U.S. Environmental Protection Agency Industrial Environmental Researcn FPA ROO/7 Tfi
Office of Research and Development Laboratory
Research Triangle Park, North Carolina 27711 Q Ctobef 1976
CONTROL OF WASTE AND
WATER POLLUTION FROM
POWER PLANT FLUE GAS
CLEANING SYSTEMS:
First Annual R and D Report
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research.and Development, U.S.
Environmental Protection Agency, have been grouped into seven series.
These seven broad categories were established to facilitate further
development and application.of environmental technology. Elimination
of traditional grouping was consciously planned to foster technology .
transfer and a maximum interface in related fields. The seven 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
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 systems. The goal of the Program
is to assure the rapid development of domestic energy supplies in an
environmentally—compatible manner by providing the necessary
environmental data and control technology. Investigations include
analyses 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 environmental issues.
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 recommen-
dation for use.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161.
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EPA-600/7-76-018
October 1976
CONTROL OF WASTE AND WATER POLLUTION
FROM
POWER PLANT FLUE GAS C L E ANIN G S Y S T E MS :
FIRST ANNUAL R AND D REPORT
by
P. P. Leo and J. Rossoff
The Aerospace Corporation
Environment and Energy Conservation Division
El Segundo, California 90245
Grant No. 68-02-1010
Program Element No. EHE624A
EPA Project Officer: Julian W. Jones
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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ABSTRACT
This initial report summarizes and assesses the state of
research and development in the fields of nonregenerable flue gas cleaning
waste treatment, utilization and disposal, as well as water reuse technology
for coal-fired utility power plants. It is based upon information available
through December 1975.
Significant results cover the following areas: chemical an I
physical characterization of wastes from eastern and western plants using
lime, limestone, or double-alkali scrubbing systems; chemical and physical
properties and leaching characteristics of treated and untreated wastes;
field evaluations of treated and untreated waste disposal; disposal alterna-
tives; cost estimates for ponding and for fixation disposal methods; disposal
standards; gypsum production and marketing; potential use of wastes in
fertilizer production and portland cement manufacture; beneficiation studies;
and total power plant water reuse.
Future reports will be issued annually to evaluate the progress
of flue gas cleaning waste disposal and utilization technology. Results not
available, but to be included in subsequent reports, will cover the areas of
coal-pile drainage, ash characterization and disposal, soil attenuation ef-
fects, and conceptualized design cost analyses for various methods of flue gas
cleaning waste disposal.
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CONTENTS
ABSTRACT iii
ACKNOWLEDGMENTS xiii
CONVERSION TABLE xv
I. CONCLUSIONS 1
1.1. Background 1
1.2 Conclusions and Observations 2
II. RECOMMENDATIONS 5
2. 1 Background 5
2.2 Recommendations 5
III. INTRODUCTION 7
3. 1 Background 7
3.2 Scope 7
3.2.1 The EPA Program 8
3.2.2 Other Programs 16
3.3 Technical Basis for This Report 16
IV. SUMMARY 17
4. 1 Approach 17
4.2 Findings 18
4. 3 Effect of Process Variables 18
4.3. 1 Effect on Major Species Concentration
in Scrubber Liquor 20
4.3.2 Effect of Time on Scrubber Liquor Trace
Element Concentration 21
-v-
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CONTENTS (Continued)
4.3.3 Effect of pH on Scrubber Liquor Trace
Element Concentration 21
4.3.4 Effect of Absorbent on Scrubber Liquor
Trace Element Concentration 21
4. 3. 5 Effect of Coal Composition on Solid Waste
and Liquor Trace Element Concentration .... 22
4.4 Physical and Chemical Characteristics of Wastes 22
4. 4. 1 Physical Properties 22
4.4.2 Chemical Properties 26
4. 5 Disposal Economics 29
4. 5. 1 Chemical Treatment and Disposal 29
4. 5.2 Ponding 29
4.6 Environmental Assessment 29
4. 6. 1 Strength 30
4.6.2 Permeability 30
4.6. 3 Leachate Concentration 30
4.6.4 Leachate Mass Release 30
4.7 Disposal and Utilization Alternatives 31
4.8 Power Plant Water Recycle and Reuse . 32
4. 9 Full-Scale Applications 32
V. EPA-SPONSORED RESEARCH AND DEVELOPMENT 33
5. 1 Environmental Assessment of FGC Waste Disposal .... 34
5. 1. 1 FGC Waste Characterization, Disposal
Evaluation, and Transfer of Waste
Disposal Technology (The Aero- ;
space Corporation) 34
5. 1.2 Shawnee FGD Waste Disposal Field
Evaluation (TV A and The Aerospace
Corporation) 74
5. 1. 3 Laboratory and Field Evaluation of FGC
Waste Treatment Processes (U.S. Army
Engineer WES) ' 87
-vi-
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CONTENTS (Continued)
5. 1.4 Characterization of Effluents from
Coal-Fired Power Plants (TVA) 100
5. 1. 5 Fly Ash Characterization and
Disposal (TVA) 102
5.1.6 Studies of Attenuation of FGC Waste
Leachate by Soils (U.S. Army Materiel
Command) 105
5. 1. 7 Establishment of a Data Base for FGC
Waste Disposal Standards Development
(SCS Engineers) 108
5.2 Process Technology Assessment and New Technology
Development 109
5.2.1 Evaluation of FGD Waste Disposal Options
(Louisville Gas and Electric) 109
5.2.2 FGD Waste Leachate - Line r Compatibility
Studies (U.S. Army Engineer
WES) 110
5. 2. 3 Lime and Limestone Wet Scrubbing
Waste Characterization (TVA) 113
5.2.4 Dewatering Principles and Equipment
Design Studies (Auburn University) 115
5. $ Process Economics Studies 115
5. 3. 1 Conceptual Design and Cost Studies of
Alternative Methods for Lime and Lime-
stone Scrubbing Waste Disposal (TVA) ..... 116
5. 3.2 Gypsum By-Product Marketing Studies
(TVA) 117
5.4 Alternative FGC Waste Disposal Methods ijg
5. 4. 1 Evaluation of Alternative- FGD Waste
Disposal Sites (A. D. Little) 118
5. 5 Now FGC Waste Utilization Methods 120
5. 5. 1 Lime and Limestone Scrubbing Waste Conr
version Pilot Studies (Pullman-Kellogg). . . . 120
5-. 5.2 Fertilizer Production Using Lime and
Limestone Scrubbing Wastes (TVA). 121
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CONTENTS (Continued)
5. 5.3 Use of FGD Gypsum in Portland Cement
Manufacture (South Carolina Public
Service Authority) 123
5.5.4 FGD Waste and Fly Ash Beneficiation
Studies (TRW) 123
5.6 Improvement of Overall Power Plant Water Use 124
5.6.1 Assess and Demonstrate Power Plant
Water Recycle and Reuse (Radian) 124
5.7 EPA In-House Research 127
VI. UNIVERSITY-RELATED RESEARCH AND DEVELOPMENT. .. 129
6. 1 Auburn University 129
6.2 Illinois Institute of Technology 129
VII. INDUSTRIAL RESEARCH AND DEVELOPMENT AND
OPERATIONAL APPLICATIONS . . . 131
7. 1 Utility-Sponsored Research and Development 131
7. 1. 1 Ontario Hydro 131
7. 1.2 Southern California Edison 132
7.1.3 Southern Services 135
7. 1.4 Southwestern Public Service Company 141
7. 1. 5 Electrical Power Research Institute 141
7. 1.6 Commonwealth Edison Company 141
7.2 Utility Power Plant Applications 151
VIII. FOREIGN TECHNOLOGY 155
8. 1 Japan 155
8. 1. 1 Calcium Sulfite 155
8. 1. 2 Gypsum 156
8. 2 West Germany 159
REFERENCES 161
-Vlll-
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FIGURES
1. EPA Program Overview: Control of Waste and Water
Pollution from FGC Systems 12
2. EPA Program Evaluation Approach 19
3. Viscosity of FGD Wastes . 23'
4. Relationship Between Trace Metal Content in Coal and
FGD Waste Solids 43
5. Relationship Between Trace Metal Content in Coal and
FGD Waste Liquors 44
6. Leachate Analyses from TVA'Shawnee Untreated
Limestone Waste: Aerobic Conditions 48
7. Leachate Analyses from TVA Shawnee Untreated
Limestone Waste: Anaerobic Conditions 49
8. Leachate Analyses from TVA Shawnee Treated
Limestone Waste (Chemfix): Aerobic Conditions 52
9. Leachate Analyses from TVA Shawnee Treated
Limestone Waste (Chemfix): Anerobic Conditions 53
10. TVA Shawnee Limestone Clarifier Underflow Crystal
Structure 59
11. Viscosity of FGD Wastes 60
12. Wet Bulk Density of FGD Waste Sample 63
13. Permeability of Untreated and Treated FGD Wastes 66
-IX-
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FIGURES (Continued)
14. Compaction Characteristics of TVA Shawnee Limestone,
Untreated FGC Waste, June 15, 1974 68
15. Load Bearing Capacity of FGC Wastes 70
16. Results of Laboratory Column Leaching Tests
of Treated and Untreated Wastes 81
17. Mass Loading of TDS to Subsoil for Various Disposal
Modes of Treated and Untreated FGC Wastes 83
18. Conductivity Versus Dissolved Solids 95
19. Leaching Results: Sulfate, Sludge No. 100 97
20. Leaching Results: Sulfate, Sludge No. 500 98
21. Process for the Production of Solid Granular Fertilizer
Material from Scrubber Sludge 122
22. Sixty-Day Compressive Strength of Sulfate Sludge,
Pulverized Lime, and Fly Ash Mixtures 144
23. Permeability of Sulfate Sludge, Pulverized Lime, and
Fly Ash Mixtures 145
24. Relationship Between Compressive Strength and
Permeability 146
25. Strength of Various Types of Gypsum and Concrete 158
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TABLES
1. Relationship of Projects in FGC Waste and Water
Program to Areas of Interest 10
2. Project Status 13
3. Relative Change in Concentration of Constituents
in the Scrubber Circuit; Limestone Process 20
4. Range of Concentration of Constituents in
Scrubber Liquors . . . 27
5. FGD Systems Sampled as Data Base 36
6. Net Change in Scrubber Liquor Composition of
Major, Minor, and Trace Constituents Between
Initial and Final Stages in Scrubber System 38
7. Phase Composition of FGD Waste Solids
in Weight Percent 57
8. Dewatered Bulk Densities of FGD Wastes 62
9. Permeability of Untreated and Chemically Fixed
Wastes 65
10. Disposal Cost Ranges for Ponding and Chemical
Treatment .73
11. Pond and FGC Waste Characteristics 76
12. Pond Leachate Analyses . . . . 79
13. Cases Studied for Calculating Mass Loading
of Leachate Constituents into Subsoil 84
'. s ' -
14. Characteristics of Cores from Chemically Treated
FGC Wastes 86
-XI-
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TABLES (Continued)
15. FGC Waste and Chemical Treatment Matrix 89
16. Physical and Engineering Properties 91
17. Physical Properties of Untreated and Treated Wastes 92
18. Chemical Characteristics Tests of Untreated and Treated
FGC Wastes 94
19. Chemical Analyses on Samples for Site Surveys 99
20. List of Candidate Fixation Materials 101
21. Program Status 103
22. Sources of FGC Wastes and Soils in the Soil
Attenuation Test Program . 107
23. Liner Materials Ill
24. FGD Wastes 112
2^. Plants Selected for Water Recycle and Reuse Study 126
26. Mix Consistencies with Various Additives for Lakeview
Gas Scrubber Sludge with 65 Percent Solids 133
27. Effluent Analyses from a Lined Liquid-Waste Settling Pond ... 137
28. EPRI SOX Control Program: FGD Treatment and
Disposal 142
29. Solubility of Sulfate from Treated Sulfate Sludge Mixtures .... 148
30. Sulfate Analyses of Water in Contact with Treated
Solidified Sludge 149
31. Sulfate Content of lOO-mj? Aliquots from 20 g of
4x8 Solidified Sludge 150
32. FGC Chemical Treatment Processes: Utility Plant
Characteristics 152
33. FGC Waste Disposal Status 153
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ACKNOWLEDGMENTS
This report, prepared by The Aerospace Corporation, is the
result of a continuing cooperative effort of many individuals and organizations,
all of whom have made significant contributions to the projects being reported.
The authors wish to acknowledge Julian W. Jones, the U. S. Environmental
Agency Project Officer, for his guidance and continued assistance in con-
ducting this study and in providing timely access to data necessary for the
preparation of this report.
Paul P. Leo
Office of Stationary Systems
Office of Stationary Systems
Environment and Energy
Conservation Division
Approved
/Environment and Energy
Conservation Division
-Xlll-
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CONVERSION TABLE
A list of conversion factors for British units used in this
report is as follows:
British
1 acre
1 British thermal unit
per pound
1 foot
1 cubic foot per minute
1 inch
1 gallon
1 pound
1 mile
1 ton (short)
1 ton per square foot
1 gram per square foot
1 part per million
1 pound per square inch
1 cubic yard
Metric
4047 square meters
2.235 Joules per gram
0. 3048 meter
28. 316 liters
2. 54 centimeters
3. 785 liters
0.454 kilogram
1.609 kilometers
0.9072 metric tons
9765 kilograms per square meter
10.76 grams per square meter
1 milligram per liter (equivalent)
0.0703 kilogram per square
centimeter
0.7641 cubic meter
-xv-
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SECTION I
CONCLUSIONS
1. 1 BACKGROUND
This report summarizes and assesses the state of research
and development (R&D) in the fields of nonregenerable flue gas desulfuriza-
tion (FGD) waste treatment, disposal, and utilization as well as water re-
cycle and reuse for coal-fired utility power plants, with the ultimate objective
being directed toward definition of cost-effective environmentally acceptable
methods. A survey of the work being conducted indicates that a significant
portion of effort is currently being conducted under the direction of the U. S.
Environmental Protection Agency (EPA). Considerable efforts are also being
conducted by others, including utilities and industrial organizations. Although
most of these efforts are concerned with problems of a site-specific nature,
they contribute to the over all understanding of the technical fields under study.
The EPA program consists of 19 projects that address the broad
range of the flue gas cleaning (FGC) waste disposal and utilization spectrum.
The projects, which are in various stages of accomplishment, encompass the
areas of (1) technology and economic assessment of existing FGC waste treat-
ment, disposal, and utilization processes; (2) development of new or evolving
technology of treatment, utilization, and disposal; and (3) development of
methods to improve power plant water reuse. Physical and chemical charac-
terizations of untreated and treated FGD wastes from utility power plants
burning eastern and western coals with a range of scrubber facility sizes,
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using lime, limestone, and double-alkali processes, are being conducted. A
data base of criteria with which to assess environmental consequences of the
identified disposal or utilization options is also being compiled.
Many of the EPA and industry studies are in an early stage;
the EPA studies will require approximately one to two years to complete.
Therefore, firm conclusions regarding results to date are not warranted
at this time. However, some conclusions can be drawn relative to the EPA
program scope and its potential to meet program objectives, and observa-
tions can be made on the basis of information currently available.
1.2 CONCLUSIONS AND OBSERVATIONS
Federal regulatory guidelines have not been promulgated
which could be used to gauge the effects of FGD waste disposal on the quality
of ground-water and on land reclamation. The results from this program will
provide a data base for defining waste disposal standards and predicting
effects on ground and surface water quality.
Specific observations made to date are as follows:
a. FGC waste chemical characteristics were found to be a
function not only of the properties of coal and scrubber
absorbent but also of the scrubber-ope rating parameters,
primarily pH. The influence of operating variables on
waste characteristics is being systematically studied as
part of the program.
b. Physical and chemical properties of untreated and treated
FGD wastes and liquors have been determined for lime,
limestone, and double-alkali scrubber systems, using
eastern and western coals. The resultant properties are
process-and fuel-dependent. The data appear to be con-
sistent in cases where analyses from different laboratories
can be compared. Significant values are summarized in
Section IV.
c. Interim results of tests of FGC wastes have shown that
chemical treatment significantly improves the structural
characteristics of the FGD waste, reduces the solubility of
major chemical species by a factor of two to four and reduces
permeability by an order of magnitude or more. No appreci-
able reduction of the concentration of trace elements in the
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leachate has been noted when compared to untreated wastes.
Management of disposal sites to prevent collection of sur-
face water would be a significent factor in minimizing or
eliminating seepage through the waste.
d. With the increased acquisition of quantitative information
anticipated during the program, a data base will be formed
with which to determine the migration of major species and
trace elements into FGD waste disposal sites and to assess
the feasibility and environmental impact on alternative dis-
posal sites such as landfills, ponds, mines, and oceans.
This data base can be used by the EPA to define waste dis-
posal guidelines.
e. The economics of FGD waste disposal and utilization will be
defined in detail and will be available for assessment of the
various disposal and utilization options. Engineering
estimates of 30-year average total fixation and disposal
costs (capital and operating) for a typical 1000-megawatt (MW)
plant have been identified as $7. 30 to $11.40 per ton of sludge
(1975 dollars and dry weight basis). These estimates repre-
sent the range of costs for three different chemical treatment
processes. The costs equate to $2.07 to $3. 24 per ton of
coal and 0.9 to 1.4 mils per kilowatt hour (kWh). Costs of
disposing of untreated FGD wastes in lined ponds have been
reported as approximately 75 percent of the fixation-disposal
costs.
f. Work performed by utilities and chemical processors has
ranged from laboratory research on processes and character-
isitics of wastes to field evaluation of pilot plants and prototype
treatment processes . The work has focused on site-specific
problems of waste treatment and disposal faced by the utilities
involved. The results, in general, complement and augment
the EPA program.
g. At present, 8 stations have 13 units (5205 MW equivalent)
committed to full-scale chemical treatment and disposal of
FGD wastes through 1979. Of these, three units (767 MW)
are in operation, and startup by three others (1413 MW) is
planned by the end of 1976. The combined total for FGD
waste disposal by ponding, projected or in use by 21 power
plant units for 1976, is 4338 MW as contrasted to 2180 MW
with chemical fixation of FGD wastes. Projections to 1983
identify approximately 68 units of approximately 26,400 MW
committed to nonregenerable scrubbers, of which 15 units
(7155 MW) are committed to chemical fixation.
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SECTION II
RECOMMENDATIONS
2. 1 BACKGROUND
A review and assessment was conducted of all known research
and development (R & D) activities for flue gas cleaning (FGC) waste treat-
ment, disposal, and water reuse to determine the completeness of the cover-
age regarding a total understanding of the problems and potential solutions.
It was determined that current work, funded primarily by the U.S. Environ-
mental Protection Agency (EPA), addresses a broad range of questions that
must be answered prior to defining environmentally and economically sound
flue gas desulfurization (FGD) waste disposal methods. The results from the
EPA program, together with work being done by utilities and other organiza-
tions, form a significant data base to assist in achieving the stated objectives,
2.2 RECOMMENDATIONS
At present, no specific change in the direction of the EPA-
sponsored program objectives is recommended. The various projects
are complementary, and negligible duplication of effort was noted within
the EPA program and between the EPA projects and work being conducted
by others. For complete coverage of the problem, further considerations
are given in the following recommendations.
a. In testing conducted as part of the EPA program, it has been
determined that weathering deteriorates the physical prop-
erties of treated wastes. However, the data are limited, and
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follow-up work is recommended to define realistic test
conditions and quantify the freeze-thaw wet-dry effects on
the strength, permeability, and leaching characteristics of
treated wastes.
b. Although the EPA program will result in the compilation of
a data base encompassing the technology and properties of
FGD wastes whereby disposal criteria can be defined and
environmental impacts assessed, a series of detailed case
studies are recommended where conditions at typical dis-
posal sites in various regions of the United States may be
evaluated. Based on the type of waste produced at each site,
together with geological, climatalogical, and hydrological
factors and site management techniques, an assessment of
pollutant transport phenomena, environmental acceptability,
and impact of various disposal methods can be made.
c. Plans were announced recently by the Electric Power Research
Institute (EPRI) to sponsor projects for the development of a
reliable design basis for lime and limestone scrubbing.^ Re-
cently, a memorandum of understanding was signed by EPA
and EPRI calling for cooperation in research and development
in areas of mutual interest. Since the intent of the EPRI
and EPA FGD waste treatment and disposal programs appears
to be quite similar, it is recommended that a cooperate effort
be pursued from which complementary objectives and goals
can be derived and the duplication of effort minimized.
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SECTION III
INTRODUCTION
3. 1 BACKGROUND
A major consideration in the installation of flue gas cleaning
(FGC) systems is the necessity for disposing of or utilizing the by-products.
This applies to all coal-fired boilers, especially those with nonregenerable
flue gas desulfurization (FGD) systems. Application of FGD systems in the
United States is accelerating; the major portion of these are lime and lime-
stone wet scrubbing systems, which produce a calcium sulfite waste. En-
vironmental and economic concerns related to the disposition of this FGD
waste are reflected in a broad range of research, development, and demon-
stration programs for its treatment and disposal.
A significant portion of the national effort is currently being
funded by the Environmental Protection Agency (EPA). Nineteen different
EPA projects are under way; the funding through fiscal year (FY) 1976 has
been identified as $6.95 million, with an additional $4.7 million projected
through FY 1980. Work has also been and is being conducted by utilities and
other industrial organizations involved in the treatment and disposal process.
In addition, full-scale systems are currently in operation, and others are
in various stages of planning and implementation.
3.2 SCOPE
The Aerospace Corporation under Task 9 of EPA Contract
No. 68-02-1010 has been contracted to integrate and evaluate the research
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and development (R & D) work being performed in the area of FGD waste
treatment disposal and utilization, as well as overall power plant water re-
cycle and reuse. This report is the first of an annual series that provides
an evaluation of the R & D results of the EPA-funded projects, as well as
those being conducted by other United States and foreign industrial organiza-
tions and by universities. The assessment of the results and technology is
related to the definition of environmentally sound and economic disposal of
or utilization of FGD wastes. In addition, a summary of the status of full-
scale operational FGD waste disposal systems is reported.
3.2.1 The EPA Program
In late 19?4, plans were formulated to greatly expand existing
EPA FGD waste disposal R & D efforts. These efforts were aimed at deter-
mining pertinent environmental parameters, reducing costs, investigating
alternative strategies, and encouraging waste-product usage. Although the
major emphasis was on FGD wastes, the plans involved consideration of
overall power plant waste and water problems, including the disposal and
utilization of coal ash. For this reason, the new program was entitled "Con-
trol of Waste and Water Pollution from Flue Gas Cleaning (FGC) Systems" or,
for brevity, the "FGC Waste and Water Program. "
The objectives of the FGC Waste and Water Program are to
evaluate, develop, demonstrate, and recommend environmentally acceptable
cost-effective techniques for disposal and utilization of FGC wastes and to
evaluate and demonstrate systems for maximizing power plant water recycling
and reuse. The projects, in general, fall into one of six main categories:
(1) environmental assessment of FGC waste disposal, (2) technology assess-
ment development, (3) disposal economics, (4) alternative disposal methods,
(5) utilization of wastes, and (6) overall power plant water use.
The environmental assessment projects include FGC waste
characterization studies; laboratory and pilot field studies of disposal tech-
niques for chemically treated FGD sludges; characterization of coal-pile
drainage, coal ash, and other power plant effluents; and studies of attenuation
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of FGC waste leachate by soils. Chemical and physical properties have been
determined by several laboratories for untreated FGC wastes from a total of
11 scrubbers and wastes treated by 5 distinct processes.
The technology assessment and development efforts include
field studies of untreated and chemically treated FGC wastes; FGC waste
leachate-disposal site liner compatibility studies; studies to correlate waste
solid characteristics with scrubber operating conditions; and dewatering
equipment design studies. The economic studies include cost estimates of
current disposal practices (e.g. , ponding, landfill) and by-product marketing
studies. Alternative disposal method studies include both mine and o.cean
disposal assessments. Utilization projects include development of a process
for FGC waste conversion (to sulfur and calcium carbonate); pilot studies
of fertilizer production (using the waste as a filler material and a source of
sulfur); use of FGD gypsum in portland cement manufacture; and FGC waste
beneficiation studies. Although the work on power plant water use is a single
study to maximize waste water reuse in the total power plant water system,
the results from this project will be integrated with the studies of power
plant effluents described earlier.
Table 1 shows the relationship of each of the projects to the
areas of interest. Whereas four of the projects are aimed at investigating
one1 specific area, the others cover several areas of interest. This is to be
expected, since it would be difficult, for example, to fairly assess the tech-
nology of a process without examining both the economics and the environ-
mental effects. An overview of the EPA program as it relates to the various
elements of the FGC solid waste and liquid effluent generation, treatment,
disposal, and utilization is shown in Figure 1. The projects and contractors
are identified and keyed to the elements of the system addressed.
In Section V each of the projects is discussed, and the current
project status and results are described. These are listed under the heading
of the main area of interest. Table 2 identifies the EPA project officer, con-
tractor project director, start date, and duration for each of the projects,
as well as the section in which each of these projects is discussed.
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Table 1. RELATIONSHIP OF PROJECTS IN FGC WASTE AND
WATER PROGRAM TO AREAS OF INTEREST
Project
FGC Waste Characterization
and Disposal Evaluation
Shawnee FGD Waste Disposal
Field Evaluation
Laboratory and Field Evalua-
tion of FGC Treatment
Processes
Characterization of Effluents
from Coal-Fired Power
Plants
Fly Ash Characterization and
Disposal
Attenuation of FGC Waste
Leachate by Soils
Establishment of Data Base
for FGC Disposal Standards
Evaluation of FGD Waste
Disposal Options
FGD Waste Leachate -
Liner Compatibility
Scrubber Waste
Characterization
Dewatering Principles and
Equipment Design
Conceptual Design-Cost
Studies of Alternative
Methods for FGC Waste
Disposal
Contractor
Aerospace
TVAC and Aerospace
U. S. Army WESd
TVAe
TVAe
U.S. Army, Dugway
scsg
LG&Eh
U.S. Army, WESd
TVAe
Auburn Ul
TVAJ
Environmental
Assessment
x
X
X
X
X
X
X
X
Technology
Assessment
and Development
X
X
X
X
X
3f ;
X
X
x- ' ;
X
Economic
Studies
X
X
X
X
X
Alternative
Disposal
Methods
X
X
X
Utilization
Methods
Development
-
Overall
Power Plant
Water Use
X
I
I-*.
o
(Continued)
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Table 1. RELATIONSHIP OF PROJECTS IN FGC WASTE AND WATER
PROGRAM TO AREAS OF INTEREST (Continued)
Project
Gypsum By- Product
Marketing Studies
Evaluation of Alternative
FGC Waste Disposal Sites
Scrubbing Waste Conversion
Studies
Fertilizer Production Using
Scrubbing Wastes
Use of FGD Gypsum in
Portland Cement
FGD Waste and Fly Ash
Beneficiation
Assess and Demonstrate
Power Plant Water Reuse
and Recycle
Contractor
TVAJ
A. D. Littlek
Pullman Kellogg1
TVAj
SCPSA, Santee
Cement, and B&Wm
TRWn
Radian
Environmental
Assessment
X
Technology
Assessment
and Development
X
X
X
X
X
Economic
Studies
3£
X
X
X
X
X
X
Alternative
Disposal
Methods
X
Utilization
Methods
Development
X
X
X
X
X
Overall
Power Plant
Water Use
X
Reference 2. Primary area of interest is indicated by shaded areas.
The Aerospace Corporation, El Segundo, California.
Tennessee Valley Authority (TVA), Division of Chemical Development, Muscle Shoals, Alabama.
U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi.
eTVA, Power Research Staff, Chattanooga, Tennessee.
U.S. Army Materiel Command, Dugway Proving Ground, Utah.
Engineers, Long Beach, California.
Louisville Gas and Electric Company (LG&E), Louisville, Kentucky.
"Auburn University, Auburn, Alabama.
-'TVA, Office of Agricultural and Chemical Development (OACD), Muscle Shoals, Alabama.
k
Arthur D. Little, Inc., Cambridge, Massachusetts.
Pullman Kellogg Company, Houston, Texas.
mSouth Carolina Public Service Authority (SCPSA)f Moncks Corner, South Carolina; Santee Portland
Cement Corporation, Holly Hill, South Carolina; and Babcock & Wilcox, Barberton, Ohio.
"TRW Systems Group, Redondo Beach, California.
Radian, Inc. , Austin, Texas.
-------
• CHARACTERIZATION OF
EFFLUENTS FROM COAL-FIRED
POWER PLANTS (TVA).A.C.L
FLY ASH CHARACTERIZATION
AND DISPOSAL (TVA) C.M.H
ASSESS AND DEMONSTRATE
POWER PLANT WATER REUSE/
RECYCLE (Radian) L.B, K
• LIME AND LIMESTONE SCRUBBING • FGC WASTE CHARACTERIZATION • LABORATORY AND FIELD EVALU-
WASTE CHARACTERIZATION (TVAI AND DISPOSAL EVALUATION
(Aerospace)
G. H. K. L, M
j 2 ?
DEWATERING PRINCIPLES AND
EQUIPMENT DESIGN STUDIES
(Auburn U) F
ro
i
ATION OF FGC TREATMENT
PROCESSES (U.S. Army WES)
G, E?H
• EVALUATION OF FGC WASTE
DISPOSAL OPTIONS (LG&EI
G, H
• CONCEPTUAL DESIGN AND COST
STUDIES OF ALTERNATIVE
METHODS FOR LIME AND
LIMESTONE SCRUBBING WASTE
DISPOSAL (TVA)G. H
• LIME AND LIMESTONE SCRUBBING
WASTE CONVERSION PI LOT
STUDIES (Pullman-Kellogg)
• FERTILIZER PRODUCTION USING
LIME AND LIMESTONE SCRUBBING
WASTES (TVA) I, J
• USE OF FGD GYPSUM IN
PORTLAND CEMENT
MANUFACTURING (SCPSA). I. J
• SHAWNEE FGD WASTE DISPOSAL
FIELD EVALUATION (TVA and
Aerospace) H. G, E2
• ATTENUATION OF FGC WASTE
LEACHATE BY SOILS (U.S.
Army. Dugway) H
• ESTABLISHMENT OF DATA BASE
FOR FGC WASTE DISPOSAL
STANDARDS DEVELOPMENT
(SCS Engr) H
• ALTERNATIVE DISPOSAL
METHODS DEVELOPMENT
(A. D. Little) H
• FGC WASTE LEACHATE-LINER
COMPATIBILITY (U.S. Army
WES) H
• FGD WASTE AND FLYASH
BENEFICIATION STUDIES
(TRW) J. I
• GYPSUM BY-PRODUCT
MARKETING STUDIES (TVA) J
Figure 1. EPA program overview: control of waste and water
pollution"from FGC systems
-------
Table 2. PROJECT STATUS
Project Title
of FGC Waste Disnosal
tion. Disposal Evaluation,
and Technology Transfer
Shawnee FGD Waste
Disposal Field
Evaluation
Laboratory and Field
Evaluation of FGC Waste
a. Pollution Potential of
Untreated and Chemi-
cally Fixed Sludges
b. Site Survey and Environ-
mental Assessment of
Existing Solid Waste
Disposal Sites
c. Evaluation of Existing
Fixation Technology
Characterization of Effluents
from Coal-Fired Power
Plants
and Disposal
Studies of Attenuation of
FGC Waste Leachate by
Soils
EPA Project Officer
Industrial Environmental Research
Laboratory (IERL)
Research Triangle Park. NC
J. W. Jones
IERL
Research Triangle Park, NC
R. E. Landreth
Municipal Environmental
Cincinnatti, OH
J. W. Jones
R. A. Venezia
IERL
Research Triangle Park, NC
JW Tr\naa
. w . j one B
R. A. Venezia
IERL
Research Triangle Park, NC
M. Roulier
MERL
Cincinnatti, OH
Contractor Project Director
The Aerospace Corporation
El Segundo, CA
J. Schultz
TVA, Division of Chemical
Development
Muscle Shoals, AL
J. Rossoff
The Aerospace Corporation
El Segundo, CA
J. L. Mahloch
U.S. Army Engineer
(WES)
Vicksburg, MS
B. G. McKinney
H. B. Flora
TVA Power Research Staff
Chattanooga, TN
Sc p a-_
. o. t^ay
TVA, Power Research Staff
Chattanooga, TN
M. Houle
U.S. Army Materiel Command
Dugway Proving Ground
Dugway, UT
Start Date
Nov 197 E
Sep 1974
a. Jul
1974
b. Jul
1975
c. Jul
1975
Apr 1975
A __ | Q7C
Apr iv 13
Dec 1975
Duration, Months
50
34
a. 36
b. 24
c. 26
50
42
24
Type of Study
analyses:
technical
and economic
Field
evaluation
a. Laboratory
b. Laboratory.
field
c. Laboratory
Laboratory,
field
field
Laboratory
Section Ref-
erenced in
This Report
5. 1
511
5. l.Z
5. 1.3
5. 1.3. 1
5. 1.3.Z
5. 1.3.3
5. 1.4
515
5. 1.6
(Continued)
-------
Table 2. PROJECT STATUS (Continued)
Project Title
Establishment of a Data Base
for FGC Waste Disposal
Standards Development
Process Technology Assess-
ment and New Technology
Development
Evaluation of FGD Waste
Disposal Options
FGD Waste Leachate-Liner
Compatibility
Lime and Limestone Wet
Scrubbing Waste
Dewatering Principles and
Equipment Design Studies
Process Economics Studies
Conceptual Design and Cost
Studies of Alternative
Methods for Lime and Lime-
stone Scrubbing Waste
Disposal
Gypsum By-Product Marketing
Studies
Alternative FGC Waste
Disposal Methods
Evaluation of Alternative FGD
Waste Disposal Sites
EPA Project Officer
D. E. Sanning
MERL
Cincinnatti, OH
J. W. Jones
IERL
Research Triangle Park, NC
R. E. Landreth
MERL
Cincinnatti, OH
J. W. Jones
IZRL
J. W. Jones
IERL
Research Triangle Park, NC
R. D. Stern
IERL
Research Triangle Park, NC
C. J. Chatlynne
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
'Contractor Project Director
C. J. Schmidt
SCS Engineers
Long Beach, CA
R. P. Van Ness
Louisville Gas and Electric Co.
Louisville. KY
Z. B. Fry
U.S. Army WES
Vicksburg, MS
J. L. Crowe
TVA Power. Research Staff
J. C. Warman
Auburn University
Auburn, AL
H. L. Faucett
TVA, Office of Agricultural and
Chemical Development (OACD)
Muscle Shoals, AL
J. I. Bucy
TVA, OACD
Muscle Shoals, AL
R. R. Lunt
Arthur D. Little, Inc.
Cambridge, MA
Start Date
Dec 1975
Being
negotiated
Jul 1975
May 1975
Being
negotiated
Jan 1976
Jan 1976
Jul 1975
Duration, Months
15
18
30
28
27
18
12
8
Type of Study
Technical
analysis
Laboratory.
field
Laboratory
Laboratory,
field
Laboratory
Technical and
economic
analyses
Technical and
economic an
analyses
Technical
analysis
Section
5. 1.7
5.2
5.2. 1
5.2. Z
5.2.3
5.2.4
5.3
5.3. 1
5.3.2
5.4
5.4. 1
(Continued)
-------
Table 2. PROJECT STATUS (Continued)
Project Title
New FGC Waste Utilization
Methods
Lime and Limestone Scrubbing
Waste Conversion Pilot Studies
Lime and Limestone
Scrubbing Wastes
Use of FGD Gypsum in
Portland Cement
Manufacturing
FGD Waste and Fly Ash
Beneficiation Studies
Improving Overall Power
Plant Water Use
Assess and Demonstrate
Power Plant Water
Reuse and Recycle
EPA Project Officer
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
F. A. Roberts
IERL
Research Triangle Park, NC
Contractor Project Director
A, G. Sliger
Pullman Kellogg Company
Houston, TX
J. L. Crowe
TVA, Power Research Staff
Chattanooga, TN
M. O. McNinch
SCPSA
Moncks Corner, SC
J. Blumenthal
TRW Systems Group
Redondo Beach, CA
D. M. Ottmers
Radian, Inc.
Austin, TX
Start Date
Being
negotiated
May 1975
Being
Negotiated
Mar 1976
July 1975
Duration, Months
11
41
(plus 18 for
field tests)
6
13
Type of Study
Bench, pilot
plant
Pilot plant,
field tests
Laboratory,
pilot plant,
full-scale
process
evaluation
Conceptual
design,
bench,
pilot plant
Analysis of
field data,
computer
simulation
Section
5. 5
5.5. 1
5.5.2
5.5.3
5.5.4
5. 6
5.6. 1
; •
-------
3.2.2 Other Programs
Other organizations including utilities and FGD waste fixation
contractors have conducted work on various aspects of the overall disposal
problem that are generally of a site-specific nature. The results of work
conducted by United States industrial organizations are discussed in Sec-
tion VII, and the status of full-scale operational FGD waste disposal system
is provided in this section. Section VI provides information on university-
related work, and foreign technology is discussed in Section VIII.
3.3 TECHNICAL BASIS FOR THIS REPORT
This initial report is based generally on published information
available through December 1975. During its preparation, a significant
amount of information not available previously was presented at the 1976 EPA
symposium on FGD in New Orleans and is included. Annual updating of
this report is planned by the EPA.
-16-
-------
SECTION IV
SUMMARY
This initial report summarizes and evaluates the research and
development (R&D) work being done in the field of coal-fired utility power
plant flue gas cleaning (FGC) waste treatment, disposal, and utilization and
overall power plant water recycle and reuse. The results of the various
projects being funded by the U.S. Environmental Protection Agency (EPA)
and private industry are viewed with the ultimate objective of recommend-
ing environmentally acceptable cost-effective waste disposal and utilization
methods.
4. 1 APPROACH
Nineteen EPA projects encompass the areas of (1) technology
and economic assessment of existing FGC waste treatment, disposal, and
utilization processes; (2) development of new or evolving technology of treat-
ment, utilization, and disposal; and (3) development of methods to improve
overall power plant water use.
Some of the EPA projects are just being initiated while others
have been under way for several years. The projects that address the physi-
cal and chemical characterization of the FGC wastes have been funded for
the longest periods. Therefore, considerable information required in the
evaluation process in these areas is available and is summarized. This
report includes data available through December 1975; other significant
information published during preparation of this report is also included.
-17-
-------
A diagram defining the approach being taken in the evaluation
of the work being conducted in the EPA program is given in Figure 2. Indus-
trial organizations have conducted privately funded work, primarily on prob- '
lems of a site-specific nature. The work performed by these organizations
(described in Sections VI and VII) will serve to supplement the EPA program
results and will also be reported by EPA as the results are made public.
4.2 FINDINGS
A summary of the findings is presented in the following areas:
a. Effect of process variables on waste characteristics .
b. Physical and chemical characterization of wastes
c. Disposal economics
d. Environmental assessment
e. Disposal alternatives
The status of operational flue gas desulfurization (FGD) disposal is also
included.
Significant data exist for items a, b, and c. Some insights
into the environmental assessment and the various disposal alternatives
(items d and e) are available, but results and recommendations in these areas
depend to a great extent on the outcome of future work. Firm conclusions
and recommendations in all areas will emerge as more information becomes
available over the next one to two years.
4.3 EFFECT OF PROCESS VARIABLES
A number of variables affects the chemistry of the various
process streams and results in different chemical characteristics and prop-
erties of the materials to be disposed.
The results are based on chemical analyses of samples from
seven different scrubbers having capacities ranging from 1 to 125 MW equiva-
lent. They are reported as a function of location within a scrubber circuit as
well as a function of time, pH, absorbent, and coal composition.
-18-
-------
DATA BASE
COMPILE CRITERIA
1
*
IIMTRFATFn
UIM 1 ntAI tU
EFFECT OF
PROCESS
VARIABLES
SECTION 4.3
DEFINE AND
EVALUATE DISPOSAL
AND UTILIZATION
TECHNOLOGIES
SECTION 4.4
ENVIRONMENTAL
ASSESSMENT
SECTION 4.6
ECONOMICS
SECTION 4.5
DISPOSAL AND
UTILIZATION
ALTERNATIVES
SECTION 4.7
Figure 2. EPA program evaluation approach
-------
A systematic and detailed evaluation of process variable effects
on the scrubber solids is being attempted by the Tennessee Valley Authority
(TVA) using the two 10-MW prototype lime and limestone scrubbing systems
at the Shawnee plant.
4.3. 1
Effect on Major Species Concentration in
Scrubber Liquors
The effect of process variables on the concentration of chemi-
cal constituents was determined as a function of the location within a scrubber
circuit, as well as a function of the scrubber process itself, i. e. , lime, lime-
stone, and double-alkalis.
The various constituents are affected differently. The end-to-
end changes for the various constituents relating the constituent concentra-
tions of the solid waste supernate to those in the scrubber liquors are shown
in Table 3.
Table 3. RELATIVE CHANGE IN CONCENTRATION OF CONSTITUENTS
IN THE SCRUBBER CIRCUIT: LIMESTONE PROCESS
Constituent
Calcium
Chloride
Sulfite
Sulfate
Trace Metals
pH
Typical Change in Concentration Between
Scrubber and Disposal Stagea
Direction of Change
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Change Between Scrubber Stage
and Disposal Stream
30 to 40%
20%
>99%
10%
10 to 20%
2 units
Reference 37
-20-
-------
4.3.2 Effect of Time on Scrubber Liquor Trace
Element Concentration
The effect of time on trace element concentration from
scrubber startup was reported and is summarized as follows:
a. Trace element concentrations reached steady-state levels
after building up during an initial scrubber startup period
b. For lead, there was a direct relationship between concen-
tration and time.
4. 3. 3 Effect of pH on Scrubber Liquor Trace Element
Concentration
Within an individual process, no correlation was detected
between trace element concentration and scrubber liquor pH, except for
lead, which generally increased with increasing pH.
4.3.4 Effect of Absorbent on Scrubber Liquor Trace
Element Concentration
The relative concentration of trace elements in scrubber
liquors from the limestone, lime, and double-alkali processes has been
determined. Generally, trace element concentrations were highest in the
limestone system, intermediate in the lime, and lowest in the double-alkali
process; however, the actual concentration differences attributable to the
process are not considered significant relative to their pollutional potential.
The data indicate that the concentration effect is a consequence of pH within
the respective scrubbers and as such is not a pollution control mechanism.
4. 3. 5 Effect of Coal Composition on Solid Waste and
Liquor Trace Element Concentration
The concentration of trace metals in treated solids was re-
5
ported as exhibiting a linear relationship with the concentration in the coal.
The trace metal concentration measured in the sludge liquor was two orders
of magnitude lower than that measured in the solids.
-21-
-------
The major source of trace metals in the solid waste is the
coal. Also, the concentration of various trace elements in sludge parallels
the differing concentrations typically found in eastern and western coals.
4.4 PHYSICAL AND CHEMICAL CHARACTERISTICS
OF WASTES
4. 4. 1 Physical Properties
Properties that define handling and engineering characteristics
4 5 12 14
of untreated and treated sludges have been reported. ' ' ' These include
viscosity, bulk density, and dewatering characteristics; porosity; permea-
bility; and unconfined compressive strength.
Viscosity is a major factor in determining pumping power
requirements. Bulk density data are needed in defining the volume of waste
and disposal site acreage, and dewatering characteristics are important in
defining treatment or conditioning requirements as well as achieving the
potential of specific bulk densities. Compressive strength provides a mea-
sure of structural quality. Porosity and permeability determine rate of
leachate penetration through the solid waste mass. Hence, the rate and
quantity of leachate constituents entering the ground, i.e., mass loading,
can be defined.
4.4.1.1 Viscosity
The viscosity of FGD wastes from seven power plants is pre-
sented as a function of solids content in Figure 3. The results show that of
the wastes tested, pumpable mixtures (< 20 poise) range from a high solids
content of 70 percent for the Cholla limestone sample to a low solids content
of 32 percent for both the Utah and GM double-alkali samples. Considering
this wide range of solids content, the importance of experimentally deter-
mining the viscosity becomes evident.
Test results suggest that fly ash in FGD wastes decreases
the viscosity of FGD wastes. Particle shape, size, and distribution may
influence viscosity, but the extent is indeterminant at present.
-22-
-------
CURVE
SOURCE
DATE FLY ASH.
ARIZONA CHOLLA LIMESTONE
SCE MOHAVE LIMESTONE
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
DUQUESNE PHILLIPS LIME
TVA SHAWNEE LIME
UTAH GADSBY DOUBLE ALKALI
GM PARMA DOUBLE ALKALI
4/1/74
3/30/73
7/11/73
6/15/74
2/1/73
6/17/74
3/19/74
8/9/74
7/18/74
58.7
3.0
40.9
40.1
20.1
59.7
40.5
8.6
7.4
120
100
80
o
Q.
>f 60
o
o
to
40
20
i i i i i i
70
60 50
SOLIDS CONTENT. WEIGHT
40
30
Figure 3. Viscosity of FGD wastes
-23-
-------
4.4.1.2 Bulk Density
The dry bulk density of untreated FGC wastes is reported
3
to be in the range of 0. 75 to 1.01 g/cm. (47 to 63 pcf), the actual value being
scrubbing-process and coal-source dependent.
For the wastes examined, chemical treatment increases the
dry bulk density to approximately 0. 80 to 1. 12 g/m (50 to 70 pcf) for wastes
3 3
with 0.75 g/cm untreated density, and 1.28 to 1.76 g/cm (80 to 110 pcf)
for those characterized by the higher 1.01 g/cm untreated densities. Again,
coal source and scrubbing process appear to affect the values.
Dewatering techniques such as settling, draining, centrifuging,
and filtration have a marked effect on the resultant bulk density. Generally,
3
the wet bulk density varied from a low of approximately 1. 52 g/cm (95 pcf),
settled, to a high of 1.76 g/cm (110 pcf), filtered. Drained and centrifuged
values were intermediate to these extremes. These values were determined
under laboratory conditions and may not necessarily be representative of
commercial processes.
Some settling characteristics of wastes from lime and lime-
stone scrubbing processes have been reported informally by TVA. For the
wastes examined, settling rate curves for lime wastes are continuous,
whereas settling curves for limestone wastes exhibit a discontinuity result-
ing in a sharp increase in settling rate prior to reaching maximum settled
density.
4. 4. 1.3 Porosity
Porosity of untreated wastes were found to be in the range of
48 to 75 percent. Chemical treatment tended to reduce porosity signifi-
cantly, in some processes, to values of 35 to 55 percent, while other pro-
cesses produced a solid with little change, remaining primarily in the 70 to
75 percent range.
-24-
-------
4. 4. 1. 4 Permeability
The permeability coefficients of untreated wastes were
-4 -5 5 12
reported to be in the range of 10 to 10 cm/sec. ' These values are
intermediate to typical values for silty sand and sandy clay, which are
-4 -6
10 cm/sec and 5X10 cm/sec, respectively. Chemical treatment
tended to reduce permeability by less than a factor of two in some cases,
and several orders of magnitude in others. The chemical treatment pro-
cess used appears to be the major determinant in the magnitude of the
reduction.
Weathering such as freezing and thawing has been reported to
12
break up the monolithic structure of certain treated wastes. The permea-
bility of several treated wastes that were mechanically fractured and pow-
dered to simulate extensive weathering exhibited permeability values approx-
imately the same as for untreated wastes. Fracturing (but not powdering)
and compacting resulted in about one order of magnitude reduction of per-
meability relative to the powdered condition.
4.4.1.5 Compressive Strength
Unconfined compressive strength of untreated wastes is low.
No specific values are reported since the material is considered nonstruc-
tural. Chemically treated sludges exhibited unconfined compressive strengths
ranging from approximately 25 psi to as high as 4500 psi in laboratory
studies, ' ' However, commercial processes being used at power sta-
tions today produce values in the range of 25 to 400 psi. Materials with un-
confined compressive strengths of 25 psi are considered capable of support-
ing heavy-equipment traffic.
A relationship between permeability and unconfined compres-
sive strength of treated wastes may exist, i. e. , the lower the compressive
strength, the higher the permeability. However, the correlation has not
been established using a broad range of wastes.
-25-
-------
4. 4. 2 Chemical Properties
Chemical properties of scrubber waste liquors and solids and
FGC waste leachates have been reported. ' More data are becoming avail-
able on FGC waste leaching characteristics as the program progresses and
are being used to define long-term trends.
Chemical, x-ray, and scanning electron microscope analyses
of the solid fractions of the wastes have shown the uniqueness of the charac-
teristics, with properties affected by coal composition and scrubber oper-
ating variables.
4. 4. 2. 1 Quality of Scrubber Liquors
The range of concentrations of scrubber liquor constituents
from five utility power plants is shown in Table 4. On the basis of the con-
stituent levels in the liquor stream and the probability that the scrubber
represents the end-of-the-line in the overall utilization of recycled power
plant water, any purged water would require treatment prior to disposal.
4.4.2.2 Leaching Characteristics
4.4.2.2.1 Untreated Wastes
From an overall assessment of leaching data, it was con-
cluded that for the major species, i.e. , sulfate and chloride ions, and total
dissolved solids (TDS), concentration in the leachate decreases rapidly dur-
ing the first three pore volume displacements (PVD) where about 90 percent
of the decrease takes place relative to the fifth pore volume. The concen-
trations at the 50th pore volume are approximately the same as at the 5th.
For untreated wastes, the pH of the leaching solution showed
no discernible effect on the leachate except for the trace elements lead and
zinc, which were leached more readily by acidic conditions.
Untreated wastes have been leached under both aerobic and
anaerobic leaching conditions. The anaerobic conditions simulated the effect
of wastes with a high affinity for oxygen as is the case for sulfite sludges or
-26-
-------
Table 4. RANGE OF CONCENTRATION OF
CONSTITUENTS IN SCRUBBER
LIQUORS6
Constituent
Range of
Potential
Concentration at
Discharge Point,
mg/t
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Tin (Sn)
Vanadium (V )
Zinc (Zn)
Carbonate (CO,)
Chloride (Cl)
Fluoride (F)
Sulfite (SO )
Sulfate (SO4)
Phosphate (PO4)
Nitrogen (N) (total)
Chemical Oxygen Demand
TDS
Total Alkalinity (as CaCO,)
Conductance, mho /cm
Turbidity, Jackson units
PH
0.03
0.09
< 0.004
< 0.002
8.0
0.004
520.
0.01
0. 10
< 0.002
0.02
0.01
3.0
0.09
0.0004
0.91
0.05
5.9
< 0.001
0.2
0.005
14.0
3. 1
< 0.001
0.01
< 1.0
420.
0.07
0.8
720.
0.03
< 0.001
60.
3200.
41.
0.003
< 3.
3.04
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
0.3
2.3
0.3
0. 14
46.
0. 11
3000.
0.5
0.7
0.2
8. 1
0.4
2750.
2. 5
0.07
6.3
1.5
32.
2.2
3.3
0.6
2400.
3.5
0.67
0.35
< 10.
4800.
10.
3500.
10,000.
0.41
0.002
390.
15,000.
150.
0.015
< 10.
10.7
-27-
-------
conditions in the lower layers of wastes in a covered landfill. The results
showed that, at any given displacement volume, a greater drop in concen-
trations of major species in the leachate occurs with anaerobic conditions
than with aerobic conditions. At the fifth pore volume for aerobic conditions,
the sulfate concentrations reached 1100 to 1300 mg/i and chloride 95 to
130 mg/l, irrespective of the initial concentration in the mother liquor.
The corresponding concentrations for the anaerobic conditions are 900 to
1100 mg/S. and 65 to 70 mg/jf for sulfate and chloride ion concentrations,
respectively. No relationship of this nature has been found for trace metals.
4.4.2.2.2 Treated Wastes
As with untreated wastes, the reduction of major species con-
centrations generally takes place within the first three pore volumes.
On the basis of laboratory and field test results, it was re-
ported that the concentration of the TDS in the first pore volume of the treated
leachate is approximately 50 percent of the untreated sludge leachate. After
the initial flushing period of 3 to 5 pore volumes, the concentrations generally
remained constant thereafter with values from the treated wastes being
approximately 25 to 50 percent of those from the untreated wastes.
On the basis of somewhat limited leaching tests evaluating
five chemical treatment processes, another laboratory has reported mixed
results relative to improvement in the leachate quality from treated wastes.
However, further testing is being conducted, as planned, to verify initial
trends and to permit an assessment of the performance of each of the five
individual chemical processes.
The effect of chemical treatment on immobilizing trace ele-
ments is not discernable at present when compared to untreated materials
5
because of low concentrations and significant scatter in much of the data.
With additional leaching data, statistical techniques may be useful to deter-
mine the effect of chemical treatment. Also, there is some evidence to sug-
gest that in certain instances the additives used in the chemical treatment of
FGD wastes may be contributing trace metals to the leachate.
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4. 5 DISPOSAL ECONOMICS
4. 5. 1 Chemical Treatment and Disposal
Engineering estimate costs for disposal of chemically treated
FCC wastes from a 1000-MW plant burning eastern coal were reported:
Total Disposal Costs, 1975 Dollars, 30-Year Average
Sludge, Including
Fly Ash, per Ton Coal per Ton
(Dry Basis) (Eastern) Mills per kWh
$7. 30 to 11. 40 $2. 07 to 3. 24 0.9 to 1/4
These costs represent the range of estimates for three fixation-
disposal processes. The average annual operating load factor was assumed
to be 50 percent over a 30-year lifetime, with the disposal site 5 miles away
from the power plant. Locating the disposal site 0. 5 mile from the power
plant rather than 5 miles and increasing the annual average operating load
factor from 50 to 65 percent reduces the disposal costs by approximately 9
and 7 percent, respectively. More detailed cost analyses of several dis-
posal processes will be conducted by TVA, and results from this study will
be reported as they become available.
4. 5. 2 Ponding
Disposal pond costs are dependent on construction and material
factors as well as land costs. For PVC-20 and Hypalon-30 materials, which
represent a reasonable range of liner material costs, the disposal costs on
a dry weight basis for a 1000-MW plant are $5. 70 to 7. 80 per ton of sludge,
or approximately 75 percent of those for chemical treatment and disposal.
4.6 ENVIRONMENTAL ASSESSMENT
Data from the various projects are not sufficient for an over-
all environmental assessment of the effects of disposal on water quality and
land reclamation. It has been determined that untreated waste chemical
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properties tend to be a function of the coal and scrubbing process variables.
Furthermore, chemically treated waste characteristics are also a function
of the treatment process itself. Prime factors to be considered in the dis-
posal of FGD wastes are as follows.
4.6.1 Strength
Because of the thixotropic nature and structural characteris-
tics of untreated wastes, personnel and equipment safety cannot be assured.
Treated material, depending on the fixation process and the solids content,
can be expected to achieve strengths in excess of those considered minimal
for supporting personnel and equipment and, in some cases, building struc-
tures. The long-range effect of weathering, i.e., wet-dry and freeze-thaw
cycling, is yet to be defined.
4.6.2 Permeability
_4
Permeability of untreated material is approximately 10 to
10 cm/sec. Chemical treatment tends to reduce these values over a broad
range, from negligible to several orders of magnitude depending on the pro-
cess selected. The long-range effect or weathering on permeability is yet to
be determined.
4.6.3 Leachate Concentration
Laboratory and field leaching data have shown that leachate
concentrations of major species in the leachate from fixed materials are
about 25 to 50 percent of the concentrations of major species in untreated
materials.
4.6.4 Leachate Mass Release
The mass release of major constituents into the soil from
chemically fixed materials is reduced as a result of lower permeability of
the treated wastes, as well as a reduction of the solubility of major pollutant
constituents. Treatment process and mode of disposal, i.e., pond, landfill,
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or lake, determine the mass loading of pollutants into the soil, which can
amount to reduction of one to two orders of magnitude when compared to
untreated materials.
4.7 DISPOSAL AND UTILIZATION ALTERNATIVES
Disposal alternatives being studied include assessment of the
environmental effects of disposal of treated and untreated wastes in mines
and oceans, as well in landfills and ponds. A data base is also being estab-
lished for the development of FGC waste divisional standards. Results from
these projects, as well as others described later in this section will be
reported as they become available.
Studies will also be conducted to determine dewatering char-
acteristics of FGC wastes in order to define areas where improvements can
be made in dewatering equipment or techniques. Results from this work will
be used in assessing potential benefits resulting from reduction of equipment
size, waste volume handled, disposal acerage, and chemical additives.
Utilization of FGC wastes can be considered as an alternative
to disposal. In this regard, the use of FGD •wastes in the manufacture of
21
fertilizer is being studied by TVA and at the Illinois Institute of Technology.
Experiments on forced oxidation of sulfite sludges to form gypsum for poten-
tial use in wallboard are being conducted, and the economics of the process
and a survey of potential markets are also being initiated. A project to use
FGD gypsum in cement manufacturing is expected to get under way shortly,
as is the evaluation of a process that uses FGD waste to produce elemental
sulfur. A conceptual design and cost study on beneficiation or alumina and
dicalcium silicate from FGC wastes is also being initiated.
The environmental effects of an alternative treatment and dis-
posal method wherein sulfite FGC wastes are oxidized to gypsum are in the
early stages of experimental assessment.
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4.8 POWER PLANT WATER RECYCLE AND REUSE
Chemical characterization of water streams from three plants
is being conducted and computer-assisted simulation of existing plant water
utilization operations will be made. Technical assessments will then be per-
formed of water recycle and reuse options formulated to minimize water re-
quirements and discharges. Cost estimates of each viable option will be
prepared. Pilot plant testing of one or more of the options will follow.
4.9 FULL-SCALE APPLICATIONS
Six utilities, with 13 power stations (5205 MW equivalent) have
been currently identified as committed to disposal of chemically treated FGC
wastes. Three power stations (767 MW) are in operation; startup by three
others (1413 MW) is planned by the end of 1976; and the remaining will begin
FGC treatment and disposal by 1979. The total quantity of untreated FGC
wastes being ponded in 1976 is 4338 MW equivalent.
In Japan, large-scale utilization in the wallboard and cement
industries of gypsum produced from FGD wastes is in progress. As dis-
cussed previously, experimental work and economic studies are being initi-
ated in the United States. A lime-based process that forms gypsum was
44
announced recently by Holter in West Germany.
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SECTION V
EPA-SPONSORED RESEARCH AND DEVELOPMENT
The U.S. Environmental Protection Agency (EPA) Program
for Control of Waste and Water Pollution from Flue Gas Cleaning (FGC)
Systems is designed to to evaluate, develop, demonstrate, and recommend
environmentally acceptable cost-effective techniques for disposal and utili-
zation of FGC wastes, with emphasis on flue gas desulfurization (FGD)
waste, and to evaluate and demonstrate systems for maximizing recycling
and reuse of power plant water. The program currently consists of 19
projects encompassing 6 major areas of interest: (1) environmental assess-
ment of FGC waste disposal and utilization processes including other power
plant effluents, (2) process technology assessment and new technology
development, (3) process economic studies, (4) alternative FGC waste dis-
posal methods development, (5) new FGC waste utilization methods develop-
ment, and (6) development of methods for improving overall power plant
water utilization.
The scope of the EPA FGC waste and water pollution control
program is depicted in Figure 1 (page 12 ). Projects concerning coal-pile
effluents, fly ash, water, and FGC waste (untreated, treated, and as
affected by scrubber operation) span the entire spectrum of the FGC waste
characterization and disposal assessment problems.
In this report, the specific projects are discussed separately
under their respective primary categories as indicated in Table 1 (page 10 ).
Additional information such as contractor or agency project director,
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EPA project director, duration, start date, and type of study are provided
in Table 2 (page 13).
5.1 ENVIRONMENTAL ASSESSMENT OF FGC
WASTE DISPOSAL
Seven environmental assessment projects are currently under
way. These include FGC waste characterization studies; laboratory and
pilot field studies of disposal techniques for chemically treated FGD sludges;
characterization studies of coal-pile drainage, coal ash, and other power
plant effluents; and studies of attenuation of FGC waste leachate by soils.
5.1.1 FGC Waste Characterization, Disposal Evaluation,
and Transfer of Waste Disposal Technology (The
Aerospace Corporation)
The Aerospace Corporation, El Segundo, California, is con-
ducting a broad-based ongoing study directed toward the determination of
environmentally sound disposal of solid and liquid wastes produced in FGD
processes. The desulfurization processes of interest in this program are
the lime, limestone, and double-alkali wet-scrubbing of flue gases produced
in the combustion of coal in steam power plants. More specifically, prob-
lems associated with FGD waste disposal are being defined, and assessments
will be made of the operational feasibility, performance, and costs of cur-
rent disposal methods. In addition, recommendations regarding alter-
native disposal methods based on the above findings are planned. Annual
reports will be issued, of which this is the first, in which FGC waste-
related research and development (R&D) activities sponsored or conducted
by EPA, Tennessee Valley Authority (TVA), and private industry will be
summarized and assessed. Periodic updates by means of papers presented
at industry meetings and symposiums are also planned;
The principal tasks of this program include (1) detailed
chemical and physical characterizations of desulfurization wastes and
process streams; (2) evaluation of the potentially toxic hazards associated
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with methods of disposal or utilization of desulfurization wastes;
(3) evaluation of chemical treatment or conditioning techniques needed to
achieve environmentally sound disposal; (4) identification and technical
evaluation of environmentally sound disposal methods and associated costs;
(5) identification of pertinent state and federal water quality and solid waste
disposal criteria and an interpretation of the impact of these criteria on the
disposal of desulfurization products; and (6) the planning and support of an
EPA FGD waste disposal field evaluation program. The later is reported
in Section 5. 1.2.
Results of tasks (1) through (5) are reported in References 4
and 5 and are summarized in the following paragraphs.
5.1.1.1 Chemical Characterization of Process Streams
The chemical characterization of process streams from seven
utility power plants encompassing a wide range of scrubber system capacity,
coal sources, and absorbent were analyzed (Table 5), and the effect of
processing variables on system chemistry was assessed.
The chemical characteristics were determined on the basis
of the following:
a. In-process variations in scrubber liquor composition
b. Variation in trace metal concentration in FGD waste
liquors with time
c. Effect of pH and ionic strength on concentration of
liquor constituents
d. Comparison of solute trace elements in FGD waste
liquors from limestone, lime, and double-alkali
scrubber systems
e. Determination of the trace metal relationship between
input materials (e.g., coal and absorbent) and output
(scrubber waste solids and liquor)
f. Distribution of trace metals released from coal by the
combustion process
g. Comparison of the trace metal content of eastern and
western coals and its effect on waste composition.
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Table 5. FGD SYSTEMS SAMPLED AS DATA BASE
Power Plant
TVA Shawnee
Steam Plant
TVA Shawnee
Steam Plant
Arizona Public
Service Company,
Cholla Power
Plant
Duquesne Light
Company,
Phillips Power
Station
General Motors
Corporation,
Chevrolet- Parma
Power Plant
Southern California
Edison, Mohave
Generating Station
Utah Power and
Light Company,
Gadsby Station .
Scrubber
System
Venturi and
spray tower,
prototype
Turbulent
contact
absorber,
prototype
Flooded-disk
scrubber,
wetted film
absorber
Single- and
dual -stage
venturi
Bubble -cap
tower
Turbulent
contact
absorber,
pilot plant
Venturi, and
mobile bed,
pilot plant
Scrubbing
Capacity,
MW (equiv)
10
•
10
120
410
32
< 1
< 1
Coal
Source
Eastern
Eastern
Western
Eastern
Eastern
Western
Western
Absorbent
Lime
Limestone
Limestone,
fly ash
Lime
Soda ash,
lime
Limestone
•
Soda ash,
lime
-36-
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5.1.1.1.1 In-Process Variations in Scrubber Liquor
Composition
A study was made of the changes occurring in the scrubber
liquor process streams, starting from the scrubber effluent to the final
filtering or dewatering step. Topics addressed in the evaluation of the
results included the following:
a. Systematic increases or decreases in the chemical
constituent concentration in the scrubber liquor
system circuit
b. Effect of the scrubber process, i.e., limestone,
lime, or double-alkali
c. The mechanism involved (synergistic change,
coprecipitation, or dissolution of constituents from
fly ash)
Data were compiled for all major, minor, and trace con-
stituent analyses for five scrubber systems, with the concentration deter-
mined for each constituent, beginning with the scrubber, through intermediate
process steps and to the final filtration or clarifying operation. These data
included the TVA Shawnee plant turbulent contact absorber (TCA) and the
venturi-spray tower systems, the General Motors (GM) Parma, Duquesne
Phillips, and Southern California Edison (SCE) Mohave systems.
The overall end-to-end changes in the concentration of each
constituent were determined and are summarized in Table 6. On the basis
of individual chemical constituents only potassium shows a consistent
increase in concentration, while aluminum, iron, silicon, silver, chloride,
and sulfite showed a decrease. The remainder were unchanged or responded
in a manner too subtle to be clearly discernible as they passed through the
process circuit. In the lime and limestone processes, the total dissolved
solids (TDS) decreased, and the system pH increased from the scrubber to
the point of disposal.
On the whole, many elements appear to be removed in the
scrubber bleed system by coprecipitation or scavenging; probably by the
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Table 6. NET CHANGE IN SCRUBBER LIQUOR COMPOSITION OF MAJOR, MINOR, AND TRACE
CONSTITUENTS BETWEEN INITIAL AND FINAL STAGES IN SCRUBBER SYSTEM
00
Constituent
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Zinc (Zn)
Chloride (Cl)
Fluoride (F)
Sulfate (SO4)
Sulfite (S03)
TDS
pH
Limestone*
Increase
X
XX
XX
XX
X
XXX
XX
X
XX
xxxx
Decrease
XXX
X
X
XX
X
xxxx
X
X
X
XX
X
XX
X
X
XXX
xxxx
xxxx
xxxx
No Signifi-
cant Change
« 20%)
XXX
XXX
XXX
XX
XXX
X
XX
XX
xxxx
X
X
xxxx
r • a
Lime
Increase
X
X
x •
XX
XX
XXXX
Decrease
XX
X
XXX
X
XX
XX
XX
XXX
X
X
X
X
XXX
XX
XXX
XX
XX
XXX
XX
No Signifi-
cant Change
(< 20%)
X
XX
X
xxxx
XX
XX
XX
XX
xxxx
XX
XXX
X
XXX
X
XXX
X
XX
XX
XJC
X
Double Alkali"
Increase
X
X
X
X
X
Decrease
X
X
X
No Signifi-
cant Change
« 20%)
X
X
X
X
X
X
X
X
X
Each "X" represents a separate sample set.
-------
formation and growth of the sulfate phase resulting from the rapid oxidation
of the bisulfite ion. Most of the remaining constituents are unchanged in
concentration as they pass through the circuit. Except for the increase in
potassium, which is attributed to leaching of fly ash, the concentration of
major, minor, and trace constituents in the scrubber liquors tends to
decrease along the process circuit.
Chloride ion content is seen as a system variant for all three
scrubbing processes, possibly as a consequence of system pH levels. The
changes in calcium, sodium, and sulfate concentration in the double-alkali
systems are attributed to inherent in-process chemistry.
5.1.1.1.2 Variation in FGD Waste Liquor Composition
with Time
To determine if constituents of FGD waste liquors undergo
any significant changes in concentration during extended periods of operating
time, analyses were made of major and trace constituent levels in the dis-
posal liquor of each set of samples as a function of sampling date. The
scrubbing systems selected for this evaluation were those for which multiple
sample sets had been analyzed over time periods ranging from 4 to 16
months. These systems were the TVA Shawnee TCA, TVA Shawnee venturi-
spray tower, Duquesne Phillips venturi, and the Arizona Public Service
Cholla Venturi-absorption tower. In addition, two sample sets were taken
that included a sampling shortly after startup of the Shawnee lime process
and the Shawnee limestone process.
For the lime process, the first sample set was taken on the
third day after startup and the second one was taken about two months later.
The other scrubber system sampled during the startup period was the
Shawnee limestone process. It was first sampled about six weeks after an
intermittent period of operation in an open-loop mode. A second sample set
was taken approximately five months later.
On the basis of the sampling rates described for the four
power plants evaluated, it appears that a rapid buildup in the concentration
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of major species takes place and reaches relatively stable conditions at a
concentration where the rate of constituent loss in the waste product equals
the rate in which that constituent is scrubbed from the flue gas.
After an initial buildup period after startup, the trace
elements, except for lead, exhibit no systematic time-related trend in con-
centration level for the trace constituents of the liquor. Since trace element
concentrations did not change systematically with time nor with changes in
major species concentration the controlling factor other than saturation
chemistry was postulated.
The variation in concentration of a given element from one
set of samples to the next was ascribed principally (lead, possibly, being
an exception) to the effects of differences in input materials, (fuel absorbed
and process water), to operating conditions, and in the case of very low-
concentration-level trace metals, to low analytical precision. It should be
noted that in some cases where TDS increased because of an increase in
sulfate content, the trace elements decreased, but when the TDS increase
was caused by chloride ion increase, the trace elements increased. This
behavior may suggest that sulfate ion may be exercising some influence on
the content of trace elements. Insufficient data are available to provide
confirmation of this observation.
For lead, there may be a direct relationship between concen-
tration and time. The buildup of lead implies that a saturation concentration
was not reached or that fluctuations in input ingredients were small relative
to the concentration in the liquors.
5.1.1.1.3 Effect of pH and Ionic Strength on Concentration
of Liquor Constituents
In the evaluation of the chemical analyses discussed pre-
viously, a general decrease in trace element content as pH increased was
noted. Also, it was observed that TDS (and therefore ionic strength)
increased for the duration that the scrubber was operated.
-40-
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In most scrubber systems, a pH is used as a system control
parameter. When data from all the systems were evaluated as a function
of pH on a system-by-system basis, no correlation was evident. The con-
clusion is drawn that trace element concentration of the scrubber liquors
within a specific system is not controlled by either system pH or the ionic
strength of the liquor. This is in agreement with the results of observations
which ascribe trace element concentrations in system liquors to the varia-
tions in trace element content of process ingredients and to major system
design variables. It is not apparent in any of these analyses that a level of
soluble saturation may have been reached by any of the trace elements rela-
tive to the major species chemistry.
5.1.1.1.4 Comparison of Solute Trace Elements in FGD
Waste Liquors from Limestone, Lime, and
Double-Alkali Scrubber Systems
Overall concentration levels of solute trace elements in
scrubber liquors using the limestone, lime, and double-alkali processes
were evaluated to determine if any appreciable differences existed for the
three processes. The results reported showed that, in nearly every case,
the trace metals concentrations (As, Be, Cd, Cr, Cu, Hg, Pb, Se, and Zn)
are higher in the limestone system and lower in the double-alkali system
relative to the lime system. Although there is a range of concentrations and
some overlap in the range of trace element concentrations between power
plants using different scrubber chemistries, concentration trends were in the
order given, with limestone system concentration worst cases being from
one to ten times higher and the lime values and double-alkali worst cases
being lower by a factor of one to four. The only obvious system parameter
that can account for this order of trace metals is scrubber pH, which is
lowest in the limestone systems and highest in the double-alkali system.
This basis of comparing scrubbing systems tends to support
the conclusion that the determining factors in trace metal levels in liquors
are primarily associated with system variables, the amounts entering the
-41-
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system from all sources. System chemistry, in particular pH, has a
discernible influence. The effect of other system variables, such as
residence time in the circuit and system efficiency as determined by
mechanical design, which may contribute to a lesser degree to the concen-
tration of the solute trace metals has not been quantified.
5.1.1.1.5 Determination of the Trace Metal Relationship
Between Input Materials (coal and absorbent)
and Output (scrubber sludge and liquor)
The relationship between the observed concentration range
of trace metals in coal (corrected for absorbent by inclusion as an equiva-
lent coal content) and in sludge solids is shown in Figure 4. Similarly,
Figure 5 illustrates a relationship between the concentrations in sludge
liquors and the coal, with the bandwidth being nearly two orders of magni-
tude. The trace metal concentration in the liquor is approximately two
orders of magnitude less than that for the solids, and some of the uncer-
tainty associated with precision at lower concentrations may be reflected
in the data scatter. There is no evidence in these results to indicate that
trace element concentration is controlled by solubility limitations.
Furthermore, the trace metal content in FGD waste liquors
has already been reported to be affected by scrubber pH. If the trace metal
content for the sludge liquor were corrected for the differences in pH, a
further reduction in data scatter would be expected.
In summary, the trace element content of FGD waste solids
and liquors appears to be a function of the trace element content in the
process ingredients, particularly coal. Data scatter may be a result of the
differing amounts of fly ash in the wastes and the scrubbing efficiency rela-
tive to each element. Scatter in the liquor data slo is expected because
the pH of the system liquor has been shown to influence the concentration
of trace metals in the liquors when one system is compared with another.
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100
CO
o
=i 10
o
CO
CO
o
I
I—
LU
O
O
o
0.1
0
'
TRACE METALS ANALYZED:
As, Be, Cd, Cr, Cu, Hg, Pb, Se, In
0.1
POWER PLANTS: TVA SHAWNEE (lime and limestone)
DUQUESNE PHILLIPS
ARIZONA CHOLLA
i i i i 1 1 1 1 I I i I I 1 1 1 1 i I I I i 1 1 1 1
1.0 10 . 100
CONCENTRATION IN COAL, ppm
Figure 4. Relationship between trace metal content in
coal and FGD waste solids
-43-
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100 r-
10
o
o 1
CO
O
o
0.1
<
CCL
0.01
0.1.
TRACE METALS ANALYZED:
As,Be,Cd,Cr,Cu,Hg,Pb,Se,Zn
0.001liliiiii—1
POWER PLANTS:
TVA SHAWNEE
GM PARMA
DUQUESNE PHILLIPS
ARIZONA CHOLLA
1.0
CONCENTRATION
10
COAL, ppm
100
Figure 5. Relationship between trace metal content in
coal and FGD waste liquors
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5.1.1.1.6 Distribution of Trace Metals Released from
Coal by the Combustion Process
In the previous paragraph a correlation was presented that
showed the concentration of trace elements in the sludge to be approximately
the same as the concentration in the coal. The bandwidth of the data scatter
for solids is about one order of magnitude, and the range of fly ash content
in the FGC wastes also was reported as about one order of magnitude.
Moreover, in evaluating the data bandwidth in Section 5.1.1.1.5, it was
reported that wastes with high fly ash content tended to lie on the high side
of the data band and that data from low fly ash wastes is more prevalent on
the low side of the data band.
The results of this study are consistent with the trace metal
distribution studies found in the literature and show that the major
source of trace metals found in the waste is in the fly ash. Two exceptions
are mercury and selenium, which are not found in the fly ash at relative
concentrations equivalent to the other trace metals. Both are found pri-
marily in the flue gas stream as vapors or ultrafine particulates (< 0. 1 |j.m).
However, their relative concentrations in the waste are nearly equivalent
to the other trace elements, which infers that some removal from the flue
gas occurs. In Section 5.1.1.1.5, it was noted that a small fraction of the
trace metals is in the waste liquor, i.e., approximately 1/100 of the con-
centration that is in the solids. It is postulated that most of these metals
originate by leaching from the fly ash during the more acid cycle of the
scrubbing operation.
5.1.1.1.7 Comparison of Trace Metal Content from Eastern
and Western Coals and Their Effect on Waste
Composition
The correlation between trace metals in sludge and coal
demonstrated in Section 5. 1. 1. 1.6 suggests that the trace metal content
expected in eastern and western scrubbing liquors may differ as a conse-
quence of differences in trace metal content of the coals.
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When comparing the coal analyses of this study with other
sources, it is seen that, with few exceptions, the range of measured
values falls within the reported range for each element. These data show
that measured values from western coal for arsenic, cadmium, mercury
and zinc are lower than the measured values from eastern coals; on the
other hand, western coal had high values of copper. These high values may be
explained by the proximity of the coal fields studied in this report to a major
copper-producing region. No other elements showed significant differences
between regions.
5.1.1.2 Leaching Characteristics of Untreated FGD Wastes
A pollution potential may exist as a consequence of the action
of rainwater leaching through FGD wastes in an unlined disposal basin. If
free-standing water is allowed on the surface, some will permeate through
the waste. The amount of water permeating through the waste depends upon
the permeability of the waste, the permeability of the subsoil, and the
amount of standing resulting from rainfall or from separation from the
solids. The quality of the leachate depends on the amount of constituents
absorbed in the permeation process.
FGD solid waste normally contains occluded liquor from the
scrubbing process representing 35 to 80 percent by weight of the total waste,
depending upon the extent of dewatering. Water permeation through the
solids flushes most of this occluded liquor within the first three pore volume
displacements. Thereafter, the quality of leachate is dependent upon the
solubility of the waste solids.
Two sets of leaching experiments were conducted. In the
first set, three laboratory columns were packed with wastes obtained from
the TVA Shawnee limestone, the Arizona Cholla limestone, the Duquesne
Phillips lime, the GM Parma double alkali, and the SCE Mohave limestone
processes. Leaching water (unbuffered) adjusted to pH 4, 7, and 9, with
either HC1 or NaOH, was used in each set of columns. The leaching water
and the leachate were allowed to react with air so as to stimulate aerobic
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conditions. A second set of leaching experiments were conducted under
anaerobic conditions. These experiments duplicated the first experiments
except that the leaching water and leachate were protected from interaction
with the atmosphere and leaching water with a pH 7 was used because no
discernible effect was noted between the aerobic columns as a result of
differences in the initial pH of the leaching waters.
Whether leaching conditions are aerobic or anaerobic depends
upon the sludge and site conditions. Aerobic leaching water can result from
supernate equilibrium with the atmosphere; however, subsequent percolation
through a sulfite sludge can create an anaerobic condition in the leaching
water. The resultant leachate can remain anaerobic in the subsoil; however,
if the soil is plugged by filtering of fine and colloidal particles from the
sludge and penetration through this filter zone is slower than permeation
through the soil, the opportunity exists for the creation of air voids in the
soil. In this case, the leachate may become aerobic. In field conditions,
all four combinations of aerobic and anaerobic leaching water and leachate
are possible.
In both experimental sets, analyses were performed for As,
Be, Cd, Cr, Cu, Pb, Hg, Se, Zn, Cl, F, SO^, SO , pH, and TDS as a
function of the leachate volume passing through the column.
The detailed results of the leaching experiments are pre-
sented in Reference 5. Typical characteristics from the aerobic experiments
are shown in Figure 6, which illustrates the effect of leaching through
Shawnee limestone waste. For the aerobic test results, a single curve is
presented for each species representing the median value of concentration
from the three values of pH for leaching water used on each waste type.
The curves shown are normalized to the concentration of the first pore
volume, which essentially reflects the concentration of the mother liquor.
A typical result of the anaerobic leaching experiments is
presented in Figure 7. From an overall assessment of the leaching data, it
was concluded that for each of the major species represented by sulfate,
-47-
-------
1.0
UJ
Qi
O
Q_
H 0.1
o
on
o
0.01
o
i—
<
UJ
O
O
O
0.001
2
LITERS
10
20 30 40
PORE VOLUME DISPLACEMENTS
50
Figure 6. Leachate analyses from TV A Shawnee untreated
limestone waste: aerobic conditions
-48-
-------
1.0
OS
O
Q_
00
!? 0.1
o
o:
0.01
o
o
o
0.001
6
LITERS
I
10
10 20 30 40 50
PORE VOLUME DISPLACEMENTS
60
70
Cl
80
Figure 7. Leachate analyses from TVA Shawnee untreated
limestone waste: anaerobic conditions
-49-
-------
chloride, and TDS, the concentrations decrease rapidly during the first few
pore volumes, and in most cases 90 percent of the decrease in concentration
of the leachate between the 1st and 50th pore volume occurred at the com-
pletion of the 3rd pore volume displacement. When a similar comparison
was attempted for trace metals, it was noted that for some elements the
transition period from pore flushing to solids dissolution generally extended
over a greater range of pore volume displacements than that for major con-
stituents. This behavior may be caused by the presence of these elements
in trace amounts, which would result in a reduced flushing action from a
given volume of water, or the observed behavior may only be the result of
greater uncertainty in the analytical data because of the low trace metal
concentration.
When comparing aerobic and anaerobic leaching, it appears
that a greater drop in concentration of major constituents occurs in the
anaerobic leaching condition than in the aerobic conditions. Moreover, when
compared with the mother liquor, the concentration of major species in the
50th pore volume is consistently less for anaerobic leaching conditions than
for aerobic conditions. When the same comparison is attempted for the
trace metals, no lear trend was reported except for lead. In every case,
lead concentration in the 50th pore volume was significantly higher when
leached under anaerobic conditions.
When the leaching effect on major species was assessed,
certain generalities were made. The sulfate ion concentration in the aerobic
columns, after 50 pore volume displacements reached a constant value
between 1100 and 1300 m.g/1, and was independent of the concentration of the
mother liquor. Sulfate ion concentration in the 50th pore volume in the
anaerobic columns showed a consistent 20 percent lower value that ranged
between 900 and 1100 mg/JL. In the 50th pore volume, the chloride concen-
tration was found to have stabilized between 95 and 130 rag/i. in the aerobic
columns and about one-half of that value in the anaerobic columns.
-50-
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5.1.1.3 Leaching of Chemically Treated Waste
Leaching experiments were also conducted with treated FGD
wastes under both aerobic and anaerobic conditions. Generally the aerobic
and anaerobic leaching conditions were similar to those for the untreated
wastes. However, the chemically treated sludge was dried and pulverized
before packing into the leaching column so that the maximum surface contact
area was available for the flow of water through the treated sludge.
The results of leaching experiments for various processes
and power plant sites are given in Reference 5. Typical aerobic and
anaerobic results for one chemical treatment process for Shawnee lime stone
wastes are shown in Figures 8 and 9.
The results reveal leaching profiles (as a function of pore
volume) similar to those observed in the leaching of untreated FGD waste.
In most cases, the decrease in concentration of chemical species in the
leachate takes place within the first few pore volume displacements. How-
ever, contrary to untreated FGD waste leaching experience, the rate of
decrease in concentration of some of the major chemical species was more
gradual. In the leaching of untreated waste, a greater rate of decrease in
concentration was observed in leaching under anaerobic condition. In
assessing the results obtained from the leaching of wastes treated by either
the Chemfix, Dravo, or IUCS processes, it was concluded that the type of
conditions, i.e. , aerobic vs anaerobic, would not be a significant factor in
the selection of a particular chemical treatment process.
Chemical treatment generally improves leachate quality, de-
pendent almost completely on the specific waste and the specific chemical
process used. The concentration of the major chemical species in the
leachate from the chemically treated waste are approximately 1/4 to 1/2
the concentration in the leachate from untreated waste.-
When the results are examined for effect on trace metals, it
is not apparent that chemical treatment of FGD waste improves the leachate
quality. In those cases in which high initial concentration of trace metals
-51-
-------
1.0
LU
C£
O
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UJ
UJ
oe.
0.1
o.oi
o
I—
<
u
o
o
0
0
LITERS
10 20 30 40 50
PORE VOLUME DISPLACEMENTS
60
70
Figure 8. Leachate analyses from TVA Shawnee treated
limestone waste (Chemfix): aerobic conditions
-52-
-------
1.0
UJ
C£.
O
Q_
CO
0.1
O
o
<
I—
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O
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0.01
0.001
10
LITERS
I
10 20 30 40 50 60
PORE VOLUME DISPLACEMENTS
70
80
Figure 9. Leachate analyses from TVA Shawnee treated
limestone waste (Chemfix): anaerobic conditions
-53-
-------
appeared in the leachate of untreated waste, similar concentrations were
measured when the sludge was chemically treated. This response was
similar under aerobic and anaerobic leaching conditions. This may be
partially explained that in some cases there is evidence to suggest the chemi-
cal additives used in the fixation process are contributing trace metals to the
leachate.
In summary, chemical treatment by the methods evaluated in
this study do not tend to reduce leachate concentrations of trace elements,
but do reduce concentrations of the major species by a factor of two to four
relative to untreated wastes. However, other effects resulting from chemical
treatment, such as reduced permeability and superior disposal placement
techniques, are considered significant in reducing the release rate of all the
constituents to the soil beneath the treated waste.
5.1.1.4 Physical Properties
The disposal, handling, and transportation techniques for
FGD wastes will be strongly influenced by the physical behavior of these
wastes and the resultant costs. The applicability of some of these techniques
may be limited or restricted by physical properties of FGD wastes in the
particular state in which they are produced, i. e. , degree of water content,
crystalline phase composition, and particle size and distribution. Experi-
mental tests were conducted to characterize the FGD wastes of seven power
plant scrubbing facilities, which include pilot, prototype, and full-scale units
ranging from 1- to 410-MW equivalent capacities. In each case, the FGD
waste studied was the waste material for each facility and received in its
normal state of disposal. The testing was directed toward the application of
the results in landfilling and land reclamation situations.
The physical parameters investigated included specific gravity
and bulk density as a function of solids content, water retention as a function
or dewatering techniques, viscosity of slurries at various solids.contents,
permeability as a function of particle packing, and compactibility and uncon-
fined compressive strength as a function of solids content.
-54-
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5.1.1.4.1 Solids Characterization
The physical properties of any liquid-solid mixture are
dependent upon the characteristics of both the liquid and the solid con-
stituents as well as the interaction between them. The FGD wastes contain
four principal crystalline phases: calcium sulfite, calcium sulfate, fly ash,
and unreacted limestone or precipitated calcium carbonate. These solid
phases exist as fine particulates suspended in an aqueous liquor which is
usually saturated with ions of these solids. In addition, sodium chloride
or calcium chloride is also present as a dissolved salt.
The relative amounts of each of the solid crystalline phases
are dependent upon many system design parameters and include (1) the sulfur
content of the coal and the efficiency of scrubbing SO_, (2) the fly ash in the
flue gas entering the scrubber and the fly ash removal efficiency of the
system, (3) the stoichiometric ratio of reactants added relative to the sulfur
content and the reactant utilization efficiency, and (4) the amount of oxidation
of the sulfur products that takes place in the system. In addition, each
crystalline phase and the characteristic of each phase will have some influence
on the behavior of the waste.
5.1.1.4.2 X-Ray Diffraction Characterization
The objective for the use of x-ray diffraction techniques to
examine power plant FGD wastes was to provide quantitative characterization
of the crystalline phases in the solid waste. The study indicated that although
this method was not suitable for quantitative analyses, it permitted a determi-
nation of the relative concentrations of the major constituents within a given
waste.
The results of the x-ray study showed that in most cases
several calcium sulfate-sulfite phases were present, in addition to the ex-
pected phases of gypsum and calcium sulfite hemihydrate.
-55-
-------
The Shawnee limestone waste showed strong gypsum peaks,
as expected, but there was also evidence of a second calcium sulfate dihydrate
that appeared as a weak phase in at least two samples. This second phase is
a relatively newly discovered phase which, while having many crystallographic
similarities to gypsum, it is nevertheless a unique phase, and the consequences
of its presence is unknown at present. The calcium sulfite hemihydrate in all
cases was the second most prominent phase in the x-ray patterns, appearing
as a moderately strong phase. In addition, a calcium thiosulfate hydrate
phase appeared as a weak phase, and residual limestone (calcite) appeared
also as a weak phase in all samples. The other samples are discussed in
detail in Reference 5.
In summary, the x-ray diffraction characterization, while not
providing quantitative data, provides insights that are helpful in identifying
phases in the waste that could not otherwise be determined and, further, pro-
vides semiquantitative data relative to the amount of the phases present.
5.1.1.4.3 Solids Composition
The composition of the solids fraction of each of the wastes
sampled was determined by chemical means and is presented in Table 7.
The analytical techniques used are described in Reference 5. The wide range
in composition for each of the major solid constituents reflects the various
design differences that exist among scrubber systems. Systems having high-
efficiency fly ash collection facilities upstream of the scrubber are con-
trasted sharply with those systems having less efficient collection methods.
The calcium sulfate content of the sludge reflects in each case the capability
of the calcium sulfite to be oxidized, this reaction usually occuring in the
scrubber or reaction tank.
5.1.1.4.4 Crystalline Structure
A portion of waste solids from each scrubber facility was
selected for subsequent examination on the scanning electron microscope
(SEM), from the materials prepared for x-ray characterization. A series
-56-
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Table 7. PHASE COMPOSITION OF FGD WASTE SOLIDS IN WEIGHT PERCENT3"
Atomic
Formula
CaSO4'2H2O
CaSCy 1/2H2O
CaSO4- 1/2H2O
CaCO3
MgSO4'6H2O
CaS2O3-6H2Oa
Na2SO4'7H2O
NaCl
CaSO4a
CaS3010a
Fly Ash
Total
TVA Shawnee
Limestone,
2/1/73
21.9
18.5
38.7
4.6
20.1
103.8
TVA Shawnee
Limestone,
7/12/73
15.4
21.4
20.2
3.7
40.9
101.6
TVA Shawnee
Limestone,
6/15/74
31.2
21.8
4.5
1.9
40. 1
99.5
TVA Shawnee
Lime,
3/19/74
6.3
48.8
2.5
1.9
40.5
100.0
SCE Mohave
Limestone,
3/30/73
84.6
8.0
6.3
1. 5
3.0
103.4
GM Parma
Double Alkali,
7/17/74
48.3
12.9
19.2
7.7
6.9
7.4
101.4
APS Cholla
Limestone,
4/1/74
17.3
10.8
2. 5
14.3
58.7
103.6
DLC Phillips
Lime,
6/17/74
19.0
12.9
0.2
9.8
59.7
101.3
UPL Gads by
Double Alkali,
8/9/74
63.8
0.2
10.8
17.7
8.6
101. 1
I
Ul
Phases not explicitly measured; presence deduced from x-ray study.
-------
of photomicrographs were taken of each sample to assist in interpreting
the results of the various other chemical and physical characterization tests.
A typical example of the crystalline structure of the solids content is shown
in Figure 10, which shows a distribution of particles representing the solids
content of the TVA Shawnee TCA system sludge using limestone absorbent.
The waste is characterized by large platelets of calcium sulfite hemihydrate
and spherical fly ash particles. A broad range of particle sizes exists for
both phases, with fly ash particles in the range of 0. 1- to 50-(j.m diameter.
The calcium sulfite phase is present as stacks of platelets with edge dimen-
sions as large as 20 to 50 |im for the largest particles and platelet thickness
of approximately 0. 1 to 0. 5 (am. In addition to these two phases, large
particles of residual limestone and blocky sulfate particles are occasionally
seen, but these are seldom greater than 5 fim in the longest dimension.
5.1.1.4.5 Viscosity
The viscosity of the liquid waste is a direct measure of its
pumpability, which affects both the cost of transporting it as well as the
system design. Waste materials produced in FGD systems contain finely
divided particulate materials suspended in an aqueous medium. Sulfur waste
products (both sulfate and sulfite) tend to have particle sizes in the same
range as fly ash, between 1 and 100 (Jim. Although fly ash is produced in
spheres, sulfite wastes are platey and sulfates are blocky in shape. Un-
reacted limestone (or lime) is usually present in the waste and contributes
an additional shape parameter. The particle shape, particularly the platey
sulfite, has been credited for the thixotropic nature observed in FGD wastes.
Fly ash when present in FGD wastes can provide a marked measure of fluidity
that the sludge would not otherwise have.
The viscosity of FGD waste from seven power plants as a
function of solids content is presented in Figure 11. The results show that
among the sludge tested, pumpable mixtures (< 20 poise) range from a high
solids'content of. 70 percent for the Cholla sample to a low solids content of
-58-
-------
Figure 10. TVA Shawnee Limestone
clarifier underflow
crystal structure (3000X)
-59-
-------
•CURVE
SOURCE
DATE FLY ASH, %
ARIZONA CHOLLA LIMESTONE
SCE MOHAVE LIMESTONE
TVA SriAWNtE LIMESTONE
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
DUQUESN.I; PHILLIPS LIME
TVA SHAWNEE LIME
UTAH GADSBY DOUBLE ALKALI
GM PARMA DOUBLE ALKALI
4/1/74
3/30/73
7/11/73
6/15/74
2/1/73
6/17/74
3/19/74 '
8/9/74
7/18/74
58.7
3.0
40.9
40.1
20.1
59.7
40.5
8.6
7.4
120
100
80
—
o
Q.
>£ 60
GO
o
o
GO
40
20
i i i i i i i i
i i
70
60 50 40
SOLIDS CONTENT. WEIGHT %
30
Figure 11. Viscosity of FGD wastes
-60-
-------
32 percent for both the Utah Gadsby and GM Parma samples; a total range
of 38 percent solids content. Considering this wide spread, the importance
of experimentally determined data for system design parameters is apparent.
The slope of the viscosity curves as a function of solids
content lie in two groups: The lower slope group includes all wastes from
the TVA Shawnee and the Utah Gadsby facilities; the higher slope group in-
cludes the other wastes. Presently, no parameter or set of parameters has
been identified to determine responsibility for this behavior.
Thus far, the results of the tests suggest that fly ash decreases
the viscosity of FGD wastes. Particle shape, size, and distribution may
influence viscosity, but the effect is indeterminant at present.
5.1.1.4.6 Wet Bulk Densities
The ability of a sludge to be dewatered is a function of many
variables; the size and distribution of particles, and the crystalline structure
of the particles and the method used. Primarily dewatering by clarifiers or
thickeners separate water from a slurry, principally through the action of
gravitational forces. The secondary methods of dewatering are typically
vacuum filtration and centrifugation. In some cases, natural settling may be
considered a cost-effective method. Dewatering of power plant FGD waste
may be advantageous on the basis of over all disposal costs as well as environ-
mental considerations.
The effectiveness of a dewatering operation is best measured
by the relative quantity of water that remains with the solid after performing
the dewatering operation. The wet bulk density of a sludge, as reported, is
the weight of a unit volume of dewatered sludge containing both liquid and
solid phases.
The wet bulk density was determined on eight FGD waste
samples after each was dewatered by settling, settling" with free drainage,
vacuum filtration, and centrifugation (Table 8). A typical set of results is
plotted in Figure 12. Data from the laboratory tests indicate that for a major
portion of the wastes tested highest density is obtained using vacuum-assisted
-------
Table 8. DEWATERED BULK DENSITIES
OF FGD WASTES
Sample
Source
and
Date
Shawnee
Limestone,
2/1/73
Shawnee
Limestone,
6/15/74
Shawnee
Lime,
3/19/74
GM
Double Alkali,
7/18/74
Utah
Double Alkali,
8/9/74
Duquesne
Lime,
6/17/74
Cholla
Limestone,
9/1/74
Mohave
Lime stone,
3/30/73
Dewatering Method
Settled
Percent
Solids
49.0
52.9
41.5
40.0
37.2
47.6
46.7
66.6
Density,
g/cc
1.45
1.46
1.34
1.31
1.30
1.40
1.39
1.65
Settled and
Drained
Percent
Solids
55.7
58.3
43.4
43.9
41.4
53. 1
50.9
67.2
Density,
g/cc
1.51
1.53
1.36
1.35
1.33
1.48
1.44
1.67
Centrifuge
Percent
Solids
59.8
63.3
49.9
50.9
62.2
57.2
60.9
77.0
Density,
g/cc
1.56
1.60
1.44
1.43
1.62
1.52
1.58
1.86
Filter
Percent
Solids
65.0
65.9
56.0
57.8
54.6
57.0
53.4
*
80.3
Density,
g/cc
1.65
1.64
1.51
1.52.
1. 50
1.52
1.48
1.78.
-62-
-------
1.7
1.6
1.5
to
LU
OQ
1.3
1.2
1.1
1.0
TVA SHAWNEE LIMESTONE
JUNE 15, 1974
H- FILTERED
CENTRIFUGED
0
20 40 60 80
SOLIDS CONTENT. %
Figure 12. Wet bulk density of FGD waste sample
-63-
-------
filtration and in the remaining centrifugation produces the most dense
material. These data reveal that the sludges with the best overall dewatering
characteristics; the TVA Shawnee limestone, the SCE Mohave, and the
Duquesne Phillips sludges, are those with the coarsest particle size distri-
butions. Conversely, the double-alkali systems which produce the finest
particle size distributions are those that dewater least efficiently. Although
the overall most effective method of dewatering was by vacuum assisted fil-
tration, the tests were conducted with laboratory equipment and the results
may not be representative of what may be expected when using commercial
equipment.
5.1.1.4.7 Coefficient of Permeability
Since the permeability of FGD waste is a significant factor
affecting the seepage of leachate through the waste and the pollution potential
of a waste disposal site, the coefficient of permeability of each of the un-
treated FGD sludges and treated sludges was measured. The permeability
of sludge from seven separate scrubbing facilities was determined by passing
deionized water through columns containing scrubber waste.
Prior to permeation measurements, the particle packing
density was determined from the weight of the charge and the height of the
packed column. The pore volume, which is used as a descriptive character-
istic, is defined as one minus the solids volume fraction. Untreated waste
was compacted after the initial permeation measurement. After a new particle
packing density and pore volume were determined, the permeation rate was
than measured. The results are tabulated in Table 9 and plotted in Figure 13.
Preparation of chemically treated samples included crushing
and pulverizing the fixed material after drying and packing the powder into
a column. Although this technique may not apply directly to treated sludge
placed and undisturbed at a disposal site, it simulates "the maximum sludge
that is moved and/or disturbed in a disposal site after placing and curing.
Additionally, permeability of undisturbed fixed sludges was determined.
-64-
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Table 9. PERMEABILITY OF UNTREATED AND CHEMICALLY
FIXED FGC WASTES
Sample
Source
Shawnee
Limestone
Shawnee
Lime
Mohave
Dusquesne
GM
Double Alkali
Cholla
Utah
Double Alkali
Shawnee
Limestone
(IUCS)
Shawnee
Limestone
(IUCS)
Mohave
(IUCS)
Shawnee
Lime
(IUCS)
Shawnee
Limestone
( Chemf ix)
Shawne e
(Dravo)
Duquesne
(Calcilox)
Sample
Date
2/1/73
6/15/74
6/15/74
6/15/74
6/15/74
3/19/74
3/19/74
3/19/74
3/30/73
3/30/73
3/30/73
6/17/74
6/17/74
6/17/74
7/18/74
7/18/74
7/18/74
4/1/74
4/1/74
4/1/74
8/9/74
8/9/74
8/9/74
5/29/75
6/12/75
2/27/75
6/12/75
Replications
1
3
1
3
3
1
1
(2)
(3)
3
3
(2)
3
2
(2)
1
1
(2)
1
1
1
1
(2)
(2)
(5)
(2)
1
1
1
1
(2)
1
1
1
1
(2)
1
1
Fractional
Void
Volume
0.69
0.60
0.58
0.58.
0.55
0.75
0.74
0.72
0.47
0.43
0.34
0.68
0.58
0.49
0.71
0.69
0.65
0. 56
0.54
0.54
0.75
0.73
0.70
0.69
0.54
0.55
0.65
0.53
0.57
-
0.68
0.72
0.70
0.78
0.75
0.70
0.78
0.76
Permeability
Coefficient,
cm'/sec
2.3xlO'4
1.0 x 10 5
9.6 x 10~j?
8.5x ID'*
5.9x 10 3
1.7X 10"!
5.3 x 10'^
6.0 x 10"3
5.0 x 10'4
7.5x 10'*
1.6 x 10'*
l.Zx 15'4
1.3x 10'*
7.4 x 10'
8.2x10'*
2.5x lO'l
8.1 x 10~3
2.7 x lO'l
1.8 x lO'l
1.1 X 10'b
9.8 x lO'l
1.3x ID'*
1.2 x 10"*
2.2 x 10~4
5.5 x 10'8
7.9 x 10".
7.3 x 10'*
1.9 X 10"*
5.5 x 10'5.
5.5 x 10"
4.1 x 10"5
1.5-2.1 x 10
4.7 x ID'5
3.2 x 10"!
6.9 x 10'5
3.8x 10'4
4.9 X 10"]:
2. 1 x 10
Remarks
Column packed as slurry
Compacted wet
Compacted wet
Column packed -as slurry
Compacted wet
Compacted wet
Compacted wet
Pulverized
,
Solid, undisturbed
Pulverized
Pulverized
Pulverized, compacted wet
Solid, undisturbed
Solid, undisturbed
Pulverized .
Solid, undisturbed
Pulverized
Pulverized
Solid, undisturbed
Pulverized
Pulverized
Pulverized, compacted wet
Replications of those in parenthesis refer to multiple measurements on a single column using varying
hydraulic heads.
-65-
-------
10
-3
1 0
o
if
10
-4
LU
a.
10
-5
0.20
POND
E
5xlO"7 A5.5xlO"8
L t 4 I
FOR POND DESCRIPTIONS
SEE SECTION 5.1.2.1
SOURCE
• TV A SHAWNEE LIMESTONE
o TV A SHAWNEE LIME
a SCEMOHAVE
LIMESTONE
• GM PARMA DOUBLE ALKALI
T UTAH GADSBY DOUBLE ALKALI
v DUQUESNE PHILLIPS LIME
A ARIZONA CHOLLA LIMESTONE
X CHEMFIX LAB A |UCS LAB
0 DRAVOLAB ,
DATE
6/15/74
3/15/74
3/30/73
7/18/74
8/9/74
6/17/74
4/1/74
0.30
0.40 0.50
VOLUME FRACTION OF SOLIDS
0.60
0.70
Figure 13. Permeability of untreated and treated FGD wastes
-------
The data presented in Figure 13 illustrate that the
permeability coefficient of untreated wastes generally falls in the range of
-4 - 5
2 X 10 to 1 X 10 cm/sec. (Data published by the U.S. Army Waterways
Experiment Station (WES) indicate the permeability of similar untreated
-5 -5 1Z
wastes to be in the range of 8 X 10 to 1 X 10 cm/sec. ) For the
crushed treated waste, a range comparable to the untreated material was
measured in the Aerospace experiments. However, solid undisturbed
treated wastes indicated lower permeabilities by a factor of approximately
two to several orders of magnitude (Table 9). (For similar wastes, WES
data from Reference 12 show a factor of about two higher to two orders of
magnitude lower permeabilities for solid, fixed sludges when compared to
untreated wastes.)
Results indicate that chemical treatment tends to reduce the
permeability, and that fracturing and crushing of the treated wastes in-the
field will increase the permeability by some factor, depending on the degree
of fracturing. Also, it has been reported informally by several sources
that weathering (freeze-thaw cycling) of the treated wastes tends to induce
cracks in the material. Therefore, the permeability will be affected to
some extent by the depth to which the freeze extends.
5.1.1.4.8 Compressibility Compaction Characteristics of
FGC Wastes
An important consideration in the disposal of FGD sludges is
the volume or land area required. Therefore consideration of mechanical
compaction of the FGC waste to reduce its volume is one of the factors
involved in the economics of disposal.
Typical compaction behavior of TVA Shawnee limestone waste
is shown in Figure 14. Three nominal values of 79, 86, and 93 percent
solids content were selected. The results show that the amount of water in
the samples had a marked effect on the compaction that occurred under load.
In general, the most compaction (~15 percent), took place at the lowest
-67-
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100
80
CO
£ 60
o
o
1 40
8
TVA SHAWNEE LIMESTONE SLUDGE
15 JUN 1974
2
1
CURVE SOLIDS. %
20
1
2
3
94.2%
86.3%
78.9%
ARROWS INDICATE
END POINT AFTER
REMOVAL OF
SAMPLE FROM MOLD
10
VOLUME CHANGE, %
15
Figure 14. Compressibility characteristics of TVA Shawnee
limestone, untreated FGC waste, June 15, 1974
-68-
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solids content, and the least compaction (~5 percent) took place at the
highest solids content. Upon release of the compaction load, the resultant
permanent change was 1 to 3 percent (Figure 14). Data for five other wastes
from TVA Shawnee (lime), Arizona Cholla, Duquesne Phillips, GM Parma,
and Utah Gadsby are given in Reference 5.
An explanation of the behavior observed relates to the
crystalline structure'of the wastes. When a stress is applied to packed
particles having the platey calcium sulfite crystals they bend and deflect.
The particles tend to return to their original configuration when the stress
is removed. For lath-like gypsum crystals, the growth trend is to form
intergrown crystals, with the result being a loosely packed, open network
of crystals. The presence of fly ash in the sludge tends to fill the voids
between the crystals. Force applied to this arrangement of particles flexes
the gypsum crystals and possibly breaks the intergrown clusters; however,
increased particle packing is difficult. Only in those cases where particles
are reasonably blocky does effective packing take place. Among the six
sludges tested, this took place only in the GM Parma and the Arizona Cholla
samples.
Criteria for safe access to a pond by personnel or equipment
or for land reclamation potential may be based on the load bearing strength
of the waste. The parameter most significantly affecting the strength of a
given waste is its solids content; therefore, measurements were made to
5
correlate load bearing strength as a function of solids content.
Load bearing strength was also measured for several wastes
4
with solids content from 55 to 70 percent (Figure 15). At 55 percent solids,
the wastes can sustain virtually no load, while at 70 percent solids load
bearing strength of 2. 1 to 2.4 x 10 dyne/cm (30 to 35 psi) exists for a
Shawnee sludge. Levels capable of supporting a person while standing,
5 2
2 x 10 dyne/cm (3 psi), by TVA Shawnee sludge would be attained at ap-
proximately 60 percent solids content.
-69-
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35 r-
30
-TVA SHAWNEE (Limestone)
. 25
| 20
o
E 15
oc
UJ
QQ
o 10
i
5
0
SCE MOHAVE (Limestone)
70 65 60
SOLIDS CONTENT, weight %
55
Figure 15. Load bearing capacity of FGC wastes
-70-
-------
At 70 percent solids where the strength increased rapidly,
the waste is at its saturation point. Removal of additional water reduces
the lubrication between particles in the waste and accounts for the rapid
increase in strength.
In the case cited above, accessibility to personnel could
probably be permitted if the solids content is greater than 65 percent, at
which point a load bearing capacity of 5.5 X 10 dyne/cm (8 psi) is
expected. It should be noted that this corresponds to the dryness expected
by vacuum filtering (Figure 4).
With a solids content of 70 percent, vehicles could probably
be supported safely. However, it should be noted that below 70 percent
solids the strength drops rapidly. Mohave waste exhibited a sharp change
in strength at 65 percent solids (Figure 15); for that material, load bearing
strength ranged from about 2 to 20 x 10 dyne/cm (3 to 30 psi).
Based on the dewatering results reported solids content
greather than 65 percent can be attained with the SCE Mohave wastes by
using any of the dewatering processes—settling, centrifuging, or vacuum
filtering. Consequently, if no free-standing water were present, a disposal
site of Mohave waste could probably be traversed safely by personnel and
equipment.
5.1.1.5 Disposal Methods
For disposal methods to be considered environmentally sound,
they must provide the means of preventing or minimizing the seepage and
flow of waste liquors into water supplies. Disposal methods may be grouped
into one of two categories: (1) ponding and (2) landfilling. Each method has
unique characteristics, and one or more may be applicable at a given site,
depending on site conditions and the overall objectives of the user. These
factors are evaluated in Reference 5 for a number of ponding and landfill
alternatives for untreated and treated wastes.
-71-
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Environmentally, each of the methods offers a different form
of protection against water pollution, and a different approach to land recla-
mation. Since the long-term effects of ponding and landfilling are still
being evaluated, no single method is considered superior to others for all
cases, at this time.
5.. 1.1.5.1 Disposal Cost Estimates
Cost estimates for disposal in lined ponds and land-filling
of chemically treated FGC wastes have been made and reported by Aerospace
on several occasions. Detailed cost estimates were made of fixation dis-
posal and were reported in Reference 13. The lined ponding cost estimates
that were presented in Reference 4 were updated and are compared with
fixation disposal costs in Table 10.
The estimates are based on a typical 1000-MW power plant
burning coal with 3 percent sulfur and 12 percent ash. The service life of
the power plant is assumed to be 30 years, with the plant operating at an
average load factor of 50 percent, and with an annual average sludge (50 per-
cent solids including ash) production of 930,000 metric tons (1,025,000 short
tons). The annualized costs include the cost for labor, maintenance, and
capital charges of 18 percent. The capital charges include replacements,
insurance, taxes, cost of capital based on 50/50 debt/equity funding, an'd
the use of straight-line depreciation.
This comparison indicates that the cost of ponding is approxi-
mately 75 percent of the fixation disposal costs. Additional costs for the
reclamation of the site, which may include the addition of top soil and
nutrients on fixed landfills, and a yet-to-be defined procedure for closing
down an pond for permanent environmental protection are not included in
the estimate. Excluded is any "cost reduction" in terms of realizing the
residual value of the land where applicable; however, the land is depreciated
throughout the lifetime of the pond. Any benefit realized from including
current ash disposal with FGD total waste disposal where applicable is also
excluded.
-72-
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Table 10. DISPOSAL COST RANGES FOR PONDING
AND CHEMICAL TREATMENT3"
Disposal
Method
Lined Pond
Q
Chemical Treatment
$/Ton of FGCd'e
Waste (Dry)
5.70 to 7.80
7.30 to 11.40
$/Ton of Coal6
1.62 to 2.22
2.07 to 3.24
Mills /kWhe
0.7 to 0.96
0 . 9 to 1.4
1000-MW station, 50% load factor, 30-yr average, January 1976 dollars
(land costs at $1000/acre are included).
Ponding costs cover range based on low-to-high material costs; i.e.,
PVC-20 (low) to Hypalon-30 (high).
'Fixation costs vary from low to high depending on characteristics of the
waste and the disposal process chosen.
510,000 short tons/yr average (dry basis) including fly ash.
JCoal burned at rate of 0.88 Ib/kWh (85% SO2 removal:
1.2 CaCOo/SOo mole ratio with an 85% SO2 removal efficiency;
3% sulfur; 12% ash).
-73-
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5.1.2 Shawnee FGD Waste Disposal Field Evaluation
(TVA and The Aerospace Corporation)
This project, which is managed by the EPA Industrial
Environmental Research Laboratory (IERL), Research Triangle Park, North
Carolina, was initiated to evaluate and monitor the field-site disposal of
untreated and treated FGC wastes. Its purpose is to determine the effects
of several scrubbing operations, waste treatment methods, disposal tech-
niques, soil interactions, and field operation procedures. Test samples of
treated and untreated wastes, ground water, surface water, leachate, and
soil cores are being analyzed in order to evaluate the environmental accept-
ability of current disposal technology. On the basis of this program, engi-
neering estimates of total costs (capital and operating) projected foi- full-
scale FGD waste treatment and disposal have been made.
Correlations are also being made between laboratory-
prepared samples and those created under field operating conditions. The
results obtained are being used to form a basic understanding of the charac-
teristics of field operations, to define procedures for planning additional
evaluation at this site, and to assist in the development of other EPA-
sponsored field evaluations. The site selected for the evaluation was the
TVA Shawnee Power Station at Paducah, Kentucky. Two 10-MW equivalent
prototype flue gas scrubber systems, one using lime and the other lime-
stone, produced wastes that were placed in five disposal ponds on the plant
site. Two of the ponds contain untreated wastes; each of the remaining
ponds contains wastes chemically treated by one to three commercial
contractors.
The Aerospace Corporation is providing program planning
and coordination and is conducting selected chemical analyses. Data evalua-
tion, costing estimates, and reporting are also Aerospace responsibilities.
TVA provides the on-site support relating to all pond construction and
j maintenance, filling of untreated ponds, and providing FGD waste for treat-
ment. Sample collection, analysis and distribution to other organizations,
-74-
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climatological and hydraulic data collection, and photographic documentation
services are also performed by TVA. Chemical treatment of the waste was
performed by Chemfix, Inc., Pittsburgh, Pennsylvania; Dravo Corporation
Pittsburgh, Pennsylvania; and IU Conversion Systems, Inc. (IUCS),
Philadelphia, Pennyslvania. The Bechtel Corporation (the scrubber facility
test director) provided the technical interface relating the scrubber test
facility to the disposal evaluation.
The program began in September 1974 with the filling of the
first untreated pond and is scheduled to continue through 1977. Reports on
13- 15
the first year's results have been published recently. The highlights
of the first year's findings are included herein. Future plans include the
evaluation of other disposal conditions including gypsum disposal.
5.1.2.1 Project Status
The TVA Shawnee Power Station at Paducah, Kentucky, is
the site of the field evaluation. Two different scrubber systems are being
operated at this station as an EPA/TVA test facility. One scrubber is a
Universal Oil Products (UOP) turbulent contact absorber (TCA) and uses
limestone as the SO- absorbent; the other is a Chemico venturi followed by
a spray tower using lime. Both scrub the fly ash and absorb the SO_ as
well. Each scrubber system is capable of independently treating up to •
10 MW equivalent of flue gas from one boiler (approximately 30,000 ft /min
at 300° F). Wastes from these scrubbers were used in the disposal evalua-
tion and are undergoing analysis in several laboratories under EPA
u- 13
sponsorship.
The disposal evaluation site consists of five disposal ponds,
each occupying approximately 0.1 acre near the Shawnee plant, approxi-
mately one mile south of the Ohio River. All the ponds were filled between
October 7, 1974 and April 23, 1975 to a depth of about 3 ft. The charac-
teristics of the fill material are shown in Table 11. Two of the ponds con-
tain untreated wastes; each of the remaining ponds contains wastes chemi-
cally treated by one of the three commercial contractors. The surfaces of
-75-
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Table 11. POND AND FGC WASTE CHARACTERISTICS
Pond
A
B
C
D
E
Scrubber
Venturi,
spray
tower
TCA
Venturi,
spray
tower
TCA
TCA
Absorbent,
Lime ,
filter cake
Limestone,
clarifier
underflow
Lime,
centrifuge
cake
Limestone,
clarifier
underflow
Limestone,
clarifier
underflow
Untreated
Solids
Content,
weight %
46
38
55
38
38
38
Fly Ash
Solids
Content,
weight %
43
40
45
38
38
38
Treatment
Contractor
Untreated
Dravo
IUCS
Untreated
Untreated
Chemfix
Fill and Treatment
Date
Sep 24 - Oct 8, 1974
Apr 7-15, 1975
Mar 31 - Apr 23, 1975
Oct 11-20, 1974
Jan 13 - Feb 5, 1975
Dec 3-7, 1974
I
-vl
-------
the three treated ponds were sloped to create a wet section, consisting of
a combination of liquor and rain water, and a potential dry section (depend-
ing on weather conditions) for the observation of physical conditions of dry
material. Within each pond is a leachate well for sampling water that
collects at the waste-soil interface. A ground water well is located on a
bern of each pond, between the sludge and the river. Ground water wells
are located approximately 100 ft south of each pond (away from the river)
to provide for the monitoring of background water quality. The disposal sites
are also being monitored periodically for leachate, supernate, and ground
water quality, soil chemistry changes, and treated waste chemical and
physical qualities.
Each of the three treated ponds was conditioned and filled by
the respective contractors in response to program requirements so that
various operational conditions and the effects of weather could be evaluated.
These operations, therefore, were not representative of identical disposal
conditions or necessarily the operational methods that would be employed
by any of the contractors. For example, different input materials were
supplied to the contractors, and the ponds were not provided with surface
runoff drainage so that the effects of trapped water could be observed.
One treated material, from Chemfix, was fractured and con-
toured by a back hoe; another, from Dravo, represents curing and disposal
under water where high strength is not necessarily required; and the other,
from IUCS, was not compacted by placement vehicles that would be used in
a full-scale operation. Therefore, comparisons between processes were
neither attempted nor implied in the evaluations. The principal environmen-
tal effects being observed are the quality of seepage water and the strength
and permeabilities of the treated materials. Correlations are also being
made between laboratory-prepared samples and those created under field
operating conditions. The results are being used to form a basic under-
standing of the characteristics of field operations.
-77-
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5.1.2.Z Analytical Results
Considerable data have been reported from the analyses of
input FGC wastes, supernate, leachate, ground water, and soil and treated
13
material cores. Since the quality of leachate and ground water and the
strength and permeability of the fixed and raw wastes are some of the more
significant of these data as they impact the environment, these results are
summarized in Table 12. It is expected that these data will be expanded
and correlated with other available laboratory and field evaluation data.
5.1.2.3 Untreated Wastes
The Pond A untreated waste leachate data show that the con-
centrations of the dissolved solids (Cl, SO., and TDS) progressively increase
with time. The data also indicate that the concentrations of the constituents
may approach those of the input liquor. Simultaneously, the concentrations
of these same constituents in the pond supernate vary with time. Neither the
scrubber system waste solids nor liquors are replenished; therefore, the
supernate should become diluted with rainfall as the program progresses.
Some fluctuation in this trend can be expected as a result of evaporation
during dry periods. The detection of heavy metals in the leachate and
supernate of this pond shows trends similar to the major species. However,
concentration projections cannot be made at this time because of the rela-
tively short period of time that the ponds have been extant. Continued
monitoring is expected to clarify this situation.
The other untreated pond, D, was filled initially and used as
the input source of material for the Chemfix operations at Pond E. At that
time, approximately 75 percent of the waste from Pond D was removed and
this pond was subsequently refilled with a similar waste several months
later. Waste removal and refilling of this pond have produced leachate trend
characteristics somewhat different from Pond A. Concentrations of the dis-
solved solids in the leachate are shown in Table 12 for this pond. The
accumulation of additional data will continue throughout the program and is
expected to produce trends that are characteristic of this material.
-78-
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Table 12. POND LEACHATE ANALYSES
Pond
A
D
B
C
E
Absorbent
Lime
Limestone
Limestone
Lime
Limestone
Fill Dates and
Fixation
Contractor
October 1974,
untreated
October 1974
and
February 1975,
untreated
April 1975,
Dravo
April 1975,
IUCS
December 1974,
Chemfix
Input Waste
Liquor
Solids,
wt%
46
38
38
55
38
TDS,
ppm
8285
5445
5685
9530
6245
Weeks
after
Filling
1
30
55
la
9
19
56
2
11
27
1
11
19
9
20
30
47
SO
ppmD
700
1250
1250
590
580
1420
1750
530
490
675
50
190
820
300
670
800
900
CLH
Ppm
600
3300
3400
210
-
1300
500
460
940
1100
2400
1200
1100
1.000
-
740
490
TDS,
ppmb
2200
7500
7560
1300
5200
4000
3370
1800
2600
2670
4700
3200
3300
2400
3400
3200
2690
Weeks from first filling.
'Surface water in leachate wells at Ponds A, B, D, and E resulted in a dilution of the early leachate samples.
-------
Analyses of samples of ground water (approximately 12 ft below Pond A and
40 ft below Pond D) have not shown any effect of seepage from these ponds.
5.1.2.4 Treated Wastes
The data from the ponds containing treated wastes, although
sampled over a shorter period of time, show trends similar to those of the
untreated waste except that the reduced concentrations of the constituents
are evident in the leachate from the chemically fixed wastes. Indications
are that these concentrations either start at or quickly build up (depending
on the amount of rain water initially present in the leachate well) to
approximately 50 percent of the respective concentrations in the liquor of
the untreated input waste (Table 12). Sampling is conducted bimonthly;
data illustrative of the trends are presented in Table 12. The long-term
results of these field evaluations will be evaluated and reported throughout
this project.
Laboratory column tests were conducted on an untreated TVA
Shawnee limestone scrubbing waste and a core taken from a treated pond at
the Shawnee disposal site. Chemical analyses of the leachate were per-
formed to define long-term TDS concentration trends; the results are shown
in Figure 16. The treated material contained limestone scrubber waste; of
the three treated ponds, the oldest one has been in operation for approxi-
mately one year. In these analyses, distilled water was allowed to seep
through the pores of the samples, and chemical analyses of the collected
leachate were made periodically. Figure 16 shows the TDS concentration
as a function of pore volume displacement of leachate water (pore volume
being defined as the nonsolid volumetric portion of a given mass). These
trends are generally typical for the various constituents of the materials,
• i j- ,. i .. 13, 14
including trace elements.
Several significant characteristics are shown in the data
presented in Figure 16. Both treated and untreated wastes display a steep
drop in leachate TDS concentration during the first five pore volume dis-
placements. During this period, salts from the sludge liquor trapped within
-80-
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10.000
CO
o
i
o
CO
o
CO
CO
<
o
1000
100
TVA SHAWNEE LIMESTONE
FGC WASTE
UNTREATED
TREATED (Pond E Core)
I
I
1
5 10 15 20 25
PORE VOLUME DISPLACEMENTS
30
Figure 16. i Results of laboratory column leaching tests
of treated and untreated wastes
-81-
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the pores are flushed out. Thereafter, solubility of the sulfite, sulfate,
and chloride within the solid mass becomes a controlling factor. Another
point of interest is that the time to achieve five pore volume displacements
is not the same for the two materials. Because the permeability rate of the
treated material is at least one order of magnitude lower than the untreated
material, the seepage of five pore volumes through the treated waste is
significantly delayed relative to the seepage through untreated wastes. A
third significant point is that, after the initial flushing period, the leachate
and the TDS concentrations stabilized at about 1900 ppm for the untreated
and 500 ppm for the treated. This represents a reduction in TDS concen-
tration of the leachate from treated material to about 25 percent of the
untreated waste.
The combined effects of all these factors are shown in
Figure 17 for the five cases defined in Table 13. These initial results are
from an analysis being conducted to project data (as in Figure 16) on opera-
tional conditions and time periods well beyond the end of this particular
project. Because a treated disposal site releases leachate to the subsoil
over a longer time period and at smaller concentrations than an untreated
disposal site, this analysis compares the treated and untreated materials in
terms of the mass per unit area of dissolved solids released to the subsoil
as a function of time.
The advantages of reducing the permeability and the solu-
bility of the wastes and of preventing water from accumulating on the surface
are highlighted in Figure 17. For example, for the first 100 years, a
treated material in a landfill with controlled runoff (Case 5) releases
approximately 1/80 of the mass of dissolved solids at a given rate to the
subsoil as an untreated material in a lake (Case 1), and approximately 1/10
as much as an untreated material in a pond (Case 3). The time in years to
reach five pore volume displacements (initial drainage period) is also
shown.
-82-
-------
1000
CM
CD
to
O
00
GO
100
10
CASE 1
END OF 5th PORE VOLUME
I I
0 20 40
60 81
YEARS
100 120 140 1300
Figure 17. Mass loading of TDS to subsoil for various disposal
modes of treated and untreated FGC wastes
-83-
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Table 13. CASES STUDIED FOR CALCULATING MASS LOADING
OF LEACHATE CONSTITUENTS INTO SUBSOIL
Case
1
2
3
4
5
Disposal
Method
Lakea
Lake
Pond
Pond
Landfill
Surface
Water
Constant
s up e mate
Constant
supernate
10. in. /yr
recharge
10. in. /yr
recharge
1 in. /yr
recharge
FGC Waste, 5 -Year Fill
Waste
• Condition
Untreated
Treated
Untreated
Treated
Treated
Depth,
ft
30
30
30
30
30
Permeability,
cm/sec^
1C'4
to'5
to'4
io-5
to'5
Fractional
Pore
Volume
0.67
0.67
0.67
0.67
0.67
aAssumed maximum hydraulic head of 6 ft during filling, including depth of
wastes; 1 ft constant water cover thereafter.
For all cases, subsoil permeability = 10" cm/sec.
-84-
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Such analyses are being continued; more specific operational
parameters will be applied as they evolve. Although some methods of dis-
posal release much lower mass to the subsoil than others, it is not apparent
at this time that the methods with the lower release rates are the only
acceptable approaches. Criteria for judging disposal methods are being
determined by the EPA and will be applied when they are available.
Some preliminary physical properties of the fixed wastes
are given in Table 14. Of particular interest are the permeabilities in the
range of 6.9 X 10 to 5, 5 X 10~ cm/sec and unconfined compressive
2
strengths of 3 to 39 ton/ft . Additional measurements of these properties
will be made on material from corings from the treated ponds taken
periodically throughout this project. FGC wastes that have not been treated
_4
or conditioned have permeability coefficients of approximately 10 cm/sec.
The structural strength is of no practical consequence. The effects of con-
ditioning untreated wastes, e.g., dewatering and compaction, are being
studied.
5.1.2.5 Soil
The ground waters show no evidence of altered quality
resulting from the filling of any of the five ponds. This result is in agree-
ment with expectations based upon the low permeabilities of clay soil samples
from the floor of the ponds. Based on soil characteristics, permeability
- 8
coefficients in the range of 10" cm/sec have been defined by TVA. Thus,
in one year, the waste leachate constituents would be expected to permeate
to a depth of less than 0. 5 in. Laboratory analyses using an ion micro-
probe mass analyzer are under way to detect the progress of the con-
stituents in successive soil cores in order to verify long-range analytical
predictions over the relatively short time period available within the time
span of the evaluation program. At this point, the initial calibration runs
have been completed on pond floor core samples to provide background data
for future tests.
-85-
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Table 14. CHARACTERISTICS OF CORES FROM CHEMICALLY TREATED FGC WASTES
Sample
Source
and
Date
Pond Ec
2/27/75
Pond Bd
6/12/75
Pond C°
5/29/75
6/12/75
Unconfined Compressive
Strength, psi
Weta
103 to 133
27 to 33
410 to 510
Dry
95 to 165
40 to 46
470 to 540
Density, g/cm
Weta
1.40 to 1.46
1.36 to 1.44
1.67 to 1.70
Dryb
0. 69 to 0. 73
0. 59 to 0. 62
1. 05 to 1.08
Water
Content,
wt%
51. 0 to 51. 5
56. 9 to 57. 8
36. 5 to 37.0
Estimated
Fractional
Pore
Volume
0. 71 to 0. 73
0.75 to 0. 76
0. 57 to 0.58
Water
Permeability,
cm/sec
1. 5 to 2.7 x 10"5
6.9 x 10"5
5.5 x 10'!j
5.5 x 10''
I
00
Wet: as received.
Dry: after oven drying.
CSamples from Ponds E and C were taken from locations free of surface water.
Pond B material was kept underwater continuously as in the case of disposal upstream of a dam.
-------
5.1.2.6 Future Plans
Plans are being developed to expand the TVA Shawnee site
evaluation to add two impoundments in order to evaluate other disposal
methods for untreated FGC wastes. The two wastes being considered are
(1) an oxidized sulfite waste and (2) a dewatered limestone waste that does
not contain fly ash, but to which is added a low-solids-content fly ash, mixed
and compacted at the test site.
These sites should be operating by the summer of 1976.
Later in this project, one or two of the four untreated disposal areas will
be drained of water and allowed to air-dry. The sites will then be capped,
contoured to drain rainwater, planted, and monitored for leachate quantity
and characteristics, as well as the strength of the material, throughout the
remainder of the project.
5.1.3 Laboratory and Field Evaluation of FGC Waste
Treatment Processes (U.S. Army
Engineer WES)
Studies are being conducted by the U.S. Army Engineer
Waterways Experiment Station (WES) in Vicksburg, Mississippi, to evaluate
chemical treatment (fixation) and environmental effects associated with the
disposal of FGC wastes. The program also includes a number of industrial
wastes. Although the industrial wastes will not be specifically addressed
in this report, the evaluation of the pollutant potential of these wastes will
be similar to those originating in the FGC processes.
The program has been divided into three areas encompassing
the following tasks:
a. Assessment of the pollution potential of the leaching of
untreated and chemically fixed FGC wastes.
b. Site survey and environmental assessment of existing
solid waste disposal sites.
c. Evaluation of existing FGC waste fixation technology.
-87-
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In assessing the pollution potential of the wastes, five
chemical fixation processes were used to threat five FGC wastes (Table 15).
The processes are being evaluated by means of leaching column studies and
physical and chemical testing of untreated and fixed wastes.
This task was initiated in July 1974. Interim reports will
present the results of physical properties of untreated and treated wastes
and the column results from leaching untreated wastes after approximately
eight months and treated wastes after about four months. The leaching
experiments are planned to continue for a total of two years. A summary of
the analyses and tests being conducted will be provided later in this report.
In order to accelerate the acquisition of a data base to assess
the pollutant migration and environmental impact from FGC wastes on land
disposal sites, a task to survey and characterize existing disposal sites has
been initiated. The primary goal will be to establish the extent of pollutant
migration from existing disposal sites, the relationship to site history and
disposal operations, and the establishment of site selection criteria. The
geology, hydrology, and chemistry of the sites and their surrounding media
will be studied. In addition to FGC disposal sites, industrial waste and
municipal refuse sites are included in the program. This report, however,
will emphasize the FGC aspects. Work on this task was begun in July 1975
and is expected to continue for two years.
The third task portion of the study involves the evaluation of
existing fixation technology. It is planned to compile a list of fixation
processors currently available and identify their respective areas of appli-
cation. Another objective is the development of a methodology for selection
and application of fixation technology based on economic analysis and process
evaluation. The latter includes the definition and development of a screen-
ing test for rapid and accurate assessment of the potential environmental
impact associated with the fixation and'idisppsal of FGC wastes. The pro-
gram is currently being initiated and is expected to extend over a two-year
period.
-88-
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Table 15. FGC WASTE AND CHEMICAL TREATMENT MATRIX
Code
No.
100
400
500
600
1000
Type of FGC Waste
Lime process,
eastern coal
Limestone process,
eastern coal
Double - alkali
process,
eastern coal
Limestone process,
western coal
Double -alkali
process,
western coal
Process Code Letter
A
X
X
X
X
X
B
X
X
X
X
X
E
X
X
X
X
X
F
X
NA
NA
X
NA
G
X
X
X
X
X
X: Waste fixed by processor and being tested in column
NA: Not applicable
Processes A, B, E, F, and G include (not listed in alphabetic order):
• Cement and fly ash additive
• Proprietary additive will pH adjustment
• Cement and sodium silicate additive
• Proprietary additive with pH adjustment
• Fly ash and lime additive
-89-
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The physical and engineering properties being reported are
outlined in Table 16. Bulk density, porosity, permeability, and unconfined
compressive strength data were reported in Reference 12 and are summa-
rized in Table 17. Fixation of the FGC waste results in a consolidated
material which is generally of higher density than the untreated waste, has
lower porosity and permeability and which demonstrates a degree of struc-
tural strength.
5.1.3.1 Assessment of Pollution Potential of Leaching of
Untreated and Chemically Fixed FGC Wastes
This task was initiated in July 1974. Five chemical fixation
processes were used to treat five FGC wastes (Table 15). The processes
will be evaluated by means of leaching and physical and chemical testing of
the untreated and chemically fixed wastes. The principal objectives of this
task are as follows:
a. To assess the application of fixation technology for
retarding the leaching (mass transport) of pollutants
from selected FGC wastes
b. To assess the leaching potential of those wastes
c. To determine the physical stability of the fixed wastes
and its relationship to disposal operations
d. To evaluate the potential role of fixation of FGC wastes
as a pretreatment proce.ss prior to ultimate disposal
5.1.3.1.1 Physical Testing
Physical testing of the raw and fixed wastes has been com-
pleted, and a report is being published. The approach taken by WES was
to characterize the wastes by evaluation of their physical and engineering
properties as determined by standard tests and procedures applied to soils.
The effects of the fixation process can then be assessed by
evaluating the change in properties resulting from fixation. Additional
characterization is possible by comparison of results with typical values of
familiar materials such as soil-cement, concrete, and soils.
-90-
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Table 16. PHYSICAL AND ENGINEERING PROPERTIES
Physical Properties
Specific Gravity
Bulk Density
Dry Density
Water Content
Void Ratio
Permeability
Grain Size Distribution
Engineering Properties
Compaction Test
Maximum Dry Density
Optimum Moisture Content
Unconfined Compression Test
Undrained Compression Test
Unconfined Compressive Strength
Modulus of Elasticity
Wet-Dry Weight Loss
Freeze-Thaw Characteristics
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Table 17. PHYSICAL PROPERTIES OF UNTREATED AND
: TREATED FGD WASTES
Sample
Identification
No.
R-100
R-400
R-500
R-600
R-1000
A- 100
A-400
A-500
A-600
A- 1000
B-100
B-400
B-500
B-600 •
B-1000
E-100
E-400
E-500
E-600
E-1000
F-100
F-600
G-100
G-400
G-500
G-600
G-1000
Dry Bulk
Density,
Ib/cf
51.7
63. 1
52.3
89.0
47.4
100. 1
108. 3
95.5
109. 3
96.6
77.0
89.0
90.8
79.6
81. 5
101. 1
82.7
99.3
110.9
82.7
_
81.0
_
62.7
52. 5
56.9
68. 1
Porosity, %
67.3
64.2
74.0
48.5
75.4
51.4
55.6
57.8
41.0
51.4
75.3
75. 5
71.6
76.3
73.2
45.7
55.4
49.0
35.4
50.8
_
52.4
_
69.7
75.4
73.4
• 70.0
Permeability,
cm/sec
1.07 x 10"j!
7.78 x 10'^
2.50 X 10'c
1.44 x 10"'
6.54 x 10
2.06 x 10"6
.7
1.13 x 10
, 4.31 x 10''
• 8,95 x 10"
1.59 x 10"c
1.08 x 10'^
4.56 x 10'^
3.96 x 10~j?
6.62 x 10
.4
7.94 x 10 J
2.52 x 10",,
4.54 x 10"o
3.57 x 10"°
7. 33 x 10
-6
5.01 x 10
.5
5.24 x 10 .
1.39 x 10"*
1.22 x 10"?
4.05 x 10"
Unconfined
Compressive Strength,
psi
_
-
-
-
-
100. 3
~
188.3
403. 1
337.4
23.7
44.5
42.7
35. 3
23.2
2570.0
720.0
2220.0
4486.0
1374.0
-
395.6
, .
242.6
86.4
126. 1
144. 3
-92-
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5.1.3.1.2 Leaching Tests .
The leaching tests are aimed at measuring the rate of pollu-
tant migration into an aqueous medium. One hundred sixty-two columns have
been assembled to simulate the dispersed flow and leaching of pollutants at
surfaces of cracks within the treated waste matrix. For treated wastes a
leaching surface-to-sludge volume ratio of 1.0 to 1.5 is being tested. A
treated sludge core, 3 in. in diameter and with a volume of approximately
0. 35 in. has been placed within a 4-in. (inner diameter) column, and the
annular space has been filled with polypropylene pellets. The leachate flow
rate is controlled to maintain a fluid velocity of about 1 X 10" cm/sec. Two
leaching fluids are being used to represent both sides of the pH spectrum and
to provide some insight into the effect of pH on leaching. One fluid is water
saturated with carbon dioxide having a pH of 4. 5 to 5. 0, and the other is
deionized water buffered with boric acid and a pH of 7. 5 to 8. 0. The columns
are being triplicated for each leaching solution.
Interim results of the leaching column studies are expected
to be available shortly. Data on untreated wastes that have been leached
in columns for approximately eight months and treated sludge exposed for
about four months are expected. In some cases, trends have not been
established, and additional data are required before comparisons can be
drawn. A listing of the data being acquired is reported in Table 18.
Information excerpted from a forthcoming WES report was
published in Reference 12; representative results are reported herein.
Specific conductance has been reported as a measure of the total TDS present
in a solution. The results presented in Figure 18 are paired data for con-
ductivity and dissolved solids on elutriates from all untreated and fixed
sludges utilized in the WES study. The data demonstrate a strong linear
relationship between these parameters and may be used to interpret
conductivity data derived from the leaching experiments by inferring a
relationship to dissolved solids.
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Table 18. CHEMICAL CHARACTERISTICS TESTS OF
UNTREATED AND TREATED FGC WASTES
Chemical Analysis: Concentration as a Function of Time
Cations
Arsenic
Beryllium
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Manganese
Mercury
Nickel
Selenium
Zinc
Anions
Chloride
Cyanide
Fluoride
Nitrate
Nitrate
Sulfate
Sulfite
Organic
Chemical oxygen demand
Total organic carbon
Leachate pH
Leachate Electrical Conductivity, fj,mhos/cm
-94-
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6500r-
6000
5500
5000
o
ID
O
O
4500
4000
a.
CO
3500
2000
1500
10001
"0 1000
2000 3000 4000 5000
DISSOLVED SOLIDS, mg//
6000
Figure 18. Conductivity versus dissolved solids
-95-
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For the experiments being conducted, the effect of the
process on leachate characteristics is illustrated in Figures 19 and 20 for
treated and untreated double-alkali and lime sludges. Generally, the con-
centration of sulfate in the leachate from the treated material is lower than
that from untreated. However, this is not always the case, e.g., where
process G appears to be typically higher and others exhibit a varying degree
of reduction in sulfite from slight to several orders of magnitude.
At this time, any conclusions based on these data are pre-
mature, inasmuch as the results reporting characteristics of other con-
stituents will not be available until the WES interim report is published.
Also, the long-range effects cannot be assessed as the results represent
approximately only six to eight months of leaching data.
5.1.3.2 Site Survey and Environmental Assessment of
Existing Solid Waste Disposal Sites
Site investigation is divided into preliminary investigative,
sampling, analysis, and environmental assessment. It is expected that
candidate site characteristics related to history, waste characteristics,
geology, and hydrology will be defined and quantified. A total of five sites
will be selected. A boring and sampling program will also be defined.
Samples of the waste, soil, pore water, and groundwater will be taken and
analyzed for chemical constituents and partition of pollutants (Table 19).
The present investigation is confined to a laboratory leaching test to assess
the mobility of pollutants under selected conditions. It is expected that
these results will give an insight into the mechanisms for pollutant trans-
port from residues outside the boundary of a disposal area. Physical
properties will also be determined. From these data, a preliminary assess-
ment of the environmental impact of land disposal for residues may be
stated, but an exact characterization of the degree of environmental impact,
if any, will have to await further investigations.
-96-
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50.000•—
10.000
^?
~i 1000
100
10
4
- i
- i
LEGEND
K
A
A
PROCESS A
PROCESS B
PROCESS
PROCESS
PROCESS G
RAW SLUDGE
E
F
b--.
40
80 120 160
ELAPSED TIME, days
200
240
Figure 19. Leaching results: sulfate, sludge No. 100
-------
50.000,—
10.000
1000
1/1
100
10
A
A
O
LEGEND
PROCESS A
PROCESS B
PROCESS E
PROCESS G
RAW SLUDGE
40
ELAPSED TIME,
Figure 20. Leaching results: sulfate, sludge No. 500
-98-
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Table 19. CHEMICAL ANALYSES ON SAMPLES FOR SITE SURVEYS
Arsenic
Beryllium
Cadmium
Chromium
Cyanide
Copper
Mercury
Magnesium
Manganese
Nickel
Iron
Lead
Selenium
Zinc
Sulfite
Sulfate
Boron
Chloride
Vanadium
Nitrites
Nitrate
Hydrocarbons
Total organic carbon
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To date, contact has been made with all companies known
to have operational FGD sludge disposal sites. One site has been visited
and rejected for study because of geologic conditions at the disposal site.
5.1.3.3 .Evaluation of Existing FGC Waste Fixation
Technology
During this portion of the study, a compilation of FGC waste
processes currently available will be made and their respective areas of
application identified. The development of a methodology for selection and
application of fixation technology based on economic analyses and process
evaluation is also planned. The latter task includes the definition and devel-
opment of a screening test for rapid and accurate assessment of .the poten-
tial environmental impact associated with the fixation and disposal of FGC
wastes. The program is currently being initiated and is expected to extend
over a two-year period. The same FGC wastes.that were evaluated in the
pollution potential task (Table 15) will be treated with a number of materials
selected on the basis of a survey of the Corps of Engineers soil and dust
control materials and methods. On the basis of field experience by the
Corps of Engineers, a list of candidate materials has been identified
(Table 20). Limited testing, appropriate to define optimum concentration
of additives, will be performed. The screening criteria which are beirig
defined will be developed to evaluate the efficacy of potential fixation
processes and also the environmental effects of solid waste on a disposal
site.
5. 1.4 Characterization of Effluents from Coal-Fired
Power Plants (TVA)
This interagency-funded program with TVA is being conducted
by the Power Research Staff, Chattanooga, Tennessee; Studies of liquid-
and solid-related effluents are under the cognizance of Julian W. Jones, -the
-100-
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Table 20. LIST OF CANDIDATE FIXATION MATERIALS
Cement
Lime
Calcium Carbide
Sodium Silicate
Chrome Lignin
Analine Furfural
A Polyurethane Resin
/
A Water-Soluble Acrylamide and Diacrylamide
An Unsaturated Polyester Resin
A Dialkyl Dimethl Ammonium Chloride
Three Proprietary Compounds That Solidify by a Hydration Reaction
-101-
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EPA Industrial Environmental Research Laboratory (IERL), Research
Triangle Park, North Carolina; studies of gaseous effluents are under
Ron A. Venezia, also of IERL. This report addresses the work in the
liquid- and solid-waste areas only.
The water- and solid-waste program is comprised of 5 tasks
extending over a period of approximately 38 months. A final report is
planned for late 1978. Chemical properties of coal-pile drainage will be
characterized and quantified. A second task will be an assessment of the
adjustment of pH on the physical and chemical composition of ash pond
effluents for purposes of meeting effluent standards. The frequency of
sampling and analysis for an effective ash pond monitoring program will be
defined, and a monitoring system designed and tested. The effects of coal
ash leachate on ground water quality will be characterized and quantified;
lastly, an assessment of the total residual chlorine, its components (free
and combined), and chlorinated organics discharged from a once-through
cooling system will be conducted. The status of the various tasks as of
December 31, 1975 is shown in Table 21.
5.1.5 Fly Ash Characterization and Disposal (TVA)
The objectives of this interagency-funded program with TVA,
Power Research Staff, Chattanooga, are to characterize, chemically and
physically, coal-fired boiler ashes and their waste effluents. In addition,
studies on fly ash handling systems and disposal, utilization, and treatment
methods for water reuse will be conducted. Work was initiated in June 1975,
and the final report on the project is planned for December 1979. Specifically,
data from TVA and other sources on the characteristics of ash will be sum-
marized and evaluated. Secondly, chemical and physical analyses of coal,
coal ashes, and ash effluents are planned in order to characterize these
materials at two different plants with different boiler designs and burning
different types of coal. The various methods available for disposal and
utilization of fly ash may also be evaluated, depending on fuel availability.
-102-
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Table 21. PROGRAM STATUS
Program
Remarks
Characterization of Coal-Pile Drainage
Assessment of pH Adjustment
o
OJ
I
Design of Monitoring System for Ash
Pond Effluents
Effect of Coal Ash Leachate on Water
Quality
The Colbert and Kingston plants were selected for
the study. The definition of the experimental
and sampling program has been completed for
Kingston and is under way at Colbert.
A mathematical model and computer program
have been developed to simulate the batch
settling characteristics of fly ash and bottom
ash in a continuous pond system. A preliminary
field study was completed for the Colbert plant
with samples taken for chemical analysis.
Laboratory column studies are being conducted.
Analysis of effluent data is still under way.
Recently available information is being in-
corporated into the analysis to develop the
experimental design. The Kingston and Colbert
plants were selected as the sites for sample
collection and evaluation.
The Kingston and Colbert generating plants were
selected as the site for this investigation. Soil
core samples and monitoring wells will be in-
stalled. A one-year sampling program is
planned. Because of geological complications
at Colbert, the Widow's Creek plant has been
tentatively selected as a replacement.
(Continued)
-------
Table 21. PROGRAM STATUS (Continued)
Program
Remarks
Effect of Chlorinated Effluents
The Kingston plant was selected for study.
However, preliminary studies indicated that
the intake water pH was high and varied sea-
sonally. Because of these widely varying con-
ditions, further testing was dropped, and the
John Sevier plant was selected as a possible
site for future work. Evaluation of prelim-
inary data, water quality, and chlorine demand
is being performed.
-------
The first phase of the program, scheduled for completion in June 1978, will
conclude with a summary of information on methods of treating sluice water
for reuse.
Studies of dry and wet ash handling systems may be conducted,
and recommendations may be made relative to the more promising systems
for ash handling, disposal, and utilization alternatives.
The TVA plants at Colbert and Kingston have been selected
for conducting chemical analyses of the streams. Complete stream charac-
terization will be conducted initially for the Colbert plant only. It is to be
noted that some of the work is being performed under another project,
"Characterization of Effluents from Coal-Fired Power Plants," reported in
Section 5. 1.4.
In order to develop sampling procedures and methods, a
preliminary sampling program was conducted at the Colbert Steam Plant.
Sampling sites included the coal scales, pulverizers, mechanical collector,
electrostatic precipitator (ESP), and pyrite hoppers and their respective ash
slurry streams. Some sampling problems were experienced. These were
primarily associated with various outages of plant equipment. Modifications
in procedures as a result of the preliminary sampling program are being
devised. The summary of coal and ash data is expected to be completed in
calendar year 1976. Other tasks are in initial stages of implementation.
5.1.6 Studies of Attenuation of FGC Waste Leachate
by Soil (U.S. Army Materiel Command)
The U.S. Army Materiel Command, Dugway Proving Ground,
Utah, is conducting a study to determine the extent that heavy metals and
other chemical constituents of FGC wastes can migrate through soil in land
disposal sites. The experimental FGC program was initiated in December
1975 and will be conducted over a period of 24 months. The project consists
of the following tasks: (1) physical and chemical characterization of
wastes and preliminary screening tests with a variety of United States soil
types, (2) leachate studies in columns with the wastes applied to two selected
-105-
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(best and worst) soil types, (3) long-term permeability tests with selected
clays, and (4) interpretation of data from the tests in (1) and (2) to identify
soil attenuation mechanisms and to develop empirical attenuation coefficients
for specific chemical substances.
Six FGC wastes, as well as fly ash from one source, will be
i
leached with water through six clay-type soils. The sources for the wastes
and soils have been selected and are summarized in Table 22. The columns
are transparent, 2 in. in diameter, and will be operated in groups of three.
A head of 8 ft of liquid will be maintained over a 4-in. sludge and soil sample.
In addition to sampling and analyzing the leachate from the
columns for heavy metals and other chemical constituents that may impair
water quality, provisions have been made to obtain leachate samples at the
waste-soil interface of the columns. This leachate will also be analyzed.
When one of the compounds is found in the soil column effluent ("break-
through"), one of the three columns will be sectioned, digested, or extracted,
and each section will be analyzed for the compounds of interest. This will
provide information as to the distribution and mobility of the compounds
through the soil with time. The remaining two columns will continue to be
leached until one or two additional compounds are detected (this will be
somewhat dependent upon the time between the first and second breakthrough).
One of the two remaining columns will then be sectioned and analyzed as
previously described. The remaining column will be treated with a fresh
portion of waste, and the leaching will be continued until a. significant change
is observed in the concentration or the composition of the soil column
/
effluent (pH, conductivity, or concentration of metals breaking through the
column). /
Flow rates through the column will be monitored in order to
detect any changes in permeability of the soil resulting from possible
interactions with the wastes. Flow rate tests through the soil in the columns
7 »
are currently being conducted. Although uniform procedures and techniques
are used to pack the soil into columns, a wide range of flow rates may be
observed through the column when conditions have equilibrated after several
-106-
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Table 22. SOURCES OF FGC WASTES AND SOILS IN THE SOIL
ATTENUATION TEST PROGRAM
FGC WASTES
Sources
Duquesne Light Co. ,
Phillips Power Station
Commonwealth Edison Co. ,
Will County Station
GM, Parma
Arizona Public Service Co. ,
Cholla Station
TVA
Shawnee
Kansas City Power and Light and
Kansas Gas and Electric,
LaCygne Station
Type of Material
Wet lime -scrubbed flue gas
waste including fly ash;
eastern coal
Wet lime stone- scrubbed flue gas
waste including fly ash; eastern coal
Double-alkali process waste;
eastern coal
Wet lime stone- scrubbed flue gas waste
including fly ash; western coal
a. Wet lime- and lime stone- scrubbed
flue gas waste including fly ash;
eastern coal
b. Fly ash; eastern coal
Wet lime stone- scrubbed flue gas waste
including fly ash; eastern coal
Soilsa
Source
Davidson, NC
Chalmers, IN
Nicholson, KY
Shawnee, KY
Dugway, UT
Soil Order and Great Soil Group
Ultisol; R B Lateritic
Mollisol; Prairie
Alfisol; G B Podzolic
aAll soils are clay-type.
-107-
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days of flowing. A number of columns (approximately twice the number
required) are being packed and flow-tested to obtain columns with similar
flow characteristics.
Soil characterization tests, i.e., pH, cation, exchange
capacity, and mineralogy, are being performed and will be compared to the
column results to determine if these tests may be used as a predictive tech-
nique in screening and assessing suitability of soils in any disposal site.
FGC wastes from two sources are being tested in this pro-
gram, from the Phillips station and Will County. Material from, the two
locations are also being used in the leachate liner compatibility studies con-
ducted at WES (Section 5.2.2).
5.1.7 Establishment of a Data Base for FGC Waste
Disposal Standards Development (SCS Engineers)
A program was initiated in December 1975 with SCS Engineers,
Long Beach, California, to establish a data base for use by EPA in its
development of FGC waste disposal standards. Preceding the development
of such a data base, an evaluation will be performed of the potential tech-
nological and economic impacts of applying any existing standards or
regulations.
The criteria that may be considered in the development of
standards or regulations when evaluating land disposal options will be
defined. Health, ecological, and aesthetic factors based on FGC waste
characteristics and land site considerations will be included. In addition,
a compilation of any proposed or existing standards and regulations appli-
cable to land disposal of FGC wastes is planned. The technological and
economic impact of options available for complying with such standards
and regulations and the economic and institutional impacts of their applica-
tion will be assessed.
Subsequently, a technical data base for standards develop-
ment will be established. This involves a definition of the interrelationships
between environmental effects (health, ecological, safety, and aesthetics)
-108-
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and regulatory approaches (local, regional, and national) subcategorized by
FGC waste characteristics, control, and treatment technology. Recommen-
dations will be made for research and development needs and priorities
needed to implement any potential standards or regulations.
5.2 PROCESS TECHNOLOGY ASSESSMENT AND NEW
TECHNOLOGY DEVELOPMENT
The technology assessment and development efforts, totaling
four projects, include (1) field studies of untreated and chemically treated
FGC wastes, (2) FGC waste leachate-disposal site liner compatibility studies,
(3) studies to correlate waste solid characteristics with scrubber operating
conditions, and (4) dewatering equipment design studies.
5.201 Evaluation of FGD Waste Disposal Options
(Louisville Gas and Electric)
Studies including the chemical and nonchemical processes
for the stabilization of FGC scrubber wastes are planned in this 18-month
project with Louisville Gas and Electric Company, Louisville, Kentucky.
Laboratory testing and field evaluations of stabilized wastes are included.
The contract is currently being negotiated and is expected to begin in the
second quarter of CY 1976. The test program is expected to be conducted
by Combustion Engineering, Windsor Locks, Connecticut.
Laboratory-scale tests will be conducted to determine opti-
mum conditions for chemical treatment and physical stabilization of carbide
lime and commercial lime FGC scrubber wastes. The scrubber wastes will
be treated with lime, slaked lime, and portland cement additives. Some of
these formulations will contain fly ash, and others will not. Chemical and
physical screening tests will be performed on the samples comprising a
matrix of treatment conditions. Selection will be made of the treated mixtures
and processing conditions that will receive further evaluation under field
conditions.
-109-
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3 3
The field studies will include 25 yd (19 m ) above-ground
impoundments of the treated wastes. Leachate, runoff, and physical prop-
erty tests of stabilized and unstabilized wastes are planned. Two stabilized
3 3
wastes will be selected for evaluation in 100 yd (76 m ) landfills. As in the
smaller scale impoundment studies, leachate, runoff, and physical properties
of the wastes will be determined.
An interim report is planned upon completion of the labora-
tory studies, approximately eight months after start of the program. Field
tests are scheduled to begin approximately five months after go-ahead and
continue for approximately one year thereafter. A final report will be
issued on conclusion of the program.
5.2.2 FGD Waste Leachate-Liner Compatibility Studies
(U.S. Army Engineer WES)
A program to assess the use of liners to contain FGD wastes
in disposal ponds is being conducted by the U.S. Arm/ Engineer WES,
Vicksburg, Mississippi. An experimental program to determine the com-
patibility of 18 liner materials with FGD wastes, liquors, and leachates has
been defined. Estimates of liner lifetimes will be made on the basis of both
a one- and a two-year exposure of the liners to the wastes. The economics
of FGD disposal by ponding will then be assessed. The cost of the liner
materials and placement will be included, as well as associated and con-
struction costs. The program was initiated July 1975 and is scheduled to be
conducted over a period of 36 months.
Ten chemicals will be admixed into soil; six sprayon-type
materials and two flexible liners have been selected for exposure to two
FGD wastes. Both FGD wastes will be from plants burning eastern coal,
one from a lime-scrubbed flue gas and the other limestone. A summary of
the liner materials and source of the sludges is shown in Tables 23 and 24.
The 18 liner materials will be exposed in a temperature-controlled environ-
ment, within a total of 72 cells designed to simulate a sludge depth of
approximately 30 ft.
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Table 23. LINER MATERIALS
Material
Material Type
Manufacturer
Sprayon Type
DCA-1295
Dynatech Formulation 267
Uniroyal
Aerospray 70
AC 40
SSK
Polyvinyl acetate
Natural rubber latex
Natural latex
Polyvinyl acetate
Asphalt cement
Slow setting cationic
emulsified asphalt
Union Carbide
Dynatech Research and Development Co.
Uniroyal, Inc.
American Cyanamid
Globe Asphalt
Globe Asphalt
Admixe s
Cement
Lime
Fly Ash
Cement with Lime
Cement with Fly Ash
Lime with Fly Ash
M179
Guartec (UF)
Analine, Furfural
Asphalt Concrete Paving
Polymer bentonite blend
A light grey powder
Dundee Cement Co.
Williams Keith Lime Co.
Amax Fly Ash Co.
Dowell Div. of Dow Chemical
General Mills
GAF Corp (Analine) and General Mills (furfural)
Local Contractors
Prefabricated Membranes
Liner
T-16
Elasticized polyolefin
(30 mil)
Black neoprene-coated
nylon-reinforced fabric
The Goodyear Tire and Rubber Co.
Reeves Brothers, Inc.
-------
Table 24. FGD WASTES
Type of FGD Waste Source of Coal Sample Source
Lime-scrubbed Eastern coal Duquesne Light Co. , Phillips
Power Station
Lime stone-scrubbed Eastern coal Commonwealth Edison, Will
County Station, Unit No. 1
-------
Physical property and durability tests such as weight, thick-
ness, density, and tensile strength will be performed on the as-received
liner materials and, again, after both a 12- and a 24-month exposure. The
leachate from each cell will be measured and analyzed. Daily monitoring of
the test cells is planned to observe if any breakthroughs occur.
Currently, the test cells have been designed and are being
fabricated. The liner materials are being procured. Testing is expected to
begin in March 1976. An interim report midway through the program and
a final report are planned.
5,2,3 Lime and Limestone Wet Scrubbing Waste
Characterization (TVA)
The effects of scrubber operating conditions on FGC waste
characteristics are being correlated in this program, which is part of an
interagency agreement with TVA, Power Research Staff, Chattanooga,
Tennessee. The FGC waste materials from the TVA Shawnee scrubber
facility will be characterized and the physical and chemical properties corre-
lated with scrubber operating conditions. The goal of the program is to
determine the feasibility of controlling waste characteristics to improve
disposal and utilization economics.
Correlation of the Shawnee scrubber operation and sludge
characteristics is scheduled for completion by the middle of calendar
year 1977 with a milestone report available late in calendar year 1976.
Settling rates, settled bulk density, and percent solids were
determined for seven samples obtained from the Shawnee TCA and venturi
scrubbing systems. Although the amount of preliminary data is limited, it
appears that the lime and limestone slurries may be differentiated by both
settling behavior and settling rate. Slurries from the lime scrubbing
operation appear to settle and approach compaction smoothly, while those
produced in the limestone system show a noticeable and reproducible
increase in settling rate immediately before, or upon the onset of, com-
paction,, The mechanism for this behavior has not as yet been defined.
-113-.
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A comparison was made of the results.of sludge settling rate
tests as performed by TVA at Muscle Shoals and in the chemical laboratory
at the Shawnee test facility. The results did not show any systematic,
significant differences between the Dorr-Oliver method used at Shawnee and
the static test method employed a~t Muscle Shoals. SEM photographs of the
samples show the calcium sulfite hemihydrate CaSO- 1/2H-O occurs in a
; J £ *•
variety of textures. In the TCA-limestone system, the sulfite occurs as
individual platey crystals and a few rosettes of thin crystals. The sulfite
solids from the venturi-lime system generally occur as compact, spherical
aggregates which result in faster settling rates. The mechanism of aggre-
gate formation is not known but can have a significant effect on the physical
behavior of the solids.
Although no correlations between operating parameters with
chemical or physical properties of the waste materials have been defined,
there is an inverse relationship identified between stoichiometr'ic ratio and
CaSO_- 1/ZH_O crystal size. Since there is a wide variation in crystal size
within a given sample, usually spanning more than two orders of magnitude,
it is difficult to arrive at a meaningful estimate of the average crystal size.
However, this qualitative relationship was reported as easiest to observe in
extreme cases as when one sample with a stoichiometric ratio of 1. 03 was
compared to another with a ratio of 1.43. The failure to determine other
mathematical relationships is viewed as a result of the relative sparsity of
the data at this point, and further work is continuing to analyze additional
samples.
Significant differences in filtration rates relative to those
usually encountered were observed with venturi lime slurries. The filter
cake sample taken at a time when filtration rates were exceptionally high
showed large, well-formed platey crystals of CaSO^ i/ZU^O, whereas the
sample obtained during a period of poor filtration consisted of much smaller
crystals. Therefore, sludge samples obtained from the venturi clarifier
underflow and the dried solids produced at the drum filter installed in the
same process stream were examined. Infrared analyses reveal no charac-
teristics significantly different from other samples.
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Characterization work was also performed upon various
samples taken from the derrdster sections of the TCA and venturi during
routine mechanical inspections. The as-received samples were reported to
be of a mud-like consistency, containing lumps which appeared as a
homogeneous unlayered structure. SEM photographs of the dried solids of
these samples are being evaluated.
Work is continuing toward the development of a practical
method of quantitative x-ray analysis of dried solids components, the objec-
tive being to provide a means of determining the distribution of sulfate and
sulfite species within a sample. Preliminary results indicate that this
method will not determine the sulfate ion concentration with the required
precision at the levels currently being observed in the scrubber solids. The
decision to implement this analytical method or to terminate its developmental
work is expected to be made shortly.
5.2.4 Dewatering Principles and Equipment Design
Studies (Auburn University)
This project to be conducted by Auburn University, Auburn,
Alabama, will consist of an examination of current dewatering equipment
design principles to determine their applicability for use on FGC wastes.
Laboratory settling and other tests will be conducted to determine the
behavior of FGC wastes. Subsequently, equipment design studies based on
FGC waste behavior are planned. This will be followed by laboratory bench
tests of the dewatering equipment design concepts. Further testing of
promising developments may be conducted if there is sufficient interest
expressed by private industry.
5.3 PROCESS ECONOMICS STUDIES
Economic studies are interwoven within most of the various
projects. Assessment of process technology or environmental impact
includes an examination of the economics involved. However, those pri-
marily related to economics are discussed in this section and include
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(1) conceptual design and cost studies for current disposal practices and
(2) gypsum by-product marketing studies. Both are being conducted by
TVA.
5.3.1 Conceptual Design and Cost Studies of Alternative
Methods for Lime and Limestone Scrubbing Waste
Disposal (TVA)
In this study by TVA, Office of Agricultural and Chemical
Development, Muscle Shoals, Alabama, several FGC waste treatment
methods and disposal methods will be selected for detailed economic
evaluation.
In disposal of the wastes from lime and limestone scrubbing
processes, numerous design and processing options are available. These
include variations in dewatering techniques and fly ash content. Waste
treatment such as forced oxidation (to gypsum) and chemical fixation includes
a number of alternatives. Disposal site characteristics, i.e., location,
ponding (with and without liners), and landfill, comprise another set of options.
A survey of the available technology has begun, including
costs for commercially available and developed FGC waste disposal systems.
The TVA Shawnee field disposal evaluation and engineering cost analysis
being performed by The Aerospace Corporation (Section 5. 1. 1) is expected
to provide significant visibility in defining direction for the study.
Selection of the most representative commercial alternatives .
with definition of design and cost premises to reflect practical applications is
planned for completion early in 1976. Preparation of flowsheets, material
balances, equipment and material lists and layouts, and investment and
operating cost information for comparing the various alternatives will be
available thereafter. All major options and variables will then be analyzed.
The analysis will include the use of a cost-oriented computer program being
developed to project all lime and limestone processing costs. A final report
is scheduled for completion in April 1977.
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5.3.2 Gypsum By-Product Marketing Studies (TVA)
This project is a task of the conceptual design and cost study
of the alternative methods for lime and limestone scrubbing waste disposal.
It is being conducted by TVA, Office of Agricultural and Chemical Develop-
ment, Muscle Shoals, Alabama, in an interagency agreement with EPA.
A preliminary study conducted by TVA during early 1974
indicated that production and sale of abatement gypsum to the wallboard
industry in the United States might offer a substantial economic advantage
over FGC waste disposal. A series of detailed market studies on by-
product sulfuric acid and elemental sulfur in the United States were also
18
conducted for EPA by TVA. These studies involved a transportation
cost model and a power plant SO- emissions inventory, which were estab-
lished for the states east of the Rocky Mountains. These studies provided
a significant step toward a more detailed evaluation of the economics of
using gypsum that may be formed in an SO_ abatement process.
The current project includes a detailed assessment of by-
product gypsum production and market potential. Data will be obtained on
the development, design, and operation of leading processes, flow diagrams,
and material balances, i.e., Chiyoda, carbon absorption, and CaSO, oxida-
tion. Detailed investment and operating cost estimates will be prepared for
two of these processes. The current sources, production, and market
statistics for gypsum will also be presented. In addition, a comprehensive
assessment will be made for marketing the gypsum in wallboard outlets in
the United States. The most likely candidate power plants will be defined,
and expected transportation costs and possible net sales revenue will be
projected for the selected plants.
Work on process evaluation has begun, and selection of two
processes is expected shortly. Detailed analysis of the marketing data is
scheduled to begin in July 1976, with completion of the project in late 1976.
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5.4 ALTERNATIVE FGC WASTE DISPOSAL METHODS
The intent of work in this area is to assess the potential and
the environmental impacts associated with disposal of FGC wastes in mines
and in shallow and deep ocean sites.
5.4.1 Evaluation of Alternative FGC Waste Disposal
Sites (A. D. Little)
FGC waste disposal alternatives to ponding and landfilling
are being evaluated in this program being conducted by A. D. Little, Inc.,
Cambridge, Massachusetts. Initially, an assessment will be made of the
potential environmental impact of the disposal of untreated and chemically
treated FGC wastes in deep and surface mines and in the ocean. State and
federal regulatory restrictions applicable to such disposal will be identified
and assessed with regard to their adequacy in protecting the environment,
and criteria will be defined as appropriate. Realistic approaches, if any,
for implementing ocean or mine disposal systems within regulatory and
other defined constraints will be identified. Although environmental effects
and operational safety are the primary considerations, an assessment will
also be made of the costs of promising disposal systems including conceptual
designs. Recommendations will include plans for a second phase that
includes subscale pilot demonstrations of such a size that design data for
full-scale operations can be obtained.
The first phase is an eight-month project that was initiated
in late July 1975. Availability of a final report is planned subsequent
to completion in April 1976.
One of the significant project tasks is to identify and character-
ize the physical and chemical properties of both untreated and treated FGC
waste by location, process type, and potential quantity produced. As of
December 31, a compilation of FGC waste data was completed. Sources were
primarily from the U. S. Army WES and The Aerospace Corporation work.
Assessment of the impacts of the waste disposal was also begun. Information
on properties of FGC wastes unique to the disposal in the marine and mine
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environment is not available, and some experiments may be conducted to
obtain these data prior to defining Phase II conditions for this program.
These include such data as sulfite ion oxidation rates in sea water and the
impact of sulfite oxidation on dissolved oxygen concentrations. Assumptions
on the rates of oxidation suggest a basis for some concern over potential
short-term oxygen depletion in situations involving concentrated dumping of
CaSO~-rich sludges and the toxicity of the sulfite itself.
In addition to the determination of the physical fate of wastes,
the biological impact potentials are being assessed. The effect of trace
contaminants is also being evaluated. This effort will be based on the
characterization of differing chemical backgrounds in potential dumpsite
environments using recently acquired field data from the East and Gulf
Coast sampling programs.
The project includes a review of ocean monitoring and polic-
ing policy, as well as navigational aids, technology monitoring, biological
parameters, and equipment monitoring. Costs of a typical monitoring and
policing policy are being included, together with costs of a typical monitor-
ing cruise and the ensuing laboratory analyses.
In the assessment of the disposal of sludges in the mines, a
set of assumptions was developed for each general mine case in order to
provide a basis for quantifying, as much as possible, the potential impact
of the sludge under different conditions. Assumptions included the nature
of aquifers, groundwater characteristics, hydraulic gradients, and the
effect of a variety of placement techniques on the physical properties of the
sludge. These assumptions are being used to evaluate the technical and
environmental impacts of sludge disposal options.
An evaluation of federal and state regulations related to
sludge disposal is being conducted. An inventory of federal laws relative to
mine disposal was made, and an assessment of their adequacy is under way.
The use of FGC wastes as a soil amendment is also being reviewed. When
compared with lime and sewage sludge, the use of FGC wastes does not
appear to be promising.
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Both the ocean and mine disposal assessments are scheduled
for completion early in calendar year 1976. The results of the assessment
work will be used as the basis for completing a conceptual system design
for promising disposal options.
5.5 NEW FCC WASTE UTILIZATION METHODS
Utilization projects include development of (1) a process for
FGC waste conversion (to sulfur and calcium carbonate), (2) pilot studies
of fertilizer production (using the waste as a filler material and a source
of sulfur), (3) use of FGD gypsum in portland cement manufacture, and
(4) FGC waste beneficiation studies.
5.5.1 Lime and Limestone Scrubbing Waste Conversion
Pilot Studies (Pullman Kellogg)
A study is planned to evaluate the Kel-S process, which
produces elemental sulfur as an alternative to throwaway disposal of FGD
lime and limestone wastes. The project will be approximately 11 months
in duration. It involves a cost-shared contract currently under negotiation
with Pullman Kellogg, Houston, Texas, to conduct pilot-plant scale evalua-
tion of several key steps in the Kel-S process.
The process converts FGD wastes obtained from lime and
limestone scrubbers to elemental sulfur. It also produces calcium car-
bonate, CaCO,, which can be recycled in the SO- scrubbing system. FGD
waste will be reduced to calcium sulfide, CaS, in a continuously rotating
kiln. The CaS is then reacted with hydrogen sulfide, H2S, which is avail-
able from the recovery unit and forms calcium hydrosulfide, Ca(HS)_. The
Ca(HS) is dissolved in water and the solution is filtered. The cycle is closed
L*
by reaction of the Ca(HS)~ with CO?-rich gas available from the drying kiln.
The reaction with CO forms H~S and also CaCO^, which is precipitated.
Half of the H~S is returned to react with the CaS, and the remainder is con-
verted to elemental sulfur in a conventional Glaus unit. The CaCO, is
recycled to the scrubber system.
-120-
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It is expected that design and operating data will be obtained
to permit scaleup of the process to a prototype integrated system that can
be operated in conjunction with a power plant FGC system.
5.5.2 Fertilizer Production Using Lime and Limestone
Scrubbing Wastes (TVA)
The use of lime and limestone scrubbing wastes as a filler
material and source of sulfur in granular fertilizers is being evaluated.
The work is being performed by TVA, Office of Agricultural and Chemical
Development, Muscle Shoals, Alabama, as part of an interagency agreement
directed toward the evaluation of the utilization or disposal of FGC wastes.
Results from previous TVA bench-scale laboratory tests and
small field plot application tests with rye grass were sufficiently promising to
warrant additional work on a pilot-plant production basis. In addition to the
pilot plant evaluation, the technical, economic, and environmental impacts
will be studied as a result of producing and using granular fertilizer from
scrubber wastes. Specific tasks include (1) determining compatibility fac-
tors involved in mixing and storing the fertilizer with conventional fertilizer,
(2) conducting of field plot tests with the pilot-plant produced fertilizer,
and (3) assessing the effects of trace and toxic materials relative to those
in conventional fertilizers. Marketing studies of the scrubber-waste based
fertilizer are also planned.
The pilot plant production and the storage compatibility tests
are scheduled for completion in 1976. Long-term agronomic testing is planned
to begin in 1977 and extend through 1979.
A flow diagram of the pilot plant process is shown in Figure 21.
Plant production is rated at 3000 Ib/hr. Efforts through the end of 1975 in-
volve modifications to the existing pilot plant to handle the FGC waste, in-
cluding the installation of a pump, waste storage tank, and agitators.
Initial pilot plant tests were conducted, using sludge produced
at the 1-MW limestone pilot unit located at the TVA Colbert Steam Plant.
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PHOSPHORIC ACID
TO STACK
ro
i
GAS
TREATMENT
SYSTEM
AMMONIATOR
GRANULATOR
Figure 21. Process for the production of solid granular fertilizer
material from scrubber sludge
-------
Introduction of sludge, phosphoric acid, and ammonia into ths preneutralizer
resulted in severe foaming. The preneutralizer was then operated with only
the acid and ammonia in the conventional ammonium phosphate mode. The
sludge and the ammonium phosphate from the preneutralizer were then fed to
the drum granulator. A number of sludge feed rates were tried, and those
resulting in acceptable granulation rates have been defined.
A specially constructed preneutralizer to eliminate the prob-
lems encountered is planned. It includes alternative methods and locations
for adding the sludge, acid and ammonia. Improved agitation and foam
breaking methods are planned. Development of the preneutralizer modifi-
cations is important so that the heat of reaction can be effectively utilized
in reducing the solids content of the incoming sludge.
Development of the granulation and processing steps is
planned after satisfactory operation of the preneutralizer is obtained.
5. 5. 3 Use of FGC Gypsum in Portland Cement
Manufacture [South Carolina Public Service
Authority (SCPSA)]
Laboratory and operational equipment tests will be conducted
by the Santee Portland Cement Corporation with SCPSA to determine the
acceptable range of variability in the FGD gypsum quality, as well as other
potential operational problems. Other uses of FGD gypsum, such as road
base material, will be tested in the laboratory and under operational condi-
tions. In addition, a full-scale evaluation of the process is planned utilizing
the FGD equipment of a utility coal-fired power plant and a portland cement
manufacturing facility.
5.5.4 FGD Waste and Fly Ash Beneficiation Studies (TRW)
A conceptual design and cost study of a TRW proprietary pro-
cess that produces sulfur, alumina, and dicalcium silicate is planned. Poten-
tial uses of the alumina and dicalcium silicate are in the production of alumi-
num and cement, respectively. If the economics are favorable, bench-scale
laboratory tests will be planned to define the range of operating conditions
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for each of the significant processing steps and to determine probable yields
and purity of products. If process viability is established, pilot-plant scale
testing may then be performed to obtain design data for full-scale equipment.
5.6 IMPROVEMENT OF OVERALL POWER PLANT
WATER USE
The program to improve power plant water use is a single
project to study methods to minimize water losses and to recycle or reuse
waste water discharges.
5. 6. 1 Assess and Demonstrate Power Plant Water
Recycle and Reuse (Radian)
A technical and economic study is being conducted by Radian,
Inc., Austin, Texas, to assess the options for the recycle or reuse and
treatment of water for coal-fired power plants. The primary objective is
to define ways to minimize water consumption and the discharges of waste
water. The basic program will be 13 months in duration.
Computer models are being prepared to simulate the existing
plant operations. With these models, predictions of plant operations will be
obtained and compared to actual plant operations. This method will be used
to verify the validity of the models for use in the technical assessment of
various water recycle and reuse options. The most attractive options for
each of the plants will be selected, and engineering cost estimates will be
made for each plant. The estimates will include capital, installation, and
operating costs.
•Three plants have been selected for water system characteri-
zation and analysis, and the addition of two other plants is planned. On the
basis of screening criteria of location, availability, site characteristics,
and timing, the three plants selected were the Four Corners Plant of Arizona
Public Service, the Public Service of Colorado Comanche plant, and the
Bower plant of Georgia Power Company. These were chosen to represent
regions in the United States where water recycle or reuse is advantageous
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due to high water costs, limited availability, or treatment and disposal
problems. The basic characteristics of the plants are shown in Table 25.
Samples from each of the three plants have been collected
and analyzed. Preliminary simulation schemes for modeling the existing
plant processes and operations have been completed, and the data input will
be finalized after completion of the laboratory analyses from the sampling
trips.
In order to establish the scaling potential criteria of CaCO,
and Mg(OHL for use in the water recycle and reuse computer model simula-
tions, laboratory experiments have been conducted. In these experiments,
steady-state precipitation rates as a function of solution super saturation
were conducted with CaCO, and Mg(OH)_.
In support of the model analyses, experiments are required
to characterize ash dissolution and to determine the mass transfer of CO-
d
from the atmosphere to process slurries and ponded ash. Thereafter,
simulations of existing plant operation to validate the model will begin.
Precipitation kinetics experiments required to define the
critical relative saturations for CaCO trusts are complete, and those for
Mg(OH)_ are in progress. Upon completion of this task and characterization
of ash to determine CO~ mass transfer between the atmosphere and process
vessels and ash ponds, the simulations of existing plant operations and'
validation of the model will begin.
The technical assessment will be performed on the basis of
evaluating various water.recycle and reuse options and strategies for each
of the representative plants on the design or design installation, operability,
and treatment effectiveness. It is expected that the sensitivity to the various
parameters will be determined and illustrated. Rough cost estimates of the
most attractive viable options as defined by the technical assessment will
then be made, and the overall optimum recycle or reuse option based on
technical and economic considerations will be defined. The results of the
study including recommendations for each plant, further assessments,
testing, or field demonstrations will be included in the final report.
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Table 25. PLANTS SELECTED FOR WATER RECYCLE AND REUSE STUDY'
Utility
Arizona Public
Service
Public Service of
Colorado
Georgia Power Co.
Station
Four Corners,
Comanche
Bowen
Location
Farmington,
New Mexico
Pueblo ,
Colorado
Taylorsville,
Georgia
Capacity, MW
1600
350
1595f
Type of
Cooling0
CP
WCT
WCT
Ash
Handling0
WSB
WSF
WSB
WSB
WSF
Particle,
Control
Cyclones,
ESP,
venturi
ESP
ESP
so2
Control6 .
. uc . :
None
None
I
h^t
ro
i
Reference 20.
Wet cooling tower (WCT); cooling pond (CP).
°Wet sluicing of bottom ash (WSB); wet sluicing of fly ash (WSF).
Electrostatic precipitator (ESP).
eUnder construction (UC).
Plant capacity as reported in Federal Power Commission (FPC) Form 67 data sheet;
present capacity is 3200 MW (4 units).
-------
5.7 EPA IN-HOUSE RESEARCH
EPA is conducting pilot plant experiments on forced oxidation
19
of FGD scrubber sludge. Primary objectives of the project include com-
plete limestone utilization, maximum oxidation efficiency of calcium sulfite
to calcium sulfate without catalysts or mechanical means, and improved
oxidized slurry settling rates. The second and third objectives are related
to determining the feasibility of forming usable gypsum as a by-product from
the FGD process.
In order to assess the characteristics of the gypsum from a
utilization standpoint or its suitability as a disposal product without the need
for further chemical treatment, Aerospace is conducting chemical and
physical characterization tests of oxidized wastes formed under a variety
of conditions:
a. Limestone scrubbing without fly ash
b. Limestone with fly ash
c. Effect of chloride ion without fly ash
d. Lime scrubbing without fly ash
The laboratory study has been initiated recently on oxidized
samples from conditions a and b. It is expected that results of these analyses
will be reported in the next annual report.
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SECTION VI
UNIVERSITY-RELATED RESEARCH AND DEVELOPMENT
Several universities were identified as planning or conducting
research and development (R & D) work in the flue gas desulfurization (FGD)
waste disposal and utilization areas.
6. 1 AUBURN UNIVERSITY
Auburn University, Auburn, Alabama, which has conducted
work in dewatering of phosphate slimes, is being funded by EPA to perform
dewatering experiments and to define dewatering equipment design criteria
for flue gas cleaning (FGC) wastes. This project is discussed in
Section 5.2.4.
6.2 ILLINOIS INSTITUTE OF TECHNOLOGY
Experimental work is being conducted at Illinois Institute of
Technology (IIT), Chicago, Illinois, on a process that utilizes sulfur oxide
from flue gas to form a superphosphate fertilizer.
Initial feasibility work was conducted by Dr. R. Peck and
Mr. L. Pircon at IIT. Subsequently, they received a grant from the State
of Illinois Institute of Environmental Quality to demonstrate certain principles
involved in the process. Work on the grant is scheduled for completion in
June 1976.
A key element in the process involves the contacting of SO_
from the gases and acidulating phosphate rock in a heterogeneous phase
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reactor to form a superphosphate fertilizer. Ammoniation can be
included to form a granular product. The fly ash formed in the combustion
process is not removed upstream of the process and is included in the
fertilizer. Detailed information on the process will not be available until
patent secrecy limitations are lifted.
Hot house experiments have been performed by the State of
Illinois, and field plant studies are planned. Plans for demonstrating the
process in utility power plant units of up to 150 MW in size are in the
formative stages.
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SECTION VII
INDUSTRIAL RESEARCH AND DEVELOPMENT AND
OPERATIONAL APPLICATIONS
This section summarizes the work performed by various
industrial organizations in the chemical treatment of flue gas desulfurization
(FGD) wastes. The operational applications of FGD treatment and disposal
are also summarized.
7. 1 RESEARCH AND DEVELOPMENT BY UTILITIES
i
7.1.1 Ontario Hydro22"24
Ontario Hydro, Toronto, Canada, has been involved in the
study of FGD systems for several years and has studied a broad range of
22-24
conditions dealing with the disposal of flue gas cleaning (FGC) waste.
At that time they were burning eastern United States coal exclusively, from
Pennsylvania and West Virginia. As a result of long-range coal supply
considerations, the use of low-sulfur western Canadian coal is being increased.
Currently, emission standards are being met by the use of a blend of the two
types or by intermittent use of low-sulfur coal. Since it is expected that this
strategy will be utilized in the foreseeable future, the research and develop-
ment (R&D) activity of Ontario Hydro in FGD scrubbing and disposal has been
essentially concluded.
Prior to this decision, FGD research at Ontario Hydro was
broad in scope and actively pursued. Laboratory programs evaluating
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various chemical additives and their effects on the physical properties of
treated waste are reported in Reference 23. Table 26 is representative of
the mixtures tested and reports the effect on the compactability and per-
meability of different mix proportions.
In the area of sludge dewatering, the effect of polyelectrolytes
on settling, the mechanics involved during the thickening, and the methods
of improving the efficiencies of the thickener have been studied. At the pilot
scale, thickener-vacuum filtration techniques and a solid bowl continuous
centrifuge to determine efficiencies and for comparison purposes have been
evaluated. The results of this work will be published in the near future in
24
the Ontario Hydro Research Quarterly.
7.1.2 Southern California Edison
7.1.2.1 Highgrove Plant22
Southern California Edison (SCE) is operating a 10-MW lime
scrubber at its Highgrove plant to evaluate the horizontal scrubber
efficiency when using high-sulfur fuel oil. The SO_ content in the flue gas
is high, about 2000 ppm. The sludge is composed mainly of calcium sulfite,
approximately 90 percent CaSO_, which is the opposite of what was reported
at Mohave (Section 7. 1. 2. 2). SCE has tested and developed a process to
oxidize the calcium sulfite to calcium sulfate with air oxidation and pH con-
trol that yields 97 percent oxidation.
7.1.2.2 Mohave Plant22' 25
Much of the SCE full-scale sludge-disposal-related research
was carried out at the Mohave scrubber installation, Clark County, Nevada
and completed in 1975. The flue gas inlet concentration was low in SO^,
and the sludge was composed mainly of calcium sulfate. It was reported
that the Mohave sludge dewatered well (60 to 70 percent solids) and was
fairly stable without further treatment.
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Table 26. MIX CONSISTENCIES WITH VARIOUS ADDITIVES FOR LAKEVIEW
GAS SCRUBBER SLUDGE CONTAINING 65 PERCENT SOLIDS
Mix Proportions
Consistency of Mix
Remarks on Compactability
oo
w
i
Sludge + 5% Lime
Sludge + 10% Lime
Sludge + 5% Cementa
Sludge + 10% Cement
Sludge + 15% Cement
Sludge + 52% Fly Ash
Sludge + 39% Fly Ash + 5% Cement
Sludge + 39% Fly Ash + 15% Cement
Sludge + 65% Fly Ash
Sludge + 15% lime
Sludge + 39% Fly Ash + 5% LimeC ,
Sludge + 65% Fly Ash + 5% Cement
Sludge -I- 65% Fly Ash + 15% Cement
Sludge + 65% Fly Ash + 5% Lime
Sludge + 39% Fly Ash + 15% Lime
Sludge + 65% Fly Ash + .15% Lime
Soft and wet
Firm and wet
Firm and moist
Firm and dry
Powdery and dry
Both lime mixes were too wet
to compact, even after 1 week
of retention. The cement mixes
were too wet to compact ini-
tially but were compactable
after 24 hours.
All mixes too wet, although
some only slightly, causing
some slumping of specimens
after removal from mold
Ideal mix combinations for
compaction
Slightly drier than above mixes,
but compactable
Too dry and powdery for proper
compaction
Condition Permeability, Coefficient, cm/sec
a
b
c
Untreated
(77% Solids)
7.6 x 10"
7.2 x 10
5.6 X 10
4.0 X 10
9.0 X 10
-6
-6
-6
-6
-------
Dewatering sludge was accomplished in a thickener where both
cationic and anionic flocculents were added, one for the fly ash fraction and
the other for sulfur products. After settling, the underflow was subjected
to chemical treatment. SCE contracted with Dravo and IU Conversion
Systems-(IUCS) to treat the sludge.
The Dravo process added Calciloxf^ to the thickener underflow;
at times, lime was added for pH control. The resultant mixture was placed
in an unlined pond for hardening.
IUCS treated the total annual output from the Mohave Unit
No. -1A, 167-MW scrubber system. The material produced, Poz-O-Tec®,
25
was used in a number of synthetic aggregate-related applications:
a. As a landfill in the construction of a housing project;
a total of 25,000 tons were placed to reclaim landi
b. In the construction of a parking lot
c. As road base by the Mohave County Department of Highways
in the construction of Bullhead City streets and county
roads. The base was capped with an oil and chip surface
course
SCE is not expected to use a chemical treatment process at
-Mdhave'for sludge disposal since the calcium sulfate sludge is considered
stable, and enough land area exists at the Mohave site to accommodate all
the sludge produced for the life of the plant, which is estimated to be
4000 acre-ft.
22
7.1.2.3 Applications
S.CE hopes to develop a market for the oxidized sludge in the
wallboard industry and will probably make a 50-ton full-scale wallboard test
with Kaiser Cement Company.
Another interest of SCE is to utilize oxidized sludge for agri-
cultural purposes. Gypsum promotes growth of denitrifying bacteria in soils
containing a high concentration of nitrates. It has also been found to promote
the growth of alfalfa and peanuts and is a useful additive for sulfur-deficient
soil.
-134-
-------
Other testing has included dewatering studies using thickeners,
filters, and centrifuges and drying studies using spray dryers, thermal disc
dryers, and kiln dryers. Pelletizing has also been studied.
7.1.3 Southern Services '
As a result of testing three FGD processes at Plant Scholz
(20-MW each), Southern Services, Chattahoochee, Florida, has become
involved in both disposal and utilization studies of waste products from the
Chiyoda gypsum process. Studies of the chemical treatment of sludge from
the Combustion Equipment Associates/Arthur D. Little, Inc. (CEA/ADL)
dual-alkali process is also being performed.
Southern Services has conducted bench-scale testing and has
to determined the suitability of using Chiyoda gypsum in wallboard manufac-
turing. Southern Services is also interested in the use of this gypsum as
a cement setting retardant and in agricultural applications.
The gypsum produced at the Scholz plant consists almost
entirely of calcium sulfate dihydrate (CaSO. • 2H_O). It has been re-
TT Lf
ported as easy to dewater by centrifuging, and the solids content is typically
80 to 85 percent. The gypsum is composed of 28 percent sand size, 66 per-
cent silt size, and 6 percent clay size material, according to the MIT
classification system.
The major portion of the gypsum particles ranged in size
from 0.01 to 0. 1 mm. As a result of consolidation tests, it was reported
that landfilled Chiyoda gypsum could support significant loads without appre-
ciable settlement. However, loads subject to vibration could not be placed
on a gypsum landfill because the gypsum tends to liquefy with vibration if the
water content of the gypsum does not remain low (approximately 15 percent
or less). A range of permeabilities was calculated from the consolidation
tests to be 10" to 10~ cm/sec. In Atterberg limit testing it was found that
the Chiyoda gypsum is nonplastic and that it will liquefy when wet and sub-
jected to vibration.
Currently, the gypsum is disposed of in a lined pond equipped
with an underdrain. Rain water, percolated through the gypsum, passes through
-135-
-------
I
the underdrain and is routed to the ash pond. The water from the underdrain
has been sampled monthly since July 1975, and the results of the analyses
are reported in Reference 26 (Table 27). In general, with the possible ex-
ception of total dissolved solids (TDS), it appears that the leachate poses no
water quality problems. Trace element concentrating are low because most
of the trace contaminants in the flue gas are removed in the prescrubber. The
liquid waste from the prescrubber is neutralized with limestone and routed
to a lined settling pond where fly ash, gypsum, unreacted limestone, and
Fe(OH), (catalyst from mother liquor bleed) settle out.
If TDS in the gypsum leachate poses a problem at a full-scale
installation, leaching could be minimized by lining the disposal area or
treating the gypsum. Studies are under way at the Scholz plant to test usage
of compacted gypsum layer as an alternative to conventional liners. Approxi-
mately 1 ft of gypsum will be placed in a 20 x 50 ft level area and will be
compacted with conventional compaction equipment. Core samples of the
compacted layer will be taken, and their permeability will be determined in
the laboratory. Approximately three more feet of gypsum will be placed on
top of the compacted layer, and the gypsum and gypsum liner will be allowed
to weather. Core samples will be taken periodically to determine if liner
permeability varies with time.
The overflow from the settling pond has been sampled and
analyzed monthly since July 1975. The analyses, as shown in Table 27,
include trace elements as well as major constituents. Concentrations of
TDS, iron, mercury, and fluoride in excess of state water quality standards
for receiving waters have been measured in the settling pond overflow.
Selenium concentrations in excess of U.S. Public Health Service (USPHS)
drinking water standards have also been measured in this overflow. How-
ever, the settling pond overflow is routed to the Scholz plant ash pond, which
ultimately discharges to the Apalachicola River where state water quality
standards are applicable. There have been no violations of state water
quality standards, as determined by monthly monitoring of the ash pond
overflow.
-136-
-------
Table 27. EFFLUENT ANALYSES FROM A LINED LIQUID-
WASTE SETTLING PONDa
Parameter
TDS, mg/|
Total Suspended Solids,
mg/i
PH
Conductivity, |j.mhos/cm
Temperature, °F
Total Calcium, mg/S. as Ca
Total Magnesium, mg/S
as Mg
Total Sodium, mg/S. as Na
Total Potassium, mg/S. as K
Total Hardness, mg/S. as
CaC03
Total Phosphorus, mg/S.
as P
Dissolved Silica, mg/S. as
Si02
Sulfate, mg/i as SO
Sulfite, mg/S. as SO~
Carbonate, mg/S. as
CaC03
Bicarbonate, mg/S. as
CaCO
Liquid Purge
Settling Pond
Overflow
2000 to 4994°
6 to 393e
2.3 to 7. 5C
3050 to 6700
47 to 85
330 to 1100
39 to 246
28 to 65
0.85 to 2.93
1093 to 3360
<0.01 to 0.036
12 to 31
1160 to 2750f
<1
0
0 to 38
,
Gypsum Pond
Underdrain
2250 to 2754°
<1 to 4
6.8 to 7.2
2000 to 2670
55 to 88
540 to 644
14 to 87
12 to 67
0.47 to 1.65
1406 to 1830
<0.01
1.5 to 2.3
1370 to I650f
<1
0
35 to 44
State of Florida
Water Quality
Standards"
500d
-
6 to 8.5
500
-
-
-
-
-
-
- •
'
—
OJ
(Continued)
-------
Table 27. EFFLUENT ANALYSES FROM A LINED LIQUID-
WASTE SETTLING PONDa (Continued)
Parameter
Liquid Purge
Settling Pond
Overflow
Gypsum Pond
Underdrain
State of Florida
Water Quality
Standards*3
00
I
Hydroxide, mg/j? as CaCO_
Chloride, mg/I as Cl
Carbon Dioxide, mg/i as
co2
Total Acidity, mg/f as
CaCO3
Color, standard units
Turbidity, NTU
Total Aluminum, mg/jf as Al
Total Arsenic, mg/i as As
Total Cadmium, mg/£ as Cd
Total Chromium, mg/j? as
Total Copper, mg/£ as Cu
Total Iron, mg/i as Fe
Total Lead, mg/Jl as Pb
Total Manganese, mg/S.
as Mn
Total Mercury, mg/£ as Hg
Total Nickel, mg/i as Ni
Total Selenium, mg/S. as Se
Total Zinc, mg/i as Zn
Oil and Grease, mg/£
0
51 to 138
25 to 970
0 to 1080
0.5 to 13
. 4.2 to 92.0°
2. 10 to 4. 80
<0.01
<0.01
<0.01 to 0.04
0.06 to 0.60°
0.54 to 109.0°
<0.01
0. 17 to 1.08h
<0.0002 to 0.0068C
0.02 to 0. 15
0.016 to 0.
0.26 to 1.3
0
2.3 to 9. 1
4. 8 to 12.0
0
0. 5 to 8
0. 18 to 1.6
<0.05 to 0.24
<0.01
<0.01
<0.01
<0.01
0.019 to 0. 17
<0.01
<0.01 to 0.32h
<0.0002 to 0.0004
__«CO. 01
<0.002 to 0.04
<0.01
250
50
0.05
0.05g
0.5
0.3
0.05
ND1
1.0
15
(Continued)
-------
Table 27. EFFLUENT ANALYSES FROM A LINED LIQUID -
WASTE SETTLING PONDa (Continued)
Parameter
Nitrate, mg/i as N
Chemical Oxygen Demand,
mg/j?
Fluoride, mg/j£ as F
Boron, mg/J! as B
Liquid Purge
Settling Pond
Overflow
20 to 105k
<1 to 11
4.2 to 27°
1.0 to 4..6m
Gypsum Pond
Underdrain
4 to 43
< 1 to 4.9
0.54 to 0.94
<0. 1
State of Florida
Water Quality
Standards13
-
1.4 to 1 . 61
-
oo
^O
i
aJuly through December 1975.
Applicable to receiving waters only after reasonable opportunity for mixing with wastes has
been afforded.
Q
These values would violate water quality standards if mixing were not taken into account.
As a monthly average: 1000 mg/j? instantaneous.
£
The EPA effluent guidelines for steam electric power plants for total suspended solids is
100 mg/2 maximum for any one day and 30 mg/jg for a monthly average.
The USPHS 1962 drinking water standard for sulfate is 250 mg/£.
°For total chromium in the effluent discharge, the standard is 1.0 mg/#;
for hexavalent chromium in the effluent discharge, the standard is 0.5 mg/i.
The USPHS 1962 drinking water standard for manganese is 0.05 mg/£.
None detectable (for practical purposes at this time, ND = <0.0002 mg/i).
JThe USPHS 1962 drinking water standard for selenium is 0.01 mg/^.
k
The USPHS 1962 drinking water standard for nitrate is 45 mg/i.
1 Applicable only to waters used for sources of Class 1 water supply; for other waters, the
standard for fluoride is 10 mg/j!.
The EPA proposed water quality criteria for public water supply intake (October 1973) for
m
boron is 1.0 mg/£.
-------
For full-scale applications, treatment or reduction of the
liquid waste may be required by both state and federal regulations. Treat-
ment could be accomplished if the volume of waste were reduced by evapora-
tion. It has been reported that consideration is currently being given by the
EPA to demonstrating vapor compression evaporation on the Chiyoda liquid
waste at the Scholz plant. Plans to reduce water consumption and the liquid
waste stream are being implemented as an approach to a closed loop.
Chiyoda gypsum has been laboratory-tested by a wallboard
company and appears to be suitable for wallboard manufacture through small-
scale tests. A demonstration test is planned, using 100 tons of Chiyoda
gypsum at a wallboard plant in Jacksonville, Florida.
The suitability of Chiyoda gypsum for cement production is
being tested by a cement company. Preliminary reports indicate that Chiyoda
gypsum can be used as a cement setting retardant.
Agricultural use of gypsum as a calcium source for peanuts is
fairly well established in the southeastern region of the United States. Testing
the suitability of the Chiyoda gypsum for agriculture began in December 1975
with soil incubation studies at the University of Florida Agricultural Research
Center, Quincy, Florida. The first month of soil incubation indicates that
application rates of up to 20 tons of Chiyoda gypsum per acre of soil will be
feasible. The results of plant response tests will soon be available because
test plants (peanuts and soybeans) were planted in soil-gypsum mixtures in
early February 1976.
Chemical treatment is also being performed on the sludge from
the CEA/ADL dual-alkali process. Fly ash, portland cement, and quicklime
are being added to the sludge in various concentrations and combinations so
as to define the more promising fixation method. IUCS and Amax have also
22
had an opportunity to test their processes on the sludge material.
Southern Services also plans to conduct economic and engineering
evaluations for large-scale sludge-handling systems, such as pumping and con-
veyors. Plans have been made for prototype and demonstration testing of the
phases of study that prove to be promising.
-140-
-------
7.1.4 Southwestern Public Service Company
Southwestern Public Service Company, together with Combustion
Engineering, is also involved in studying the feasibility of producing structural
landfill material from sludge by mixing scrubber solids with local soils found
22
around the plant site. Tests demonstrated that mixtures of soil and sludge
could produce a landfill material with significant load-bearing strength. This
type or method of approach is reported to be more promising in areas that
have a more arid climate.
7.1.5 Electrical Power Research Institute
As a result of its assessment of the complexity and site-
specificity of handling and disposing of lime and limestone scrubber, the
Electrical Power Research Institute (EPRI) has defined a program which
addresses these problems. The projects specifically related to FGD treat-
ment and disposal are covered under the general objective to develop a
reliable design basis of lime and limestone scrubbing. The proposed treat-
ment and disposal projects are enumerated in Table 28. Although detailed
descriptions of the various tasks were not provided, it appears that four or
five projects (Items 1 and 3 through 6 of Table 28) lie in areas of interest
similar to the EPA FGC Waste and Water Program. It is anticipated
that the EPA program information will be used wherever possible. It has
been reported that a memorandum of understanding has been signed by EPRI
EPA calling for cooperation in R & D in areas of mutual interest relating
to the environmental aspects of producing, transmitting, distributing,
45
utilizing, and conserving electric power.
27
7.1.6 Commonwealth Edison Company
A project to characterize the sludge produced from the Com-
monwealth Edison Will County Unit No. 1, Joliet, Illinois, limestone scrubber
is reported in Reference 27. Laboratory studies were conducted on treated
sludge admixtures to determine the following:
a. Compressive strength
-141-
-------
Table 28. EPRI SOX CONTROL PROGRAM: FGD
TREATMENT AND DISPOSAL
1. Evaluate FGD Process Control Capability
2. Low Sulfur and Alkaline Ash Scrubbing Characterization
3. Evaluation of Sludge Dewatering Processes
4. Sludge Composition and Leachability
5. Sludge Fixation Chemistry Guidelines
6. Chemistry Modifications to Improve Reliability and Cost
7. Hardware Modification to Improve Reliability and Cost
8. Diagnostic Support, Eastern Coal
9. Diagnostic Support, Western Coal
-142-
-------
b. Permeability
c. Solubility
d. Dissolved solids in sludge supernatant
Considerable data were reported in each category, including
properties as a function of curing temperature. Significant and typical re-
sults are summarized below.
7. 1.6. 1 Compressive Strength < .
Over 270 test series were made of various sludge admixture
combinations and curing temperatures. Samples were cured in 100 percent
relative humidity at 4.4° C (44° F), 22°C(72°F), and 50 °C (122° F). Some
significant findings of the tests were that the addition of pulverized lime and
fly ash or portland cement and fly ash resulted in the most economical and
satisfactory solidification of sulfate sludge. Figure 22 illustrates some of
the results obtained.
At low temperatures .(4.4° C), the laboratory sludge additive
mixtures did not harden to any significant degree. Some field mix samples
hardened; however, these samples were at room temperature for four days
prior to being placed at 5° C for further curing. Curing at 22° C resulted in
strengths of about 20 to 25 percent lower than corresponding samples cured
at 50°C.
7.1.6.2 Permeability
I Permeability coefficients of samples ranged from 10" to
10" cm/sec. The permeability was found to be dependent on the solids and
additive contents of the sludge. The effect of these parameters is shown in
Figure 23. Strength and permeability are generally related to the porosity of
a material. The strength and permeability of the hardened sludge as a func-
o
tion of the compressive strengths required for a permeability factor of 10
and 10" cm/sec are approximately 650 psi and 250 psi, respectively.
-143-
-------
2000
1500
1000
SAMPLES CURED
AT'50°C
l/V
CO
o
o
500
1 o
D
A
PARTS BY WEIGHT
SLUDGE
' 10
10
10
PULVERIZED
LIME.
1
0.75
0.5
FLY ASH
2.
1.5
I'.O
30 40 50:
SOLIDS IN SULFATE" SLUDGE,, %'•
Figure 22., Sixty.-day cqmpressiive' strengtli^of sulfate
sludge, pulverized! lime, and fly ash
mixtures
-144-
-------
10
-10
of 10
o
o
u_
>-
I
CO
-9
8
-7
°- 10
SAMPLfS CURED
10 DAYS AT 50°C
30 40 50
SOLIDS IN SULFATE SLUDGE, %
O
D
A
PARTS BY WEIGHT
SLUDGE
10
10
10
PULVERIZED
LIME
1
0.75
0.5
FLY ASH
2
1.5
1
60
Figure 23. Permeability of sulfate sludge, pulverized
lime, and fly ash mixtures
-145-
-------
10
-10
o:
O
o
v-8
00
<
Od
io
7
"7
LOWER LIMIT
BETWEEN
COMPRESIVE
STRENGTH AND
PERMEABILITY
O SULFATE SLUDGE, PULVERIZED LINE,
AND FLY ASH
D SULFATE SLUDGE, TYPE I CEMENT,
AND FLY ASH
A SULFATE SLUDGE, HYDRATED LIME,
AND FLY ASH
I
500 1000 1500
COMPRESSIVE STRENGTH, psi
Figure 24. Relationship between compressive
strength and permeability
-146-
-------
7.1.6.3 Solubility
Solubility of the sludge was characterized as a function of the
sulfate concentration in the water which was contacted with sludge. Crushed
solidified sludge was used to simulate a severe leaching environment. Two
sizes of crushed solidified sludge were used: 0. 187 X 0.094 in. (4x8 mesh)
and 0.012 X 0.006 in. (50 X 100 mesh). Water poured through a filter bed of
the solidified sludge was collected and analyzed. Contact time between the
water and sludge varied from 5 to 60 min. A series of seven consecutive
washings or leachings were analyzed. Results of this test series are given
in Tables 29 and 30.
Supernatant of the untreated sludge contained 1640 mg/t of
SO. while the highest average SO . content for seven consecutive washings
of solidified sludge was 177 mg/2 with a 50 X 100 mesh sample in contact
with water for 60 min/wash (Table 29). The results show that treatment of
the sludge significantly reduces its SO . solubility even when the solidified
sludge is in powder form.
The SO ~ content decreased with increased leaching of the
sludge when the first leachate contained over 100 mg/£ (Table 30). However,
even after the first washing of the 50 x 100 mesh, 60-min contact time sample,
the wash water contained only 428 mg/t SO. .
The SO." content of the wash water increased with increased
contact time, e.g. , from 26 mg/f. (for 3 to 5 min/wash) to 67 mg/0 (for
60 min/wash), Table 29. Generally the SO." concentration decreased with
an increase in solids content of the sludge as well as with an increase in
quantity of additives added to solidify the sludge.
A sample of 4 x 8 mesh solidified sludge (10 parts of 57 percent
solids content sludge plus 0. 5 parts pulverized lime and 1 part fly ash) was
immersed in a liter of distilled water, and aliquots were taken for SO .
analyses at time intervals of up to 60 days. These data are given in Table 31.
After 60 days, the SO ." content was 241 mg/£ . The compressive strength of
-10
this sample exceeded 1500 psi and its permeability was 3 X 10
-147-
-------
Table 29. SOLUBILITY OF SULFATE FROM TREATED SULFATE
SLUDGE MIXTURES3-
Composition,
parts by weight
Sludge
10
10
10
10
10
10
10
10
10
10
10
Pulverized
Lime
1
0.5
1
1
0. 5
1
0.5
1
1
Type I
Portland
Cement
1
0.5
Fly
Ash
Z
1
2
Z
1
2
1
2
1
2
2
Solids
in
Sludge, %
57b
57b
50
50
50
40
40
40
40
40
40
Particle
Size,
me sh
4X8
4X8
4X8
50 X 100
4X8
4X8
4X8
4X8
4X8
4X8
50 X 100
Contact Timo of
H£O and Sliidgt- per
Wash, ruin
3 to 5
3 to 5
3 to 5
~60
3 to 5
3 to 5
3 to 5
! to 5
-1. to 1
-60
~60
SO^ Content, g/t
Average of
7 Consecutive Washes
0.012
0.023
0.011
0.017
0.028
0.026
0.033
0.040
0.027
0.067
0.177
Range of
7 Consecutive Washes
0.010 to 0.014
0.020 to 0.027
0.009 to 0.013
0.014 to 0.020
0.024 to 0.031
0.022 to 0.030
0.032 to 0.034
0.038 to 0.044
0.023 to 0.035
0.039 to 0. 104
0.094 to 0.42H
00
I
All mixtures cured 10 days at 45°C and an additional 30 days at 25° C.
Sulfate content of supernatant was 1. 640 g/l.
-------
Table 30. SULFATE ANALYSES OF WATER IN CONTACT WITH
TREATED SOLIDIFIED SLUDGE
Composition,
parts by weight
Sludge
10
10
10
10
10
10
10
10
10
10
10
Pulverized
Lime
1
0. i
1
0.5
1
. 1
1
0. 5
I
1
0.5
Fly
Ash
2
1
Z.
1
2
2
2
1
2
2
1
Solids in
Sludge, %
43a
43a
50b
50b
50b
57
57
57
57
57
57
Dry
Sample
Weight, g
20
20
20
20
20
20
20
20
20
20
20
Particle
Size,
mesh
4X8
4X8
4X8
4X8
50 X 100
4X8
4X8
4X8
50 X 100
4X8
4X8
Contact
Time
of H2O and
Sludge, min
? t<> 5
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
-60
3 to 5
~60
3 to 5
3 to 5
Sulfate Content of Water in
Consecutive Washings, mn/t
,
11.6
23.4
11.9
_
18.8
30
104
33.9
428
44. i
35
2
10.0
27.4
9.4
31.2
14.0
24.4
94
33.6
188
39.4
28.4
1
14.0
23.4
9.4
28.6
15.4
23. -2
80
.33.6
177
37.6
23.2
4
11.0
20. 1
11.6
5
12.8
6
13.2
19.9 ! 21.8
12.4
12.4
24.4 25.6 26.0
17.6
22.0
64
33.3
120
3H.4
26.4
16.5
23.2
42
31.6
133
40. 5
25.0
18.8
23.4
39
32.2
102
41.2
24. 8
7
11.9
23.4
12.8
29.2
20.0
25.4(114)C
47
34.2
94
37.6
26.0
aSulfate content of supernatant was 1640 mg/f .
Sulfate content of supernatant was 1480 mg/i.
Additional wash in which the sample was exposed to H,O for ~60 min.
-------
Table 31. SULFATE CONTENT OF 100-m.g ALIQUOTS
FROM 20 g-OF 4X8 SOLIDIFIED SLUDGEa
Time of
0.5
1
2
4
8
24
7
60
Immersion
hr
hr
hr
hr
hr
hr
days
days
Sulfate Content of H_O, mg/Jt
44.2
54.5
56.0
74.0
78.8
85.6
112.0
241.0
10 parts by weight of sludge (57% solids), 0.5 parts by
weight of pulverized lime, and 1 part by weight of fly ash
in Hof HO.
-150-
-------
7. 1.6.4 TDS in Supernatant
The supernatant of the su'lfate sludges tested contained 1.480
and 1. 640 git of sulfate and a TDS content of 4. 160 g/t. . Numerous com-
pounds were added to the supernatant in an attempt to reduce its SO . and
TDS content. One compound was successful in reducing the SO . and TDS
content rapidly. This compound when added at levels of 6.25 g/t. of super-
natant reduced the TDS to approximately 0. 7 g/t. and the SO4~ content to
approximately 0.5 git .
7.2 UTILITY POWER PLANT APPLICATIONS
Full-scale experience and future plans relating to FGD
chemical treatment and disposal by utilities are summarized in Tables 32
and 33. A total of 13 units, representing 8 power plants totaling 5205 MW,
are currently committed to initiate by 1979 the chemical treatment of wastes
prior to disposal. Three stations (767 MW) are now in operation; three
others (1413 MW) will start up by the end of 1976, and seven others have made
definite commitments to begin by 1979. Also a number of facilities repre-
senting 4338 MW equivalent are identified as scrubbing and disposing un-
C O Q
treated FGC wastes in lined ponds in 1976. '
-151-
-------
Table 32. FGC CHEMICAL TREATMENT PROCESSES:
UTILITY PLANT CHARACTERISTICS
Utility
Commonwealth Edison
• Duquesnu Liyht Co.
Duquesne Light Co.
Southern California
Edison (SCE)
Central Area Power
Coordihation (CAPCO)
Group
Ohio Edison Co.
Duquesne Light Co.
Cleveland Electric
Co.
Toledo Edison Co.
Pennsylvania Power
Co. (operator)
Louisville Gas and
Electric Co.
ILG*E)
Columbus and Southern
Ohio Electric
In-Hanapoli* Power
and Light
Power Station
Will County.
Unit No. 1
Phillips
Elrama
Mohave, Unit No. 1
Mohave, Unit No. 2
Bruce Mansfield.
Unit No. 1
Unit No. 2
Cane Run, Unit No. 4
Cane Run, Unit No. 5
Cane Run, Unit No. 6
Mill Creek, Unit No. 3
Mill Creek. Unit No. 4
Conesville, Unit No. 5
Conesville, Unit No. 6
Petersburg, Unit No. 3
Station
Size,
MW
167
410
510
790
790
825
825
178
183
277
425
425
400
400
530
Coal C
%S
2 (1974)
1 (1975)
1 . 0 to 2 . 8
2 +
0. 5 to 0.8
0. 5 to 0.8
4 to 5
4 to 5
3.5 to 4.0
3. 5 to 4.0
3.5 to 4.0
3.5 to 4.0
3. 5 to 4.0
4. 5 to 4.9
4 . 5 to 4 . 9
3.0 to 3. 5
Character
% Ash
10
18
~18
10
10
8 to 10
8 to 10
17
17
sties
Btu/lb
9, 500
11,000
12,000
1 1 , 500
11, 500
FGD
Limestone
Slaked lime
Hydrated lime
with switch to
quicklime as
soon as
possible
Limestone
(lime
alternative)
Lime
alternative)
Lime
Lime
Lime
Lime
Lime
Lime
Lime
Thiosorbic
lime
Thiosorbic
lime
Limestone
FGD
Retrofit
Retrofit
Retrofit
Retrofit
Retrofit
New
New
Retrofit
Retrofit
Retrofit
New
New
New
New
New
FCD
Startup
Feb 1972
Jul 1973
.Nov 1975
Jan 1974
Nov 1973
Apr 1976
Apr 1977
Jun 1976
Dec 1977
Sep 1978
Jul 1977
Jul 1979
Jun 1976
Jan 1978.-
Apr 1977
Scrubber
Sixe,
MW
167
410
510
170
170
825
825
178
183
277
425
425
400
400
530
Particulate
Control Device
Upstream of
Scrubbers
(ESP) used only when FGD
not in use
Mechanical cyclones
followed by ESP,
Research-Cottrell :
Venturis
Mechanical cyclones
followed by ESP;
Venturis
ESP, Research-Cottrell
ESP, Research-Cottrell
None
None
ESP
ESP
absorber modules:
B «. W
One 2-stage variable
throat venturi module
processing 125 MW:
four single-stage
modules processing
remainder; Chemico
Five single-stage
Venturis; Chemico
Vertical TCA module:
Universal Oil Products
(UOP); test completed
Jul 1975
Horizontal 4-stage
module; SCE; tests
completed, Feb 1975;
170-MW prototype
unit to Public Service
Corners Station
2-stage scrubbers;
Chemico
2-stage scrubbers;
Chemico
American Air Filter
Combustion
Engineering
Not selected
American Air Filter
Not selected
UOP
UOP
4 modules; UOP
By-
pass
Yes
Yes
Yes
Yes
'29-31
29, 32
29, 33.
34
29. 35.
36
29, 35,
36
29, 37,
38
29, 37,
38
29
29
29
29
29
29
29 -
29
I
h-k
01
I
-------
Table 33. FGC WASTE DISPOSAL STATUS
Utility
Commonwealth Edison
Co.
Duquesne Light Co.
SCE
CAPCO Group
Ohio Ediaon Co.
Duqueane Light Co.
Cleveland Electric
Co.
Toledo Edison Co.
Pennsylvania Power
Co. (operator)
LGtE
Columbus and Southern
Ohio Electric Co.
Indiapolia Power and
Light
Power Station
Will County, Unit No. 1
(167 MW)
(387 (MW)
Elrama
(494 MW)
1st scrubber in
Service, Nov
1975
Mohave, Unit No. 1
Mohave, Unit No. 2
Bruce Mansfield,
Unit No. 1 (825 MW)
Unit No. 2 (825 MW)
Paddy's Run
(65 MW)
Cane Run. Unit No. 4
(178 MW)
Mill Creek, Unit No. 3
(425 MW)
Conesville, Unit No. 5
(400 MW)
Conesville, Unit No. 6
Petersburg, Unit No. 3
(530 MW)
Processor
Own with
Chicago
fly ash
®
IUCS
U.S. U.S.
IUCS.
18-mo
contract
starting
Sep 1975
IUCS
Dravo
Dravo
LG4E
LGiE
LCtE
IUCS
IUCS
Dravo
Fixation
Material
Lime and
fly ash
®
Calcilox
Fly ash
and
botton
ash
Lime and
fly aah
©
Calcilox
cat c u ox
Carbide
lime;
fly ash
mixed at
disposal
site
Lime
®
Calcilox
Waste
Solids
Content
35 to 45%
clarifier
30 to 40%
clarifier
underflow
30 to 40%
underflow
35 to 40%
clarifier
underflow.
filtered to
50 to 60% solids
ment
30% solids
clarifier
underflow
22 to 24% solids
in clarifier
underflow.
filtered to 35 to
45% solids
Thickener under-
flow at 30% solid.
Secondary thick-
ening then vacuum
filtered to 50 to
60% solids
Treatment
Conditions
10% lime and 20%
fly ash (of dry
ge so i
10% on dry
sludge basis
— 400 tons pro-
produced in 4
weeks, - 70%
solids, Jun 1975
Various
Treating waste
produced by 210
MW equivalent.
using equipment
from Mohave site
Treated all sludge
from 167 -MW
system for 1 yr
3 to 5% additive
(dry sludge basis)
added in thickener
Fixation plant to be
completed, May
1976. Blend with
dry fly ash
FGC Waste Disposal
Interim
Storage
7 .acre on-site
clay -lined
(prior to
Sep 1975
ponds, 6000 yd ,
each with 10 to
14-day capacity
None
Transport
Mode
Rotary mix
concrete
Truck, 25-
ton capacity
Treated
waste
pumped to
disposal site.
•— 7 mi; pond
supernate
returned for
reuse
Truck 1 mi
at $0, 50 /ton
Disposal site
1/3 mi from
plant; fixation
plant midway;
fixation plant
to disposal
site
Final Disposal Site
Offsite to permanent landfill
disposal site operated by
Sep 1975
capacity
Isolated area in landfill
operations
Landfill, ~ 2 mi from plant
Landfill of 25, 000 tons for
housing; parking lot con-
struction; streets and roads
in Bullhead City and Riviera;
synthetic aggregate manu-
facture
Unlined pond
400-ft high embankment
dams a 1330-acre valley
Site estimated to
be adequate for 20
to 25 yr
10-acre borrow; pit depth,
20 to 30 ft.
75-acre (minimum) tiered
landfill, 18 to 20 years
at site
Landfill
Ref.
29-31
2.32
22,25,
29. 33
33
22, 33,
39
25,29.
35,36
25
22,37,
38
40
22,29
22,29
25,29
41.42
29
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SECTION VIII
FOREIGN TECHNOLOGY
8. 1 . JAPAN43
Japanese flue gas desulfurization (FGD) nonregenerable
processing experience is the most advanced of foreign technology; significant
information is available in Reference 43.
The discarding of calcium sulfite sludge is not as widespread
in Japan as it is in the United States because of limitations on land available
for disposal. Recently in Japan, about six million tons yearly of SO- have
been emitted, mainly by the burning of heavy fuel oil. Since many desulfur-
ization plants will be built, it is likely that the supply of by-products will far
exceed the demand and that a substantial portion of them will be discarded.
Gypsum is generally considered the most reasonable by-product because
the demand for it is increasing and because it is considered as an easily
discarded material. The various by-products from nonregenerable waste
gas desulfurization processes are discussed in the following sections.
8.1.1 Calcium Sulfite
Limited quantities of calcium sulfite FGD wastes have been
produced in Japan because of its lack of utility and lack of available land for
discarding it. Mitsui Aluminum Company, which has produced a calcium
sulfite. sludge since 1972, plans to use the gypsum production process for
new installations because of the poor properties of the sludge. There is no
interest in chemical treatment, as there is in the United States.
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A synthetic paper from fairly pure calcium sulfite and
polyethylene, at a weight ratio of about 70:30 has recently been produced.
The product has some defects and is now undergoing improvement.
8. 1.2. Gypsum
Most of the large sulfur oxide recovery plants now under
construction or being planned are oriented toward the production of the by-
product gypsum. This approach is being taken for a number of reasons:
(1) Japan has large quantities of limestone; (2) the value of other by-products,
such as sodium salts, sulfuric acid,, and ammonium sulfate, is not expected
to increase since they are already in over supply; (3) production of elemental
sulfur from SO., in waste gases is complex; (4) Japan has little available land
on which to dispose of calcium sulfite sludge; (5) demand for gypsum has been
increasing considerably; and (6) gypsum is considered suitable for disposal
in case of over supply. To date, all of the by-product gypsum has been used
for wallboard production and as a cement setting retardant. Since 1971,
there has been a slight shortage of gypsum in Japan. However, since many
gyp sum-producing desulfurization plants are to be installed, an oversupply
is likely to occur in the future.
For wallboard production, gypsum of an appropriate crystal
size (longer than about 30 (im and thicker than 10 ^.m) and high purity is
desired. Gypsum obtained from oilrfired flue gas and from most other gases
usually meets these requirements.
The by-product gypsum is nearly white or light brown. Users
of gyp sunn for cement and wallboard have gradually become accustomed to
the colored product, resulting from the small amount of dust derived from
the oil-fired flue gas as it passes through electrostatic precipitators. The
material is reported to have no adverse effect on the gypsum properties.
The thickness of gypsum crystals is generally an important
factor in the strength of wallboard. Crystals obtained from wet-lime stone
processes are not very long but have considerable thickness and ara con-
sidered ideal for use in wallboard.
-156-
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For use as a retarder in the setting of cement, gypsum should
contain less than about 10 percent moisture because wet gypsum gends to
form a "bridge" in the hopper and cannot be charged smoothly to the cement
mill. Normally, by-product gypsum contains less than 10 percent moisture
after being centrifuged. Well-grown gypsum crystals produced by some of
the indirect limestone processes (100 to 500 |o.m) contain only 5 to 7 percent
moisture after being centrifuged. The presence of sodium in gypsum can
adversely affect the property of cement, but the amount of sodium in gypsum
produced by the sodium-limestone process is negligible because of the ease
of washing due to the large crystal size. Ten percent fly ash in gypsum is
reported to have no detrimental effects. Calcium sulfite can be used also
for a cement setting retardant replacing a portion of the gypsum. Magnesium
sulfate and calcium chloride in amounts less than 0. 5 percent may have no
adverse effects on wallboard and cement production.
Since a considerable oversupply of gypsum may occur in the
future, many groups are investigating new uses for it. The most promising
new use is as a building material. The usual type of calcium sulfate hemihy-
drate (|3 type) has lower strength than concrete (Figure 25). The herriihydrate
of o/ type has a much larger crystal size and higher strength than P type but
is fairly expensive. The II-anhydrite, which is obtained by heating gypsum
at 950 to 1000°C, hydrates fairly rapidly and increases in strength when a
small amount (1 to 2 percent) of potassium sulfate is added. Recent tests
have shown that an anhydrite of good quality can be obtained with by-product
gypsum from SO? recovery if the fly ash content is less than about 5 percent.
A larger amount of fly ash tends to decrease the strength.
Technology for reinforcement of gypsum with glass fiber has
43
been developed recently in England. The reinforced gypsum from a type
hemihydrate has compression, bending, and tensile strengths equal to and an
impact strength higher than asbestos-reinforced concrete.
A well known limitation in the use of gypsum as a building
material is its lack of resistance to water. To eliminate this deficiency, a
-157-
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W/G: WATER/GYPSUM
W/C: WATER/CEMENT
CM
400
300
o
CO
200
to
£100
Q_
o
o
- 6,000r
-ANHYDRIDE W/G = 0.35
a-HEMIHYDRATE W/G = 0.36
CONCRETE W/C = 0.6
B- HEM I HYDRATE W/G = 0.7
0-HEMIHYDRATE W/G = 0.6
1 2 3
AGING, weeks
Figure 25. Strength of various types of gypsum and concrete
-158-
-------
gypsum plastic composite has been recently developed in Japan. Usually, a
resin monomer such as methyl methacrylate or styrene is used for impreg-
nation. The monomer is polymerized by a thermal catalytic process. The
composite is reported to have high strength, to be resistant to water, acids,
and bases; and to have good workability. It is also semi-incombustible. It
may, therefore, have potential as a high-grade building material.
8.2 WEST GERMANY
The Holter process includes the oxidation of FGD waste to
44
form by-product gypsum. In describing the operation of over 7000 hours
of a 40-MW-equivalent prototype plant, the stack gas with SO_ content in the
range of 600 to 875 ppm SO~ was scrubbed with a special washing fluid. After
additional washing in a venturi,. drying, separation, treatment and oxidation,
a gypsum with less than 0. 5 percent CaSO_ was produced.
The washing solution is reported to be clear and alkaline and
does not involve a lime slurry. Rather, the Holter process is reported to
use a solution of lime innoculated with chlorides and Absorben '75.
-159-
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REFERENCES
1. L. W. Nannen and K. E. Yeager, "Status of the EPRI Flue Gas
Desulfurization Development Program, " Paper presented at the U.S.
Environmental Protection Agency Symposium on Flue Gas Desulfuriza-
tion, New Orleans, March 8-11, 1976.
2. J. W. Jones, "Research and Development for Control of Waste and
Water Pollution from Flue Gas Cleaning Systems, " Paper presented
at the U. S. Environmental Protection Agency Symposium on Flue Gas
Desulfurization, New Orleans, March 8-11, 1976.
3. U. S. Environmental Protection Agency Symposium on Flue Gas
Desulfurization, New Orleans, March 8-11, 1976.
4. J. Rossoff and R. C. Rossi, Disposal of By-Products from Non-
Regenerable Flue Gas Desulfurization Systems; Initial Report,
EPA-650/2-74-037-a, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina (May 1974).
5. J. Rossoff, et al. , Disposal of By-Products from Non-Regenerable
Flue Gas Desulfurization Systems; Interim Report, The Aerospace
Corporation, El Segundo, California (to be published).
6. L. J. Bornstein, et al. , Reuse of Power Plant Desulfurization Waste
Water, EPA-600/2-76-024, U.S. Environmental Protection Agency,
Corvallis, Oregon (February 1976).
7. P. B. Suresh, ed. , Trace Elements in Fuel, American Chemical
Society, Washington, D. C. (1975).
8. R. R. Ruch, H. J. Gluskoter, and N. F. Shimp, Occurrence and
Distribution of Potentially Volatile Trace Elements in Coal,
EPA-650/2-74-054, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina (July 1974).
-161-
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9. Coal Fired Power Plant Trace Element Study; A Three Station
Comparison, Report prepared for U.S. Environmental Protection
Agency, Region VIII, Denver, Colorado, by Radian, Inc., Austin,
Texas (September 1975).
10. D. J. vanLehnden, R. H. Jungers, and R. E. Lee, Jr., "Determination
of Trace Elements in Coal, Fly Ash, Fuel Oil and Gasoline: A Pre-
liminary Analysis of Selected Analytical Techniques, " J. Anal. Chem. ,
46 (2), 239 (February 1974).
11. E. M. Magee, H. J. Hall, and J. M. Varga, Jr. ,' Potential Pollutants
in Fossil Fuels, EPA-R-2-73-249, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina (June 1973).
.12. J. L. Mahloch, "Chemical Fixation of FGD Sludges: Physical and
Chemical Properties, " Paper presented at the U.S. Environmental
Protection Agency Symposium on Flue Gas Desulfurization, New
Orleans, March 8-11, 1976.
13. R. B. Fling, et al. , Disposal of Flue Gas Cleaning Wastes: EPA Shawnee
Field Evaluation: Initial Report, EPA-600/2-76-070, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina (March 1976),
14. J. Rossoff and R. C. Rossi, "Flue Gas Cleaning Waste Disposal: EPA
Shawnee Field Evaluation, " Paper presented at the U. S. Environmental
Protection Agency Symposium on Flue Gas Desulfurization, New
Orleans, March 8-11, 1976.
15. J. W. Jones, J. Rossoff, and R. C. Rossi, "Flue Gas Cleaning Waste
Characterization and Disposal Evaluation, " Paper presented at the Fourth
International Ash Utilization Symposium, St. Louis, Missouri, March 24-
25, 1976.
16. J. L. Mahloch, et al. , Pollutant Potential of Raw and Chemical Fixed
Hazardous Industrial Wastes and Flue Gas Desulfurization Sludges;
Interim Report, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, Mississippi (to be published).
17. P. A. Corrigan, Preliminary Feasibility Study of Calcium-Sulfur
Sludge Utilization in the Wallboard Industry, TVA-S-466, Tennessee
Valley Authority,. Muscle Shoals, Alabama (June 21, 1974).
18. J. I. Bucy, J. L. Nevins, and P. A. Corrigan, "Marketability of
Abatement Sulfuric Acid and Sulfur from FGD Applied to Power Plants
in the Eastern United States, " Paper presented at the U. S. Environ-
mental Protection Agency Symposium on Flue Gas Desulfurization,
New Orleans, March 8-11, 1976.
-162-
-------
19. R. H. Borgwardt, "IERL-RTP Scrubber Studies Related to Forced
Oxidation, " Paper presented at the U.S. Environmental Protection
Agency Symposium on Flue Gas Desulfurization, " New Orleans,
March 8-11, 1976.
20. J. G. Noblett, Jr. , Plant Selection for Water Recycle/Reuse Alternatives
Study, TN 200-118-03, Radian, Inc., Austin, Texas (December 11,
atuay,
1975).
21. Personal communication, Dr. R. Peck and L. Pircon, December 5,
1975 and March 24, 1976, respectively.
22. J. L. Crowe and H. W. Elder, "Status and Plans for Waste Disposal
from Utility Applications of Flue Gas Desulfurization Systems, " Paper
presented at the U.S. Environmental Protection Agency Symposium on
Flue Gas Desulfurization, New Orleans, March 8-11, 1976.
23. T. W. Klym and D. J. Dodd, "Landfill Disposal of Scrubber Sludge, "
Paper presented at the American Society of Civil Engineers
Meeting, Kansas City, October 1974.
24. Personal communication, D. Harrison, Ontario Hydro, March 25,
1976.
25. Personal communication, H. Mullen, IU Conversion Systems, to
J. Rossoff, The Aerospace Corporation, March 25, 1976.
26. R. B. Dakan, R. A. Edwards, and R. E. Rush, "Interim Report on
Chiyoda Thoroughbred 101 Coal Application Plant at Gulf Power
Scholz Plant, " Paper presented at the U. S. Environmental Protection
Agency Symposium on Flue Gas Desulfurization, New Orleans,
March 8-11, 1976.
27. R. L. Berger, Stabilization of Sulfate Sludge: Final Report on
Research Completed to September 1973, Report prepared for Chicago Fly
Ash Corporation and Commonwealth Edison Company (March 1974).
28. Flue Gas Desulfurization Systems; Summary Report, Report prepared
for U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina, by PEDCO-Environmental Specialists (January-
February 1976).
29. T. W. Devitt, G. A. Isaacs, and B. A. Laseke, "Status of FGD
Systems in the United States, "Paper presented at the U.S. Environ-
mental Protection Agency Symposium on Flue Gas Desulfurization,
New Orleans, March 8-11, 1976.
-163-
-------
30. Survey of Flue Gas Desulfurization Systems, Will County Station,
Commonwealth Edison Company, EPA-650/2-75-057-J, U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina
(October 1975).
31. W. G. Stober, "Operational Status and Performance of the Common-
wealth Edison Will County Limestone Scrubber, " Paper presented at
the U.S. Environmental Protection Agency Symposium on Flue Gas
Desulfurization, New Orleans, March 8-11, 1976.
32. Survey of Flue Gas Desulfurization Systems, Phillips Power Station,
'Duquesne Light Company, EPA-650/2-75-057-C, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina
(July 1975).
33. R. G. Knight and S. L. Pernick, "Duquesne Light Company Elrama
and Phillips Power Stations Lime Scrubbing Facilities, " Paper pre-
sented at the U. S. Environmental Protection Agency Symposium on
Flue Gas Desulfurization, New Orleans, March 8-11, 1976.
34. Personal communication, R. Patton, Duquesne Light Company, to
J. Rossoff, The Aerospace Corporation, May 24, 1976.
35. Survey of Flue Gas Desulfurization Systems, Mohave Station,
"Southern California Edison Company, EPA-650/2-75-057-k, U. S.
Environmental Protection Agency, Research Triangle Park, North
Carolina (October 1975).
36. A. Weir, et al. , "Results of the 170 MW Test Modules Program,
Mohave Generating Station, Southern California Edison Company, "
Paper presented at the U.S. Environmental Protection Agency .
Symposium on Flue Gas Desulfurization, New Orleans, March 8-11,
1976.
37. "Bruce Mansfield Fact Sheet, " Pennsylvania Power Company,
October 1975.
38. Personal communication, R. C. Forsythe, Pennsylvania Power
Company, to J. Rossoff, The Aerospace Corporation, April 27, 1976.
39. "IU Conversion Systems Completes Scrubber Sludge Conversion
System for Duquesne Light Company's Elrama Power Station, " Press
release, IU Conversion Systems, Philadelphia, Pennsylvania,
February 1976.
-164-
-------
40. Survey of Flue Gas Desulfurization Systems, Paddy's Run Station,
Louisville Gas and Electric Company, EPA-650/2-75-057-d, U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina (August 1975).
41. Personal communication, R. J. Bacskai, IU Conversion Systems, to
J. Rossoff, The Aerospace Corporation, May 24, 1976.
42. "IU Conversion Systems Signs 20-Year Agreement for Scrubber
Sludge Conversion at Columbus and Southern Ohio Electric Plant, "
Press release, IU Conversion Systems, Philadelphia, Pennsylvania,
July 11, 1975.
43. J. Ando and G. A. Isaacs, SC*2 Abatement for Stationary Sources in
Japan, EPA-600/2-76-013-a, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina (January 1976).
44. "Stack Gas Desulfurization Plant Using the Holter Process, " Brochure
presented at the U.S. Environmental Protection Agency Symposium on
Flue Gas Desulfurization, New Orleans, March 8-11, 1976.
45. Air/Water Pollution Report, Vol. 14, No. 4, Business Publishers,
Inc., Silver Spring, Maryland (January 26, 1976), p. 39.
-165-
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-76-018
2.
3. RECIPIENT'S ACCESSION NO.
4.
AND SUBTITLE CONTROL OF WASTE AND WATER
POLLUTION FROM POWER PLANT FLUE GAS
CLEANING SYSTEMS: First Annual R and D Report
5. REPORT DATE
October 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
P. P. Leo and J. Rossoff
8. PERFORMING ORGANIZATION REPORT NO.
ATR-76(7297-01)-2
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The Aerospace Corporation
P.O. Box 92957
Los Angeles, California 90009
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
68-02-1010
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
Annual; 1-12/75
14. SPONSORING AGENCY CODE
EPA-ORD
is.SUPPLEMENTARY NOTES JERL-RTP project officer for this report is J.W. Jones, Mail
Drop 61, 919/549-8411 Ext 2915.
16. ABSTRACT
The report summarizes and assesses the state of research and development
in the fields of non-regenerable flue gas cleaning (FGC) waste treatment, utilization,
and disposal, as well as water reuse technology, for coal-fired utility power plants.
Significant results cover: (1) chemical and physical characterization of wastes from
eastern and western U.S. plants using lime, limestone, or double-alkali scrubbing
systems; (2) chemical and physical properties and leaching characteristics of treated
and untreated wastes; (3) field evaluations of treated and untreated waste disposal; (4)
disposal alternatives; (5) cost estimates for ponding and for fixation disposal methods;
(6) disposal standards; (7) gypsum production and marketing; (8) potential use of
wastes in fertilizer production and portland cement manufacture: (9) beneficiation
studies; and (10) total power plant water reuse. Reports are to be issued annually to
evaluate the progress of FGC waste disposal and utilization technology. Results, not
available but to be included in subsequent reports, will cover: coal-pile drainage,
ash characterization and disposal, soil attenuation effects, and conceptualized design
cost analyses for various methods of FGC waste disposal.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Waste Treatment
Electric Power Plants Waste Disposal
Flue Gases
Coal
ombustion
Water Pollution
Water Reclamation
Scrubbers
Calcium Oxides
Limestone
Ponds
Gvosum
Pollution Control
Stationary Sources
Flue Gas Cleaning
Double-Alkali Process
13B
10B
21B
21D
07A
07B
08G
08H
3. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
179
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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