&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research EPA-600/7-79-158c
Laboratory July 1979
Research Triangle Park NC 27711
Chemically Active Fluid
Bed for SOX Control:
Volume 3.
Sorbent Disposal
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-158c
July 1979
Chemically Active Fluid Bed for SOX Control
Volume 3. Sorbent Disposal
by
C. C. Sun
Westinghouse Research and Development Center
1310 Beulah Road
Pittsburgh, Pennsylvania 15235
Contract No. 68-02-2142
Program Element No. EHB536
EPA Project Officer: Samuel L Rakes
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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PREFACE
The Westinghouse Research and Development Center is carrying
out a program under contract to the United States Environmental Protec-
tion Agency (EPA) to provide experimental and engineering support for
the development of the Chemically Active Fluid-Bed (CAFB) process. The
process was originally conceived at the Esso Petroleum Company, Ltd.,
Abingdon, UK (ERCA), as a fluidized-bed gasification process to convert
heavy fuel oils to a clean, medium heating-value fuel gas for firing in
a conventional boiler. Westinghouse, under contract to EPA, completed
an initial evaluation of the process in 1971. Conceptual designs and
cost estimates were prepared for new and retrofit utility boiler appli-
cations using heavy fuel oil. Westinghouse continued the process
evaluation from 1971 to 1973 and formulated an atmospheric pollution
control demonstration plant program for retrofit of a utility boiler
utilizing a high-sulfur, high-metals content fuel oil (for example,
2
vacuum bottoms). The CAFB process represented an attractive option for
use of these low-grade fuels, for which pollution control using hydro-
desulfurization or stack-gas cleaning was not economical. Application
of a pressurized CAFB concept with combined-cycle power plants was also
assessed.^ Experimental support work was initiated between 1971 and 1973
to investigate two areas of concern - sorbent selection and spent sorbent
processing - to achieve an acceptable material for disposal or utiliza-
tion. The preliminary design and cost estimate for a 50 MWe demonstration
plant at the New England Electric System (NEES) Manchester Street Station
3
in Providence, RI were completed in 1975. Commercial plant costs were
projected and development requirements identified. Experimental support
of the sulfur removal system continued in order to provide a basis for
iii
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the detailed plant design. A number of design and operating parameters
from the preliminary design study that required further development were
identified. The environmental impact of the disposal of unprocessed and
processed spent sulfur sorbent has continued to be an area requiring
further study. This report presents the results of a test program
carried out from 1976 to 1979 to obtain data for assessing the potential
environmental impact of disposal.
Additional support work carried out under the present contract
(68-02-2142) includes:
„ , . 4,5
• Sorbent selection
• Processing spent sorbent to minimize environmental
impact
• Solids transport between adjacent CAFB fluidized beds
e Engineering evaluation of the CAFB process
iv
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ABSTRACT
The chemically active fluidized-bed (CAFE) process is being
developed to convert high-sulfur heavy oils and low—grade coal to clean,
medium heating—value fuel gas in conventional boilers. The disposal of
the spent sorbent, which consists of varying amounts of CaO, CaS, and CaSO,,
may cause environmental concerns associated with potential air, water, odor,
and heat pollution. The spent sorbent can be further processed to reduce
its environmental impact by methods including dry sulfation, dead-burning,
room-temperature fly ash blending, high-temperature processing, and slurry
carbonation. A laboratory experimental program has been carried out to
investigate three major areas: residue characterization, leaching property,
and thermal activity. The results from tests on solid residues from the
Esso Research Centre, Abingdom UK (ERCA) pilot plant indicate that the
CAFB spent sorbent residue may be hazardous because of its sulfide content.
Test results indicate that nonhazardous disposal of the residue can be
achieved by processing the spent sorbent. The environmental impact of CAFB
residue disposal is also compared with results of conventional power plant
residues: flue gas desulfurization residues (FGD) and lignite ash. Federal
regulations and guidelines on solid waste disposal, including the recently
enacted Resource Conservation and Recovery Act, have been reviewed to assess
their impact on CAFB solid residue disposal.
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TABLE OF CONTENTS
SUMMARY 1
1. INTRODUCTION 4
2. REGULATIONS/CRITERIA 6
3. EXPERIMENTAL TESTING PROGRAM 13
Samples 13
Unprocessed CAFB Residue 13
Processed CAFB Residue 13
Reference Material 15
Experimental Program and Testing Method 16
Characterization 16
Leaching Tests 16
Activity Tests 18
Results 19
Unprocessed Residue 19
Processed Residue 50
Reference Material 68
Heat Release Property 85
Total Dissolved Solids 87
Total Organic Carbon 92
Leaching Media 93
Summary 95
4. ENVIRONMENTAL ASSESSMENT 98
5. REFERENCES 102
vii
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LIST OF FIGURES
Page
1. Photomicrographs of (a) CAFB-8 Gasifier Material
(b) Regenerator Material 25
2. SEM Photomicrographs of CAFB-8 Stack Fines Showing
Variation of Their Physical Characteristics 27
3. SEM and EDAX of CAFB-8 Stack Fines 28
4. SEM and EDAX of CAFB-10A Gasifier Bed Material 33
5a. Photomicrograph of a Cross-Section of a Spent CAFB-10A
Gasifier Sorbent Particle Blocking the Area for Electron
Microprobe Analysis 34
b-f. EMA Area Scan for Ca, S, Fe, Si, and Al 34
6a. Photomicrographs of a Cross-Section of a Spent CAFB-10A
Gasifier Sorbent Particle Blocking the Area for EMA Scan 35
b-f.EMA Area Scan for Ca, S, Fe, Si, and Al 35
7. Leachate Characteristics as a Function of Total Continuous
Leach Time for the CAFB Samples Obtained via the Ralph
Stone Co. 38
8. Leachate Characteristics as a Function of Intermittent
Leaching Time for the CAFB Samples. 39
9. (a) SEM Photomicrograph and (b) EDAX Spectrum of the White
Precipitate Formed Readily in Air from the Leachate 40
10. Electron Microprobe Analysis of Spent Regenerator Bed
Material from CAFB "Lignite" Run 42
11. SEM and EDAX of Stack Cyclone Fines from CAFB "Lignite"
Run Material 46
12. SEM and EDAX of Stack Cyclone Fines from CAFB "Lignite"
Run 47
viii
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LIST OF FIGURES (Cont)
Paee
13. Leachate Characteristics as Functions of Batch
Mixing Time 52
14. Leachate Characteristics as a Function of Stone
Loading 53
15. Comparison of Dissolved Sulfide in Leachates of Sulfated
and Unsulfated CAFB-9 Spent Sorbent 55
16. Comparison of Specific Conductance of Leachates of Sulfated
and Unsulfated CAFB-9 Spent Sorbent 55
17. Thermogravimetric Curve of Processed Spent Stones 59
18. Typical SEM and EDAX of TUGCO Ash 69
19. Leachate Characteristics of TUGCO Ash 72
20. Valley Builder Supply Block 75
21. SEM of Unprocessed FGD Sludge 80
22. Leachate Characteristics of Dried FGD Sludge as a
Function of Continuous Leach Time 82
23. Leachate Characteristics of Dried FGD Sludge as a Function
of Intermittent Leaching 83
24. Heat Release Property as a Function of Solid:Water Ratio 87
25. Heat Release Property of Spent Solids from the CAFB Process 90
26. Correlation between TDS and Specific Conductance in CAFB
Leachate System 92
27. Leachate Characteristics as a Function of Mixing Time 96
IX
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LIST OF TABLES
Page
1. Comparison of Environmental Impact of Processed and
Unprocessed CAFB Spent Sorbents 3
2. Hazardous Waste Criteria (RCRA Section 3001) 8
3. Selected Water Quality Criteria 11
4. CAFB Spent Sorbents Tested 14
5. Spent Sorbent Characterization by X-Ray Diffraction 20
6. Chemical Analysis of CAFB Spent Sorbents from the
Regenerator 21
7. Leaching Results of Spent CAFB Regenerator Sorbents 22
8. Trace Metal Elements in the Unprocessed CAFB Regenerator
Spent Sorbents and Their Leachates 23
9. Leaching Results from the CAFB-8 Gasifier Spent Sorbent 26
10. Chemical Characteristics of CAFB-8 Stack Fines and
Leachates 30
11. Comparison of Trace Metal Elements in Regenerator Bed
Material and Stack Fines of CAFB-8 31
12. Chemical Characteristics of CAFB 10-A Gasifier Material and
Its Leachates 36
13. Trace Metal Content in the CAFB Spent Sorbents Obtained
through Ralph Stone Co., and their Leachates 43
14. CAFB-11 Operating Conditions 44
15. Solid and Leachate Characteristics of Spent Material from
CAFB "Lignite" Run 48
16. Chemical Characteristics of CAFB "Lignite" Run Residues and
Leachates 49
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LIST OF TABLES (Continued)
Page
17. Residual Activity of Spent CAFB "Lignite" Run Material by
Heat-Release 51
18. Sulfur Contents in CAFB-9 Spent Sorbent and Dry-Sulfated
CAFB-9 Spent Sorbent 51
19. Comparison of Chemical Compositions of CAFB-9 Spent Sorbent
before and after Dead-Burning 57
20. Leachate Characteristics of Dead-Burned CAFB-9 Stones 58
21. Environmental Impact of Sintered (Dead-Burned) Spent Sorbent 61
22. Leachate Characteristics of Room-Temperature Processed Solid
Compacts of CAFB-9 Regenerator Stone and Fly Ash 62
23. Preparation and Compositions of High-Temperature Processed
Solid Compacts 65
24. Leachate Characteristics of High-Temperature Solid Compacts
of Sorbent/Ash Mixture 66
25. Analysis of TUGCO Ash 68
26. Chemical Characteristics of Leachate from TUGCO Ash by
Continuous Shake Test 71
27. Trace Metal Elements in TUGCO Ash and Its Leachate 73
28. Chemical Compositions of Valley Builders Supply Samples 74
29. Chemical Characteristics of Valley Builder Supply Block and
Leachate 76
30. Heat-Release Properties of Valley Builder Supply Samples 77
31. Summary of FGD Sludge Samples 79
32. Chemical Characteristics of FGD Sludge, Liquor, and Leachate 84
33. Activity Tests of Processed and Unprocessed CAFB Spent
Sorbents by Their Heat-Release Properties 88
34. Chemical Characteristics of CAFB-10A Leachate Using
Different Eluent 94
35. Comparison of Leachate Characteristics from the CAFB and
FGD Residues 97
xi
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LIST OF TABLES (Continued)
Page
36. Comparison of Environmental Impact of Processed and 99
Unprocessed CAFB Spent Sorbents
37. Preliminary Comparison of the Environmental Impact of the 101
Disposal of CAFB and FGD Residues
xii
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NOMENCLATURE
ATV = reactivity coefficient
BOD = biochemical oxygen demand
CAFB = chemically active fluidized bed
COD = chemical oxygen demand
CSO = Columbus Southern Ohio Company
DLC = Duquesne Light Company
DWS = drinking water standards
EDAX = energy dispersive analysis by X-ray
EMA = electron microprobe analysis
ERCA = Esso Research Centre, Abingdon, UK
FBC = fluidized-bed combustion
FGD = flue gas desulfurization
LGE = Louisville Gas and Electric Company
MATE = Minimum Acute Toxicity Effluent
MEG = Multimedia Environmental Goals
NIPDWR = National Interim Primary Drinking Water Regulations
RCRA = Resource Conservation and Recovery Act
SAM = Source Analysis Model
SEM = scanning electron microscopy
TDS - total dissolved solids
TEP = toxicant extraction procedure
xiii
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NOMENCLATURE (Cont)
TGA = thermogravimetric analysis
TOC = total organic carbon
TUGCO = Texas Utility Generating Corporation
USPHS = United States Public Health Service
WHO = World Health Organization
xiv
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ACKNOWLEDGEMENT
This work was performed under Contract 68-02-2142 for IERL of
EPA. We should like to acknowledge the contributions of Mr. Sam Rakes
as the contract officer.
I should like to thank Messrs. G. L. Johnes of ERCA: R. Stone
of Ralph Stone Co., and A. S. Werner of GCA for their cooperation in
supplying CAFB residues. I should also like to acknowledge the kind
assistance of Mr. P. P. Leo of Aerospace Corporation, Mr. R. P. Van'Ness
of Louisville Gas and Electric Co., and Mr. D. Henzel of Dravo Lime Co.
in supplying FGD scrubber sludge samples for this study.
I should also like to acknowledge the cooperative efforts and
contributions by many Westinghouse personnel, in particular, Dr. D. L.
Keairns, the project manager, for his guidance and consultation throughout
this investigation, Mr. C. H. Peterson for his work in residue processing
and in providing the processed samples for this study, and Messrs. J. T.
McAdams and R. Brinza for their technical assistance in carrying out the
laboratory experiments. I should also like to express my appreciation
to many members of the Analytical Chemistry and Physical Metallurgy Depart-
ments within the Westinghouse R&D Center for their valuable contributions
in sample characterization.
xv
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SUMMARY
Westinghouse has developed an experimental testing program to
determine the environmental impact of the disposal of CAFB residue, con-
centrating its efforts on three major areas — residue characterization,
leaching property investigation, and potential thermal pollution.
We have reviewed the environmental laws, including up-to-date
development of the regulations and guidelines under the authority of the
Q
Resource Conservation and Recovery Act.
Actual CAFB residues from ERCA's gasifier, regenerator, cyclone,
and stack were used in this study. Materials processed by dry sulfation,
dead-burning, room-temperature ash blending, high-temperature compacting,
and slurry carbonation were also tested to evaluate the effect of further
processing.
On the basis of laboratory testing results, we judged that
unprocessed CAFB spent sorbent would be environmentally unacceptable for
direct land disposal. Environmental acceptability, however, can be
achieved by further processing based on the available test data. Table 1
summarizes the degree to which negative environmental impact can be re-
duced by use of four of the processing alternatives for spent sorbent from
the CAFB gasification process. We believe the leaching tests performed
result in severer projections of environmental impact than will be encountered
in practice. Since there are no guidelines for leachate qualities at the
present time, we have compared results with drinking water standards and
the leachate characteristics of natural gypsum.
The drinking water standards in this investigation, however,
are used only in an effort to put data into perspective until EPA guide-
lines are established and should not be construed as suggesting that the
leachate must necessarily meet drinking water standards. These standards
-------
of course, are extremely conservative; a leachate dilution/attenuation
factor of 10 is currently being considered in the proposed regulations
0
under Section 3001 of the Resource Conservation and Recovery Act of 1976
(RCRA) by the Hazardous Waste Management Division of the Office of Solid
Waste, EPA.
The major environmental concerns with direct disposal are heat
release, sulfide, pH, calcium, SO., and IDS. The major environmental
concerns with disposal after processing are pH, calcium, SO , and IDS.
On the basis of these results, spent sorbent processing will be required
for nonhazardous disposal. Four processing options were investigated. A
comparison of the environmental impact is summarized in Table 1. On the
basis of environmental impact, the high-temperature processing or dry
sulfation options are the recommended processes, followed by dead-burning
and low-temperature fly ash blending. There are advantages and disadvantages
to each method of processing, and the decision for each application will
be based on the balance of technical, environmental, and economic factors.
For example, the high-temperature processing option requires a high energy
consumption and may only be selected if it can result in utilization of
the product material. Of course, site selection, design and management
of the disposal task based on the site-specific hydrology, geology, climate,
and soil composition are critically important to the success of solid waste
disposal practice. Selection of the proper processing method to reduce
surface area and permeability and to improve the heat—release and leaching
properties can greatly simplify the disposal management task.
Pending implementation of EPA criteria with which to assess the
environmental acceptability of the disposal of CAFE residues, the chemical,
physical, and leaching properties of the spent CAFB material are compared
with the residues from conventional coal-burning power plants with flue
gas desulfurization processes (FGD).
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Table 1
COMPARISON OF ENVIRONMENTAL IMPACT OF PROCESSED AND UNPROCESSED
CAFB SPENT SORBENTS
Environmental
arameters
Processing
PH
Total
Dissolved
Solids
(a)
Sulfide
Sulfate
Calcium
Trace
Metal
(a)
Heat
Release
I3gm/Z0ml)
Total
Organic
Carton
(a)
Unprocessed CAFB
Dry-Sulfation
AT=ND<0.2°C
Dead-Burning
AT=ND<0.2°C
Rm-temp.Protessing
AT=ND<0.2°C
HI 3emp. Processing
AT=NO<0.2°C
Note: u Unprocessed CAFB Leachate Characteristics
4- Improved From u Value
0 No Significant Change From u Value
83 Do Not Meet Either The Drinking Water or Gypsum Leachate Criteria
£2 Pass Gypsum Leachate Criteria But Not Drinking Water Standards
O Pass Both Drinking Water and Gypsum Leachate Criteria
(a) No Drinking Water Standards Exist
A preliminary comparison of the environmental impact of the disposal of
unprocessed CAFB solid wastes and FGD sludge residues from varying pro-
cessing systems suggests that the disposal of the CAFB solid waste may
cause comparable (due to chemical properties), perhaps less negative (due
to physical properties), environmental effects than the disposal of the
residue from currently commercialized FGD processes.
This assessment is based on results from a continuing program
that is, however, limited by the investigation of spent CAFB materials
from a pilot-scale operation. These conclusions are considered preliminary
and should be reassessed as more representative samples become available
from a larger scale plant.
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1. INTRODUCTION
The CAFB (Chemically Active Fluidized Bed) gasification process,
in which limestone or dolomite removes the sulfur from fuel gas during the
gasification process, was developed to permit the utilization of high-
sulfur residual fuel oil or refinery bottoms in conventional boilers by
producing a low-sulfur fuel gas. Coal is also being investigated as a
fuel. The process can be operated as a once—through limestone sorbent
system, a sorbent regeneration/sulfur recovery system, or a sorbent
regeneration system without sulfur recovery by capturing the sulfur-rich
gas from the regenerator with the spent stone. The spent stone from each
system alternative can be processed to minimize the environmental impact
of the waste stone for disposal or to provide material for potential
3 9
market utilization. '
Under contract to the U. S. Environmental Protection Agency
(EPA), Westinghouse has carried out laboratory support work on sulfur
removal, solid transport, and the environmental impact of residue
3 9
disposal. ' Esso Research Centre, Abingdon, England (ERCA) is carrying
out pilot-scale tests to investigate sulfur removal. At San Benito,
Texas, a 10 MW demonstration plant has been retrofitted by Foster Wheeler
Energy Corporation and Central Power and Light Co., and larger-scale
testing has begun.
The CAFB gasification/desulfurization process produces a dry,
partially utilized limestone (or dolomite) with particles up to 6000 pm
in size. The composition of the sorbent for disposition will depend on
the characteristics of the original stone, the fuel feed, the selection
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of the sorbent processing system, and the process operating conditions.
Spent sorbent compositions for the once-through and regenerative oper-
ating modes are:
Solids Composition, wt %
Regenerative Once-through
(regenerator solids) (gasifler solids)
CaO 85-95 50-75
CaS 2-5 25-50
CaSO, 2-4 vl
Inerts 1-10 1-10
The disposal of this solid may be accomplished by a variety of
methods. Several processing alternatives have been developed to convert
calcium oxide (CaO) and calcium sulfide (CaS) to an environmentally
acceptable form for disposal or further utilization. Dry sulfation and
dead-burning are examples of dry processing systems; slurry carbonation
3 9
is an example of the wet methods investigated. '
Among the factors that will affect the disposition of the
spent sorbent are the quantity of spent sorbent, its chemical charac-
teristics, regulations, geographical location, and the size of the
market for the respective applications. The environmental impact of any
disposed material is a function of its physical and chemical properties
and the quantity involved. Potential water pollution problems in many
cases can be predicted by chemical properties such as solubility, the
presence of toxic metals, and the pH of leachates. The disposal of spent
stone from the CAFB gasification process may create air pollution or
odor nuisance (e.g., hydrogen sulfide [H2S], depending on the amount of
CaS present. Heat may be released on hydration of CaO. Potential
water pollution may be introduced from the runoff leachates caused by
the rainfall and naturally occurring subsurface flow through the land-
fill site. An experimental testing program on stone analysis, leaching
properties, heat release properties, landfill properties, and air emis-
sion has been carried out to obtain this information. The assessment
reported here is limited to the environmental impact from land disposal
of unprocessed and processed spent sorbent. The processing work is
discussed elsewhere.
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2. REGULATIONS/CRITERIA
Under the authority of the Clean Air Act of 1970, the EPA
promulgated regulations on standards of performance for new stationary
13
sources of air pollution. Specifically, subpart B established standards
of performance for fossil-fuel-fired steam generators of more than
263.75 GJ/hr (250 million Btu/hr) and established the standards for
sulfur dioxide (S0?) emission. The alternatives available for com-
pliance with S0~ standards are:
1. To burn low-sulfur fuels
2. To remove the SCL from the exhaust gas with FGD systems
3. To use alternative technologies.
As an example of the third alternative, the chemically active
fluidized-bed gasification process employs calcium-based sorbent for
sulfur removal that results in the production of dry, partially utilized
sorbent and ash as solid residue for disposal. The environmental
standards for solid residue disposal from CAFB systems have not been
established. Two environmental laws that affect solid waste disposal
are the Resource Conservation and Recovery Act (RCRA) of 1976 (the
Solid Waste Disposal Act of 1965, as amended by P.L. 94-580, 1976),
and the Federal Water Pollution Control Act of 1972 (Public Law 92-500,
1972, as amended by Clean Water Act, P.L. 95-217, 1977).14'15 Eventually,
disposal guidelines are to be promulgated by EPA under the authority
of the former.
As a result of the Clean Air Act, the Water Pollution Control
Act, and other federal and state laws respecting public health and the
environment, greater amounts of solid waste have been created. Similarly,
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inadequate and environmentally unsound practices for the disposal or
use of solid waste may create greater amounts of air and water pollution
and other problems for the environment and for health. Among the
objectives of RCRA are the protection of health and the environment and
the conservation of valuable material and energy resources by:
• Providing technical and financial assistance to state and
local governments and interstate agencies for the develop-
ment of solid waste management plans
• Providing training grants in occupations involving the
design, operation, and maintenance of solid waste disposal
systems
• Prohibiting future open dumping on the land and requiring
the conversion of existing open dumps to facilities that
do not pose a danger to the environment or to health
• Regulating the treatment, storage, transportation, and
disposal of hazardous wastes that have adverse effects
on health and on the environment
• Providing for the promulgation of guidelines for solid
waste collection, transport, separation, recovery, and
disposal practices and systems
• Promoting a national research and development program for
improved solid waste management and resource conservation
techniques.
The passage of RCRA closed the legislative loop of environmental
laws (air/water/solid) and created a new level of control over solid waste
disposal. Of special concern are the regulations to be promulgated under
Subtitle C - Hazardous Waste Management.16-18 Table 2 summarizes the
currently proposed criteria for hazardous waste identification and those
that are being considered for future ruling. Of the characteristics
currently proposed for hazardous waste (ignitability, corrosivity,
reactivity and toxicity), toxicity and reactivity cause the most concern.
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Table 2
HAZARDOUS WASTE CRITERIA (RCRA SECTION 3001)
Characteristics
Status
Comment
1. Ignitability
2. Corrosivity
3. Reactivity
Toxicity
5. Radioactivity
6. Generic
Activity
7. Bioaccumulation
8. Additional
Aspects of
Toxicity
Proposed Dec. 18, 1978
in Fed. Reg.; scheduled
to be promulgated
Dec. 31, 1979.
Not intended to be
static; to be reviewed
periodically.
Advanced Notice for
Proposed Rulemaking,
Dec. 18, 1978.
Comments/information
invited.
To be proposed in Fed.
Reg. no sooner than
1 yr. from the Ad-
vance Notice date,
i.e., Dec. 18, 1979.
Current proposed regu-
lations apply only to
liquid waste pH >12 or
_<3, but proposed regu-
lations may change.
"Sulfide bearing waste
which can generate toxic
gases"...or, "reacts
violently with water"...
Some uncertainty may
arise from the interpre-
tation of this qualita-
tive statement, espe-
cially with regard to
regenerative, PFBC
residue.
A waste is hazardous if
its "EP" leachate
exceeds 10X primary DWS.
A waste is considered toxic and, therefore, hazardous if its
eluent from the "extraction procedure" (EP, proposed in Federal Register,
Dec. 18, 1978) contains trace elements exceeding ten times the primary
drinking water standards. Because of the low levels of trace elements
-------
exhibited by the CAFB leachates, we expect that the CAFB solids would
not be toxic. The unprocessed CAFB residue, however, may be considered
"reactive" because of its sulfide content. This is by no means conclusive.
Should the CAFB solids be determined to be hazardous waste under RCRA
3001, we would expect them to be classified under the "special waste"
category under the regulations of RCRA Sec. 3004 for "utility waste."
On the other hand, they could be processed (and we have shown that this
can be done) to render them nonhazardous and, therefore, subject to the
regulations and criteria under RCRA Sec. 4004 for nonhazardous waste
disposal^^ and proposed guidelines under RCRA Sec. 1008 for location,
design, construction, operation, and maintenance of solid waste land
disposal facilities.20
The primary environmental concern with solid waste disposal is
the potential ground and surface water contamination caused by leachate
run-off or seepage. The federal regulation that most nearly relates to
a limit on seepage water quality is the EPA's "Alternative Waste
Management Techniques for Best Practical Waste Treatment"2-'- under the
authority of the Federal Water Pollution Control Act of 1972 amended by
the Clean Water Act of 1977. These criteria, which apply to publicly
owned treatment and land application of waste water, state that the
groundwater, resulting from land applications of waste water, shall be
limited to the maximum contaminant levels contained in the National
22
Interim Primary Drinking Water Regulations (NIPDWR) or to the existing
concentration if the latter is greater. If the groundwater is to be
used for other than a drinking water supply, "the ground water (sic)
criteria should be established by the Regional Administrator." In
contrast to the United States Public Health Service (USPHS) Drinking
21
Water Standards (DWS), 1962, which limit sulfate and chloride to
250 mg/£ each (and many others, e.g., copper, iron, manganese, nickel,
tin, and zinc), no limits are given in the NIPDWR for these substances.
These and other substances, however, may be included in secondary
standards, when issued.
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In anticipation of such forthcoming criteria, the chemical
characteristics of leachates from leaching experiments are compared with
the drinking water standards set by NIPDWR,22 USPHS Drinking Water
Standards,23 and the World Health Organization (WHO) Potable Water
Standards. Of course, these standards are extremely conservative;
a leachate dilution/attenuation factor of 10 is currently being con-
sidered in the regulation draft under Section 3001 of RCRA by the
Hazardous Waste Management Division of the Office of Solid Waste, EPA.17
Note that the drinking water standards are used in this investigation
only in an effort to put data into perspective in the absence of EPA
guidelines and should not be construed as suggesting that the leachate
must necessarily meet drinking water standards. Although the guidelines
for the power plant effluents2-* are not applicable to the disposal of
dry spent sorbent from the CAFB process, they are used as additional
references in this investigation. Table 3 lists the selected water
quality criteria for leachate comparison.
Currently, EPA-IERL-RTP is developing Multimedia Environmental
26 27
Goals (MEG) and Minimum Acute Toxicity Effluent (MATE) for use in
the environmental assessment of rapid effluent screening. MATE values
are being developed on the basis of health and ecology for land, water,
and air. EPA-IERL-RTP/EACD (Energy Assessment Control Division) is also
developing Source Analysis Models (SAM) based on comparison with MEG
and MATE values. SAM/IA ranks effluent by "degree of hazard" and "toxic
no
unit discharge rate," and provides a standardized methodology for
environmental assessment.
Existing air pollution control regulations limit the S0?
emission level discharged by fossil fuel power plants. One commercialized
process for SO removal is flue gas desulfurization (FGD) , which gent-r-
ates large quantities of sludge and has received considerable attention
environmentally. A recently published EPA report by SCS Engineers
entitled "Data Base for Standards and Regulations Development for Land
29
Disposal of Flue Gas Cleaning Sludges concluded that the characteris-
tics of FGD sludge set the need for regulation and recommended that
10
-------
Table 3
SELECTED WATER QUALITY CRITERIA
Effluent Guidelines
Substance
Ag
As
Ba
Ca
Cd
Cr
Cu
Fe
Hg
Mg
Mn
Ni
Pb
Se
Sn
Zn
so4
Cl
N03
F
pH
(pH unit)
IDS
Drinking Water Standards, mg/£
22
NIPDWR
0.05
0.05
1.0
0.01
0.05
0.002
23
USPHS
0.05
0.05
1.0
0.01
0.05
(Cr+6)
1.0
0.3
0.05
2.0
\
l
0.05 0.05
0.01 0.01
1.0
1
1 5.0
I
250
250
10 (as N)j 45
1.4 to 1.7
2.4
500
WHO 24
Highest
Desirable
Level
0.05
75
0.01
0.05
0.1
0.001
30
0.05
0.1
0.01
5.0
200
200
45
1.7
7.0 - 8.5
500
Maximum
Permissible
Level
0.05
200
0.01
1.5
1.0
0.001
150
0.5
0.1
0.01
15
400
600
45
1.7
6.5 - 9.2
1500
and Standards
for Steam
Electric Power
Generation, 25
0.2
1.0
1.0
1.0
6.0 - 9.0
11
-------
regulations allow for site-specific factors as well as sludge character-
istics. Important disposal site characteristics to be considered for
regulatory action are present and projected land use, topology, hydrology,
and meteorology.
Because of the wide variation in the characteristics of solid
wastes in general, weather, soils, topography, groundwater from site to
site, and nearby stream guality and flow characteristics, permits are
currently being awarded on a site-specific basis. Eventually, state
g
regulations will apply as a result of the RCRA, but these regulations
will not be enacted until federal standards are promulgated. Depending
on the actual site selected for disposal, the leachates would have to
meet the water quality criteria for the specific water use.-'1-' Further-
more, the success of a land disposal application depends, above all,
on the design, construction, and operation of a specific disposal site
based on the geology, hydrology, and meteorology of that particular site.
12
-------
3. EXPERIMENTAL TESTING PROGRAM
SAMPLES
Samples investigated to leach the environmental impact of
land disposal fall into three categories.
Unprocessed CAFB Residue
Residues from the CAFB pilot plant at ERCA were used. These
included spent gasifier, regenerator, cyclone, and stack fines.
Table A summarizes the unporcessed ERCA residues tested and the fuel and
sorbent used for each run.
Processed CAFB Residue3'9>12
Various techniques for further processing were used on the
spent sorbent. Samples tested for their environmental impact included
those processed by the most promising methods: dry sulfation, dead-
burning, room-temperature fly ash blending, and high-temperature com-
pacting. They are listed below:
• DS-mix - CAFB-7 spent sorbent processed by dry sulfation in
a 2.5-cm bench-scale fixed-bed reactor
• CAFB-903 - CAFB-9 spent sorbent processed by dry sulfation
in a 10-cm fluidized-bed unit
• CAFB-904 - CAFB-9 spent sorbent processed by dry sulfation in
a 10-cm fluidized-bed unit, then separated by particle size
to two fractions which achieved different degrees of sulfation
• DB163 to 171 - nine CAFB-9 spent sorbents processed by dead-
burning at three different temperatures for three different
durations
13
-------
Table 4
CAFB SPENT SORBENTS TESTED
CAFB-Run
Fuel
Sorbent
CAFB-7
CAFB-8
CAFB-9
CAFB-10
CAFB-10A
High-S
residual oil
High-S
residual oil
High-S
residual oil
High-S residual oil
+ bitumen
High-S residual oil
+ coal and lignite
Denbighshire limestone
•f BCR 1359 limestone
BCR 1359 limestone
BCR 1359 limestone
+ Aragonite
BCR 1359 limestone
BCR 1359 limestone
CAFB-11
Lignite
BCR 1359 limestone
-------
DB44 ym ~ six CAFB-9 spent sorbents of -44 ym size processed
by dead-burning at two different temperatures for three dif-
ferent durations
DB-66+88 ym - six CAFB-9 spent sorbents of -66+88 ym size pro-
cessed by dead-burning at two different temperatures for three
different durations
Room temperature 4A, 4B, and 4C air cured for 7, 14, and
28 days - nine solid compacts prepared from three mixtures
of CAFB-9 spent sorbent and fly ash, and air cured in water
for three lengths of time
Hi-temperature 75-CF-22, 75-CF-26, 65-CF-30 - three solid
compacts prepared by hot pressing mixtures of CaS, CAFB-9
spent sorbent, and CaSO, with fly ash at 1050°C and
33,000 MPa (4800 psi).
Reference Material
The following reference materials were tested:
FGD residue. Unprocessed and processed S02 scrubber
sludges from conventional power plants with FGD systems
provide a comparison of power plant residue with a
currently commercialized process.
31
Lignite Ash. Lignite ash from (TUGCO) serves as a refer-
ence for lignite ash for residues from CAFB gasification of
lignite.
31
Valley Builder Supply Block. Representative blocks and
aggregates manufactured by Valley Builder Supply, a
potential contractor to utilize the CAFB spent sorbent
from the CAFB demonstration plant at San Benito, Texas,
were tested to provide reference for processed CAFB spent
sorbent.
Gypsum. Iowa ground gypsum No. 114 was used to provide a
reference for CaSO, leachability because of the large
amount of CaSO, present in the spent CAFB sorbents.
15
-------
EXPERIMENTAL PROGRAM AND TEST METHODS
The environmental impact of any disposed material is a function
of its physical and chemical properties as well as of the quantity
involved. Potential water pollution problems can be predicted from the
chemical characteristics of leachates, such as pH, specific ion concen-
trations, trace element dissolution, and total dissolved solids (IDS).
Disposal of the CAFB solid wastes may also create air pollution, odor
nuisance, and heat-release problems. To assess the environmental impact
of CAFB solid waste disposal and the suitability of waste material as
landfill, physical and chemical characteristics of the residue, leaching,
and heat-release properties were investigated.
Characterization
Chemical, physical, and morphological characterization of the
spent bed and carry-over material was carried out by optical microscopy,
scanning electron microscopy (SEM), energy dispersive analyses by X-ray
(EDAX), electron microprobe analysis (EMA), X-ray diffraction, thermo-
gravimetric analysis (TGA), emission and atomic absorption spectroscopy,
and wet chemical methods.
Leaching Tests
At this time, there is no standard EPA leaching test with
which the potential environmental contamination from a solid waste can
be assessed. A standard test has been proposed by EPA in the Federal
Register "Hazardous Waste Guidelines and Regulations"-'-^ under the
authority of RCRA Sec. 3001 to identify hazardous waste. We expect
this test, entitled "extraction procedure"(EP), to be promulgated
in December 1979.
16
-------
Parallel to the EPA effort, ASTM committee 19.12 (subcommittee
32
19.1203) is also developing a standard leaching test for solid waste
materials. A 48-hour shake method using either type IV reagent water
(ASTM D-1193 or pH = 4.5 sodium acetate-acetic acid buffer is proposed.
A shake test is proposed by both organizations.
In this study leachates were induced by the shake test that
9 33 34
Westinghouse developed prior to the EPA and ASTM efforts, ' ' unless
otherwise specified. Samples of waste stones were mixed with deionized
water in Erlenmeyer flasks at room temperature. An automatic shaker
capable of 70 excursions per minute was used to agitate the mixtures.
Among the parameters investigated were sorbent/water loading, sample
mixing time, and pH of the leading medium. The supernatants resulting
from this operation were filtered, and the filtrate was determined for
pH, specific conductance, TDS, calcium, magnesium, sulfide, sulfate,
trace metal ion and anion concentrations, and total organic carbon (TOG)
content. The solid samples before and after the leaching operation were
also analyzed for their chemical and physical characteristics. Since
CaSO^ is a major constituent of the waste stone, and leachates contained
high calcium and sulfate concentrations, a naturally occurring gypsum was
tested under similar leaching conditions for comparison.
Two shake procedures have been employed. These are described
below.
• Continuous shake test. It establishes equilibrium condi-
tions between the solid and its aqueous surrounding and
provides the worst possible case with respect to contam-
ination release. This method has been used by Westinghouse
since 1975 as one of the screening tests for determining
leaching properties of CAFB spent solids. Typically, a
1:10 solid-to-water ratio is used.
17
-------
• Intermittent shake test. A series of ten to fifteen
cycles of a 72-hour shake test was adopted as part of
the leachability study to provide leaching rate, aging
effect, and long-term leachability of the worst case and
to make possible the calculation of "total fraction
leached" for any specific ion or for TDS as a function
of total leach time or total leachate passing the sample.
Leachates were analyzed at the end of each interval, and
a fresh charge of ionized water was added for each
72-hour leach cycle. Typically, a 1:3 solid-to-water
ratio was used.
Both shake tests are more severe than conditions anticipated
under actual land disposal; results from the shake tests are expected
to project the worst.
Activity Tests
No standard EPA activity test exists. Under Sec. 3001 of
RCRA, EPA's Hazardous Waste Management Office is currently developing
test methods for reactivity criteria as an effort to define hazardous
waste. Their tests concentrate on hazardous properties such as
explosiveness and chemical and mechanical instability but do not apply
35
to residual lime.
The activity of residual lime in spent CAFB materials can be
determined by its heat release property on contact with water, as the
hydration reaction of CaO is extremely exothermic. Literature on
lime reactivity and slaking rate has been reviewed, including the ASTM
37
C110 for the slaking rate of quicklime (CaO), Murray's study of lime
reactivity as a function of porosity and shrinkage characteristics
38
during calcination, and American Water Works' standard on lime for
water treatment.
18
-------
The heat release activity of CAFB residue in this study was
measured calorimetrically. The temperature rise of a solid/water system
containing free CaO is a function of the solid/water ratio. In our
experimental effort to establish a screening test for the residual
activity in spent CAFB solids produced under varying processing con-
ditions, a solid/water proportion of 3 g to 20 ml (which is in the bulk
range specified by the ASTM-C110 test and by Murray's work) was found
empirically to provide much better repeatability than that from a higher
solid/water ratio that would give greater temperature rise but would
lack reproducibility, probably due to local heating. Higher solid/water
ratios were also used, however, because they provide higher sensitivity
and simulate rainfall onto the disposed solid.
Chromel-alumel thermocouples were used to monitor the tempera-
ture rise in the stone/water system with an Omega cold junction com-
pensator and a millivolt recorder. The heat release tests were conducted
on the actual spent sorbent and on carry-over fines from the CAFB pilot
unit at ERCA. Calcined and uncalcined limestone and dolomite samples
were also tested for comparison.
RESULTS
Unprocessed Residue
The actual CAFB residues from ERCA pilot-scale runs were
tested in this work. These can be further grouped as shown below.
Table 5 summarizes the typical compounds present as identified by
X-ray diffraction.
CAFB-7, 8, 9 Regenerator Material
Three batches of actual regenerator spent sorbents using
residual oil as the fuel were tested. Table 6 summarizes the chemical
analyses. Leaching tests were carried out under both aerobic and
anaerobic conditions - in other words, under air and nitrogen atmos-
pheres, respectively. The oxidation and leachability of sulfide ions
19
-------
Table 5
SPENT SORBENT CHARACTERIZATION BY X-RAY DIFFRACTION
Dwg.l7(AB31
Sample
CAFB-8
Gasifier Bed
CAFB-8
Gasifier Bed
CAFB-8
Regular Bed
CAFB-8
Regular Bed
CAFB-8
Stack Fines
CAFB-10A
Gasifier Bed
CAFB-11
Regular Bed
CAFB-11
Cyclone
CAFB-11
Stack Fines
Fuel
Resid. oil
Resid. oil
Resid. oil
Resid. oil
Resid.oil
Resid. oil
+ coal
+ lignite
Lignite
Lignite
Lignite
Physical
Separation
White particles
Black particles
White
Black
No separation
No separation
Chemical Composition
CaO
Minor
Major
- -
Major
Major
Major
Major
Ca
-------
Table 6
CHEMICAL ANALYSIS OF CAFB SPENT
SORBENTS FROM THE REGENERATOR
Ca
=
S
S°I
CAFB- 7, %
66.5
1.25
2.98
CAFB-8, %
60.5
3.89
2.31
CAFB-9, %
64.3
2.24
3.07
were affected by the oxygen partial pressure in the system. Table 7
summarizes the chemical characteristics of the leachates. Table 8
summarizes the trace metal contents in the spent regenerator sorbents
and their leachates. Results showed that:
• The leachability of trace metal ions is not expected to
cause water pollution.
• The leachates are alkaline with pH = 12.8.
• Concentrations of calcium, sulfate, sulfide, and TDS as
well as pH are major concerns.
• Total dissolved ions are higher for the anaerobic leaching,
as indicated by the specific conductance of the leachates.
• Sulfide is higher in the anaerobic leachates and sulfate
is higher in the aerobic case when all other conditions
are identical. This is reasonable because part of the
dissolved sulfides may be oxidized to sulfate under aerobic
mixing conditions.
e Gaseous H~S evolution from leachates over 240 hours con-
stitutes less than 1 percent of the total sulfide in the
stone. Note, however, that these tests were conducted in
deionized water at room temperature. In the case of acid
rainfall onto the disposed sulfide-containing stone, the
H2S evolution would probably be higher.
• Further processing of the spent stone is deemed necessary
in order to render it environmentally suitable for disposal.
21
-------
Table 7
LEACHING RESULTS OF SPENT CAFB REGENERATOR SORBENTS
0»<1. 257C927
Regenerator
Spent Sorbents
CAFB-9
CAFB- 7
CAFB-8
Experiment
Stone
loading
Mixing
time
Stone
loading
Mixing
time
Mixing
time
Conditions
4g/200 ml/24 hr, aerobic
20 g/200 ml/24 hr,
40 g/ 200 ml/ 24 hr,
80 q/ 200 ml/ 24 hr,
4 g/200 ml/24hr, anaerobic
20 g/200 ml/ 24 hr,
40g/200 ml/24 hr,
80 g/200 ml/24 hr,
20 g/200 ml/6hr, aerobic
20 g /200ml/ 24 hr, "
20 g/200 ml/ %hr, "
20 g/200 ml/ 150 hr, "
20 a /200ml/ 214 hr, "
20g/200 ml/6 hr, anaerobic
20 g/200 ml/ 24 hr, "
20 g/200 mil % hr, "
20 g/200 ml/ 150 hr, "
20 g/200 ml/ 214 hr^ "
1 g/250 ml/24hr, aerobic
25 g/250 ml/24 hr, "
10 g /250ml/ 24 hr, "
25 g/250 ml/ 24 hr, "
50 g/250 ml/ 24 hr, "
25 g/250 ml/ Ihr, "
25 g/250 ml/ 3 hr, "
25 g/250 ml/ 6 hr, "
25 g/250 ml/ 17 hr, "
25 g/250 ml/ 24 hr, "
25 g/250 ml/ 48 hr, "
10g/100 ml/48 hr, aerobic
lOg/100 ml/100 hr, "
10g/100 ml/240 hr, "
10 g/ 100 ml/432 hr, "
10 g/100 ml/48 hr, anaerobic
10 g/100 ml/100 hr, "
10 g/100 ml/240 hr, "
10 g/100 ml/432 hr, "
Chemical Characteristics of Leachates
pH
1Z6
12.7
12.6
12.5
12.64
12.64
12.5
115
12.5
12.7
12.6
12.8
12.9
12.6
12.7
lib
12.8
12.6
12.8
US
12.8
12.8
US
12.7
12.7
118
11 &
12.8
1Z8
12.3
lil
lil
12.4
12.3
12.1
12.1
11.7
Specific
Conductance.
M mhos-cm
6,300
7.390
8,900
1,340
6,900
8,380
9,580
14,200
6,790
7,890
8,920
9,180
9.330
7,060
8,380
9,840
10,490
10, 710
6,040
6,600
7,630
8,380
7,170
7,750
7,610
7,810
8,140
8,380
8,735
9,150
9,700
10,360
10,130
8,580
9,930
11,000
10,690
Ca.
mgtf
824
1,368
1,824
3,496
928
1,512
1.952
3,784
936
1.368
1,860
1,936
2,064
984
1,512
2,096
2,344
2,440
668
760
1,005
1,280
1,576
920
938
1,000
1,175
1,280
1,453
1,624
1,724
2,0%
2,176
1,352
1,752
2,064
2,232
S .
mg/t
106
435
576
2,560
166
659
928
5,080
230
435
627
1,062
883
214
659
1.338
1,734
1,888
6.4
214
73.5
185
485
US
31 0
54.3
191.5
185
329
432
264
744
784
936
1072
1376
SO.
mg/l
346
1,037
1,325
1,536
507
614
1,075
2,016
422
1,037
1,555
1,843
2.016
461
614
1,286
1,277
1,210
77
153
556
1,035
1,990
220
345
480
844
1,035
1,380
931
1,548
1,622
1,297
1,225
1,000
1,211
1,410
Gaseoys S.
*of S in
Solid
0.054%
0.054%
<0.3*
< 1%
<0. 01%
<0. 01%
<0. 01%
22
-------
Table 8
Dwg. 170*1833
TRACE METAL ELEMENTS IN THE UNPROCESSED CAFB REGENERATOR
SPENT SORBENTS AND THEIR LEACHATES
\Samples
Elements\
Ag
Al
As
B
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
Hg
Li
Mg
Mn
Mo
Na
Ni
Pb
Se
Si
Sn
Sr
Ti
V
Zn
Zr
Sb
Spent Sorbent, wt%
CAFB-9
< 0.0002
0.3
<0.02
< 0.002
< 0.0001
< 0.0007
>10
< 0.007
< 0.002
0.002
< 0.002
0.2
0.8
0.02
0.007
0.1
< 0.007
1
< 0.002
0.01
1
< 0.007
< 0.001
CAFB-8
<0.01
0.07
ND<0.01
ND<0.01
>10
ND<0.03
ND<0.01
NO < 0.03
<0.01
0.1
<0.03
0.33
0.05
ND<0.01
<0.1
0.03
ND<0.01
0.3
NO < 0.03
0.02
0.3
NO < 0.03
ND<0.03
NO < 0.03
Leachates, mg/£
CAFB-9
ND<0.02
1000
ND < 0. 3
ND < 0. 1
ND<0.05
ND<0.1
0.1
<0.1
0.4
ND<0.02
0.4
1
ND<0.02
NO < 0.05
ND«1
0.4
ND<0.2
> 10
ND < 0. 2
ND<0.05
NO < 0.5
ND<0.2
CAFB-8
<0.03
<1
<0.05
0.03
«0.1
<0.03
>1000
<0.03
<0.1
<0.03
0.08
0.03
< 0.001
<1
<0.03
0.08
<0.1
<0.1
<0.01
0.2
<0.1
<0.03
<0.03
<1
<1
<0.1
DWSe
0.05
0.05
1.0
1.0
0.01
0.05
1.0
0.3
0.002
0.05
2.0
0.05
0.01
1.0
5.0
ND - Not Detectable
" DWS - U.S. Public Health Service Drinking Water Standards
(USPHS 1972)
National Interim Primary Drinking Water Regulations
(NIPDWR, 1976)
World Health Organization Drinking Water Standards
(WHO, 1971)
23
-------
Leaching tests using the intermittent shake method and
activity tests are discussed in later sections.
CAFB-8 Gasifier Material
Both the gasifier and the regenerator spent sorbents are
granular, with varying color shades, as shown in Figure 1. They grad-
ually disintegrate into grayish powder on contact with moisture in
the air. The spent sorbent after leaching becomes a white-to-gray powder
consisting primarily of calcium carbonate (CaCOo) and slaked lime
(Ca(OH),,). Although the spent sorbent from the gasifier is not expected
to be disposed of directly, it is also tested for its leaching behavior.
Table 9 summarizes the results. As expected, results indicated less
desirable characteristics than those from the leachate of the regener-
ator stone, which is also judged unsuitable for direct disposal.
CAFB-8 Stack Fines
Effort was directed toward characterizing the stack fines
since the particulate emission from the CAFB process is a potential
concern.
Scanning electron microscopy (SEM) and energy dispersion
analysis by X-ray (EDAX) were used for chemical and physical characteri-
zation. Figure 2 is SEM photomicrographs of CAFB-8 stack fines illus-
trating variation in their physical characteristics. Some spherical
particles were present that resembled cenospheres in typical coal ash.
Larger particles were often agglomerates of finer particles. Figure 3
shows EDAX spectra of particles observed on SEM. An area scan by EDAX
for the entire area shown on SEM in Figure 3(a) showed that the CAFB-8
stack fines consisted mostly of calcium. X-ray diffraction identified
it to be CaO. Figures 3(b) and (c) show that even the submicron particles
were high in calcium with minor elements such as sulfur, silicon, sodium,
potassium, chlorine, iron, and zinc. Calcium oxide appeared to be the
major component in all phases of the CAFB-8 stack fines, with the
exception of the spherical particle shown in Figure 3(d), whose EDAX
spectrum showed it to be mostly iron.
24
-------
(a)
(b)
Figure 1 - Photomicrographs of (a) CAFB-8 Gasifier Material
(b) CAFB-8 Regenerator Material
25
RM-70683
-------
Table 9
LEACHING RESULTS FROM THE CAFB-8 GASIFIER SPENT SORBENT
Leaching Conditions
10 g, 100 ml, 48 hr, aerobic
10 g, 100 ml, 48 hr, anaerobic
10 g, 100 ml, 100 hr, aerobic
10 g, 100 ml, 100 hr, anaerobic
10 g, 100 ml, 240 hr, aerobic
10 g, 100 ml, 240 hr, anaerobic
10 g, 100 ml, 432 hr, aerobic
10 g, 100 ml, 432 hr, anaerobic
Leachate Characteristics
PH
12.3
12.3
12.2
12.0
12.1
12.0
12.0
11.8
Sp. Cond.,
ymhos-cm~l
8740
8790
10000
13600
11400
14800
11250
15700
Ca,
mg/£
1384
1256
1780
2400
2596
2880
2584
3440
Mg,
mg/Ji
9
31
31
31
12
19
5
5
s ,
mg/£
-
1888
704
2664
448
3392
928
2592
S0~ 4
mg/9.
300
213
745
18
2145
25
1272
144
i
-------
Figure 2 - SEM Photomicrographs of CAFB-8 Stack Fines Showing
Variation of Their Physical Characteristics
27
RM-71955
-------
32SEC 28662 I NT
v s : seee HS . SBEV/CH
ee |es
EDRX
(b)
(d)
Figure 3 - SEM and EDAX of CAFB-8 Stack Fines
28
RM-71954
-------
The amount of free carbon in the CAFB-8 stack fines was
determined by TGA to be in the range of 5 to 8 percent by weight.
Similar tests showed that the gasifier and regenerator bed materials
from the same run contained less than 2 percent free carbon.
Standard leaching tests were conducted on CAFB-8 stack fines.
Solid and leachate characteristics are summarized in Table 10. Note that
the stack fines contain lower sulfide and higher sulfate than does the
bed material, and the leachate of stack fines contains much less sulfide
than does that from the bed material.
Trace metal element contents in the bed material and stack
fines are compared for CAFB run 8. Results summarized in Table 11
indicate higher concentrations in the stack fines - for example,
chromium, copper, mercury, manganese, sodium, lead, and vanadium.
Table 11 also compares their leachates and indicates low dissolved trace
elements in both.
The only element that did not meet the stringent DWS is
mercury, whose concentration in the leachate of stack fines was 0.03 ppm
as compared with the DWS for mercury of 0.002 ppm. This is not neces-
sarily a problem because the amount of stack fines produced in a
typical plant is relatively small compared with the total amount of
spent solids from the bed.
CAFB-10, 10A Residue
CAFB-10 and 10A were runs in which mixed fuels were used
(residual oil, bitumen, lignite, and coal). CAFB-10A from ERCA was
run under the following conditions:
Sorbent - Limestone BCR 1359
Average gasifier temp. - 950°C
Average regenerator - 1100°C
Run length - 50 hr: 45 hr fuel oil
5 hr coal - 1.5 hr Texas lignite
3.5 hr Illinois'No. 6
29
-------
Table 10
CHEMICAL CHARACTERISTICS OF CAFB-8 STACK FINES AND LEACHATES
Sample
CAFB-8 Stack Fines
Leaching Conditions
Solid
Chemical Characteristics
Ca
46.7 wt %
Mg
0.62 wt %
S
0.18 wt %
SO4
7.19 wt %
Leachate
Leachate
Leachate
Leachate
10 g/100 ml/100 hr/aerobic
10 g/100 ml/100 hr/anaerobic
10 g/100 ml/196 hr/aerobic
10 g/100 ml/196 hr/anaerobic
1504 mg/1
1440 mg/1
1624 mg/1
1800 mg/1
7.2 mg/1
0
9.6 mg/1
9.6 mg/1
-
>100 mg/1
< 20 mg/1
370 mg/1
1339 mg/1
1116 mg/1
1094 mg/1
1094 mg/1
-------
Table 11
Dwg. 1689B48
COMPARISON OF TRACE METAL ELEMENTS IN REGENERATOR BED
MATERIAL AND STACK FINES OF CAFB-8
Substrate
Ag ^
Al
As
B
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
Hg
Mg
Mn
Mo
Na
Ni
Pb
Se
Si
Sn
Sb
Ti
V
Zn
Zr
Solid.
CAF8-8 Reg.
Bed Mat '1
<1
<1
<3
5
2
0.03
50
3
50
1000
10
1%
ppm
CAFB-8
Stack Fines
<1
<1
<3
10
5
4
100
3
>1000
1000
30
2%
Leachate
CAFB-8 Reg.
Bed Mat' 1
<0.03
<1.0
<0.003
0.03
«0.1
<0.03
>1000
<0.03
<0. 1
<0.03
0.08
0.03
<0.001
<1.0
<0.03
0.08
<0.1
<0.1
<0.003
0.2
<0.1
<0.1
<0.03
<0.03
<1.0
<1.0
,mg/f
CAFB-8
Stack Fines
<0.01
0.02
< 0.003
0.5
<1.0
<0.01
<0.01
Major
<0.01
<0.05
<0.05
<0.05
<0. 1
0.03
<1.0
<0.05
0.2
>5.0
<0.05
<0.05
<0.003
0.3
<0.05
<0.05
<0.05
<0.05
<1.0
<0.05
U.S. Drinking
Water Standards."
mqlt
0.05
0.05
1.0
1.0
0.01
0.05
1.0
0.3
0.002
0.05
2.0
0.05
0.01
1.0
5.0
* DWS: NIPOWR 1976, USPHS 1962,and WHO. 1971
31
-------
Figure 4 shows typical SEM photomicrographs and EDAX spectra of CAFB-10A
gasifier material at the surface and fractured surface of a spent sorbent
particle. EDAX spectra scanning the entire SEM area indicated the
presence of silicon, aluminum, potassium, iron, and vanadium in addition
to the major species calcium and sulfur. Higher sulfur is observed on
the particle surface.
Electron microprobe analysis (EMA) provides elemental profiles
of the particle cross-section. Figures 5 and 6 illustrate two types of
sulfur profiles found in spent sorbent particles of the CAFB-10A gasifier
sorbent. Figure 5(a) shows a photomicrograph of a cross-section of a
partially sulfided limestone particle blocking the area scanned for
calcium, sulfur, iron, silicon, and aluminum shown in Figures 5(b) to (f).
The concentration of an element is proportional to the intensity of the
X-ray counts. Calcium is evenly distributed, and sulfur concentrates on
the particle periphery, as do iron and silicon in this case. Figure 6
shows an opposite sulfur gradient with sulfur depletion at the particle
surface. We suspect that this type of particle is formed during
regeneration when a fully sulfided limestone particle is partially
regenerated to CaO, which is more concentrated at the surface of the
particle. A third type of sulfur configuration, not shown in these
figures, has sulfur evenly distributed throughout the particle.
Table 12 summarizes the leaching results and indicates the
following:
• Leachates are high in pH and TDS attributable to CaO present
as a major species in the solid.
• Sulfide in the leachate is lower than the previously tested
CAFB spent sorbents as is consistent with the lower sulfide
content present in the CAFB-10A gasifier solid.
• Sulfate in leachate is dominated by the CaSO, present in
the solid, which is higher in CAFB-10A spent sorbent than
in the previously tested CAFB spent stones.
32
-------
(a)
(b)
U)
(c)
16SEC 33318INT
v s . seee _geEv/CH
(d)
EDRX
Figure 4 - SEM and EDAX of CAFB-10A Gasifier Bed Material
(a) (b) particle surface
(c) (d) fractured surface
-------
(a)
(b)
(c)
(d)
Figure 5 - (a) Photomicrograph of a Cross Section of a Spent
CAFB-10A Gasifier Sorbent Particle Blocking the
Area for Electron Microprobe Analysis
(b) EMA Area Scan for Ca, (c) for S, (d) Fe, (e) Si,
(f) Al
34
RM-70681
-------
(a)
(b)
(c)
(d)
(f)
Figure 6 - (a) Photomicrograph of a Cross Section of a Spent
CAFB-10A Gasifier Spent Sorbent Particle Blocking
the Area for EMA Scan
(b) EMA Area Scan for Ca, (c) S, (d) Fe, (e) Si,
(f) Al
35
-
-------
Table 12
CHEMICAL CHARACTERISTICS OF CAFB-10A GASIFIER
MATERIAL AND ITS LEACHATES
Dwq. 1704B32
OJ
Samples
CAFB-10A
Gasifier Stone.
urf OL
Leachates,
mg//
Leaching Conditions
Before leaching
After leaching
10/g/100 ml/100 hr/aerobic
10 g/100 ml/100 hr/aerobic
10 g/100 ml/100 hr/anaerobic
10 g/100 ml/196 hr/aerobic
10 g/100 ml/196 hr/anaerobic
Chemical Characteristics
PH
-
-
12.2
12.2
12.3
12.3
Specific
Conductance,
pmhos/cm
11130
11230
11740
8620
Ca
57.6
*
1708
1768
1572
1472
Mg
0.83
ft
<10
<10
<10
<10
s
0.78
*
£
150
91
374
—
SU4
9.62
<•
1263
1311
1395
1139
—
CO,
0.8
21
•*
ft
fr
*
—
OH
0.17
5,1
*
*
^
*
Not determined
-------
« The leached stones contain much more CaCOH)^ and CaCO,,
than does the original stone due to the hydration and
carbonation of CaO during the leaching process.
In order to correlate the various EPA contractors' efforts in
the area of CAFB spent sorbent disposal, samples were requested and
39
received from the Ralph Stone Company. These included five batches of
33 34 40
Exxon and PER spent sorbent and fly ash from the FBC process ' ' and
two CAFB spent solids from the ERCA pilot unit.
Leaching studies were carried out on the CAFB spent materials.
Two methods were employed: the continuous leach test reported previously
and an intermittent leach test.
Figure 7 shows results from the continuous leaching. Two
points are noted. First, calcium and sulfide increase with mixing time,
indicating that CaS equilibrium between the solid and aqueous phase is
not achieved in 200 hours. Secondly, the CAFB-10A bed and CAFB-10
gasifier fly ash display similar leachate characteristics except that
higher dissolved sulfide is found in the leachate of the bed material,
consistent with the solid analysis.
Results from the intermittent shaker tests of several CAFB
residues are shown in Figure 8. Several points can be noted:
• All leachates had similar pH and sulfate that improved
only very slightly with total leachate volume and time.
• The repeatability of the two batches of CAFB-10A was good
(CAFB-10A and RS-CAFB-10A).
• CAFB-8 regenerator material, which had higher sulfide
content in the solid, produced leachate with higher S ,
Ca, and TDS, as would be expected from the greater CaS
dissolution.
• Initial TDS was worst for CAFB-8 regenerator sorbent and
best for CAFB-10 fly ash. All converge to a similar value
after several 72-hour intervals.
37
-------
Curve 690793-B
300
200
100
0
2000
1000
2000
1000
o_
E
o
i/>
o
o
O
14
12
10
8
6
8
6
4
o RS-CAFB-lOAGasif. Bed
a RS-CAFB-lOGasif. Fly Ash
100 200
Total Continuous Leach Time, hr
Figure 7 - Leachate Characteristics as a Function of Total
Continuous Leach Time for the CAFB Samples
Obtained via the Ralph Stone Co.
38
-------
Curve 691326-i
Normalized Leachate Quantity. m//g Starting Solid
30 36 42
ouu
*, 600
01
i 400
"3
to
200
0
^,2000
f
§1000
'o
(0
o
0
2000
en
15
"5
0
12
ft 10
8
6
1
•£ 10
o
I 8
I 6
1 4
o
o 2
OJ
o.
l/l
1 1 1 1 1 1 1
N PAFR 10A fiaiif Red
v ............ PC-P4FR-inA fiacH Rwi
- X. , RS-CAFB-10 fiasif Ash
v. — — CAFB-8 Reqenerator Bed
"^•--. """^-^ — — __
i i i i i l i
i i i i i i i
i i i i i i i
i i i i i ii
- r.^i — . ' l ' ' ' ' -
-
2 4 6 8 10 12 14
n = Total No. of 72 hr Intermittent Leaching
i i i
360 720 1080
Total Leach Time= (72) (n)hr
Figure 8 - Leachate Characteristics as a Function of
Intermittent Leaching for the CAFB Samples
39
-------
(a)
(b)
Figure 9 - (a) SEM Photomicrograph and (b) EDAX Spectrum of
the White Precipitate Formed Readily in Air
from the Leachate
40
RM-71557
-------
e CAFB spent solids tested so far contained high concen-
trations of CaO, and their leachate did not seem to
improve considerably with time.
White crystalline precipitate found on the leachate surface
when the leachate was stored overnight has been identified by X-ray
diffraction and by TGA to be CaCO- (calcite) that must have been formed
by carbonation of dissolved calcium with carbon dioxide (CO,-,) in air.
Figure 9 shows a SEM and EDAX of such precipitate. Trace metal elements
were determined on these solids and their leachates. Results from the
CAFB spent materials which are presented in Table 13 show that the trace
metal element content in these leachates is below the U. S. drinking
water standards. This is consistent with our previous report based on
analyses of other batches of spent sorbent from the CAFB process.
CAFB-11 Residue
, CAFB-11 was a 100 hr run using Texas lignite, during which
* / 1 9A
' GCA carried out the Level I environmental sampling. The operating
x
conditions are summarized in Table 14. Four types of samples collected
by GCA personnel during the run were tested for the environmental impact
of disposal.
The gasifier and regenerator bed materials were granular,
similar to the previously tested spent sorbents from residual oil runs.
Figure 10 shows microphotographs of a cross-section of a spent sorbent
particle from the regenerator and elemental profiles (Ca, Mg, S, Si,
Al, Fe, and C) on an area near the surface. Calcium is evenly distributed
in the calcium-based sorbent particle. Sulfur, silicon, aluminum, and
iron are more concentrated on the particle periphery, suggesting an ash
deposit at the particle surface of approximately 10 ym thickness.
Carbon, however, is depleted at the particle surface where ash coating
exists. The gasifier and the regenerator residues appear to be very
similar.
41
-------
Opt
ograph
Figure 10 - Electron Microprobe Analysis of Spent Regenerator
Bed Material from CAFB "Lignite" Run
42
RM-77934
-------
Table 13
Dxg. 1689647
TRACE METAL CONTENT IN THE CAFB SPENT SORBENTS OBTAINED
THROUGH RALPH STONE CO. AND THEIR LEACHATES
Substance
Ag
Al
As
B
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
Hg
Mg
Mn
Mo
Na
Ni
Pb
Sb
Se
Si
Sn
Sr
Ti
V
Zn
Zr
Solid (w%)
RS-
CAFB 10A
Gasif. Bed
>10
< 0.003
0.01
0.0001
<0.0003
»10
<0.003
< 0.0005
0.003
0.005
>10
1.0
0.005
0.001 j
<0.03
0.01
< 0.001
>10
0.0003
0.02
0.03
<0.01
<0.01
RS-
CAFB-10
Gasif. Fly Ash
3
<0.003
0.001
<0.0001
<0.0003
»10
<0.003
<0.0005
0.003
0.003
3
0.3
0.005
0.001
' <0. 03
0.03
0.001
>10
<0.0003
0.02
0.3
<0.01
<0.01
Leachate (mg/£)
RS-
CAFB 10A
Gasif. Bed
<0.01
0.05
0.003
0.8
<1.0
<0.01
<0.01
Major
<0.01
<0.05
<0.05
<0.05
<0.1
<0.001
<1.0
<0.05
0.1
r~<5.o
<0.05
<0.05
<0.05
0.003
5.0
<0. 05
>5.0
<0.05
<0.05
<1.0
<0. 1
RS-
CAFB-10
Gasif. Fly Ash
<0.01
0.05
0.003
0.5
<1.0
<0.01
<0.01
Major
<0.01
<0.05
<0.05
<0.05
<0.1
<0.001
<1.0
<0.05
0.1
>5.0
<0.05
<0.05
<0.05
<0.003
5.0
<0.05
>5.0
<0.05
<0.05
<1.0
<0. 1
. j. unriKiny
Water Standards.
mg/f
0.05
0.05
1.0
1.0
0.01
0.05
1.0
0.3
0.002
0.05
2.0
0.05
0.01
1.0
5.0
A3
-------
Table 14
CAFB-11 OPERATING CONDITIONS
Average Coal Feed Rate
Average Line Feed Rate
Air to Gasifier
Air to Regenerator
Temp, in Regenerator
Regenerator Bed Depth
Gasifier Bed Depth
Regenerator Drain
211 kg (465 lb)/hr
10.4 kg (23 lb)/hr Measured
3682-4184 dm3 (130-170 df)/min
595-736 dm3 (21-26 cf)/min
Set at 1055°C by
61-127 cm (24-50 in)
56-61 cm (22-24 in)
3
Set at 113 dm (4 cf)/hr ERCA
Regenerator SO-
Regenerator C02
Regenerator 00
0-1.2%
5-17%
0.2-5%
Measured
by
ERCA
Stack SO,
173 ppm - GCA
260 ppm - Avg. for day
by ERCA
44
-------
The residue from the main cyclone consisted of finer
granular sorbent particles, ash, and carbon. The ash content (Si, Al)
in the CAFB-11 cyclone carry-overs was much higher than the cyclone ash
from the oil gasification runs. Figure 11 shows SEM and EDAX of the
main cyclone and stack cyclone fines. Unlike the main cyclone ash, the
stack fines from the Texas lignite run consisted of mixtures of sorbent
fines and cenospheres. The latter were not seen in the oil gasification
residues. The SEM and EDAX of these are shown again in Figure 12, where
chemical and physical characteristics are correlated for various
particles. In general, the spent sorbent fines are of irregular shape
and are predominantly calcium. The very bright, nonspherical particles
are SiCL (quartz). The cenospheres were high in silicon and aluminum.
The chemical compositions and leaching properties of CAFB-11
residues were determined. The results are shown in Tables 15 and 16.
The following points are worth noting:
• The gasifier and the regenerator materials appear to be
similar not only in physical characteristics but also in
chemical composition. Therefore, leaching tests were
carried out only on the regenerator material.
• The carry-over materials contained a much smaller amount
of sorbent fines than did the carry-over from the oil
gasification runs. Thus, calcium and TDS were also lower
in the leachate of CAFB-11 carry-over.
• Sulfur content (both S and SO, ) was low in the residues
from the lignite run, due to the low sulfur content in
Texas lignite.
• Trace elements were more concentrated in the carry-over
and were highest in the stack fines (B, Ba, Ci, Cu, Mu, Mo,
Ni, Pb, Sr, Ti, Zr).
o Leachate from CAFB-11 bed material was similar to the
leachate from the oil gasification residues except for
the lower S and SO, concentrations in the former.
4
45
-------
Main Cyclone
Stack Cyclone
Figure 11 - SEM and EDAX of Stack Cyclone Fines from
CAFB "Lignite" Run Material
VJ
VJ
w
-------
Al & (4. ft
wv c*
Al Si K (j T.
SEM and EDAX of Stack Cyclone Fines
from CAFB "Lignite" Run
RM-77933
-------
Table 15
SOLID AND LEACHATE CHARACTERISTICS OF SPENT
MATERIAL FROM CAFB "LIGNITE" RUN
Gasifier Bed
Regenerator Bed
Main Cyclone
Stack Cyclone
Solid, wt %
Ca
49.6
52.1
6.4
8.7
Mg
0.8
0.3
0.5
1.3
S
0.22
0.1
0.2
0.13
so4
0.1
0.97
0.2
2.7
Leachate, mg/S.
PH
11.7
11.7
11.1
11.4
10.3
10.9
^ * v> m 9
y mhos /cm
7690
8250
1330
2400
1150
1310
Ca
812
888
152
204
240
232
Mg
<10
<10
<10
<10
<10
<10
S
37
100
38
56
so4
206
200
77
38
544
343
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
-p-
oo
-------
Table 16
Dwg. 2618C99
CHEMICAL CHARACTERISTICS OF CAFB "LIGNITE"
RUN RESIDUES AND LEACHATES
Substance
L Al
L Ag_
As
B
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
, Fe
l~~ Hq
Mg
Mn
Mo
Na
Ni
Pb
Sb
Se
Si
Sn
Sr
Ti
V
Zn
Zr
so.
S =
so.
F
Cl
Br
NO,
N031000
>1000
100
0.1%
0.97%
"1000
300
1000
0.2%
0.13%
~T7%"
(3)
Major
<1
1000
1000
<1
<1
8.7%
<3
<10
100
10
Major
1.3%
1000
10
1000
30
50
<50
Major
<10
>1000
»1000
1000
1000
0.13%
2.7%
-3%
(b)
Leachate, mg/t
IDAe
<1
<0.01
<0.05
2
<1
<0.01
<0.01
w/,mm.
<0.01
<0.04
<0.03
<1
<0.2
< 0.002
<10
<0.01
0.06
2
<0.03
<0.03
<0.1
<0.01
0.6
<0.1
>1
<0.1
<0.05
<4
<1
<10
37
206
1.6
11
<1
<1
<1
< 1
<20
% ii.7^
I7690!i
ID An
<1
<0.01
<0.05
2
<1
<0.01
<0.01
Y///.mm
<0.01
<0.04
<0.03
<1
<0.2
< 0.002
<10 j
<0.01
<0.06
2
<0.03
<0.03
<0.1
<0.01
1
<0.1
>1
<0.1
<0.05
<4
<1
<10
100
200
1.9
12
<1
<1
2
<1
<20 ,
'% 11.7^
^8250 %
(2) Ae
>1
<0.01
<0.05
1
• <1
<0.01
<0.01
'////Art*///.
<0.01
<0.04
<0.03
<1
^ \'%%
< 0.002
<10
<0.01
0.2
>1
<0.03
<0.03
<0.1
<0.01
>1
<0.1
>1
<0.1
<0.02
<4
<1
<10
38
77
2^7.9'^
11
<1
<1
•a
<1 n
<20
^ 11.1^
i133°f
(2)An
>1
<0.01
<0.05
1
<1
<0.01
<0.01
'//A 204 W.
<0.01
<0.04
<0.03
<1
<0.2
< 0.002
<10
<0.01
0.06
>1
<.0.03
<0.03
<0.1
<0.01
>1
<0.1
>1
<0.1
<0.05
<4
<1
<10
56
38
^8.4^
13
<1
<1
T75~
<1
<20
ifTi»
§2400P
(3IAe
<1
<0.01
<0.05
1
<1
<0.01
<0.01
Y///wW,
<0.01
<0.04
<0.03
<1
y/-,> \'tff/
< 0.002
<10
<0.01
0.3
>1
<0.03
<0.03
<0.1
>1
<0.1
>1
<0.1
<0.09
<4
<1
<10
'm.^m
2.4
23
1.8
20
7
<1
<20
^1U.3^
iliw^
(3)An
<1
<0.01
<0.05
1
<1
<0,01
<0.01
^232-^
<0.01
<0.04
<0.03
<1
<0.2
< 0.002
<10
<0.01
<0.05
1
<0.03
<0.03
<0.1
rm^m
>i
<0.1
>1
<0.1
<0.05
<4
<1
<10
WiVAW,
W/,i.r////
72
<1
22
12
<1
<20
^.'0.9/^
Si3ioi
let
DWS, mg//
0.05
0.05
1.0
200
0.01
0.05
IJO
0.3
0.002
150
0.05
2.0
0.05
0.01
1.0
5.0
250
2.4
250
10
5 to 9. 0
-750
(a) (II Regenerator Bed Material
(2) Main Cyclone Material
(3) Stack Cyclone Material
-------
• The anaerobic leachate contained higher Ca, S , and TDS,
in general, than did the aerobic.
• DWS were met by the bed leachate but exceeded (Fe, F, Se)
by the leachate from the carry-over. Leachate from TUCCO
ash (a Texas lignite ash from a conventional boiler) also
exceeded the DWS for Cr and Se, as will be discussed in a
later section.
• Like the oil gasification residue, Ca, SO^, pH, and TDS
were major concerns for the leachate.
Note that CAFB-11 was the only residue from the Texas lignite
test at the time of this work. The residues, thus, may not be repre-
sentative because of the unstable conditions existing during at least
part of the test duration.
The heat-release property of CAFB-11 summarized in Table 17
falls within the range found for the residues from the oil run, which
will be discussed in a later section.
Processed Residue
Dry Sulfation
The dry sulfation (DS) scheme is designed to sulfate the spent
regenerator material (CaO, CaS) with the S0? from the regenerator
ff 3,9,12
off-gas. ' '
Four samples that were sulfated to various degrees were investi-
gated in this category. Table 18 summarizes the samples and their sul-
fate and sulfide contents. The leachate characteristics were determined
as functions of stone load and mixing time. Figures 13 and 14 present
leaching results of the DS mix and compare them with CAFB-7 regenerator
stone before sulfation. Since the sulfated product is largely CaSO,,
leaching results of a natural gypsum (Iowa Gypsum No. 114) are also
presented for comparison. From Figures 13 and 14 one could make the
following points:
• Sulfide in the leachate was drastically reduced by the dry-
sulfation processing of the CAFB regenerator .stone.
50
-------
Table 17
RESIDUAL ACTIVITY OF SPENT CAFB "LIGNITE"
RUN MATERIAL BY HEAT-RELEASE
Sample Source
Gasifier Bed
Regenerator Bed
Main Cyclone
Stack Cyclone
Max. Tern
3p/20 m£
20°C (10 min)
17.5°C (10 min)
1.3°C (3 min)
<0.2°C
D. Rise
8g/2 m£
163°C (3 min)
133°C (3 min)
16°C (10 min)
<0.2°C
Table 18
SULFUR CONTENTS IN CAFB-9 SPENT SORBENT AND
DRY-SULFATED CAFB-9 SPENT SORBENT
Spent Sorbents
Processing History
Sulfate,
wt %
Sulfide,
wt %
CAFB-9
CAFB-903
CAFB-904
CAFB-904
(125-177 urn
fraction)
Actual spent sorbent from
the regenerator bed of
ERCA's pilot plant
^50 m % sulfated CAFB-9
in the 10-cm fluidized-
bed laboratory unit
79 m % sulfated CAFB-9
(44 to 420 um)
94 m % sulfated CAFB-9
(125 to 177 um)
3.07
40.2
2.24
0.59
65.2
68.8
0.16
0.1
51
-------
e 1000
oo
en
CL
CD
O
c.
rrj
8000
-!
-5 'E 6000
§ V
o ° 400°
•5 1.2000
50 100 150
Mixing Time, hrs
200
Figure 13 - Leachate Characteristics as Functions of
Batch Mixing Time for:
o CAFB Regenerator Stone No. 7
A 76 m% CAFB-7 - DS mix
Q Iowa Gypsum No. 114
52
-------
Curve 680706-B
CD
13
oo
00
CJ
12
10
8
A
1 1 1 1
— —
— —
1 1 1 1
I
8000
0 4000
E 6000
o V
U-l
o
•g 12000
Q_
GO
50 100 150
Stone Loading, g/£
200
Figure 14 - Leachate Characteristics as a Function
of Stone Loading for:
o CAFB Regenerator No. 7
A 76 m% CAFB-7 - DS mix
Q Iowa Gypsum No. 114
53
-------
• Sulfate concentrations in both the CAFB regenerator stone
and the sulfated DS mix exceeded the DWS (25C mg/£).
Leachates from a natural gypsum, however, contained
similarly high dissolved sulfate, which was consistent
with the saturated CaSO, solution.
• Gypsum leachates had lower pH, calcium, and total
dissolved ions than did the 76 m % CAFB spent stone.
Spent sorbent CAFB-9 was sulfated to various degrees (CAFB-903,
CAFB-904). The sulfated CAFB-904 was further sieved to separate the
fraction of smaller particle size (125-177 pm which achieved a 94 m %
3 9 12
sulfation. ' ' Leaching tests were conducted separately on these
differently sulfated spent sorbents. A general trend was noted -
leachate calcium, sulfide, IDS, and pH decreased with an increasing
degree of sulfation. Figure 15 compares leachate sulfide for aerobic
and anaerobic cases and shows that sulfide concentration was much less
under aerobic conditions. It also shows that the sulfide in the leachate
was significantly reduced by the degree of sulfation. Similar plots are
shown in Figure 16 for specific conductance which are a good approximation
_i
for TDS: 1.5 ymhos-cm is approximately equivalent to 1000 mg/£. IDS
are lower under aerobic leaching and decrease with increasing sulfation.
Leachate pH is high for unsulfated and partially sulfated spent sorbent
but falls within the water quality criteria range for the 94 m % sulfated
sample. Trace metal contents were also determined and indicated little of
concern.
In summary, the leaching results of the sulfated spent sorbent
demonstrated that the leachate quality is significantly improved by
"dry sulfation" processing of the spent sorbents from the CAFB gasifi-
cation process so that the potential water pollution would be greatly
reduced.
Dead-Burning
Processing by dead-burning aims to deactivate the CaO activity
by high-temperature sintering.
54
-------
Curve 682331-A
2000
1500
• CAFB-9, Unsulfaled. Anaerobic
o CAFB-9, Unsulfated, Aerobic
50m%Sulfated, Anaer.
50 m% Sulfated, Aer.
79m%Sulfated. Anaer.
0 79m%Sulfated, Aer.
94 m% Sulfated, Anaer.
r 1000
c
o
Ln
100 200
Mixing time, hour
Figure 15 - Comparison of Dissolved buiride
in Leachates of Sulfated and
Unsulfated CAFB-9 Spent Sorbent
300
• CAFB-9, Unsulfated, Anaerobic
o CAFB-9, Unsulfated, Aerobic
• 50m% Sulfated. Anaerobic
n 50 m% Sulfated. Aerobic
+ 79m% Sulfated, Anaerobic
0 79m% Sulfated. Aerobic
* 94m% Sulfated, Anaerobic
^ 94m% Sulfated, Aerobic
100 200
Mixing time, hour
Figure 16 - Comparison of Specific Con-
ductance of Leachates of
Sulfated and Unsulfated
CAFB-9 Spent Sorbent
-------
Leaching studies were carried out on numerous dead-burned
3 9 12
CAFB-9 spent sorbent from the CAFB gasification pilot plant. ' '
Table 19 summarizes some of these dead-burned samples and compares their
chemical compositions, especially sulfide and sulfate contents, with
the original spent sorbent before dead-burning. Two points should be
made: the dead-burning process reduced the sulfide content to negligible
levels, and dead-burning at 1250°C increased the sulfate content in the
stone and at 1550°C decreased the sulfate content. These are clear in
the light of the CaS oxidation at 1250°C and CaSO, decomposition at 1550°C.
Table 20 summarizes the leachate characteristics of these samples. The
stones sintered at temperatures equal to or above 1250°C contained CaS
sufficiently low that no measurable sulfide was found in their leachates.
Leachates from stones sintered at 1550°C contained no detectable sulfide
and also had a sulfate level below the DWS.
Although the leachate sulfide and sulfate were reduced by
dead-burning processing, the pH, calcium, and TDS were not satisfactorily
improved because of the formation of Ca(OH)2.
Another observation worth noting is that the dead-burned samples
before leaching were grey, lumpy solids whose darkness increased with the
degree of sintering. The solids after leaching, however, were signifi-
cantly swollen, ranging from an off-white fluffy mass to a pure white,
crystalline powder in the reverse order - in other words, the whitest
powder was the leached sample sintered at the highest temperature for
the longest time. One possible explanation may be that the hydration
and carbonation rates are decelerated by the degree of sintering; there-
fore, the whiter, more crystalline products were formed by the slower
reaction during leaching of the more dead-burned spent sorbents.
The residual solids after leaching were determined by X-ray
diffraction, TGA, and wet-chemical methods to consist of Ca(OH)? and
CaCO- as major species. Figure 17 shows TG curves of some processed
CAFB-9 spent stones. The top two curves show thermodecomposition of
the residual solid after 200-hr aerobic leaching of dry-sulfation
samples. A small amount of CaCO~ is seen to decompose at point c for
56
-------
Table 19
COMPARISON OF CHEMICAL COMPOSITIONS OF CAFB-9 SPENT
SORBENT BEFORE AND AFTER DEAD-BURNING
Initial CAFB
Particle Size,
urn
Sintering
Temperature, °C
Chemical Composition, wt %,
before Leaching
Sintering
Time, hr
S
S04
0 to 44
0 to 44
0 to 44
0 to 44
0 to 44
0 to 44
63 to 88
63 to 88
63 to 88
63 to 88
63 to 88
63 to 88
CAFB-9
0-3000
1250
1250
1250
1550
1550
1550
1250
1250
1250
1550
1550
1550
Spent sorbent
before dead-burni
2
5
24
2
5
24
2
5
24
2
5
24
ng
0.0006
0.0004
0.009
0
0
0
0.0428
0.0216
0
0.006
0.0186
0
2.24
7.08
8.64
8.52
0.48
0.6
0.48
7.296
7.368
6.552
0.96
1.032
0.984
3.07
57
-------
Table 20
LEACHATE CHARACTERISTICS OF DEAD-BURNED CAFB-9 STONES
Dead-Burning
Conditions
0 to 44 un, 1250°C, 2 hr
0 to 44 urn, 1250°C, 5 hr
0 to 44 pm, 1250°C, 24 hr
0 to 44 pm, 1550°C, 2 hr
9 to 44 um, 1550°C, 5 hr
0 to 44 um, 1550°C, 24 hr
63 to 83 um, 1250°C, 2 hr
63 to 88 urn, 1250°C, 5 hr
63 to 88 um, 1250°C, 24 hr
63 to 88 ym, 1550°C, 2 hr
63 to 88 urn, 1550°C, 5 hr
63 to 83 um, 1550°C, 24 hr
Leaching Conditions
2 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr/aerobir
4 g/100 ml/430 hr/aerobic
2 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr, aerobic
4 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr/aerobic
2 g/100 ml/430 hr/aerobic
2 g/100 ml/430 hr/aerobic
4 g/100 ml/430 hr/aerobic
Leachate Characteristics, mg/1)
pH
12.5
12.5
12.5
12.6
12.6
12.6
12.4
12.4
12.4
12.5
12.5
12.6
Sp. Cond.
(umhos/cm)
8010
7870
3290
8240
7590
7590
8520
8340
8340
7630
7940
7940
Ca
988
1362
1388
1274
360
840
1380
1322
1320
828
844
846
Mg
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
S
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
<5
so4=
1042
1481
1486
1214
134
163
1560
1229
1428
132
113
82
00
-------
Curve 682724-A
20
18 -
16
14
12
**. "*"* Q
10
8
I ! I
Dry-sulfation sample 904, 125 to \77\im
fraction after 200 hr aerobic leaching
Dry-sulfation sample 904 composite after
200 hr aerobic leaching
Dead-burned 171-1 after 200 hr aerobic
leaching
- Dead-burned 170-1 before leaching
Dead-burned 164-1 before leaching
j L
I i
0 200 400 600 800
Temperature, °C
1000 1200
Figure 17 - Thermogravimetric Curve of Processed Spent Stones
59
-------
sample 904 composite, and the major component, CaSO,, begins to decom-
pose at point d. Dead-burned sample 171-1 (1550°C, 24 hr) after
200 hours of aerobic leaching is shown to consist of a small amount of
surface water at point a, major CaCOH)^ at b, CaCO~ at c, and some CaSO,
starting to decompose at point d. Dead-burned sample 170-1 (1550°C,
5 hr) before leaching is shown to contain some Ca(OH>2, and dead-burned
sample 164-1 (1070°C, 5 hr) before leaching contains both Ca(OH)2 and
CaCO_, indicating that hydration and carbonation take place in air
even with dead-burned spent stone. This finding illustrates the point
that the dead-burning process up to 1550 °C and 24 hours does not perma-
nently deactivate the stone but merely slows down the hydration rate so
that no immediate heat release is detected on contact with water.
No gaseous H?S was detected (<1 ppm) during leaching. The
aerobic leachate contains slightly less calcium, sulfate, and TDS than
the anaerobic leachate. Trace metal ions in leachate would be no
problem.
ERCA conducted "weathering" tests of the sintered spent
stone by exposing the residue to outdoor conditions. Table 21 compares
the environmental impact projected by Westinghouse and ERCA.
Room-Temperature Ash Blending
Solid compacts can be formed by blending the spent CAFB stone
3 9 12
with fly ash and casting them at room temperature. ' '
Nine solid compacts prepared from three proportions of spent
sorbent and fly ash mixtures and cured in water for three lengths of
time were investigated for their leaching behavior. Table 22 summarizes
3 9 12
the results. ' ' Two methods of leaching were adopted. In the first,
the solid compact was ground to powder, and the standard shaking
was then applied. In the second, a chunk of the compact was broken off
and then immersed in a flask of deionized water. The mixture that had
the same solid-to-water ratio as the powder/water mixture was kept
60
-------
Table 21
ENVIRONMENTAL IMPACT OF SINTERED (DEAD-BURNED) SPENT SORBENT
WJ Laboratory-Scale Test
ERCA Weathering Test
Heat Release
Ca(OH)2/CaC03
Formation
Sintering Temp.
Trace Metal
Elements
Major Concern
Long-Term
Weathering
Nonsintered stone, T /2Q - = 18°C
Sintered stone T0 /ori , < 0.2°C
3g/20 ml
Hydration of sintered CaO followed by
carbonation takes place during
leaching (because sintered stone is
not truly dead-burned)
Sintering at 1250°C converts CaS to
Sintering at 1550°C decomposes
to CaO
Leachate of 1250°C sintered stone
contains high 864
Leachate of 1550°C sintered stone
contains little
• Meet drinking water standards
High pH, TDS, Ca in leachate
• Environmentally stable CaCOo will
eventually be formed
Nonsintered T = 30°C (1st hr)
Sintered T = 5°C (20 hr)
All sintered CaO converts to
Ca(OH)2 in 2 mos; 50% Ca(OH)2
converts to CaCO- in 12 mos.
weathering
Sulfide/sulfate content unclear
Sintering temp. 1350-1550°C
had no effect on weathering
(804 in leachate not measured)
Not monitored extensively
• High pH, Ca in leachate (TDS
not determined)
• CaC03 increases with weathering;
Ca(OH)2 decreases after peaking
at 2 mos.
-------
Table 22
Owg. 1704B3''
LEACHATE CHARACTERISTICS OF ROOM-TEMPERATURE PROCESSED SOLID
COMPACTS OF CAFB-9 REGENERATOR STONE AND FLY ASH
^^Du ration
Sample ^\
4A - 7 days
4A - 7 days
4A - 14 days
4A - 14 days
4A - 28 days
4A - 28 days
4B - 7 days
4B - 7 days
4B-14days
4B-14days
4B-28days
4B-28days
Leaching Conditions
Solid Form
Chunk
Crushed powder
Chunk
Powder
Chunk
Powder
Chunk
Powder
Chunk
Powder
Chunk
Powder
Shaking
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
Solid/Water
10 g/lOOm 1/256 hr
aerobic
10 g/lOOm 1/256 hr
aerobic
10 g/100 m 1/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 m 1/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 m 1/256 hr
Leachate Characteristics, mg/1 ^
PH
12.5
12.6
12.4
12.4
12,3
12.4
12.5
12.5
12.4
12.4
12.3
12.4
Sp.Cond..
umhos/ctn
8090
8440
8440
8540
8000
8400
8770
8810
8730
8700
8290
8740
Ca
1360
1488
1380
1440
1296
1360
1600
1680
1456
1488
1336
1464
Mg
0
0
0
0
0
0
0
0
0
0
0
0
S
<0.1
<0.1
0
0
0
0
<0.1
0.1
0
0
0
0
5°4
1613
1987
1752
1920
1766
1814
2189
2438
1872
1968
1752
1944
-------
Table 22 (Cont)
Dwg. 1704B35
^x^ Duration
Sample ^\
4C - 7 days
4C - 7 days
4C- 14 days
4C- 14 days
4C- 28 days
4C- 28 days
Leaching Conditions
Solid Form
Chunk
Powder
Chunk
Powder
Chunk
Powder
Shaking
No
Yes
NO
Yes
No
Yes
Solid/Water
10 g/100 ml/256 hr
aerobic
10 g/100 m 1/256 hr
aerobic
10 g/100 ml/256 hr
aerobic
10 g/100 m 1/256 hr
aerobic
10 g/100 m 1/256 hr
aerobic
10 g/100 m 1/256 hr
Leachate Characteristics, mg/1
PH
12.6
12.5
12 .3
12.4
12.4
12.4
Sp.Cond..
p mhos/cm
7970
8070
7770
8350
8320
8250
Ca
1328
1440
1208
1404
1328
1296
Mg
0
0
0
0
0
0
S
<0.1
<0.1
0
0
0
0
S°4
1680
1877
1584
1920
1512
1632
-------
without shaking for the same leaching time and its filtrate analyzed
for leachate qualities. Examination of the results summarized in
Table 22 reveals:
• Leaching for 256 hours using either one of the above methods
produced leachates of similar quality, indicating that the
solid compacts were permeable to water. The equilibrium
state was reached for both mixtures.
• All nine samples (of three mixtures and three curing times)
produced similar leachates, further indicating that a
leachate saturation had been reached.
• Sulfide was low in all the solid blends studied and was
undetectable in their leachates.
• All leachates were high in pH, calcium, sulfate, and IDS.
• Trace metal leachability is not expected to cause water
contamination.
It appears that the leachates produced from these solid com-
pacts are not as desirable as the leachates from either the sulfated
sorbents, which had lower pH, calcium, and TDS, or the dead-burned
stones, which had lower calcium and sulfate dissolution. It would be
premature, however, to judge the potential usefulness of this utilization
processing method based on the above results, which were obtained at the
initial developmental stage.
High-Temperature Compacting
CAFB residue can also be processed by isostatic pressing at
3 9 12
high temperature. ' ' Solid compacts of high-temperature processed
CaSO, and CAFB spent sorbents with fly ash were studied for their
permeability and leaching behavior. Table 23 summarizes the sample
preparation and resultant compositions as determined by X-ray diffraction.
Obviously, the solid reaction took place during hot pressing; the major
species present in 75-CF-26 and 75-CF-30 were Ca2Al2Si07 and CaAl?Si?0R,
which are the reaction products between the spent sorbent and fly ash.
64
-------
Table 23.
PREPARATION AND COMPOSITIONS OF HIGH-TEMPERATURE
PROCESSED SOLID COMPACTS
Samples
Sample Description
X-Ray
Identification
75-CF-22 80% CaS + 20% coal fly ash, ball-
milled for 2 hr, sieved to -120 mesh
and hot pressed at 1050°C, 33096 kPa
(4800 psi) for 1 hr
d = 2.550 g/cm3
Dark, hard, dense cylinder
Smells of H£S
75-CF-26 50% CaSO^ + 50% coal fly ash, pre-
pared under same conditions as above,
d = 2.350 g/cm^
Dark, hard dense cylinder
No smell
75-CF-30 20% CAFB-9 spent sorbent + 80% coal
ash, prepared under similar con-
ditions as above.
d = 2.460 g/cm3
Dark, hard, dense cylinder
No smell
Major CaS
Major Ca2Al2Si07
Minor CaAl0SiO,
sio22 6
Major Ca2Al2Si07
CaAl0Si00QFe
2. i. o
Minor CaAl0SiO,Si00
L D 2.
Preliminary testing indicated a very low permeability
—8
coefficient, in the order of 10 cm/s. Leachate characteristics are
presented in Table 24. A significant difference was found between the
leachates induced by the two procedures: static contact of water with
cylindrical samples versus shaking of crushed powder in water, with the
former resembling the more realistic landfill situation and the latter
representing the worst possible case. This result further indicates low
sample permeability. Of these three samples, the leachability of 75-CF-30
is of primary interest because it is made of CAFB spent sorbent. The
leachate of this sample is low in TDS, calcium, sulfate, and sulfide,
passing the DWS even when induced by the shake (crushed sample) method.
65
-------
Table 24
LEACHATE CHARACTERISTICS OF HIGH-TEMPERATURE SOLID
COMPACTS OF SORBENT/ASH MIXTURE
Sample
Sample
Conditions
Leaching
Procedure*
Solid/HaO
Ratio
Leach ing
Time, hr
Leac.hate Characteristics
PH
Sp. Cond. ,
pmhos-cm
Ca,
mg/ 1.
Mg,
mg/ i
mg/;
*Procedure A: Solid-water mixtures are agitated in Erlenmeyer flasks by an automatic shaker; mixtures are
filtered for leachate analysis.
*Procedure B: The cylindrical sample is mounted at the bottom of a glass tube with only the top surface
in contact with water. No agitation is applied. As the samples are practically impermeable,
leachates are poured out for analysis.
111S/ v'
75-CF-22
"
75-CF-26
11
75-CF-30
"
Crushed powder
Cylindrical sample
Crushed powder
Cylindrical sample
Crushed powder
Cylindrical sample
A
B
A
B
A
B
1:10
1:10
1 :10
1 : 10
1:10
1:10
210
210
210
210
210
210
11.35
9.96
8.02
9.63
8 . 35
9.28
14700
410
950
290
520
90
4964
64
108
•'10
72
<10
19
<10
0
<10
24
<10
1925
30
61
<20
34
< 5
6528
152
389
90
233
22
-------
In summary, the high-temperature processed solid compacts of
spent sorbent and fly ash are more stable on contact with water than are
the spent sorbent and fly ash separately, due to the formation of the
insoluble cementlike calcium-aluminate-silicate compounds. Leaching
results indicated satisfactory leachates with reduced pH, TDS, calcium,
sulfide, and sulfate concentration. Trace elements also pass DWS. The
potential application of this processing method, however, would also
depend on the results of economic analysis.
Slurry Carbonation
Slurry carbonation is a processing method whereby the spent
3
sorbent is carbonated with CO™ to form practicably insoluble CaCO_.
On the basis of the results obtained, few environmental problems are
expected:
Of the total spent sorbent, 96 to 97 percent can be
converted to practically insoluble and environmentally
stable CaCO~, whose leachate is expected not to cause
water contamination.
CaS in the spent sorbent is converted to H~S during the
slurry carbonation reaction; it is recycled to the gasifier
and sent to the S-recovery system. No or low sulfide in
the leachate is expected.
Since the heat of hydration of CaO is released during the
slurry carbonation reaction (which is utilized as a heat
source), disposal of the carbonated sorbent will not
cause heat pollution.
Leachability of trace metal elements is expected to be
similar to that of the unprocessed spent sorbent, which
has been shown not to be of environmental concern.
67
-------
Reference Material
TUGCO Ash
31
Characterization of the coal ash from TUGCO,"* and tests on
the environmental impact of land disposal were carried out. The objective
was to provide references to the leaching and activity properties of the
fly ash resulting from the CAFB process utilizing Texas lignite coal as
the solid fuel.
X-ray diffraction showed that the ash consisted of major Si02
(quartz) and minor AJ^Oo^ SiO™ (mullite) . Results by wet chemistry
analysis are shown in Table 25. Morphological investigation reveals
that the TUGCO ash is composed of cenospheres ranging from 0.1 to 40 pm
in size. Figure 18 shows typical SEM photomicrographs of the sample and
EDAX spectra of four cenospheres of different diameters. Note that
silicon and aluminum are the major elements present in all four sites
scanned and that the minor elements (calcium, potassium, iron, magnesium,
and titanium) vary among particles.
Table 25
ANALYSIS OF TUGCO ASH
Substance
s.o2
A12°3
CaO
MgO
so3
P
F
Cl
Others
Wt %
60.4
19.3
2.54
9.36
2.27
0.05
0.029
0.016
<0.001
6.03
68
-------
(a)
(b)
(c)
(d)
(e)
Figure 18 - Typical SEM and EDAX of TUGCO Ash; (a) and (b),
SEM; (c), (d), (e), and (f), EDAX Spectra
Scanned on Sites 1, 2, 3, and 4, Respectively
69
RM-73t.
-------
Leaching studies were carried out employing both the con-
tinuous and intermittent shake procedures. Table 26 summarizes the
results of the continuous shake test. Figure 19 shows the results of
the intermittent leaching test. Both tests resulted in relatively pure
leachates with lower pH, calcium, SO,, and TDS than the typical leachate
of spent sorbent or ash from the CAFB process. The higher pH, calcium,
SO,, and TDS from the spent CAFB solid are caused by the CaO, CaS, and
CaSO, present in the utilized sulfur removal sorbent. The trace metal
elements present in the TUGCO ash and its leachate are summarized in
Table 27. Two elements, chromium and selenium, are found to exceed the
drinking water standards.
No detectable heat-release activity was found when TUGCO ash
came into contact with water.
Valley Builder Supply Samples
Characterization of the samples obtained from Valley Builder
31
Supply has been completed and the environmental impact has been
investigated to provide a reference for the disposal of processed and
utilized CAFB residue. Table 28 lists the samples obtained and sum-
marizes the chemical compositions as determined by X-ray diffraction
and wet chemical methods. Figures 20a and b show typical optical and
SEM microphotographs of a piece broken from the Valley Builder block.
Figures 20c and d show, respectively, the porous area A and the less
porous area B identified on 20b. EDAX analysis shows the porous area A
is rich in silicon and aluminum, plus potassium, iron, and calcium in
decreasing order; and the less porous area B is rich in calcium, with
silicon, aluminum, potassium, and iron in decreasing concentrations.
Standard leaching tests were carried out on a piece of Valley
Builder block, both as it is and as crushed powder. Table 29 summarizes
the chemical characteristics of the block and its leachates and compares
the leachates with the DWS. The leachates exceed DWS for pH although
70
-------
Table 26
CHEMICAL CHARACTERISTICS OF LEACHATE FROM TUGCO ASH
BY CONTINUOUS SHAKE TEST
Leach Conditions
Leachate Characteristics, mg/£
PH
Spec. Cond.
(ymhos/cm)
Ca
Mg
50 g/500 ml, 200 hr 10.7 810 144 <10
10 g/100 ml, 400 hr 8.2 760 148 10
S
S°4
F
Cl
<10 263 <1 <1
1U ^ No
Br
»o2
t Determine
»o3
P04
TOC
<1
-------
Curve 692873-B
300
^ 200
^ 100
00 o
^ 300
I1 200
3 100
0
Normalized Leachate Quantity, mllq of Starting Material
6 12 18 24 30 36
•o——o
e
o
2.0
•i 1.0
o
CT>
°
600
400
200
n
1 1 1 1 1
V~
_
-— o 1 o— o— o— o— - d>
12
10
8
6
i i i i I
_ ^ v ^---a^^^ ^
° o
1 1
5 10
(360) (720)
Total No.of 72 hr Intermittent Leach (total leach time, hr)
Figure 19 - Leachate Characteristics of TUGCO Ash
72
-------
Table 27
TRACE METAL ELEMENTS IN TUGCO ASH AND ITS LEACHATE
Substance
Al
Ag
As
B
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
Hg
Mg
Mh
Mo
Na
Ni
Pb
Sb
Se
Si
Sn
Sr
Ti
V
Zn
Zr
TUGCO Ash Solid,
ppm
Major
< 1
12.1
500
5
< 10
Major
< 3
20
80
200
Major
0.12
> 1000
660
30
> 1000
50
85
< 33
4.0
Major
< 10
1000
< 1000
250
100
TUGCO Leachate,
ppm
> 1
< 0.01
0.006
> 1
< 0.01
< 0.01
Major
< 0.01
< 0.01
0.7a
< 1
< 0.1
< 0.001
< 1
< 0.01
0.2
% 1
< 0.05
< 0.01
< 0.05
0.05a
< 1
o n c
^ \j • O_;
> i
< i
0.5
< 1
< 1
Exceed the U.S. Drinking Water Standards for Cr (0.05 ppm)
and Se (0.01 ppm).
-------
Table 28
CHEMICAL COMPOSITIONS OF VALLEY BUILDER SUPPLY SAMPLES
Samples
X-Ray Diffraction
Wet Chemistry
Ca
Limestone Dust 37.28
Type I Cement (Major) 54 CaO • 16 SiO~ • MgO • A190~ 43.68
Mg
1.0
2.4
so4
0.02
3.4
, wt %
S=
0.03
0.04
co3=
58.39
0.82
Fine Aggregate
Coarse Aggregate
Block
and/or Ca^SiOo and others in trace
amounts (Si02, CaC03, Ca(OH)2, CaSO^,
CaSO^ • 2H20, Ca3Mg(Si04)2, CaO, and
(Mg, Fe)2Si04)
Major SiO~ quartz and an unidentified
trace phase
Major SiO? quartz, trace CaCO,, calcite
0.96 0.19 0.22 0.1 0.71
0.8 0.19 0.83 0.08 0.52
8.0 0.19 0.21 0.05 7.55
-------
V
;«n
(a)
Figure 20 - Valley Builder Supply Block: (a) Optical photomicrograph
at 3X; (b) SEM at 26X; (c) porous area A at 1300X, rich
in Si, Al, plus K, Fe and Ca in decreasing concentrations
shown by EDAX; (d) less porous area B at 1300X, rich in
Ca, also Si, Al, K, Fe in decreasing concentrations.
75
RM-75208
-------
Table 29
Dwg. 1694B42
CHEMICAL CHARACTERISTICS OF VALLEY BUILDER SUPPLY BLOCK AND LEACHATE
Substance
Ag
Al
As
B
Ba
Be
Bi
Ca
Cd
Cr
Cu
Fe
Hq
Mg
Mn
Mo
Ni
Pb
Sb
Se
Si
Sn
Sr
Ti
V
Zn
Zn
Cl
F
S =
S04
TOC
pH
Sp. Cond.
li mhos/cm
Solid ,ppm
<1
Major
350
500
2
1
8.0%
<1
20
30
>1%
0.19%
100
20
20
10
<10
Major
<3
>300
>1000
150
100
500
0.05%
0.21%
Leach ate. ppm
a
<0.01
<1
<0.01
<1
<1
<0.01
<0.01
52
<0.01
0.02
<1
<0.2
< 0.002
<10
<0.01
<0.05
<0.05
<0.01
<0.2
<0.01
<0.01
<0.2
<1
<0.2
0.05
<1
<1
2.6
<1
<10
35
<5
'/MV,
270
b
<0.01
<1
<0.01
<1
<1
<0.01
<0.01
114
<0.01
0.04
<1
<0.2
< 0.002
<10
<0.01
<0.05
<0.05
<0.01
<0.2
<0.01
<0.01
<0.2
<1
<0.2
0.2
<1
<1
4.2
<1
<10
194
<5
'/#.&/,
420
•Drinking Water Standards,
ppm
0.05
0.05
1.0
200
0.01
0.05
1.0
0.3
0.002
150
0.05
2.0
0.05
0.01
0.01
1.0
5.0
5.0
250
2.4
250
5.0 to 9.0
-750
"DWS NIPDWR, USPHS. and WHO Drinking Water Standards
a leachate from a piece of uncrushed block
b leachate from crushed powder
tm exceeds the DWS
76
-------
much less than does the CAFB leachate. One may recall that a typical
CAFB leachate (processed and unprocessed) exceeds the DWS for pH,
calcium, S04, and IDS.
Results from the heat-release tests are summarized in Table 30.
The limestone dust and fine and coarse aggregates did not show any
temperature rise; the cement powder gave off heat on contact with
water as expected. The block (after being crushed to powder), however,
also showed a very slow temperature rise when exposed to water.
Table 30
HEAT-RELEASE PROPERTIES OF VALLEY BUILDER
SUPPLY SAMPLES
Samples 3
Limestone Dust <0.2°
Type
Fine
Heat-Release, AT, °C
g/20 ml 16 g/4 ml
C <0.2°C
I Cement 2°C 6°C in < 1.5 min
(immediate rise)
Aggregate <0.2°
Coarse Aggregate <0.2°
Block
Block
C <0.2°C
C <0.2°C
<0.2°C <0.2°C
(crushed powder) <0.2°C 2°C slow rise over
1.5 hr
FGD Sludge
In the absence of leachate criteria with which to assess the
environmental acceptability of land disposal of CAFB residue, the
leaching property of residues from conventional coal-burning power plants
with flue gas desulfurization scrubber systems has been investigated to
provide a reference for the leachate characteristics of residue from a
currently commercialized process.
77
-------
A typical untreated FGD sludge using lime or limestone sor-
bent contains 30 to 70 percent solid matter after settling. The major
constituents of the solid are CaSO -1/2 H20, CaSO^-2 Kfl, CaCCy coal
ash that consists of SiO,,, Al 0 , Fe2°3' and trace elements. The exact
composition varies, depending on many factors, including the type of
coal, the type of scrubber system, and boiler and scrubber operating
conditions.
Six samples of FGD sludge from pilot- and commercial-scale S02
scrubbing systems, including untreated, ponded, oxidized, and stabilized
lime or limestone scrubber sludges, were tested during the investigation.
Table 31 summarizes the sample source, scrubber system, further treatment,
and X-ray identification of the sludges. All sludge samples except one
(the stabilized) were wet with supernatant liquors as received. The
liquors were separated by vacuum filtration and analyzed chemically.
The dewatered sludges were then dried (^95 to 105°C), and the sludge
powders underwent the standard leaching tests developed for CAFB
residues.
SEM of the unprocessed sludge (Figure 21) shows the small
platelet crystallites of CaSO -1/2 H~0 that have been reported by the
39-41
FGD investigators to be responsible for the dewatering/settling
difficulties and the thixotropic property of the sludge. The ponded sludge
often has mixtures of the flaky platelets and bulkier crystals due to
partial oxidation of sulfite to sulfate. On the other hand, the oxidized
TVA sludge shows large crystals of gypsum (CaSO,-2 tUO). The potential
environmental hazard (due to sulfite oxygen demand) has been reduced, and
dewatering and settling difficulties are greatly improved. In fact,
oxidation to gypsum has been recommended as one of the methods by which
46
Lo stabilize FGD sludge. Cenospheres from coal ash are also present
in the sludge samples and may also cause settling problems in ponding.
EDAX spect-ra show that the platelet crystallites of the FGD solid are
high in calcium and sulfur (presumably CaSO,,'1/2 H~0) and that the
cenospheres are rich in silicon, aluminum, and iron (coal ash).
78
-------
Table 31
SUMMARY OF FGD SLUDGE SAMPLES
Sample
Process Description
X-Ray Identification
Louisville Gas and Electric
Company (LGE)42
Fresh, untreated, unponded;
lime sludge with small amount
of MgO added
Major: CaS03'l/2 H20
Low minor: (Fe,Mg) A1204 or
(Mg,Fe) Si04 spinel
Columbus Southern Ohio Company
(CSO)43
Untreated lime sludge; 98% fly
ash removal
Major:
CaS03'l/2
Duquesne Light Company
Untreated lime sludge; con-
taining ^50% fly ash
Major:
Minor:
Low minor:
Si02
CaS03'l/2
Fe2°3
TVA Shawnee, Pond
Untreated, ponded limestone
sludge bottled in pond liquor
for 2.5 yr
Major:
Major:
Trace:
CaS03'l/2
CaCO
SiO,,
TVA Shawnee - Oxidized
Sludge44.45
Lime sludge followed by
forced air oxidation to gypsum
Major:
Duquesne Light Company43
Stabilized Sludge
"Calcilox" stabilized lime
sludge containing ^50% fly ash;
stabilized and ponded for 3 yr
Major:
Minor:
SiO^, amorphous
phase
CaCO , CaSO '1/2
-------
SEM Photomicrographs of Itewatered FGD Sludge
(a)
FGD sludge (LGE)
unponded, untreated
(b)
FGD sludge (TVA)
ponded, untreated
(c)
FGD sludge (TVA)
oxidized, gypsum
Figure 21 - SEM Photomicrographs of Dewatered FGD Sludge
80
RM-
73896
-------
SEM of the stabilized sludge shows a mixture of cenospheres
and a fluffy mass that appears frequently to be clustered and to have
adhered to the cenospheres. The platelet crystallites are no longer
observed. It has been reported that the compressive strength of the
stabilized sludge increases as a function of stabilization (solid setting)
time.
Leaching properties were investigated using both the con-
tinuous and the intermittent shake methods described in the previous
section. Figure 22 shows the leachate characteristics of the dried
sludge as a function of continuing leaching time. Note that the
leachate from the stabilized FGD sludge is very similar to gypsum
leachate. On the average the untreated sludge leachate has higher
calcium, magnesium, SO,, pH, and TDS.
Figure 23 shows the specific onductance and approximate TDS
in the leachate from the intermittent shake test. The better leachate
quality is seen again in the case of the stabilized sludge. The
leachate from the untreated, ponded, and oxidized sludge had much higher
TDS and improved with total leaching time and total leachate volume.
The lower TDS in the CSO leachate after two 72-hr leach cycles was due
to the low solubility of calcium sulfite (CaSO«), which was the predom-
inant specimen in the untreated fly-ash-free CSO sludge. It must be
kept in mind that the leachate characteristics presented here were from
the vacuum-filtered and dried sludge. The superheated liquors of the
sludges had much higher TDS and specific ion concentrations, as seen
in Table 32, which summarizes the chemical characteristics of the solid,
liquor, and leachate of the untreated, ponded, oxidized, and stabilized
sludge samples. One can see that the trace element concentrations are
Lue lowest Lot Liie leachate from the stabilized sludge auu ue^L luwcoL
in the untreated sludge following ponding. Although oxidation to gypsum
increased the crystal size and improved the sludge settling property and
shear stress, the trace element and anion concentrations in the
oxidized sludge liquor and leachate remained high.
81
-------
Curve 693172-B
2000
1000
to
o
200
100
0
3000
2000
1000
0
"
til;
"• I?,
0
100 200 300 1 400
Total Continuous Leach Time, hr
A LGE Untreated
v CSO Untreated
o DLC Untreated
O TVA Ponded
o TVA Oxidized
• Calcitox-Stabilized
Natural Gypsum
Figure 22 - Leachate Characteristics of Dried FGD Sludge
as a Function of Continuous Leach Time
82
-------
Curve 695695-B
Normalized Leachate Quantity, m£/g Starting Solid
6 9 12 15 18 21 24
27
30
00
E
o
t/>
o
.c
E
o
c
ra
J
4000
3000
2000
1000
CT>
I
I
I
I
I
345678
n = Total No. of 72-hr Intermittent Leach
10
130 360
Total Leach Time = 72 x (n), hr
LGE Untreated o DLC Untreated
CSO Untreated O TVA Ponded
Natural Gypsum
540
o TVA Oxidized
• Calcilox-Stabilized
720
Figure 23 - Leachate Characteristics of Dried FGD Sludge as a
Function of Intermittent Leaching
-------
Table 32
•«• MIK36
CHEMICAL CHARACTERISTICS OF FGD SLUDGE, LIQUOR, AND LEACHATE*
a Based on analysis of 6 samples tested
Exceed Drinking Water Standards I NIPDWR. USPHS. and WHO)
84
-------
The investigation of FGD residues presented in this section
has been limited to their chemical and leaching properties. The
physical properties of the FGD sludge have been reported in the
45-47
literature.
Gypsum
Granular gypsum (Iowa No. 114) was tested in parallel with
many of the CAFB leaching tests to provide a reference for natural
leachability. Results have been reported in the previous sections.
Heat Release Property
The activity of residual lime in spent sorbents and fly ash
was determined by its heat release property on contact with water, as
O£
the hydration reaction of CaO is extremely exothermic. Literature on
37
lime reactivity and slaking rate has been reviewed. The ASTMC110-76
provides a test for the slaking rate of quicklime (CaO). In this test
76 g of quicklime is added to 380 ml of distilled water in a modified
Dewar flask covered with a rubber gasket fitted with a mechanical
stirrer. The temperature is read with a thermometer at 30-second to
5-minute intervals, depending on the reactivity of the quicklime, until
a constant temperature is reached. The slaking rate is determined by
the following quantities: temperature rise at 30 seconds, total
temperature rise, and active slaking time.
38
Murray studied lime reactivity as a function of porosity
and shrinkage characteristics during calcination and found that
calcitic quicklime of low shrinkage and high porosity had high reactivity.
He used a limerwater ratio of 1:7 by weight. Since preliminary slaking
tests indicated a wide range in slaking rates, an empirical compromise
poiuL was selected as indicative of the rapidity of slaking. Tue
temperature rise in five seconds was selected, and the reactivity
coefficient was designated as AT,.; yet he readily acknowledges that
85
-------
his test was inequitable for the extremely reactive limes in which slaking
was actually completed in three to four seconds, so that a reading at
five seconds made them appear to be slower than they actually were.
American Water Works' standard on lime for water treatment
employs a lime slaking test with lime:water proportions 100 g:400 ml,
following the test procedure of ASTMC110.
The temperature rise of a solid/water system containing free
CaO is a function of solid:water ratio. In our experimental effort to
establish a screening test for the residual activity in spent CAFB
solids produced under varying processing conditions, a solid to water
proportion of 3 g to 20 ml (which is in the bulk range specified by the
ASTMC110 test and by Murray's work) was found empirically to provide
much better repeatability than that from a higher solid:water ratio which
would give greater temperature rise but would lack reproducibility, most
likely because of local heating. The former ratio was initially adopted
as the screening test for heat-release property because of its speed,
small quantity of stone required, and the good reproducibility of results.
The latter, however (small quantity of water added to larger quantity
of solid), was also used because it provides higher sensitivity and
simulates rainfall onto the disposed solid.
Figure 24 compares the temperature rise as a function of
solidrwater ratio for a CAFB spent sorbent and a calcined limestone.
Higher temperature rise and faster response are observed for the higher
solid:water ratio system, as expected. Figure 25 shows the temperature
rise profile when 4 ml of water are added to 16 g of six CAFB spent
materials. A lower solidrwater ratio is used for the calcined limestone
for comparison due to the calcined limestone's extremely violent heat
release characteristics. A variation in residue activity among different
batches of CAFB spent sorbent was noted. Spent bed material also
displays greater heat release property than did fly ash or stack fines.
86
-------
Curve 690480-A
Calcined Limestone, 15 g/20 ml
Calcined Limestone, 5g/20 ml
CAFB-8 Reg. Bed, 16 g/4 ml
CAFB-8 Reg. Bed, 3 g/20 ml
J_
10
20
Time, min
30
Figure 24 - Heat-Release Property as a Function of
So lid-.Water Ratio
The heat release properties of all the CAFB residues, processed and
unprocessed, using the lower solid:water ratio (3 g:20 ml) are summarized
in Table 33. Note the improvement by processing.
Total Dissolved Solids
The total dissolved solid (IDS) in a leachate is a good index
of leachate quality. TDS, which can be determined by the time-consuming
evaporating procedure, can be estimated by multiplying the easily
measured specific conductance by an empirical factor. This factor may
87
-------
Table 33
ACTIVITY TESTS OF PROCESSED AND UNPROCESSED CAFB SPENT
SORBENTS BY THEIR HEAT-RELEASE PROPERTIES
Samples
CAFB - 7 Reg; Bed
CAFB - 8 Reg. Bed
CAFB - 8 Gasif. Bed
CAFB - 8 Stack Fines
CAFB - 9 Reg. Bed
CAFB - 10 A Gasif. Bed
CAFB - 11 Reg. Bed
CAFB -11 Gasif. Bed
CAFB - 11 Main Cyclone
CAFB - 11 Stack Fines
DS - Mix
CAFB -903
CAFB - 904 Composite
CAFB -904 125 -177pm
DB163
DB164
DB165
DB166
DB167
DB168
DB169
DB170
DB171
Processing History
Unprocessed CAFB residue from ERCA
M
n
M
M
n
n
n
n
ii
76 m* sulfated CAFB - 7
50 m* sulfated CAFB - 9
79 m% sulfated CAFB - 9
CAFB -904 sieved to -f 125- 177Mm. 94 m%
Dead-burned CAFB -9. 1070°C. 2hr
Dead-burned CAFB -9, 1070°C. 5hr
Dead-burned CAFB- 9, 1070°C. 24 hr
Dead-burned CAFB- 9. 1250°C. 2hr
Dead-burned CAFB -9. 1250°C. 5hr
Dead-burned CAFB -9. 1250°C. 24 hr
Dead-burned CAFB -9. 1550°C. 2hr
Dead-burned CAFB -9. 1550°C. 5hr
Dead-burned CAFB -9. 1550°C. 24 hr
Solid/Water
3g/20ml
II
II
n
II
II
M
n
II
II
II
II
tl
II
ti
II
II
H
II
II
M
II
11
ATmax.°C -
18
10.3
6.7
3.1
15
2
18
20
1.3
<0.2
<0.2
0.7
<0.2
<0.2
17
19
0.9
7.2
<0.2
<0.2
<0.2
<0.2
<0.2
88
-------
Table 33 (Continued)
Dwg.1704B55
Samples
D8. 0-44um
DB, 0-44um
DB, 0-44um
DB. 0-44Mm
DB, 0-44um
DB. 0-44um
DB. 63-88um
DB, 63-88um
DB. 63-88um
DB, 63-88um
DB. 63-88um
DB, 63-88um
Room-Temp. Compacts
4A - 7. 14. 28
4B - 7, 14. 28
4C - 7. 14. 28
75 - CF - 22
75 - CF - 26
75-CF-30
TUGCO Ash
Valley Builder
FGD Sludge
Gypsum
Limestone 1359
500-lOOOum
Calcined Limestone 1359
500-lOOOum
Tymochtee Dolomite
1000-1200um
Processing History
Dead-burned CAFB -9. 1250°C. 2hr
Dead-burnedCAFB-9. 1250°C. 5hr
Dead-burnedCAFB-9. 1250°C. 24hr
Dead-burnedCAFB-9. 1250°C, 2hr
Dead-burnedCAFB-9. 1550°C. 5hr
Dead-burnedCAFB-9, 1550°C. 24 hr
Dead-burnedCAFB-9. 1250°C. 2hr
Dead-burnedCAFB-9. 1250°C.5hr
Dead-burnedCAFB-9. 1250°C, 24 hr
Dead-burned CAFB- 9. 1550°C. 2hr
Dead-burnedCAFB-9. 1550°C. 5 hr
Dead-burned CAFB -9. 1550°C. 24 hr
Room-temp, processed sorbent/ash mixtures
for 7, 14. and 28 days
M II
II II
High-temperature hot-pressed CaS/ash compacts
High-temperature hot-pressed CaSO./ash
compacts
High-temperature hot-pressed CAFB-sorbent/ash
compacts
Conventional lignite ash
Commercial aggregate
Untreated and treated
Natural, ground
Solid/Water
3g/20ml
M
ll
M
M
11
11
H
M
II
II
11
M
M
II
tl
M
II
II
II
II
ir
it
M
M
*v°c
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
'0,2
<0,2
<0.2
<0.2
<0,2
<0.2
<002
<0.2
> 55
<0.2
89
-------
Curve
vo
O
E
o>
Calcined Limestone, 15 g/20 ml
CAFB-8Reg. Bed, 16 g/4 ml
-— CAFB-8Gasif. Bed, 16 g/4 ml
CAFB-10A Gasif. Bed, 16 g/4 ml
RS-CAFB-10A Gasif. Bed, 16 g/4 ml
CAFB-8 Stack Fines, 16 g/4 ml
RS-CAFB-10 Gasif. Fly Ash. 16 g/4 ml
10
20
30
40
Time, min
50
60
70
80
Figure 25 - Heat-Release Property of Spent Solids from the CAFB Process
-------
vary, depending on the soluble components in the particular aqueous
system and the temperature of measurement. A constant temperature, 25°C,
has been selected for the latter throughout our leaching studies. This
section summarizes our efforts in determining empirically the multiplying
factor for the CAFB leachates.
Several spent CAFB materials (bed, ash, stack fines) were
investigated. Leachate was induced by a 48-hr shake procedure. A
portion of the original leachate from each sample was diluted to provide
diluted solutions of 1/2, 1/4, and 1/8 fractions of the original con-
centrations. Specific conductance, pH, and IDS were determined for all
16 leachate solutions.
The procedure in determining TDS described in Standard Method
for Water and Wastewater was used to obtain TDS at evaporation tempera-
ture, 103°C. This was not the true TDS because the residue at 103°C
contained physically occluded water, hydration and carbonation products,
Ca(OH)2, CaSO,-1/2 H20, CaSO,-2 H20, and CaCO., among other dissolved
species. To determine the true TDS - in other words, the total weight
of solid from the spent CAFB material that is dissolved - the residue at
103°C was heated to 500°C to convert Ca(OH)2, CaSO^-1/2 H20, and
CaSO,, and then to 900°C to convert CaCO., to CaO. As we will show that
the TOC in the leachate of CAFB residue is low, volatilization and
decomposition of organic species would not be of concern when residue
is dried at higher temperatures. The TDS at 900°C was used in this work
because it approximated more closely the weight of the actual solid com-
ponents - for example, CaO and CaSO, dissolved from the spent CAFB materials,
The results presented in Figure 26 show the relationship
between TDS and specific conductance. There is a straight line with a
slope of 0.37 mg-cm-ymho~ fc~ . Thus, TDS in a CAFB leachate (mg/Jl) can
be approximated by multiplying the easily measured specific conductance
(in pmhos/cm) with a conversion factor of 0.37.
91
-------
Curve 691639-H
4000
3000
_
3
5 2000
1000
Slope =0.37 mg-cm-iimho- I
Sample 1: CAFB-10 Gasif Bed •
Sample 2: RS-CAFG-10 Gasif Fly Ash o
Sample 3: CAFB-8 Stack Fines Q
Sample 4: CAFB-8 Reg Bed a
J L
0 1 2 3 4 5 6 7 8 9 10 11 12
Specific Conductance, mi Hi mhos/cm
Figure 26 - Correlation between TDS and Specific
Conductance in CAFB Leachate System
Note that the results presented here are empirical and based
on typical CAFB leachates. TDS obtained in this manner are only approxi-
mated values. Note, also, that a typical CAFB leachate has a TDS of
approximately 4000 mg/£ and that the drinking water standard for TDS is
500 mg/Jl.
Total Organic Carbon (TOC)
Conventionally, chemical oxygen demand (COD) and biochemical
oxygen demand (BOD) are determined on water and waste water streams to
provide a measure of the organic content in the stream, but since both
the COD and BOD are time-consuming procedures, total organic carbon (TOC)
is often measured to provide a speedy and convenient way of estimating
the degree of organic contamination.
We used a Model 915 Beckman TOC analyzer. Measurements of
TOC on the CAFB residues indicated that the organic content in leachates
of CAFB residue was insignificant when compared with gypsum leachate
as a control.
92
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Leaching Media
In the previous sections deionized water was based in the
majority of the leaching tests except where otherwise specified. Leach-
ing property of the CAFB residue was also investigated as a function
of leaching media. Three media of varying pH were used. Leaching with
CCL-saturated deionized water was carried out to simulate surface
water where dissolved C0~ may be high. Leaching tests were also con-
ducted using a sodium acetate/acetic acid buffer solution with a
pH = 4.4 and specific conductance 3.31 umhos/cm, as suggested by
32
the proposed ASTM test to simulate inhomogeneous disposal sites where
codisposal of municipal and industrial waste often results in
acidic leaching conditions. Table 34 summarizes the continuous leaching
results of CAFB-10A gasifier bed material using three media under
aerobic and anaerobic conditions. Definitive conclusions cannot be
drawn on the basis of such limited data, but preliminary results do
indicate the following:
• Specific conductance and pH were decreased slightly with
C0~-saturated media because of the formation of insoluble
CaCO .
• The effect of an acetate medium on leachate concentrations
was more than additive, perhaps due to the higher ionic
strength and lower pH of the leaching medium. Increased
calcium and sulfide in the acetate leachate were such
examples.
• Anaerobic leachate had higher sulfide in all cases.
• On the whole the leaching medium did not play as important
a role as one might have expected, due to the large amount
ol spent CaO present in the CAFB residue.
• The final leachates were still highly alkaline in all
cases (pH ^12).
Minor and trace species were determined in these leachates.
Preliminary results, based on single-test data, suggested a slight
93
-------
Table 34
CHEMICAL CHARACTERISTICS OF CAFB-10A LEACHATE USING DIFFERENT ELUEHT
Eluent
Deionized Water
}eionized Water
Deionized Water
Deionized Water
CO^-Saturated
Deionized H.,0
(^-Saturated
Deionized H20
COj-Saturated
Deionized H~0
CC^-Saturated
Deionized H20
Acetate Buffer
SC = 3.1 millimhos/ciT.
Acetate Buffer
SC = 3.1 millimhos/cr
Acetate Buffer
SC = 3.1 mi llimhos/cn
Acetate Buffer
SC = 3.1 mi 1 limhos/rm
Eltient
pH
7.0
7.0
7.0
7.0
4.0
4.0
4.0
4,0
4.4
4.4
4.4
4.4
Solid sS
./Eluent
s Ratio
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
Continuous
Shake
Time
hr
100
100
196
196
200
200
400
400
200
200
400
400
Aerobic ^^
*S"^ Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Leachate Chem. Characteristics
PH
12.2
12.2
12.3
12.3
11,9
11.9
12.0
12.0
12.1
12.0
12.2
12.1
Sp. Conductance
(millimhos/cra)
11.13
11.23
11.74
3.62
9.59
9.57
9.73
9.70
14.5
14.9
14. S
19.2
Ca,
mg/i
1703
1768
1572
1472
1520
1568
1600
1572
3276
3280
3400
4SGO
S ,
rag/t
-
150
91
374
255
369
344
552
329
397
363
656
S04,
mg/'
1263
1311
1395
1139
1225
1083
1460
1325
913
1248
1060
340
-------
increase in lead, selenium, mercury, and chlorine. Because of sample
inhomogeneity and variations among CAFB residues from different run
conditions, tests on more samples must be repeated.
SUMMARY
The leachate characteristics of unprocessed and processed CAFB
spent sorbent are summarized in Figure 27 and compared with natural
gypsum leachate. Note the improvement of leachate quality by various
processing alternatives. This investigation, in general, resulted in
the following findings:
• Trace elements are not expected to cause environmental
problems (unprocessed and processed).
• Negligible organic contamination was found in the leachate
(unprocessed and processed).
• Leaching and heat release are improved significantly by
processing the stone.
• The leachate quality of processed spent sorbent has been
shown to be equal to or better than natural p,ypsum
leachate.
• Potential concerns are for
Unprocessed: sulfide, heat-release, Ca, SO,, IDS, and pH
Processed: Ca, SO,, TDS, and pH.
The effect of the leaching medium on leaching property should
be investigated further. Although TOC is low in leachates, specific
organic species have not been determined.
Because we lack specific disposal criteria, the leachate
characteristics of the CAFB residue are compared with liquor and leachate
of FGD residue, a currently commercialized process (Table 35). The
untreated sludge has liquor and leachate exceeding many of the DWS for
trace elements. With very few exceptions (two batches of stack fines),
the leachate of the CAFB residues meet the stringent DWS.
95
-------
Curve 686168-B
1500
^
i1 1000
s 500
^ 2000
* 1500
| 1000
^ 500
ITJ
O
2000
1500
1000
500
12
10
g
k
2.
-
1 1 1 1
• " ~
—
8^ —
1 1 1 1
c
42
o
£ O
O r—
.
00
10000
8000
6000
4000
2000
_ 1 ' ' 1 _
^1 o
^ — ^^ "~ ^
~^/ * *
A ^
1 IP 1 1
100 200 300
Mixing Time, hr
400
500
Lectcliate Characteristics as a FuucLiuu
of Mixing Time for:
O CAFB-9, unprocessed
A CAFB-904, 94 m% dry-sulfated
• Dead-burned at 1550°C, 5 hr
V Room-temp, processed compacts
0 75-CF-30, hi-temp. processed compact
D Natural gypsum
96
-------
Table 35
Dwg. 1693872
COMPARISON OF LEACHATE CHARACTERISTICS FROM THE
CAFB AND FGD RESIDUES*
Substance
Al
Ag
As
B
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
Hq
Mq
Mn
Mo
Na
Ni
Pb
Sb
Se
Si
Sn
Sr
Ti
V
Zn
Zr
S =
S03
soa
Cl
f
NO^as N
TOC
PH
IDS
Specific
Conductance
umhos/cm
Liquor, mqlt
FGD
Oto20
<0.05
<0.05
>5
<1
<0.02
<0.04
/V500///X
/OtoO,2'//x
<0. 1
<0.05
<1
<0.3
< 0.002
/OtoXlOOOV/
/J0to20////
0. 1 to 7. 0
0 to > 100
<1
<0.05
<0.2
/.o.'oQito'o.'5'/
Oto30
<1.0
Oto40
<2
<2
<2
<2
<20
<10to40
/"lOOOtpTpOO/
/300.to.6000 /
/ 10 to ISO'//
/OtQ,109///
<30
6to9
/5QOO,toM4pOO/
5.0 to 17.0
Leachate. mg/£
CAFB
<1
<0.05
<0.05
^2
<1.0
500
T^
a'^o:o3-^/;
<20
<0.05
<1
<10
10
<2
<1
<1
<1
/ojd.xiooo^
<10
/J00p--20(r/
<30
ra;<2;4fgr.8^
<10
<30
/12'to'l3//
/3000;to,4000
6.0 to 10.0
FGD
<1
<0.05
/O.td.O.'!//
>1
<1
<0.02
<0.04
A5QQ"//
<0.01
<0.1
<0.05
<0. 1
<0.3
< 0.002
/t).to 500//
/fito0.1/y
<1
<10
<0. 1
<0.05
-------
4. ENVIRONMENTAL ASSESSMENT
Based on the laboratory testing results, we judged that the
unprocessed CAFB spent sorbent would not be environmentally acceptable
for direct land disposal. Available test data, however, show that en-
vironmental acceptability can be achieved by further processing. Table
36 summarizes the degree of reduction of the environmental impact
achieved by four of the processing alternatives for the spent sorbent
from the CAFB gasification process. The leaching tests performed are
considered to result in more severe projections of environmental impact
than will be encountered in practice. Since there are no guidelines for
leachate qualities at the present time, results are compared with drinking
water standards and leachate characteristics of natural gypsum.
It must be pointed out that the drinking water standards are
used in this investigation only in an effort to put data into perspective
in the absence of EPA guidelines and should not be construed as suggesting
that the leachate must necessarily meet drinking water standards. Of
course, these standards are extremely conservative; a leachate dilution/
attenuation factor of 10 is currently being considered in the regulation
draft unaer Section 3001 of the RCRA by the Hazardous Waste Management
Division of the Office of Solid Waste, EPA.17
Although, on the basis of its leachate quality (Table 36), the
high-temperature processed compact appears to be environmentally
superior to other alternatives, the energy requirements would have to be
evaluated in relation to the benefits. On the basis of environmental
impact, dry-sulfation would be the recommended process, followed by dead-
burning and low-temperature fly ash blending.
98
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Table 36
g. 1694B48
COMPARISON OF ENVIRONMENTAL IMPACT OF PROCESSED AND
UNPROCESSED CAFB SPENT SORBENTS
Environmental
.Parameters
Processing
pH
Total
Dissolved
Solids
Sulfide
Sulfate
Calcium
Trace
Metal
Heat
Release
3g/20ml
Total °
Organic
Carbon
Unprocessed CAFB
ys
= 18°C
Xxxxx>
Ory-Sulfation
AT=ND<0.2°C
Dead-Burning
AT=ND<0.2°C
Rm-temp.Processing
AT=ND<0.2°C
HRemp. Processing
AT=ND<0.2°C
Note: u Unprocessed CAFB leachate characteristics
+ Improved from u value
0 No significant change from u value
^ Do not meet either the drinking water or gypsum leachate criteria
^ Pass gypsum leachate criteria but not Drinking Water Standards
Q Pass both drinking water and gypsum leachate criteria
a No Drinking Water Standards exist
-------
The major environmental concerns for direct disposal are heat
release, sulfide, pH, calcium, SO^, and IDS. The major environmental
conerns for disposal after processing are pH, calcium, SO,, and IDS.
On the basis of these results, spent sorbent processing will be required.
There are advantages and disadvantages to each method of processing,
but the ultimate decision will be based on the careful balance of tech-
nical achievement and economic feasibility. Of course, site selection,
design, and management of the disposal task based on the site-specific
hydrology, geology, climate, and soil composition are critically
important to the success of a solid waste disposal system. Selection of
a proper processing method to reduce the residue surface area and
permeability and to improve the heat-release and leaching properties
can greatly simplify the disposal management task.
In the absence of formal EPA criteria with which to assess the
environmental acceptability of the disposal of CAFB residues, the
chemical, physical, and leaching properties of the spent fluidized-bed
combustion (FBC) material are compared with those of the residues from
six FGD processes developed for conventional coal-burning power plants.
A preliminary comparison of the environmental impact of the disposal of
unprocessed CAFB solid wastes and untreated FGD sludge residues from
varying processing systems is presented in Table 36 on the basis of up-
to-date results from parallel environmental testing programs. Since
the samples tested resulted from our use of different coal and sorbents,
an absolute comparison may not be possible, although one would hope that
the general trends indicated were meaningful.
These results are encouraging and suggest that the disposal of
the CAFB solid waste may cause environmental effects comparable to (due
to its chemical properties) or perhaps less negative than (due to its
physical properties) the disposal of the residue from the currently
commercialized FGD process.
The assessment is based on the current results from an ongoing
program that is limited, however, by the lack of spent CAFB materials
from commercial systems. These conclusions are considered preliminary
and should be reassessed as more representative samples become available.
100
-------
Table 37
OHf. 2*15CM
PRELIMINARY COMPARISON OF THE ENVIRONMENTAL IMPACT
OF THE DISPOSAL OF CAFB AND FGD RESIDUES*
CAFB
(T) Solubility of major compounds: Ca. SO. . and IDS
contributing to potential environmental concern
(D Sulfidfc environmental concern
(5) High alkalinity in leachate: pH = 10 to 13
(4) Trace elements: not expected to cause
environmental problem. Most leachates meet
Drinking Water Standards
(5) TOC in leachate: tow
(T) Residual activity : Heat - release due
to hydration ot CaO
(2) Spent sorbent in dry granular solid form
• More disposal and utilization options available
• Relative ease in transporting and disposal
(3) Further processing is recommended due to
presence of CaS and CaO
FGD
(T) High concentrations of Mg, Cl in addition
to Ca. SOj and IDS (plus Na in the case
of double-alkali system )
(D Sulfite: environmental concern
(D pH = 5 to 10 for lime or limestone
scrubbing systems
pH = 12 to 13 for double-alkali system
(J) Several elements in liquor and leachate,
e.g. As. Se, Cd. Mn and F, exceeding the
Drinking Water Standards including the
ponded and oxidized sludges
(|) TOC in leachate: low
TOC in liquors: low
(T) No heat- release problem
(D In sludge form
• Difficulty in dewatering and settling
of untreated sludge causing problems
in tend disposal
• Potential environmental problems
associated with transporting, ponding,
and land reclamation
(D Physical stabilization chemical
fixation or oxidation to high solids
content gypsum most likely required
Chemical
Property
Physical
Property
^Unprocessed CAP) residue and untrsa:.ed FGD sludge
101
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5. REFERENCES
1. Archer, D. H., D. L. Keairns, J. R. Hamm, R. A. Newby, W.-C. Yang,
L. M. Handman, and L. Elikan, Evaluation of the Fluidized Bed
Combustion Process, Vols. I, II, and III. Report to EPA, Westing-
house Research and Development Center, Pittsburgh, PA, November 1971,
GAP Contract 70-9, NTIS PB 211-494, 212-916, and 213-152.
2. Keairns, D. L., D. H. Archer, R. A. Newby, E. P. O'Neill, E. J. Vidt,
Evaluation of the Fluidized-Bed Combustion Process, Vol. IV,
Fluidized-Bed Oil Gasification/Desulfurization. Report to EPA,
Westinghouse Research and Development Center, Pittsburgh, PA,
December 1973, EPA-650/2-73-048d, NTIS PB 233-101.
3. Keairns, D. L., R. A. Newby, E. J. Vidt, E. P. O'Neill, C. H.
Peterson, C. C. Sun, C. D. Buscaglia, and D. H. Archer, Fluidized
Bed Combustion Process Evaluation - Residual Oil Gasification/
Desulfurization Demonstration at Atmospheric Pressure. Report to
EPA, Westinghouse Research and Development Center, Pittsburgh, PA,
March 1975, EPA-650/2-75-027 a&b, NTIS PB 241-834 and PB 241-835.
4. Chemically Active Fluid Bed for SO Control: Volume 2, Processing
of Spent Sorbent, Westinghouse report to EPA, to be issued.
5. O'Neill, E. P., D. L. Keairns, and M. A. Alvin, Sorbent Selection
for the CAFB Residual Oil Gasification Demonstration Plant. Report
to EPA, Westinghouse Research and Development Center, Pittsburgh,
PA, March 1977, EPA-600/7-77-029, NTIS PB 266-827.
6. Bachovchin, D. M., P. R. Mulik, R. A. Newby, and D. L. Keairns,
Solids Transport between Adjacent CAFB Fluidized Beds. Report to
EPA, Westinghouse Research and Development Center, Pittsburgh, PA,
January 1979, EPA-600/7-79-021.
7. Chemically Active Fluid Bed for SO Control: Volume 1, Engineering
Evaluation and Sorbent Selection, Westinghouse report to EPA, to
be issued.
8. Resource Conservation and Recovery Act, Public Law 94-580; 1976.
9. Keairns, D. L., C. H. Peterson, and C. C. Sun, Disposition of Spent
Calcium-Based Sorbents Used for Sulfur Removal in Fossil Fuel
Gasification, Presented at the Solid Waste Management Session,
69th Annual Meeting, AIChE, November 28 - December 2, 1976,
Westinghouse Scientific Paper 76-9E3-FBGAS-P1.
102
-------
REFERENCES (Continued)
10. Craig, J. W. T., et al., Chemically Active Fluid Bed Process for
Sulfur Removal During Gasification of Heavy Fuel Oil - Second Phase.
Report to EPA, Esso Research Centre, Abingdon, UK, November 1974,
EPA-650/2-74-109, NTIS PB240-632/AS.
11. Chemically Active Fluid Bed Process (CAFB). Monthly report to
EPA, Foster Wheeler Energy Corporation, Livingston, N. J. May 29 -
June 25, 1978, Contract 68-02-2106.
12. Peterson, C. H., Processing of Spent Sorbent from the CAFB Process
for Disposal/Utilization. Report to EPA, Westinghouse Research
and Development Center, Pittsburgh, PA. To be issued.
13. Federal Register (42 CFR Part 466), 36 (159); August 17, 1971.
14. Federal Water Pollution Control At, Public Law 92-500; 1972.
15. Clean Water Act, Public Law 95-217; 1977.
16. Corson, A., D. Friedman, and D. Viviani, Hazardous Waste Management
Division, EPA-OSW, 1978.
17. "Hazardous Waste Guidelines and Regulations-Criteria, Identification,
and Listing of Hazardous Waste" EPA Draft, March 1978.
18. "Hazardous Waste: Proposed Guidelines and Regulations and Proposal
on Identification and Listing," Federal Register, December 18, 1978.
19. "Solid Waste Disposal Facilities - Proposed Classification Criteria,"
Federal Register, February 6, 1978.
20. "Land Disposal of Solid Waste Proposed Guidelines." Federal Register,
March 26, 1979. Part II.
21. Federal Register, 41 (29); February 11, 1976.
22. Environmental Protection Agency National Interim Primary Drinking
Water Regulations, Federal Register, 40 FR 59565; December 24, 1975;
Environmental Reporter 81; February 13, 1976.
23. U. S. Drinking Water Standards 1962, U. S. PUblic Health Service
Publications 956; 1962.
24. Interim Standards for Drinking Water, 3rd Edition, Geneva: World
Health Organization; 1971.
25. EPA Effluent Guidelines and Standards for Steam Electric Power
Generating, Federal Register, 40-FR 23987; June 4, 1975; Environ-
mental Reporter, S-259; July 11, 1975.
103
-------
REFERENCES (Continued)
26. Hangebrauck, R. P., Status of IERL-RTP Program to Develop Environ-
mental Assessment Methodology for Fossil Fuel Processes, working
document; February 1977.
27. Cleland, J. G., and G. L. Kingsbury, Multimedia Environmental Goals
for Environmental Assessment, Vol. I, November 1977, EPA-600/7-77-136a.
28. Schalir, L. M., and K. J. Wolfe, SAM/1A: A Rapid Screening Method
for Environmental Assessment of Fossil Energy Process Effluents.
Report to EPA, Acurex Corporation, Mountainview, CA; January 1978.
Aerotherm Report TR-77-50.
29. Weaver, D. E., C. J. Schmidt, and J. P. Woodyard, Data Base for
Standards/Regulations Development for Land Disposal of Flue Gas
Cleaning Sludges. Report to EPA, SCS Engineers, Long Beach, CA,
December 1977, EPA-600/7-77-118.
30. Water Quality Criteria, Ecological Research Series; March 1973.
31. Zoldak, F., and B. Halliday, Foster Wheeler Energy Corporation,
Private Communications, 1977-78.
32. Proposed Test Methods for Leaching of Waste Materials, ASTM D19-1203,
June 1978.
33. Sun, C. C., C. H. Peterson, and D. L. Keairns, Disposal of Solid
Residue from Fluidized-Bed Combustion: Engineering and Laboratory
Studies. Report to EPA, Westinghouse Research and Development
Center, Pittsburgh, PA, March 1978, EPA-600/7-78-049.
34. Sun, C. C., C. H. Peterson, and D. L. Keairns, Environmental Impact
of the Disposal of Processed and Unprocessed FBC Bed Material and
Carry-over, Proceedings of the Fifth International Conference on
Fluidized-Bed Combustion, Washington, D. C., December 12-14, 1977,
McLean, VA: The Mitre Corporation; 1978.
35. Friedman, D., and D. Viviani, EPA Office of Solid Waste-Hazardous
Waste Management Division. Private Communication; July 1978.
36. Boynton, B. S., Chemistry and Technology of Lime and Limestone.
New York: Interscience Publishers; 1966.
37. ^hysical Testing of Quick Lime, Hydrated Lime and Limestone, ASTM
C110-76. Annual Book of ASTM Standards, Part 13; 68-85; 1976.
38. Murray, J. B., et al., Shrinkages of High-Calcium Limestone during
burning, J. Am. Ceram. Soc., 37 (7): 323-28; 1974.
104
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REFERENCES (Continued)
39. Stone, R., and R. Kahle, Environmental Assessment of Solid Residues
from Fluidized-Bed Fuel Processing. Report to EPA, Ralph Stone
and Co., Inc., Los Angeles, CA, December 1977, EPA 600/7-77-139.
40. Keairns, D. L., et al. Fluidized-Bed Combustion: Environmental
and Engineering Investigations. Report to EPA, Westinghouse
Research and Development Center, Pittsburgh, PA. To be issued.
41. Werner, A. S., et al. Preliminary Environmental Assessment of
the CAFB. Report to EPA, GCA Corporation, Bedford, MA, October
1976, EPA-650/7-76-017.
42. Van'Ness, R. P., Louisville Gas and Electric Co., Private
Communication, 1977.
43. Henzel, D., Dravo Lime Co., Private Communication, March 1978.
1 -
44. i Leo, P. P., Aerospace Corporation, Private Communication, 1977.
i
45. Disposal of By-Products from Non-Regenerable Flue Gas Desulfurization
Systems. Second Progress Report to EPA, Aerospace Corporation,
May 1977, EPA-600/7-77-052.
46. Sludge Oxidation in Limestone FGD Scrubbers, EPA-IERL, Research
Triangle Park, NC, June 1977, NTIS PB 268-525.
47. Selmeczi, J. G., D. H. Marlin, and D. W. Kestner, Stabilization
of Sludge Slurries, Dravo Corporation, Pittsburgh, PA. U. S.
Patent 3,920,795, November 18, 1975.
48. Standard Methods for the Examination of Water and Waste Water,
13th Edition. Washington, D.C.: American Public Health
Association; 1974.
105
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
REPORT NO. .
EPA-600/7-79-158c
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Chemically Active Fluid Bed for SOx Control:
Volume 3. Sorbent Disposal
5. REPORT DATE
July 1979
6. PERFORMING ORGANIZATION CODE
i. AUTHOR(S)
C.C. Sun
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Westinghouse Research and Development Center
1310 Beulah Road
Pittsburgh, Pennsylvania 15235
10. PROGRAM ELEMENT NO.
EHB536
11. CONTRACT/GRANT NO.
68-02-2142
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
Final; 2/76 - 2/79
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES IERL-RTP project officer is Samuel L. Rakes, Mail Drop 61,
919/541-2825.
16. ABSTRACT The rep0rt describes a laboratory investigation of three areas of the
chemically active fluidized-bed (CAFB) process: residue characterization, leaching
property, and thermal activity. Results indicate that further processing is required
to meet environmental constraints. The environmental impact of CAFB residue dis-
posal is also compared with results of conventional residues (flue gas desulfurization
and lignite ash) from parallel tests. The impact of the recently enacted Resource
Conservation and Recovery Act is assessed. The CAFB process was developed to
convert high-sulfur heavy oils and low-grade coal to clean, medium heating value
fuel gas in conventional boilers. Disposal of the spent sorbent, which consists of
varying amounts of CaO, CaS, and CaSO4, may cause environmental concerns asso-
ciated with potential air, water, odor, and heat pollution. The spent sorbent can be
further processed to reduce its environmental impact by methods including dry sul-
fation, dead-burning, room-temperature fly-ash blending, high-temperature pro-
cessing, and slurry carbonation.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution Leaching
Fluidized Bed Processing
Coal Gasification Heat of Hydration
Fuel Oil Sorbents
Waste Disposal
Residues
b.IDENTIFIERS/OPEN ENDED TERMS
Pollution Control
Stationary Sources
CAFB
Thermal Activity
c. COSATI Field/Group
13 B 07 D
13H,07A
20M
2 ID 11G
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
119
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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