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

-------
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

-------
 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

-------
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

-------
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"

-------
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-

-------
 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

-------

-------
                                                          is
                                                          Is
                                                          a>

                                                          I
  <   »•«
           o
 <*  aez  rv>
 oo  <  «<,
   >»  30
   »!•
   GDM-0
f"rn  o
  "»  a»
  -<
O    J»
O    CJ
**    m
o    z
                                                           N>-" * t-~L"T, V
                                                           o?.-.  &2°5
                                                           °M   ,r3?
                                                           1?  SS  q
                                                           -;!'g'  ^
                                                              CO   !£

                                                                   cr
                                                             •*>

-------