United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-92/196 December! 992
EPA Project Summary
Effects of E-SOX Technology on
ESP Performance
G.H. Marchant, Jr., J.P. Gooch, and M.G. Faulkner
This report describes field measure-
ments and supporting laboratory stud-
ies related to the development of the
flue gas cleanup process known as E-
SOx. It describes work performed as a
part of pilot-scale studies of the E-SOX
process at Ohio Edison's Burger Sta-
tion.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The E-SOX process involves removal of
sulfur oxides prior to the inlet of an elec-
trostatic precipftator (ESP) with an aque-
ous spray of an alkaline material. The
entering fly ash and resultant particulate
matter are then removed in the ESP. A
research program to develop and demon-
strate the process has been performed
under the sponsorship of the U.S. EPA,
the Ohio Coal Development Office, and
the Babcock & Wilcox Company (B&W).
Slaked lime slurry without the use of
recycled material was the source of alka-
linity for all experiments. Pebble lime was
transferred pneumatically from tank trucks
to a storage bin, and the lime was then
slaked and placed in a slurry tank. The
slurry was metered and injected into a
spray chamber through two B&W Mark 4
nozzles. Dilution water was added to the
slurry prior to reaching the nozzle, de-
pending on the calcium to sulfur ratio and
approach to saturation desired. At the exit
of the spray chamber and ahead of the
ESP are two rows of Droplet Impingement
Devices (DIDs) which are temperature-
controlled pipes to prevent entry of large
wet particles into the ESP. The flue gas
and uncollected particulate matter which
exited the ESP were returned to the main
ductwork ahead of the main unit's ESP.
Measurement Program
The ESP, the fly ash, and fly ash/sor-
bent mixtures were characterized by mea-
suring:
• Inlet and outlet mass concentrations,
• Inlet and outlet mass vs particle sizes
with cascade impactors,
• Real-time outlet mass concentration
trends with an Environmental Systems
Corporation PSA mass emissions
monitor,
• Secondary voltage-current relation-
ships and operating points,
• Inlet velocity traverses,
• Inlet and outlet temperature traverses,
• Laboratory and in situ resistivity,
• Chemical analysis of bulk and size-
fractionated samples, and
• Ash cohesivity and Bahco particle
size.
Baseline measurements were performed
without the DID array.whereas the sor-
bent injection tests necessarily were per-
formed with the DID array. In addition to
preventing penetration of large moist par-
ticles into the first field of the ESP, the
DID array minimized gas velocity non-uni-
Printed on Recycled Paper
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formlty due to flow disturbances caused
by the sorbent injection nozzles.
Emissions caused by rapping systems
in pilot-scale ESPs are usually not repre-
sentative of full-scale systems. Therefore,
the test program was conducted with rap-
ping systems de-energized during the time
period that outlet measurements were un-
derway. Rappers were energized between
tests to avoid excessive electrode build-
ups. This testing strategy allowed the over-
all and particle size dependent efficien-
cies to be compared with the "no rap"
projections of the mathematical model.
Since the first test series with sorbent
injection indicated that participate emis-
sions exceeded the program goal of 0.1
lb/109 Btu (43 ng/J), a second test series
was performed following an effort to Jm-
prove the gas velocity and temperature
distributions at the ESP inlet.
Conclusions
1. Analysis of particle size fractions
collected on impactor stages at the
inlet and outlet of the E-SOX ESP
showed a large increase in the rela-
tive calcium content of the finer size
fractions across the ESP.
2. Massive reentrainment of ash/sor-
bent mixtures could be induced
without electrode rappers in ser-
vice by lowering the operating tem-
perature of the ESP inlet. The
reentrainment could be reduced by
elevating the average inlet operat-
ing temperature 10 to 20°F (5.5 to
1 _1°.C)~with- no accompanying-
G. H. Marchant, Jr., J.P. Gooch, andM.G. Faulkner are with Southern Research
Institute, Birmingham, AL 35255-5305.
Louis S. Hovls is the EPA Project Officer (see below).
The complete report, entitled "Effects of E-SOXTechnology on ESP Performace,"
(Order No. PB93-107258/AS; 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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
change in secondary voltage and
current.
3. ESP performance for the E-SOX
process, as evaluated at the Burger
station with the coal, lime, and con-
ditions present during testing, is
dominated by two factors not rep-
resented in the existing EPA-SRI
versions of the mathematical model
of ESP performance: instantaneous
reentrainment of low resistivity ash/
sorbent particles and deagglomer-
ation of slurry residue within the
ESP.
4. Significant improvement of the ve-
locity and temperature profiles
downstream from the DID array al-
lowed outlet particulate emissions
- " ' to be reduced urleiss-triam).ribT
10s Btu with 50% SO2 removal.
However, the severe reentrainment
problem within the ESP was still
present, especially at temperatures
below 160°F (71 °C).
5. Additional Work would help develop
a quantitative understanding of the
chemical and physical properties of
slurry residues which result in poor
ESP performance. Slurry additives
designed to increase dust layer ten-
sile strength and reduce reentrain-
ment showed no beneficial effects
during the brief test periods that
were possible in the current pro-
gram. Additional testing with these
additives could involve longer term
and more stable process operating
conditions.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
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POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-92/196
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