United States
 Environmental Protection
Industrial Environmental Research
Research Triangle Park NC 27711
 Research and Development
EPA-600/S9-82-012   Sept. 1982
Project  Summary
Proceedings:  EPA's  Industry
Briefing  on the Adipic  Acid
Enhanced  Limestone  FGD
Process  (July 1981)
J. David Mobley, Briefing Chairman
  The proceedings document pre-
 sentations made during an EPA-spon-
 sored industry briefing which was held
 on July 15, 1981, in Springfield, MO.
 The briefing dealt with the status of
 EPA's research activities on the adipic
 acid enhanced limestone flue gas
 desulfurization (FGD) process. Subjects
 covered  included: (1) overview of the
 adipic acid enhanced process.  (2)
 status of the demonstration project at
 Springfield City Utilities, (3) results of
 the demonstration  project on an
 industrial boiler, (4) results of testing
 at the EPA prototype test facility at
 TVA's Shawnee Steam Plant,  and (5)
 economics of limestone FGD systems
 using adipic acid. The briefing provided
 users, architects, engineers, vendors,
 consultants, and government person-
 with a comprehensive assessment of
 this innovative technology for con-
 trolling SOa emissions.
  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 fsee Project Report ordering
 information at back).

  EPA's  Industrial Environmental Re-
 search Laboratory in Research Triangle
 Park (IERL-RTP) periodically sponsors
symposia and industry briefings for the
transfer of information regarding research,
development, and application activities
with the objective of further accelerating
the development and commercialization
of technology. One of the major IERL-
RTP efforts for the past several years
has been advancement of the technology
for flue gas desulfurization (FGD). A key
element of the FGD program has been
the advancement of  lime/limestone
wet scrubbing technology, which has
led to the development of the adipic acid
enhanced limestone FGD process.
  The July 15, 1981,  industry briefing
provided interested people with EPA's
latest findings on the use of adipic acid
in lime/limestone scrubbers. The
presentations covered testing  work
performed at the laboratory, bench,
pilot, prototype, industrial, and  utility
scales. In addition, an economic assess-
ment of the use  of the technology on
new and retrofit systems was included.
The presentations were complemented
by a tour of the limestone FGD system at
Springfield City  Utilities' Southwest
Power Station in Springfield, MO.
  During the tour the FGD system was
operating with the addition of approxi-
mately 1500 ppm of  adipic acid. The
scrubber was operating at 5.5 pH with a
liquid-to-gas ratio of about 60 gal./1000
ft3.* The boiler was operating at 75% of
•Readers more familiar with the metric system may
 use the following conversion factors-1 Btu = 1.055
 J, 1 ft3 = 0.028 m3, 1 gal = 3.79 liters, and 1 Ib =
 0.45 kg.

maximum load with uncontrolled emis-
sions of 6.5 lb/106 Btu. The emissions
after the scrubber were 0.3 lb/106Btu
which represents an SOa removal
efficiency of over 95%. The SOaremoval
efficiency of the unit under  similar
operating conditions  but without the
adipic acid additive  had been about
  More than 120 people (representing
electric utilities,  industrial sources,
architect and engineering firms, vendors,
consultants, and government personnel)
attended the briefing in Springfield,
  Abstracts of the presentations follow.
Asterisks by authors' names denote

Overview of EPA's Testing of
the Adipic Acid Enhanced
Limestone FGD Process

John C. S. Chang, Acurex
Corporation and J. David
Mobley,* U.S. Environmental
Protection Agency

  Extensive  research  has  determined
that adipic  acid, when used as  an
additive to a limestone flue gas desul-
furization (FGD) system, will improve
the performance of the system.  Both
SO2 removal and  limestone utilization
can be greatly increased by the buffering
effect of adipic acid. Extensive test data
show that the technology is ready  for
full scale application.  Although adipic
acid does degrade in  the scrubber,  no
significant operating problems or envi-
ronmental impacts have been identified.
Economic estimates  show the adipic
acid enhanced limestone FGD system to
be economically attractive, compared to
conventional FGD systems.  In addition,
further research is underway to decrease
the  cost  of using additives in  FGD

Status  of Adipic Acid
Enhanced FGD System
Demonstration at Springfield
City Utilities Southwest
Power Plant

0. W. Hargrove*,  J. D. Colley,
and G.  E. Brown,  Radian

  Adipic acid, as an additive to enhance
the performance of  limestone FGD
systems,  was  demonstrated  quite
successfully at Springfield City Utilities'
Southwest Power Plant (SWPP), a 194-
MW coal-fired unit designed to burn
3.5-4.0% sulfur coal.  Both forced and
natural oxidation testing were planned
at Springfield. The forced oxidation tests
were completed in late April 1981; the
natural oxidation tests should  be
completed in August 1981. SOa removal
efficiencies greater than 90% were
consistently achieved  for over 35 days
with adipic acid in the forced oxidation
mode. This compares with SOa removal
efficiencies of 50-60% without  adipic
acid. Limestone utilization was also
typically about  90%.  In addition, the
scrubber operated for 36 days with only
about  10  hours  of  downtime. This
represents the longest period of con-
tinuous operation at SWPP to date. The
improved reliability can be attributed to
design  modifications and operating
procedure changes implemented by City
Utilities, additional process  input by
Radian, and process reliability factors
created by adipic acid addition  and
forced oxidation.

Evaluation of the  Adipic Acid
Enhanced Limestone Flue Gas
Desulfurization Process on an
Industrial Boiler

R. W. Gerstle and D. S.  Henzel
PEDCo Environmental, Inc.  and
J. David Mobley* U.S.
Environmental Protection

  The purpose  of this study was to
evaluate the effect of the addition of
adipic acid on the SOa removal of a wet
limestone  FGD system on  a coal-fired
industrial  boiler facility.  The boiler
facility at the Rickenbacker Air National
Guard Base near Columbus, OH, was
selected for this study. Emission data
were collected in accordance with the
regulations for  SO2 compliance  data
specified in the Federal Register. Test
results show that adding adipic acid to
the  limestone slurry significantly  im-
proved the SOa removal efficiency of the
FGD system. Limited baseline data on
operations with limestone only indicated
a performance level of 55% SOa removal.
With addition of about 2200 ppm of
adipic acid to  the limestone scrubbing
system, the unit's level of performance
increased to an average of 94.3% SOa
removal over a 30-day test period.
Adipic Acid-Enhanced
Lime/Limestone Test Results
at the EPA Alkali Scrubbing
Test Facility

Shih-Chung Wang and Dewey
A. Burbank* Bechtel National,

  FGD tests  are being conducted at
EPA's 10-MW prototype test facility at
TVA's coal-fired Shawnee Power Station
near Paducah, KY. Test results show that
adipic  acid  is a powerful  lime and
limestone scrubber additive for improving
SOa removal. SOz removal efficiencies
in excess of 90% and reliable scrubber
operation have been demonstrated in
four long-term (greater  than 1  month)
limestone  runs with adipic acid  en-
hancement:  two  venturi/spray tower
runs  using two  scrubber  loops with
forced oxidation in the venturi loop, a
TCA run without forced oxidation, and a
spray tower run with forced oxidation.
Full  or  partial factorial tests, each
lasting 12 hours or longer, including 5-7
hours of steady-state operation, were
also conducted to characterize the SOa
removal performance of the scrubber as
a function of operating parameters such
as gas and slurry flow rate, pH,  and
adipic acid concentration.  Data from
these tests were correlated using  a
semi-theoretical  mathematical model
that  conforms  to  boundary constraints
to provide a  design basis  for use of
adipic acid in lime/limestone scrubbers.

Economics of Limestone FGD
Systems Using Adipic Acid

R. L Torstrick*, C. D.
Stephenson, J. D. Veitch
Tennessee Valley Authority

  The economics of the use of adipic
acid additive in limestone  FGD were
examined using current  design and
economic premises established for the
continuing series of economic  evalua-
tions performed by TVA  for EPA.
Economics  were projected  based  on
long-term Shawnee test facility operating
data, Springfield test facility operating
conditions,  and recent  Shawnee  test
facility operation.  Incorporating  the
improved scrubbing efficiency effected
by adipic acid into the design of a 90%
SOa removal  limestone FGD-landfill
process reduces the capital investment
and  annual  revenue requirements by
about 2% each. A further similar

reduction is attained using 95% removal
and partial bypass. For existing facilities,
based  on Springfield  and Shawnee
data, using adipic acid increases capital
investment and annual revenue require-
ments slightly but reduces the unit cost
in terms of cost per ton of S02 removed.
Although the differences in economics
are not significant,  considering the
accuracy of these cost projections, the
use of  adipic acid for obtaining higher
degrees of SC>2 removal may be signifi-
cant in (1) bringing marginal plants into
compliance,  and (2) allowing power
units to  burn higher sulfur  coals  to
reduce costs. One of the more significant
advantages of using adipic acid is the
ability  to  improve the SO2  removal
efficiency  of an  existing scrubber
system simply by adding adipic acid.
The EPA author J. David Mob/ey (a/so the EPA Project Officer, see below) is with
  the Industrial Environmental Research Laboratory, Research Triangle Park,
  NC 27711.
The complete report, entitled "Proceedings: EPA's Industry Briefing on the
  Adipic Acid  Enhanced Limestone FGD Process (July 1981)," (Order No.
  PB 82-231 853; Cost: $ 13.50, 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
                                                                                     0 UAOOVEIINMENT PRINTING OFFICE-1962-559-017/0807

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Environmental Protection
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