United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-82-065b Mar. 1983
SERA Project Summary
The Adipic Acid Enhanced Flue
Gas Desulfurization Process for
Industrial Boilers: Volume 2.
Technical Assessment
G. P. Behrens and O. W. Hargrove
EPA's Industrial Environmental Re-
search Laboratory (Research Triangle
Park, NC) has sponsored an evaluation
of an adipic-acid-enhanced limestone
flue gas desulfurization (FGD) system
on industrial boilers at the Rickenbacker
Air National Guard Base. The SO2
removal efficiency with the adipic acid
averaged 94.3 percent over a 30-day
period, representing a significant im-
provement in the performance of the
system using only limestone. Economic
calculations for an industrial boiler
adipic-acid-enhanced limestone FGD
system indicate a slight reduction in
both capital and operating expenses
relative to a limestone-only system
designed for 90 percent SO2 control of
3.6 percent sulfur coal. The costs are
competitive with the dual alkali system.
The successful demonstration of the
adipic-acid-enhanced limestone system
increases the number of demonstrated
technologies available to a potential
user.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory. Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
EPA's Industrial Environmental Re-
search Laboratory (Research Triangle
Park, NC) is currently developing the
adipic-acid-enhanced limestone flue gas
desulfurization (FGD) process and gather-
ing background information to support a
New Source Performance Standard for
industrial boilers. To demonstrate the
control technology for these sources,
IERL-RTP sponsored an evaluation of an
existing industrial boiler limestone FGD
system, using adipic acid to enhance S02
removal. The test site was the Ricken-
backer Air National Guard Base (RANGB)
near Columbus, OH. The site consists of
six industrial boilers which supply hot
water to the Base facilities. A Research-
Cottrell/Bahco lime/limestone FGD sys-
tem is used to control both particulate and
S02 emissions from these stoker-fired
boilers. Maximum heat generation capac-
ity is 210 million Btu/hr.
The host site was chosen because:
• The RANGB unit istheonly coal-fired
industrial boiler which uses a lime-
stone FGD system.
• The RANGB FGD unit was tested
previously, using lime and limestone
sorbents. Lime tests resulted in aver-
age SOa removal efficiencies of about
90%, while limestone yielded less
than 70%. Therefore, the potential
exists for a significant improvement
in S02 removal efficiency when using
limestone.11'
The increasing differential cost be-
tween clean fuels (oil, gas) and coal
provides the driving force for continued
increases in coal-fired industrial boiler
capacity. The lower cost of limestone,
compared to other alkali reagents, pro-
vides an economic incentive to demon-
strate reliable and efficient operation of a
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V
limestone-based industrial FGD
system. Adding an alternative FGD tech-
nology to the list of demonstrated tech-
nologies will give a potential user greater
flexibility in selecting control equipment.
Typically, limestone systems do not easily
maintain SO2 removal efficiencies as
high as those for sodium-based systems
which are the predominant FGD systems
used for industrial boilers. Based on test-
ing at the EPA/TVA Shawnee prototype
facility, adding a relatively small amount
of adipic acid can increase the removal
capability of limestone systems to levels
obtained by sodium systems. Economic
studies based on the prototype results
indicate that adipic-acid-enhanced sys-
tems may have a cost advantage over
unenhanced limestone systems for utility
applications.121
To demonstrate this technology, EPA
has funded a study to determine the
effectiveness of adipic acid in enhancing
the performance of the RANGB FGD
system. EPA has also funded testing of a
utility system, the 194 MW unit of City
Utilities, Springfield, MO, completed in
the fall of 1981.
PEDCo Environmental Inc., was con-
tracted by EPA to collect continuous SO2
removal efficiency data from the RANGB
unit and to characterize the process
parameters of the adipic-acid-enhanced
system. The results of their study are pub-
lished separately and summarized in this
report. Radian Corporation was contrac-
ted by EPA to monitor the operation of
RANGB. Additionally, Radian evaluated
the results at RANGB and determined
their applicability to new industrial boiler
FGD systems. The approach used for this
study was similar to that used in the FGD
technology assessment report for indus-
trial boilers.'31 Two model boilers (150 and
400 x 106 Btu/hr) using limestone FGD
systems without adipic acid were used as
the base cases. The two systems were
then compared to adipic-acid-enhanced
systems on economic, energy, and environ-
mental impact bases.
Results
Based on results obtained in the
RANGB FGD system testing with adipic
acid and the economic calculations of this
report, an adipic-acid-enhanced lime-
stone FGD process seems to compare
favorably (both technically and economi-
cally) with other commercially available
and demonstrated industrial boiler FGD
processes. The results obtained by TVA
on the similar-sized Shawnee system and
the utility scale demonstration at City
Utilities of Springfield confirm that adipic-
acid-enhanced limestone systems can
achieve 90 percent or greater SO2 re-
moval efficiencies. The bases for these
conclusions are summarized below and
reflect both the results of the testing at
RANGB and the economic, energy, and
environmental considerations of adipic
acid systems applied to new industrial
boilers.
As stated earlier, PEDCo Environmental
Inc. performed the testing at RANGB
including the SOz monitor certification
and process chemistry analysis.141 An
important result of the testing is that, for a
30-day period with an adipic acid con-
centration of about 2000 ppm, S02 re-
moval averaged 94.3 percent. In previous
30-day tests, the system averaged 65.8
percent removal when using only lime-
stone and 91.5 percent when using lime.
Similar increases in SOz removal effi-
ciency at Shawnee and Springfield have
also been observed for adipic-acid-en-
hanced operation over base-line limestone-
only performance.'5'8'
The RANGB limestone FGD system is a
one-of-a-kind design, not likely to be used
in future installations. Therefore, the
development of material and energy
balances and cost estimates for this type
of design was not undertaken. As dis-
cussed previously, the RANGB results
support the results obtained with the
Shawnee FGD system using a turbulent
contact absorber (TCA). Although it treats
utility flue gas, the Shawnee facility is
about the same size as that required for a
medium size industrial boiler. In this
report the Shawnee data (with and with-
out adipic acid addition) provide the bases
for an economic, energy, and environ-
mental impact analysis of industrial boiler
FGD systems.
A technology assessment report on
FGD for industrial boiler applications'31
evaluated five different FGD systems for
five sizes of model industrial boilers burn-
ing a variety of fuels and with varying SO2
removal efficiencies.This report examines
the differences between the adipic-acid-
enhanced system and the base limestone
system for both 150 and 400x 106 Btu per
hour boilers burning 3.5 percent sulfur
Eastern coal requiring 90 percent S02
removal. The system cost results are
compared to those for an equivalent dual
alkali system. The economic, energy, and
environmental impact trends exhibited
for these cases should hold true for boiler
systems with different capacities.
Table 1 gives the capital investment
and annual costs for the adipic acid
system, the limestone base case, and a
dual alkali system for the model boilers.
The adipic-acid-enhanced limestone sys-
tem is 5-6 percent lower in capital
investment and 2-3 percent lower in
operating cost than the limestone base
case. Although there is considerable un-
certainty in the overall cost of the lime-
stone systems (estimated to be ±30
percent), the relatively small cost advan-
tage for the adipic acid system is real
because the costs were estimated for
various subsystems based on technical
factors and material balances. Some of
the technical issues, such as differences
in dewatering efficiency between sludges
from adipic-acid-enhanced and -unen-
hanced systems, may be somewhat site
specific. However, the difference be-
tween costs of the enhanced and un-
enhanced subsystems based on the tech-
nical factors does reflect actual size
differences even though the absolute
cost of each subsystem is known only
within ±30 percent. Table 1 also shows
that both adipic-acid-enhanced (2000
ppm) and -unenhanced limestone sys-
tems have approximately equal capital
and operating costs compared to the dual
alkali system.
Table 1. Capital Investment and Annual Costs for Industrial Boiler FGD Systems (1978 Dollars)
Size
10" Btu/hr
150
150
150
400
400
400
FGD System
Limestone (without ad/pic acid)
Limestone (with adipic acid)
Dual alkali"
Limestone (without adipic acid)
Limestone (with adipic acid)
Dual alkali"
Capital Cost
$1,000
1.568
1.488
1.657
2.714
2.586
2.576
Annual Costa
$1,OOO
785
765
778
1.435
1.412
1,328
'Annual cost includes annual O&ty plus capital-related costs.
*Ref. 7 gives the cost breakdown for dual alkali system.
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The annual cost advantage for the
adipic acid system over the limestone
base case reflects lower capital costs and
lower energy consumption. The energy
consumption of the adipic acid process is
approximately 50 percent of that used in
the base case limestone system. The
adipic acid systems require less than 1
percent of the boiler input energy; the
limestone-only systems require 1.5-1.8
percent. Stack gas reheating is not used
in any application. This large reduction is
because of the increased S02 removal
capability of the adipic-acid-enhanced
limestone slurry and the resulting size
reduction of the slurry circulation pumps
and lower gas-phase pressure drop a-
cross the TCA scrubber required for the
desired removal. Actual design param-
eters for each system were obtained from
correlations of the Shawnee data.
Conclusions
The demonstrated improvement in S02
removal efficiency of adipic acid-en-
hanced limestone FGD systems at Ricken-
backer, Shawnee, and City Utilities has
proven the effectiveness of the process.
The economic calculations indicate a
small reduction in costs compared to a
limestone-only system. Additionally, the
estimated costs appear very competitive
to the dual alkali system, which is the
predominant industrial boiler FGD techno-
logy at the present time.
References
1. PEDCo Environmental Inc. Continu-
ous Sulfur Dioxide Monitoring of the
Industrial Boiler System at Ricken-
backer Air Force Base, Columbus,
Ohio; Volume 1. EMB Report 79-
IBR-2. September 1980.
2. McGlamery, G. G., et al. FGD Eco-
nomics in 1980. In Proceedings:
Symposium on Flue Gas Desulfuri-
zation—Houston, October 1980; Vol-
ume 1, EPA-600/9-81-019a (NTIS
PB81-243156), pp 49-83. April
1981.
3. Dickerman, J. C., and K. L Johnson.
Technology Assessment Report for
Industrial Boiler Applications: Flue
Gas Desulfurization. EPA-600/7-
79-178i (NTIS PB80-150873). No-
vember 1979.
4. Clarke, P. A., et al. The Adipic Acid
Enhanced Flue Gas Desulfurization
Process for Industrial Boilers; Vol-
ume 1. Field Test Results, EPA/IERL-
RTP-1335 (Draft), September 1982.
5. Burbank, D. A., et al. Test Results on
Adipic Acid-Enhanced Limestone
Scrubbing at the EPA Shawnee Test
Facility—Third .Report. In Proceed-
ings: Symposium on Flue Gas Desul-
furization—Houston, October 1980;
Volume 1, EPA-600/9-81-019a
(NTIS PB81-243156), pp 233-286.
April 1981.
6. Mobley, J. D., et al. Control of S02
Emissions by the Adipic Acid En-
hanced Limestone Flue Gas Desul-
furization Process, EPA/IERL-RTP-
P-509. Presented at the 75th
Annual Air Pollution Control Asso-
ciation Meeting, New Orleans, June
20-25,1982.
7. U.S. EPA, Office of Air Quality Plan-
ning and Standards. Fossil Fuel
Fired Industrial Boilers—Back-
ground Information; Volume 1: Chap-
ters 1-9, EPA-450/3-82-006a
(NTIS PB82-202573), March 1982.
G. P. Behrens and 0. W. Hargrove are with Radian Corp., P. 0. Box 9948, Austin,
TX 78766.
J. David Mobley is the EPA Project Officer (see below).
The complete report, entitled "The A dipic A cid Enhanced Flue Gas Desulfurization
Process for Industrial Boilers: Volume2. Technical Assessment," (Order No. PB
83-144 782; Cost: $10.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
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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