set was taken to include the
combusiton of coal in coal-fired power plants and burning coal
refuse piles. Under this interpretation, the myriad of organics
formed by the combustion of coal in oxygen deficient regimes
(coking-type reactions) was included as representative of gobpile
burning. These numbered in the hundreds; over 800 compounds have
already been identified from the coking of coal. Many different
pollutants have been identified as being associated with raw coal
or with some segment of the coal industry.
Reexamination of the problem led to the conclusion that the
boundaries of the set should be narrowed to eliminate all pollu-
tants except those directly concerned with coal cleaning. Burning
refuse piles at coal cleaning plants are to be considered a
mismanagement problem rather than a process problem. Thus, under
the redefinititon, the set of pollutants associated with the
cleaning of coal includes primarily inorganic compounds associated
with the ash fraction. Water would be the principal receptor for
these pollutants; operations causing major emissions of air
pollutants are infrequent in the cleaning of coal. The largest
air emissions would include fugitive dust from coal handling and
transfers, and particulates and combustion products from coal
dryers.
Within the set of possible pollutants, it was necessary to
establish certain criteria for defining actual pollutants; thus,
Priority I pollutants were defined as those that have already
been identified as pollutants of concern, and whose presence in
finite concentrations in coal cleaning processes is known or
suspected. These chemical substances were drawn from a number of
sources, including EPA criteria pollutants for air; pollutants
identified by effluent guidelines for coal mining and preparation;
substances included in EPA "Quality Criteria for Water"; and
toxic and hazardous pollutants listed by EPA. In addition to
these specific pollutants, a number of more general nonchemical
pollutants and aggregated pollutant parameters were included.
The total list (Table 14) details approximately 80 chemical
69
-------
TABLE 14. PROPOSED PRIORITY I POLLUTANTS
FOR COAL CLEANING PROCESSES
Pollutant
Al umi num
Antimony
Arsenic
Barium
Beryllium
Boron
Bromi ne
Cadmium
Calcium
Carbon
Cerium
Cesium
Chlorine
Chromi um
Cobalt
Copper
Fluorine
Gallium
Indium
Iodine
Iron
Pollutant regulations applicable to
coal cleaning
A
B
X
X
X
X
X
X
X
Xb
Xb
Xb
X
X
c
X
D
E
X
X
X
X
X
F
X
G
X
X
X
X
X
X
X
X
X
Column headings are defined as follows:
A - National Primary and Secondary Ambient Air Quality Stan-
dards
B - OSHA Standards for Workroom Air Contaminants
C - National Emission Standards for Hazardous Air Pollutants
D - New Source Performance Standards (Coal Preparation Plants)
E - Drinking Water Regulations (EPA and PHS)
F - EPA Toxic Pollutant Effluent Standards (Proposed)
G - EPA Water Quality Criteria (Proposed-not regulations)
Metal fume standard.
(continued)
70
-------
TABLE 14. (continued)
Pollutant
Lanthanum
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Niobium
Nitrogen
Oxygen
Phosphorus
Potassium
Rubidium
Selenium
Silicon
Sodium
Strontium
Sulfur
Tellurium
Thorium
Tin
Titanium
Uranium
Vanadium
Zinc
Zirconium
Groupings
Alkalinity
Ammonia
Cyanide
Pollutant regulations applicable to
coal cleaning
A
B
X
X
X
X
X
X
X
X
X
X
X
C
X
D
E
X
X
X
X
X
X
F
X
X
G
X
X
X
X
X
X
X
X
X
X
(continued)
71
-------
TABLE 14. (continued)
Pollutant
Chlorides
Nitrates
Sul fides
Sul fates
S0x
NO
X
Total suspended
solids (TSS)
Total dissolved
solids (TDS)
Chemical oxygen
demand (COD)
Total suspended
parti c. (TSP)
Carbon dioxide
Carbon monoxide
Hydrocarbons
Photochemical
oxidants
Oil and grease
Phenols
Organic sulfur
compounds
Organic nitrogen
compounds
Polycyclic organic
materials (POM's)
Carbon chloroform
extract (CCE)
Pollutant regulations applicable to
coal cleaning
A
X
X
X
X
X
X
B
X
X
X
X
X
C
D
X
X
E
X
X
X
X
X
F
G
X
X
X
72
-------
substances that have application to coal cleaning processes.
From this list a short list has been extracted to be used for
preliminary testing of some of the concepts and approaches to the
environmental assessment. The short list pollutants are:
arsenic mercury
beryllium nitrates
cadmium nitrogen oxides
iron selenium
lead sulfates
manganese sulfur dioxide
Pollutants from coal cleaning processes are released as
airborne gases and particulates, waterborne ions and compounds,
(including dissolved and suspended substances), and elements and
compounds associated with solid refuse piles. The ecological
impacts of these pollutants can be categorized as effects upon
human health, aquatic biota, terrestrial biota, and entire
ecosystems.
Many pollutants associated with coal cleaning and burning
are toxic to humans. Air pollutants probably pose the greatest
health hazard; in addition to their primary direct toxic effects,
they cause secondary effects by aggravating existing diseases.
The quantity of these emissions can be drastically reduced by
prevention of refuse pile fires. Of the water pollutants, heavy
metals are of great concern because these toxic trace elements
can be leached from coal refuse and storage piles.
Pollutants also have serious effects upon aquatic biota.
Heavy metals are often introduced into aquatic ecosystems as by-
products of acid mine drainage. Heavy metals are highly toxic to
aquatic organisms, especially fish. Some of the heavy metals and
related trace elements are also highly bioaccumulative. In
addition, they can inhibit photosynthesis, respiration, and
growth in various genera of freshwater algae. Freshwater inver-
tebrates are also deleteriously affected. Acidic water emanating
from mine drainage of coal piles can seriously alter the pH of
73
-------
the environment. Suspended solids can also be harmful, reducing
light penetration and providing a surface for growth of micro-
organisms.
These ecological effects can severely affect aquatic biota
by endangering the integrity of community structure. For example
the integrity of the community structure of algae and protozoa
could be seriously damaged by any reduction in the penetration of
visible radiation into the ecosystems that would restrict or
prohibit the growth of photosynthetic organisms. Predator-prey
relationships (e.g., zooplankton grazing on phytoplankton) might
change, resulting in abnormal increases or decreases of indivi-
duals, thereby causing an upset in the population balance and
stability.
Terrestrial biota can also be significantly affected.
Table 1-5 lists some symptoms shown by vegetation from the effects
of a variety of air pollutants. The contaminated vegetation may
then be ingested by terrestrial animals, who may also be contami-
nated by (a) inhalation of gases, aerosols, and particulates,
(b) ingestion of contaminated water or animals, or (c) absorption
of pollutants through the eyes or skin.
The effect upon the ecosystem of a change in the human,
aquatic, or terrestrial biota can be serious. A change in
vegetation can deprive a particular species of a habitat. The
balance of nature is disturbed.
Having defined the pollutants and their effects upon the
ecosystem, it is also important to establish permissible media
concentrations for each particular pollutant for pollution
control development guidance. In view of the state of the art,
which is still an emerging technology, the permissible media
concentrations are designated as estimated permissible concen-
trations (EPC's); they are regarded only as estimates, subject to
revision as more data become available.
Since a multimedia approach is being taken to the environ-
mental assessment of coal cleaning, EPC's are needed for all
three media - air, water, and land; and these will be integral
74
-------
TABLE 15. POLLUTANT EFFECTS ON VEGATATION
Pollutant
Sulfur dioxide
Ozone
Peroxyacetyl-
nitrate (PAN)
Nitrogen
Symptoms
Bleached spots,
bleached areas be-
tween veins, chloro-
sis, insect injury;
winter and drought
conditions may cause
similar markings
Fleck, stipple,
bleached spotting,
pigmentation; conifer
needle tips become
brown and necrotic
Glazing, silvering, or
bronzing on lower
surface of leaves
Irregular, white or
brown collapsed lesion
on intercostal tissue
and near leaf margin
Maturity of
leaf affected
Middle-aged
most sensitive;
oldest least
sensitive
Oldest most
sensitive;
youngest
least sensitive
Youngest most
sensitive
Middle-aged
most sensitve
Part of leaf
affected
Mesophyll cells
Palisade or spongy
parenchyma in
leaves with no
palisade
Spongy cells
Mesophyll cells
Injury theshold
ppm
(vol)
0.3
0.03
0.01
2.5
g/tr
785
59
50
4700
Sustained
exposure
5 hours
4 hours
6 hours
4 hours
U1
(continued)
-------
TABLE 15. (continued)
Pollutant
Hydrogen
fluoride
Ethyl ene
Chlorine
Symptoms
Tip and margin burn,
dwarfing, leaf abscis-
sion; narrow brown-red
band separates necrotic
from green tissue;
fungal disease, low
and high temperatures,
drought, and wind may
cause similar markings;
suture red spot on
peach fruit
Sepal withering, leaf
abnormalities; flower
dropping and failure
of leaf to open
properly; abscission;
water stress may
produce similar
marking
Bleaching between
veins, tip and
margin burn, leaf
abscission; marking
often similar to that
of ozone
Maturity of
leaf affected
Youngest
most sensitive
Young
recover; older
do not recover
fully
Mature
most sensitive
Part of leaf
affected
Epidermis and
mesophyll
cells
All
Epidermis and
mesophyll cells
Injury threshold
ppm
(vol)
0.1
(ppb)
0.05
0.10
g/m3
0.03
58
200
Sustained
exposure
5 weeks
6 hours
6 hours
(continued)
-------
TABLE 15. (continued)
Pollutant
Ammonia
Hydrogen
chloride
Mercury
Hydrogen
sulfide
2,4-Dichloro-
phenoxyacetic
acid (2-4D)
Sulfuric acid
Symptoms
"Cooked" green appear-
ance becoming brown
or green on drying;
over-all blackening
on some species
Acid- type necrotic
lesion; tipburn on fir
needles; leaf margin
necrosis on broad
leaves
Chlorosis and abscis-
sion; brown spotting
yellowing of veins
Basal and marginal
scorching
Scalloped margins,
swollen stems, yellow-
green mottling or
stippling, suture red
spot (2,4,5-T);
epi nasty
Necrotic spots on
upper surface similar
to those caused by
caustic acidic com-
pounds; high humidity
needed
Maturity of
leaf affected
Mature
most sensitive
Oldest
most sensitive
Oldest
most sensitive
Youngest
most affected
Youngest
most affected
All
Part of leaf
affected
Complete tissue
Epidermis and
mesophyll cells
Epidermis and
mesophyll cells
Epidermis
All
In.
ppm
^20
~5-10
< 1
20
<1
ury threshold
g/m3
^14,000
-11,200
<8,200
28,000
<9,050
Substained
exposure
4 hours
2 hours
1-2 hours
5 hours
2 hours
-------
parts of multimedia environmental goals (MEG's) that are to be
established. EPC's will be germane for air and water media,
which man and biota utilize directly. EPC's for soils will be
more difficult to establish, due to the fact that there must be a
least one transfer before a soil pollutant impacts man.
The establishment of EPC's is recognized as critical to the
entire environmental assessment, yet no accepted method has been
developed for their determination. Various methods have been
attempted, and Battelle has devised a novel series of biological
tests. However, there are still tremendous problems in the
determination of EPC's, the relevance of animal data to humans
being one of the most significant problems.
Concurrent with the development of source assessment criteria,
studies are in progress to select coal cleaning sites for environ-
mental testing. The classification of coal sites has been based
on four criteria: (a) the acid neutralization potential of the
soil surrounding the facility; (b) the pyritic sulfur content of
the run-of-mine coal; (c) the average annual precipitation; and
(d) the coal cleaning process technology. Based on combinations
of the extremes (high and low) for each variable and elimination
of combinations that do not occur, ten possible site categories
were obtained.
An initial sorting of more than 400 known coal cleaning
plants, using information available in the literature, produced
lists of facilities corresponding to each of the ten site categor-
ies . Where the categories included a large number of cleaning
plants, three secondary conditions were imposed to eliminate
plants considered undesirable because of field sampling problems.
This shortened list includes 46 facilities, to which site visits
are planned to obtain unpublished information that will be
required before the final selection of the sampling sites.
A master test plan is being developed to ensure a comprehen-
sive test program and to facilitate preparation of site-specific
field test plans. The master test plan will identify the poten-
tial pollution sources associated with a generalized coal
78
-------
cleaning plant and will suggest media likely to be impacted by
the effluents. Test objectives related to each pollution source
will be defined to simplify the process of selecting critical
sampling locations and measurements.
Between December 1976 and April 1977 a series of environ-
mental tests were conducted at the Homer City Generating Station
in Pennsylvania. The purpose of this monitoring was to evaluate
the air, water, and biological quality in the vicinity of the
advanced coal cleaning plant then under construction. These
studies were conducted prior to the operation of the cleaning
plant as a reference point for the future; more comprehensive
environmental testing is scheduled during the operation of the
plant. Results of the environmental tests are being evaluated.
As in other projects, an extensive review of pollution
control technology has been initiated, and is continuing.
4.2.2 Coal Contaminants
Three programs are directed to the identification and
characterization of contaminants in coal. Specifically, the
research attempts to demonstrate the occurrence, association, and
distribution of trace elements and mineral phases in the coal
seam.
One portion of this research, led by the Illinois State
Geological Survey, concentrates on coals of the Illinois Basin.
This work has three principal goals: (a) to determine the mode
of occurrence and distribution of trace elements and minerals in
coal seams; (b) to study the mineralogy and genesis of sulfide
minerals in coal; and (c) to evaluate the potential for removal
of minerals from coal by various preparation techniques.
The most significant contribution recently was the publica-
(1)
tion of "Trace Elements in Coal: Occurrence and Distribution"
which summarizes results of the past 6 years of EPA-supported
activity. The report demonstrates various levels of organic
affinities for some of the trace elements in coals. Germanium,
beryllium, boron, and antimony all have high affinities for
79
-------
organic matter, germanium having the highest. Zinc, cadmium,
manganese, arsenic, molybdenum, and iron tend to reside with the
inorganics, zinc and arsenic being most consistent. A number of
elements, including cobalt, nickel, copper, chromium, and selenium,
have intermediate organic affinities, suggesting that these
metals are present in coals as organometallic compounds, chelated
species, or adsorbed cations.
A second area of investigation is being studied by the U. S.
Geological Survey in Reston, Virginia. This project has dual
objectives. One is to determine the geologic factors which
affect or control the physical cleanability of coal and to
develop geologic models to help maximize the efficiency and
minimize the environmental impact from coal mining, cleaning, and
burning. The second objective is to provide chemical, physical,
and mineralogical data on the nation's coal resources that will
permit evaluation of the environmental impacts resulting from
coal preparation and utilization.
The annual report on the first objective of this study is
nearing completion; several preliminary conclusions can be drawn
on the Upper Freeport coal seam, which the report will address.
Despite the complexity of this seam, stratigraphic analysis
suggests that facies (geologic zones) in the coal can be mapped
throughout the study area. Therefore, those aspects of coal
quality that are a function of facies can also be mapped.
Mineralogic determinations suggest that quartz, pyrite, kaolin-
ite, illite, and calcite are the most abundant species and that
marcasite, siderite, sphalerite, and chalcopyrite occur occasion-
ally. Data on trace elements of environmental concern suggest
that arsenic is associated with the iron disulfides, cadmium
appears with zinc in sphalerite, and selenium is associated with
lead as a lead selenide.
The third study in the area of coal contaminants, being
conducted at the Los Alamos Scientific Laboratory (LASL), deals
with evaluation of the contaminant potential of coal preparation
wastes. The research has three distinct phases:
80
-------
(a) Characterize the minerals and trace elements, and their
association in coal preparation wastes; (b) to study the effects
of weathering and leaching on trace elements in coal wastes; and
(c) to identify and evaluate techniques for controlling or prevent-
ing trace element contamination from coal waste materials.
Phases (a) and (b) have been completed, and the results published
by EPA ' . Results of the LASL project are discussed in
section 4.3 of this report.
4.2.3 A Washability and Analytical Evaluation of Potential
Pollution from Trace Elements
The DOE has recently completed a study showing the trace
element content of various specific-gravity fractions of ten U.S.
(24)
coals . Most of the trace elements of interest were concen-
trated in the heavier fractions of the coal, indicating that they
are associated with mineral matter. Removal of the high-density
fractions of coal should result in trace element reductions,
ranging (for some elements) up to 88 percent.
4.2.4 Evaluation of the Effects of Coal Cleaning on Fugitive
Elements
Bituminous Coal Research, Inc., is evaluating the fate of
coal trace elements during mining, transportation, and prepara-
tion. It is proposed that 20 run-of-mine samples, representative
of U.S. coals, be collected and analyzed. To date, only two
samples have been collected. The first was a blend of Upper and
Lower Freeport bed coals from the Rochester and Pittsburgh Coal
Company in Indiana, Pennsylvania. The second was Illinois No. 6
bed coal from the Old Ben Coal Company in Benton, Illinois. Each
sample was crushed and sized, and each size fraction was subdivided
into three specific-gravity fractions. Each specific-gravity
fraction has been analyzed for arsenic, beryllium, cadmium,
chromium, copper, fluorine, lead, manganese, mercury, nickel,
selenium, vanadium, and zinc. Analyses are now being performed
to determine the relative organic and inorganic affinities of
each element.
81
-------
organic matter, germanium having the highest. Zinc, cadmium,
manganese, arsenic, molybdenum, and iron tend to reside with the
inorganics, zinc and arsenic being most consistent. A number of
elements, including cobalt, nickel, copper, chromium, and selenium,
have intermediate organic affinities, suggesting that these
metals are present in coals as organometallic compounds, chelated
species, or adsorbed cations.
A second area of investigation is being studied by the U. S.
Geological Survey in Reston, Virginia. This project has dual
objectives. One is to determine the geologic factors which
affect or control the physical cleanability of coal and to
develop geologic models to help maximize the efficiency and
minimize the environmental impact from coal mining, cleaning, and
burning. The second objective is to provide chemical, physical,
and mineralogical data on the nation's coal resources that will
permit evaluation of the environmental impacts resulting from
coal preparation and utilization.
The annual report on the first objective of this study is
nearing completion; several preliminary conclusions can be drawn
on the Upper Freeport coal seam, which the report will address.
Despite the complexity of this seam, stratigraphic analysis
suggests that facies (geologic zones) in the coal can be mapped
throughout the study area. Therefore, those aspects of coal
quality that are a function of facies can also be mapped.
Mineralogic determinations suggest that quartz, pyrite, kaolin-
ite, illite, and calcite are the most abundant species and that
marcasite, siderite, sphalerite, and chalcopyrite occur occasion-
ally. Data on trace elements of environmental concern suggest
that arsenic is associated with the iron disulfides, cadmium
appears with zinc in sphalerite, and selenium is associated with
lead as a lead selenide.
The third study in the area of coal contaminants, being
conducted at the Los Alamos Scientific Laboratory (LASL), deals
with evaluation of the contaminant potential of coal preparation
wastes. The research has three distinct phases: (a) to charac-
82
-------
terize the minerals and trace elements, and their association in
coal preparation wastes; (b) to study the effects of weathering
and leaching on trace elements in coal wastes; and (c) to identify
and evaluate techniques for controlling or preventing trace
element contamination from coal waste materials. Phases (a) and
(b) have been completed, and the results published by EPA '
A second annual progress report is in preparation. Results of
the LASL project are discussed in section 4.3 of this report.
4.2.3 A Washability and Analytical Evaluation of Potential
Pollution from Trace Elements
The DOE has recently completed a study showing the trace
element content of various specific-gravity fractions of ten U.S.
(24)
coals . Most of the trace elements of interest were concen-
trated in the heavier fractions of the coal, indicating that they
are associated with mineral matter. Removal of the high-density
fractions of coal should result in trace element reductions,
ranging (for some elements) up to 88 percent.
4.2.4 Evaluation of the Effects of Coal Cleaning on Fugitive
Elements
Bituminous Coal Research, Inc., is evaluating the fate of
coal trace elements during mining, transportation, and prepara-
tion. It is proposed that 20 run-of-mine samples, representative
of U.S. coals, be collected and analyzed. To date, only two
samples have been collected. The first was a blend of Upper and
Lower Freeport bed coals from the Rochester and Pittsburgh Coal
Company in Indiana, Pennsylvania. The second was Illinois No. 6
bed coal from the Old Ben Coal Company in Benton, Illinois. Each
sample was crushed and sized, and each size fraction was subdivided
into three specific-gravity fractions. Each specific-gravity
fraction has been analyzed for arsenic, beryllium, cadmium,
chromium, copper, fluorine, lead, manganese, mercury, nickel,
selenium, vanadium, and zinc. Analyses are now being performed
to determine the relative organic and inorganic affinities of
each element.
83
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4.3 DEVELOPMENT OF POLLUTION CONTROL TECHNOLOGY
The subprogram to develop coal cleaning pollution control
technology is in a formative phase. A wide variety of techniques
is available for controlling conventional pollution problems
(total suspended solids, total particulate emissions, pH, etc.),
but as coal cleaning processes evolve and as pollution control
regulations become more specific and stringent, these techniques
must be modified and improved. The subprogram for development of
pollution control technology addresses current and projected
pollution control needs.
4.3.1 Control of Trace Element Leaching from Coal Preparation
Plant Wastes
LASL is conducting studies to assess the potential for
environmental pollution from trace or minor elements that are
discharged or emitted from coal preparation wastes and stored
coals, and to identify suitable environmental control measures.
Initial studies were concerned with the assessment of the
identities, structure, and chemistry of the trace elements and
minerals in samples of high sulfur coal preparation wastes .
Extensive quantitative analyses were made of the elemental and
mineral compositions of more than 60 refuse samples collected
(24)
from three coal cleaning plants in the Illinois Basin .
Analysis showed these waste materials to be composed mainly of
clay minerals (illite, kaolinite, and mixed-layer varieties),
pyrite, marcasite, and quartz. Smaller amounts of calcite and
gypsum were also identified in some of the refuse samples. The
elements present in greatest abundance (silicon, aluminum, iron,
sodium, potassium, calcium, and magnesium) are components of the
major mineral species. Potentially toxic trace elements found in
environmentally significant quantities included manganese,
cobalt, nickel, copper, zinc, arsenic, selenium, cadmium, and
lead.
84
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The structural relationships and associations among the
trace elements and major minerals in the refuse samples were
investigated by statistical correlation of chemical and physical
data and by direct observation of refuse structure with electron
and ion microprobes. It was found that the mineral associations
of many of the trace elements that have been identified as being
highly leachable from the refuse samples, and therefore, of
environmental concern, were with the refuse clay fractions
rather than the major pyritic fractions.
In studies completed this year, static and dynamic tests
were conducted to determine the trace element leachabilities of
the various waste samples. Generally, the trace elements leached
in the highest quantities (iron, aluminum, calcium, magnesium,
and sodium) are constituents of the major refuse minerals.
Several other elements, although not present in the refuse in
large amounts, were nonetheless easily removed by leaching. This
group included cobalt, nickel, zinc, cadmium, and manganese.
The highest degree of trace element leachability was exhibi-
ted by the waste samples that produced the most acidic leachates.
Trace element leaching was also found to be a function of refuse
particle size (relative surface area), temperature, and access to
air.
On the basis of the mineralogy studies, elemental studies,
and laboratory leaching experiments, the elements of most concern
in the Illinois Basin preparation plant wastes are considered to
be fluorine, alumimum, manganese, iron, cobalt, nickel, copper,
zinc, and cadmium. These elements are often toxic in aqueous
systems or soils, or are present in the refuse in a highly leach-
able state.
Following completion of the leaching studies, experiments
were started to assess potential technologies for (a) preventing
the release (leaching) of trace elements from coal preparation
wastes, and (b) removing the dissolved trace elements from
acidic leachates.
85
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Tests were conducted to evaluate the degree of trace element
control that could be exerted by adding neutralizing agents to
high-sulfur refuse materials prior to disposal to reduce leachate
(24)
acidity and trace element dissolution . Column leaching
experiments were conducted with mixtures of crushed limestone and
refuse to test the effectiveness of this control method. Lime-
stone was combined with the refuse to simulate three geometric
arrangements in refuse dumps: placement of limestone on top of
the refuse, beneath the refuse, or intermixed with the refuse.
Adding coarse limestone to the acid refuse material was only
(24)
partly successful in controlling leachate acidity . The pH
values of the leachates from most of the refuse-limestone combina-
tions were higher throughout the leaching tests than were those
from the refuse alone; however, even in the best instances,
neutralization by the in situ limestone was not sufficient to
prevent the dissolution of refuse solids (see Figure 10). As
expected from the leaching studies, the release of some trace
elements was found to be dependent upon the degree of acidity
control. Release of elements, such as aluminum, potassium,
vanadium, and chromium (which were sensitive to leachate pH) , was
less from the refuse-limestone systems than from pure refuse.
The limestone additions had little apparent effect on the leachate
concentrations of iron, manganese, cobalt, copper, and zinc.
Other studies focused on potential control technologies to
reduce the content of undesirable trace elements in the aqueous
drainages associated with refuse disposal. Tests were conducted
to evaluate the degree to which trace element solubilities are
affected by treatment with neutralizing agents such as lime,
limestone, and lye (sodium hydroxide). These experiments indica-
ted that alkaline neutralization is an effective means for con-
trolling trace element concentrations in refuse wastewater. The
iron content and pH of the treated solutions were within accept-
able limits, based on 1977 EPA effluent limitation guidelines.
Manganese content, however, was a borderline case that sometimes
exceeded acceptable limits in the leachates. Lye was generally
86
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00
2 IOUH
o
co
UJ
O
CO
co
10'
2 x 10
-2
ID
LU
o:
oc
»—i
«=c
INTERMIXED
LAYERED
AT OUTLET
fcNO CONTROL
\ \
\
0 0.25
0.5 0.75
1.0 1.25 1.5 1.75
VOLUME, m3
2.0
Figure 10. Total dissolved solids vs leachate volume from column
leaching study of limestone refuse mixtures.
-------
more effective than limestone or lime in reducing the trace
element content of the drainage samples.
4.3.2 Control of Blackwater in Coal Preparation Plant Recycle
and Discharge
Characterization of the fine solid material in the primary
effluent from coal preparation plants provides the basis for a
better understanding of the problems associated with treating
blackwater. The study was made to obtain a comprehensive char-
acterization of the blackwater solids from coal preparation
plants. Suspended solids from 13 blackwater samples, representa-
tive of the major U.S. coal seams where wet preparation methods
are used, were characterized by mineralogical content, particle
size distribution, and surface properties.
The conclusions from this work are as follows:
A. Minerlogical composition
1. Blackwater solids consist of two types of material,
carbonaceous matter and mineral material. These
constituents exhibit distinctly different chemical and
physical properties.
2. Based on mineralogical similarities, the samples were
divided into two groups; those from the Eastern half of
the United States (Appalachian and Midwestern coal
fields), and those from the Western half. The minera-
logical content of the eleven Eastern samples was
similar, whereas the two Western samples differed from
the Eastern ones as well as from each other. The
Eastern samples show marked similarities since they are
all derived from coals of the Pennsylvanian period.
3. In all 11 Eastern blackwater samples tested, the carbon-
aceous content amounted to approximately 60 percent of
the total weight of the blackwater solids. These
studies showed that it is possible to remove, by froth
flotation, essentially all of this carbonaceous (coal)
fraction from the blackwater, and that this coal could
be blended with the coarse clean coal without signifi-
cantly altering the quality of the total product.
4. Additional clean coal may be recovered from current
blackwater discharges from preparation plants by a more
extensive use of the flotation process.
88
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5. The average ash content of the carbonaceous fraction
removed by froth flotation was 11 percent, as compared
to an average of 41 percent ash in the as-received
blackwater samples.
6. The mineral fraction of the blackwater solids from
Eastern and Midwestern coal fields contains largely
illitic clays together with lesser amounts of kaolinite,
quartz, calcite, chlorite, and pyrite. Minor amounts
of dolomite, feldspar, rutile, or siderite were found
in some of the samples.
7. The average mineralogical composition of the mineral
fraction from blackwater solids of the eleven samples
representative of the "Eastern" coal fields are summar-
ized in Table 16.
8. The high illitic clay content in the Eastern blackwater
samples indicates that a large amount of the mineral
material in the blackwater is of shale origin. Since
shale-derived material is usually soft, it tends to
decompose easily during processing. Its presence in
the blackwater effluent from a coal preparation plant
is therefore virtually assured.
9. Samples from West Virginia, Kentucky, and Alabama
contained an illitic material of relatively good crys-
tallinity with very little or no interstratification of
montmorillonite with the illite, whereas samples from
Pennsylvania, Ohio, Indiana, and Illinois contained an
illitic material of varying crystallinity and interstra-
tification.
10. Mineralogy of the two Western samples is different from
that o£ the Eastern samples. Both Western samples
contain a large amount of montmorillonite clay. The
unique mineral contents of these two samples may be
attributed to the fact that these coal seams belong to
two different geological periods - the Washington
sample from the Tertiary and the Colorado/Utah 'sample
from the Cretaceous.
11. Montmorillonite clay, such as that found in the Western
samples, is often more difficult to flocculate effi-
ciently than are illitic and kaolin clays; therefore
higher turbidity may be expected in the recycled water
from plants treating these Western coals.
12. The primary control of the composition of the mineral
matter contained in blackwater is the composition of
the adjacent strata, which becomes incorporated into
run-of-mine coal during mining.
89
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TABLE 16. PRINCIPAL MINERALS FROM BLACKWATER SOLIDS,
EASTERN COAL FIELDS3
Average
Range of
average
mite,
%
55
47-65
Kaolinite,
%
11
6-22
Chlorite,
%
4
0-7
Calcite,
%
12
0-22
Quartz,
%
15
8-22
Pyri te ,
%
4
1-10
aMineral composition of blackwater from plants treating coals dating
from the Pennsylvanian period may be expected to be similar to this.
90
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13. The differences in the carbonaceous contents of the
13 blackwater samples are more than likely due to
differences in the mining and preparation methods used
at the different mines rather than to a difference in
the type of coal being mined.
14. The average ash content of pure mineral matter of a
typical Eastern sample is about 87 percent. The remain-
ing 13 percent loss is due to the formation of H20,
CO0, SO9, etc., upon heating.
£ £
B. Particle Size Analysis
1. Carbonaceous (coal) and mineral fractions from the
different blackwater samples produce two distinct size
distributions. The carbonaceous fraction is consistently
coarser than the mineral matter fraction. On the
average, 41 percent of the carbonaceous particles are
less than 44 ym, whereas 83 percent of the mineral
matter particles are less than 44 ym.
2. Considerable similarity in particle size distribution
was found among the 11 Eastern samples. Size distribu-
tions in the two Western samples, however, were quite
different, probably because of differences in the
mineralogy and in the sampling procedures.
3. Typically, the size distributions in the mineral matter
tend to be bimodal, probably because of mixtures of
"coarse" minerals (quartz, calcite, pyrite, etc.), and
"fine" minerals (clays).
4. The size distributions of the mineral matter in the
Eastern samples were remarkably similar, presumably
because of the similarity of their mineral content.
Plots of the particle size distributions of the mineral
matter from all 11 Eastern samples yielded a narrow
band, with standard deviations ranging from ± 2.2 to
±9.7 percent, depending on size. A composite size
distribution shows that, on the average, 70 ± 9.7
percent of the mineral matter is finer than 10 ym. The
fineness of these materials is no doubt due to a high
clay content.
5. Similar composite size distributions of the carbonaceous
fractions produced standard deviations ranging from
± 0.8 to ± 15.9 percent. The average size distribution
of the carbonaceous fraction indicates that this material
is much coarser than the mineral matter fraction. The
carbonaceous material averages only 21.2 + 7.3 percent
finer than 10 ym.
91
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6. In most of the samples, the high clay content completely
dominated the size characteristics of the mineral
matter fraction and strongly influenced the overall
size characteristics of the blackwater solids.
C. Surface Properties
In the investigation of the surface properties of the princi-
pal mineral and carbonaceous constituents, the Zeta potential was
measured to determine the electrophoretic mobility of these
constituents as a function of pH.
1. Hydronium and hydroxyl ions are potential determining
ions for coal and silicate constituents of blackwater.
These two mineral categories (coal and silicates)
typically account for about 90 percent of the particu-
late matter in blackwater.
2. Pyrite and the carbonate minerals, mostly calcite, are
the only important constituents found in blackwater for
which hydronium and hydroxyl ions are not directly the
potential determining ions. These minerals are indirectly
affected by the concentration of these ions, however,
because of the effect of pH on their potential deter-
mining ions through the CO2/HCO.j ~/CO 2~ and H_S/HS~/S2~
equilibria and through precipitation of metal ions by
hydroxyl ions.
3. The point of zero charge (PZC) for the silicate minerals
is usually below a pH of 4.
4. The surface properties of the illitic group of clay
minerals were highly variable, a reflection of the high
degree of structural and compositional variation in
this class of clay minerals. For some illites the PZC
occurred at pH 2-3, and for others no PZC was found and
the particles maintained a negative potential over the
entire range studied, pH 2-10.
5. Manipulation of the pH of blackwater suspensions will
strongly influence the Zeta potential of the contained
mineral matter, and offers a means of controlling the
agglomeration of most of the mineral matter. Agglomera-
tion of the silicates, which constitute most of the
mineral matter in blackwater, should be favored as the
pH of the suspension is lowered. It is not to be
inferred that pH control would be the only means, or
even the preferred means, of achieving flocculation of
the particulate matter in blackwater. In practice, the
use of inorganic and organic flocculating agents, such
as lime, alum, starch, and polyacrylamides, would usually
be the preferred method of flocculation.
92
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6. Since most of the mineral matter in blackwater is
clays, the surface properties of these clay minerals
will exert a major influence on the surface properties
of the suspension as a whole. This effect is magnified
because of the small particle size and great surface
area of the clays.
7. The large carbonaceous (coal) content in most of the
blackwater samples suggests that the surface properties
of the coal will also be an important factor in deter-
mining the bulk properties of the suspension and the
blackwater treatment process.
8. The PZC of the fresh coal samples tested was between
pH 3 and 7, decreasing to pH 2 or below as the surface
of the coal becomes oxidized. The Zeta potential of
most coals is negative for alkaline solutions and
decreases in magnitude as the pH is lowered. The
surface properties of the carbonaceous constituents of
blackwater will depend on a number of factors such as
rank, lithotype, degree of oxidation, and chemistry of
the blackwater solution.
9. In actual practice one would expect surface properties
of the carbonaceous particles in blackwater to be much
closer to those of oxidized coal than to those of the
fresh coal.
D. Characterization of a Typical Eastern Blackwater Sample
The characteristics of an average Eastern blackwater sample
are shown in Table 17.
4.3.3 Stabilization of Coal Preparation Waste Slurries
Reject ponds are becoming increasingly impractical because
of safety, environmental, and land-use considerations. An
alternative approach to the disposal of the fine slurry wastes is
the treatment of these wastes to create stable solids, a process
termed "stabilization."
Under contract to DOE, Dravo Lime Co. is conducting a study
to characterize the engineering, physical, and chemical properties
that affect stabilization of fine wastes from coal preparation
plants. The requirements and conditions for stabilizing these
wastes with and without chemical agents are being determined.
Nine samples were collected from preparation plants in
Pennsylvania, West Virginia, Virginia, Illinois, and Indiana.
93
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TABLE 17. CHARACTERISTICS OF A TYPICAL EASTERN BLACKWATER SAMPLE
Solid material
Weight, percent
Ash, percent
Sulfur, percent
Mineral
40.6
84.3
1.97
Carbonaceous
59.4
10.9
1.51
Total
100.0
41.0
1.68
Mineral composition, weight percent
Illitic
55
Kaolinite
11
Quartz
15
Calcite Chlorite
12 4
Pyri te
4
Particle size analysis, weight percent-less than
Size (ym)
44
1
Mineral
86
22
Carbonaceous
44
3
Total
59
n
Surface properties of principal constituents (coal and silicates)
Potential Determining Ions
Point of Zero Charge
H+ OH"
Less than pH 5
94
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All samples were subjected to laboratory analyses for index
properties, which are permeability, consolidation, penetration,
and direct shear, and for stabilization characteristics as a
function of variations of additive type (Calcilox, lime, portland
cement), dosage, waste solids level, temperature, and time.
The data are being analyzed, and a final report is to be
issued in several months. If additional research is warranted,
a second phase involving on-site testing with a mobile laboratory
will be carried out.
95
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REFERENCES
1. GLUSKOTER, H. J., et al., "Trace Elements in Coal: Occur-
rence and Distribution," EPA-600/7-77-064 (NTIS No. PB 270
922/AS), June 1977.
2. MCCANDLESS, L. C., "An Evaluation of Chemical Coal Cleaning
Processes," Draft Technical Report, EPA Contract 68-02-2199,
January 1978.
3. WEWERKA, E. M., et al., "Environmental Contamination from
Trace Elements in Coal Preparation Wastes: A Literature
Review and Assessment," EPA-600/7-76-007 (NTIS No. PB 267
339/AS), August 1976.
4. KILGROE, J. D., "Coal Cleaning for Compliance with S02
Emission Regulations," Third Symposium on Coal Preparation,
NCA/BCR Coal Conference and Expo IV, October 18-20, 1977,
Louisville, KY.
5. MIN, S., WHEELOCK, T. D. , "Cleaning High Sulfur Coal,"
Second Symposium on Coal Preparation, NCA/BCR Coal Confer-
ence and Expo III, October 19-21, 1976.
6. CAVALLARO, J. A., JOHNSTON, M. T., DEURBROUCK, A. W. , "Sulfur
Reduction Potential of U. S. Coals: A Revised Report of
Investigation," EPA-600/2-76-091 (NTIS No. PB 252 965/AS)
or Bureau of Mines RI 8118, April 1976.
7. ANON., "Replacing Oil and Gas with Coal and Other Fuels in
the Industrial and Utility Sectors," Executive Office of
the President—Energy Policy and Planning, June 1977.
96
-------
8. MCGLAMERY, G. G., et al., "Flue Gas Desulfurization Eco-
nomics" in Proceedings, Symposium on Flue Gas Desulfurization,
New Orleans, March 1976, Volume I, EPA-600/2-76-136a (NTIS
No. PB 255 317/AS), May 1976.
9. LASEKE, B. A., Jr., "EPA Utility FGD Survey: December 1977 -
January 1978," EPA-600/7-78-051a (NTIS No. PB 279 011/AS),
March 1978.
10. TUTTLE, J., PATKAR. A., GREGORY, N., "EPA Industrial Boiler
FGD Survey: First Quarter 1978," EPA-600/7-78-052a (NTIS
No. PB 279 214/AS), March 1978.
11. HOFFMAN, L., ARESCO, S. J., HOLT, C. C., Jr., "Engineering/
Economic Analysis of Coal Preparation with SO2 Cleanup
Processes for Keeping High Sulfur Coals in the Energy
Market," The Hoffman-Muntner Corporation for U. S. Bureau
of Mines, Contract JO155171, November 1976.
12. GILCHRIST, J. D., "Extraction Metallurgy," Pergamon Press,
London, 1967, p. 66 ff.
13. MILLER, K. J. , "Flotation of Pyrite from Coal: Pilot Plant
Study," U. S. Bureau of Mines, RI 7822, Washington, D. C.,
1973.
14. MILLER, K. J., "Coal Pyrite Flotation in Concentrated
Pulps," U. S. Bureau of Mines, RI 8239, Washington, D. C.,
1977.
15. MILLER, J. D., "Adsorption-Desorption Reactions in the
Desulfurization of Coal by a Pyrite Flotation Technique,"
University of Utah for U. S. Bureau of Mines, Contract
H0155169, April 1978.
16. HAMMERSMA, J. W., KRAFT, M. L., "Applicability of the
Meyers Process for Chemical Desulfurization of Coal:
Survey of 35 Coals," EPA-650/2-74-025a (NTIS No. PB 254
461/AS), September 1975.
97
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17. KOUTSOUKOUS, E. P., et al., "Meyers Process Development for
Chemical Desulfurization of Coal, Volume I," EPA-600/2-76-
143a (NTIS No. PB 261 128/AS), May 1976.
18. HART, W. D., et al., "Reactor Test Project for Chemical
Removal of Pyritic Sulfur from Coal, Volume I," Draft Final
Report, EPA Contract 68-02-^1880, April 1978.
19. ZAVITSANOS, P. D., "Coal Desulfurization Using Microwave
Energy," EPA-600/7-78-089, Washington, D. C., June 1978.
20. GOTTFRIED, B. S., and JACOBSON, P. S., "Generalized
Distribution Curve for Characterizing the Performance of
Coal-Cleaning Equipment," USBM Report of Investigation 8238.
21. GOTTFRIED, B. S., "Computer Simulation of Coal Preparation
Plants," Final Report on USBM Grant No. G0155030.
22. CONTOS, G. Y., FRANKEL, I. F. , MCCANDLESS. L. C., "Assess-
ment of Coal Cleaning Technology: An Evaluation of Chemical
Coal Cleaning Process," EPA-600/7-78-173a, August 1978,
p. 165-183.
98
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BIBLIOGRAPHY
KILGROE, J. D., HUCKO, R. E., "Interagency Coal Cleaning
Technology Developments," Third National Conference on
Interagency Energy/Environment R & D Program, Washington,
D. C., 1978.
CONTOS, G. Y., FRANKEL, I. F., MCCANDLESS, L. C., "Assess-
ment of Coal Cleaning Technology: An Evaluation of Chem-
ical Coal Cleaning Processes," EPA-600/7-78-173a, August
1978.
99
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-072
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
EPA-Meragency Coal Cleaning Program: FY 1978
Progress Report
8. REPORT DATE
February 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
Robin D. Terns
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
PEDCo Environmental, Inc.
P.O. Box 20337
Dallas, Texas 75220
10. PROGRAM ELEMENT NO.
EHE623A
11. CONTRACT/GRANT NO.
68-02-2603, Task 31
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: 10/77 - 9/78
14. SPONSORING AGENCY CODE
EPA/600/13
16. SUPPLEMENTARY NOTES fERL-RTP project officer is James D. Kilgroe, MD-61, 919/541-
2851.
16. ABSTRACT
The report reviews the progress of EPA's interagency coal cleaning pro-
gram for 1977. Research into the methodology and economics of physical coal clea-
ning has continued. The first phase of a physical coal cleaning plant has undegone
acceptance tests. In conjunction with that project, investigations are being carried
out to optimize the performance of dense media cyclones. A two-stage coal/pyrite
floatation demonstration circuit has been installed in a coal preparation plant. In an
associated project, adsorption/desorption reactions in the desulfurization of coal by
flotation are being studied. High-gradient magnetic separation is being studied for
application to coal cleaning. The first phase has been completed in developing a
computer program to simulate coal preparation plant operations. A study to identify
the costs associated with various physical coal cleaning processes was recently
completed. Amajor review of the process technologies and economics of the most
advanced chemical coal cleaning processes has been completed. A 1/3-ton/hr Reac-
tor Test Unit has been operated for 4 months to evaluate key process steps of the
Meyers process. Improvements have been made to Battelie's hydrothermal process.
A extensive review of the environmental impact of coal cleaning has been started.
Programs are under way to characterize possible hazardous pollutants in wastes.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. cos AT i Field/Group
Pollution
Coal
Coal Preparation
Assessments
Pyrite
Flotation
Cyclone Separators
Sorption
Desulfurization
Magnetic SeparatorsjCoal
Mathematical Mo-
dels
Toxicity
Pollution Control
Stationary Sources
Cleaning
Environmental Assess-
ment
Hydrothermal Process
13B 07D
08G,21D
081
14B
12A
07A,13H,11F 06T
131
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
21. NO. OF PAGES
110
22. PRICE
EPA Form 2220-1 (»-73)
100
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