v>EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
EPA-600/7-78-225
November 1978
Utilization of
Lime/Limestone Waste in
a New Alumina Extraction
Process
Interagency
Energy/Environment
R&D Program Report
-------
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.
-------
EPA-600/7-78-225
November 1978
Utilization of Lime/Limestone
Waste in a New Alumina Extraction
Process
by
E.P. Motley and T.H. Cosgrove
TRW, Inc.
One Space Park
Redondo Beach, California 90278
Contract No. 68-02-2613
Task No. 14
Program Element No. EHE624A
EPA Project Officer: Julian W. Jones
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
111
-------
FOREWORD
Man and his environment must be protected from the adverse effects of
pesticides, radiation, noise, and other forms of pollution, and the unwise
management of solid waste. Efforts to protect the environment require a
focus that recognizes the interplay between the components of our physical
environment—air, water, and land. The Industrial Environmental Research
Laboratory contributes to this multidisciplinary focus through programs
engaged in
t studies on the effects of environmental contaminants
on the biosphere, and
• a search for ways to prevent contamination and to
recycle valuable resources.
This report, prepared by TRW Systems for the Environmental Protection
Agency, Industrial Research Laboratory, Research Triangle Park, North Carolina,
presents the results of a four month study to evaluate a new alumina extrac-
tion process which utilizes as a feedstock lime/limestone waste generated in
the removal of sulfur dioxide (S02) from stack gases of coal burning power
plants. This study includes a base case preliminary process design and
economic evaluation, an applicability evaluation and an investigation of the
critical/cost sensitive areas of the process.
iv
-------
ABSTRACT
This report describes results of a preliminary process design and economic
evaluation of a processing scheme for using lime/limestone scrubbing wastes as
a source of calcium in the extraction of alumina (for use in aluminum produc-
tion) from low grade domestic ores such as clays or coal ash. The other
principal feedstocks for the process are soda ash and coal. The products are
alumina, elemental sulfur and dicalcium silicate, an alternate feedstock in
the manufacturing of port!and cement.
The conceptual plant is located next to a 1000 MW coal burning power plant
which generates more than 1,000,000 tons per year (TRY) of lime/limestone
scrubber wastes. In addition to the scrubber wastes, the process will require,
yearly, 12,000 tons of soda ash, 300,000 tons of clay and 273,000 tons of coal
to produce 70,000 tons of alumina, 156,000 tons of sulfur and 625,000 tons of
dicalcium silicate. Dicalcium silicate can be used to produce 860,000 tons of
Portland cement per year. The required selling price for the alumina produced
at 10 percent discounted cast flow (DCF) would range from $195 to $370 per ton
as a function of sludge removal credit, exclusive of cement manufacture. How-
ever, if this alumina plant were co-located with a 860,000 TRY portland cement
plant selling cement at $50 per ton, the alumina produced would have a range
of selling prices, depending on sludge removal credit, of from $27 to $221 per
ton at 10 percent DCF.
The chemistry of the process is similar to that for the lime-soda-sinter
reaction except that the reaction proceeds in a reducing rather than an
oxidizing atmosphere. The reaction is summarized as follows:
Sludge + Soda + Clay -*• Soluble Sodium Aluminate + Insoluble Dicalcium
Silicate or, 4CaS04 + Na2C03 + Al203'2Si02'2H20 + Reducing Combustion
Gases •*• Na20'Al203 + 2Si02'(2CaO) + H2S + Combustion Gases.
-------
CONTENTS
Page
DISCLAIMER ^
FOREWORD "i
FIGURES v
TABLES • vi
ABSTRACT vii
1. INTRODUCTION 1
2. CONCLUSIONS 3
3. RECOMMENDATIONS 6
4. TECHNICAL DISCUSSION 7
CHARACTERIZATION OF SCRUBBER WASTE 7
BASE CASE PROCESS DESIGN DEVELOPMENT 9
BASE CASE PROCESS CAPITAL AND OPERATING COSTS 25
RAW MATERIAL COST AND PRODUCT VALUE 38
PARAMETRIC EVALUATION OF COST SENSITIVITY 40
REFERENCES 45
APPENDIX A 47
APPENDIX B 4s
v1
-------
FIGURES
Number Pa9e
1 Total Utilization Concept 4
2 Feed Preparation and Sintering Section ^2
3 Dicalcium Silicate Extraction and Recovery Section 13
4 Desilication Section ^
5 Alumina Recovery Section ^5
6 Soda Ash Recovery Section 16
vii
-------
TABLES
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
FGD SCRUBBER SLUDGE CHARACTERISTICS
SINTERING AND REDUCTION ZONES
MATERIALS BALANCES
TOTAL ESTIMATED CAPITAL REQUIREMENTS
TOTAL ESTIMATED CAPITAL REQUIREMENTS
DAILY PLANT UTILITY REQUIREMENTS
FEED PREPARATION AND SINTERING SECTION
EQUIPMENT LIST - MAJOR ITEMS
DICALCIUM SILICATE EXTRACTION & RECOVERY SECTION
EQUIPMENT LIST - MAJOR ITEMS
DESILICATION SECTION EQUIPMENT LIST - MAJOR ITEMS
ALUMINA RECOVERY SECTION EQUIPMENT LIST - MAJOR ITEMS. . . .
SODA ASH RECOVERY SECTION EQUIPMENT LIST - MAJOR ITEMS . . .
ESTIMATED ANNUAL OPERATING COST
ESTIMATED ECONOMICS OF PORTLAND CEMENT MANUFACTURE
ALUMINA SELLING PRICE AND SLUDGE CREDIT AS A FUNCTION
OF PRINCIPAL ECONOMIC FACTORS
Page
8
17
18
26
27
29
30
31
32
33
34
36
37
41
-------
SECTION 1
INTRODUCTION
The first generation of flue gas desulfurization systems is presently
expanding in usage throughout the electrical power industry. These systems
consist primarily of lime or limestone stack gas scrubbers in which the alka-
line earths react with flue gas sulfur dioxide to form calcium sulfates and
sulfites. The reactions transpire in a water slurry (wet scrubber) and produce
large quantities of waste material identified as sludge. The solid portion of
the sludge consists of calcium-sulfur compounds, fly ash, and calcium carbon-
ate. The liquid portion of the sludge contains calcium, chloride and sulfate
ions, and may contain sodium and magnesium ions along with ions of trace
elements primarily from the fly ash. Because of this composition, there is
concern the contamination of natural water supplies may occur through perco-
lation to ground or surface waters in the vicinity of sludge disposal sites.
Thus, alternate methods of treating and/or disposing of scrubber waste sludge
are being studied.
The study presented herein investigates the commercial utilization of
calcium sulfate/sulfite sludge as a coreactant in the extraction of alumina
from an aluminosilicate ore, kaolin clay. The study provides a preliminary
process design and economic evaluation of a hypothetical plant situated in the
southeastern United States which utilizes the sludge output from a 1000 MW
power plant stack gas scrubber. Although alumina is the desired product of
the process, dicalcium silicate, and alternate feedstock in cement manufac-
ture*, is also produced in large quantities in addition to high purity sulfur.
As a result, a process complex which includes a proportionately sized cement
plant has been assessed as the most economically viable arrangement. The
industrial complex is co-located with the electrical power plant.
*
Tricalcium silicate is normally used.
-------
Present alumina production in the United States is based exclusively upon
the Bayer process, or variations thereof, which utilize bauxitic ore feedstocks.
Domestic production of bauxite is approximately 10 percent of consumption with
dependence for the remaining supply centered on the Caribbean area and other
sources external to the United States. Domestic reserves have been estimated
(1965) at 45 MM tons*or 0.8 percent of the total world supply. The annual
U.S. demand for aluminum «etal is expected to be at least 21.2 MM tons of
bauxite by the year 2000. This latter figure is roughly equivalent to 41.4 MM
tons of bauxite ore. The insufficiency of U.S. domestic bauxite reserves is
therefore obvious and a need exists to investigate alternate mineral sources
of aluminum and related processes for the extraction of same. This fact is
compounded by the equally obvious susceptibility to increase that imported
bauxitic ore prices may have in future international markets.
Alternate sources of aluminum exist in abundance within the continental
United States. These sources take the form of large low-grade bauxitic clay
deposits, thin or deeply buried bauxite deposits, low-grade gibbitic bauxite,
low-grade ferruginous bauxite, nonbauxitic clays of the kaolin type, anor-
thosite, dawsonite and alunite. The ultimate source of aluminum is expected
to include a nonbauxitic clay of the kaolin type.
Metric conversions are provided in Appendix A.
-------
SECTION 2
CONCLUSIONS
The results of this study indicate that an alumina extraction process
employing calcium sulfate/sulfite sludge, sodium carbonate and kaolin clay as
coreactants could be commercially feasible* under present economic conditions
provided that the alumina extraction plant includes a cement producing facil-
ity which utilizes the dicalcium silicate by-product from the alumina extrac-
tion process as feedstock. Should bauxite prices escalate, the estimated
selling price for alumina as output from an alumina plant not possessing a
cement facility may become competitive. Each of the above conclusions are
based upon a sulfur credit of $10 per ton and a sludge disposal credit of $5
per wet ton (50 percent solids). These credits are considered conservative.
The process is illustrated in Figure 1. The 10 percent discounted cash flow
(DCF) price for alumina from a lime/limestone sludge utilization facility is
$124 per ton including a sludge disposal credit and sulfur and cement by-product
credits. Without these credits, the price of alumina from this process is
$421 per ton. The current market value of alumina (from bauxite) is $160 per
ton.
Up to 1.4 million tons of sludge per year may be produced by one 1000 MW
generating facility. In the conceived process, this output is effectively
converted into alumina, cement and sulfur. Yearly output from the complex is
approximately 858,000 tons of cement, 70,000 tons of alumina and 156,000 tons
of sulfur. The required alumina selling price for the base case alumina plant,
exclusive of cement manufacture, is $292 per ton at a 10 percent DCF rate of
return. When total utilization of the alumina plant by-products is considered,
* Under the assumption that the chemistry will proceed at satisfactory rates
with a minimum of side reactions. This assumption must be verified at
bench and pilot scale levels.
-------
LIMESTONE
QUARRY
LIMESTONE
POWER PLANT
(1000 MW)
LIMESTONE
375 M
COAL
3,325 M
t
COAL MINE
COAL
228 M
COAL
250 M
SLUDGE (50% SOLIDS)
1,365 M
CLAY STORAGE
CLAY
317 M
CEMENT PLANT
652 M
DICALCIUM SILICATE
ALUMINA PLANT
SODA ASH
12 M
LIME
5 M
PORTLAND
CEMENT
858 M
Figure 1.
ALUMINA
70 M
Total Utilization Concept
(Quantities in tons/yr)
SULFUR
156 M
-------
i.e., cement manufacture with cement sold at $50 per ton, the selling price of
alumina drops to $124 per ton at a 10 percent DCF rate of return and $182 per
ton at a 12 percent DCF rate of return. These latter prices compare favorably
with the present market value of alumina as produced from bauxite of $160 per
ton. In each of the above cases, a sulfur credit of $10 per ton and a sludge
disposal credit of $5 per wet ton (50 percent solids) were assumed.
Alternate means of sludge disposal are available to power utilities.
Depending on the disposal site and applicable regulations, these include
ponding and landfill of both treated and untreated waste. Present cost for
chemical treatment range from $7.50 to $11.40 per wet ton (50 percent solids)1.
Estimates for ponding run slightly lower but do not include disposal site and
reclamation subsequent to pond life. Based on these cost estimates, sludge
credits of $5 to $10 per wet ton are felt to represent complete disposal/
utilization of the waste material, and therefore are used in this study.
The chemical functioning of this process is predicted upon several tech-
nical assumptions (see Recommendations, Section 3). The validity of these
assumptions must be proven via laboratory experimentation before it may be
concluded that the potential for a technically viable extraction process
exists. Other elements of the process not dependent upon the referenced
2 3
assumptions have been demonstrated in earlier work by the Bureau of Mines '
4
and TRW Systems Inc. . Given the laboratory demonstration of the validity of
the process chemistry assumptions, sufficient technical justification will
exist to proceed with a development program. No unusual equipment has been
identified and plant construction can be accomplished with standard items.
-------
SECTION 3
RECOMMENDATIONS
Technical assumptions are implicit in the conceived design. Laboratory
verification of these assumptions is necessary before any developmental work
may proceed. It is recommended that laboratory investigation be conducted to
verify that:
0 the reactions of soda, alumina, calcium and silica to form
dicalcium silicate and sodium aluminate will proceed in a
reducing atmosphere to a high percentage completion;
• the reaction rates are sufficiently fast to be practical;
• side reactions do not occur which inhibit the formation of
soluble sodium aluminate and thus negate the output of
alumina;
• coal can be used to produce a reducing atmosphere in the
proper amounts in this processing scheme;
• the dicalcium silicate by-product possesses the necessary
mechanical properties for compatibility with standard
cement manufacture.
It is additionally recommended that an alternate processing scheme in
which the principal product is cement (tricalcium silicate), be considered.
This latter scheme would use sand and lime/limestone scrubber sludge as primary
feedstocks. Physically, the design of such a process need not extend beyond
grinding of the kiln sinter and hence would require significantly less capital
than the alumina extraction process. Such a process would also be less energy
intensive. Because of the potential for increased economic leverage implied
in this scheme, a preliminary' study for the purpose of assessing technical
viability and quantifying the economic variables is recommended.
-------
SECTION 4
TECHNICAL DISCUSSION
CHARACTERIZATION OF SCRUBBER WASTE
Table 1 presents reported data on sludge composition derived from a number
of flue gas desulfurization (FGD) demonstration scrubbers based on limestone,
lime, and double-alkali scrubbing. As indicated in Table 1, the sludges were
generated from the scrubbing of flue gas (FG) originating from the combustion
of fuels of substantially different sulfur and ash content (columns 2 and 3),
scrubbed under a variety of conditions (columns 5, 6, and 7), and with or with-
out simultaneous ash removal (column 8). The scrubbing system can be either
closed or open loop (column 4). A closed loop system is one in which the only
liquid that leaves the system is that occluded with the solids. Conversely,
an open loop system has a direct liquid discharge. Thus, the sludge com-
positions presented represent a good sample of the spectrum of waste sludges
expected from FGD throwaway processes.
The common components in all FGD waste sludges are calcium sulfite, cal-
cium sulfate, calcium carbonate, and water. Limestone scrubber sludges contain
substantial quantities of unreacted limestone. Double-alkali sludges contain
minor quantities of alkali metal sulfites and sulfates. All these sludge
components influence, at least to a minor extent, the cost of producing alumina
from clays. Ash may or may not have an influence on the cost of the process
depending on its composition.
Alumina production from clays requires calcium and alkali metal oxides as
process feeds in addition to clay. The large concentration of calcium in flue
gas desulfurization waste sludges renders them an attractive feedstock for the
alumina process. The oxidation state of the sulfur is expected to have little
influence on the alumina production process except as it affects the water
content of the slurry. Sulfite is preferable to sulfate because of higher
-------
TABLE 1. FDS SCRUBBER SLUDGE CHARACTERISTICS
00
Facility Coal
Sulfur Ash
Type
Scrubber
Stolchio- pH
metery 1n
Ca/S02 Scrubber
o2/so2
Sludge Composition
. (Dry Basis, Wt. X) Solids
Fly Ash CaSO, CaS04 CaC03, Content
1/2 H20 2H25 or CaO NazS04 1n Sludge
(mole/mole) (mole/ratio) (%) (%) (%)
Kansas City
Power a Light
Hawthorne 4
Commonwea 1 th
Edison, Mill
County 1
City of Key West
Stock Island
Kansas City Power
& Light, LaCygne
Arizona Public
Service Choi la
Shawnee
Shawnee
Louisville Gas
a Electric
Paddy's Run
So. Cal . Edison
Mohave 2
FMC Mobile
Scrubber
GM Parma, Ohio
Chevrolet Plant
Kawasaki /Kureha
Showa Denka
KK/Ebara
Envirotech
Selected Base Case
for Alumina Process
3
3.5
2.0
(oil)
5.3
.5
3.5
3.5
3.7
.4
4.8
2.5
1.2-1.5
(oil)
2.5-3.0
(oil)
.4
3.5
13
15
.04
22
10
12
12
14
16
NA
NA
NA
NA
NA
12
Limestone
Closed Loop
Limestone
Open Loop
Limestone
Open Loop
Limestone
Closed Loop
Limestone
Open Loop
Limestone
Closed Loop
Lime
Closed Loop
Lime
Closed Loop
L1me
Closed Loop
Double
Alkali
Double
Alkali
Double
Alkali
Double
Alkali
Double
Alkali
Lime
Typical ash composition: Silica (S10?)«47
Magnesia (MgO)«.5, Sodium Oxide (Na20>.5,
(P205)=.l.
1.
1.
5.
1.
1
1.
1
1
1
1
1
1
5
.5
,0
9
.0
.2
.0
.0
.0
.05
.5
.0
NA
1.1-1.5
1
.0
, Alumina
Titanium
5.5-4.5
5.9-5.7
7.5-6.5
6.0-5.6
6.5-5.2
7-6
9-5
9.0-5.3
9-5
6-7
9 in
5.5-6 out
6.9-7.3
6.3
7.5-7.7 in
6.5 out
9-5
20
40
30
30
100
30
30
30
300
23
1000
37
NA
33
30
(Al,0,)»25, Ferric Oxide
Dioxide (T102)=l, Sulfur
45
15
1
15
65
37.9
34.7
38.3
42.5
46.9
4
3
21.4
1-2
Low
Low
1-2
2
(Fe20
Triox
17
50
20
40
15
30
33
30
46
23
15
5
15
20
.4 14.5
.1 17.2
.9 16.6
.5 11.8
38.6 14.1
94
2
73
70
2
95
.5
85-73
(CaSOx)
MOO
MOO
87-81
(CaSOx)
23
,)=20, L1me (CaO)=-3
Tde (503)=!, Carbon
(X) (Wt X)
15 M3 40
20 -vO 35
74 i-O 50
30 *JQ 35
0 ^0 50
21.8 •"O 36.5
19.7 ^0 37.2
11.9 'xO 33.3
3.4 ^0 46
3.9 ^0 46
0 ^ 40
0 ^0 65
1.75 1.18 65
10-20 4-5 50
(Ca[OH]2)
<300 ppm 40
<300 ppm NA
10-15 2 60-70
5 *0 46
, Potassium Oxide (K20)«l
(c)=2, Phos Pentoxide
-------
calcium content per unit weight. However, dewatering the sulfite requires more
energy than dewatering the sulfate. Water may have a beneficial effect in the
blending of the process feedstock but it will affect adversely process ener-
getics. Everything else being equal, the presence of alkali metals in the
sludge is highly desirable. Ash may be considered as clay; therefore, its
desirability as a sludge component depends on its alumina concentration.
Although the composition of coal ash is extremely variable, the AlpCU/SiCL
ratio for a typical coal ash is 1/2. This is the same ratio found in kaolin
clays.
It is apparent from the above discussion that selection of a waste sludge
composition as feedstock for alumina production may influence process cost.
Thus, the sludge recommended for use as the feed to the alumina process in the
baseline scheme analysis was that most closely representing the mean composi-
tion of the various sludges presented in Table 1. The lime sludge from the
TVA Shawnee plant fits this criterion. (The selection was partially influenced
by sludge characterization data availability and reliability.)
The sludge composition used as a base-case feed to the alumina process is
that shown in the last row of data in Table 1. The composition of the selected
waste sludge differs from the actual composition of the Shawnee lime sludge
only in ash content. Because ash content and composition varies widely with
fuel and because not all scrubbers utilize simultaneous SO - ash removal, it
J\
was decided that the base case engineering analysis should not include ash
concentrations greater than those found in sludges generated from the SOX
removal of "particulate-free" FG. The ash content of the slurry can then be
treated parametrically as an alumina/silica ratio in the sludge or as a clay
composition variable.
BASE CASE PROCESS DESIGN DEVELOPMENT
This process for utilizing lime/limestone scrubber wastes in the extrac-
tion of alumina from clay is based on the following criteria:
1) Feedstock: Sulfur dioxide wet lime/limestone scrubber wastes
sludge delivered by pipeline from a 1000 MW power plant co-
loscated with the process plant. The feed sludge will contain
50 percent water and 50 percent solids with the following
composition:
9
-------
Sludge Composition, weight percent on dry basis
CaO 40.69
S02 34.72
S03 10.70
C02 2.2
Fixed Water 9.70
Fly Ash 2.0
Kaolin clay (containing 20 percent water) delivered by
rail to the plant site from a local mine.
Clay Composition, weight percent dry basis
A12°3 30
Fe2°3 3
Si02 50
LOI 15
Other
Sodium carbonate delivered by rail from a local supplier
2) Plant location: Southeastern portion of U.S.A.
3) Reactions: The reactions of soda, alumina, calcium and
silica will proceed to 96 percent completion given that
these components exist in the following weight ratios:
CaO/Si02 = 1.8 and Na20/Al203 = 1
4) Steam: Steam for evaporators and autoclaves will be gen-
erated in waste heat boilers on the rotary kilns. Addition-
al steam requirements will be met by combusting kiln off-gases
and coal.
5) Process: Bituminous coal will be delivered by rail or trans-
ferred from a local mine and preparation plant.
Coal Composition
Moisture 1.5
Volatile Matter 26.7
Fixed Carbon 57.9
Ash 13.9
C 72.7
H 4.5
10
-------
0 3.7
N 1.2
S 4.1
H.V. 13010 Btu/lb
6) Water: Plant water requirements are satisfied with water
obtained from the sludge feedstock.
7) Effluents: Anticipated pollution control devices are
included in the design and priced as units.
The plant design parallels the Bureau of Mines (BuMines) lime-soda-sinter
process in which alumina is extracted from clay by sintering with soda ash and
limestone . The sinter is leached using a diluted sodium carbonate solution
to form sodium aluminate solution. This solution is treated with lime to
remove dissolved silica and then carbonated to precipitate alumina trihydrate.
The tri hydrate is calcined to ex-alumina.
The TRW process is an adaptation of the BuMines lime-soda sinter process
in that lime/limestone waste sludge from sulfur dioxide wet scrubber systems,
as used in coal burning power plants, replaces limestone as a major feedstock.
Sulfur and dicalcium silicate are recovered as by-products. The major benefit
derived via the TRW concept is that it permits the processing of sulfur con-
taining feedstocks.
The TRW process for utilization of lime/limestone wastes is separated
into five sections: Feed Processing and Sintering, Dicalcium Silicate Extrac-
tion and Recovery, Desilication, Alumina Recovery and Soda Ash Recovery.
Process flow diagrams for each of these sections are shown in Figures 2
through 6. Material balances are shown in Tables 2 and 3.
Feed Processing and Sintering
In the feed processing and sintering section (Figure 2) raw kaolin clay,
lime/limestone scrubber waste sludge, sodium carbonate solution and recycled
desilication residue are ground and blended in tube mills to prepare a mixture
for sintering. The wet mixture is fed to indirect dryers where 250 psig steam
is used to supply 7,000 MM Btu/D to drive off 6,326,000 Ib/D of water, leaving
11
-------
ro
SPRAY DBJM (1 I) (FIGUK 3)
TO CON06NSATE TANK
Figure 2. Feed Preparation and Sintering Section
-------
FROM A1(OH)3 FIITER
WASHING SOLUTION
(FIGURE 5)
Figure 3. Dicalcium Silicate Extraction and Recovery Section
-------
f«OM AI(OH)3 fllTM WASHING SOLUTION in GUM 9)
PKtSSUtt
Plin« _ HBGNANT SOLUTION
TO MIX TANK _
(FIGUK 3)
TOWETG«NDE«(flGU«E2)
Figure 4. Desilication Section
-------
en
34) TO STACK
O
Figure 5. Alumina Recovery Sections
-------
MULTIPLE EFFECT EVAPORATORS
No,CO, FROM CARBONATED SOLUTION
* 3 THICKENERS SUKGE TANK
(FIGURE 5)
TO CONDF.NSATE TANK
—T* f TO LEACH TANi
>—^ AND WE
IK
D WET
GRINDING
(FIGURE 3)
TO CONDENSATE TANK
Figure 6. Soda Ash Recovery Section
-------
TABLE 2. SINTERING AND REDUCTION ZONES
MATERIAL AND ENERGY BALANCE
Basis: 1 day,
In
Al,0,-2SiO~
£. 3 C
CaC03
Na2C03
CaS04
CaS03
Fe2°3
Si02
NaAl 02
Ash and Other
Coal
Air
Total
Out
Al,0,-2SiO,
23 2
CaO
Na20
Ca2Si04
Fe203
Si02
NaA102
Ash and Other
so2
H2S
CO
co2
H2
H20
N,
Total
Heat loss
TOTAL
Tref.= 25°C
Lbs
860,537
242,940
707,661
709,608
2,539,481
45,340
310,843
225,248
109,030
1,180,481
5,242,803
12,173,971
Lbs
46,648
1,048,749
186,724
867,785
45,340
448,439
825,930
271,935
594,303
633,215
859,740
2,194,680
3,132
111,955
4,035,396
12,173,971
(16%)
HF at 780°C
kcal/gmole
-722.1
-248.4
-237.8
-329.5
-267.2
-167.5
-204.9
-255.8
0.731 at room temperature
Preheated with solid effluents
HF at 1200°C
kcal/gmole
-698.2
-139.4
-112.9
-571.5
-155.3
-198.2
-268.8
- 72.9
- 10.3
- 18.9
- 81.1
+ 7.9
- 49.4
+ 8.4
H MM Btu at
780°C (1436°F)
- 5,035.2
- 1,085.2
- 2,858.4
- 3,091.5
-10,165.6
85.6
- 1,907.6
- 1,265.2
+ 26.5
+ 173.9
+ 1,457.3
-23,836.6
H MM Btu at
1200°C (2192°F)
- 263.9
- 4,693.2
- 612.2
- 5,182.6
79.0
- 2,662.9
- 3,538.4
+ 85.4
- 1,216.6
- 346.1
- 1,045.9
- 7,284.4
+ 22.1
- 552.1
+ 2,165.1
-25,204.7
+ 1,368.1
-23,836.6
17
-------
TABLE 3. MATERIAL BALANCES
CD
Stream No. 1
In M lbs/0
Sludge
Ash, etc. 78
A1203
CaO 1 ,587
Na-0
C02 86
Si02
Fe?°l
H20 4,279
S02 1,354
S03 417
Total 7,801
Coal
Air
Gases
H2S
so2
CO
co2
H,
H?0
N2
Other
Total
23456 7 8 9 10 11 12 13 14 15 16
Recycle Water Drying Pulverized Reduction Sour Cooled Carbonation Stack Sweeten Na2C03
Na.CO, Clay Slurry Vapor Steam Coal Air Off-Gases Gases Sinter Gases Sulfur Gases Qjjes Leachate
30 109 2 277 17
52 453 535 530
1,614 1,598
481 499 494 204
294 401 128
1 756 777 769
45 45 45
1,659 605 6,553 6,326 7,366 (541) 563
1,354
417
2,487 1,889 12,304 6,238 7,366 29 27 4,220 895 912
1,180
5,243
633 633
594 594
860 860 860
2,195 2,195 380 4,088 2,346
3 3 2
112 339 80 481 924
4,035 4,035 622 6,686 4,482
4 37
8,432 8,659 1,085 11,292 8,613
-------
TABLE 3. (CONTINUED)
Stream No. 17
In M Ibs/D Pregnant
Solution
Ash, etc.
A1203 509
CaO
Na20 716
C02 147
Si02 21
H20 4,834
so2
so3
Total 6,227
Coal
Air
Gases
so2
CO
co2
N2
Other
Total
18 19
Thickener Leaching
Underflow Solution
277
241 203
1,613 15
340 357
92 110
753 5
45
2,370 6,100
5,731 6,790
20 21 22 23 24 25
Filter Washing D1 calcium Pregnant Pregnant
Water So1ut1on Silicate Solution Solution Lime
277 1
4 42 51 458
1 ,598 27
51 33 72 644
35 16 15 132
748 2 18 1
45
3,409 1,401 1,080 483 4,351
3,409 1,491 3,839 623 5,603 29
26 27 28 29 30 31
Autoclave Water
Feed Steam Vapor Filtrate Water Si 11 cant
1 1
509 479 30
27 27
716 698 18
147 126 21
21 1 20
4,834 309 254 4,380 120 10
6,255 309 254 5,684 120 128
-------
TABLE 3. (CONTINUED)
Stream No. 32
33
34
35
36
37
38
39
40
41 42
43
44
45
46
47
48
ik./n
IDS/U
Sweetened Alumina Carbonatlon Alumina
Na2C0
Alumina
Caldner Concentration Condensate Makeup
Na7CO,
jirMl .
Gases Seed 6*ses Solution Mater Water Solution Trlhydrate Condensate Steam A1r Coal Al?03 Off-Gases solution
Na2C03
Ash, etc.
A1203
CaO
Na20
coz
S102
Fe2°3
H20
so
115
30
17
273
594
727
446
1
69
644
393
1
4,630 1,053 812 4,399
405
2
1
424
209
274
401
2
1
69
644
393
1
2,222
2,257
41
29
ro
o
Total
Coil
Air
Gases
H2S
soz
CO
co
380
435
77
6,398 1,053 812 5,506
833
209
274
582
404
56
5
151
3,329
2,257
70
H20
N2
°2
Other
Total
80
622
3
1,085
103
622
3
805
238
447
6
8
846
-------
the chemically fixed water in the clay. The remaining 227,000 Ib/D of fixed
water is driven off in the preheaters where 1200°C (2192°F) reduction zone
off-gases are used to supply 1993 MM Btu/D to raise the mixture temperature
to 780°C (1436°F). No sulfur compounds are expected to decompose here. The
mixture is next reacted in an atmosphere produced by burning coal at 1200°C
(2192°F) with less than the stoichiometrically required amount of air. Along
with the reactions associated with the combustion of coal, the following
chemical reactions are assumed to occur:
Al203-2Si02 + 4CaS04 + Na2C03 + SCO + 8H2 £ (1)
2NaA102 + 2Ca2Si04 + 4H2$ + 9C02 + 4H20
Al203'2Si02 + 4CaS03 + Na2C03 + SCO + 4H2 t (2)
2NaA102 + 2Ca2Si04 + 4H2$ + 9C02
Na2C03 £ Na20 + C02 (3)
CaS03 + CO + 2H2 J CaO + H2$ + C02 + H20 (4)
CaS04 + CO + 3H2 Z CaO + H2$ + C02 + 2H20 (5)
CaC03 t CaO + C02 (6)
H2S + 02 J S02 + H2 (7)
H20 + CO t C02 + H2 (8)
2H2 + 02 * 2H20
The amount of air supplied was determined so as to obtain the gaseous products
in the following proportions:
H2S:S02 =2:1
H2:H20 = 1:4
and [C02][H2]
[CO][H20] -
21
-------
If a 2:1 molar ratio of HoS to S02 can be obtained in the kilns, the Claus unit
furnace is not required. The mass and energy balances for the sintering and
reduction kilns are shown in Table 2. The reduction zone off-gases are used
to preheat the solids entering the sintering kiln. In doing so, the gas tem-
perature drops to about 704°C (1300°F). The hot gas is then used to generate
some 1,794,000 Ib/D of 250 psig steam before the temperature is lowered to
232°C (450°F), a temperature at which it can join the 232°C (450°F) gases from
alumina trihydrate calcination in the first Claus converter.
The sulfur plant is a Claus unit, minus a furnace and waste heat boiler,
coupled with a Beavon tail gas plant. The units are sized to produce 400 long
tons per day of sulfur. The steam requirement on the Claus plant is that re-
quired to reheat the gas from the first condenser before it is fed to the second
converter. All the boiler feedwater for this plant is heated to 93°C (200°F)
in cooling coils on the two sulfur condensers of the Claus plant. The sweet-
ened gases are burned in a low Btu boiler which generates 3860 MM Btu of 250
psig steam. A percent of the combustion products is used for carbonation.
Solid products from the reduction zone kiln are cooled to 60°C (140°F) in
preheating the air used for combustion. These solids are then wetted to
facilitate conveyance of the next section.
Several assumptions were made in the feed preparation and sintering
sections, the viability of which can be tested only in a laboratory. The first
assumption was that the hydrogen and carbon monoxide required by the quasi-
sintering reactions, reactions (1) and (2), could be produced by combustion of
coal with less than the stoichiometrically required air in a rotary kiln. The
process may require a coal gasification reactor for some, or all of the coal
required in the reactions. The second assumption was that the proper order
for the reactions was sintering first, bringing the materials to reaction
temperatures, and then reduction to convert most of the sulfur produced to
hydrogen sulfide. It may be that the correct order is just opposite to that
assumed. The third assumption was that the amount of air calculated would
produce a product similar to that from a Claus furnace. It may be that almost
22
-------
all of the sulfur produced in the kilns will be in the form of hydrogen sul-
fide. If so, H-S will be separated from the other gases in an absorption pie
and then converted to sulfur using a traditional Claus process.
Pi calcium Silicate Extraction and Recovery Section
In the dicalcium silicate extraction and recovery section (Figure 3), the
cooled, wet sinter, containing 530,000 Ib/D of alumina, proceeds through a
grinder/rake classifier section to the sodium carbonate leach tanks. A por-
tion of the recovered sodium carbonate solution is added to the grinder and
the remainder is pumped to the 60°C (140°F) sodium carbonate leach tank. The
leach tanks were sized for a 30 minute capacity. The leach tank effluent is
pumped to a thickener where the pregnant solution is separated from the dical-
cium silicate slurry. The thickener has a settling area of 1.7 square feet
per ton of dry solids per day. The pregnant solution, thickener overflow, is
pumped to a filter. The filter residue is added to the dicalcium silicate
product. The filtrate is pumped to the desilication section. A sugar solu-
tion is available for pumping to the thickener in case the solution gels. The
thickener underflow is washed countercurrently in three thickeners. Overflow
from the first thickener is recycled to the leach tank. Overflow from the
second thickener is used as wash solution for the first and overflow from the
third thickener is wash solution for the second. Underflow from the third
thickener is vacuum filtered. The three thickeners have settling areas of
about 3.2, 3.4, and 3.5 square feet per ton of dry solids per day respectively.
Approximately 1,491,000 Ib/D of recovered washing solution from the alumina
trihydrate filter in the alumina recovery section is used as wash solution for
this vacuum filter. Recovered solution is used as wash for the third thick-
ener. The filter residue is 3,843,000 Ib/D of dicalcium silicate product
which is sent to product storage and later to a cement manufacturing plant
where it replaces most of the lime and silica feedstocks.
Desilication Sections
The pregnant solution from the dicalcium silicate recovery section (Figure
4) is divided so that about 10 percent of the stream is used for slaking lime.
The other 90 percent is preheated to 199°C (390°F), mixed with the cool
23
-------
lime containing solution and sent to one of five batch autoclaves to be held at
177°C (350°F) and 100 psig for 2 hours. Most of the silica in solution reacts
to form a precipitate assumed to be 2Na20-2Al203'3Si02-5H20. Six percent of
the alumina and three percent of the soda in solution also precipitate along
with the silica. The slurry from the autoclave is sequentially flashed at
30 psig and then at atmospheric pressure. Approximately 309,000 Ib/D of 30
psig steam is recovered from the first flash vessel. The pregnant solution
is then separated from the desilication residue in a five foot per ton of dry
solids surface area thickener. Underflow from the thickener is washed and
vacuum-filtered. Almost 128,000 Ib/D of filtered desili cation residue is
recycled to the wet grinder in the feed preparation and sintering section of
the plant. Filtrate from the vacuum filter and overflow from the thickener
are pumped through pressure leaf filters to the mix tank in the alumina re-
covery section. Residue from the leaf filters is added to recycled desilica-
tion residue or sent to solids disposal.
Alumina Recovery Section
In the alumina recovery section (Figure 5) flue gases from the calcining
kiln are bubbled into the desilicated solution as it is pumped to the mix
tank. To promote precipitation, 434,391 Ib/D of alumina tri hydrate seed,
about 25 percent of the alumina that precipitates, is added to the mix tank.
The solution is then pumped through three stages of carbonation where flue
gases from the steam generation are used to reduce the solution pH to the
level required for aluminum tri hydrate precipitation. About 86 percent of the
alumina in the desilicated liquor precipitates according to the following
reaction:
Na0-Al0 + C0 + 3H0 + A10-3H0 + NaC0 (10)
2
The slurry from the final stage of carbonation is pumped to hydroclassification
and mechanical classification. Overflow from classification contains aluminum
tri hydrate fines which are recovered in two thickeners and recycled to the mix
tank as seed. Overflow from the fine aluminum tri hydrate thickeners are pump-
ed to a sodium carbonate solution surge drum. Approximately 30 percent of the
sodium carbonate is recycled to hydroclassification. The remaining 5,587,017
24
-------
Ib/D of solution is pumped to the soda ash recovery section. Coarse aluminum
trihydrate is contained in the classifier underflow and is filtered and washed
in drum filters. Twenty-five percent of the filter cake material is free
water which is removed with 250 psig steam in an indirect dryer. The dried
material, 624,238 Ib/D, is calcined at 1093°C (2000°F) to a-alumina. The cal-
cination reaction is shown in equation (11):
A1203-3H20 -* A1203 + 3H20 (11)
the product has the following composition:
A12°3
Na20
co2
Soda Ash Recovery Section
The soda ash recovery section (Figure 6) consists of triple effect evap-
orators. Thickener overflow from the carbonated solution surge tanks is
concentrated in the evaporators. About 75 percent of the evaporator effluent
goes to the feed preparation and sintering section. The remainder is recon-
centrated with makeup soda ash in the mix tank before being pumped to the
dicalcium silicate extraction and recovery section.
BASE CASE PROCESS CAPITAL AND OPERATING COSTS
Presented in this section are estimates of the total plant investment
and annual operating cost requirements for the conceptualized TRW alumina
extraction process. Cost of major processing equipment are itemized by
processing section. The related economics for portland cement manufacture
are presented in this section. All costs are quoted at a Marshall and Stevens
index of 444.3, the annual index for 1975. Raw materials and land costs are
not included in the investment estimates.
Two differing methods of plant investment and capital cost estimation are
represented in Tables 4 and 5. The method illustrated in Table 4 has been
25
-------
TABLE 4. TOTAL ESTIMATED CAPITAL REQUIREMENTS*
(BuMines Method)
Millions $
Feed Preparation & Sintering 24
Dicalcium Silicate Extraction 2
Desilication 1
Alumina Recovery 4
Soda Ash Recovery 0.2
Pumps @ 4% of above 1
Total Installed Equipment Cost 32.2
Steam Plant 0.3
Subtotal 32.5
Plant Facilities, 10% of Subtotal 3
Plant Utilities, 12% of Subtotal 4
Total Construction 39.5
Initial Catalyst Requirement §
Total Plant Cost 39.5
Interest During Construction 7
Subtotal for Depreciation 46.5
Working Capital 5
Total Investment 51.5
BuMines Format
f Includes Sulfur Recovery Plant
5 Included in Sulfur Recovery Plant
26
-------
TABLE 5. TOTAL ESTIMATED CAPITAL REQUIREMENTS*
(TVA Method)
Millions $
Feed Preparation & Sintering 24
Dicalcium Silicate Extraction 2
Desilication 1
Alumina Recovery 4
Soda Ash Recovery 0.2
Pumps 1
Total Installed Equipment Cost 32.2
Steam Plant 0.3
Subtotal 32.5
Plant Facilities I c
-------
used by BuMines in all investigations of alumina extraction processes to date
and is of the general type called "study estimate" . This "study estimate"
technique has been used herein so that comparisons may be made with BuMines
figures. A more conventional method of presenting capital estimates is shown
in Table 57. As may be observed, the latter method results in an approximate
0.2 percent increase. The impact of this increase upon alumina selling prices
and sludge credits is insignificant (see discussion of raw material and product
value).
Table 6 presents the utility requirements for steam, coal and water.
Cost estimates for utilities and facilities, Table 4, are taken as 12 percent
and 10 percent of the total physical cost, respectively. These percentages
are based upon a plant complexity level of four as delineated in the Oil and
Gas Journal cost estimating methodology, 22 July 1974. Included under plant
utilities are fire protection equipment, refrigeration, gas, power and water
distribution, etc. Plant facilities include administration buildings, ware-
houses, shops, laboratories, etc. Utility and facility costs as shown in
Table 5 are taken as five percent of the direct investment subtotal.
The sulfur removal plant consists of a combination of Claus and Beavon
units. The cost quoted in Table 7 is for both units and is based upon a
daily production of 382 long tons of sulfur. Tables 8 through 11 summarize
the individual equipment costs for the other various process sections.
Working capital as shown in Table 4 is taken as 10 percent of the total
plant cost plus interest during construction. Interest during construction is
calculated as the product of interest rate, total plant cost and construction
time. Interest rate is taken as nine percent and construction time as two
years. The total plant investment, so calculated, is $51.5 million.
The working capital of Table 5 is calculated as the equivalent of: three
weeks, raw material; seven weeks, direct cost; and seven weeks, overhead.
Interest during construction is calculated over the construction period at
eight percent with 75/25 debt-to-equity ratio. Total plant investment via this
method is $52.5 million.
28
-------
TABLE 6. DAILY PLANT UTILITY REQUIREMENTS
ro
to
250 psig Steam
Feed Preparation and Sintering Consumed Produced
Section
Dryers 7366
Preheaters
Kilns 1794
Claus Converters and Condensers 205
Beavon
01 calcium Silicate Extraction and
Recovery Section
Steam tracing on pipes,
filters, tanks, etc.
Desili cation Section
Heat Exchangers
Autoclaves 946
Alumina Recovery Section
C02 Bubblers
Dryers 275
Calciners 419
Soda Ash Recovery
Evaporator, three effect
Steam Generator* 6579
Theoretical Totals 8792 8792
Steam, M Ibs u.,»- u.,* Plant Cooling
waste neat Water Water
100 pslg Steam 30 psig Steam 5 psig Steam MM Btu/D M Lb/D M Lb/D
Consumed Produced Consumed Produced Consumed Produced Consumed Produced
4300
1993 1993 227
-541
6886
239 -398
138
-3409
309
254
325 309 1ZO
-1866
inc. 209
1328 2257
1328
1328 1328 325 549 138 0 1993 1993 1224 6886
c , Electric
Power
MM Btu/D kwhr/hr
15358
332.5
49.9
713
4249
20320 382.4
The 6,215,000 Ibs of 250 pslg steam 1s generated by combustion of reduction zone off gases, 3,797,000 Ibs,
The steam 1s generated at 250 pslg and reduced to the pressures required.
and by combustion of coal, 2,418,000 Ibs.
-------
OJ
TABLE 7. FEED PREPARATION AND SINTERING SECTION
EQUIPMENT LIST - MAJOR ITEMS
Item
Sludge Storage Bin
Sludge Surge Bin
Clay Silo
Clay Feed Hopper
Conveyors
Tube Mills
Dryer
Kilns - Preheat, Sinter
& Reduction
Kilns - Drum Cooler Conveyor
Rotary Drum Coolers
Beavon Plant
Claus Plant*
Total -
as Purchased
installed
No.
1
1
1
1
4
8
2
6
2
2
1
1
Cost
$ 176,000
28,000
86,000
1,000
84,000
1,540,000
395,000
5,046,000
35,000
450,000
4,988,000
3,640,000
16,469,000
24,209,000
*
Unit Dimension
643,000
96,000
188,000
28,000
100'x24"(l),
10'
24,500
399
gallons
gallons
gallons
gallons
30'xl8"(D> 60'xl8"(2)
x 18'
ft2
Long Tons S/day
Where dimensions are not given, costs are based on BuMines estimates.
Does not include waste heat boiler or incinerator.
-------
TABLE 8. DICALCIUM SILICATE EXTRACTION AND
RECOVERY SECTION
EQUIPMENT LIST - MAJOR ITEMS
Items
Tube Mills
Rake Classifiers
Leach Tanks
Thickener No. 1
Thickener No. 2
Thickener No. 3
Thickener No. 4
Sugar Silo & Mix
Tank
Rotary Vacuum
Filters
Conveyors (screw)
Total -
as Purchased
installed
No.
2
2
2
1
1
1
1
2
2
Cost Unit Dimension
$ 385,000
41 ,000
13,000 12,000 gallons
3,800 ft2
296,000 6'2°° ftl
6,500 ft*
6,800 ft2
25,000
128,000
24,000 60' x 12"
912,000
1,881,000
Where dimensions are not given, costs are based on BuMines estimates,
31
-------
TABLE 9. DESILICATION SECTION
EQUIPMENT LIST - MAJOR ITEMS
Items
Lime Slaking Storage Bin
Lime Slaker & Feeder
Autoclaves
Flash Tanks
Thickener
Rotary Vacuum Filter
Pressure Leaf Filter
Screw Conveyors
Totals -
as Purchased
installed
No.
1
1
5
2
1
2
2
2
Cost
$ 4,000
5,000
535,000
11,000
16,000
38,000
38,000
37,000
684,000
1,253,000
Unit Dimension
3,600 gallons
10,000 gallons
8,500 gallons
300 ft2
100' x 12"
Where dimensions are not given, costs are based on BuMines estimates.
32
-------
TABLE 10. ALUMINA RECOVERY SECTION
EQUIPMENT LISTS - MAJOR ITEMS
Items
A1(OH)? Seed Tank &
Agitator
Carbonators
Hydroclassifier
Rake Classifier
Thickener
Surge Drum
Mix Tank
(pre-carbonation)
Screw Conveyor
Dryer (A1203'3H20)
Kiln (calcination)
Indirect Rotary Cooler
Combustion Gas Scrubber
Cyclone
Rotary Vacuum Filter
Totals -
as Purchased
installed
No.
1
3
1
1
1
1
1
1
1
1
1
1
2
1
Cost Unit Dimension
$ 8,000 6,700 gallons,
10 H.P.
48,000 100,000 gallons
15,000
11,000
62,000
11,000 20,000 gallons
13,000 25,000 gallons
9,000 30' x 14"
100,000
1,088,000
296,000
442,000
13,000
49,000
2,165,000
3,565,000
Where dimensions are not given, costs are based on BuMines
estimates.
33
-------
TABLE 11. SODA ASH RECOVERY SECTION
EQUIPMENT LIST - MAJOR ITEMS
Items No.
Na2C03 Mix Tank 1
Na2C03 Surge Tank 1
Triple Effect Evaporator - 1
Stage 1
Stage 2
Stage 3
Total -
as Purchased
installed
Cost
$ 61,000
38,000
3,000
4,000
4,000
110,000
228,000
Unit Dimension
87,000 gallons
32,800 gallons
2,000 gallons
2,800 gallons
4,000 gallons
Where dimensions are not given, costs are based on BuMines estimates.
34
-------
Purchased equipment costs are estimated from various textbook sources
including a detailed BuMines analysis of the lime-soda-sinter process for the
3
extraction of alumina from kaolin clay . In particular, the ratios necessary
to compute installed versus purchased equipment costs for the various process
sections are taken from this reference which closely parallels the TRW process.
Installed equipment costs reflect charges for foundations, buildings, and
structures, insulation, instrumentation, electrical, piping, painting and
miscellaneous fixtures.
The operating costs presented in Table 12 also follow a BuMines format.
Estimates of capital investment and operating expense for a cement plant
producing 858,000 tons per year (350 days) are itemized in Table 13. These
costs are updated from a previous TRW publication .
35
-------
TABLE 12. ESTIMATED ANNUAL OPERATING COST
Direct Cost:
Raw Materials:
Lime at $35/ton
Coal at $20/ton
Clay at $ 6/ton
Soda ash at $47/ton
Total
Utilities:
Fuel gas at $2.00/MM Btu
Electric power at 4 cents/KW-hr
Water, Beavon plant, at 20 cents/M gal
Total
Direct Labor:
Labor at $6.00/hr
Supervision, 15 pet of labor
Total
Plant Maintenance
Labor at $15,000/yr
Supervision, 20 pet of labor
Materials and Contracts
Total
Payroll Overhead
Operating Supplies
Total Direct Cost
Indirect, overhead
Fixed Costs:
Taxes, Insurances
Depreciation
Total, before credits
Credits:
Dicalcium Silicate @ $1.00/ton
Sulfur P $10.00/ton
Sludge removal @ $5.00/ton
Total Operating Cost
Annual
Cost
(Thousands)
$ 173
5,466
1,905
576
8,120
175
1,599
14
1,787
842
126
968
705
141
1,058
1,094
544
381
13,703
1,301
759
2,349
18,112
652
1,563
6,825
$ 9,072
Cost per
Ton
Alumina
$ 2.46
77.90
27.14
8.20
115.70
2.49
22.78
.20
25.47
12.00
1.80
13.80
10.50
2.01
15.07
27.13
7.76
5.42
195.25
18.54
10.82
33.45
258.07
9.30
22.27
97.26
129.24
36
-------
TABLE 13. ESTIMATED ECONOMICS OF PORTLAND
CEMENT MANUFACTURE*
Installed Capital Investment (4.5 MM bbl/yr) $ 35.2 MM
Operating Costs (annual) Thousands $
Direct Costs
Limestone ($6/ton) 2,247
Dicalcium Silicate ($l/ton) 652
Gypsum ($10.00/ton) 456
Coal ($2.00/MM Btu) 11,992
Electrical Energy ($0.04/KWh) 1,030
Water ($0.08/gal) 46
Operating Labor 867
Supervision and Benefits 867
Maintenance and Supplies (4% of Invest./yr) 1,094
Total Direct Costs 19,251
Indirect Costs
Depreciation (5%/yr) 1,369
Interest (at 7%, 20% debt) 411
Insurance and Local Taxes 821
Overhead 1,049
Total Indirect Costs 3,650
Total Manufacturing Cost $22,901
*
Wet process plant
f 28 men/shift
37
-------
RAW MATERIAL COST AND PRODUCT VALUE
The present market price for alumina, as quoted in the Chemical Marketing
Reporter for 26 July 1976, is $158 per ton. Because aluminum is the most
abundant metallic element in the earth's crust, has universal application in
production, and is the object of intense efforts on behalf of the aluminum
industry to expand and develop markets, this commodity will continue to
maintain its value and be a major growth metal for many years. Average annual
Q
growth rate for demand is estimated to be in the range of 5.1 to 7.4 percent
through the year 2000. This range corresponds to a U.S. demand in the year
2000 of from 21.2 to 42.0 million tons. These'values may be compared with
the actual 1968 demand of 4.31 million tons.
Nonmetallic usage of alumina is minimal at approximately 11 percent of total
usage and is principally in the areas of refractories, chemicals and abrasives.
The metallic uses are outlined as shown in the following:
Metallic Uses of Aluminum
Area Percentage
Construction 24.6
Transportation 17.2
Electrical 11.8
Cans & Containers 14.1
Appliances 8.6
Machinery 5.7
Other 6.6
88.6
Approximately 80 percent of the free world productive capacity for bauxite,
alumina and aluminum is concentrated in six corporate groups or subsidiaries.
These include one Canadian company, Alcan Aluminum Ltd.; three U.S. companies,
ALCOA, Reynolds and Kaiser; and two French firms, Pechina, and Ugine. All
companies are Integrated In that they encompass the manufacturing process from
mining of bauxite to finished aluminum products.
A conservative value of $10 per ton was used in base case assessments for
sulfur by-product credit. Assessment of present market values for crude
bright sulfur shows a range of $60 to $66 per ton. This commodity is subject
38
-------
Q
to rapid fluctuation; however, a continued strong demand is projected . Lime-
sulfur sludges are recognized as a tremendous reservoir of sulfur which is not
significantly tapped at present. Sulfur during 1975 production totaled 10
million long tons, 76 percent of which was Frasch sulfur. The remaining
production was from sour gas. Sulfur is currently in a somewhat short supply.
Principal usage of sulfur is in the following areas:
Area Percent
Sulfuric Acid Manuf. 80
Pulp and Paper 5
Carbon Disulfide 2.5
Agriculture 1
Other 3.5
Major suppliers of sulfur as produced via the Frasch process are identified as
follows:
Atlantic Richfield Co., Fort Stockton, Texas
Freeport Minerals Co., Chauvin, La.; Grand Isle, La;
Port Sulphus, La.; Venice, La.
Occidental Chemical Co., Long Point Dome, Texas
Texasgulf, Inc., Beaumont, Texas; Bullycamp Dome, La.;
Hampshire, Texas; Liberty, Texas; Newgulf, Texas
Refinery or natural gas producers are numerous. Therefore it is not expected that
sulfur from FGD would have a significant influence upon market prices.
Dicalcium silicate, as produced in this process, has no established market.
This material is an ideal feedstock for cement manufacture. Preliminary esti-
mates are on the order of $1-2 per ton. A $1.0 per ton estimate was used in
this assessment.
Clay feedstock will vary in price depending on locale and whether or not
the material is self-mined, or contracted out and the type of mining required.
Published market prices for refined kaolin clay do not apply to the raw
material as mined and used in this process. A conservative range would be $4
to $8 per ton. A $6 per ton cost was used in this analysis, however, the
price could conceivably be as low as $3 per ton. Sodium carbonate (Soda Ash)
was taken at present market value, $47 - $49 per ton. In large quantities,
39
-------
such as employed in this process, a contracted value may be significantly lower.
Coal costs are somewhat volatile and subject to negotiation. Many present
power facility contracts are based on coal prices in the $30 per ton range.
However, these prices for a number of facilities were negotiated at a time of
energy panic and will probably drop again. National Coal Association figures
from the 1974 edition of Steam Electric Plant Factors indicate an approximate
range for the Georgia region, as burned, at $9.07 - $11.46 per ton. Under
inflation, this range would be $12.14 - $15.34 per ton in 1976. Coal prices
are subject to quantity and negotiation. As such, it is difficult to fix a
future price. For the purposes of this analysis $20 per ton was chosen.
PARAMETRIC EVALUATION OF COST SENSITIVITY
Alumina selling price is a function of several primary cost factors in-
cluding raw material feedstocks, by-product credits, energy requirements,
capital investment and total operating costs. In addition, the rate of return
on investment is a determining factor. These relationships are characterized
by the set of linear equations illustrated in Appendix B which relate the
various economic variables at several discounted cash flow (DCF) rates. This
evaluation consists of alternate cases in which alumina selling price and
sludge credit are taken as dependent variables for the equations noted. In
each specific case a different set of primary cost factors is postulated and
either alumina selling price or sludge credit are calculated to match in-
vestment return rates of 10, 12 and 15 pet. discounted cash flow. In all
cases where sludge credit (a negative expense) is defined as the independent
variable, alumina price is fixed at $150 per ton. In cases where alumina
selling price is the independent variable, sludge credit is fixed at $5 per
wet ton (2000 Ibs) or varied to assess the impact upon alumina price for a
given set of cost factors. A utility financing value for selling price or
credit based upon a 75/25 equity-to-debt ratio and an income tax rate of 48
percent is also included for each case. Table 14 presents the results of this
analysis and series to illustrate the methodology.
Of primary interest are cases 13 and 14 in which the capital and opera-
ting costs for a combined cement and alumina plant are considered. The
alumina selling price calculated for a $5 per ton sludge credit is $124 per
40
-------
TABLE 14. ALUMINA SELLING PRICE AND SLUDGE CREDIT AS A
FUNCTION OF PRINCIPAL ECONOMIC FACTORS
c
a
s
e
1
Base Case
2
3
4
5
6
7
Coal
Cost
$20
20
10
20
25
40
20
20
20
20
*
t
i
Clay
Cost
$ 6
6
6
6
6
1
6
10
1
6
10
Alumina
Before
Units:
Cost
$47
47
47
47
47
47
47
Capital
Cost*
$52 MM
52 MM
52 MM
52 MM
X 0.5
X 1.5
52 MM
X 0.5
X 1.5
52 MM
52 MM
Basis
Capital Sludge
Cost Credit
Cement (wet
Plant basis)
$ 1
5
10
-
.
.
5
5
.
for Price Estimation
Sludge
Mater
Content
50%
50%
50%
50%
50%
50%
50%
Alumina Dicalcium Cement Sulfur A^um1"a CSI"n!
SiHratp riant riant
Credit r,l,;f: Credit Credit Operating Operating
CredU Costs* Costs
$1 - $10 $18 MM
150 1 - 10 18 MM
150 1 - 10 15 MM
18 MM
19 MM
24 MM
150 1 - 10 18 MM
1 - 10 18 MM
1 - 10 16 MM
18 MM
150 1 - 10 16 MM
18 MM
Estimated Price
Utility Financing
Alumina
Selling
Price
$297
218
122
218
175
264
197
218
238
Sludge
Credit
$ 8.57
6.59
8.57
9.59
12.60
8.57
6.29
10.85
7.41
8.57
9.50
10%
Alumina
Selling
Price
$370
292
195
292
193
392
270
292
310
OCF
Sludge
Credit
$12.32
10.34
12.32
13.34
16.34
12.32
7.21
17.43
11.16
12.32
13.18
of Alumina or Sludge
12%
Alumina
Selling
Price
$404
327
229
327
210
444
304
327
345
OCF
Sludge
Credit
$14.08
12.10
14.08
15.10
18.11
14.08
8.08
20.08
12.92
14.08
15.01
15%
Alumina
Selling
Price
$461
383
286
383
237
529
360
383
401
OCF
Sludge
Credit
$16.99
15.00
16.99
18.01
21.01
16.99
9.49
24.48
15.82
16.99
17.92
+ Sulfur Plant
credits
$/ton
, includes
(2000 Ibs)
sulfur plant
-------
TABLE 14. (CONTINUED)
ro
J Coal Clay Na2C03 Capita) C^{"
s Cost Cost Cost Cost Cement
8 20 6 47 51 MM
52 MM
54 MM
g 20 6 47 $51 MM
52 MM
54 MM
10 20 6 47 52 MM
11 20 6 47 52 MM
12 20 6 47 52 MM
13 20 6 47 52 MM 35 Mf
14 20 6 47 52 MM 35 H
Basis
Sludge
Credit
(we
basis)
9
5
2.50
.
5
_
5
H 0
5
10
N
for Price Estimation
Sludge Alumina Dlcaktum Cement
Water /v«j4f Silicate rr«Niu
Content LrMlt Credit LrMU
10'! - 1
501.
75*
lOt 150 1
50*.
751
50* - 1
50% 150 1
50T - 1
50* - 1 50
507 150 1 50
Sulfur
Credit
10
10
0
10
25
0
10
25
10
10
10
Alumina Cement
Plant Plant
Operating Operating
Costs' Costs
15 m
18 MM
20 MM
18 MM
18 MM
18 MM
18 MM
X 1.6 »
X 0.6
18 MM 23 MM
18 1* 23 MM
Utility
Alumina
Selling
Price
$201
218
256
242
218
186
218
348
116
91
N.A
N.A
Financing
1 Sludge
Credit
($15.83
{ 17.14
( 21.04
9.72
8,57
6.85
N.4.
Estimatsd Price
10« DCF
Alumina Sludge
Selling . ..
Price
$271
292
332
$22.66
24.64
28.96
315
292
259
13.46
12.32
10.60
292
421
189
221
124
27
3.44
of Alumina or Sludge
121!
Alumina
Selling
Price
$304
327
367
349
327
293
327
456
223
279
182
85
OCF
Sludge
Credit
$26.14
28.16
32.64
15.23
14.08
12.37
6.39
151
Alumina
Selling
Price
$360
383
426
405
383
350
383
512
280
369
272
174
OCF
Sludge
Credit
$31 .82f
33.98}
38.68*
18.13
16.99
15.27
11.25
Alumina * Sulfur Plant
+ Before credits, includes sulfur plant
1 Units: $/ton (2000 Ibs)
" Sludge crtdU, dry b««1»
* Non-Mtwlil optr»Hng cotti «r« v«r1nl by *50% and
-------
ton (10% DCF) and the sludge credit determined for a fixed alumina price of
$150 per ton is $3.44 per ton (10% DCF). These values are to be compared with
a base case value unattached alumina plant (Case 1), of $292 per ton for
alumina and a corresponding credit for sludge, alumina price fixed, of $12.32
per ton (Case 2). A clear economic advantage rests with the combined cement-
alumina complex. Case 13 also shows that for the combined plant, at a 12
percent DCF return rate, the alumina selling price escalates to no more than
$182 per ton. This latter value compares favorably with the present market
value of $160 per ton.
In all cases the utility supplying the sludge is being charged on a wet
basis of zero to $10 per ton of wet sludge. Should a dry basis be employed,
to accommodate variability in moisture percentage, the sludge credit would
necessarily rise. However, the impact upon process economics may be slight.
In the base case chosen for this report, a 50 percent solids - 50 percent
water sludge is used. The sludge credit employed is $5 per ton on a wet basis.
Should a dry basis be considered, the quantity of sludge upon which revenue is
credited would be decreased by 50 percent. This, in turn, would decrease the
total sludge credit by 50 percent if the $5 per ton price were maintained. It
becomes necessary, therefore to increase the sludge credit per dry ton to
compensate for loss of revenue. A $10 per dry ton credit is still competitive
with alternate sludge disposal methods. If this value is chosen, the loss of
revenue from switching to a dry basis is exactly compensated for and the total
sludge revenue remains the same. Thus, the method upon which sludge credit is
determined need not have a significant effect as illustrated in this base case.
Sludge credits shown in Table 14 may be multiplied by a factor of two to obtain
the required credit on a dry solids basis.
Variations in sludge water content do affect energy requirements and, hence,
product selling price. The impact of differing water content is shown in Cases
8 and 9. Cost factors were selected to illustrate the economics of using this
process as opposed to a throw away process for sludge. In Case 8, a constant
annual sludge credit of $6,825,000 was assumed. This essentially sets the values
of the 75 percent, 50 percent and 10 percent moisture sludges at $2.50, $5.00
and $9.00 per wet ton, respectively and correspondingly decreases the selling
43
-------
price of alumina. In Case 9, the alumina price was fixed at $150/ton and the
corresponding dry sludge credit was calculated.
Alumina prices as determined in the bulk of solo alumina plant cases are
high relative to present market values. However, in certain cases, such as
the $10 per ton sludge credit of Case 1 at 10 percent DCF, the calculated
alumina selling price of $195 per ton is not infeasible with respect to
possible rising bauxite prices.
The impact of coal cost is shown with respect to sludge credit in Case 3.
As may be observed, increases in coal cost have a profound effect upon the
sludge credit required to maintain a $150 per ton selling price for alumina.
Considered from the extreme standpoint of a coal cost of $40 per ton and a
fixed sludge credit of $5 per ton, an alumina price of $468 is required at 12
percent DCF. Alumina prices and related sludge credits are highly sensitive
to coal costs in this energy intensive process. This fact may be compensated
to a large extent by increases in sulfur credit. In the cases discussed above,
a sulfur credit of $10 per ton was assumed. This value is conservative with
respect to present market values in excess of $60 per ton. Cases 10 and 11
illustrate the relation between sulfur credit and alumina selling price-sludge
credit. An increase from $10 per ton to $25 per ton sulfur credit will
produce a 11 percent reduction in alumina selling price at 10 percent DCF.
The remaining raw material input, clay and Na2C03, have been priced at
$6 per ton and $47 per ton, respectively. These are conservative values.
Clay may be mined at less cost than used in the base case, should a continguous
mine be possible. The effect of reduced clay cost was determined in Cases 6
and 7. Sodium carbonate was set at the present market value F.O.B. This
latter factor was not varied although some reduction in cost may be feasible.
44
-------
REFERENCES
1. Rossoff, J. and R.C. Rossi, Disposal of By-Products from Non-Regenerable
Flue Gas Desulfurization Systems, Vol. I. EPA-650/2-74-037, Aerospace
Corp. El Segundo, Calif. 1974.
2. Cservenyak, F.J. Recovery of Alumina from Kaolin by the Lime-Soda Sinter
Process. R. I. 4069, U.S. Dept. of the Interior - Bureau of Mines,
College Park, Maryland, 1947. 59 pp.
3. Peters, F.A., P.M. Johnson, J.J. Henn, and D.C. Kirby. Methods for
Producing Alumina from Clay. R. I. 6927, U.S. Dept. of the Interior -
Bureau of Mines, College Park, Maryland, 1966. 38 pp.
4. TRW Systems Group, Inc. Proposal for the Development of a New Process
for the Economic Utilization of the Solid Waste Effluent from Limestone
Slurry Wet Scrubber Systems. Proposal No. 27359.000. 1974. Two
volumes, 112 pp.
5. TRW Systems Group, Inc. Engineering and Cost Effectiveness Study of
Fluoride Emissions Control, Vol. I. SN 16893.000. McLean, Virginia.
1972.
6. Peters, F.A. and P.W. Johnson. Revised and Updated Cost Estimates for
Producing Alumina from Domestic Raw Materials. 1C 8648. Bureau of
Mines, College Park, Maryland, 1974. 51 pp.
7. McGlamery, G.G., et. al. Detailed Cost Estimates for Advanced Effluent
Desulfurization Processes. EPA-600/2-75-006, Tennessee Valley Authority,
Muscle Shoals, Alabama. 1975. 418 pp.
45
-------
8. Bureau of Mines Staff. Mineral Facts and Figures, BuMines Bulletin 650,
U.S. Government Printing Office, 1970. 1291 pp.
9. Lowenheim, F.A. and M.K. Moran. Industrial Chemicals, Fourth Edition.
Wiley-Interscience. 1975. 904 pp.
-------
APPENDIX A
GENERAL CONVERSION FACTORS
British
Metric
ac
bbl
Btu
°F
ft
ft2
ft3
ft/min
ft3/min
gal
gpm
gr
gr/ft3
hp
in
Ib
lb/ft3
Ib/hr
mi
rpm
scfm
ton
ton .long
ton/hr
Multiply By
acre 0.405
barrels of oil 158.97
British Thermal Unit 252
degrees Fahrenheit-32 0.5555
feet 30.48
square feet 0.0929
cubic feet 0.02832
feet per minute 0.508
cubic feet per minute 0.000472
gallons 3.785
gallons per minute 0.06308
grains (troy) 0.0648
grains per cubic foot 2.288
horsepower 0.7457
inches 2.54
pounds 0.4536
pounds per cubic foot 16.02
pounds per hour 0.126
miles 1609.
revolutions per minute 0.1047
standard cubic feet
per minute (32°F) 1.695
tons (short)* 0.90718
tons (long)* 1.016
tons per hour 0.252
To Obtain
hectare
liters
gram-calories
degrees Centigrade
centimeters
square meters
cubic meters
centimeters per second
cubic meters per second
liters
liters per second
grams
grams per cubic meters
kilowatts
centimeters
kilograms
kilograms per cubic meter
grams per second
meters
radians per second
normal cubic meters
per hour (0°C)
metric tons
metric tons
kilograms per second
ha
1
g-cal
°C
cm
m2
m3
cm/sec
m3/sec
1
I/sec
9
g/m3
kW
cm
kg
Kg/m3
g/sec
m
rad/sec
Nm3/hr
t
t
kg/sec
All tons, including tons of sulfur, are expressed in short tons in this report.
-------
APPENDIX B
ECONOMICS MODELS - REVENUE REQUIREMENTS
Utility*: R = N + .1198C + .01981W
10% DCF1": (.52[R-(N+D)]+D) 8.51356 = C - .14864W + .1875 (C-W)
12% DCFf: (.52[R-(N+D)]+D) 7.46944 = C - .10367W + .225 (C-W)
15% DCFf: (.52[R-(N+D)]+D) 6.25933 = C - .0611W + .281 (C-W)
where: R = Revenue required at indicated level of return
N = Net operating cost - $9,000,000
W = Working capital - $5,000,000
C = Total capital requirement (including working capital)
- $52,000,000
D = Annual depreciation (5% of fixed capital) - $2,300,000
Utility financing assumes:
0 debt/equity ratio = 75/25
• interest on debt = 9%
• return on equity = 15%
• income tax rate = 48%
Discounted cash flow financing assumes:
t income tax rate = 48%
t DCF return rates as indicated above
48
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-78-225
2.
4. TITLE AND SUBTITLE
Utilization of Lime/Limestone Waste in a New
Alumina Extraction Process
7. AUTHOR(S)
E. P. Motley and T.H.Cosgrove
9. PERFORMING ORGANIZATION NAME At
TRW, Inc.
One Space Park
Redondo Beach, California
JO ADDRESS
90278
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
November 1978
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
68-02-2613, Task 14
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 4-9/78
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES JERL_RTpprojectofficer jg Julian W. JonCS , MD- 61 , 919/541-
2489.
IB. ABSTRACT rpke repOrj- gjves results of Si preliminary process design and economic
evaluation of a process for using lime /limes tone scrubbing wastes as a source of
calcium in the extraction of alumina (for use in aluminum production) from low grade
domestic ores such as clays and coal ash. The other principal process feedstocks
are soda ash and coal. The products are alumina, elemental sulfur, and dicalcium
silicate, an alternate feedstock in the manufacture of portland cement. The concep-
tual plant is located next to a 1000 MW coal-burning power plant which generates
> 1 million tons per year (tpy) of lime/limestone scrubber wastes. The required
selling price for the alumina produced at 10% discounted cash flow would be $195-370
per ton, depending on the credit for sludge removal, exclusive of cement manufac-
ture. If the alumina plant were co-located with an 860,000 tpy portland cement plant
selling cement at $50 per ton, the required alumina selling price would be $27-221
per ton. Based on the current market price for alumina (£160 per ton), the portland
cement plant appears to be necessary to make the process viable. In addition to the
scrubber wastes, the process requires 12,000 tpy of soda ash, 300,000 tpy of clay,
and 273,000 tpy of coal to produce 70,000 tpy of alumina, 156,000 tpy of sulfur, and
625,000 tpy of dicalcium silicate (used to produce 860,000 tpy of portland cement).
17.
a. DESCRIPTORS
KEY WORDS AND DOCUMENT ANALYSIS
b.lDENTIFIERS/OPEN ENDED TERMS
Pollution Scrubbers Pollution Control
Aluminum Oxide Calcium Stationary Sources
Extraction Aluminum Industry Alumina Extraction
Waste Treatment Clays Scrubbing Waste
Calcium Oxides Sodium Carbonates Coal Ash
Calcium Carbonates Coal Dicalcium Silicate
Sulfur Portland Cements
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
c. COS ATI Field/Group
13B 131
07B
13H,07A 11F
08G
21D
11B
21. NO. OF PAGES
56
22. PRICE
EPA Form 2220-1 (»-73)
49
------- |