xvEPA
TVA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-80-050
March 1980
Tennessee Valley Authority
Office of Power
Energy Demonstrations
and Technology
Muscle Shoals Al 35660
EDT-112
Preliminary Economic
Analysis of a Lime Spray
Dryer FGD System
Interagency
Energy/Environment
R&D Program Report
-------
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3. Ecological Research
4. Environmental Monitoring
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6. Scientific and Technical Assessment Reports (STAR)
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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
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tems. The goal of the Program is to assure the rapid development of domestic
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essary environmental data and control technology. Investigations include analy-
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EPA-600/7-80-050
EDT-112
March 1980
Preliminary Economic Analysis
of a Lime Spray
Dryer FGD System
by
T.A. Burnett and W.E. O'Brien
TVA Office of Power
Division of Energy Demonstrations and Technology
Muscle Shoals, Alabama 35660
Interagency Agreement No. D9-E721-BI
Program Element No. INE827
EPA Project Officer: Theodore G. Brna
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
DISCLAIMER
This report was prepared by the Tennessee Valley Authority and has
been reviewed by the Office of Environmental Engineering and Technology,
U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the
views and policies of the Tennessee Valley Authority or the U.S. Environ-
mental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
ii
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ABSTRACT
A preliminary economic analysis of two flue gas desulfurization
(FGD) processes, one dry and one wet, were performed for a new 500-MW
power plant burning western coal having 0.7% sulfur, 9.7% ash, and a
heating value of 9,700 Btu/lb and meeting current new source performance
standards (70% S02 removal and 0.03 Ib/MBtu particulate emission). The
generic lime spray dryer process used a baghouse for particulate collection,
while the wet limestone slurry process had an electrostatic precipitator
(ESP) for particulate control. In addition to the coal noted, the final
report will include an economic evaluation for both a low- and a high-
sulfur eastern coal.
Results of the preliminary analysis show that the capital investment
costs for the generic lime spray dryer process for S02 and particulate
removal are $132/kW while being $186/kW for the ESP-wet limestone
slurry combination. First-year and levelized annual revenue requirements
are 6.20 and 8.55 mills/kW, respectively, for the dry FGD process; 8.55
and 11.71 mills/kWh, respectively, for the wet process.
Sensitivity analyses indicate (1) delivered raw material costs do
not significantly affect the annual revenue requirements for either the
wet or dry process, (2) annual revenue requirements for the spray dryer
are insensitive to the raw material stoichiometry, and (3) waste disposal
for the wet process even with fixation is still more expensive than for
the generic lime spray dryer process.
iii
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CONTENTS
Abstract iii
Figures vii
Tables viii
Abbreviations and Conversion Factors ix
Acknowledgements x
Executive Summary xi
Introduction 1
Conclusions 4
Recommendations 5
Design and Economic Premises 6
Design Premises 5
Emission Standards 6
Fuel 7
Power Plant Design 8
Power Plant Operation 8
Flue Gas Composition 8
Absorber Design 9
Reheat 10
Raw Materials 10
Waste Disposal 11
Economic Premises 11
Capital Costs H
Capital Investment Estimates 14
Annual Revenue Requirements 17
Process Background and Description 19
Generic Lime Spray Dryer Process 19
Process Description 19
Analysis of Processing Subsections 23
Limestone Slurry Process 28
Process Description 28
Analysis of Processing Subsections 31
Economic Evaluation and Comparison 38
Accuracy of Estimates 38
Capital Investment 39
Generic Lime Spray Dryer Process 39
Limestone Slurry Process 41
v
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Comparison 4^
Annual Revenue Requirements /-
Generic Lime Spray Dryer Process 42
Limestone Slurry Process 45
Comparison ^c
Sensitivity Analysis 47
Sensitivity to Raw Material Prices ^
Sensitivity to Raw Material Stoichiometry 49
Sensitivity to Waste Disposal Costs 49
References 52
vi
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FIGURES
Number
S-l Generic lime spray dryer process. Block flow diagram . . .
S-2 Limestone slurry process. Block flow diagram
S-3 Sensitivity of the first-year annual revenue require-
ments to the delivered cost of the raw material Xxi
S-4 Sensitivity of the first-year annual revenue require-
ments to the raw material stoichiometry in the absorber . . xxi
1 Generic lime spray dryer process. Flow diagram 20
2 Limestone slurry process. Flow diagram 29
3 Sensitivity of the first-year annual revenue require-
ments to the delivered cost of the raw material 48
4 Sensitivity of the first-year annual revenue require-
ments to the raw material stoichiometry in the absorber . . 48
vii
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TABLES
Number Page
S-l Major Design Premises ..
S-2 Base-Case Comparison of Capital Investments and Annual
Revenue Requirements ..
S-3 Summary of the Total Capital Investments ..
S-4 Summary of First-Year Annual Revenue Requirements .
1 Contract Awards for Spray Dryer-Based FGD Systems ^
2 Coal Composition and Flow Rate
3 Fly Ash Analysis
4 Base-Case Flue Gas Composition and Flow Rate
5 Design Conditions for Absorber System Calculations .... 1n
6 Levelized Annual Capital Charges for Regulated Utility
Financing .,
7 Cost Indexes and Projections
8 Projected 1984 Unit Costs for Raw Materials, Labor, and
Utilities
9 Generic Lime Spray Dryer Process Material Balance 2i
10 Generic Lime Spray Dryer Process Base-Case Equipment
List, Description, and Cost 2,
11 Limestone Slurry Process Material Balance »_
12 Limestone Slurry Process Base-Case Equipment List,
Description, and Cost _?
13 Generic Lime Spray Dryer Process Total Capital Investment . 40
14 Limestone Slurry Process Total Capital Investment 42
15 Base-Case Total Direct Investments and Total Capital
Investments ,,
16 Summary of the Total Capital Investments /-
17 Generic Lime Spray Dryer Process Annual Revenue Require-
ments 44
18 Limestone Slurry Process Annual Revenue Requirements ... //:
19 Base-Case Total First-Year and Levelized Annual Revenue
Requirements
20 Summary of the Total First-Year Revenue Requirements ... /7
21 Comparison of Total Capital Investment and First-Year
Unit Revenue Requirements for the Generic Lime Spray
Dryer Process at Various Raw Material Stoichiometries
viii
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ABBREVIATIONS AND CONVERSION FACTORS
ABBREVIATIONS
o
aftj actual cubic feet kg
Btu British thermal unit k&
°C degrees Celsius kW
dia diameter kWh
ESP electrostatic precipitator lb
°F degrees Fahrenheit k
FD forced draft M
FGD flue gas desulfurization min
ft feet mol
ft/sec feet per second MW
g gram ppm
gal gallon sft3
gpm gallons per minute sec
gr grain vol
hr hour wt
ID induced draft yr
in. inch
kilogram
kiloliter
kilowatt
kilowatthour
pound
thousand (kilo)
million (mega)
minute
mole
megawatt (electrical)
parts per million (volume)
standard cubic feet
second
volume
weight
year
CONVERSION FACTORS
To convert from English units
acres
British thermal units
degrees Fahrenheit minus 32
feet
square feet
cubic feet
cubic feet per minute
gallons (U.S.)
gallons per minute
grains per cubic foot
horsepower
inches
pounds (mass)
pounds per cubic foot
pounds (force) per square inch
miles
standard cubic feet per minute
(60°F)
tons (short)3
To metric units
hectares
kilocalories
degrees Celsius
centimeters
square meters
cubic meters
cubic meters per second
liters
liters per second
grams per cubic meter
kilowatts
centimeters
kilograms
kilograms per cubic meter
Pascals (Newton per square meter)
meters
normal cubic meters per hour (0°C)
metric tons
Multiply
by
0.405
0.252
0.5556
30.48
0.0929
0.02832
0.000472
3.785
0.06308
2.288
0.746
2.54
0.4536
16.02
6895
1609
1.6077
0.9072
a. All tons, including tons of sulfur, are expressed in short tons.
ix
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ACKNOWLEDGEMENTS
Partial, support for this study was provided by the Department of
Energy by means of pass-through funds to the Environmental Protection
Agency.
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PRELIMINARY ECONOMIC ANALYSIS OF A LIME SPRAY DRYER FGD SYSTEM
EXECUTIVE SUMMARY
Dry-scrubbing flue gas desulfurization (FGD) technology using a
concentrated solution or suspension of a reactive absorbent in a spray
dryer is a recent development in electric utility FGD. It is receiving
extensive attention, at the present time, and contracts have been awarded
for nine commercial installations. Much of this interest is due to some
potentially significant technical advantages over conventional wet FGD
technology—the process design is relatively simple; stack gas reheat
may be substantially reduced or eliminated, and the product is a dry
waste rather than a wet sludge.
These dry scrubbers have one significant disadvantage—the use of
an expensive (relative to limestone) alkali absorbent, either lime or
soda ash. The raw material cost penalty for using lime or soda ash must
be offset by savings in capital charges and maintenance costs for spray
dryer systems to be economically competitive with the wet limestone
systems. Minimizing these raw material costs is one of the reasons that
the first commercial utility applications of these systems are on boilers
fired with lignite and subbituminous coals. Both of these types of
coals are normally low in sulfur and, therefore, the amount of expensive
alkali raw material to be consumed in the FGD system is minimized. (In
fact, the average fuel sulfur level at the utility boilers currently
under contract is less than 1.0%.) These fuels also produce a highly
alkaline ash which, if recycled through the spray dryer, can further
reduce makeup raw material requirements.
Although capital investments and revenue requirements for these
processes have been estimated by various process vendors and compared
with a conventional wet limestone slurry process, no independent economic
comparisons based on comparable design and economic premises have been
published. The purpose of this economic evaluation is to compare the
costs of the spray dryer FGD technology with those of the limestone
slurry process based on the technical and economic premises developed
jointly by the Environmental Protection Agency (EPA) and the Tennessee
Valley Authority (TVA).
In addition to the base-case evaluations, sensitivity analyses of
raw material costs and stoichiometries on the annual revenue requirements
were performed. The capital investment and annual revenue requirements
xi
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for the limestone slurry process with sludge fixation by the IU Conversion
Systems, Incorporated (IUCS) process and landfill disposal were determined
for comparison with the costs of pond disposal.
DESIGN AND ECONOMIC PREMISES
Design Premises
Table S-l lists the major design premises for this study. The
base-case power plant is a new, 500-MW coal-fired power unit located in
the Great Plains - Rocky Mountain region. The fuel is a subbituminous
coal with a heating value of 9,700 Btu/lb and containing 0.7% sulfur
(dry basis), 9.7% ash, and 16% moisture. The boiler heat rate is 9,500
Btu/kWh.
TABLE S-l. MAJOR DESIGN PREMISES
Item
Premise
Power plant
Operating schedule
Fuel
Base year
FGD waste disposal
S02 removal- efficiency
Particulate removal efficiency
SOo absorber redundancy
New, Great Plains - Rocky Mountain
region, 500-MW coal-fired boiler,
9,500 Btu/kWh heat rate
130,400 hr, 30-yr life, 5,500-hr first-
year operation
Subbituminous coal; 9,700 Btu/lb, 0.7%
sulfur, 9.7% ash, 16% moisture
Capital investment: mid-1982
Revenue requirements: 1984
Limestone: clay-lined pond
Generic lime spray dryer: landfill
70%
99.8% (0.03 Ib of particulates/MBtu
heat input)
33% (3 operating trains, 1 spare)
The FGD unit includes all the equipment necessary to meet the
recent (June 1979) new source performance standards (NSPS) for both
particulate matter (0.03 Ib/MBtu heat input) and S02 (overall 70% removal
for low-sulfur coals). The overall design for the generic lime spray
dryer system is based on vendor information, while the design of the
limestone slurry process is based on in-house data and previous evaluations
by TVA.
xii
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Economic Premises
The project is assumed to begin in mid-1980 with a 3-yr construction
period ending in mid-1983. The midpoint of construction costs, and
therefore the basis for the capital investment costs, is mid-1982. The
revenue requirements are based on 1984 costs. Delivered costs for raw
materials are projected based on mid-1979 prices in the Great Plains -
Rocky Mountain region. Labor rates for 1984 for this region are assumed
to be equivalent to those for a midwestern location and are projected
from current midwestern labor costs.
Capital investment estimate is made up of direct investment, indirect
investment, and other capital charges. The direct investment is based
on equipment lists and other installation costs (such as piping, electrical,
instrumentation, etc.) are factored from the equipment costs. Indirect
investment (engineering design and supervision, construction expense,
etc.) is estimated based on the direct investment. Other capital costs
(allowance for startup and modification, interest during construction,
etc.) are estimated from the total direct and indirect investment.
These preliminary capital investment estimates are normally considered
to have a -20% to +40% range of accuracy (i.e., in an actual application
of the generic lime spray dryer process for this 500-MW boiler the capital
investment could range from 20% less to 40% more than the projected $132.3/kW)
Two types of annual revenue requirements are projected—first year
and levelized. Both are based on 5,500 hours of operation per year at
full load (about a 63% capacity factor) and both use a levelized capital
charge. Levelized annual revenue requirements differ from first-year
annual revenue requirements in that they take into consideration the
time value of money over the life of the FGD unit and are calculated
using a 10% discount factor, 6% inflation factor, and a 30-yr economic
life.
PROCESS BACKGROUND AND DESCRIPTION
Generic Lime Spray Dryer Process
The generic lime spray dryer process (Figure S-l) contains only two
major equipment items, a spray dryer and a baghouse. Most of the flue
gas from the boiler passes untreated to the spray dryer where it contacts
an atomized slurry of lime and recycled waste. The sulfur oxides are
absorbed and react with the lime, and fly ash alkali if present, to form
calcium sulfite and calcium sulfate. The slurry concentration is adjusted
so that the water injected into the spray dryer is insufficient to
saturate the flue gas and the resulting waste material leaves as dry
particulate matter entrained in the flue gas.
xiii
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STACK
PARTIAL BYPASS
X
H-
BOILER
MATERIAL
HANDLING AND
FEED PREPARATION
4
'\
^ SOo jT fc P ARTICULATE
^ ABSORPTION ^ REMOVAL
„
W ^ _
^^ WASTE STORAGE
1
^ GAS
~ HANDLING
^ WASTE DISPOSAL
Figure S-l. Generic lime spray dryer process. Block flow diagram.
-------
The remaining flue gas from the boiler (22% of the total gas rate)
bypasses the spray dryers and enters the flue gas ducts downstream of
the spray dryers but before entering the baghouse. The system is designed
such that the overall SOo removal will meet the recently promulgated
(June 1979) NSPS (i.e., 70% removal for coal containing 0.7% sulfur).
The calcium-based particulate matter formed in the spray dryer and
the fly ash from the boiler are removed in the baghouse, which is designed
to meet the NSPS for particulate matter (0.03 Ib/MBtu). Part of the
waste material from the baghouse (both fly ash and calcium-based salts)
is temporarily stored in a hopper before trucking to the landfill. The
remainder is reslurried and recycled to the spray dryer.
The only other area is the lime preparation area where lime is
stored, slaked, and pumped to the spray dryers. Surge capacity for both
the dry lime and the lime slurry is included.
Limestone Slurry Process
The limestone slurry process (Figure S-2) is also a relatively
simple process containing only two major equipment items, a high-efficiency
electrostatic precipitator (ESP) and a venturi/spray tower wet scrubber.
Although ESP's are not normally considered a part of the limestone
slurry process, they have been included in this limestone slurry process
so that it can be compared with the generic lime spray dryer process.
Flue gas from the boiler passes through the ESP for fly ash removal
to meet the NSPS. (The fly ash from the ESP is trucked to the disposal
pond.) The flue gas from the ESP is divided into two streams. Most
(72%) of the flue gas enters the S02 scrubbers where 90% of the entering
S02 is absorbed to achieve the overall 70% SC>2 removal required by the
NSPS for the 0.7% sulfur coal. The remaining flue gas bypasses the
scrubbers and enters the flue gas ducts after the scrubber, providing
sufficient heat to make reheating unnecessary.
Part of the recirculating slurry in the absorption section is bled
off and pumped to the disposal pond. The wet calcium sulfite-sulfate
salts settle out as a 40% (by weight) sludge, and the supernate is
recycled for reuse in the process.
The major remaining processing area is the limestone preparation
area where the makeup limestone is stored, crushed, milled, and slurried
before being added to the recirculating slurry. Surge capacity for both
dry limestone and the limestone slurry is included.
ECONOMIC EVALUATION AND COMPARISON
Preliminary estimates of capital investment, first-year revenue
requirements, and levelized annual revenue requirements were prepared
for both the generic lime spray dryer process and the limestone slurry
process based on the design and economic premises. These results are
shown in Table S-2.
xv
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PARTIAL BYPASS
" ,
BOILER
PARTICULATE
REMOVAL
GAS
HANDLING
STACK
t
ABSORPTION
I
WASTE
DISPOSAL
MATERIAL HANDLING
AND
FEED PREPARATION
Figure S-2. Limestone slurry process. Block flow diagram.
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TABLE S-2. BASE-CASE COMPARISON OF CAPITAL
INVESTMENTS AND ANNUAL REVENUE REQUIREMENTS
Generic lime
spray dryer
process
Capital investment (1982 $)
M$
$/kW
Total first-year revenue require-
ments (1984 $)
M$
mills/kWh
Levelized annual revenue require-
ments (1984 $)
M$
mills/kWh
66.2
132.3
17.04
6.20
23.52
8.55
Limestone
slurry
process
93.2
186.4
23.50
8.55
32.19
11.71
The capital investment for the generic lime spray dryer process is
$66.2M ($132.3/kW) in mid-1982 dollars. The total direct investment
portion of the capital investment, which includes equipment costs and
installation expenses, accounts for $32.5M. The major processing areas,
in terms of investment required, are particulate matter removal ($11.1M),
gas handling ($7.2M), and S02 absorption ($7.2M). These areas alone
account for 78% of the direct investment. The indirect investments
(engineering design and supervision, architect and engineering contractor,
etc.) are about $18.2M; the other capital charges (allowance for startup
and modifications, interest during construction, etc.) make up the
remaining $15.5M.
The capital investment for the limestone slurry process is $93.2M
($186.4/kW) in mid-1982 dollars. The total direct investment portion of
the capital investment accounts for $45.7M. The major processing areas
in this total direct investment are S02 absorption ($13.7M), particulate
matter removal ($12.4M), and gas handling ($9.9M). These three areas
account for about 79% of the direct investment. The indirect investments
and the other capital charges account for $25.5M and $21.9M of the capital
investment respectively.
The first-year and the levelized annual revenue requirements for
the generic lime spray dryer process are $17.OM (6.20 mills/kWh) and
$23.5M (8.55 mills/kWh) respectively. The major component of these
revenue requirements is the levelized capital charges of $9.7M. Other
important annual costs are maintenance ($1.9M), overheads ($1.8M), elec-
tricity ($1.5M), and lime ($1.0M).
xvii
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The first-year and the levelized annual revenue requirements for
the limestone slurry process are $23.5M (8.55 mills/kWh) and $32.2M
(11.71 mills/kWh) respectively. Again, the major component of these
revenue requirements is the levelized capital charges of $13.7M. Other
major annual costs are maintenance ($3.5M), overheads ($3.0M), and
electricity ($1.8M).
Comparisons
In terms of both capital investment and first-year annual revenue
requirements, the base-case generic lime spray dryer process is sub-
stantially lower in cost than the base-case limestone slurry process as
shown in Table S-2. The capital investment for the generic lime spray
dryer process is about 29% lower, and the first-year annual revenue
requirements are about 28% lower, than those for the limestone slurry
process.
If these total capital investments are broken down into individual
investment areas as shown in Table S-3, the reasons for the higher cost
of the limestone slurry process are apparent. With the exception of the
material handling area and particulate matter handling and recycle area
(which the limestone slurry process does not have), the area investments
for the limestone slurry process are higher than those for the generic
lime spray dryer process. In fact the differences in only three areas,
the SC>2 absorption, disposal area preparation, and gas-handling areas,
account for a $12.8M difference in direct investment, or about $26.OM in
total capital investment when the other capital charges are adjusted to
reflect the higher direct investment.
TABLE S-3. SUMMARY OF THE TOTAL CAPITAL INVESTMENTS
Investment area
Material handling
Feed preparation
Gas handling
S02 absorption
Particulate removal
Particulate handling
and recycle
Solids disposal
Disposal area preparation
Land
All other capital costs
Total capital investment
Total cost
Generic lime
spray dryer
process
2,443
599
7,190
7,173
11,133
1,425
379
321
515
34,993
66,171
, k$
Limestone
slurry
process
919
1,071
9,924
13,734
12,395
-
1,453
3,793
910
48,910
93,109
Basis:
TVA design and economic premises.
xviii
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The lower investment costs for the generic lime spray dryer process
in these three areas are primarily due to the use of the spray dryer
absorber. The design of the generic lime spray dryer process precludes
the need for mist eliminators and the large recirculating slurry pumps
which are used in the SC^ absorption area of the limestone slurry process.
The higher land and disposal area preparation costs (i.e., pond construction)
for the limestone slurry process are due to the nature of the settled
sludge in the pond (i.e., the sludge in the pond is only 40% solids) in
contrast to the dry waste going to the landfill in the generic lime
spray dryer process.
The first-year annual revenue requirements are broken down into
various annual costs in Table S-4. Major cost differences between the
processes are costs for raw materials, maintenance, and levelized capital
charges. The higher raw material cost for the generic lime spray dryer
process is due to the consumption of expensive lime ($102/ton) rather
than limestone ($8.50/ton). Maintenance costs for the limestone slurry
process are substantially higher because of the need to recirculate
large amounts of limestone slurry through the process equipment. Levelized
capital charges are higher for the limestone slurry process because of
the higher total capital investment required.
TABLE S-4. SUMMARY OF FIRST-YEAR ANNUAL REVENUE REQUIREMENTS
Raw materials
Operating labor and supervision
Electricity
Maintenance
Levelized capital charges
Other annual costs
Total first-year revenue
requirements
Total cost, $
Generic lime
spray dryer
process
1,026,900
948,800
1,485,600
1,939,400
9,727,100
1,912,600
Limestone
slurry
process
133,900
1,321,600
1,764,300
3,464,700
13,698,800
3,120,500
17,040,400 23,503,800
SENSITIVITY ANALYSIS
Sensitivity to Raw Material Cost
The generic lime spray dryer process is more sensitive to changes
in the delivered price of the raw material than the limestone slurry
process. Because of the low-sulfur coal used and the low S02 removal
requirement, however, cost changes from the base case do not significantly
xix
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change the economic results, as shown in Figure S-3. The generic lime
spray dryer process has lower first-year annual revenue requirements
regardless of the raw material prices selected.
The limestone slurry process, because of the low unit cost of
limestone as well as the low-sulfur level in the coal and the low SO?
removal requirement, is essentially insensitive to the delivered price
of limestone.
Sensitivity to Raw Material Stoichiometry
Since the design Stoichiometry for the limestone slurry process is
based on the results from actual low-sulfur coal applications, only the
base-case Stoichiometry for the limestone slurry process was evaluated.
The generic lime spray dryer process, however, represents technology
which has not been demonstrated on a commercial scale and hence may
change as this technology is developed further. Therefore, a range of
raw material stoichiometries from 1.00 (-18.0%) to 1.46 (+19.7%) was
evaluated.
The results of this sensitivity analysis are not significantly
different from those previously discussed for the sensitivity to raw
material prices (i.e., regardless of what reasonable raw material Stoichio-
metry is used for the generic lime spray dryer process, the generic lime
spray dryer process has a lower first-year annual revenue requirement
than the base-case limestone slurry process) as shown in Figure S-4.
Sensitivity to Waste Disposal Costs
Since some power plant locations do not have sufficient land available
for ponding of the limestone slurry process waste, the relative economics
for a limestone slurry process with an alternative disposal method, the
IUCS fixation process, were also evaluated. The limestone slurry process
up to the point at which the purge stream leaves the scrubbers is identical
for both cases. For the base-case limestone slurry process, the scrubbing
waste is simply pumped to the pond and the supernate is returned to the
process. For the limestone slurry - IUCS fixation process, the waste is
pumped to a thickener and filter for dewatering, mixed with lime and fly
ash, and allowed to set up before being hauled by truck to an onsite
landfill for disposal.
The total capital investment for this combination limestone slurry -
IUCS pro.cess is $91.4M ($183/kW) in 1982 dollars or nearly $2.0M less
than the base-case limestone slurry process with ponding. This decrease
in capital investment is due to the substantially lower disposal area
preparation costs and land requirements for the IUCS alternative.
The first-year and the levelized annual revenue requirements for
the limestone slurry - IUCS fixation process are $24.98M (9.08 mills/kWh)
and $35.20M (12.80 mills/kWh) respectively. These costs are about 6%
higher than those for the base case (i.e., with ponding) primarily
because of the higher labor costs and related higher overhead costs.
xx
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LIMESTONE COST, S/TON
X
X
M-
10.0
§ 9.0
1/5
rf
cn
2 8'°
W
a.
D
8'
Q£
g 7.0
Z
UJ
w
^ 6.0
i
>«
H
w
2
fc 5.0
4.0
5.00 8.50 12.00
1 1 1
~ Limestone slurry process
"— ~~"
- —
Generic 1 iine spray dryer process
i i i
10.0
g 9.0
en
*
g 8.0
M
1
M
K
P£
p 7-0
u
S
a:
5 6.0
f
H
t/3
fc 5.0
4.0
n
1 1 1 I 1
Limestone slurry process
_
_
B
Generic lime spray dryer process
— _
i i i i i
75.00 102.00 125.00
LIME COST (DELIVERED), $/TON
Figure S-3. Sensitivity of the first-year
annual revenue requirements to
the delivered cost of the raw
material.
RAW MATERIAL STOICHIOMETRY, MOL ALKALI/MOL S02 ABSORBED
Figure S-4. Sensitivity of the first-year annual
revenue requirements to the raw material
stoichiometry in the absorber.
-------
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
For a new, 500-MW power unit burning a 0.7% sulfur subbituminous
coal, the generic lime spray dryer process has a lower total capital
investment and lower annual revenue requirements than a comparable
limestone slurry process. These differences in capital investment and
annual revenue requirements are larger than the uncertainty surrounding
the comparability of preliminary economic estimates of this type (+10%).
Therefore, for the assumed design and economic premises the generic lime
spray dryer process appears to have a significant economic advantage
over a conventional limestone slurry process.
For these design and economic premises, the generic lime spray
dryer process maintains its economic advantage over the limestone slurry
process for all ranges of raw material costs and raw material stoichio-
metries studied. The generic lime spray dryer process also has an
economic advantage over a combined limestone slurry - IUCS process for
fixation and landfill instead of ponding waste disposal.
Recommendations
Since only a single base-case application of the generic lime spray
dryer process has been considered in this study, a definitive economic
analysis of this process is suggested as the logical next step. Not
only would the accuracy of the capital investment and annual revenue
requirements for the base case be increased, but several case variations
(power unit size, sulfur level in the coal, S02 removal efficiency, for
example) could be evaluated.
Other areas which require additional study (and which will be
evaluated in the final report for this project) include:
« Generic soda ash spray dryer process for a low-sulfur subbituminous
coal application.
o Generic lime spray dryer process for a low-sulfur eastern coal
application.
o Generic lime spray dryer process for a high-sulfur eastern coal
application.
xxii
-------
PRELIMINARY ECONOMIC ANALYSIS OF A LIME SPRAY DRYER FGD SYSTEM
INTRODUCTION
One of the recent developments in flue gas desulfurization (FGD),
the so-called dry scrubbing technology using a concentrated solution or
suspension (depending on whether the alkali material is sodium- or
calcium-based) of a reactive absorbent in a spray dryer, is currently
receiving a considerable amount of attention. Much of this interest is
due to some potentially significant technical advantages over conventional
wet FGD technology (primarily lime or limestone slurry scrubbing). In
particular, the process design is relatively simple and a dry waste,
rather than a wet sludge, is produced.
Nine contracts have been awarded for these dry scrubbers (listed in
Table 1), six for commercial utility boilers and three for industrial
boilers. With the exception of one utility boiler application which
uses a sodium-based system, the systems under contract use lime-based
spray dryer technology. Of the six utility boiler applications, three
are lignite-fired boilers and three are fired with subbituminous coal.
All six of these boiler fuels are relatively low in sulfur (<1%) and
have a highly alkaline fly ash. Two of the three industrial boiler
applications, on the other hand, involve eastern bituminous coals which
have higher sulfur levels and relatively low alkalinity in the fly ash.
These dry scrubbers have one significant disadvantage—the use of
an expensive (relative to limestone) alkali absorbent, either lime or
soda ash. As long as the savings in capital charges and maintenance
costs for the spray dryer systems are higher than the raw material cost
penalty for lime or soda ash, the spray dryer systems will remain econom-
ically competitive with the wet limestone systems. This is one of the
reasons that the first commercial applications are on utility boilers
fired with lignite and subbituminous coals. Since both of these types
of coals are normally low in sulfur, the amount of sulfur to be removed,
and hence the consumption of expensive alkali raw material in the FGD
system, is minimized. (In fact, the average sulfur levels in the fuels
at the utility boilers currently under contract are all less than 1.0%
sulfur.)
-------
TABLE 1. CONTRACT AWARDS FOR SPRAY DRYER-BASED FGD SYSTEMS
Installation
Utility Boiler
Coyote Unit 1
Antelope Valley Unit 1
Laramie River Unit 3
Stanton Unit 2
Springerville Unit 1
Springerville Unit 2
Rawhide Unit 1
Industrial Boiler
Strathmore Paper Co.
Celanese
University of Minnesota
Size,
gross MW
410
440
575
63
350
350
250
14e
22e
83e
Fuel
type (% S)
Lignite (0.78)
Lignite (0.68)
Subbituminous
Lignite (0.77)
Subbituminous
Subbituminous
Subbituminous
Bituminous (2.
Bituminous (1.
Subbituminous
(0.54)
(0.69)
(0.69)
(0.29)
0-2.5)
0-2.0)
(0.6-0.
S02 Alkali raw Startup
removal, % material date
50
62
85
73
61
61
70
75
70-80
7) 70
Soda ash
Lime
Lime
Lime
Lime
Lime
Lime
Lime
Lime
Lime
4/81
4/82
4/81
9/82
2/85
9/86
12/83
7/79
1/80
9/81
Vendor
RI/WF3
Joy/Niro
B&WC
R-Cd
Joy/Niro
Joy/Niro
Joy/Niro
Mikropul
RI/WF
Carborundum
a. Rockwell International/Wheelabrator-Frye.
b. Western Precipitation Division of Joy Manufacturing
c. Babcock and Wilcox.
d. Research-Cottrell.
e. Based on 2,900 aft
/MW.
Company /Niro
Atomizer, Inc.
-------
Another advantage for the spray dryer processes associated with
these western coals is the relatively high alkalinity of the fly ash
from these coals. Not only does this alkalinity react with sulfur in
the boiler and thus reduce the amount of sulfur removal required in the
FGD system, but the alkalinity in the fly ash also removes sulfur oxides
(SOX) from the flue gas in the spray dryer (if recycled) and thereby
decreases the consumption of makeup alkali raw material.
Thus, in order to reflect the current utility market for these
spray dryer systems, the fuel chosen for this study is a low-sulfur
subbituminous coal containing a highly alkaline ash.
Although capital investments and revenue requirements for these dry
scrubbing processes have been estimated by various process vendors and
compared with a conventional wet limestone slurry process, no independent
economic comparisons have been published. The purpose of this study is
to make an economic comparison of a generic lime spray dryer process
with a conventional wet limestone slurry process using the same design
and economic premises.
In addition to these base-case evaluations, a sensitivity analysis
is included in which the annual revenue requirements are calculated for
various raw material costs and stoichiometries. The capital investment
and annual revenue requirements for an alternate limestone slurry process
with sludge fixation and landfill disposal are also included.
-------
CONCLUSIONS
For a new, 500-MW power unit burning a 0.7% sulfur subbituminous
coal, the generic lime spray dryer process has a lower total capital
investment and lower annual revenue requirements than a comparable
limestone slurry process. These differences in capital investment and
annual revenue requirements are larger than the uncertainty surrounding
the comparability of preliminary economic estimates of this type (+10%).
Therefore, for the assumed design and economic premises the generic lime
spray dryer process appears to have a significant economic advantage
over a conventional limestone slurry process.
For these design and economic premises, the generic lime spray
dryer process maintains its economic advantage over the limestone slurry
process for all ranges of raw material costs and raw material stoichio-
metries studied. The generic lime spray dryer process also has an
economic advantage over a combined limestone slurry - IUCS process for
fixation and landfill instead of ponding waste disposal.
-------
RECOMMENDATIONS
Since only a single base-case application of the generic lime spray
dryer process has been considered in this study, a definitive economic
analysis of this process is suggested as the logical next step. Not
only would the accuracy of the capital investment and annual revenue
requirements for the base case be increased, but several case variations
(power unit size, sulfur level in the coal, S02 removal efficiency, for
example) could be evaluated.
Other areas which require additional study (and which will be
evaluated in the final report for this project) include:
• Generic soda ash spray dryer process for a low-sulfur subbituminous
coal application.
• Generic lime spray dryer process for a low-sulfur eastern coal
application.
• Generic lime spray dryer process for a high-sulfur eastern coal
application.
-------
DESIGN AND ECONOMIC PREMISES
This study compares the economics of two FGD systems on an equitable
basis using conditions that are as representative as possible of projected
industry conditions and that provide a clearly definable breakdown of
costs into significant and useful divisions. The premises used in this
study have been developed by the Tennessee Valley Authority (TVA), the
U.S. Environmental Protection Agency (EPA), and others during similar
economic evaluations made since 1967. Criteria of the premises are
designed to establish efficiencies, process flow rates, and other
operating and design conditions. The economic premises are designed to
represent the many factors affecting costs.
DESIGN PREMISES
The utility plant design and operation is based on Federal Energy
Regulatory Commission (FERC) historical data (1) and TVA experience.
The conditions used are representative of a typical modern boiler for which
FGD systems would most likely be considered. An Upper Great Plains and
Rocky Mountain location typical of Wyoming, Colorado, Nebraska, and
North and South Dakota is used because the concentration of both low-
sulfur subbituminous coal supplies and power plants in this area make it
representative of the segment of the power industry most attracted to
the spray dryer FGD technology*
Although the FGD design is assumed to be proven, in keeping with
current industry practice a redundant absorber train is provided to
maintain acceptable boiler availability. In the integration of the
absorber system with the boiler systems, provision for turndown and
maintenance are limited to provision of a common plenum between the
systems with dampers to allow individual trains to be shut down.
Emission Standards
New source performance standards (NSPS) established by EPA (2)
specify a maximum emission, based on heat input, of 0.03 Ib/MBtu for
particulate matter, 1.2 Ib/MBtu for S02, and 0.5 Ib/MBtu for NOX. In
addition to meeting this maximum emission limit of 1.2 Ib/MBtu for SO?,
the NSPS also require that new plants must reduce the uncontrolled SO?
emissions from 70% to 90%, depending on the uncontrolled S02 emission
level. For the low-sulfur subbituminous coal chosen in this study, this
percentage S07 reduction is 70%. In addition it is assumed that the
-------
boiler is designed to meet the 0.5 Ib/MBtu NOX standard and that the FGD
system includes all the process equipment needed to meet both the 0.03
Ib/MBtu particulate matter standard and the 70% S02 removal standard.
Fuel
The coal premises are composites of many samples representing major
western coal production areas. The subbituminous coal is assumed to
have a heating value of 9,700 Btu/lb and an ash content of 9.7% (both as
fired) and a sulfur content of 0.7% (dry basis). The composition and
flow rates for the base-case conditions are shown in Table 2. Although
fly ash compositions are not normally of great significance in specifying
a limestone FGD system, if the fly ash contains appreciable alkalinity
it can have a significant effect on the economics of dry FGD systems
which consume an expensive alkali raw material. Because of the high
alkalinity of many western coals, a typical alkaline fly ash with the
composition shown in Table 3 is used.
TABLE 2. COAL COMPOSITION AND FLOW RATE
Coal
component
C
H
0
N
S
Cl
Ash
H20
Wt %
as fired
57.00
3.90
11.50
1.20
0.59
0.10
9.70
16.00
Ib/hr
279,100
19,100
56,310
5,876
2,889
A90
47,500
78,350
Basis:
500-MW new coal-fired unit, 9,500
Btu/kWh, 9,700 Btu/lb heating value,
0.7% sulfur in coal, dry basis.
-------
TABLE 3. FLY ASH ANALYSIS
Fly ash component Wt
Si02
A120
Fe203
CaO
MgO
Na-,0
K20
Ti02
S03
Other
Total
32.2
17.4
6.0
20.0
4.7
1.7
0.5
1.0
15.3
1.2
100.0
Power Plant Design
A single horizontal opposed, balanced-draft boiler for a 500-MW net
electrical output is used. This net output does not include the power
requirements for the FGD system. In contrast to some previous FGD
studies by TVA, particulate matter removal and disposal have been included
as part of the FGD unit rather than as part of the boiler because of the
nature of the dry sorbent processes, which collect fly ash and sulfur
salts simultaneously.
Power Plant Operation
An operating life of 30 years and a total operating lifetime of
130,500 hours are used. For this study a boiler capacity factor of
62.8% (equivalent to full load for 5,500 hr/yr) and a boiler heat rate
of 9,500 Btu/kWh are used.
Flue Gas Composition
Flue gas compositions are the result of boiler design, fuel, and a
variety of operating conditions. Combustion and emission conditions
used to determine flue gas composition are based on balanced-draft
boiler design and average values for the sulfur content of coal. Flue
gas compositions are based on combustion of pulverized coal using a
total air rate equivalent to 139% of the stoichiometric requirement.
This includes 20% excess air to the boiler and 19% air inleakage in the
boiler air heater. These values reflect TVA operating experience with
horizontal, frontal-fired, coal-burning units. It is assumed that 80%
of the ash present in coal is emitted as fly ash and 85% of the sulfur
in coal is emitted as SOX. Three percent of the SOX emitted is assumed
to be SO^ and the remainder S02. The base-case flue gas composition and
flow rates calculated for these conditions are shown in Table 4.
8
-------
TABLE 4. BASE-CASE FLUE GAS COMPOSITION AND FLOW RATE
Flue gas component Volume, % Ib/hr
N2
°2
co2
so2
so3
NOX (as NO)
HC1
H20
Ash
73.09
5.39
12.24
0.04
-
0.03
0.01
9.20
-
3,887,000
327,200
1,023,000
4,760
184
1,590
504
314,600
38,000
Total 100.00 5,597,000
Basis:
500-MW new coal-fired unit, 9,500 Btu/lb heating
value, 0.7% sulfur, dry basis, 1,754,000 aft^/min
at 300°F.
Absorber Design
Absorber design criteria are based on TVA operating experience,
general power industry practice, and information from process and equip-
ment vendors. The generic lime spray dryer process is based on vendor
information. The limestone process is based on TVA experience at the
Shawnee EPA Alkali Test Demonstration Facility, extensive power industry
experience with these processes, and vendor information. Both the
generic lime spray dryer and the limestone slurry processes are fed from
a common plenum located downstream of the boiler air heaters. Both of
these FGD processes consist of four parallel trains of absorbers of
which three are operating and one is a spare. In addition, since only
70% S02 removal is required to meet the NSPS, part of the flue gas in
both processes is bypassed around the absorbers for reheat purposes.
The remaining flue gas passes through the absorbers where, depending on
the process, the S02 removal is 80% to 90%. As the flue gas leaves the
absorber, the hot bypassed flue gas is mixed with the scrubbed flue gas
to obtain a 175 F recombined flue gas.
The generic lime spray dryer process feeds a single baghouse.
Since the flue gas from these spray dryers is not saturated and does not
contain entrained liquid, mist eliminators are not required. Induced-
draft (ID) fans located between the baghouse and the stack are provided
to compensate for the assumed total pressure drop of 12 inches H20 for
the generic lime spray dryer process.
-------
The limestone slurry process is provided with high efficiency
(99.8%) electrostatic precipitators (ESP) for particulate matter removal,
venturi scrubber presaturators before the absorber, and chevron-type mist
eliminators after the spray towers. The mist eliminators reduce the
moisture content of the scrubbed gas to 0.1%. This reduces the reheating
load, decreases deposition and corrosion in downstream equipment, and
reduces particulate matter emission. A 16-inch 1^0 pressure drop is
assumed for the limestone slurry process, and in contrast to the generic
lime spray dryer process which uses ID fans, a forced-draft (FD) fan is
included between the boiler plenum and each venturi scrubber to compensate
for this pressure drop. Operating conditions for the absorbers are
shown in Table 5. These conditions are used for both the base-case and
case variation studies. Cost scaling factors based on gas and product
rates are used to calculate values at conditions other than the base
case.
TABLE 5. DESIGN CONDITIONS FOR ABSORBER SYSTEM CALCULATIONS
Operating conditions
Generic lime
spray dryer
Limestone
Presaturator
Type
Liquid 3
Liquid/gas, gal/kaft
Pressure drop, in. H20
Absorber
Type
Slurry solids, % „
Liquid/gas, gal/kaft
Pressure drop, in. 1^0
Liquid in exit gas, %
Slurry added, % solids
Effluent, % solids
Total pressure drop, in. 1^0
None
Spray dryer
22.5
0.3
2
0.0
22.5
100
12
Venturi
Scrubber
20
9
liquid
Spray tower
15
40
2
0.1
60
15
16
Reheat
Flue gas reheat to 175 F for both processes is provided by bypassing
part of the incoming flue gas around the absorbers.
Raw Materials
The raw materials used for each process are listed below. Limestone
is crushed and wet ground as part of the scrubbing operation. The lime
is not processed before use.
10
-------
Generic lime spray
Property Limestone process dryer process
Size as received
Ground size
Analysis „
Bulk density, Ib/ft
0 - 1-3/4 in.
10% to pass 200 mesh
90% CaC03
95
3/4
90%
55
- 1-1/4 in.
CaO
Waste Disposal
The disposal area is located one mile from the plant site. An
earthen-diked, clay-lined pond, designed to minimize the sum of land and
construction costs, is used for the limestone slurry process. Pond
evaporation is assumed equal to rainfall. The limestone process waste
is assumed to settle to a 40% solids sludge. An area-fill type landfill
is used for the generic lime spray dryer process. The landfill size is
based on a waste bulk density of 50 Ib/ft-* and a 30-ft fill depth.
Provisions for normal site maintenance of the pond and for normal
landfill operations, including covering the waste and contouring to
control runoff are included. No costs are provided for monitoring or
post-operation maintenance.
ECONOMIC PREMISES
The economic premises are divided into capital costs for construction
of the FGD system and annual revenue requirements for its operation.
The premises are based on regulated utility economics using the design
premises as a costing basis. The estimates use cost information obtained
from engineering-contracting, processing, and equipment companies; raw
material suppliers; and published cost indexes. Spray dryer costs were
obtained by scaling vendor-supplied information. Raw material costs are
based on those prevailing in the Upper Great Plains - Rocky Mountain
region. Labor costs are assumed equivalent to those in the Midwest.
Capital Costs
The capital structure for the electric utility company is assumed
to be:
Common stock 35%
Preferred stock 15%
Long-term debt 50%
11
-------
The cost of capital is assumed to be:
Common stock 11.4%
Preferred stock 10,0%
Long-terra debt 9.0%
Weighted cost of capital
(based on capital costs
above) 10.0%
The discount rate is 10%, the same as the weighted cost of capital.
For other economic factors needed in financial calculations, the
following values are assumed:
Investment tax credit 10%
Federal and State income tax 50%
Property tax and insurance 2.5%
Annual inflation rate 6%
The levelized annual capital charge approach used in these premises is
similar to that used by the Electric Power Research Institute (EPRI) (3).
Depreciation—
A 30-yr economic life and a 30-yr tax life are assumed for the
utility plant. Salvage value is less than 10% and is equal to removal
costs. The annual sinking fund factor for a 30-yr economic life and
10.0% weighted cost of capital is:
Sinking fund factor = Q + wcc)n - f = °-61% (1)
where: n = economic life (in years)
WCC = weighted cost of capital (as a decimal fraction)
The use of the sinking fund factor does not indicate that regulated
utilities commonly use sinking fund depreciation. The sinking fund
factor is used since it is equivalent to straight-line depreciation
levelized for the economic life of the facility using the weighted cost
of capital.
An annual interim replacement allowance of 0.56% is also included
as an adjustment to the depreciation account to ensure that the initial
investment will be recovered within the actual rather than the forecasted
life of the facility. Since power plant retirements occur at different
ages, an average service life is estimated. Many different retirement
dispersion patterns occur. The type S-l Iowa State Retirement Dispersion
pattern is used (4). This S-l pattern is symmetrical with respect to
the average-life axis and the retirements are represented to occur at a
low rate over many years. The interim replacement allowance does not
cover replacement of individual items of equipment since these are covered
by the maintenance charge.
12
-------
The sum of the years digits method of accelerated depreciation is
used for tax purposes. On a levelized basis (using flow- through accounting)
this results in a credit in the fixed charge rate as follows:
Accelerated tax depreciation = - -, - + \\ (WCC)
where: CRF = Capital recovery factor (weighted cost of capital
plus sinking fund factor) for the economic life
(as a decimal fraction)
CRF = Capital recovery factor for the tax life
(as a decimal fraction)
nT = Tax life (in years)
TTR
Levelized accelerated depreciation credit = (ATD - SLD) x
— 1 IK
where: ATD = Accelerated tax depreciation (as a decimal fraction)
SLD = Straight-line depreciation (as a decimal fraction)
ITR = Income tax rate (as a decimal fraction)
For a 50% tax rate, 30-yr tax life, 30-yr book life, 10.0% weighted cost
of capital, and 0.61% sinking fund factor, the annual levelized accelerated
depreciation credit is 1.36% using flow-through accounting.
Investment Tax Credit —
The levelized investment tax credit is calculated as follows :
(CRF ) (Investment tax credit rate)
Levelized investment tax credit =
n + wee1) f - TTRl -
where CRF , WCC, and ITR are the same factors previously defined in
equations (1) and (2).
Using a 10.0% weighted cost of capital, 0.61% sinking fund factor, 10%
investment tax credit rate, 50% income tax rate, the levelized investment
tax credit is 1.92% annually.
Income Tax —
The levelized income tax is calculated as follows:
, . j • „ r™^ , x-rr, OT^I ri Debt Ratio x Debt CostT r ITR -\
Levelized income tax = 1CRFB + AIR- SLD ] [1 -- ^j - J 4 _ ITRJ
(4)
where: AIR = Allowance for interim replacement
13
-------
Using a 10.61% capital recovery factor (weighted cost of capital plus
sinking fund factor), 0.56% allowance for interim replacements, 3.3%
straight-line depreciation, 50% debt ratio, 9.0% debt cost, and a 50%
income tax rate, the levelized income tax rate is 4.31%.
Annual Capital Charge—
The levelized annual capital charges for a publicly owned electric
utility, as shown in Table 6, are 14.7% of the total investment. The
annual capital charge includes charges for the capital recovery factor,
interim replacements, insurance, and property taxes, State and Federal
income taxes, and credits for investment credits and accelerated deprecia-
tion.
TABLE 6. LEVELIZED ANNUAL CAPITAL CHARGES
FOR REGULATED UTILITY FINANCING
Capital charge, %
Capital recovery factor 10.61
Interim replacements 0.56
Insurance and property taxes 2.50
Levelized income tax 4.31
Investment credit (1.92)
Accelerated depreciation (1.36)
Total 14.70
The annual capital charge is applied to the total capital investment.
It is recognized that land and working capital (except spare parts) are
not depreciable and that provisions must be made at the end of the
economic life of the facility to recover their capital value. In addition,
investment credit and accelerated depreciation credit cannot be taken
for land and working capital (except spare parts). The cumulative
effect of these factors makes an insignificant change in the annual
capital charge rate and is therefore ignored.
Capital Investment Estimates
Capital investment estimates for this study are based on an Upper
Great Plains and Rocky Mountain location and represent projects beginning
in 1981 and ending in 1983. Capital cash flows for a standard project
are assumed to be 25% the first year, 50% the second year, and 25% the
third year of the project life. Capital costs for fixed assets are
projected to mid-1982, which represents the approximate midpoint of the
14
-------
construction expenditure schedule. The estimates in this study are
based on a process description, flowsheet, material balance, and equipment
list. These preliminary-level estimates are considered to have a -20%
to +40% range of accuracy.
The total fixed capital investment consists of direct capital costs
for equipment, building, utilities, service facilities, raw material and
byproduct storage, waste disposal facilities, engineering design and
supervision, construction expense, contractor fees, and contingency.
The total capital investment consists of the total fixed capital invest-
ment plus allowances for startup and modifications, royalties, the cost
of funds during construction, plus the cost of land and working capital.
Direct Capital Investment Process—
Direct capital costs cover process equipment, piping, insulation,
transport lines, foundations, structures, electrical equipment, instru-
mentation, raw material and byproduct storage, site preparation and
excavation, buildings, roads and railroads, trucks, and earthmoving
equipment. Direct investment costs are prepared using the average
annual Chemical Engineering (5) cost indexes and projections as shown in
Table 7.
TABLE 7. COST INDEXES AND PROJECTIONS
Year
Plant
Material
Labor
1978
218.8
240.6
185.9
1979a
240.2
262.5
209.7
1980
259.
286.
226.
a
4
1
5
1981
278.
309.
244.
a
9
0
6
1982a
299.8
333.7
264.2
1983
322.
360.
285.
a
3
4
3
1984
344.
385.
305.
a
9
6
3
a. TVA projections.
b. Same as index in Chemical Engineering
(5) for
"Equip
imei
it,
c.
machinery, supports."
Same as index in Chemical Engineering (5) for "Construction
labor."
The overtime premium for 7% overtime is included in the construction
labor. Appropriate amounts for sales tax and for freight are included
in the process capital costs.
Direct Capital Investment - Utilities, Services and Miscellaneous—
Necessary electrical substations and conduit and steam, process
water, fire and service water, instrument air, chilled water, inert gas,
and compressed air distribution facilities are included in the utilities
investment. These facilities are costed as increments to the facilities
already required by the power plant. Service facilities such as maintenance
15
-------
shops, stores, communications, security, offices, and road and railroad
facilities are estimated on the basis of process requirements. Services,
non-power plant utilities, and miscellaneous costs will normally be in
the range of 4% to 8% of the total process capital depending on the type
of process. A 6% rate is used in this evaluation for both processes.
Indirect Capital Investment—
Indirect capital investment covers engineering design and supervision,
architect and engineering contractor costs, construction costs, contractor
fees, and contingency. Construction facilities (which include costs for
mobile equipment, temporary lighting, construction roads, raw water
supply, construction safety and sanitary facilities) and other similar
expenses incurred during construction are considered as part of construc-
tion expenses and are charged to indirect capital investment.
Listed below are the indirect costs used:
% of direct investment
Engineering design and supervision 7
Architect and engineering contractor 2
Construction expense 16
Contractor fees 5
Total 30
A contingency of 20% is included because projects normally have a higher
likelihood of exceeding rather than underrunning the capital estimate.
While actual projects could properly have both project and process con-
tingencies of varying amounts, depending on the type and developmental
maturity of the process, comparability among processes could be skewed
by the use of different contingencies in the same study.
Other Capital Charges—
Startup and modification allowances are estimated at 8% to 12% of
the total fixed investment depending upon the complexities of the process
being studied. For these processes a midpoint value of 10% of the total
fixed investment was assumed.
Cost of funds during construction is 15.6% of the total fixed
investment for each process. This factor is equivalent to the 10%
weighted cost of capital with 25% of the construction expenditures of
the first year, 50% the second year, and 25% the third year of the
project construction schedule. Expenditures are assumed uniform over
each year. Startup costs are assumed to occur late enough in the project
schedule that there are no charges for the use of money used to pay
startup costs.
16
-------
For both processes, royalty fees of 0.5% of the direct investment
are charged. Land cost is assumed to be $5,000 per acre.
Working capital is the total amount of money invested in raw materials,
supplies, finished and semifinished products, accounts receivable, and
monies on deposit for payment of operating expenses such as salaries,
wages, raw materials, purchases, taxes, and accounts payable. For these
premises, working capital is defined as the equivalent cost of 1 month's
raw material, 1.5 months' conversion cost, and 1.5 months' plant and
administrative overhead costs. In addition, it includes an amount equal
to 3% of the total direct investment to cover spare parts, accounts
receivable, and monies on deposit to pay taxes and accounts payable.
Annual Revenue Requirements
Annual revenue requirements use 1984 costs and are based on 5,500
hours of operation per year at full load. Annual revenue requirements
are divided into direct costs and indirect costs. Both first-year and
levelized annual revenue requirements are determined. Levelized annual
revenue requirements are based on a 10% discount factor and a 6% inflation
rate over the 30-yr life of the power unit. Direct costs consist of raw
materials, labor, utilities, maintenance, and analytical costs. Indirect
costs consist of levelized annual capital charges and overheads.
Direct Costs—
Projected raw material, labor, and utility costs are listed in
Table 8. Unit costs for steam and electricity are based on the assumption
that the required energy is purchased from another source. Unit costs
($/kW, mills/kWh) are calculated on the basis of net power output of the
boiler excluding the electricity consumed by the pollution control
systems. Actually, electrical use by the pollution control equipment
after the ESP will result in a derating of the utility plant for either
a new or a retrofitted unit. To minimize iterative calculations, the
pollution control equipment is charged with purchased electricity instead
of derating the utility plant.
Maintenance costs are estimated as a percentage of the direct
investment, based on unit size and process complexity. For the limestone
slurry process, non-pond maintenance is 8% and pond maintenance is 3%.
For the generic lime spray dryer process, maintenance is 6%.
Indirect Costs—
The levelized annual capital charges consist of a sinking fund
factor, an allowance for interim replacement, property taxes, insurance,
weighted cost of capital, income tax, credits for accelerated depreciation,
and investment credit. The levelized annual capital charge for a regulated
utility, as was shown in Table 6, is 14.7%.
17
-------
TABLE 8. PROJECTED 1984 UNIT COSTS FOR RAW
MATERIALS, LABOR, AND UTILITIES
$/unit
Raw materials
Limestone
Lime
Labor
Operating labor
Analyses
Mobile equipment
Utilities
Q
Process water
Electricity
8.50/ton
102.00/ton
15.00/man-hr
21.00/man-hr
21.00/man-hr
0.14/kgal
0.037/kWh
a. Varies according to process-dependent
water requirements.
Plant and administrative overhead is 60% of conversion costs less
utilities. The plant and administrative overheads include plant services
such as safety, cafeteria, medical, plant protection, janitor, purchasing
personnel, general engineering (excluding maintenance), interplant
communications and transportation, recreational facilities, and the
expenses connected with management activities. Fringe benefits such as
retirement, vacation, dental and medical plans are included in the base
wage rates.
18
-------
PROCESS BACKGROUND AND DESCRIPTION
GENERIC LIME SPRAY DRYER PROCESS
The generic lime spray dryer process (Figure I and Table 9) is a
relatively simple processing system requiring few items of process
equipment. Makeup lime is slurried, atomized into the flue gas stream,
and the resulting waste material is collected along with the fly ash in
the baghouse. The concentration of the lime slurry is adjusted so that
the amount of water injected into the flue gas stream does not saturate
the flue gas. Mist eliminators (a frequent source of operating problems)
are not required. In addition, since the flue gas stream is unsaturated,
the waste material is collected as dry particulate matter.
In this particular application (primarily due to both the relatively
low S02 removal required and the highly alkaline nature of the fly ash),
most of the collected waste material is reslurried and recycled through
the spray dryer. This recycling of waste material increases the lime
utilization in the process and thereby reduces the consumption of this
costly alkali raw material. The waste that is not recycled is trucked
to a landfill for disposal.
Flue gas bypass around the spray dryer is used in this application
because it is more economical to treat part of the flue gas at a higher
S02 removal efficiency than to remove 70% of the S02 from all of the
flue gas. By using flue gas bypass and having hot (-300 F) flue gas
available for reheat, the spray dryer can be operated so that the
treated flue gas more closely approaches the flue gas saturation temper-
ature. As the flue gas approaches saturation temperature, the alkali
droplets retain their moisture longer and increase the liquid-phase
residence time for S02 absorption. This results in a better raw material
utilization (as well as a higher S02 removal efficiency) in the spray
dryer. Although there is an additional capital investment for the flue
gas bypass ductwork, this is offset by both the lower capital investment
for the spray dryers and the lower annual cost for lime.
Process Description
Flue gas from the boiler air heater enters the three operating
trains (the fourth is a spare) of the FGD system through a common plenum.
Most of the flue gas (78%) from the plenum passes directly into the top
of the spray dryers. The rest of the flue gas bypasses the spray dryers
for reheat purposes. The spray dryer contains an atomizing system
19
-------
N3
o
Figure 1. Generic lime spray dryer process. Flow diagram.
-------
TABLE 9. GENERIC LIME SPRAY DRYER PROCESS
MATERIAL BALANCE
1
2
t
.',
',
((
/
fi
")
1°
Stream No.
Total stream. Ib/hr
sft^min at 60°F
Temperature, °F
Pressure, psisi
Rpm
Specific gravity
pH
Undisaolved solids. Z
1
489,700
2
Combustion air
5,119,000
1,131,066
80
3
Combustion air
4,419,000
976,466
535
4
Gas to
econom zer
4,897,000
1,045,000
890
5
Gas to
air neater
4,897,000
1,045,000
705
Stream No,
Description
1
1
'.
'}
/
8
9
10
Total stream, Ib/hr
sft3/min at 6Qf>F
Temperature, °F
Pressure , psig
gpm
Specific gravity
PH
Undissolved solids, %
11
Waste to
recycle
parttculate silo
55,450
12
Makeup water
to recycle
slurry tank
83,150
166
13
Recycle slurry
to spray dryer
138,600
iO
14
Makeup lime
to slaker
3,661
15
Makeup water
to slaker
11,350
23
Stream No.
1
i
'}
it
/
H
4
10
Description
iQtal sueam. Ib/hr
sftVmtn at 6Q°F
Temperature, °F
Pressure , psig
Kpm
Spt'cific gravity
PH
Undissolved solids, %
16
Grit to
landfill
366
17
Lime slurry to
spray dryer
14,650
22.5
18
Dilution water
to spray drver
19,890
60
40
a. Includcs air inleukage Into the
21
-------
designed to spray the lime slurry and a waste recycle slurry perpen-
dicularly to the gas flow in the spray dryer. (The lime slurry and the
waste recycle slurry are combined into a single stream and atomized in
the spray dryer.) The SOX and HC1 in the flue gas react readily with
the lime slurry by the following reactions:
Ca(OH)2 + S02 -> CaS03 4- H20f (5)
Ca(OH)2 + SCL -> CaSO^ + H20t (6)
Ca(OH) + 2HC1 -> CaCl + 2HOt (7)
In addition to these primary reactions, the following secondary reaction
also occurs:
CaS03 + 1/202 -*• CaS04 (8)
The water content of the feedstreams is controlled so that all of the
water fed to the spray dryer evaporates and the mixed calcium salts and
fly ash leave the spray dryer as dry particulate matter entrained in the
flue gas. Since the flue gas is not saturated and contains no liquid
carryover, mist eliminators are not required. The particulate matter-
laden flue gas from thp. bottom of the spray dryer is mixed with the
300°F flue gas which bypassed the spray dryer and is passed to the
baghouse. The baghouse not only removes the fly ash and the calcium-
based particulate matter from the flue gas, but it also significantly
increases the contact time between the calcium-based particulate matter
and the SC>2-containing flue gas. This increased contact time leads to
the additional conversion of both SOX by reactions (5) and (6) and
CaSO-j by reaction (3) . The flue gas from the baghouse passes through an
ID fan and is vented to the stack. The flue gas enters the stack at
about 175 F and, therefore, additional reheat is not required.
The fabric bags in the baghouse are cleaned periodically. The
particulate matter drops into hoppers at the bottom of the baghouse.
Pneumatic conveyors move the particulate matter to either the recycle
storage silos or the waste storage bins. Waste solids from the silo are
reslurried with makeup water and recycled through the spray dryer. The
waste storage bin is emptied into trucks for transport to a landfill.
Bulk shipments of pebble lime are received by rail and sent to the
storage silo. The lime is periodically moved to intermediate storage
bins from which process requirements are removed. The pebble lime from
the bins is slaked with makeup water and pumped as a 22.5% slurry to the
lime slurry tank. This makeup slurry is pumped to the spray dryer as
needed.
22
-------
Analysis of Processing Subsections
To facilitate cost determinations and comparisons, the lime process
is divided into seven processing sections and the processing equipment
is assigned to the appropriate section. The equipment list, giving the
description and cost of each equipment item by section, is shown in
Table 10. These costs do not include the investment required for founda-
tions, structures, electrical components, piping, instruments and controls,
etc. Each of these processing sections is described in more detail
below.
Material Handling—
This and the following section, feed preparation, compose the raw
material receiving and preparation section. The material handling
section includes all of the equipment to receive lime by rail and to
maintain a supply of lime to the weigh feeders. It includes a lime
storage silo with a 30-day capacity and two lime feed bins each having a
12-hr capacity.
Feed Preparation—
The feed preparation sections include the equipment necessary to
convert the makeup lime into slurry for S02 absorption. Two trains of
lime preparation equipment (feeders, slakers, tanks, and agitators) are
used. Each train is sized to handle 50% of the full load capacity. A
slurry feed tank with a 4-hr capacity is provided.
Gas Handling—
Included in this area is an inlet plenum interconnecting the flue
gas ducts which feed the scrubber trains. It also includes the bypass
ducting around the spray dryers. Four ID fans are provided between the
baghouse and the stack to compensate for the pressure drop through the
FGD system.
S02 Absorption—
Four spray dryers are provided (three operating and one spare);
each is sized to handle one-third of the total flue gas volume.
Particulate Removal—
A single baghouse containing 28 compartments and the associated
equipment is provided.
Particulate Handling and Recycle—
A single train of equipment to store, reslurry, and recycle the
waste material is provided. Two particulate storage bins are included
to provide a 24-hr capacity for waste material to be landfilled.
Waste Disposal—
This section contains no processing equipment. It includes trucks
to transport the waste absorbent to the landfill and earthmoving equipment
23
-------
TABLE 10. GENERIC LIME SPRAY DRYER PROCESS
BASE-CASE EQUIPMENT LIST, DESCRIPTION, AND COST
Area
1 — Material Handling
Item No. Description
Total
material
cost,
1982 $
Total
labor
cost,
1982 $
1. Conveyor, lime 1
unloading (enclosed)
2. Elevator, storage 1
silo
3. Silo, lime
storage
Vibrators
4. Conveyor, live
lime feed
5. Elevator, live
lime feed
6. Bin, lime feed
Belt, 24 in. x 1,500 ft 390,000 242,800
long, 30 hp, 100 tons/hr,
200 ft/min
Continuous bucket, 16 in. 33,600 3,300
x 8 in. x 11-3/4 in., 75
ft lift, 15 hp, 100 tons/hr,
160 ft/min
40 ft dia x 50 ft straight 65,200 194,300
side, 62,800 ft3, 60°
slope, carbon steel
Bin activator, 10 ft dia 14,000 1,300
Belt, 14 in. x 100 ft 23,800 7,600
long, 2 hp, 16 tons/hr,
100 ft/min
Continuous bucket, 8 in. 49,300 4,000
x 5-1/2 in. x 7-3/4 in.,
35 ft lift, 2 hp, 16 tons/
hr, 150 ft/min
11 ft dia x 12 ft straight 10,600 28,200
side, 1,140 ft3> 60° slope,
w/cover, carbon steel
7. Dust collecting
system
Subtotal
Bag filter, polypropylene
bag, 2,200 ft3/min, 7-1/2
hp (1/2 cost in feed prepa-
ration area)
3,900
600
590,400 482,100
(continued)
24
-------
TABLE 10 (continued)
Area 2 — Feed Preparation
1.
2.
3.
4.
Item
Feeder, lime
bin discharge
Feeder, slaker
Slaker
Tank, slaker
No. Description
2 Vibrating, 3-1/2 hp, carbon
steel
2 Screw, 12 in. dia x 12 ft long,
1 hp, 2 tons/hr
2 5 hp slaker, 1 hp classifier,
1.0 ton/hr
2 6 ft dia x 8 ft high, 1,700
Total
material
cost,
1982 $
8,400
6,600
72,500
5,400
Total
labor
cost,
1982 $
800
400
23,900
7,500
product
gal, open top, four 6 in.
baffles, agitator supports,
carbon steel, neoprene lined
5. Agitator, slaker
product tank
6. Pump, slaker
product tank
7. Tank, slurry
feed
2 turbines, 24 in. dia,
3 hp, neoprene coated
Centrifugal, 40 gpm, 50 ft
head, 1-1/2 hp, carbon steel,
neoprene lined
(2 operating, 1 spare)
10 ft dia x 12 ft high, 7,100
gal, open top, four 10 in.
baffles, agitator supports,
carbon steel, neoprene lined
15,800 1,800
5,300 2,300
6,500 9,500
8. Agitator, slurry
feed tank
9. Pump, slurry
feed tank
10. Dust collecting
system
Subtotal
40 in. dia, 7-1/2 hp, neoprene
coated
Centrifugal, 40 gpm, 200 ft
head, 5 hp, carbon steel,
neoprene lined
(3 operating, 5 spare)
Bag filter, polypropylene bag,
2,200 ft3/min, 7-1/2 hp, (1/2
cost in material handling area)
15,300
40,000
3,900
1,300
6,000
600
179,700 54,100
(continued)
25
-------
TABLE 10 (continued)
Area 3—-Gas Handling
Item
No.
Description
Total
material
cost,
1982 $
1. Fan
Induced draft, 382,000
aft3/min, 12 in. static
head, 875 rpm, 1,250 hp,
fluid drive, double width,
double inlet (4 operating)
Subtotal
3 rotary atomizers, carbon
steel, (3 operating, 1 spare)
Subtotal
Total
labor
cost,
1982 $
1,583.600 99.600
1.583.600 99,600
Area 4 — S0? Absorption
Item No. Description
1. Spray dryer 4 48 ft dia x 54 ft high, with
Total
material
cost,
1982 $
4,324,000
Total
labor
cost,
1982 $
548.000
4,324.000 548,000
Area 5—Particulate Removal
Item
No.
Description
Total Total
material labor
cost, cost,
1982 $ 1982 $
1. Baghouse 1
Subtotal
Automatic fabric filter, 28 compart- 8,262,000^ 2,871.100
ments, 2.5 air-to-cloth ratio
8.262.000 2.871.100
(continued)
26
-------
TABLE 10 (continued)
Area 6 — Particulate Handling
Item No.
and Recycle
Description
Total
material
cost,
1982 $
Total
labor
cost,
1982 $
1. Conveyor, particu- 1 Pneumatic, pressure-vacuum,
late feed to bin 250 hp
2. Bin, particulate
storage
2 24 ft dia x 25 ft straight
side, 11,300 ft3, 60° slope,
w/cover, carbon steel
243,100
75,600
43,600 131,400
3.
Vibrator 2
Silo, particulate 2
recycle
Bin activator, 10 ft dia
25 ft dia x 30 ft straight
side, 14,700 ft3f 60° slope,
w/cover, carbon steel
18,600 2,500
51,200 149,700
4. Feeder, particu-
late
5. Feeder, recycle
slurry tank
6. Tank, recycle
slurry
Vibrating, 3-1/2 hp, carbon
steel
Screw, 12 in. dia x 12 ft
long, 5 hp, 50 tons/hr
21 ft dia x 23 ft high,
55,400 gal, open top, four
21 in. baffles, agitator
supports, carbon steel, neo-
prene lined
8,400 800
30,800 4,500
25,700 38,700
7. Agitator, recycle
slurry tank
8. Pump, recycle
slurry feed
Subtotal
84 in. dia, 30 hp, neoprene
coated
Centrifugal, 80 gpm, 200 ft
head, 10 hp, carbon steel,
neoprene lined
(3 operating, 5 spare)
42,100
65.400
2,600
7,600
528.900 413.400
Basis: Most equipment cost estimates are based on informal vendor quotes and
TVA information. The only exception is the cost for the spray dryers
which is based on information supplied by the vendor.
These costs represent equipment costs only. Costs for piping, elec-
trical equipment, instruments, foundations, and other installation
costs are not included. The differences in area costs between the
equipment list and the capital summary sheets are due to these installa-
tion costs. 27
-------
to distribute the waste evenly throughout the landfill. Therefore,
these costs are not shown in the equipment list, but rather they are
listed as a direct investment component of the capital investment.
LIMESTONE SLURRY PROCESS
The limestone slurry process (Figure 2 and Table 11) is also a
relatively simple processing system requiring few items of process
equipment. Although not usually considered as part of the FGD system, a
high-efficiency (99.8%) ESP has been included in the limestone slurry
process upstream of the FGD system. This change in the typical economic
analysis of the limestone slurry process (i.e., including the cost of
the ESP's) is necessary to provide comparability with the generic lime
spray dryer process.
Another significant design change for the limestone slurry process
is the inclusion of partial flue gas bypass around the scrubber. Since
only 70% SC>2 removal is required in this low-sulfur coal application, it
was considered more economical to design the FGD system for 90% S02
removal and treat only enough flue gas to meet the required S02 reduction.
Under these conditions sufficient heat is available from the bypassed
gas to eliminate the need for additional reheat.
Otherwise the limestone slurry process is of conventional design.
The makeup limestone is ground, slurried, and added as needed to maintain
a 15% solids slurry recirculating through the scrubber. A purge stream
is bled off the absorber loop and is pumped to the disposal pond. The
pond supernate is recycled and reused in the process. The fly ash from
the ESP is trucked to and disposed of in the pond.
Process Description
The flue gas from the boiler air heater passes through both the
high-efficiency ESP and the power plant ID fans before entering a common
plenum. This common plenum distributes the gas to four trains of FD
booster fans and absorbers. (Three of these scrubber trains are operating
and one is a spare.) These FD booster fans are provided downstream of
the plenum to compensate for the pressure drop in the FGD system.
Approximately 28% of the 300°F flue gas from the booster fan bypasses
the venturi/spray tower absorbers and enters the ducts downstream from
the absorbers for reheat purposes. The remaining flue gas enters a
venturi absorber where the flue gas, in contact with recirculated limestone
slurry, is adiabatically cooled and saturated. This cooled flue gas
enters the spray tower absorbers and passes countercurrently to the
recirculating 15% solids limestone slurry which absorbs the SOX. The
absorbers are equipped with chevron-type mist eliminators. Absorber
outlet gas is heated from 130°F to 175 F before entering the stack by
mixing with the bypassed flue gas.
28
-------
BOILER
to
VO
," ELECTROSTATIC
'ECONOMIZER! PRECIPITATOR
FD
FAN
COAL
POND SUPERNATE
RETURN
TO WASTE
DISPOSAL POND
Figure 2. Limestone slurry process. Flow diagram.
-------
TABLE 11. LIMESTONE SLURRY PROCESS
MATERIAL BALANCE
Description
I
I
\
'.
6
7
H
9
|0
Total stream, Ib/hr
«fr3/mln at 60<>F
Temperature. °F
pressure. osiff
Soecific Rravltv
oH
Undissolved solids, 7.
1
Coal to boiler
489,700
2
Combustion air
to air heater
5, 119,000
1,131,000
80
3
Combustion air
to boiler
4 ^4 11,000
976,400
535
4
Gas to
economizer
4,897,000
1,045,000
896
5
Gas Co
air heater
4,897,000
1.045.000
7S5
L
k
')
ft
/
H
9
Iff
Description
/rain at 60OF
Pressure, psift
pom
Specific ftravity
uH
Undissolved solids, X
6
Gas to ESP
] ,700.000
7
863.200
8
Gas from
922.300
9
Gas to stack
1.259.000
10
to venturi
20.930
15
1
;
i
4
'>
;
H
9
10
§tream No.
Description
Total stream, Ib/hr
sft'/min at 60OF
Temperature, QV
Pressure, psla
uH
Undisaolved solids. £
11
Makeup water
to scrubber
170,100
340
12
Reclrculated
slurry to
absorber
23,050,000
130
41.860
15
13
Slurry to pond
48,810
89
15
14
Pond supernace
to reclrcutatlon
tank
26,690
53
15
limestone to
weigh belts
5,728
|
s
fl
/
8
4
IU
J t ream No.
Description
Total stream, Ib/hr
sftVnln at 60op
prflflfl.Mrp- psig
sB6Cific gravity
oH
Unrflosnlved solids. %
16
Pond supernate
to wee
ball mill
3,820
8
17
Mills product
tank feed
9,546
12
60
18
Makeup slurry
to recirculat ion
tank
9,546
12
60
30
-------
A bleedstream from the recirculation tank is fed to the pond feed
tank from which it is pumped to the onsite pond. The solids in the
slurry settle to form a sludge containing approximately 40% solids. The
pond supernate is recycled to the wet ball mills and the absorber recir-
culation tank.
Makeup limestone is received by rail and stored in a pile onsite.
The limestone is removed from the pile and fed first to gyratory crushers
and then to ball mills where it is wet ground to 70% minus 200 mesh.
The effluent from the ball mill is stored as a 60% solids slurry, first
in the ball mill product tank and then in the slurry feed tank. This
makeup limestone slurry is pumped to the absorber recirculation tank
where it is combined with scrubber effluent slurry and recycle pond
water to maintain a 15% solids content in the recirculating slurry.
Analysis of Processing Subsections
To facilitate cost determinations and comparisons, the limestone
slurry process is divided into six processing sections and the processing
equipment is assigned to the appropriate section. The equipment list,
giving the description and cost of each equipment item by section, is
shown in Table 12. These costs do not include the investment required
for foundations, structures, electrical components, piping, instruments,
and controls, etc. Each of these processing sections is described
below.
Material Handling—
This area includes all of the facilities needed for receiving the
raw limestone, areas for a storage stockpile sufficient for 30 days at
normal operating conditions, and an in-process limestone storage for 24
hours.
Feed Preparation—
A single train of gyratory crushers and wet ball mills to convert
the raw limestone to a 70% minus 200 mesh, 60% solids slurry is included
in this area. It also contains a product storage tank with capacity
equal to an 8-hr supply of makeup slurry.
Particulate Removal—
Four high-efficiency ESP units (99.8% removal) are included in this
area. These ESP's are sized for a low-sulfur, western coal application.
Gas Handling—
Included in this area is one inlet flue gas plenum interconnecting
the four flue gas ducts which feed the absorbers and four FD fans. Also
included are the FD fans and the bypass ducting around the absorbers.
Each of these FD fans is sized to handle one-third of the total flue gas
volume and to compensate for the pressure drop in the FGD system.
31
-------
TABLE 12. LIMESTONE SLURRY PROCESS
BASE-CASE EQUIPMENT LIST, DESCRIPTION, AND COST
Area 1 — Materials Handling
1.
2.
3.
4.
Item
Mobile equipment
Hopper, reclaim
Feeder, live
limestone storage
Pump , tunnel sump
No.
1
1
1
2
Description
Bucket tractor
7 ft x 4-1/4 ft x 2 ft
deep, carbon steel
Vibrating pan, 3.5 hp
Vertical, 60 gpm, 70 ft head,
Total
material
cost,
1982 $
60,800
700
15,400
4,300
Total
labor
cost ,
1982 $
—
1,300
2,700
1,100
5. Conveyor, live
limestone feed
6. Conveyor, live
limestone feed
(incline)
7. Elevator, live
limestone feed
8. Bin, crusher 1
feed
9. Dust collecting 1
system
Subtotal
5 hp,carbon steel, neoprene
lined
(1 operating, 1 spare)
Belt, 30 in. wide x 100 ft
long, 2 hp, 100 tons/hr,
60 ft/min
Belt, 30 in. wide x 190
ft long, 40 hp, 35 ft lift,
100 tons/hr, 60 ft/min
Continuous bucket, 12 in. x
8 in. x 11-3/4 in., 75 hp,
90 ft lift, 100 tons/hr,
160 ft/min
13 ft dia x 21 ft high, w/
cover, carbon steel
Bag filter, polypropylene
bag, 2,200 aft3/min, 7-1/2
hp, automatic shaker system
34,300
102,800
6,900
6,700
6,300
48,000 20,300
2,400
14,500
18,100
279,900 66.700
(continued)
32
-------
TABLE 12 (continued)
Area
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
2 — Feed Preparation
Item No.
Feeder , crusher 1
Crusher 1
Ball mill 1
Tank, mills 1
product
Agitator, mills 1
product tank
Pump, mills 2
product tank
Tank, slurry 1
feed
Agitator, slurry 1
feed tank
Pump, slurry 6
feed tank
Dust collecting 1
system
Subtotal
Total
material
cost,
Description 1982 $
Weigh belt, 18 in. wide x 14 23,100
ft long, 2 hp, 3.0 tons/hr
Gyratory, 0 x 1-1/2 to 3/4 in., 67,700
75 hp, 3.0 tons/hr
Wet, open system, 100 hp, 174,400
3.0 tons/hr
10 ft dia x 10 ft high, 5,500 6,200
gal, open top, four 10 in.
baffles, agitator supports,
carbon steel, flakeglass lined
36 in. dia, 10 hp, neoprene 10,500
coated
Centrifugal, 12 gpm, 60 ft 6,200
head, 1 hp, carbon steel,
neoprene lined
(1 operating, 1 spare)
11 ft dia x 11 ft high, 7,500 4,300
gal, open top, four 11 in.
baffles, agitator supports,
carbon steel, flakeglass lined
44 in. dia, 15 hp, neoprene 11,000
coated
Centrifugal, 4 gpm, 60 ft 17,700
head, 1/4 hp, carbon steel,
neoprene lined
(3 operating, 3 spare)
Bag filter, polypropylene 6,700
bag, 2,200 aft3/min, 7-1/2
hp, automatic shaker system
328,200
(continued)
33
Total
labor
cost,
1982 $
1,800
7,600
17,800
11,000
500
1,400
10,500
900
4,300
18,100
73,900
-------
TABLE 12 (continued)
Area 3—Particulate Removal
Item
No.
Description
Total Total
material labor
cost, cost,
1982 $ 1982 $
1. ESP
4 99.8% removal efficiency
SCA = 700
2. Conveyor, flyash 1 Pneumatic, pressure-vacuum,
to particulate 75 hp
bin
3. Bin, particulate 2 25 ft dia x 27 ft high,
w/cover, carbon steel
8,020,000 4,010,000
109,800 69,300
39,000 108,600
4. Vibrator
Subtotal
2 Bin activator, 10 ft dia
28,000 2,600
Area 4 — Gas Handling
Item No. Description
1. Fans 4 Forced draft, 421,000
Total
material
cost,
1982 $
2,276,200
Total
labor
cost,
1982 $
147,500
890 rpm, 2,250 hp, fluid
drive, double width, double
inlet
(3 operating, 1 spare)
Subtotal
2.276.200 147.500
Area 5 — SO? Absorption
Item No.
1. Venturi absorber 4
Description
L/G = 20, pressure drop = 9 in.
H20 (3 operating, 1 spare)
(continued)
34
Total
material
cost,
1982 $
632,900
Total
cost,
labor
1982 $
86,000
-------
TABLE 12 (continued)
Area 5 (continued)
Item
No.
Description
Total Total
material labor
cost, cost,
1982 $ 1982 $
2. Tank, venturi
hold
3. Agitator,
venturi hold
tank
4. Pumps, venturi
recycle
5. S02 absorber
6. Tank, recircula-
tion
7. Agitator, recir-
culation tank
8. Pump, slurry
recirculation
12
15-1/2 ft dia x 31-1/2 ft
high, 44,500 gal, open top,
four 15-1/2 in. wide baffles,
agitator supports, carbon
steel, flakeglass lined
(3 operating, 1 spare)
62 in. dia, 40 hp, neoprene
coated
(3 operating, 1 spare)
Centrifugal, 7,000 gpm, 100
ft head, 350 hp, carbon steel,
neoprene lined
(3 operating, 5 spare)
Spray tower, 34 ft long x 17
ft wide x 40 ft high, 1/4 in.
carbon steel, neoprene lining;
FRP spray headers, 316 stain-
less steel chevron vane entrain-
ment separator and nozzles
(3 operating, 1 spare)
31-1/2 ft dia x 31-1/2 ft high,
184,200 gal, open top, four
31-1/2 in. wide baffles, agi-
tator supports, carbon steel,
flakeglass lined
(3 operating, 1 spare)
124 in. dia, 60 hp, neoprene
coated
(3 operating, 1 spare)
Centrifugal, 7,000 gpm, 100
ft head, 350 hp, carbon steel,
neoprene lined
(6 operating, 6 spare)
63,700 156,300
96,900 32,700
421,000 37,000
3,485,000 401,200
158,400 354,500
293,300 99,100
631,500 55,600
(continued)
35
-------
TABLE 12 (continued)
Area 5 (continued)
9.
10.
Item No .
Pump , makeup 2
water
Soot blowers 44
Subtotal
Description
Centrifugal, 2,620 gpm, 200
ft head, 250 hp, carbon
steel
(1 operating, 1 spare)
Air, retractable
Total
material
cost,
1982 $
25,600
377,100
6,185,400
Area 6 — Solids Disposal
1.
2.
3.
4.
Item No.
Tank, pond 1
feed
Agitator, pond 1
feed tank
Pumps , pond feed 4
Pumps , pond 2
return
Subtotal
Description
15-1/2 ft dia x 31-1/2 ft high
44,500 gal, open top, agitator
supports, four 15-1/2 in.
baffles, carbon steel, flake-
glass lined
2 turbines, 52 in. dia, 40 hp,
neoprene coated
Centrifugal, 89 gpm, 130 ft
head, 3 hp, carbon steel,
neoprene lined
(2 operating, 2 spare)
Centrifugal, 127 gpm, 200 ft
head, 10 hp , carbon steel,
neoprene lined
(1 operating, 1 spare)
Total
material
cost,
1982 $
15,900
21,700
18,200
6,200
62,000
Total
labor
cost,
1982 $
2,700
318,700
1,543,800
Total
labor
cost,
1982 $
39,100
1,800
3,900
700
45,500
Basis: Most equipment cost estimates are based on informal vendor quotes and
TVA information.
These costs represent equipment costs only. Costs for piping, elec-
trical equipment, instruments, foundations, and other installation
costs are not included. The differences in area costs between the
equipment list and the capital summary sheets are due to these
installation costs.
36
-------
SiOo Absorption—
Four trains (three operating, one spare) of venturi/spray tower
absorbers with mist eliminators, recirculation tanks, and recirculating
pumps are included. Each absorber train is sized to handle one-third of
the total flue gas volume.
Solids Disposal—
Included are one pond feed tank with agitator, pond feed and pond
return pumps, and mobile equipment (trucks) to move the fly ash from the
ESP to the sludge pond.
37
-------
ECONOMIC EVALUATION AND COMPARISON
Based on the power plant, process design, economic premises, and
the specific process equipment for each process described in the previous
sections, preliminary capital investment, first-year revenue requirements,
and levelized annual revenue requirements were prepared for the economic
evaluation and comparison of the generic lime spray dryer process and a
conventional limestone slurry process.
Both first-year and levelized annual revenue requirements are cal-
culated. First-year annual revenue requirements are useful for comparing
the relative cost differences between processes for their first year of
operation, and they are an indicator of the magnitude of the annual
revenue requirements. However, these first-year annual revenue require-
ments do not represent the actual cost of operating the plant since they
do not consider either the time-value of money or the inflationary
pressures over the life of the plant. In order to reflect these costs,
a levelizing factor (1.886) is applied to the first-year annual revenue
requirements to give a levelized annual revenue requirement. This
levelizing factor is based on a 10% discount factor and a 6% inflation
rate over the 30-yr life of the power unit.
Sensitivity analyses have also been performed to evaluate the
effects of varying the raw material price and stoichiometry for the
generic lime spray dryer process. An alternate case involving sludge
fixation for the limestone slurry process has also been included.
Even though the generic lime spray dryer process, as described and
costed, was assumed to be proven technology, the current status of
development does not fully justify this assumption since none of the
lime spray dryer processes have been operated on a commercial, coal-
fired boiler. However, for TVA cost estimation purposes each system is
assumed to be proven technology.
ACCURACY OF ESTIMATES
The accuracy associated with these preliminary cost estimates,
i.e., -20%, +40%, is defined as the relationship between the estimated
costs and what the actual installed costs for the process might be. The
accuracy assigned to a cost estimate is empirical and not related to
variabilities in a statistical sense, but rather, it depends on both the
amount and the quality of the technical data available. Accuracy ranges
reflect the numerous uncertainties surrounding estimates made using
simplifying assumptions. For example, in a preliminary-level estimate
38
-------
in which only a flowsheet, material balance, and an equipment list are
available—and all other indirect investments are factored—the uncertainty
surrounding the investment is much greater than a definitive-level
estimate where quantities and costs for piping, electrical equipment,
instruments, etc., are calculated rather than factored. Therefore when
estimating the preliminary-level capital investment for a particular
process for a particular installation the uncertainty surrounding the
costs would be -20%, +40%.
However, when comparing the preliminary-level costs for two competing
process technologies, many of the same simplifying assumptions are made
for each of the processes and therefore the comparability is much greater
than the accuracy of the estimates. When directly comparing two similar
level estimates, the uncertainty ranges associated with the compared
costs are estimated at only llO%.
CAPITAL INVESTMENT
Generic Lime Spray Dryer Process
The total capital investment for the generic lime spray dryer
process is $66.2M ($132/kW) in mid-1982 dollars. This total cost can be
broken down into the various investment cost categories as shown in
Table 13. The total direct investment, which includes processing equip-
ment, piping, etc., accounts for about 49% of the total capital investment.
The indirect investments such as engineering design and supervision,
architect and engineering contractor, construction expense, contractor
fees, and project contingency make up about 28% of the total capital
investment. The various other capital charges (allowance for startup
and modifications, interest during construction, royalties, land, and
working capital) make up the remaining 23%.
The total direct investment for the generic lime spray dryer process
can be further subdivided into the various processing areas. The major
investment areas are the particulate matter removal, gas handling, and
S02 absorption areas. These areas account for most (78%) of the total
direct investment.
Major indirect investments are project contingency at $8.4M and the
construction expense at $5.2M. Engineering design and supervision, con-
tractor fees, and architect and engineering contractor expense contribute
significantly less at $2.3M, $1.6M, and $0.7M respectively.
Other capital charges, including allowance for startup and modifi-
cations, interest during construction, royalties, land, and working
capital, account for $15.5M of the total capital investment. The allow-
ance for startup and modifications and interest during construction
contributed most to the other capital charges. Land and royalties were
relatively insignificant at $0.5M and $0.2M.
39
-------
TABLE 13. GENERIC LIME SPRAY DRYER PROCESS
TOTAL CAPITAL INVESTMENT
(500-MW new coal-fired power unit, 0.7% S in coal;
70% S02 removal; onsite solids disposal)
Investment, k$
Direct Investment
Material handling 2,443
Feed preparation 599
Gas handling 7,190
S02 absorption 7,173
Particulate removal 11,133
Particulate handling and recycle 1,425
Solids disposal 379
Total process capital 30,342
Services, utilities, and miscellaneous 1,821
Total direct investment excluding disposal field preparation 32,163
Disposal field preparation 321
Total direct investment 32,484
Indirect Investment
Engineering design and supervision
Architect and engineering contractor
Construction expense
Contractor fees
Contingency
Total fixed investment 50,675
Other Capital Charges
Allowance for startup and modifications
Interest during construction
Royalties
Land
Working capital
Total capital investment
Dollars of total capital per kW of generation capacity
Basis
Upper Midwest plant location represents project beginning mid-1980, ending
mid-1983. Average cost basis for scaling, mid-1982.
Minimum in-process storage, redundant scrubber train, and pumps are spared.
Disposal area located one mile from power plant.
FGD process investment begins at boiler air heater exit. Boiler plenum and
stack excluded.
Only nominal construction overtime included.
40
-------
Limestone Slurry Process
The total capital investment for the base-case application of the
limestone slurry process (a combined particulate-limestone FGD system)
is $93.2M ($186/kW) in mid-1982 dollars, as shown in Table 14.
The direct investment for the limestone slurry process can be
further subdivided into the various processing areas. SC>2 absorption,
particulate matter removal, and gas handling account for nearly 79% of
the total direct investment. The waste disposal pond construction
represents about 8% of the total direct investment.
The major indirect investments are project contingency ($11.9M),
construction expense ($7.3M), contractor fees ($2.3M), and engineering
design and supervision ($3.2M). Architect and engineering contractor
costs are significantly less ($0.9M).
The remaining $22.OM of the total capital investment is other
capital charges. The allowance for startup and modifications and interest
during construction together contribute nearly 20% of the total capital
investment and make up 83% of the other capital charges. Royalties,
land, and working capital are $0.2M, $0.9M, and $2.6M respectively.
Comparison
The total direct investment and the total capital investment for
the two FGD systems are shown in Table 15. The generic lime spray dryer
process is substantially (29%) less capital intensive than a limestone
slurry process.
TABLE 15. BASE-CASE TOTAL DIRECT INVESTMENTS
AND TOTAL CAPITAL INVESTMENTS
Total direct Total capital
investment investment
Process
Generic lime spray dryer
Limestone slurry
M$
32.5
45.7
$/kW
65.0
91.3
M$
66.3
93.2
$/kW
132.6
186.4
The major investment differences between the generic lime spray
dryer process and the limestone slurry process are in the S02 absorption,
particulate matter removal, solids disposal equipment, and the waste
disposal area preparation as shown in Table 16. With the exception of
the investment for the material handling and feed preparation areas, the
limestone slurry costs are higher than the costs for the corresponding
areas in the generic lime spray dryer process. The lower costs for the
generic lime spray dryer process in the other areas are due primarily to
the use of the spray dryer. The spray dryer technology eliminates the
41
-------
TABLE 14. LIMESTONE SLURRY PROCESS
TOTAL CAPITAL INVESTMENT
(500-MW new coal-fired power unit, 0.7% S in coal;
70% S02 removal; onsite solids disposal)
Investment, k$
Direct Investment
Material handling 919
Feed preparation 1,071
Particulate removal 12,395
Gas handling 9,924
SO absorption 13,734
Solids disposal 1,453
Total process capital 39,496
Services, utilities, and miscellaneous 2,370
Total direct investment excluding pond construction 41,866
Pond construction 3,793
Total direct investment 45,659
Indirect Investment
Engineering design and supervision 3,]96
Architect and engineering contractor 913
Construction expense 7,305
Contractor fees 2,283
Contingency 11,871
Total fixed investment 71,227
Other Capital Charges
Allowance for startup and modifications 7,123
Interest during construction 11,111
Royalties 228
Land 910
Working capital 2,590
Total capital investment 93,189
Dollars of total capital per kW of generation capacity 186.38
Basis
Upper Midwest plant location represents project beginning mid-1980,
ending mid-1983. Average cost basis for scaling, mid-1982.
Minimum in-process storage, redundant scrubber train, pumps are spared.
Disposal pond located one mile from power plant.
FGD process investment begins at boiler air heater exit. Boiler
plenum and stack excluded.
Only nominal construction overtime included.
A 2
-------
need for slurry recirculating tanks and pumps and mist eliminators in
the S02 absorption area and the thickeners and filtration equipment in
the solids disposal area. The higher land and disposal area preparation
costs for the limestone process are due to both the type of disposal
(pond versus landfill) and the nature of the settled sludge in the pond
(i.e., the sludge in the pond is only 40% solids as compared to a dry
product going to the landfill in the generic lime spray dryer process).
TABLE 16. SUMMARY OF THE TOTAL CAPITAL INVESTMENTS
Investment area
Material handling
Feed preparation
Gas handling
S02 absorption
Particulate removal
Particulate handling
and recycle
Solids disposal
Disposal area preparation
Land
All other capital costs
Total capital investment
Total cost,
Generic lime
spray dryer
process
2,443
599
7,190
7,173
11,133
1,425
379
321
515
34,993
66,171
, k$
Limestone
slurry
process
919
1,071
9,924
13,734
12,395
-
1,453
3,793
910
48,910
93,189
Basis:
TVA design and economic premises.
ANNUAL REVENUE REQUIREMENTS
Generic Lime Spray Dryer Process
The first-year annual revenue requirements for the generic lime
spray dryer process as applied to the previously described base case are
$17.04M in 1984 dollars as shown in Table 17. This corresponds to a
first-year unit revenue requirement of 6.20 mills/kWh. Equivalent
levelized annual revenue requirements for the generic lime spray dryer
process are $23.52M, or 8.55 mills/kWh.
Annual direct costs (including raw material and conversion costs)
are $5.52M or slightly more than 32% of the total first-year annual
revenue requirements. Indirect costs, primarily capital charges but
also including overhead costs, account for the remaining 68%.
The major direct costs are maintenance ($1.9M), electricity ($1.5M)
and lime ($1.0M). Together these three items account for 26% of the
first-year annual revenue requirements. The other major annual costs
are the levelized capital charges of $9.7M and overheads of $1.8M or
57.1% and 10.5% of the total first-year annual revenue requirements
respectively.
-------
TABLE 17. GENERIC LIME SPRAY DRYER PROCESS
ANNUAL REVENUE REQUIREMENTS
(500-MW new coal-fired power unit, 0.7% S in coal;
70% S02 removal; onsite solids disposal)
Annual
quantity
Unit
cost, $
Total
annual
cost, $
Direct Costs - First-Year
Raw materials
Lime
Total raw materials cost
Conversion costs
Operating labor and supervision
FGD
Solids disposal
Utilities
Process water
Electricity
Maintenance
Labor and material
Analyses
Waste disposal operation
Total conversion costs
Total direct costs
10,068 tons
25,400 man-hr
27,040 man-hr
74,440 kgal
40,151,000 kWh
4,160 man-hr
122,500 tons
102.00/ton
15.00/man-hr
21.00/man-hr
0.14/kgal
0.037/kWh
21.00/man-hr
0.15/ton
1,026.900
1,026,900
381,000
567,800
10,400
1,485,600
1,939,400
87,400
18,400
4,490,000
5,516,900
Indirect Costs - First-Year
Overheads
Plant and administrative (60% of conversion
costs less utilities)
Total first-year operating and maintenance costs
Levelized capital charges (14.7% of total capital
investment)
Total first-year annual revenue requirements
Levelized first-year operating and maintenance
costs (1.886 first-year 0 and M)
Levelized annual revenue requirements
M$ Mills/kWh
First-year annual revenue requirements 17.04 6.20
Levelized annual revenue requirements 23.52 8.55
1,796,400
7,313,300
9.727.100
17,040,400
11.792.900
23,520,000
Basis
Upper Midwest plant location, 1984 revenue requirements.
Remaining life of power plant, 30 years.
Power unit on-stream time, 5,500 hr/yr.
Coal burned, 1,347,000 tons/yr, 9,500 Btu/kWh.
Total direct investment, $32,484,000; total fixed investment, $50,675,000; and total capital
investment, $66,171,000.
44
-------
Limestone Slurry Process
The first-year annual revenue requirements for the limestone slurry
process are $23.50 as shown in Table 18. This corresponds to a first-
year unit revenue requirement of 8.55 mills/kWh. Equivalent levelized
annual revenue requirements are $32.19M or 11.71 mills/kWh.
Annual direct costs for raw materials, labor, utilities, and main-
tenance are $6.8M, or only 29% of the first-year revenue requirements.
Indirect costs, primarily for capital charges but also including over-
head costs, account for the remaining 71%.
Raw material costs for the limestone slurry process are about
$0.1M. The conversion costs are nearly $5.9M, with the major costs
being maintenance and electricity at $3.5M and $1.8M respectively. As
would be expected, the levelized capital charge at $13.7M was the major
annual expense, representing 58% of the total first-year annual revenue
requirements.
Comparison
The first-year and the levelized annual revenue requirements for
each of the FGD processes are shown in Table 19. The generic lime spray
dryer process is approximately 27% lower in cost (6.20 mills/kWh versus
8.55 mills/kWh) than the limestone slurry process in terms of both
first-year costs and levelized annual revenue requirements.
TABLE 19. BASE-CASE TOTAL FIRST-YEAR
AND LEVELIZED ANNUAL REVENUE REQUIREMENTS
Total first-year Levelized annual
revenue requirements
Process
Generic lime spray dryer
Limestone slurry
M$
17.04
23.50
Mills/kWh
6.20
8.55
M$
23.52
32.19
Mills/kWh
8.55
11.71
Table 20 compares the various component costs of the first-year
revenue requirements for each process. The major cost difference
between the processes is the cost for capital charges, maintenance, raw
materials, and overheads (primarily because of the differences in main-
tenance costs). The $0.7M difference in raw material costs between the
limestone slurry process and generic lime spray dryer process (limestone
is much cheaper than lime) is essentially cancelled by the higher capital
charges of the limestone slurry process. Utility costs (electricity and
process water) are about the same for both processes although electrical
costs are slightly higher for the limestone slurry process.
45
-------
TABLE 18. LIMESTONE SLURRY PROCESS
ANNUAL REVENUE REQUIREMENTS
(500-MW new coal-fired power unit, 0.7% S in coal;
70% S02 removal; onsite solids disposal)
Direct Costs - First-Year
Raw materials
Limestone
Total raw materials cost
Conversion costs
Operating labor and supervision
FGD
Solids disposal
Utilities
Process water
Electricity
Maintenance
Labor and material
Analyses
Waste disposal operation
Total conversion costs
Total direct costs
Annual
quantity
15,800 tons
61,900 man-hr
18,720 man-hr
99,670 kgal
47,683,000 kWh
6,240 man-hr
104,500 tons
Unit
cost, $
8.50/ton
15.00/man-hr
21.00/man-hr
0.14/kgal
0.03 7 /kWh
21.00/man-hr
0.15/ton
Total
annual
cost, $
133.900
133,900
928,500
393,100
14,000
1,764,300
3,464,700
131,000
15,700
6,711,300
6,845,200
Indirect Costs - First-Year
Overheads
Plant and administrative (60% of conversion
costs less utilities)
Total first-year operating and maintenance costs
Levelized capital charges (14.7% of total capital
investment)
Total first-year annual revenue requirements
Levelized first-year operating and maintenance
costs (1.886 first-year 0 and M)
Levelized annual revenue requirements
2,959,800
9,805,000
13.698.800
23,503,800
18.492.200
32,191,000
M$ Mills/kWh
First-year annual revenue requirements 23.50 8.55
Levelized annual revenue requirements 32.19 11.71
Basis
Upper Midwest plant location, 1984 revenue requirements.
Remaining life of power plant, 30 years.
Power unit on-stream time, 5,500 hr/yr.
Coal burned, 1,347,000 tons/yr, 9,500 Btu/kWh.
Total direct investment, $45,659,000; total fixed investment, $71,227,000; and total capital
investment, $93,189,000.
-------
TABLE 20. SUMMARY OF THE TOTAL
FIRST-YEAR REVENUE REQUIREMENTS
Raw materials
Operating labor and supervision
Electricity
Maintenance
Levelized capital charges
Overheads
Other annual costs
Total first-year revenue
requirements
Total cost, $
Generic lime
spray dryer
process
1,026,900
948,800
1,485,600
1,939,400
9,727,100
1,796,400
116,200
17,040,400
Limestone
slurry
process
133,900
1,321,600
1,764,300
3,464,700
13,698,800
2,959,800
160,700
23,503,800
The higher maintenance charge for the limestone process is due to
both the larger number of equipment items needed and the problems
associated with handling and recirculating a corrosive and erosive
scrubbing slurry.
SENSITIVITY ANALYSIS
Sensitivity to Raw Material Prices
The sensitivity of the first-year annual revenue requirements for
the generic lime spray dryer process and the limestone slurry process to
the delivered raw material cost was calculated. The results of this
sensitivity analysis are shown in Figure 3.
Although the generic lime spray dryer process is more sensitive
than the limestone slurry process to changes in the delivered price of
the raw material, the low-sulfur nature of the coal and the low S02
removal requirement preclude changes from the base-case costs from
significantly changing the economic results. The generic lime spray
dryer process has lower first-year annual revenue requirements regard-
less of the raw material prices selected. For example, a 25% increase
(or decrease) in the delivered cost of lime results in only a 1.3%
increase (or decrease) in the first-year annual revenue requirements for
the generic lime spray dryer process. This is still 26.5% less than the
first-year annual revenue requirements for the base-case limestone
slurry process.
47
-------
.c-
oo
10.0
g 9.0 -
7.0
6.0
5.0
LIMESTONE COST, 5/TON
5.00 8.50 12.00
\ Y
Limestone slurry process
Generic lime spray dryer process
I
I
75.00 102.00 125.00
LIME COST (DELIVERED), $/TON
Figure 3. Sensitivity of the first-year annual
revenue requirements to the delivered
cost of the raw material.
10.0
9.0
8.0
5- 6-0
5.0
4.0
_L
Limestone slurry process
Generic lime spray dryer process
_L
_L
_L
0.8 1.0 1.1 1.2 1.3 1.4 1.5
RAW MATERIAL STOICHIOMETRY, MOL ALKALI/MOL S02 ABSORBED
Figure 4. Sensitivity of the first-year annual revenue
requirements to the raw material stoichiometry
in the absorber.
-------
The limestone slurry process, due to the low unit cost of limestone
as well as the lower sulfur level in the coal and the lower SC>2 removal
requirements, is essentially insensitive to the delivered price of
limestone.
Sensitivity to Raw Material Stoichiometry
Since the generic lime spray dryer process technology has only been
demonstrated on a pilot-plant scale, the assumed Stoichiometry in the
spray dryer could change as the technology is developed further. In
addition, the alkalinity in the fly ash from low-sulfur coals may vary
between coals. The required lime Stoichiometry for coals with the same
sulfur content could change, depending on the fly ash alkalinity of coal
being burned. Therefore, a sensitivity analysis showing the changes in
total first-year revenue requirements as the raw material Stoichiometry
in the spray dryer is changed has been included.
Table 21 lists both the base-case and the alternative stoichio-
metries used in the sensitivity analysis. The raw material stoichio-
metries given are in mols of alkali per mol of S0~ absorbed. The range
of stoichiometries shown for the generic lime spray dryer process is
1.00 (-18.0%) to 1.46 (+19.7%).
The capital investments for each processing area are adjusted by
using area scale factors and the ratio of raw material flow rates through
each area. Processing areas that are sized independently of the raw
material rates (gas handling and S02 absorption) are the same for each
of the alternative stoichiometries. Many of the processing areas that
are dependent on the raw material flow rate contribute only minor amounts
to the capital investment. For example, a 19.7% increase in raw material
flow rate increases the capital investment only about 2%.
The annual revenue requirements for the generic lime spray dryer
process are somewhat more sensitive to the raw material Stoichiometry
than the raw material cost. For example, a 19.7% increase in the raw
material Stoichiometry results in a 3.1% increase in first-year revenue
requirements. However, from these results (as shown in Figure 4) it is
apparent that Stoichiometry changes over a wide range will have little
effect on the capital investment and annual revenue requirement relation-
ships of the two processes.
Sensitivity to Waste Disposal Costs
An alternate limestone slurry process in which the waste sludge is
dewatered and fixed before disposal in a landfill is included for com-
parison purposes. For this alternate process, the front end of the
limestone slurry process (through the venturi/spray tower absorbers) is
identical to the base-case limestone slurry process. The major difference
is that the absorber slurry bleed is treated using a process similar to
the IU Conversion Systems, Inc. (IUCS) fixation process. In this process
49
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TABLE 21. COMPARISON OF TOTAL CAPITAL INVESTMENT AND
FIRST-YEAR UNIT REVENUE REQUIREMENTS FOR THE GENERIC LIME
SPRAY DRYER PROCESS AT VARIOUS RAW MATERIAL STOICHIOMETRIES
Total
Raw material stoichiometry
Process
Generic lime spray
dryer
Limestone slurry
Variation
Low
Base
High
Base
Value*
1.00
1.22
1.46
1.12
% change^
-18.0
19.7
-
capital
$/kW
129.9
132.3
135.0
186.4
investment
% change^
-1.8
2.0
-
First-year unit
revenue requirements
Mills/kWh
6.02
6.20
6.39
8.55
% change^
-2.9
3.1
-
a. Raw material stoichiometry is defined as mols of alkali per mol of S02 absorbed.
b. Change is calculated relative to the base-case value.
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the mixed sulfite-sulfate sludge, rather than being pumped to a pond for
disposal, is dewatered, using a thickener and a filter, to 60% solids,
mixed with dry fly ash and lime, and trucked to an onsite landfill for
disposal.
The capital investment for this process was estimated from the
base-case limestone slurry process capital investment by deleting the
disposal area preparation (pond construction) and sludge transportation
charges and including the investment required for the IUCS process
equipment and the landfill preparation. The total capital investment
for the limestone slurry-IUCS process is $91.4M (vs. $93.2M for the
base-case limestone slurry process). The lower capital investment for
the limestone slurry-IUCS process is the result of the much lower land-
fill preparation costs ($0.23M for the landfill vs. $3.79M for the
pond), which overcome the costs ($2.66M) for the additional equipment
(thickeners and filters).
The first-year and the levelized annual revenue requirements for
the limestone slurry-IUCS process are $24.98M (9.08 mills/kWb.) and
$35.20M (12.80 mills/kWh) respectively. These costs are about 6% higher
than those for the base case (i.e., with ponding). Although the levelized
capital charges are lower ($0.2M) for the limestone slurry-IUCS process,
this savings is completely offset by the higher labor costs ($0.88M) and
the higher overheads ($0.62M).
51
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REFERENCES
1. Machine Readable Data Format of FERC FORM 67 Data, 1969-1973,
Applied Data Research, 1976.
2. New Stationary Sources Performance Standards; Electric Utility Steam
Generating Units. Fed. Regist., 44(113):33,580-33,624, June 11, 1979,
3. Technical Assessment Guide, EPRI PS-866-SR, Electric Power Research
Institute, Palo Alto, California, June 1978.
4. Jeynes, P. H. Profitability and Economic Choice, 1st Ed., The Iowa
State University Press, Ames, Iowa, 1968.
5. Economic Indicators, Chemical Engineering, Vols. 83, 84, 85, and 86,
1976, 1977, 1978, and 1979.
52
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
, REPORT NO.
EPA-600/7-80-050
J3. RECIPIENT'S ACCESSION NO.
TITLE ANDSUBTITLE
Preliminary Economic Analysis of a Lime Spray
Dryer FGD System
IB. REPORT DATE
March 1980
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
T.A. Burnett and W.E. O'Brien
|8. PERFORMING ORGANIZATION REPORT NO.
EDT-112
'PERFORMING ORGANIZATION NAME AND ADDRESS
Tennessee Valley Authority
Office of Power
Division of Energy Demonstrations and Technology
Muscle ShoalSi Alabama 35660
10. PROGRAM ELEMENT NO.
INE827
11. CONTRACT/GRANT NO.
Inter agency Agreement
EPA-IAG-D9-E721-BI
2. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
A T
Pr
A TYPE OF REPORT A.NB-P.ERLO
eliminary;
VERED
14. SPONSORING AGENCY CODE
EPA/600/13
-^SUPPLEMENTARY NOTES IERL-RTP project officer is
919/541-2683.
Theodore G. Brna, Mail Drop 61,
16. ABSTRACT
rep0r(. gives results of a preliminary economic analysis of two flue gas
desulfurization (FGD) processes (one dry and one wet) for a new 500-MW power
plant burning Western coal having 0. 7% sulfur , 9. 7% ash, and a heating value of 9700
Btu/lb and meeting current new source performance standards (70% SO2 removal and
0.03 Ib/MBtu particulate emission). The generic lime spray-dryer process used a
baghouse for particulate collection, while the wet limestone slurry process had an
electrostatic precipitator (ESP) for particulate control. (In addition to the coal noted,
the final report will include an economic evaluation for both low- and high-sulfur
Eastern coals.) The analysis shows capital investment costs of Sl32/kW for the lime
process for SO2 and particulate removal, and #186/kW for the limestone process.
First year and levelized annual revenue requirements are 6. 20 and 8. 55 mills /kW,
respectively, for the lime process; and 8.55 and 11.71 mills /kW, respectively, for'
the limestone process. Sensitivity analyses indicate that: (1) delivered raw material
costs do not significantly affect the annual revenue requirements for either process-
(2) annual revenue requirements for the spray dryer are insensitive to the raw mat-
erial stoichiometry; and (3) waste disposal for the wet process, even with fixation,
is more expensive than for the dry process.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATl Field/Group
Pollution Calcium Carbonates
Economic Analysis Spray Drying
Analyzing Coal
Desulfurization Combustion
Flue Gases
Calcium Oxides
Pollution Control
Stationary Sources
13B
05C 13H
14B 21D
07A,07D
21B
07B
18. DISTRIBUHON STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport!
Unclassified
21. NO. OF PAGES
75
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
53
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