United States
                     Environmental Protection
                     Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
                     Research and Development
EPA-600/S7-84-031 Apr. 1984
v>ERA          Project  Summary
                     Evaluation  and   Demonstration  of
                     the  Chemically   Active   Fluid   Bed
                     R.E. Sommer, A.S. Werner, and Z.  Kowszun
                       Results are reported on the operation
                     of a 17-MW Chemically Active Fluid Bed
                     (CAFB) demonstration unit, retrofitted
                     to a natural gas boiler. The CAFB pro-
                     cess gasifies high-sulfur, high-metals-
                     content liquid and solid fuels. Residual
                     oil,  lignite, and bituminous coal were
                     gasified separately or together between
                     November 1979 and June 1981. Oil was
                     gasified for 540 hours. A maximum con-
                     tinuous-rating test sustained 22 MW of
                     electrical energy for 2 hours. Sulfur re-
                     moval efficiencies of up to 90 percent
                     were achieved during oil gasification.
                     Lignite and bituminous coal were gas-
                     ified for 42 hours: sulfur removal effi-
                     ciencies of up to  70 percent were
                     obtained. Design and operational areas
                     which need to be upgraded were iden-
                     tified. Continuous monitors were used
                     to measure boiler flue gas emissions of
                     SO,, nitrogen oxides  (NOX), CO, oxy-
                     gen, CO,, and opacity. Periodic manual
                     emission tests were conducted for par-
                     ticulate,  SO,,  and NOX,  using  EPA
                     reference methods. Emissions of these
                     three criteria pollutants were generally
                     lower than New Source Performance
                     Standards for utility boilers, although
                     occasionally excessive particulate and
                     SO, emissions  were  observed.  NOX
                     emissions were consistently lower than
                     those from natural gas combustion. Po-
                     tential  multimedia impacts from the
                     three major discharge streams from the
                     CAFB (boiler flue gas, spent solids from
                     the  gasifier bed, and  sulfur recovery
                     system ash) were characterized using
                     the phased approach to environmental
                     assessments developed by EPA. Results
                     of detailed chemical analyses and bio-
                     logical assays  are reported.
                       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
documented in a separate report of the
same title (see Project Report ordering
information at back).

Background
  The Chemically Active Fluid Bed (CAFB)
process was developed in the late 1960's by
the  Esso Research  Center,  Abingdon
(ERCA), England, as a way to generate elec-
trical energy from high-sulfur, high-metal,
heavy fuel oil. In the CAFB process, oil or
coal is fed continuously into a fluidized bed
of lime maintained at 870 °C. Air is preheated
and fed to the gasifier in substoichiometric
proportions. The fuel entering the gasifier is
vaporized, oxidized, and cracked to produce
a low-Btu low-sulfur gas which, after pass-
ing through cyclones to remove particulate
matter, is burned in a conventional gas
boiler. Sulfur  contained in the  oil initially
forms various gaseous compounds which
then  react with the bed lime  to yield solid
calcium sulfide.  Some of the fuel-bound
trace elements are also bound to the bed
stone. The sulfided lime  is  cycled to a
regeneration unit where it is oxidized to pro-
duce  calcium oxide (which is returned to the
gasifier) and S02 (which is sent to a sulfur
recovery unit).
  During the early and mid-1970's, the pro-
cess  was demonstrated at a 2.9 MW pilot
plant  to provide energy efficiently from both
liquid and solid fuels while simultaneously
limiting emissions of S02, NOX, vanadium,
and nickel. Based on the successful pilot
plant  tests in England, the U.S. EPA and the
Texas-based Central Power and Light Com-
pany  (CP&L) commissioned Foster Wheeler
Energy Corporation (FWEC) to construct a
17-MW demonstration plant in San Benito,
TX. The agreement with CP&L, signed in

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May 1975,  provided for construction and
operation of the demonstration plant. The
contract  with  EPA (68-02-2106) covered
engineering design, labor for start-up, fuels
and feedstocks, and environmental monitor-
ing. Design of the unit, based on the ERCA
design and operating experience, was ini-
tiated in January 1975, and construction was
completed in January 1979. The plant incor-
porated FWEC's proprietary sulfur recovery
system, RESOX™. More than 130 contrac-
tors and subcontractors were employed dur-
ing construction. A test program using heavy
oil, lignite,  and bituminous coal was  con-
ducted between October  1979  and June
1981.
  This report describes the design, opera-
tion, and environmental aspects of the San
Benito plant.

Plant Operation
  Oil, lignite, and bituminous coal were
gasified separately or together in the CAFB
unit, which was retrofitted on the front end
of a natural gas boiler, between November
1979 and June 1981. Eleven test runs were
conducted during this period. Operating con-
ditions and fuels employed for the runs are
summarized in  Table 1. Residual  oil was
gasified during the first four runs, totaling
343.5 hours of operation. The fifth gasifica-
tion  run was the longest and most suc-
cessful.  All three systems, the  gasifier,
regenerator, and  RESOX™  reactor, were
operational during the run. During the fifth
run, oil (the primary feedstock) was gasified
for 196 hours; however, lignite was intro-
duced and gasified in combination with the
oil for the final 3 hours of operation. During
the second run, a maximum continuous-
rating test  sustained 22 MW of electrical
energy on oil for 2 hours. Problems with the
transfer of  bed stone between the gasifier
and regenerator limited regenerator opera-
tion during oil gasification to 213 hours. The
RESOX™  sulfur recovery system  was
operated during oil gasification for 115 hours.
Sulfur removal efficiencies of up to 90 per-
cent were obtained.
  West Texas lignite was gasified for 10.5
hours: problems with the coal feed system
precluded additional operation. An eastern
bituminous coal was gasified for 31.7 hours
during the final four runs: again,  coal feed
problems caused premature termination of
two of the runs. Throughout the final two
runs, the boiler flames were strong and well-
defined. A sulfur removal efficiency of 70
percent was achieved during the final run.
  The following alterations would improve
operation:
  • More efficient cleanup of product gas
    entering  the  boiler. The single-stage
    cyclones at San Benito were, at times,
    inadequate.
  • A sturdier, more reliable  coal  feed
    system. The coal feed system was very
    sensitive to coal physical properties and
    was prone to plugging under some con-
    ditions.
  • A burnup cell for the carbon on the
    cyclone fines.
  • More  reliable  rotary seals,  valves,
    dampers, augers, and filters, to better
    withstand  the  severe conditions  of
    CAFB  operation.

Environmental Aspects
  The demonstration unit was evaluated to
determine its capability to  control flue gas
criteria pollutant emissions and to estimate
potential multimedia pollution impacts. Con-
tinuous monitors  were used by FWEC to
measure S02, NOX, CO, oxygen, C02, and
opacity. In  addition, periodic manual emis-
sion tests were conducted by FWEC for par-
ticulate, S02,  and   NO    using  EPA
Table 1. Summary of the 11 Gasification Runs Between December 1979 and June 1981
Hours of Fuels Regenerator RESOX™ Boiler load
Run Dates gasification used operation operation product gas
1

2

•
3

4


5


6


7


8
9



10


11

12/19/79-
12/20/79
1/27/80-
1/31/80-

4/ 8/80-
4/14/80
7/29/80-
81 1/80

9/24/80-
101 1/80

11/20/80-
11/25/80

121 9/80-
12/12/80

2/81
3/11/83-
3/12/83

61 5-61 6/81
61 7-61 8/81
61 9-6/10/81

6/22/81-
6/23/81
32

77.5


144

90


196


79


5.5


4
10


19.5
17.5
19

16

Oil

Oil


Oil

Oil


Oil
Lignite, 2 fir

Oil
Lignite
Oil/lignite
Oil
Oil/lignite
Lignite
Lignite
Oil, 3 hr
Oil /coal, 3 hr
Coal, 4 hr
Oil
Oil, Oil/coal
Oil, Oil/coal
Oil, 3 hr
Oil/ coal, 5 hr
Coal, 8 hr
No

No


No
3hr
Yes


Yes


No


Yes


Yes
No


Yes


No


No

No


No

Yes
17 hr

Yes


No


No


No
No


No


No


4MW- 6hrs
9-10MW-28hrs
9-11 MW
14-15 MW
20-22 MW- 3hrs
7.2-15 MW

10.5 MW
72 hrs product /natural gas

8.5 MW - product gas
2-hr coal provided 30% of
8.5 MW
5- 6 MW


9 MW
7.5 MW


8.7 MW



9.0 MW


4.8 MW - product gas
5.9 MW - natural gas
Comments


Maintained 22 MW for maximum
continuous rating.



First use of /V2 for material
transfer between gasifers
and regenerator.
During this run GCA performed
environmental assessment




The gasifier bed appeared to be
releasing S02.

Run aborted.
Approximately 4.5 MW was from
product gas.





The bed from run 10 was reused
in this run.

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reference methods 5, 6, and 7, respectively.
Potential multimedia environmental impacts
were determined under a separate contract
(68-02-2695) by GCA/Technology Division.
This program, which followed  protocols
developed by EPA, characterized in detail the
chemical composition of the  three major
streams discharged from the CAFB: boiler
flue gas, spent lime sorbent, and ash from
the sulfur recovery system.
  The major environmental conclusions of
the demonstration programs follow.
  • NOX emissions from the combustion of
    product gas generated by gasification of
    oil, lignite, or bituminous coal were con-
    sistently below 100 ng/J (0.233 lb/108
    Btu) and were lower than NOX emis-
    sions from natural gas combustion.
  • During  oil  gasification,  the  sulfur
    removal efficiency (SRE) varied from 60
    to  90  percent.  The SRE decreased
    markedly as the gasifier bed temperature
    was raised above 870°C. Recycling of
    RESOX™  tail gas to the gasifier
    decreased  SRE, probably  as a conse-
    quence of steam  and elemental sulfur
    entrained in the tail gas.
  • Particulate emissions during oil gasifica-
    tion averaged 31.3 ng/J (0.073 lb/10«
    Btu) based on the results  of five EPA
    Method 5 tests. Opacity was generally
    below 20 percent. However, the higher
    than anticipated elutriation rate of bed
    material from the gasifier resulted in ex-
    cessive paniculate buildup in the boiler.
    Periodically this material would be blown
    off the boiler tubes by increasing the gas
    flow to the boiler, resulting in momen-
    tary jumps in opacity.
  • Particulate collected from the boiler flue
    gas showed neither appreciable toxici-
    ty nor any positive mutagenicity.
  • Some mutagenicity was indicated by an
    Ames test on extracts of XAD porous
    polymer resin used to collect samples of
    gaseous organic compounds from the
    flue gas.
  • Leachates  collected from the  spent
    stone and RESOX™ ash contained low
    metal and anion concentrations. Anion
    concentrations in both leachates were
    well below EPA Primary and Secondary
    Drinking Water Regulations.
Rebecca E. Sommer and Arthur S.  Werner are with GCA/Technology Division,
  Chapel Hill, NC 27514; Z. Kowszun is with Esso Research Centre, Abingdon,
  Oxfordshire, OX136AE. England.
Samuel L. Rakes is the EPA Project Officer (see below).
The complete report, entitled "Evaluation and Demonstration of the Chemically
  Active Fluid Bed," (Order No. PB84-159 243; Cost: $ 19.00, 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
                                   U.S GOVERNMENT PRINTING OFFICE, 1984 — 759-015/7640

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