United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-83-029 Mar. 1984
Project Summary
Economic Evaluation of
Limestone and Lime Flue Gas
Desulfurization Processes
T.A. Burnett, C.D. Stephenson, F.A. Sudhoff, and J.D. Veitch
The preliminary-grade economics
(accuracy: -15%, +30%) of various
alternative limestone and lime flue gas
desulfurization (FGD) processes are
examined using the current design and
economic premises established for the
continuing series of economic evalua-
tions performed by TVA for EPA. The
economics are projected using the
Shawnee lime/limestone computer
model, which is based on long-term
operating data from EPA's alkali scrub-
bing test facility at TVA's Shawnee
Steam Plant near Paducah, KY. The
capital investment for the base-case
limestone scrubbing process (500 MW,
3.5% sulfur coal, 1979 NSPS, spray
tower, forced oxidation, landfill) is
$206/kW. The first-year and levelized
annual revenue requirements are 10.59
and 15.09 mills/kWh, respectively.
Costs for the equivalent limestone
scrubbing process using a Turbulent
Contact Absorber (TCA) are lower,
while those for the venturi/spray tower
absorber are higher. Forced-oxidation/
landfill disposal has a lower capital
investment than unoxidized/pond
disposal for all options studied; however,
the first-year and levelized annual
revenue requirements are slightly
higher for the forced-oxidation landfill
process for most coal applications. For
the spray tower limestone process to
achieve a specified SO2 removal effi-
ciency, it is more economical to increase
the limestone stoichiometry and mini-
mize the absorber liquid/gas ratio
(L/G). The use of adipic acid or possibly
dibasic acid (DBA) as an additive to
enhance SO2 removal in the limestone
scrubbing process is an economically
attractive option.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This study evaluates the economics of
limestone and lime wet scrubbing FGD
processes that incorporate recent tech-
nological developments such as forced
oxidation, refined absorber design and
operating conditions, landfill disposal,
and the use of additives to enhance
scrubbing efficiency. Most of the processes
are based on EPA-sponsored FGD evalu-
ations at the Shawnee test facility. The
economic data were obtained using a
computer model developed from the
Shawnee test facility results.
The primary focus of this study is on
absorber types, forced oxidation, and the
use of additives. The three types of
absorbers (Turbulent Contact Absorber
(TCA), spray tower, and venturi/spray
tower), the forced oxidation method
(single loop, two loop, and bleedstream),
and the type of additive (magnesium
oxide (MgO) and adipic acid) are the main
subjects. Landfill disposal is the primary
disposal method used, but a range of
pond disposal processes are included for
comparison. All processes without forced
(or natural) oxidation have pond disposal;
all forced oxidation processes, except
two, have landfill disposal.
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Forced oxidation to gypsum has recent-
ly evolved into the mainstream of limestone
and lime processes. Oxidation to nearly
100% gypsum is achieved, and the waste
is readily dewatered to 85% or more
solids. It is apparently tractable to
landfill disposal without stabilization. Use
of the gypsum for wall board and cement
manufacture is also a possibility.
The use of MgO to enhance SOZ
removal efficiency has been investigated
for several years, mostly in lime processes,
to increase dissolved alkalinity. Adipic
acid, an organic additive which has
recently received considerable attention,
acts as a buffer that tends to maintain a
liquid pH favorable to S02 absorption. It
has been extensively evaluated by EPA as
a means of improving limestone FGD
performance.
Processes Evaluated
The processes evaluated consist pri-
marily of combinations of (1) limestone or
lime absorbent; (2) TCA, spray tower, or
venturi/spray tower absorber; (3) pond
disposal of sludge without forced oxidation
or forced oxidation with landfill; and (4) no
additive, and MgO or adipic acid additive.
The alternatives of increased partial
scrubbing (using adipic acid to enhance
SO2 removal efficiency) are also investi-
gated.
Results
The economic results consist of the
capital investment in 1982 dollars, first-
year annual revenue requirements
(which include levelized capital charges)
in 1984 dollars, and levelized (over a 30-
year period) annual revenue requirements
(which consist of levelized operating and
maintenance costs as well as levelized
capital charges). Summaries of these
costs are shown in Table 1.
Comparison of Limestone
Processes With and Without
Forced Oxidation
Costs for comparable limestone processes
without forced oxidation and with pond
disposal and those with forced oxidation
and landfill are shown in Table 2.
Processes without forced oxidation and
with pond disposal have higher capital
investments than comparable processes
with forced oxidation and landfill disposal,
in all cases. The differences increase with
increasing coal sulfur content. The higher
capital investment is largely a result of
disposal area construction costs, which
are 2 to 3-1/2 times higher for ponds
than for landfills. In contrast, the
additional capital investment for forced
oxidation and sludge dewatering is
relatively small. Except for the 5.0%
sulfur coal cases, first-year annual
revenue requirements are higher for
forced-oxidation processes because of
the higher operating labor, maintenance,
and overhead costs associated with the
waste dewatering and landfill operations.
Levelized annual revenue requirements
are higher for the forced-oxidation
processes. This is the result of the higher
proportion of operating and maintenance
costs in the total annual revenue requir-
ments of the forced-oxidation processes.
Additives
Costs of comparable processes with
and without additives are shown in Table
3.
MgO—
The use of MgO as an additive in the
limestone process has no significant
effect on capital investment. The equip-
ment needed to handle the relatively
small volumes of additive does not
materially affect equipment costs. By
improving SO2 removal efficiency and
absorbent utilization the use of MgO
slightly decreases gas handling, SO2
absorption, and disposal costs. The effect
is thus more pronounced at higher coal
sulfur contents. For 3.5% sulfur coal, the
reduction in capital investment is less
than 1%, however.
The effect of MgO on annual revenue
requirements of forced-oxidation processes
is similar to the effect on capital investment.
The cost of the additive is minimal (less
than 1% of total annual revenue require-
ments). The improved SOa removal ef-
ficiency and absorbent utilization, ex-
pressed primarily as reduced absorbent
and electricity costs, more than offset the
cost for MgO. For 3.5% sulfur coal, the
cost reduction is less than 1%.
Adipic Acid
In contrast to the results with MgO
addition, the use of adipic acid appears to
be an economically attractive additive for
all applications considered in this study.
Capital investment reductions range from
nearly 13% for 0.7% sulfur western
subbituminous coal to about 10% for
high-sulfur coal. The additional equipment
needed to handle the small quantities of
adipic acid does not have an appreciable
effect on equipment costs. However, by
improving SO2 removal efficiency and
absorbent utilization, the use of adipic
acid decreases the capital investments
for the feed preparation, gas handling,
S02 absorption, solids separation, and
disposal area costs. The primary reasons
for the more dramatic reductions in costs
are the assumptions that with adipic acid
the limestone stoichiometry can be
reduced by 24% (1.07 versus 1.40) and
that 95% SOz removal can be achieved,
allowing partial flue gas bypass to reduce
both the reheat requirements and the size
of the absorbers. (Note that vendors are
quoting stoichiometries as low as 1.10 on
bids for processes without additives; this
would obviously result in a lower cost
advantage for the adipic-acid-enhanced
process.)
The effect of adipic acid addition on both
the first-year and the levelized annual
revenue requirements for the forced-
oxidation processes is similar to its effect
on capital investment: it decreases costs
11-13%, depending on the coal sulfur
level. Most of this cost reduction is due to
a saving in capital charges. Other
reductions (e.g., for electricity, absorbent,
maintenance, and overhead) also contrib-
ute to a significant degree. For forced
oxidation, the cost of adipic acid is
minimal (less than 1 % of annual revenue
requirements for all except 5.0% sulfur
coal), and the improved SO2 removal
efficiency and absorbent utilization,
expressed primarily as reduced absorbent
and electricity costs, more than offset the
cost for adipic acid.
In processes without forced oxidation,
the annual revenue requirements of
processes using additives are lower than
those of the same process without
additives, but the difference is less
because of the additional additive lost in
the low-solids wastes. The cost of the
additive in these cases is about the same
as the absorbent cost. Except for the
additional additive costs, the other cost
reductions remain unchanged.
Absorber Type
Cost comparisons for limestone pro-
cesses with different types of absorbers are
shown in Table 4 for limestone processes
at the 500-MW, 3.5% sulfur coal condi-
tions. The capital investment relationships
of the processes with TCAs, spray towers,
and venturi/spray towers remain the
same whether forced oxidation or additives
are used. For all, the TCA process has the
lowest capital investment and the venturi/
spray tower has the highest.
The major capital investment advantage
of the TCA process lies in lower costs for
S02 absorption because of the smaller
absorber and lower L/G. Processes using
the larger, lower-pressure-drop spray
tower have higher capital investments for
SO2 absorption than the TCA processes,
which are only partially offset by the
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Table 1. Capital Investment and Annual Revenue Requirements
Annual revenue requirements,
1984$
fiant coal
size, sulfui
MW %
anther Capital investment, 1982$
type"
$10*
$/kW
First -year
$10* mills/ kWh
Level/zed
$10* mills/ kWh
Limestone Processes Without Forced Oxidation"
200 3.5
500 0.7
500 2.0
500 3.5
500 5.0
500 3.5
500 3.5
1,000 3.5
ST
ST
ST
ST
ST
TCA
V-ST
ST
62.7
73.2
90.4
112.6
123.3
107.8
121.7
192.1
314
146
181
225
247
216
243
192
15.8
18.1
23.3
28.8
31.5
27.6
31.3
48.9
14.39
6.56
8.46
10.47
11.44
10.03
11.37
8.89
21.7
24.5
32.1
39.6
43.3
38.0
43.1
67.2
19.72
8.91
11.68
14.42
15.73
13.81
15.68
12.23
Limestone Processes With Forced Oxidation0
200 0.7
200 2.0
200 3.5
200 5.0
500 0.7
500 2.0
500 3.5
500 5.0
500 3.5
500 3.5
500" 3.5
1,000 0.7
1,OOO 2.0
1,OOO 3.5
1,000 5.0
Limestone Processes
Adipic Acid
200 3.5
500 0.7
500 2.0
500 3.5
500 5.0
500 3.5
500 3.5
500 3.5'
500 3.5"
7,000 3.5
MgO
500 0.7
500 2.0
500 3.5
500 5.0
500 3.5
500 3.5
500 3.5
ST
ST
ST
ST
ST
ST
ST
ST
TCA
V-ST
ST
ST
ST
ST
ST
With Forced Oxidation and Additive6
ST
ST
ST
ST
ST
TCA
V-ST
ST
ST
ST
ST
ST
ST
ST
TCA
V-ST
ST
44.4
52.1
59.1
62.6
70.4
86.6
103.1
109.2
98.5
109.2
94.4
109.2
151.7
177.2
187.0
54.4
61.4
79.1
92.8
97.9
90.4
96.3
100.7
92.8
155.5
69.1
86.6
102.5
107.9
98.2
113.1
111.2
222
260
295
313
141
173
206
218
197
218
189
109
152
177
187
272
123
158
186
196
181
193
201
186
155
138
173
205
216
196
226
222
12.3
14.7
16.7
17.8
18.8
24.2
29.1
31.2
27.8
30.8
25.8
28.3
41.1
49.3
53.0
15.3
16.4
21.6
25.8
27.7
25.4
27.0
26.8
25.7
42.8
18.4
23.8
28.8
30.7
27.7
31.6
28.5
11.15
13.40
15.21
16.17
6.84
8.80
10.58
11.36
10.09
11.20
9.40
5.15
7.47
8.97
9.63
13.95
5.97
7.86
9.38
10.07
9.23
9.81
9.73
9.35
7.78
6.70
8.66
10.49
11.18
10.09
11.50
10.36
17.3
21.0
23.9
25.4
26.3
34.4
41.5
44.7
39.5
43.9
36.4
39.2
57.7
69.9
75.5
21.9
23.0
30.4
36.6
39.5
36.1
38.3
37.3
36.4
60.4
25.8
33.6
41.1
43.9
39.5
44.9
39.2
15.76
19.10
21.69
23.O8
9.56
12.49
15.08
16.25
14.37
15.96
13.25
7.13
10.50
12.71
13.73
19.86
8.36
11.07
13.31
14.36
13.12
13.93
13.58
13.25
10.99
9.37
12.23
14.93
15.98
14.38
16.33
14.27
Lime Processes Without Forced Oxidation"
500 0.7
500 2.0
500 3.5
500 5.0
500 3.5
500 3.5
Lime Processes With
500 3.5
500 3.5
500 3.5
Lime Processes With
500 3.5
500 3.5
500 3.5
ST
ST
ST
ST
TCA
V-ST
Forced Oxidation0
ST
TCA
V-ST
Forced Oxidation and MgO°
ST
TCA
V-ST
60.7
79.3
96.2
105.3
94.6
103.2
88.9
86.2
92.7
89.6
90.4
96.8
121
159
192
211
189
206
178
172
185
179
181
194
15.3
21.8
28.0
31.6
27.7
29.9
28.5
27.9
29.6
28.6
28.7
30.3
5.56
7.92
10.19
11.51
10.09
10.88
10.35
10.16
10.77
10.40
10.45
11.01
20.9
30.7
40.3
46.0
40.0
43.0
42.1
41.5
43.8
42.3
42.4
44.5
7.62
11.18
14.66
16.71
14.55
15.63
15.31
15.07
15.92
15.37
15.43
16.18
" ST=spray tower; JCA-Turbulent Contact Absorber; V-ST venturi/spray tower.
" Pond disposal in all cases.
° Landfill disposal in all cases.
d No flue gas reheat.
B Landfill disposal, except as noted.
' Pond disposal.
fl Dibasic acid.
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Table 2. Cost Comparison of Processes With and Without Forced Oxidation
Process*
Capital
investment
1982 $/kW
Annual revenue
requirements,
1984 mills/kWh
First-year
Levelized
O.7% Sulfur Coaf
No forced oxidation, pond
No forced oxidation, landfill
2.0% Sulfur Coal
No forced oxidation, pond
Forced oxidation, landfill
3.5% Sulfur Coal
No forced oxidation, pond
Forced oxidation, landfill
5.0% Sulfur Coal
No forced oxidation, pond
Forced oxidation, landfill
146.5
140.7
180.8
173.1
225.1
206.1
246.7
218.3
6.56
6.84
8.46
8.80
10.47
10.58
11.44
11.36
8.91
9.56
11.68
12.49
14.42
15.08
15.73
16.25
"5OO-MW, limestone spray tower processes, natural oxidation to 95% CaSO*. 2HO forO. 7% sulfur
coal cases, in-loop forces oxidation to 95% CaSO*.2l-PO for all other cases.
" With low sulfur coal, forced oxidation is not required to achieve high (>90%) oxidation ofsulfite to
sulfate.
Table3. Cost Comparison of Processes With and Without Additives
Capital
investment,
1982 $/kW
Annual revenue
requirements,
1984 mills/kWh
First-year
Levelized
Landfill Disposal*
O.7% sulfur coal
No additive
Adipic acid
MgO
2.0% sulfur coal
No additive
Adipic acid
MgO
3.5% sulfur coal
No additive
Adipic acid
MgO
5.0% sulfur coal
No additive
Adipic acid
MgO
Pond Disposaf
3.5% sulfur coal
No additive
Adipic acid
MgO
140.7
122.8
138.2
173.1
158.2
171.8
206.1
185.5
205.0
218.3
195.9
215.8
225.1
201.4
222.4
6.84
5.97
6.70
8.80
7.86
8.72
10.58
9.38
10.49
11.36
10.07
11.18
10.47
9.73
10.36
0.56
8.36
9.37
12.49
11.07
12.39
15.08
13.31
14.93
16.25
14.36
15.98
14.42
13.58
14.27
a 5OO-MW, limeston spray tower processes, natural oxidation for all 0.7% sulfur coal cases, in-
loop forced oxidation for no additives and adipic acid cases, bleedstream forced oxidation for all
MgO processes.
" 5OO-MW, limestone spray tower processes without forced oxidation.
lower capital investment for fans. The
processes using the venturi/spray tower
absorbers have a higher limestone
utilization rate, and thus slightly lower
capital investments for feed preparation,
solids dewatering, and disposal. This is
more than offset by the higher capital
investments for gas handling and S02
absorption. The same cost relationships
also prevail in annual revenue require-
ments, largely because of costs based on
capital investments such as maintenance
and capital charges. In costs other than
maintenance and capital charges, there
is little difference in annual revenue
requirements between the processes
with TCAs, spray towers, or venturi/spray
towers.
Spray Tower Absorber Design
Conditions
Since the superficial gas velocity
through the absorber, the pH of the slurry,
and the SOz removal efficiency are
normally determined by the technology
or the performance requirements, the
absorber L/G ratio and stoichiometry are
the only remaining design conditions
that can be optimized. Thus it becomes an
economic tradeoff between the costs
associated with slurry recirculation
pumps (L/G) and the costs for the
limestone preparation equipment andthe
waste disposal area (stoichiometry).
Increasing the limestone stoichiometry
and decreasing the absorber L/G is the
more economical option. Increasing the
stoichiometry from 1.1 to 1.4 mol
CaCOa/mol (SO2+2HCI) absorbed resu Its
in a decrease in capital investment of 14-
18%. Levelized annual revenue require-
ments decrease 16-18%.
Partial Versus Full Scrubbing
For lower sulfur coals, where relatively
modest S02 removal efficiencies are
required, two alternative designs are
possible: full scrubbing at the required
removal efficiency or scrubbing part of
the flue gas at a high removal efficiency
(e.g., 90%) and bypassing the rest of the
flue gas around the absorber to reduce or
eliminate the need for stack gas reheat.
The costs of full and partial scrubbing for
a range of coal sulfur levels are based on
a 500-MW limestone process with a
spray tower absorber, forced oxidation,
and landfill disposal. Partial scrubbing is
based on 90% S02 removal in the
absorber. In terms of capital investment,
it is less expensive to partially scrub the
flue gas from coals with sulfur contents
below about 1.5%. For 0.7% sulfur
western subbituminous coal, partial
scrubbing saves about $10/kW in capital
investment (a 6.5% reduction) and about
1.2 mills/kWh in annual revenue require-
ments (an 11.2% reduction). For 2.0%
sulfur coal, full scrubbing saves $4.0/kW
in capital investment over partial scrubbing,
but the annual revenue requirements are
essentially the same in both cases.
Full-Scrubbing Processes at
85%, 90%, and 95% SO2
Removal
As the required SO2 removal efficiency
increases from 85% to 95%, the economic
advantage of the adipic-acid-enhanced
process increases. At 85% removal the
adipic acid-enhanced process is about
9% lower in capital investment and nearly
12% lower in annual revenue require-
ments. At 95% removal the corresponding
reductions are more than 15% for both
capital investment and annual revenue
requirements.
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Table 4. Cost Comparison by Absorber Type"
Process"
Capital
investment.
1982 $/kW
Annual revenue
requirements.
1984 mills/ kWh
First-year
Level/zed
Without Forced Oxidation (Pond Disposal)
Spray tower
TCA
Venturi/spray tower
With Forced Oxidation
Spray tower
TCA
Venturi/spray tower
With Forced Oxidation
Spray tower
TCA
Venturi/spray tower
225.1
215.6
243.4
(Landfill Disposal)
206.7
797.0
218.4
and Adipic Acid (Landfill Disposal)
185.5
180.9
192.7
10.47
10.03
11.37
10.58
10.09
11.20
9.38
9.23
9.81
14.42
13.81
15.68
15.08
14.37
15.96
13.31
13.12
13.93
' 500 MW. 3.5% S.
Limestone and Lime Processes
Limestone and lime process costs by
process area are compared for different
coal sulfur contents and by process type
in Table 5. The processes using lime
maintain a substantial advantage in
capital investment for all conditions. The
advantage decreases slightly with increas-
ing coal sulfur content. At the same coal
sulfur content, the capital investment
advantage of the lime processes with
variations such as forced oxidation and
additives remains relatively constant.
about 15% lower than the corresponding
limestone processes.
Coal sulfur content has an important
effect on relationships of the annual
revenue requirements. The lime process
has lower annual revenue requirements
for the low-sulfur coal cases, but the
advantage decreases with increasing
coal-sulfur content because of increasing
absorbent costs. The different relationship
in first-year and levelized annual revenue
requirements occurs because levelizing
increases operating and maintenance
Table 5. Cost Comparison of Limestone and Lime Process
Process
Spray Tower8
0.7% sulfur coal
Limestone
Lime
2.0% sulfur coal
Limestone
Lime
3.5% sulfur coal
Limestone
Lime
5.0% sulfur coal
Limestone
Lime
Venturi / Spray Tower"
Without forced oxidation (pond)
Limestone
Lime
Forced oxidation (landfill)
Limestone
Lime
With forced oxidation and
MgOc (landfill)
Limestone
Lime
Capital
investment,
1982 $/kW
146.5
121.5
183.4
158.6
225.1
192.3
246.7
210.6
243.4
206.3
2/5.4
785.4
226.7
193.5
Annual revenue
requirements,
1984 mills/kWh
First-year
6.56
5.56
8.46
7.92
10.47
10.19
11.44
11.51
77.37
10.88
11.20
10.78
11.50
11.01
Levelized
8,91
7.62
11.61
11.81
14.42
14.66
15.73
16.71
15.68
15.63
15.96
15.92
16.33
16.18
*5OO-MW. without forced oxidation, pond disposal.
*500-MW, 3.5% sulfur coal.
cBleedstream forced oxidation.
costs, which are a significantly lower
portion of annual revenue requirements
for the limestone process.
Reheat
Since in-line steam reheat involves
significant expenditures in both capital
investment and annual revenue require-
ments and since benefits of reheat
sometimes are not apparent, some
utilities have specified FGD systems
without reheat. In comparing two 500-
MW, 3.5% sulfur coal, limestone forced-
oxidation processes, the capital invest-
ment without reheat is more than 8%
lower ($18/kW) than with reheat. The annual
revenue requirements are about 12%
lower without reheat. These lower costs
are due partly to the elimination of steam
consumption and partly to the reduction
in maintenance, overhead, and capital
charges because of the lower capital
investment for the case without reheat.
Conclusions
Processes with forced oxidation and
landfill disposal have lower capital
investments than processes without
forced oxidation and pond disposal
because the aggregate costs of forced
oxidation and dewatering equipment and
landfill construction are small, compared
with the cost of pond construction. First-
year annual revenue requirements are
slightly higher for forced-oxidation
processes under most conditions evalu-
ated. At large waste volumes, however,
the first-year annual revenue require-
ments for processes without forced
oxidation are slightly lower. All processes
without forced oxidation have slightly
lower levelized annual revenue require-
ments.
The use of additives reduces both the
capital investment and annual revenue
requirements of limestone processes. For
processes with forced oxidation and
landfill disposal, the effects of MgO are
marginal; but with adipic acid, more
substantial reductions of 10-13% are
obtained in both capital investment and
annual revenue requirements. The cost
reductions are reflected in capital invest-
ment by reduced equipment sizes and
smaller waste volumes and in annual
revenue requirements by reduced capital
charges (the major factor) and other costs
related to capital investment and by
reduced absorbent and electricity costs.
The larger cost reductions obtained with
adipic acid are largely a result of a
substantial improvement in limestone
utilization. The costs related to the use of
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additives are a very small part of the total
costs, and both capital investment and
annual revenue requirements are very
insensitive to changes in the cost and
consumption rate of the additives or to
the use of lower cost substitutes. The
higher removal efficiencies attainable
with adipic acid also permit the use of the
more economical partial scrubbing with
bypass over a wider range of coal sulfur
contents. For processes that use pond
disposal, the use of additives has the
same effect on capital investment as it
does for processes using landfill disposal,
but the cost reduction in annual revenue
requirements is reduced by about half
because of the additional additive loss in
the low-solids waste.
Processes using TCAs are about 5%
less expensive than processes using
spray towers and 12% less expensive
than processes using venturi/spray
towers because of the smaller size
and lower L/G ratio of the high-pressure-
drop TCA, assuming that maintenance
costs are the same percentage of equip-
ment costs for all the processes. Changes
of 15% in maintenance costs for either
process make the annual revenue require-
ments of processes using TCAs and spray
towers equivalent.
Economically, the optimum absorber
design favors higher limestone stoichio-
metries and lower L/G ratios. For the
same SOa removal efficiency, a 1.4
stoichiometry and a low L/G is 14-18%
lower in capital investment and annual
revenue requirements than a design with
a 1.1 stoichiometry and a high L/G ratio.
Partial scrubbing at 90% removal
efficiency with bypass of some of the flue
gas is more economical at coal sulfur
contents below about 2% because the
bypassed flue gas reduces reheat costs.
All lime processes evaluated have
lower capital investments than limestone
processes. They also have lower annual
revenue requirements at lower coal
sulfur contents. Lime processes are more
sensitive to absorbent costs, however,
andalso to levelizing, since operating and
maintenance costs constitute a larger
percentage of the total annual revenue
requirements. As a result, lime process
annual revenue requirements increase
more rapidly with coal sulfur content than
those of limestone processes, particularly
if levelized annual revenue requirements
are compared. At a coal sulfur content of
about 4.5% the first-year annual revenue
requirements of lime and limestone
processes are equal; at a coal sulfur
content of about 3.0% the levelized
annual revenue requirements are also
equal. As the coal sulfur content further
increases, limestone processes become
increasingly more economical.
T. A. Burnett, C. D. Stephenson, F. A. Sudhoff, andJ. D. Veitch are with Tennessee
Valley Authority. Muscle Shoals. AL 35660.
J. D. Mobley is the EPA Project Officer (see below).
The complete report, entitled "Economic Evaluation of Limestone and Lime Flue
Gas Desulfurization Processes," {Order No. PB 84-133 644; Cost: $25.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
* U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/873
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