United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S9-84-025a Mar. 1985
&ER& Project Summary
Fourth Symposium on the
Transfer and Utilization of
Paniculate Control Technology:
Volume I. Fabric Filtration
F. P. Venditti, J. A. Armstrong, and M. D. Durham
Summarized herein is Volume I of
three volumes of proceedings of the
Fourth Symposium on the Transfer and
Utilization of Particulate Control Tech-
nology held in Houston, Texas, October
11-16,1982. Volume I papers discuss
theoretical and applied aspects of fabric
filtration. Volumes II and III are des-
cribed in two separate project sum-
maries.
This Project Summary was developed
by SPA's Air and Energy Engineering
Research 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
The papers in these three volumes of
proceedings were presented at the Fourth
Symposium on theTransfer and Utilization
of Particulate Control Technology in
Houston, Texas, October 11-15, 1982,
sponsored by the Particulate Technology
Branch of the Environmental Research
Laboratory of EPA at Research Triangle
Park, NC.
The symposium brought together re-
searchers, manufacturers, users, govern-
ment agencies, educators, and students
to discuss new technology and provided
an effective means for the transfer of this
technology out of the laboratories and
into the hands of the users.
The two major particle control tech-
nologies—fabric filters and electrostatic
precipitators (ESP's)—were the primary
concern of the symposium. These tech-
nologies were discussed from perspec-
tives of economics, new technical ad-
vancements in science and engineering,
fundaments, and applications. Several
papers dealt with the interaction of sulfur
dioxide control and paniculate control.
Additional topic areas included mechan-
ical collectors, coal characterization, in-
halable particulate matter, novel devices,
and advanced energy applications for
particulate control.
The symposium was conducted as a
series of parallel sessions, each contain-
ing four to six related papers. The sessions
were scheduled to avoid conflict due to
simultaneous sessions dealing with the
same topic. Each series of related ses-
sions represented a thread of technology.
These parallel threads, extending over
the total period of the symposium, pro-
vided a highly integrated approach to the
total subject of particulate control tech-
nology with strands of specialized tech-
nologies. These strands of specialized
technologies, or perspectives, provided
the basis for the division of the papers
into three volumes, each volume contain-
ing a set of related session topics so as to
provide easy access to a unified tech-
nology area.
Volume I Papers
Volume I, summarized here, is a collec-
tion of papers describing various aspects
of fabric filtration. One section includes
papers dealing with the theoretical and
fundamental aspects of fabric filtration.
Specialized measurement techniques for
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various aspects of fabric filtration includ-
ing pressure drop, dust layer thickness,
and bag strength are described in a series
of papers. Several papers deal with the
application of baghouses to coal-fired
boilers. Both pulse jet and reverse air
systems are discussed, and data are
presented from pilot-scale test devices
and full-scale installations. One section
deals entirely with results from several
research projects on improvements pro-
duced through electrostatic enhancement
of fabric filtration. Results are presented
for enhancement by application of electric
fields at the bag surface and by means of
precharging the particles. Practical as-
pects of fabric filtration are covered in a
section dealing with bag cleaning strate-
gies, startup procedures, and air flow
design. A final section of papers deals
with combined 802 and particulate con-
trol using spray dryers in combination
with fabric filtration.
Section A—Fabric Filters:
Fundamentals
Theory of the Temporal
Development of Pressure Drop
Across a Fabric Filter During
Cake Initiation
Eric A. Samuel
General Electric Environmental Services,
Inc.
The time variation of the pressure drop
across a fabric filter characteristic of cake
initiation in a new fabric as well as in a
seasoned fabric is derived on the basis of
the Carmen-Kozeny hypothesis, which is
well known for its prediction of the linear
growth of pressure drop with time char-
acteristic of cake filtration. The non-linear
growth of pressure drop during cake
initiation in a new fabric is associated
with the filling of the voids within the
fabric prior to cake establishment. The
non-linear growth of pressure drop dur-
ing cake initiation in a seasoned fabric is
associated with non-uniform dust loading
on the fabric. The non-uniform loading
may either be an initial condition follow-
ing cleaning, or be induced by inertia! or
external forces. Experimental evidence in
support of the theory is presented.
Pulse Jet Filtration Theory—
A State-of-the-Art Assessment
Richard Dennis
GCA/Technology Division
Louis S. Hovis
Air and Energy Engineering Research
Laboratory, U.S. Environmental
Protection Agency
The relevant literature on pulse jet filter
theory and applications was assessed to
develop coherent guidelines for designing
predictive filter models. Observations of
several foreign and U.S. researchers not
previously subjected to rigorous compar-
isons showed that there is a considerable
unanimity in technical perspectives when
data and theories are viewed from a
common baseline. Common misconcep-
tions are clarified such as (a) the "air
bubble" that descends through the bag
during pulsing, (b) dust removal by air
flushing rather than mechanical protec-
tion from a rapidly decelerating fabric,
and (c) failure to recognize that only a
small (1-5 percent) fraction of dust dis-
lodged by pulse action actually reaches
the hopper. Data from several sources
suggest that not only the compressed air
pressure, but also the rate of pressure
rise within a bag and the fabric mobility
determine dust removal effectiveness.
Unique pairings of pressure intensity and
dust dislodgeability (as defined by dust/
fabric adhesive properties) appear es-
sential for complete removal of surface
dust layers. When air jets are correctly
placed for specified pulse jet parameters,
the surface dust layer should be com-
pletely dislodged. Various investigators
also suggest that the residual dust (i.e.,
the irreversibly embedded dust) is rel-
atively constant for fixed dust/fabric
combinations.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and administra-
tive review policies and approved for
presentation and publication.
Laboratory Techniques for
Developing Pulse Jet Collectors
Robert R. Banks
John T. Foster
Wheelabrator-Frye Inc., Air Pollution
Control Division Technical Center
A major factor in the performance of a
pulse jet collector is its effectiveness in
using compressed air. The manifold con-
figuration, venturi design and other fac-
tors determine this effectiveness. To
expedite the study of these factors over a
wide range, two sets of apparatus were
built.
The first, the impact force tester, meas-
ures the momentum of the air pulse from
each hole in a manifold and the pressure
along the manifold. The momentum o|
the jets can be equalized by varying the
hold size along the manifold.
The second test rig measures the
characteristic of the ejector or jet pump
formed by the air jet and venturi so that
the geometry of this part of the systerr
can be optimized. Jet pump curves were
found to predict relative performance as
measured in a laboratory pilot collector
Testing by these methods takes only <
fraction of the time required using a pilo
collector. Data from tests leading to ar
optimum pulse jet cleaning system desigi
will be shown.
Off-Line Pulse-Jet
Cleaning System
Thomas C. Sunter
C-E Air Preheater, Division
of Combustion Engineering, Inc.
The paper discusses off-line pulse-jc
cleaning systems by formulating a set c
simplified mathematical equations t
describe the cleaning process. A compu
er model is developed from the equatior
and manipulated to simulate both tim<
based and differential pressure-base
control of the pulse-jet system.
Practical application of this informatic
is discussed as it affects system contrc
bag life, energy consumption and syste
operation.
Section B—Fabric Filter:
Measurement Techniques
Field Evaluation of the Drag 01
Individual Filter Bags
W. T. Grubb
R. R. Banks
Wheelabrator-Frye Inc.
Air Pollution Control Division,
Technical Center
Evaluation of the performance of filti
tion fabrics has heretofore necessitate!
full compartment test, as only gene
observations could be made using a fi
test bags.
Compact, inexpensive, readily portal
equipment was developed to measure 1
filter drag of a single bag by blowini
metered flow of ambient air through 1
bag and measuring the pressure dr
The test apparatus is set up in 1
baghouse compartment to minimize c
turbance to the bag and its dust cake.
Test results show reproducibility i
statistically significant differences ami
bags made of different cloths and
different sites. Evaluation of the per
mance of various filter fabrics on
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lasis of a limited number of trial bags is
possible. Selected data will be presented
reflecting experience with tests on fiber-
glass and synthetic bags in five large
utility collectors.
A Dual-Detector Beta Particle
Backscatter Gauge for
Measuring Dust Cake
Thickness on Operating
Bag Filter and ESP Units
Robin P. Gardner
Center for Engineering Applications of
Radioisotopes
R. P. Donovan
Process and Chemical Engineering
Division, Research Triangle Institute
L S. Hovis
Utilities and Industrial Process Division
Air and Energy Engineering Research
Laboratory, U.S. Environmental
Protection Agency
To avoid the use of moving mechanical
parts in the hostile environment of dust
collection that is necessary with the dual-
beam beta-particle backscatter gauge, an
alternative measurement principle has
been sought that still allows the measure-
ment of dust cake density thickness
'ndependent of distance from the device.
It is found that the use of a dual-detector
system, in which each detector detects
the response of a different part of the
backscattered beta-particle spectra from
a single radioisotope source, can be used
o accomplish this.
The system investigated here consists
of a Sr-90 source and two thin end-
window GM counters, one covered with a
iimple paper filter with density thickness
of 0.050 g/cm2. The two responses
obtained differ significantly with dust
:ake density thickness so that models of
lach response can be solved simultan-
lously for two experimental responses to
ive dust cake density thickness inde-
>endent of distance from the device.
.aboratory results on a prototype device
jsing paper samples of known density
hickness to simulate dust cake density
hickness yield standard errors of 0.0278
nd 0.0151 g/cm2 for bag filter and ESP
jnit configurations, respectively. The
•ange of distances and simulated dust
:ake density thickness investigated were
.4 to 7.4 cm and 0 to 0.2133 g/cm2,
•espectively.
This paper has been reviewed in ac-
:ordance with the U.S. Environmental
'rotection Agency's peer and adminis-
rative review policies and approved for
iresentation and publication.
MIT Flex Endurance Tests at
Elevated Temperature
John T. Foster
W. Theron Grubb
Wheelabrator-Frye Inc.
Air Pollution Control Division
Technical Center
The MIT flex endurance test, originally
devised for paper, is used to evaluate the
fatigue life of woven filtration fabrics.
This test is used in predicting the relative
life of fiberglass fabric filter bags and in
the development of finishes. In the past,
MIT flex data has been published only for
tests conducted at ambient (room) tem-
perature. Fiberglass filter bags, however,
are used at operating temperatures up to
550°F. Since the physical properties of
the finishes which protect the cloth
change with temperature, MIT flex tests
conducted at the operating temperature
of the cloth should provide more meaning-
ful data.
An MIT flex tester designed to meet the
specifications of ASTM method 02176,
and to operate at temperatures as high as
600°F, has been built and tested. A
relationship between flex endurance and
operating temperature for several com-
mercially finished fiberglass fabrics is
present.
The One-Point In-Situ
Calibration Method for Using a
Beta-Particle Backscatter
Gauge for Continuously
Measuring Dust Cake
Thickness on Operating Bag
Filter and ESP Units
Robin P. Gardner
Center for Engineering Applications of
Radioisotopes
R. P. Donovan
Process and Chemical Engineering
Division, Research Triangle Institute
L S. Hovis
Utilities and Industrial Processes
Division, Air and Energy Engineering
Research Laboratory
U.S. Environmental Protection Agency
An alternative to using the dual-beam
beta-particle backscatter gaugeto contin-
uously measure dust cake thickness on
operating bag filter or electrostatic precip-
itator (ESP) units independent of gauge
distance from the dust, a one-point in-
situ calibration method for using a simple
beta-particle backscatter gauge, is de-
veloped and demonstrated. The method
consists of obtaining a response model
for beta-particle backscatter in terms of
dust cake density thickness (areal den-
sity), distance from the gauge, and either
bag filter or collector plate density thick-
ness. Then, assuming that the density
thickness of the bag filter or the collector
plate (on the ESP unit) without dust is
either known or (for the ESP) larger than
the saturation value for the beta-particle
source being used, the initial gauge
response before dust is present can be
used to establish the gauge distance to
the bag filter or collector plate.
This approach has been investigated in
the laboratory with a system consisting of
a Sr-90 beta-particle source and an end-
windowGeiger-Mueller(GM) tube detect-
or. The ranges of distances and simulated
dust cake density thicknesses investi-
gated were 3.4 to 7.4 cm and 0 to0.2133
g/cm2, respectively. The accuracies con-
tained were quite good. For the bag filter
application, dust cake measurement ac-
curacies of 0.025 g/cm2 or better were
obtained for all distances up to 7.4 cm
and dust cake density thicknesses less
than 0.05 g/cm2. This assumes counting
rate errors of 1 percent and an error in the
measurement of the bag filter density
thickness of 5 percent. For the ESP
application the dust cake measurement
accuracies for the equivalent error as-
sumptions were even better, ranging
from 0.0012 to 0.017 g/cm2 for all
distances and dust cake thicknesses
investigated. This excellent accuracy for
the ESP application is in part due to the
basic sensitivity for this case (slope of the
calibration curve) and in part because
there is no error introduced by variations
in the ESP collector plate thickness. The
accuracies for both applications have
been significantly improved by removing
the rotating shield superstructure greatly
reducing the background response re-
ported for the predecessor dual-beam
gauge.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and administra-
tive review policies and approved for
presentation and publication.
Section C—Fabric Filters:
Coal Fired Boilers
Pulse-Jet Fabric Filter
Experience Using Non-Glass
Madias at Air to Cloth Ratios of
5 to 1 on a Pulverized Coal
Fired Boiler
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G. L. Pearson
D. D. Capps
Adolph Coors Company
A 12-module baghouse system using
the Carter-Day high temperature module
has been in service since November
1979 controlling emissions from the
450,000 Ib/hr Boiler No. 5 unit. Bags
were made of felted "Ryton" and cleaning
is accomplished via a low pressure-mod-
erate volume, pulse-jet technique.
Experience to date with this baghouse
system will be presented. Data on pres-
sure drop, cleaning cycles, cleaning
frequency, bag life experience and panic-
ulate emissions will be reviewed. Results
of on-line evaluation of felted FBI bags
will also be presented.
Prepared for Presentation at the Fourth
Symposium on the Transfer and Utiliza-
tion of Particulate Control Technology
Sponsored by the U.S. Environmental
Protection Agency and held in Houston,
Texas, October 11-15, 1982.
Start-Up and Operation of a
Fabric Filter Controlling
Particulate-Emissions from a
250 MW Pulverized Coal-Fired
Boiler
Charles B. Barrangsr
Flakt, Inc.
John Saibini
Sierra Pacific Power Co.
Norm Spence
Stone and Webster
Summarize and describe the design,
construction, start-up and operation of
the fabric filter baghouse controlling the
particulate emissions from Boiler Unit
No. 1 located at Sierra Pacific Power,
North Valmy, Nevada. The basic design
specification requirements will be des
cribed, i.e., fuel type, flue gas, fabric filter
type, system arrangement and perfor-
mance requirements. Actual pre-start
checkout and system start-up procedure
will be reviewed in detail. The fabric filter
was put on-line in November of 1981.
Resulting equipment operating conditions
from start-up through date of the paper
will be presented.
Performance of a 10 MW
Fabric Filter Pilot Plant and
Comparison to Full-Scale Units
Wallace B. Smith
Kenneth M. Gushing
Southern Research Institute
Robert C. Carr
Electric Power Research Institute
This paper provides an update on
EPRI's fabric filter research .program
currently being conducted by Southern
Research Institute of the Arapahoe test
facility in Denver, Colorado, and also
several full-scale installations. Data are
reported which suggest a quantitative
relationship between tube-sheet pres-
sure drop and air-to-cloth ratio for
reverse-gas cleaned baghouses. Typical
results show that average tube-sheet
pressure drop increases from 4.5 to 8 in.
H20 (1.12 to 2.0 kPa) as the air-to-cloth
ratio increases from 1..7 to 2.5 acfm/ft2.
Large residual dust cakes of up to 1 Ib/ft2
(about 500 mg/cm2) were measured in
the bags after cleaning by reverse gas.
Current tests indicate that approximately
a 20 percent reduction in operating
pressure drop could be achieved by
increasing the reverse-gas velocity to 6
ft/min (3 cm/sec), although such a high
value may be impractical for full-scale
units. These results suggest that reverse-
gas alone is only marginally effective as a
method of cleaning bags in utility appli-
cations. Applying intense sonic energy
(horns) during reverse-gas cleaning re-
sults in much better dust cake removal.
Tests now underway indicate that this
hybrid bag cleaning mode can reduce the
operating pressure drop by more than a
factor of two.
The Design, Installation, and
Initial Operation of the
W. H. Sammis Plant
Unit 3 Fabric Filter
Dennis R. Ross, P.E.
Generating Plant Staff Engineer
Ohio Edison Company
James R. Howard
Plant Engineer
W. H. Sammis Plant
Ohio Edison Company
R. Mark Golightley
Plant Engineer
W. H. Sammis Plant
Ohio Edison Company
This paper will discuss the design
philosophy and preliminary operating
experience of the first unit of four units to
be retrofitted with fabric filters at the W.
H. Sammis Plant. Each unit is 180 MW
net. The unit was operational in late
August 1982.
The paper will identify design criteria
initially specified, design enhancements
during the course of the project, construc-
tion highlights, and preliminary operating]
experience. Results from the first months
of operation will include pressure drop
and opacity. In addition, start-up, shut-
down, and maintenance procedures will
be discussed.
Results from the Fabric Filter
Evaluation Program of Coyote
Unit#1
H. James Peters
Arthur A. Re/singer
W. Theron Grubb
Wheelabrator-Frye Inc.
Air Pollution Control Division and
Merrill Lewis
Montana Dakota Utilities
The fabric filter at Coyote Unit #1 has
been in service since May 1981 collecting
lignite fly ash and sodium-based sprav
dryer product as the second stage of the
dry scrubbing system installed by the
Wheelabrator-Frye Inc./Rockwell Inter-
national joint venture.
A program is being conducted to eval-
uate the performance of acrylic, polyester
Nomex, and fiberglass filtration fabric;
and operates at filter ratios of typically 3:1
using combination deflation air an<
mechanical shaking as the fabric cleanin;
method.
This paper highlights the results of thi
fabric evaluation program to date includ
ing comparisons of the pressure drop
throughput, replacement history, filtra
tion parameters, and changes in physica
properties of the various fabrics over thi
first year of operation. Discussion of thi
overall performance of the unit am
economic and technical consideration:
for fabric selection is also covered.
Baghouse Performance and
Ash Characterization at the
Arapahoe Power Station
Robert S. Dahlin
Southern Research Institute
D. Richard Sears
U.S. Department of Energy
George P. Green
Public Service Company of Colorado
This paper presents the results of
field test conducted in March 1981 onth
Unit 3 baghouse of the Arapahoe Static
of the Public Service Company of Cole
rado. The unit was burning a subbiturr
inous coal from Routt County, Coloradi
and was retrofitted with a baghouse i
1979. Baghouse performance was four
to be excellent with an overall mas
efficiency of 99.98 percent. The estimate
4
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cumulative collection efficiency of all
particles smaller than two microns was
99.92 percent.
The average electrical resistivity of the
fly ash was found to be 6 x 10" ohm-cm at
266°F. This was consistent with the low
level of S03 found in the flue gas (~0.3
ppm). The measured resistivity agreed
reasonably well with that predicted by
Bickelhaupt's technique using the anal-
ysis of the ash obtained by atomic absorp-
tion spectrometry. These results suggest
that a high SCA and possibly flue gas
conditioning would be required to obtain
the same collection efficiency from an
ESP.
A microanalvtical characterization of
ash elemental and mineral composition
has been performed. Using SEM, detailed
major element analyses for —240 indi-
vidual ash particles have yielded concen-
tration frequency distributions and com-
position as a function of particle size, and
inter-element concentration correlations.
The results have been correlated with
coal and ash mineralogy. Suggestions are
made concerning possible application of
this data to practical problems of fly ash
control and disposal.
An Evaluation of Full-Scale
Fabric Filters on Utility Boilers
John W. Richardson
John D. McKenna
John C. Mycock
ETS, Inc.
The objective of this EPA-sponsored
program was to determine the particulate
emission concentrations of a coal-fired
electric utility of greater than 100 MW
output. Tests were also conducted to
determine gaseous constituent concen-
trations of the flue gas and particle size
via a cascade impactor.
Testing was conducted at Southwest-
ern Public Service's Harrington Station,
Unit 3, between July 6, 1981, and July
11, 1981. A total of three (3) outlet tests
and one (1) inlet test were performed.
Due to the absence of inlet test ports,
inlet testing was done by bypassing the
baghouse and testing at the outlet ports
of the stack.
Emissions for Unit 3 are controlled by
two (2) baghouse systems, an east and a
west, each with its own operating control
system and bypass dampers for start-
ups, emergency operation and shutdown.
Each system incorporates shake/deflate
cleaning, and consists of 32 compart-
ments with 204 bags per compartment
for a total of 6,528 bags.
Average outlet concentration resulted
in a lower than expected value of 0.007
lbs./106 Btu. The loading of the inlet
testing was 2.0 lbs./106 Btu giving a
99.65% collection efficiency for the bag-
house. This emission rate is significantly
lower than the existing Federal standard
of 0.03 lbs./106 Btu. Particle sizing tests
indicated that the mass geometric mean
diameter for outlet tests 1 through 3
ranged from 7.5 to 13 /urn with an
extrapolated inlet mass diameter of 60
yum, and a baghouse collection efficiency
of 99.86%.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Status ofSPS Investigation of
Harrington Station Unit 2
Fabric Filter System
Richard Chambers
Southwestern Public Service Co.
Dale Harmon
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
This paper describes activities during
the fourth year of the SPS/EPA fabric
filtration study at Harrington Station. The
scope of the overall study and its purposes
were outlined in earlier papers.
During the fourth year of this project,
sufficient information was available to
make certain comparisons between Har-
rington Station's high air-to-cloth ratio
(3.4 ft/min) shake/deflate fabric filter
system and low air-to-cloth reverse air
units. Specifically, comparison of bag life
economics and pressure drop perform-
ance is addressed. Sizing of reverse air
and shake/deflate baghouses is dis-
cussed in light of current operating data
from Harrington Station and other instal-
lations.
Operation and maintenance costs are
shown for the Harrington Unit 2 fabric
filter system, and suggestions for im-
proved shaker design are given. Plans to
investigate sonic augmentation of bag
cleaning are described.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Update of SPS Pilot
Baghouse Operation
Richard Chambers
Sherry Kunka
Southwestern Public Service Co.
Date Harmon
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
An option of the 1977 Environmental
Protection Agency (EPA) contract, with
Southwestern Public Service Company
(SPS) to assess the performance of a
large prototype fabric filter system pro-
vided for the installation of a pilot bag-
house. The pilot unit was placed in
service in October 1979. This paper
describes the test program being con-
ducted in the pilot unit by SPS for the
EPA. These test programs to date have
primarily involved the evaluation of the
filtration characteristics of a number of
fabrics in both the shake/deflate and
reverse air cleaning modes.
This paper has been reviewed in accord-
ance with the U.S. Environmental Protec-
tion Agency's peer and administrative
review policies and approved for presen-
tation and publication.
The Use of Sonic Air Horns as an
Assist to Reverse Air
Cleaning of a Fabric Filter
Dust Collector
Alan R. Menard
Ft. Mark Richards
Public Service Company of Colorado
A detailed summary of the installation,
test program, and performance of sonic
air horns used as an assist to reverse air
cleaning of an operating FFDC is pre-
sented. Four sonic air horns were in-
stalled and tested on compartment num-
ber 11 of Public Service Company of
Colorado's Arapahoe Unit #3 FFDC. The
overall objective of the test program was
to reduce the pressure drop across the
tube sheet of the test compartment.
Sonic cleaning reduced the compartment
tube sheet differential pressure by ap-
proximately 27 percent; this was suf-
ficient to warrant the purchase and
installation of two (2) sonic air horns in
each of the 14 baghouse compartments.
Section D—Fabric Filters:
Electrostatic Enhancement
"Electrostatic Stimulation of
Reverse-Air-Cleaned
Fabric Filters"
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D. A. Furlong
G. P. Greiner
ETS, Inc.
D. W. Van Osdell
Research Triangle Institute
L S. Hovis
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
The concept of electrostatic stimulation
of fabric filtration (ESFF) has been invest-
igated on a slipstream of a pulverized-
coal-fired boiler using reverse-air-
cleaned, woven-fiberglass filter bags.
Operation was demonstrated using ESFF
at a gas-to-cloth ratio (G/C) of 6 ft/min.1
An un-electrified control house was
simultaneously operated at a G/C of 3
ft/min. Under these conditions, the ESFF
house maintained a pressure drop equal
to or less than the control baghouse. In
addition to reducing the filter cake pres-
sure drop, ESFF was observed to ap-
parently have long-term benefits in pre-
venting irremovable dust buildup in the
fabric.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Electrical Stimulation of
Fabric Filtration:
Enhancement by Particle
Precharging
George E. Lamb
Richard I. Jones
William B. Lee
Textile Research Institute
The reductions in pressure drop that
accompany the establishment of a strong
electric field near a filter fabric appear to
be due to three separate mechanisms.
One is the formation of a more porous
dust cake due to dust capture in the low
packing density regions of the fabric. A
second mechanism is attraction of part-
icles to the bag wall which causes the bag
to act like a precipitator. The thickness of
dust cake is then greater near the en-
trance than at the end of the bag, and this
results in a lower pressure drop. The third
mechanism involves attraction of parti-
cles to the bag electrodes. The dust is
then deposited in bands with relatively
thin deposits in between. Measurements
'Readers more familiar with metric units
may multiply ft/min by 0.305 for the
equivalent m/min.
and visual inspections of the dust de-
posits indicate that the second and third
effects are enhanced when the aerosol is
charged. A particle charger of new design
appears to be particularly suitable for this
purpose, and is found to cause major
changes in filtration performance.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
ESFF as a Field Effect
L. S. Hovis
G. H. Ramsey
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
R. P. Donovan
Research Triangle Institute
Evidence to suggest that the mechan-
ism on which ESFF (electrostatic stimula-
tion of fabric filtration) depends is an
electric-field-only mechanism (as op-
posed to a Coulomb mechanism that
depends on both electric field and electric
charge) includes:
1. A room-temperature high-humidity
factorial experiment in which both
external electric field and fly-ash
electrical charge were independent
variables.
2. Selected experiments carried out at
low relative humidity and room
temperature.
3. Enhanced filtration measurements
made with a 60-Hz ac electric field
applied to the bag electrodes.
4. Published precharging data of oth-
ers in which enhancement vanish-
es at high relative humidity.
All of the data collected in EPA/IERL's
Research Triangle Park laboratory (items
1 -3, above) refer to experiments in which
pulverized coal fly ash was the dust
source. Dusts from other sources were
used in the experiments of item 4.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Electrical Enhancement of
Fabric Filtration:
Precharging Vs. Bag Electrodes
R. P. Donovan
Research Triangle Institute
L. S. Hovis
G. H. Ramsey
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
Two distinct approaches to achieving
electrically enhanced fabric filtration are:
(1) upstream precharging in a corona
discharge; and (2) dust filtration in an
external electric field applied by elec-
trodes woven into or positioned adjacent
to the bag. Both techniques have demon-
strated performance enhancement by
some measure, but the mechanisms of
enhancement may differ; clearly the
hardware does.
This paper reviews the hardware op-
tions and configurations available with
each basic approach and summarizes
various mechanisms whereby each ap-
proach brings about an electrical en-
hancement, including those which dom-
inate in combined precharge/bag elec-
trode systems. From this background,
guidelines for matching configurations to
source properties are suggested, as well
as a hybrid electrostatic precipitator
(ESP)/fabric filter design incorporating
features that enable it to operate as
either an electric-field aided baghouse or
a hybrid ESP/baghouse.
This paper has been reviewed in accord-
ance with the U.S. Environmental Pro-
tection Agency's peer and administrative
review policies and approved for pre-
sentation and publication.
Permeability of Dust Cakes
Collected Under the
Influence of an Electric Field
D. W. VanOsdell
R. P. Donovan
Research Triangle Institute
D. A. Furlong
ETS, Inc.
L. S. Hovis
Air and Energy Engineering Research
Laboratory
U.S. Environmental Protection Agency
The reductions in dust cake flow re-
sistance and residual pressure drop that,
can be achieved by electrostatic stimula-
tion of fabric filtration (ESFF) have been
documented. The changes in the dust
deposition characteristics which cause
these improvements are not well under-
stood. This paper presents results from
three investigations into the nature of
dust deposits collected with ESFF. Per-
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meability data collected at various axial
positions along ESFF and conventional
bags were the basis of the first study. The
second study concerned the deposition
patterns of dust collected on a laboratory
filter when ESFF was in use, and the
third, the resistance to compression of
the collected dust with and without an
electric field.
These investigations gave evidence that
ESFF caused the formation of a residual
dust deposit which was not axially uni-
form (the permeability at the bottom of
the bag was half that at the top) and was
more easily removed than a conventional
dust deposit. In the laboratory, it was
shown that ESFF caused newly collected
dust to form very nonuniform deposits.
The dust tended to collect near the
electrodes, in patterns which have not
been observed in the pilot units. In the
third study, the ESFF electric field was
found to improve the resistance to con-
solidation of the dust cake collected in a
pulse-jet pilot unit.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Section E—Fabric Filters:
Practical Considerations
"High Velocity Fabric
Filtration for Industrial
Coal-Fired Boilers"
Gary P. Greiner
Shannon Delaney
ETS. Inc.
Lou S. Hovis
U.S. EPA
AEERL. MD-61
Two parameters which dramatically
affect the technical/economic perform-
ance of a fabric filter system are gas/cloth
(G/C) ratio (or filtering velocity) and bag
life.
Under an EPA-sponsored contract, ETS,
. Inc. has been conducting a study of state-
of-the-art and experimental fabrics and
finishes in full-scale baghouses operating
on coal-fired boilers at the Kerr Finishing
Plant, Travelers Rest, South Carolina. The
objective of the study is to operate, test,
and evaluate performance at G/C ratios
up to 10/1 and screen various fabrics
with respect to pressure drop, collection
efficiency, and fabric strength charateris-
tics necessary for technical/ economic
analysis. Included in the program are
some revolutionary fabrics which hold
promise of technological breakthroughs.
This paper will discuss evaluation
methodology, performance results, and
future program plans.
This paper has been reviewed in ac-
cordance with the U.S. Environmental
Protection Agency's peer and adminis-
trative review policies and approved for
presentation and publication.
Optimizing the Location of
Anti-Collapse Rings in
Fabric Bags
John G. Musgrove
Bechtel Power Corporation
The number and placement of anti-
collapse rings in fabric filter bags are
frequently left to the bag manufacturers.
Bag manufacturers do not analyze operat-
ing requirements for determination of
ring location but merely subdivide the
bag into sections of approximately equal
length. Bags whose section lengths are
equal are suspected during reverse air
cleaning of having greater collapse (de-
flection) in lower sections than in higher
sections.
An analysis has been developed to
predict the amount of collapse (deflection)
in all sections of a bag undergoing
reverse air cleaning. The methodology
uses the catenary principle of a uniformly
loaded suspension cable to determine
deflection. A computer program utilizing
this methodology has been developed to
analyze the forces on a warp thread in a
bag and to determine the location of anti-
collapse rings to assure equal bag col-
lapse in all sections. A companion pro-
gram has been developed to predict bag
section collapse for bags with established
ring locations.
Pulse Jet On-Line Cleaning
Filter for Fly Ash
Wayne G. Wellan
Carter-Day Company
This paper describes the development
and performance of on-line cleaning by
pulse jet filters with needed felt. This
pulse jet filter design is in operation on
various types of coal-fired boilers. Con-
siderable research and testing was in-
volved in finding a fiber that would endure
continuous pulsing, high temperatures,
and a sulfur environment. Additional
research was required to develop the
proper filter media in the areas of needling
and scrim design. Also, analysis of various
types of fly ash was conducted to deter-
mine particle size and shape, and what
effect it has on the performance of the
filter.
Top Inlet Versus Bottom Met
Baghouse Design
Robert M. Jensen
Bechtel Power Corporation
This paper compares top inlet with
bottom inlet baghouse designs for bags
that collect on the inside. The comparison
includes performance data for top inlet
baghouses in service with comparable
bottom inlet performance.
The paper explains why pressure loss
predictions for top inlet may be more
reliable than for bottom inlet. Other
advantages claimed for top inlet are
higher cloth ratio for the same pressure
loss as bottom inlet; use of longer bags;
better utilization of unreacted reagent
after a spray dryer; and more efficient
cleaning with the reverse air.
The most important advantage of top
inlet design may be the apparent ability
for all bags to operate at a constant face
velocity in contrast to bottom inlet bags in
which the face velocity diminishes with
time on line after each cleaning.
Upgrade of Fly Ash Collection
Capability at the Cromby Station
T. J. Ingram
R. J. Biese
Gilbert/Commonwealth
R. 0. Jacob
Philadelphia Electric Company
A description is given of measures to
upgrade the dust collection capability of
28-year old Cromby Unit 1 in the interim
period before installation of an S02
scrubber. A novel approach was taken to
enhance the performance of outdated
equipment, resulting in continued usage
of existing mechanical collectors, up-
graded electrostatic precipitators, and the
addition of a sidestream baghouse to
accomplish the objective. The equipment
was installed and started up within a year
of writing specifications, and compliance
was attained. The paper discusses some
problems experienced, notably bag blind-
ing which has resulted in a severe
maintenance problem; steps in progress
to resolve the problem are discussed.
High Sulfur Fuel, Fabric Filter
Startup Experience
Phil Hanson
Power Production Manager
City Power and Light Department
-------
Larry Adair
Project Manager/Senior Engineer
Phelps and Phillips
Robert N. Roop
Product Manager
Research-Cottrell, Inc.
Robert B. Moyer
Manager Fabric Filter Applications
Research-Cottrell, Inc.
The long-term operation of fabric filters
on low sulfur fuels has been, with a few
exceptions, well demonstrated. Similar
experience on high sulfur coals has not
yet been gained. As utilities continue to
convert to coal, reliability of fabric filters
for high sulfur coal service will be of
paramount concern.
The City of Independence, Missouri,
recently put into service a fabric filter
designed for three to five percent sulfur
coal flue gases. Details of the design will
be discussed. Anticipating the opportun-
ity to test in real world conditions, a bag
evaluation program was initiated and is
in progress. Physical and mechanical
properties of the bag fabric are being
tested to determine the effects of high
sulfur service and a possible relationship
to bag life. Results of that bag test
program, as obtained to date, and its
implications will be presented.
Fundamental Strategies for
Cleaning Reverse Air
Baghouses
M. G. Ketchuck
M. A. Walsh
O. F. Fortune
M. L. Miller
G. E. Environmental Services, Inc.
M. A. Whittlesey
Adapco
In order to choose among the various
cleaning cycle strategies (Batch, Contin-
uous, and Distributed) used for utility
reverse air cleaned baghouses, it is
necessary to understand the fundamen-
tals of the cleaning process. This paper
describes both analytical and experiment-
al investigation of fundamental mechan-
ics common to all cleaning strategies.
Section F—Dry Scrubbers
Design Considerations for
Baghouse-Dry SO2 Scrubber
Systems
Owne F. Fortune
Richard L. Miller
G. £. Environmental Services, Inc.
The combination of a reverse air
cleaned baghouse and a dry sulfur dioxide
scrubber is attractive because of the ease
with which the baghouse can remove
over 99.9% of the high solids loading in
the gas stream exiting the scrubber, and
because sulfur dioxide scrubbing con-
tinues to occur in the filter-cake on the
bags. However, in order to avoid having
gypsum deposits shortening the usable
life of the bags, close attention has to be
paid to several design considerations.
Among them are system response to
boiler tube leaks, approach to saturation
temperature, reheat system, avoidance
of condensation in reverse air cleaning
system, plant maintenance problems,
changing boiler loads, and changing
sulfur dioxide concentrations. Exper-
ience-based design strategies to deal
with these issues are discussed in this
paper.
Results of Baghouse and
Fabric Testing at Riverside
H. W. Spencer III
Y. J. Chen
M. T. Quach
Joy Manufacturing Company
Western Precipitation Division
This paper presents the results of one
year of baghouse and fabric testing at the
Riverside Dry FGD Demonstration Facility
during 1981. Operating parameters and
baghouse performance data are summar-
ized. The results of the fabric evaluation
test are discussed. Pressure drop meas-
urements are reported and pressure drop
predictions for various fabric filters based
on the experimental data are compared.
Pressure drop predictions are compared
with overall baghouse pressure drop.
Good agreement between the predicted
values and the actual measurements are
reported. Measurements reported in the
paper cover operation with three different
coals.
Reactivity of Fly Ashes in a
Spray Dryer/Fabric Filter FGD
Pilot Plant
Wayne T. Davis
Randal E. Pudelek
Gregory D. Reed
Department of Civil Engineering
The University of Tennessee
This paper summarizes the results of a
study in which the reactivities of 23 fly
ashes were evaluated in a pilot plant
spray dryer/fabric filter sulfur dioxide
removal system. The primary objective
was to determine the ability of each fly
ash (including lignite, subbituminous,
and bituminous eastern and western
ashes) to remove S02 when placed in a
water-based slurry and atomized by a
spinning disk atomizer into a spray dryer
located on a slipstream from a stoker-
fired boiler.
Data are summarized in both tabular
and graphical form including chemical
kinetic data as well as S02 removal
efficiency indicating the enhancement in
efficiency resulting from use of fly ash.
The SO2 removal efficiency ranged from
10 to 50% with only fly ash in the slurry.
Section G—Plenary Session
Fabric Filtration—As It Was,
Has Been, Is Now and Shall Be
Edward R. Frederick
Technical Director
Air Pollution Control Association
Since the first baghouse patent issued
in 1852, commercial filtration technology
h,as progressed significantly with ad-
vances in both collector design and in the
performance capability of filter fiber and
fabric. With the resulting extended and
expanded service of fabric filters, critical
issues have evolved concerning electro-
static involvement. Even though the
natural charges present on gas entrained
particles and on the collecting media
interact to play a major role in essentially
all filtration operations, more intense
interest and study is being devoted to
electrical augmentation as a means for
optimizing these features and, thereby,
all collection parameters. These observa-
tions have also stimulated further interest
in and the production of new types of
electrets, the electrified fibers that retain
charges for extended service even under
adverse conditions.
Although zinc oxide was first suggested
as an absorbent for S02 during the last
century, more economic reagents now
serve with fabric filters to control this
emission contaminant commercially by
dry and wet/dry scrubbing. Further ad-
vances in this technology through the
addition of special catalysts/additives
and/or with special processing aids,
increase SOz removal efficiency and also
control NO, effectively.
Normal use temperature filter fabrics
are being improved and even better,
although more exotic, high-temperature
products are available. Improved process-
ing, finishing and treating practices are in
use to offer special value in extending bag
-------
life, chemical resistance and cleanability.
The major yet unheralded problem
of nodule formation deserves special
research consideration in view of the
check valve effect that these "dingle-
berries" have on the filtration process.
Corrective measures for this condition
and expansion of waste heat/product
recovery and utilization will certainly lead
to further expansion of fabric filtration
technology for S02 as well as particulate
matter control.
F. Venditti. J. Armstrong, and M. Durham are with Denver Research Institute,
Denver, CO 80210
Dale L. Harmon is the EPA Project Officer (see below). '
The complete report, entitled "Fourth Symposium on the Transfer and Utilization
of Particulate Control Technology: Volume I. Fabric Filtration," (Order No. PB
85-161891/AS; Cost: $40.00. Set of three volumes PB 85-161883/AS; Cost:
$95.50, 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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
ft U.S. GOVERNMENT PRINTING OFFICE: 1985-55M16/27050
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