TVA
EPA
Tennessee Valley
Authority
Energy Research
Office of Power
Chattanooga TN 37401
TVA PRS 31
US Environmental Protection Agency Industrial Environmental Research
Office of Research and Development Laboratory
Research Triangle Park NC 2771 1
Characterization of
Solid Residues from
Fluidized-bed
Combustion Units
Interagency
Energy/Environment
R&D Program Report
EPA 600 7 78-135
July 1978
-------
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
-------
PRS-31
EPA-600/7-78-135
July 1978
Characterization of Solid Residues
from Fluidized-bed Combustion Units
James L. Crowe
Office of Power
Tennessee Valley Authority
Chattanooga, Tennessee 37401
by
and
Stephen K. Seale
Office of Agricultural and Chemical Development
Tennessee Valley Authority
Muscle Shoals, Alabama 35660
EPA Interagency Agreement No. IAG-D7-E721
Program Element No. EHE623A
Project Officers: D. Bruce Henschel (EPA) and James L. Crowe (TVA)
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
and
Tennessee Valley Authority
Office of Power
Chattanooga, TN 37401
-------
ABSTRACT
This report summarizes work completed during the period July 1, 1975,
to June 30, 1977. The purpose of this study was to provide comprehen-
sive chemical and physical characterization of fluidized bed combustion
materials with emphasis on beneficiation and/or disposal of these materials.
Fluidized bed combustion materials were obtained from the Argonne National
Laboratory, the Combustion Power Company, and the Exxon Research and
Engineering Company. Samples of regenerated bed materials from Argonne
National Laboratory were also characterized.
In general, granular bed material consists of three zones. The outer
zone consists primarily of CaSO* and ranges in thickness from 2 to 25
microns, a center zone 60 to 150 microns consists of CaSOi, and soft-
burned CaO, and a third zone (in samples with incomplete sulfation)
consists primarily of original absorbent.
Particle size analysis shows that in general, CaSO* and Ca(OH)2 concen-
tration increases as the size of the particle decreases and that CaC03
is more concentrated in the larger particles.
The fluidized bed combustion residue was found to stabilize sludges
produced by wet lime/limestone scrubber systems such that they would not
reslime upon contact with water.
iii
-------
CONTENTS
Abstract iii
Figures v
Tables vi
Section
1. Introduction 1
2. Conclusions 2
3. Instrumental Techniques of Characterization 4
4. Solids Characterization 5
5. Size Classification and X-ray Studies 12
6. Fluidized Bed Material—Sludge Stabilization Tests .... 14
iv
-------
FIGURES
Figure Page
1. Scanning electron micrographs for Combustion Power Corporation
sample 20 LP 24
2. Optical photomicrographs for Argonne samples LST-1 and LST-4 26
3. Scanning electron micrographs for Argonne samples LST-1 and LST-4 . . 28
4. Optical photomicrographs for Argonne samples CCS-10 and RGL-10 .... 30
5. Scanning electron micrographs for Argonne samples CCS-10 and RGL-10 . 32
6. Scanning electron micrographs and x-ray maps for Exxon samples
30.1, 30.2, and 32.0' 34
7. Sieve fraction analysis for CPC-20 LP 35
8. Sieve fraction analysis for Argonne samples E-11576 and E-11624 ... 36
9. Sieve fraction analysis for Argonne samples LST-1 and LST-4 37
10. Sieve fraction analysis for Argonne samples CCS-10 and RGL-10 .... 38
11. Sieve fraction analysis for Exxon samples 30.1 and 32.0 39
12. Sieve fraction analysis for Exxon samples 30.2 and 19.3 40
-------
TABLES
Table Page
I. Chemical analysis of fluidized bed residues 15
II. Chemical analysis of fluidized bed combustion-regeneration residues . 16
III. Qualitative composition of fluidized bed residues from x-ray data . . 17
IV. Test strengths of cured FBCR-sludge mixtures 22
V. Conversion table of USA Standard Sieve Sizes 23
vi
-------
Section 1
INTRODUCTION
Residue materials produced by fluidized combustion of coal
have been previously characterized in the published literature, but as a
general rule such characterizations have been either limited to one
sample source or have been reported as a minor part of some larger
study.
It has been the primary purpose of this study to provide a
comprehensive petrographic, mineralographic, and chemical characteriza-
tion of fluidized bed combustion materials from a number of sources,
including high- and low-pressure combustion beds and regeneration
systems. With an eye towards beneficiation and/or disposal of these
materials, auxiliary studies have considered the particle size distribu-
tion found in these samples and their chemical composition as a function
of size fraction and have investigated their use as stabilizing additives
for flue gas desulfurization sludges.
These studies, both qualitative and quantitative, have used
comparative optical and electron microscopy, x-ray diffraction, infrared
analyses, and electron microprobe analyses to provide a comprehensive
study of the composition and morphology observed in these samples.
This report presents data collected on fluidized bed combus-
tion materials provided by the Argonne National Laboratory, the Combustion
Power Company, and the Exxon Research and Engineering Company over the
period July 1, 1975, to June 30, 1977.
-1-
-------
Section 2
CONCLUSIONS
Bed material and flyash from high- and low-pressure fluidized
bed combustors have been characterized petrographically, chemically, and
with the aid of scanning electron microscopy, the electron microprobe,
and x-ray powder diffraction. Granular bed materials generally consist
of three zones. The outermost zone consists of a surface layer, or
veneer, and ranges in thickness from 2 to 25 microns. This zone consists
primarily of CaSO*. Metallic oxides are generally present; their content
is seen to range from a light Fe203 staining to heavy encrustations of
siliceous glass containing large amounts of FeaOs (hematite) and Fe30i,
(magnetite). The physical integrity of this surface reaction zone is
observed to range from an integral part of the granule body characterized
only by color and crystallite size differences, to an easily separable
physical shell which, while relatively hard, is not well associated with
the body of the granule. The secondary reaction zone underlies this
surface veneer; its thickness may range from 60 to 150 microns or, in
well sulfated samples, to the granule's core. It consists of CaSO* and
soft-burned. CaO for limestone beds; MgO is sometimes seen with dolomite
beds. Granules which have been incompletely sulfated will have a third
zone or core consisting primarily of original material (with the exception
of MgC03 which has not been observed) and small amounts of CaO or MgO.
Samples of regenerated bed materials have also been characterized.
Those samples studied have been exposed to 10 cycles of sulfation and
regeneration and are easily characterized by their outer layer which,
while not necessarily thicker than that shown by once-through granules,
is much higher in iron and silicon compounds and exists as a vitreous,
amorphous, siliceous glass containing large amounts of FeaOs and Fe30<,.
This encrustation is presumed to form gradually upon successive stages
of regeneration.
Particle size fraction analyses have been performed on all
samples. It has been shown that the content of CaSO* and Ca(OH)2 generally
increases with decreasing size fraction and that CaC08 is more concen-
trated in the larger fractions. The Ca(OH)2 content increase in the
smaller fractions is attributed to conversion of the softer CaO which
is attrition ground from broken or fractured larger granules. SiOa has
not shown a predictable composition relationship to size fraction. A
sample described as "ash" is shown to consist primarily of finely ground
CaSO*. The process of fines transport from a fluidized bed and collection
by cyclone is as likely to collect CaSOfc as it is to collect "ash" since
the ash component is seen to be concentrated on the surface of intact
granules. Fines within the bed are likely to consist of the softer
components of CaO and CaC09. These components are less resistant to
attrition grinding by bed turbulence and will be quickly sulfated due to
their high surface area to volume ratio.
-2-
-------
It has been shown that fluidized bed combustion residue may be
used to stabilize the CaS09*l/2H20 sludges produced by wet lime/limestone
scrubbing systems and that the fixed materials are not subject to resliming
on contact with water. Short-term physical strengths appear to be
higher for sludges containing flyash than for ash-free sludges. Increased
strengths of stabilized materials are attributed primarily to formation
of massive crystalline gypsum.
-3-
-------
Section 3
INSTRUMENTAL TECHNIQUES OF CHARACTERIZATION
Fluidized bed combustion materials from the Argonne National
Laboratory, the Combustion Power Company, and the Exxon Research and
Engineering Company have been characterized. A number of techniques
have been employed in this study. Scanning electron microscopy, using a
Cambridge S-4 SEM, and optical microscopy have provided comprehensive
petrographic and mineralographic information on these samples. An
energy-dispersive x-ray analyzer was used in connection with the SEM to
provide electron microprobe qualitative information regarding chemical
composition of the materials.
X-ray powder diffraction of bulk samples and of separated size
fractions was used to determine qualitative verification of petrographic
data (as was infrared analysis) and to provide relative estimates of
composition versus size fraction.
Various physical test equipment was used to determine uncon-
fined compression strengths of materials as an indication of the degree
to which they had been stabilized.
-4-
-------
Section 4
SOLIDS CHARACTERIZATION
Samples of fluidized bed materials, bed reject materials, and
flyash were obtained from combustors operated by the Combustion Power
Company, Inc., the Argonne National Laboratory, and the Exxon Research
and Engineering Company. Detailed results of the characterization
studies on these samples are given below. Chemical analytical results
are shown in Tables II and IV.
Combustion Power Company
One sample each of fluid bed material and flyash was received
from a 20-inch (diameter) by 24-inch (depth) low-pressure combustor
operated by the Combustion Power Company. The samples were obtained
after 1003 hours of operation at 899°C from a test run. High (3.11 percent)
sulfur coal was the fuel, dolomite was the sulfur dioxide absorbent
(ratio of 0.24 Ib of dolomite to 1.0 Ib of coal), and Burgess No. 10
clay pigment was used as a corrosion suppressant (comprising 0.4 percent
of the total bed weight). The results of chemical analyses of these
samples are included in Table I.
The bed material sample was received in the form of orange to
brick-red irregular granules of 0.5 to 1.0 mm in diameter (Figure 1A).
Petrographic investigation indicates that this material consists primarily
of CaSOi. (anhydrite) and metallic oxides, mostly CaO, pseudomorphic
after the original dolomite structure. Microchemical tests show Mg to
be fairly abundant, although no free-formed magnesium salt could be
identified; x-ray diffraction analysis indicates the existence of MgO.
Most of the granules appear as dense units upon which a 2 to 5 micron
hardened, reddish shell of hematite has been deposited. While the shell
material itself is very hard, it is fairly easily separated from the
body of the granule; a small percentage of the granules, as received,
had sections of their "shell" broken away, exposing the softer body of
the granule. The contrast between the comparatively smooth hematite
surface coating and the coarser, crystalline, underlying layer of CaSO<,
is readily seen in Figures IB and 1C. Towards the center of the granules,
the CaSOj, occurs in a more massive form (Figure ID); a high percentage
of the anhydrite is optically amorphous. Qualitative analyses of the
total granule material by x-ray powder diffraction verify CaSO«, as the
major phase, with lime (CaO) being present in somewhat lesser quantities.
Quartz, Ca(OH)a, and MgO are present in small amounts.
The flyash portion of this sample was received in the form of
finely divided, 5- to 25-micron, orange-red solids (Figures IE and IF).
The major fraction of this material is CaS04, part of which is crystalline.
-5-
-------
Microchemlcal tests show that part of the CaSO* IB present as soluble
anhydrite; i.e., addition of water to the sample results in the forma-
tion of a significant quantity of gypsum. Hematite is observed petro-
graphically as a minor phase with quartz, CaO, and a clay-like siliceous
material all present in trace quantities. X-ray powder diffraction
analyses indicates, in addition to the components mentioned above, the
presence of CaSOh»3MgSOfc in trace quantities.
Argonne National Laboratory
Sample E-11576 was taken from a high-pressure fluidized bed
combustor, 6 inches in width and with a bed depth of 3 feet, operated at
900°C at a pressure of 8 atmospheres. The fluidizing gas velocity (with
17 percent excess air) was approximately 0.9 m/s and Grove limestone was
used as the absorbent at a Ca:S molar feed ratio of 1:5. The sample was
received in the form of dark brown granules with diameters ranging from
0.1 to 1.5 mm. Petrographic examination Indicates that the granules
consist primarily of CaSO« and CaCO,, with small amounts of CaO. Micro-
chemical tests indicate trace quantities of soluble anhydrite. Qualitative
analyses by x-ray diffraction and infrared spectrophotometry verify the
presence of anhydrite, limestone, and lime, including trace amounts of
quartz and hematite. A given individual granule will be covered with an
outer layer up to 25 microns in thickness consisting of CaSOj, and Fea09.
The thickness of this outer veneer will determine the color of the
granule, with the lighter colored granules having thinner veneers.
Under this surface coating another zone is observed, ranging up to 100
microns and consisting of CaSO* and soft-burned, amorphous CaO. These
granules show a core or central zone of poorly crystallized CaCO» and
CaO, ranging in diameter from 500 to 900 microns.
A second sample (E-11624) was taken from the combustion system
described above with the stated operating conditions, but using Tymochtee
dolomite as the absorbent. The sample was received in the form of light
brown granules, with diameters ranging from 0.1 to 1.5 mm. Fetrographic
examination shows that the granules consist chiefly of aggregates of
CaSOi, and soft-burned, amorphous MgO and contain approximately 10 to 20
percent CaCO». In this sample, the outer layer is only 5 microns in
thickness (accounting for the lighter color) and consists of anhydrite,
Fe209, and dead-burned MgO. The second zone in this sample extends to
the core of the particle and consists of CaSO* and soft-burned MgO (possibly
a form of MgO-MgC09-Mg(OH)2 solid solution) which is amorphous with a
refractive index of approximately 1.64. The presence of anhydrite,
CaC03, and MgO is verified by x-ray diffraction. Semiquantitative
infrared spectrophotometric analyses show a gross sample composition of
approximately 80 percent sulfate and 20 percent carbonate, with small
amounts of CaO, FeaOs, and quartz.
-6-
-------
Four additional samples wars obtained from tha Argonne National
Laboratory. Tha aamplaa conaiatad of both apant (aulfatad) and regenerated
granular materials from limaatona and dolomite bada, Samplaa LST-1
(originally Columbia limaatona) and LSI-4 (originally Gaorgia marble)
wara removed from a fluidiiad oombuation ayatern oparatad at 870'C and
approximately 4 atmoepherea. Tha Ca:S ratioa uaad in tha two taata ware
1.6 and 2.2, raapactivaly. Tha fluidiiing gaa velocity (containing 17
percent excess air) waa 0.76 ra/e for L8T-1 and 0.82 a/a for LST-4.
Samples CCS-10 (originally Tymochtee dolomite) and RGL-10 (originally
Greer limestone) were obtained from fluidiiad bed combustion-regeneration
systema operated at 1100'C and Approximately 1,5 atmoepherea after 10
cyclea of regeneration. The gaa velocity uaad was 1.2 m/s,
In sample LST-1, petrographic examination indicates that three
major typea of particles are preaent. Approximately 10 percent of
these consist of CaCO» as single rhombic cryatala up to 1200 microns in
length, with a thin (up to 20 microns) surface veneer of reaction product
which is present aa single-plate crystals of CaSO* up to 10 microns
acroas. Another 15 percent of the sample occurs as anhydrite crystals
aggregated into units with a maximum aise of 150 microns. The individual
CaSOi, crystals comprising these aggregates may range up to 15 microns
and are very slowly soluble in hot, concentrated acids. The other
three-fourths of the,sample is coarae granular aggregates of CaCOa with
a 25-micron surface veneer of CaSO<, aa plate crystals with a maximum
length of 15 microns. This veneer shows iron staining with iron present
as FeB0|. The presence of numerous agglomerated lines shews that the
sample has been subjected to a long period of attrition grinding.
Sample L8T-A is similar in color and appearance to L8T-1?
about two-thirds of the sample occurs as granular aggregates up to 1200
microns in diameter. These granules consist of GaGOt crystals with a
35-micron surface veneer. This outer layer is formed of Ga80« crystals
with a maximum dimension of 15 microns and shews a small amount el 4?en
staining as FeiOa. Approximately one-fourth §1 the sample is single
crystals of CaC08 up to 1200 mlerons across and eeated with a ll-aieren
surface layer of Ga§0«. Less than 10 percent of the sample material
occurs as 230-mioron GaGPa aggregates stained with FeaOai Virtually all
of the CaSCu present in this saapU is Ihe iageluble anhydrite form.
Neither of the two sanplee, JJT=1 tr UT-4, exhibits eig§?§te,
defined, reaction senea (except for external lays? fenaatiefi) a§ ae the
previously examined gulf ales' materials. Qranuleg §1 fe§th §1 Ihege
eaiapleg were prepared lor SIM exaffliaatioa by efflbeaiing taea ia an epexy
potting eeapound and grinding Ihe resultant gelid t§ reveal a @f§§§
seetiea of their internal §t?ueture§i Qplieii phei§B4etegfaphg el the
samples thus prepared are shewn in Figures 2A aM IB. The selllei
appearanee §f nost gravies and laek §1 ibvitug gene ieraallea auppetl
the agguntpU§fi lhalt eepeaalag en the pa?U@4@ p@f§§4ly, gulf alien and
eentaffiinaliea by ineris proeeede vilhia Ihe pafllele al a gl§we? fal@
lhan on Ihe gurfaeei fhe laek el reaeliea a§a@ fefaalien is allfiluled
-------
to this difference in porosity; less densely aggregated stones are more
likely to show such formations.
Patterns of interior sulfation along grain boundaries are
easily seen when the prepared granules are lightly etched with hydro-
chloric acid. This procedure dissolves away the highly soluble CaCOs
component, while leaving the CaSO* portion relatively untouched. Figure
3A shows a SEM photomicrograph of such an etched particle. The web-like
nature of the CaSOt, is easily seen, sulfation having proceeded along
internal surface areas provided by the granule's porosity. The relatively
smoother area seen on all sides but the lower left of the web structure
is the unetched surface of the potting compound. Figures 3B and 3C show
views of a cross section of another granule, both before and after
etching. The internal network of CaSO*, barely visible as trace outlines
on the unetched granule (Figure 3B), is clearly seen after etching
(Figure 3C). The relatively darker or smoother region in the lower
right corner of the photograph is again unetched potting compound.
Figures 3D and 3E show an example of edge (surface) sulfation
on a granule of sample LST-4. In Figure 3D, the thin surface of sulfation
(seen in cross section) is only faintly visible. After light etching
(Figure 3E) this layer clearly stands out. Electron microprobe analysis
verifies that sulfur is a major component of this edge structure and is
present only in residual amounts in the body of the particle. The deep
longitudinal dissolution features running northeast to southwest on the
photograph are artifacts resulting from preferential dissolution of the
CaC03 along lattice planes caused by localized lattice defects of a
nonstoichiometric nature, or strain effects caused by grinding.
Samples CCS-10 and RGL-10 were received in the form of 0.5 to
1.0 mm dark brown to black granules, with less than 5 percent of the
material present as fines of less than 60 mesh (see Table V for con-
version to microns).
Upon petrographic examination, two basic types of particles
are seen in sample RGL-10. One-fourth of the sample consists of black,
magnetic units consisting of a siliceous glass (refractive index of
1.545) and black opaque particles of magnetite present as cubic pseudomorphs-
possibly after pyrite. These particles produce a sulfide odor upon
dissolution in HC1. Approximately two-thirds of the sample is present
as brown, iron oxide-stained granules of CaO with a 10- to 12-micron
surface veneer consisting of a mixture of CaSO* (about 1 micron crystals),
siliceous glass, and an occasional black, magnetic, cubic pseudomorph at
the surface. The CaO approaches a dead-burned condition; it has a mean
refractive index of 1.77 to 1.78. The iron content of this sample
appears to be unusually high. This may be a result of a gradual buildup
of metallic oxides during successive cycles 'of combustion and regeneration.
The occurrence of soluble anhydrite in this sample is negligible.
-8-
-------
Sample CCS-10 consists of two types of particles. About 15
percent are magnetic and consist of a deeply colored glass having a mean
refractive index of 1.70 to 1.74, with a trace of incipient crystallization
of unknown composition (possibly an iron silicate). Cubic pseudomorphs
are a significant component of this magnetic fraction. The remainder of
the granules range from light brown to dark gray in color due to various
degrees of iron staining in the outer 10-micron veneer. This surface
layer consists of an amorphous slag and overlies a secondary reaction
zone, approximately 40 microns in thickness, consisting of CaSO,,. The
core of these granules is composed of CaCOs and MgO. The core MgO
component is soft-burned. No soluble anhydrite was found in this sample.
Both RGL-10 and CCS-10 were prepared for SEM examination by
the embedding and grinding process described previously. Figures 4A and
4B show optical photomicrographs of the prepared samples; note examples
of surface encrustations of metallic oxides and reaction zones exposed
in the cross-sectional views of several granules (marked by arrows).
Figures 5A and 5B show cross-sectional views of representative
CCS and RGL granules. The thick vitreous crust of inert material which
interferes with both regeneration and sulfation is easily seen; it is
shown by electron microprobe analysis to contain a high percentage of
aluminum, silicon, and iron. Similar analyses of the granules' interior
regions show a preponderance of calcium, or where dolomite is used,
calcium and magnesium.
The decreased reactivity of absorbent after successive cycles
of regeneration is attributed primarily to crust formation. No evidence
of sintering in the core of these granules has been observed.
Exxon Research and Engineering Company
Sample 19.3 (bed materials) was removed from a high-pressure
combustor operated at a temperature of 900°C and a pressure of 9 atmospheres
for a period of 6 hours. The bed dimensions were 12.5 inches wide by 4.7
feet deep; the gas velocity (at 6 percent excess air) was 1.9 m/s. Grove
limestone was used as the absorbent with a molar feed ratio Ca:S of 1.5.
Received in the form of dark brown granules averaging 1 mm in diameter,
a quantity of fines was also observed, presumably as the result of
fracture of the larger granules (which are not structurally strong) by
circulation within the bed or in handling or shipping. Petrographic
examination shows that the granules have a surface layer up to 5 microns
thick of CaSO* and Fe209. The remainder of the granule is generally
divided equally between a secondary reaction zone containing CaSO,, and
CaO and a central core section composed of CaCOs and CaO. X-ray powder
diffraction and infrared analyses identify CaSOi, and CaC09 as major
components present in a 2:3 ratio with CaO, FeaO,, and quartz all
present in amounts smaller than 5 percent.
-9-
-------
Sample 30.1 (bed reject materials) was removed from the combustor
as described for the previous sample with the same operating conditions
except that a Ca:S molar feed ratio of 3.7 was used, and the amount of
excess air was Increased to 13.7 percent. As received, the sample
consisted of dark brown granules ranging in diameter from 1 to 2 mm.
Optical microscopic examination reveals that these granules also consist
of three separate and distinct zones. The surface of the granules is
covered with a thin (up to 5 microns) layer of dead-burned CaO, insoluble
anhydrite, and Fea08. Underneath this layer, ranging in thickness from
60 to 150 microns, lies a second zone of soluble anhydrite and soft-
burned CaO. The central zone, or core, consists chiefly of poorly
crystalline CaCOa and soft-burned CaO. X-ray diffraction studies of the
bulk sample verify the presence of these components and show, in addition,
small quantities of quartz. Semiquantitative Infrared analyses indicate
a CaC09 to CaSO* ratio of 3:1, and Identify CaO, quartz, and FeaO»
present in amounts smaller than 5 percent total.
Sample 30.2 (bed reject materials) was obtained from the
combustor as described above. During this run, a Ca:S ratio of 3.7 was
used, the bed temperature was raised to 930°C, and 17% excess air was
used as the fluidizing gas at a velocity of 8 feet/sec. This sample
consisted of brown to black granules ranging in diameter from 0.5 to 2.5
mm. While easily crushed with fingertip pressure, these granules are
much stronger structurally than previous Exxon samples. Here, the outer
layer is 3 to 5 microns thick and again consists of CaSO* and metallic
oxides, but the second reaction zone composes the bulk of the particle;
little or no core zone exists. Qualitative analysis by x-ray Indicates
primarily CaSO* and CaO; but infrared studies show, in addition, smaller
quantities of CaCO,, FeaOi, and quartz. A CaCO» to CaSO* ratio of 1:12
is indicated.
Sample 32.0 consisted of bad materials removed from a run in
which Pfizzer dolomite was used as the absorbent. This teat run was
made at a pressure of 5.9 atmospheres and at 840°C; 20 percent excess
air was used at a velocity of 1.5 m/s. A Ca:S ratio of 0.75 was used.
The sample was received In this laboratory in the form of dark brown to
black granules with approximate sizes ranging from 0.5 to 2 mm. The
surface venesr in these particles is between 3 to 10 microns in thickness,
consisting of CaSO*, FegOt, and hard-burned MgO (collapsed, dense,
crystalline units with a refractive index of 1.735). The secondary zone
of reaction constitutes ths major fraction of the granule and is composed
of CaCO» and soft-burned, amorphous MgO. The small canter zone consists
of poorly crystalline CaCOi and soft-burned MgO. Infrared analysis of
the rock sample shows the presence of CaCO» and CaSO* with a 1:5 ratio.
Tracts of CaO, quartz, and F«|0S ar« also Indicated. MgO is shown by x-ray
diffraction studies.
Samples of ths abovt materials were mounted and subjected to
grinding and polishing as previously described to expose cross sections
of the granules for observation. Figures 6A, 6C, and 6E show 8EM photo-
micrographs of granule sections as viewed with secondary slsctron imaging
-10-
-------
(normal SEM operating mode). The secondary reaction zone in these
granules is seen as that area near the periphery of each granule which
is relatively smoother than the granule interior. This relatively
smooth appearance is due to the fact that this CaSO(,-containing zone is
generally harder than the CaCOs-CaO core zone and thus more resistant to
abrasion. In these sections the secondary zone extends from 50 to 200
microns into the body of the granule. The irregular white tracing
superimposed on Figure 6A indicates the sulfur content of the section
immediately below the line. As this tracing approaches the left edge of
the granule it rises sharply, indicating an increase in sulfur content
at the particle's periphery, then drops back to a low level across the
granule's interior region indicating that sulfation has not yet proceeded
to completion. The sulfur content again rises as the electron beam
reaches the right edge of the granule.
Figures 6B, 6D, and 6F correspond to the views shown on the
left-hand side of the page but show the granules' cross section as
viewed by the 2.307 kev (sulfur) x-rays as emitted by the sample when
struck by the scanning electron beam. These photographs may be described
as "sulfur maps" of the granules and show the relative distribution of
sulfur on and within the granule. The usually peripheral secondary
reaction zone is shown to be rich in sulfur, but note Figure 6F where
sulfation has proceeded along structural cracks into the body of the
granule.
-11-
-------
Section 5
SIZE CLASSIFICATION AND X-RAY STUDIES
Samples (as received) of fluidized bed materials were subjected
to size classification by dry seiving and x-ray powder diffraction
analysis to determine the general composition of various size fractions
and the compositional differences between them. The seive analyses are
reported in Figures 7 through 12, and the fraction composition data are
shown in Table III.
The samples of bed materials and flyash from the Combustion
Power Company show the expected size distributions. Two-thirds of the
bed materials are +100 mesh while two-thirds of the flyash (collected
from a second-stage cyclone) is sized below 200 mesh. For mesh size-
micron conversion, see Table V. In the bed material the content of
Ca(OH)2 is seen to increase with decreasing particle size. Since the
largest fractions are whole granules with a relatively Intact inert
outer shell, only the smaller, broken granules will expose unreacted CaO
to the atmosphere, forming the Ca(OH)2. The bulk of the ash material (-200
mesh) is seen to consist of the same material as reported by petro-
graphic analysis (CaSO<,, SiOa, and Fea09).
The two high-pressure (8 atmospheres) bed samples from the
Argonne National Laboratory (E-11576 and E-11624) are interesting in
that they display such differences in particle size distribution. The
sample containing the largest (more than 30 percent) amount of -60 mesh
particles is E-11576. This sample has a 25-micron outer layer, whereas
E-11624 (derived from dolomite) has only a 5-micron shell. Since this
outer, relatively inert, layer is usually structurally stronger than the
core of the granule, one would expect, under similar conditions, more
attrition grinding to be evidenced by the sample with the thinner shell.
While the sample E-11576 may have been subjected to more turbulent
conditions within the bed or rougher handling before receipt by this
laboratory, another possibility is that the inert shell on this sample,
while quite strong itself, is not particularly well cemented to the
particle body. The outer veneer on some samples has been observed to be
weakly "attached" to the granule body; in some cases it may easily be
flaked off. This would have exposed the much softer granule Interior to
further fracture and attrition grinding during any subsequent handling
step. In sample E-11576, the content of CaO is seen to decrease with
decreasing particle size. Furthermore, there is an accompanying increase
in Ca(OH)2 content as the exposed lime is hydrated.
Samples LST-1 and LST-4, from 4 atmosphere beds, show essentially
the same particle size distribution with three-fourths of each sample
being larger than 60 mesh. In both samples, the content of both CaO and
Ca(OH)2 are seen to increase with decreasing size fraction, the increase
-12-
-------
in Ca(OH)a being dependent on exposure of CaO. Si02 is a relatively
constant component of LST-4. It is useful to consider that the stone
used for LST-4 contained 1.3 weight percent of SiOa initially, as compared
to 0.2 percent for the limestone that produced LST-1. For both samples,
the CaSOj, content increases with the smaller fractions and the CaC09
content decreases.
Again, samples CCS-10 and RGL-10 (10th cycle of regeneration)
show the same particle size distribution. The dolomite-derived material
(CCS-10) shows major amounts of MgO throughout all size ranges although
its CaSOt, component is still present in noticeable quantities, indicating
regeneration has not been completely successful. In both samples,
Ca(OH)2 increases with decreasing particle size, as more residual or
regenerated CaO is exposed to the atmosphere. Both the Fe30<, and MgO»2CaO»2Si02,
which are found in trace amounts throughout all size ranges, are assumed
to originate on the surface veneer of the granules during the combustion
cycle.
Exxon sample 30.1 contains about 30 weight percent minus 60-
mesh material. Over the size range of solids shown, both the CaSOfc and
CaO content increase with decreasing particle size. Exxon sample 32
(dolomite bed) shows the same general size distribution, but here the
CaSOj, content is roughly constant. In both samples, CaC03 generally
decreases with decreasing particle size. In Exxon 30.2, both CaO and
CaSOfc are fairly constant regardless of size fraction. This sample
contains less than 3 weight percent minus 60-mesh material, indicating
very little attrition grinding has taken place. Again, the Ca(OH)a
component increases with decreasing particle size.
In summary, within the range of samples studied the content of
both CaSOfc and Ca(OH)a is seen generally to increase with decreasing
particle size, while CaCOs content decreases under the same conditions.
-13-
-------
Section 6
FLUIDIZED BED MATERIAL—SLUDGE STABILIZATION TESTS
Sludges produced by wet lime/limestone S0a scrubbing systems
have produced severe disposal problems. A partial solution to this
problem lies in fixing or stabilizing this sludge with various additives.
Several commercial processes exist to accomplish this. It has been
suggested that fluidized bed combustion residues may also be used to
stabilize these sludges. In an attempt to determine the feasibility of
this idea and to develop a simple laboratory stabilization test procedure,
fixation tests were performed with fluidized bed combustion residue and
sludges produced from two different wet scrubbing systems.
The fluidized bed material used was a 1:1 ratio of the Combustion
Power Company bed material and second-stage flyash. The bed material
was ground to -200 mesh before mixing. On a weight percent basis,
sludge number 1 consisted of approximately 30 percent ash, 8 percent
CaSOi,»2H20, 54 percent CaS03«0.5H20, and 8 percent CaC03. Sludge number
2 contained about 1 percent ash, 9 percent CaSO<,*2H20, 77 percent CaS03»
0.5H20, and 14 percent CaC03. The solids component of both sludges was
essentially -200 mesh.
The sludges used were allowed to drain on a filter to remove
most of the liquor, which was saved. Appropriate amounts of fluidized
bed material and sludge were then mixed with sufficient amounts of
liquor added to achieve approximately 75 weight percent solids. Cylindrical
cores of the resulting mixture measuring 4 cm in length and 2 cm in
diameter were separated and allowed to cure in a container held at room
temperature and 100 percent humidity from 5 to 11 days. The unconfined
compression strength of the cured pellets was then measured.
The results of these tests are shown in Table IV. The compressive
strength increases with time and is directly related to the percent of
fluidized bed residue in the original mixture. Pellets produced from
sludge number 2, containing essentially no flyash, were noticeably
weaker. For all mixtures, pellet fragments immersed in boiling water
for 1 day exhibited no resliming.
X-ray diffraction examination of the fixed pellets indicated
that a large quantity of gypsum (CaSO*»2HaO) has been formed, presumably
by hydration of the soluble anhydrite component in the fluidized bed
material. SEM examination indicates large, massive gypsum crystal
growth throughout the body of the sample. This type of structure has
been seen in gypsum scale removed from the internal surfaces of wet
limestone S02 scrubbing towers. The strength of this material is
primarily attributed to this massive and interlocking internal crystal
growth.
-14-
-------
TABLE I
Chemical Analysis
Constituent
Na+
K+
cr
Ca+'
Mg+*
C02"2
S03"2
so,,'2
Si
Fe
Al
Acid insolubles
CPC
20" LP
bed
0.07
0.04
ND3
23.0
13.1
0.4
NDa
29.7
11.1
1.7
0.72
14.7
CPC
20" LP
ash
0.14
0.13
<0.1
12.7
6.4
1.3
<0.1
33.6
0.55
0.95
0.51
36.0
Exxon
Run
19.3
0.01
0.03
<0.1
35.9
0.36
33.5
0.1
14.7
0.44
0.72
0.26
4.3
(Weight
Exxon
Run
30.1
ND3
0.02
NDa
36.0
2.6
36.0
ND3
14.2
0.29
0.39
0.15
2.1
Percent)
Exxon
Run
30.2
ND3
0.02
ND3
47.0
1.1
2.6
NDa
25.9
0.62
0.68
0.34
2.8
Exxon
Run
32.0
ND3
0.01
ND3
34.8
6.0
11.9
NDa
29.5
0.40
0.67
0.21
3.7
Argonne
Run
E-11624
0.05
0.14
ND3
22.7
14.0
7.6
ND3
34.7
0.96
0.36
0.50
3.7
Argonne
Run
E-11576
NDa
ND3
NDa
35.9
0.39
20.5
NDa
31.2
0.47
0.48
0.31
1.8
ND = not determined.
-------
TABLE II
Chemical Analysis (Weight Percent)3
Constituent
S
C09"
Ca
Mg
C
Si
A1203
Fe203
CCS-10 RGL-10 LST-1
3.2 1.0 8.0
35.6
25.7 37.6 36.5
1.0
8.2
6.1 10.4 0.9
2.2
0.6
LST-4
6.3
36.8
33.6
7.1
Analytical data supplied by Argonne National
Laboratory.
-16-
-------
TABLE III
Qualitative Composition From X-Ray Data*
Sample
CaSO«.
CaO
CaCOa Ca(OH)a S10a
MgO
Fea03
> 30% (major); 30% > m > 5% (minor); tr < 5% (trace).
Other
+30
-30 to +60
-60 to +100
-100 to +200
-200 to +400
-400
+30
-30 to +60
-60 to +100
-100 to +200
-200 to +400
-400
m
M
M
M
M
M
M
M
M
M
M
M
_
tr
tr
-
-
tr
_
-
-
-
-
-
CPC
_
-
tr
-
tr
tr
«.
-
-
-
-
-
20" LP bed
_
tr
m
m
tr
m
CPC 20" LP
_
-
-
-
-
-
material
M - tr
m m -
- m -
tr m -
tr m -
tr m -
ash
m tr m
m tr m
m tr tr
m tr m
m - m
M - m
CaSO^OMgSO*. (M)
CaSO«,«3MgSO«, (m)
CaSOi,»3MgSOi. (m)
CaSO««3MgSOfc (m)
CaSO^OMgSO,. (m)
CaSOfcOMgSO,. (m)
Argonne E-11576
+20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200
M
M
M
M
M
M
m
m
m
tr
tr
tr
M
M
M
m
m
m
—
_
—
tr
tr
m
tr
tr
tr
- - tr
_ _ _
— — —
-------
TABLE III (continued)
Qualitative Composition From X-ray Data'
Sample
CaSOt,
CaO
CaCO.
Ca(OH)a
SiOa
MgO
FeaQ9
Other
Argonne E-11624
+20
-20 to +30
-30 to +60
-60
+20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200
+20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200
M
M
M
M
m
m
m
M
M
M
m
m
m
M
M
M
_
-
-
tr
_
-
tr
m
tr
tr
_
-
-
tr
tr
tr
m
m
tr
m
M
M
M
m
m
m
M
M
M
M
M
m
-
-
-
tr
Argonne LST-1
-
-
-
tr
tr
m
Argonne LST-4
—
-
-
-
tr
tr
tr m
tr m
m m
tr m
- -
- -
- -
— —
-
— —
tr
tr
tr
tr
tr
_ _
CaMg(C03)a (tr)
-
CaMg(C03)2 (tr)
CaMg(C03)2 (tr)
-
-
-
-
-
—
—
-
-
-
-
—
> 30% (major); 30% > m > 5% (minor); tr < 5% (trace).
-------
TABLE III (continued)
Qualitative Composition From X-ray Data'
Sample
CaSO;. CaO CaC03
Ca(OH)2 SiOa MgO FeaQ3
Other
+20
-20 to +30
-30 to +60
-60
+20
-20 to +30
-30 to +60
-60
+12
-12 to +20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200 to +400
-400
m
m
m
m
m
tr
tr
m
m
m
m
M
M
M
M
M
m
tr
m
m
M
M
M
M
_
—
-
tr
tr
tr
tr
tr
Argonne CCS-10
tr tr M
tr tr" M
tr tr M
m tr M
Argonne RGL-10
_
-
-
-
M
M
M
M
m
m
m
M
tr
tr
m
M
_
_
tr
-
—
tr
m
m
M
m
m
M
Exxon 30.1
tr
tr
tr
tr
—
—
tr
—
tr
tr
tr
tr
tr
tr
tr
tr
tr
tr
tr
—
tr
m
m
tr
m
tr
tr
m
_
_
tr
tr
tr
tr
—
—
Fe30<, (tr), MgO«2CaO-2SiOa (tr)
Fe30,, (tr), MgO«2CaO»2S102 (tr)
Fe90i, (tr), MgO«2CaO«2S102 (tr)
Fe30<, (tr), MgO»2CaO«2Si02 (tr)
Fe30<, (tr)
> 30% (major); 30% > m > 5% (minor); tr < 5% (trace).
-------
TABLE III (continued)
Qualitative Composition From X-ray Data*
?
Sample
+12
-12 to +20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200 to +400
-400
+12
-12 to +20
-20 to +30
-30 to +60
-60 -to +100
-100
CaSOi.
M
M
M
M
M
M
M
M
M
M
M
M
M
M
CaO
tr
m
M
M
M
m
m
m
M
M
M
M
M
M
CaCOs
Exxon 32
m
m
m
m
tr
tr
tr
tr
Exxon 30.2
tr
-
-
-
tr
tr
Ca(OH)a
-
-
-
tr
tr
tr
m
m
tr
tr
tr
m
m
M
SiOa
tr
tr
tr
-
-
-
-
—
tr
tr
tr
tr
-
tr
MgO
m
m
tr
tr
tr
tr
-
—
_
-
-
-
-
"•
FeaQ3
—
-
-
-
-
-
tr
-
_
-
tr
m
-
—
> 30% (major); 30% > m > 5% (minor); tr < 5% (trace).
-------
TABLE III (concluded)
Qualitative Composition From X-ray Data*
i
Is}
Sample
+12
-12 to +20
-20 to +30
-30 to +60
-60 to +100
-100 to +200
-200 to +400
-400
CaSCU
M
M
M
M
M
M
M
M
CaO
..
tr
-
tr
m
m
m
m
CaCOs
Exxon 19.3
m
m
m
m
tr
tr
tr
tr
Ca(OH)2
_
-
-
-
tr
tr
m
m
SiOa
tr
tr
tr
tr
-
-
-
—
MgO Fea09
_ _
-
- -
-
tr
-
tr
_ _
> 30% (major); 30% > m > 5% (minor); tr < 5% (trace).
-------
TABLE IV
Test Strengths of Cured FBCR-Sludge Mixtures
Test
Number
1
2
3
4
5
6
7
8
9
Composition on solids basis
(weight percent)
FBC
100
90
75
50
25
90
75
50
25
Sludge 1
0
10
25
50
75
0
0
0
0
Sludge 2
0
0
0
0
0
10
25
50
75
Unconfined compression strength
(cured at room temp, and 100% humidity)
5 days
300
280
220
70
60
240
200
100
50
8 days
480
350
270
90
80
250
220
110
50
11 days
NT3
400
300
120
100
250
200
140
70
= not tested.
-22-
-------
TABLE V
Conversion Table of USA Standard Sieve Sizes
USA
standard Microns
12 1700
20 850
30 600
60 250
100 150
200 75
400 38
-23-
-------
Figure 1
Scanning electron micrographs for Combustion Power Corporation sample 20 LP.
A. 200-diameter view of bed material granules
B. 1000-diameter view of broken surfaces of granule showing
crystalline interior
C. 2000-diameter cross-sectional view of granule surface showing
surface layer and crystalline interior
D. 2000-diameter view of crystalline interior of granule
E. 200-diameter view of second stage "ash" particles
F. 1000-diameter view of second stage "ash" granules
-24-
-------
Figure 1A
Figure IB
Figure 1C
Figure ID
Figure IE
Figure 1 F
-25-
-------
Figure 2
Optical photomicrographs for Argonne samples LST-1 and LST-4.
A. 16-diameter view of polished cross sections of LST-1 granules
B. 16-diameter view of polished cross sections of LST-4 granules
-26-
-------
LST-1
Figure 2A
LST-4
Figure 2B
-27-
-------
Figure 3
Scanning electron micrographs for Argonne samples LST-1 and LST-4.
A. 100-diameter view of etched cross section of LST-1 bed granule
B. 200-diameter view of polished cross section of LST-1 granule
C. 200-diameter view of etched cross section shown in (B)
D. 500-diameter view of polished cross section of granule showing
edge of granule
E. 500-diameter view of etched section shown in (D)
-28-
-------
Figure 3A
Sfe
77-1142 208X LST-1 X-SECT
Figure 3B
LST-1 ETCH XSECT
Figure 3C
77-1246 590X LST-4 X-SECT
Figure 3D
Figure 3E
-29-
-------
Figure 4
Optical photomicrographs for Argonne samples CCS-10 and RGL-10.
16-diameter view of polished cross sections of sample CCS-10
granules. Arrows explained in text show edge layering and
reaction zone features.
16-diameter view of polished cross sections of sample RGL-10
granules. Arrows explained in text show edge layering and
reaction zone features.
-30-
-------
CCS-10
Figure 4A
RGL-10
Figure 4B
-31-
-------
Figure 5
Scanning electron micrographs for Argonne samples CCS-10 and RGL-10.
A. 50-diameter view of etched cross sections of CCS-10 granules;
electron probe elemental analysis shown for indicated areas
B. 50-diameter view of etched cross sections of RGL-10 granules;
electron probe elemental analysis shown for indicated areas
-32-
-------
Al, Si
Mg, S, Ca
Figure 58
Al.Si. Fe.Ca
Figure 5A
-33-
-------
Figure 6
Scanning electron micrographs and x-ray maps for Exxon samples 30.1,
30.2, and 32.0.
A. 50-diameter view of cross section of embedded 30.2 granule.
Superimposed trace shows relative concentration of sulfur
in the sample along the line shown.
B. 50-diameter sulfur-atom x-ray map of the view shown in Figure
6A. White dots show concentrations of sulfur in the cross
section.
C. 30-diameter view of the cross sections of embedded 32.0 granules,
D. 30-diameter sulfur-atom x-ray map of the view shown in Figure
6C.
E. 75-diameter view of the cross section of an embedded 30.1
granule. Edge of granule is at left.
F. 75-diameter sulfur-atom x-ray map of the view shown in Figure
6E
-34-
-------
Figure 6A
Figure 6B
Figure 6C
Figure 6D
-•
.--:.
7'r'- j\- *
* <> ' ', /
^ %^p^K
>' - r'^£^^
' . ^ -«^<*a*, -^
"^
>.
,..
76-1701 75X EXXON RUH 38.1
Figure 6E
Figure 6F
-35-
-------
90 r~
CPC 20" LP BED MATERIAL
PARTIAL % RETAINED
_ to w A
9 O O O O
—
3O
60 100 20O
SIEVE FRACTION
4OO
-40O
CPC 20" LP 224 STAGE ASH
o
u
90
40
30
20
10
30
6O IOO 20O
SIEVE FRACTION
4OO
-400
FIGURE 7
-36-
-------
ARGONNE E-11576
PARTIAL % RETAINED
0 5 8 g 5 30
PARTIAL *
068
1
20 30 60 -60
SIEVE FRACTION
FIGURE 8
-37-
-------
ARGONNE LST-I
SOr-
so —
eo
0
c
-
> u
_,
\ SO 60 100 200 -2C
SIEVE FRACTION
ARGONNE LST-4
50
PARTIAL % RETAINED
_ - ra w »
O O O O O
—
to so eo 100
SIEVE FRACTION
ZOO -200
FIGURE 9
-38-
-------
ARGONNE CCS-IO
90
L % RETAINED
« <* *
300
PARTIA
o 5 '
—
1
20 SO 60
SIEVE FRACTION
-60
ARGONNE RGL-IO
601—
g 40
Z
u BO
PARTIAL %
_ to
O O O
—
—
—
—
J
20 30 60 -60
SIEVE FRACTION
FIGURE 10
-39-
-------
SOi-
EXXON 30.1
O 40l
30
20F
101
°0
2O SO 6O 100
SIEVE FRACTION
200
400
-400
501
EXXON 32
a
ui
III
c
40
sol
201
,
12
20 30 60 100 200 400 -400
SIEVE FRACTION
FIGURE II
-40-
-------
o 40
EXXON 30.2
o
UJ
z
u
e
N?
PARTIAL fl
6O
50
40
30
20
10
0
__
—
—
—
1 1
12
20 30 60
SIEVE FRACTION
100
-100
50
EXXON 19.3
u 30
K
_i 20
a. 10
12
20 30 60 100
SIEVE FRACTION
200
400
-400
FIGURE 12
-41-
-------
TECHNICAL REPORT DATA
(Please read Inunctions on the reverse before completing)
I. REPORT NO.
EPA-600/7-78-135
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Characterization of Solid Residues from Fluidized-
bed Combustion Units
5. REPORT DATE
July 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James L. Crowe (TVA/Chattanooga) and
Stephen K. Seale (TVA/Muscle Shoals)
8. PERFORMING ORGANIZATION REPORT NO.
PRS-31
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Power, TVA, Chattanooga TN 37401; and
Office of Agricultural and Chemical Development,
TVA, Muscle Shoals AL 35660
10. PROGRAM ELEMENT NO.
E HE 62 3 A
11. CONTRACT/GRANT NO.
IAG-D7-E721
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
Final; 7/75-6/77
AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES IERL-RTP project officer is D. B. Henschel, Mail Drop 61, 919/
541-2825. TVA project officer is J.L.Crowe.
is. ABSTRACT The repOrt gives results of physical and chemical characterizations of
samples of spent bed material and of fly ash (carryover elutriated from the bed) from
three experimental atmospheric and pressurized fluidized-bed combustion (FBC)
units. It also gives results of characterization of samples of bed material which
had been subjected to sorbent regeneration. In general, it was found that the
granular material consists of three shells or zones. The outer zone., primarily
CaSO4, is 2-25 microns thick; an intermediate zone, CaSO4 and soft-burned CaO,
is 60-150 microns thick; and the third zone, in the center of the particle (for samples
with incomplete sulfation), is primarily original absorbent. Particle size analysis
shows that, in general, CaSO4 and Ca(OH)2 concentration increases as the size of
the particle decreases and that CaCOS is more concentrated in the larger fraction.
The FBC residue was found to stabilize sludges produced by wet lime/limestone
scrubber systems so that they would not soften when contacting water.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Fluidized Bed
Processing
Solids
Residues
Analyzing
Properties
13. DISTRIE
Fly Ash
Sulfation
Sorbents
Sludge
Scrubbers
Calcium Oxides
Calck
Pollution Control
Stationary Sources
Characterization
13B 21B
07C
13H,07A 11G
07D
131
14B 07B
FRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
46
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
-42-
------- |