United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711 J
Research and Development
EPA-600/S9-84-025D Mar. 1985
&ER& Project Summary
Fourth Symposium on the
Transfer and Utilization of
Particulate Control Technology:
Volume II. Electrostatic
Precipitation
F. P. Venditti, J. A. Armstrong, and M. D. Durham
Summarized herein is Volume II of
three volumes of proceedings of the
Fourth Symposium on the Transfer and
Utilization of Particulate Control Tech-
nology held in Houston, Texas, October
11-15,1982. Volume II papers discuss
theoretical and applied aspects of elec-
trostatic precipitation.
Volumes I and III are described in two
separate project summaries.
This Project Summary was developed
by EPA'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 in-
formation at back).
Introduction
The papers in these three volumes of
proceedings were presented at the Fourth
Symposium on the Transfer and Utiliza-
tion of Particulate Control Technology in
Houston, Texas, October 11-15, 1982,
sponsored by the Particulate Technology
Branch of the Air and Energy Engineering
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 (ESPs)—were the primary
concern of the symposium. These tech-
nologies were discussed from perspectives
of economics, new technical advance-
ments in science and engineering, fun-
daments, and applications. Several papers
dealt with the interaction of sulfur dioxide
control and particulate control. Additional
topic areas included mechanical collec-
tors, coal characterization, inhalable
particulate matter, novel devices, and
advanced energy applications for particu-
late control.
The symposium was conducted as a
series of parallel sessions, each containing
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 sessions
represented a thread of tech nology. These
parallel threads, extending over the total
period of the symposium, provided a highly
integrated approach to the total subject of
particulate control technology, with
strands of specialized technologies. These
strands of specialized technologies, or
perspectives, provided the basis for the
division of the papers into three volumes,
each volume containing a set of related
session topics so as to provide easy access
to a unified technology area.
Volume II Papers
Volume II, summarized here, isa collec-
tion of papers describing various aspects
-------
of electrostatic precipitation. A section on
advanced ESP technologies contains sev-
eral papers describing laboratory and pilot
plant results of advanced technologies
such a prechargers, wide plate spacing,
and pulsed excitation. The improvements
in ESP performance that can be obtained
with flue gas conditioning using sulfur
trioxide and ammonia are described in a
series of papers. Various aspects of ESP
modeling are also discussed including the
use of modeling for sizing ESPs and the
importance of loss mechanisms in models.
Theoretical aspects are covered in a
section covering positive polarity, particle
charging, dust layer breakdown, back
corona, and the electrohydrodynamic
effects of turbulence. Practical aspects
such as air flow distribution, rapping
strategies, electrode design, high voltage
control systems, operation and mainte-
nance, and industrial applications are also
discussed.
Section A - Industrial
Applications
Modeling of Wet Bottom
Agitator Systems for
Electrostatic Precipitators on
Recovery Boilers
Michael A. Sandell
Robert R. Crynack
Air Pollution Control Division
Wheelabrator-Frye, Inc.
Wet bottom precipitator designs are
becoming more common on black liquor
recovery boiler applications. A black
liquor-filled pan under the precipitator
mixes the collected salt cake as it is
circulated with rotating agitators. Unde-
sirable buildup can result due to improper
mixing and poor flow patterns. In order to
verify that the design of a complex
wet bottom agitator system is adequate,
three dimensional scale modeling should
be employed. The paper presents the
results of several such model studies. The
results discussed include (a) visualization
of flowand mixing patterns, (b) identifica-
tion of poor mixing areas, (c) specification
of location and size of baffles to improve
areas of poor mixing, (d) determination of
agitator speed and direction of rotation,
(e) evaluation of paddle design and orien-
tation, and (f) location of feed and drain
pipes. The theory of modeling, which
considers the temperature and viscosity
of the black liquor and which establishes
the scaling factors and model fluid param-
eters, is also discussed. This modeling
technique provides a valuable tool for
users, consultants, and manufacturers to
minimize on-line problems.
Design and Performance of
Electrostatic Precipitators
Utilizing a New Rigid Discharge
Electrode Design
Gary/?. Gawreluk
Robert L Rump
Research-Cottrell, Inc.
A survey of recent electrostatic precipi-
tator buying practices indicates that rigid
electrodes, as compared to weighted
wires and rigid frames, are becoming
more and more the electrode of choice for
new equipment purchases. This paper
presents some of the reasons behind this
trend and discusses the rigid electrode
design of one manufacturer. Additionally,
the design and performance of three
installations that are utilizing this rigid
electrode are examined.
Development and
Evaluation of a New Precipitator
Emitter Electrode
R. Adams
P. Gelfand
Air Correction Division. UOP, Inc.
This paper reviews the laboratory and
field development and evaluation associ-
ated with the development, of a new rigid
emitter. The paper discusses the experi-
mental procedures and establishes the
comparative criteria for the evaluation of
different electrodes. Laboratory studies
were conducted to measure the current
density patterns formed by various elec-
trode designs. Final laboratory data are
presented comparing three different types
of emitters, two rigid and one wire. The
data result in comparison of emitter
performance on a theoretical basis. Final
field data on a full-scale precipitator are
presented which verify the laboratory
results.
Industrial Applications of Two
Stage Tubular Electrostatic
Precipitators
Harish S. Surati
Michael R. Beltran
Beltran Associates, Inc.
Two stage Tubular precipitators incor-
porate best features of both the single
stage and two stage type designs. Ex-
tremely high collection efficiency in sub-
micron regions makes these precipitators
ideal choices for processes having a very
high concentration of sub-micron organic
mist like Retort Oil Shale or Coal/Wood
gasification. Design parameters, field test
data and operating data from installations
on these processes are discussed in this
paper.
Tubular precipitators have also found
wide acceptance in ferrous and non-
ferrous metallurgical applications involv-
ing sub-micron emissions, most notably
from smelting, sintering, and scarfing
operations. Installations on Electric Arc
and Rotary Hearth Furnace exhausts are
described.
Several installation details from chem-
ical processes like Sulfuric Acid Manu-
facturing, Sulfonic Acid Production,
Ammonia Scrubbing of SO2, etc. are
covered in the paper. Comparisons with
single stage type precipitators are made
wherever applicable.
Section B - Advanced Technology
Pilot Demonstration Two-Stage
ESP Test Results
P. Vann Bush
Duane H. Pontius
Southern Research Institute
Results of the evaluation of the per-
formance of a large pilot scale two-stage
ESP under a range of operating conditions
are presented in this paper. A three
electrode precharger, followed by four
collector sections with a total SCA of 286
ftVkacfm {56 mVmVs) and a gas flow
capacity of 30,000 acfm {850 mVmin),
was tested under two ash resistivity
conditions. Background information on
system operation since start-up in early
1981 as well as results from recent tests
are presented.
Evaluation of Prechargers for
Two-Stage Electrostatic
Precipitators
George Rinard
Donald Rugg
Michael Durham
Denver Research Institute
Two-stage precipitators are being con-
sidered for high resistivity dust collection.
Indications are that the size of a two-
stage precipitator for this application may
be considerably smaller than a conven-
tional wire plate design. ORI is presently
evaluating two-stage designs using a
7.08 mVs (15000 ACFM) pilot plant and
slipstream of the Valmont Power Plant in
Boulder, Colorado. Results of the evalua-
tion of two precharger designs are given.
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.
Initial Experiments with an
Electron Beam Precipitator
Test System
W. C. Finney
R. H. Davis
J. S. Clements
Department of Physics
Florida State University
E, C. Trexler
U.S. Department of Energy
J. S. Halow
Morgantown Energy Technology Center
0. Z. Tokunaga
Japan Atomic Energy Research Institute
As part of the Department of Energy's
Advanced Environmental Control Tech-
nology Program, a laboratory-scale Elec-
tron Beam Precipitator test system (EBP)
has been designed and constructed at the
Florida State University to investigate
particle charging and collection under a
wide variety of experimental conditions.
The system consists of a rectangular,
closed-circuit wind tunnel composed of a
number of interchangeable modules in-
cluding an electron beam (e-beam) pre-
charger followed by a collecting section.
A model aerosol enters the e-beam
precharger, is charged in an ionization
zone, and then passes downstream to the
collector. At a gas velocity of 10 ft/sec
through the precharger the velocity in the
collector is 2.5 ft/sec, giving the collector
an SCA of 200.
Experimental results are presented of a
preliminary investigation of e-beam pre-
charger ionization for a wide range of
electron beam currents and precharger
electric fields. Experiments planned with
the EBP include the determination of the
charging and collection efficiency of the
system using resuspended particles with
properties similar to high resistivity fly
ash.
Experiments with Wide Ducts in
Electrostatic Precipitators
Ekkehard Weber
Helmut Wiggers
University of Essen
The repeatedly observed enhancement
of the effective migration velocity with
increasing duct width holds out the
prospect of less expensive electrostatic
precipitators. Vagueness still exists re-
garding the optimum of the width and the
influencing factors on it. Based on labor-
atory experiments indicating almost a
proportionality between migration veloc-
ity and duct width up to 715 mm, a pilot
precipitator with a maximum flow rate of
36,000 mVh was constructed. Parallel to
large scale conventional electrostatic
precipitators for a coal-fired power station
and the room dedustion of a sinter plant
duct width up to 1,000 mm were tested.
Besides a far reaching conformity with
the laboratory results an optimum width
was ascertained, which is influenced for
instance by the gas velocity. Moreover,
with a theoretical precipitator model it
succeeded to explain the corresponding
influences on the migration velocity.
A Reconciliation: Wide Versus
Narrow Spaced Collecting
Plates for Precipitators
Dennis G. Puttick
Peabody Sturtevant, Ltd.
Misaka of Hitachi, amongst others, has
presented evidence for the improvement
of electrostatic precipitator performance,
using much wider gas passage spacing
than normal (typically 20 in.). Such de-
signs are now in general use.
This appeared to be directly contrary to
the experience of Peabody Sturtevant
who, on very large utility ESP plants
treating highly resistive particulates, pro-
duce remarkable efficiencies with nar-
rower spacing than normal (typically 8
in.-9 in.) using a design first developed
during the mid-1960's.
In developing his reconciliation, the
author uses observations of the actual
internal construction of different designs
of precipitators and the effect that in-
creasing variance from perfect electrode
geometry has upon total power input and
field intensity at various plate spacings.
This return to basic precipitation elec-
trostatic theory demonstrates not only
that Peabody Sturtevant is right to pursue
its narrow spacing design but other
companies, with their own particular
standard of construction, may be equally
right in developing wider spacer tech-
niques.
Pulse Corona as Ion Source and
Its Behaviors in Monopolar
Current Emission
Senichi Masuda
Yoshiaki Shishikui
Department of Electrical Engineering
University of Tokyo
The pulse voltage applied to a discharge
electrode produces a weakly ionized
plasma with about 5 x 109 ions/cm3 in ion
concentration in a very short time of
about 10-100 nanoseconds. The monopolar
ions are extracted by an externally applied
dc field towards the charging area from
this plasma, and the current pulse lasts
for a substantially longer time of about
1 -3 milli-seconds. This is due to a long life
time of the plasma which disappears by
recombination and charge separation.
The expansion of the monopolar ion cloud
during its migration across the charging
area also contributes to the increase in
the duration time of the current pulse
measured at the counter electrode. The
theory explaining the wave form of the
Section C - Fundamentals
A New Correction Method of
Migration Velocity in Deutsch
Efficiency Equation for
Conversion of Electrostatic
Precipitator Sizing from a
Pilot-Scale to a Full-Scale
Fumio Isahaya
Hitachi Plant Engineering &
Construction Co., Ltd.
Research Laboratory
In order to confirm the validity of the
Deutsch efficiency equation, the deposi-
tion rate distribution of the collecting
electrode wall of a small size cylindrical
type precipitator having a diameter of 30
mm and length of 400 mm was measured
by utilizing a radioactive aerosol tracer
technique.
The Thorium B solid particles as testing
radioactive aerosols having a relatively
uniform particle size of approximately 0.1
microns were used. As a result the
concept of the Deutsch efficiency equa-
tion was held tolerably good in the range
of the gas velocity of 0.35-1.0 m/s, S.C.A.
of 35-106 s/m and corona current density
of 2.5-13 //A/cm.
Accordingly, in order to put the Deutsch
migration velocity to practical use in
industry and to predict the required sizing
and S.C.A. for a full-scale precipitator on
the basis of the test results in a pilot-scale
one, such a new correction formula for
the migration velocity in the Deutsch
efficiency equation which can be cor-
reeled as a function of the aspect ratio of
collecting electrode, spacing of electrode,
treating gas velocity, S.C.A., corona cur-
rent density, particle size distribution, a
wide spacing effect and re-entrainment
effect, was proposed. Furthermore, ac-
cording to this formula the performance
characteristics curves of collection effici-
-------
ency versus S.C.A. for a pilot-scale and
full-scale precipitator were given in com-
parison with both in the range of industrial
use such as a coal-fired boiler plant.
Distortion of Pulse Voltage
Wave Form on Corona Wires
Due to Corona Discharge
Senichi Masuda
Hajime Nakatani
Department of Electrical Engineering
University of Tokyo
A very short pulse voltage travelling on
a corona transmission line producing
streamer coronas is subjected to a time-
dependent distortion of its wave form
owing to energy consumption by corona.
There are two different streamers in the
case of a parallel-wire transmission line.
The first streamer is launched from the
negative wire at the leading part of the
pulse crest voltage, while the second
streamer is emitted from the positive wire
at its rear part. The first (negative)
streamer produces a small distortion in
the leading part, whereas the second
(positive) streamer causes a great lower-
ing of voltage wave form in the rear part.
The time-dependent equivalent surge
impedance of the line also shows a
concurrent lowering owing to these
streamer activities.
Electrostatic Precipitator
Analysis and Synthesis
Ta-Kuan Chiang
Thomas W. Lugar
General Electric Environmental
Services, Inc.
An analytic model using the modified
Deutsch approach has been developed to
describe the overall performance of an
electrostatic precipitator comprising two
different configurations or energization
methods in tandem. Measurements of
the overall collection efficiency and the
collection efficiency of either configura-
tion provide sufficient information to
isolate the performance contributed by
the other. Field data, obtained with pulse
energization at the outlet half of the plate
area and conventional dc energization at
the inlet half of a full-scale utility precip-
itator, are presented to illustrate the
method.
Computer Model Use for
Precipitator Sizing
G. W. Driggers
A. A. Arstikaitis
L A. Hawkins
Environmental Systems Division
Combustion Engineering, Inc.
The design of utility industry precipita-
tors is typically based on a historical data
base of performance and operating char-
acteristics gathered from full scale units.
Development over the last ten years of
first principal analytical models for per-
formance prediction offers new tools for
the precipitator designer. The EPA/SORI
model has been selected by the Combus-
tion Engineering Environmental Systems
Division for refinement to the C-E precipi-
tator design. The current historical data
sizing procedure and performance predic-
tion approach is described followed by a
discussion of the EPA/SORI model and
refinements required to make it fit theC-E
design.
Improvements in the
EPA/SRI ESP Performance
Model
M. G. Faulkner
Southern Research Institute
ft. B. Mosley
J. R. McDonald
Crestmont Associates, Inc.
L. E. Sparks
Air and Energy Engineering Research
Laboratory
Environmental Protection Agency
Revision 3 of the ESP performance
model developed for the EPA at Southern
Research Institute has been completed.
This version features a reduction in
required computer time of about a factor
of 10 over revision 1 for the rigorous
calculation of collection efficiency. In
addition, several new procedures have
been added to the model. One of these
allows the calculation of plume opacity.
Another calculates the effects of rapping
reentrainment through a dynamic process
which examines the results of each rap as
it occurs. These changes and others will
be described.
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.
Numerical Simulation of the
Effects of Velocity
Fluctuations on Electrostatic
Precipitator Performance
Eric A. Samuel
General Electric Environmental
Services, Inc.
A numerical scheme for including the
effects of velocity fluctuations in plate-
wire electrostatic precipitators arising
from turbulent diffusion, within the
framework of the already developed tra-
jectory method for precipitator perform'
ance evaluation, is described. The pre-
dictions of the scheme are shown to be in
agreement with classical solutions based
on Fickian diffusion for some simple
configurations.
Corona-Induced Turbulence
M. Mitchner
G. L Leonard
S. A. Self
High Temperature Gasdynamics
Laboratory, Mechanical Engineering
Department, Stanford University
The results of previous experiments
with a bench-scale precipitator (5 cm
plate-to-plate spacing) have shown that
moderate levels of turbulence can be
maintained in the presence of a corona
discharge, and that in accord with theory,
significant gains in precipitator efficiency
are possible. In this paper hot-wire
anemometer measurements in a labora-
tory-scale precipitator (25 cm plate-to-
plate spacing) are presented that support
the previous results and suggest that
similar improved performance is possible
in larger-scale commercial precipitators.
The measurements also provide a further
explanation for the reduced migration
velocity previously reported by other
workers at low gas velocities.
Velocity and Turbulence
Fields in Negative Corona
Wire-Plate Precipitator
H. P. Thomsen
P. S. Larsen
E. M. Christensen
J. V. Christiansen
Department of Fluid Mechanics
Technical University of Denmark
Back-scatter laser Doppler anemometr>
has been used to obtain distributions o
mean and rms values of particle velocity
in horizontal planes perpendicular tc
electrodes in a 0.3 m wide by 0.6 m higf
wire-plate electrostatic precipitator fo
four types of electrodes and a meai
velocity of 1 m/s. Particle motion reveal:
complex three-dimensional flow pattern
with rolls of axial vorticity which are mos
regular for barbed wire electrodes witl
axial needles. The turbulence level i
shown to depend on current density an
mean velocity and to disappear when th
inverse electrical Froude number is belov
-------
about 0.2. However, rolls persist. Results
are discussed in terms of the turbulent
kinetic energy production.
The Effect of Turbulence on
Electrostatic Precipitator
Performance
D. E. Stock
Department of Mechanical Engineering
Washington State University
The turbulent character of the gas flow
found in an electrostatic precipitator (ESP)
affects the motion of the particles (dust)
and, therefore, the unit's performance
through two mechanisms. The mean
velocity profile found in an ESP conveys
the particles both longitudinally through
the precipitator and in the transverse
direction. Particle motion is also strongly
affected by turbulent diffusion. The
magnitude of the turbulent diffusion is
expressed through a particle turbulent
diff usivity which depends on the turbulent
character of the gas, particle size, and the
crossing trajectories effect.
A particle diffusion equation is devel-
oped and the coupling with the gas flow
field and electric field is discussed. Finally,
techniques for estimating the particle
diffusivity are presented.
Factors Leading to Electrical
Breakdown of Resistive Dust
Layers and Sustained
Back Corona
Phil A. Lawless
Research Triangle Institute
Leslie E. Sparks
Air and Energy Engineering Research
Laboratory
Environmental Protection Agency
Recent theoretical work modeling the
resistive dust layer has shown consider-
able enhancement of the electric field at
the points of contact between particles.
These theories are examined with regard
to evaluating the conditions leading to
electrical breakdown and sustained back
corona discharge via the Townsend ava-
lanche mechanism. Among other factors,
the particle size distribution is shown to
have a significant effect on the internal
field in the layer. The resulting breakdown
characteristics of the resistive layer can
be used to obtain the proper operating
current density for the precipitator and to
evaluate the effects on collection of
excursions into the back corona regime.
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.
Electrical Breakdown of
Particulate Layers
G. B. Moslehi
S. A. Self
High Temperature Gasdynamics
Laboratory, Mechanical Engineering
Department. Stanford University
A theoretical analysis of electrical
breakdown of a current-carrying particu-
late layer modeled as a regular array of
equi-sized resistive spheres having com-
bined surface and volume conduction is
presented. This analytical treatment is
based on an extension of a theory of
electromechanics of the layer and predicts
the onset of electrical breakdown of the
layer in the form of intermittent micro-
sparks in the gap between the contacting
particles when the electric field at the
contact or in the surrounding gap exceeds
the threshold breakdown value. The
occurrence of breakdown is due to the
existence of a very strong electric field in
and around the contact region as a result
of current constriction at the contact
area. Two possibilities of breakdown are
examined: (i) breakdown in the gap where
the gap height, d, is larger than the gas
mean free path, ^; and (ii) vacuum break-
down at the contact where d < A.
The electrical behavior of the layer after
breakdown is also analyzed in terms of a
simplified equivalent lumped circuit using
methods of conventional transient circuit
theory. In this analysis the layer is
modeled as a number of capacitive spark
gaps in series, separated by high resis-
tances. In effect, the discharge propagates
through the layer as a cascade of micro-
sparks, which discharges the layer locally.
The theory predicts increases of sparking
frequency and average current as the
applied average field EA, exceeds the
threshold average field for the onset of
breakdown EAB.
Experiments with glass beads demon-
strate the existence of intermittent
microsparks after the onset of breakdown,
whose frequency of occurrence increases
with increasing EA.
Electromechanics of
P articulate Layers
G. B. Moslehi
S. A. Self
High Temperature Gasdynamics
Laboratory, Mechanical Engineering
Department, Stanford University
In previously reported work, a compre-
hensive theory of the electromechanics
of a paniculate layer was developed,
treating it as a regular cubic array of equi-
sized resistive spheres, allowing for both
volume and surface conduction, and
taking account of self-compression of the
layer. The theory gives expressions for
various quantities of interest including
the contact angle G0, the maximum
electric field Emax, the average compres-
sive stress PE and the apparent resistivity
pA, all in terms of the average layer
current density JA (or average field EA =
pAJA) and the system parameters.
In the present paper this theory is
extended in two ways. First, explicit
expressions for the quantities 00, Emu, PE
and PA are given in the form of power laws
(in EA) in which the coefficients and
exponents depend on the system param-
eters, in particular the resistivity ratio o =
sa/p, where a is the particle radius and s
and p are, respectively, the (intrinsic)
surface and volume (material) resistivities
of the particles. These expressions should
be operationally useful for interpreting
experimental data. Second, the theory
has been extended to include all of the six
classical modes of compaction for equi-
sized spheres. The results are qualita-
tively similar to those for the cubic array
and are related to them by a set of
multiplicative constants which are of
order unity.
Measurements of the resistivity char-
acteristics PA (EA) of layers of glass beads
confirm the theoretical results both quali-
tatively and quantitatively.
Lateral Propagation of Back
Corona in Twin-Electrode
Type Precipitators
Senichi Masuda
Toshifumi Itagaki
Department of Electrical Engineering
University of Tokyo
The lateral propagation of back corona,
discovered to occur in a tri-electrode
corona system, also occurs in a conven-
tional electrostatic precipitator of the
twin-electrode system under certain
circumstances. The primary factor in
initiating this phenomenon is the mutual
excitation of the wire corona discharge
and back corona. At high resistivity of
dust deposit and with small discharge
wire diameter, this mutual excitation
becomes dominant and the lateral propa-
gation occurs from a single back corona
on a plate appearing at a local spot. The dc
base voltage in a pulse charging system
must be selected in careful consideration
of this phenomenon. The detailed condi-
tions of its initiation and extinction in air
-------
at NTP are presented in relation to various
modes of corona discharge.
First Measurements of Aerosol
Particle Charging by
Free Electrons
James L DuBard
M. G. Faulkner
Southern Research Institute
Leslie E. Sparks
Air and Energy Engineering Research
Laboratory
Environmental Protection Agency
The charging of fine aerosol particles
by free electrons has been isolated from
negative ionic charging and measured for
the first time. The charge and size of
individual particles were measured in a
Millikan cell, with charging electric field
from 0.82 to 8.2 kV/cm. In the particle
size range 0.5 to 3.5 tm\ diameter, the
particle charge values are much larger,
and increase faster with particle size,
than those predicted and observed for
negative ionic charging. The particle
charge values show only slight depen-
dence on the charging electric field.
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 D - Operation &
Maintenance
Gas Flow Distribution
Model Testing
D. R. Cook
J. M. Ebrey
D. Novogoratz
Lodge-Cottrell/Dresser
Uniform gas distribution is critical to
the operational efficiency of both electro-
static precipitators and structural bag-
houses.
The relationship of collection efficiency
to gas distribution criteria is discussed.
The Deutsch-Anderson equation model-
led into a computer gas distribution
program indicates the effects of gas
distribution deviations on efficiency per-
formance
Unique characteristics of the Lodge-
Cottrell approach to gas flow distribution,
pressure loss, and dust fallout testing are
discussed, as are the proprietary distribu-
tion devices used. Test objectives and
methods used are described.
These preceding discussions identify
the need for gas flow correction tech-
nology and its role in fulfilling today's
technological requirements.
The need for gas flow correction in
structural baghouses is discussed, and
some results presented.
Finally, model vs. field test results will
be compared for both the electrostatic
precipitator and the structural baghouse.
Acknowledgements—The authors wish
to express their appreciation to Dresser
Industries, Inc., for granting permission
to publish this information and also our
thanks to our colleagues at Lodge-Cottrell
U.K. and U.S. for their assistance.
Air Flow Model Studies
L H. Bradley
United Engineers and Constructors
This paper establishes the need for
strict control of air flow model studies and
the higher acceptance standards for test
results which are required to obtain the
collection efficiencies needed to satisfy
regulatory requirements. The importance
of flow patterns and minimum pressure
losses is reviewed and discussed includ-
ing the importance of dimensionless
ratios such as Reynolds N u mber, modified
Fraude Number, and the momentum ratio.
The requirements for design, scale, model
limits, fabrications and test procedures as
established by I.G.C.I. Standards and
additional requirements are shown and
discussed. Data collection methods in-
cluding limitations and evaluation me-
thods for test data are presented and
discussed. Examples from recent air flow
model studies are presented and reviewed
to illustrate items which should be con-
sidered. Based on these results, a com-
parison of deviation from design collection
efficiency as a function of root mean
square deviation is shown.
Collecting Electrode Rapping
Designed for High Efficiency
Electric Utility Boiler
Electrostatic Precipitators
A. Russell-Jones
A. P. Bay I is
Lodge-Cottrell Limited
The influence of collecting electrode
rapping on the efficiency of an electro-
static precipitator is examined. Particular
emphasis is placed upon the limitations
caused by dust re-entrainment.
The way in which the effectiveness of
the dislodgement blow is often specified
in terms of measured shock acceleration
on the collecting electrode, is shown to be
unsatisfactory in view of plate and accel-
erometer response variations.
The means~by which re-entrainment
can be minimized is discussed and a
theory which can be used to explain
observed performance is advanced.
Long term performance of an Electric
Utility gas cleaning plant designed to
achieve the best compromise of rapping
requirements is reviewed. Examples of
500 MW power plant precipitators, and
larger, operating satisfactorily over per-
iods up to 17 years after commissioning,
are cited.
Electrostatic Precipitator and
Fabric Filter Operating and
Maintenance Experience
P. Goldbrunner
Burns and Roe
W. Piulle
Electric Power Research Institute
This paper summarizes the "Reliability
Assessment of Paniculate Control Sys-
tems" (RP 1401) performed by Burns and
Roe, Inc., for the Electric Power Research
Institute. Its purpose was to determine
the performance and availability of elec-
trostatic precipitators and fabric filters
used to control flue gas particulate emis-
sions from coal fired electric utility power
plants. Representative precipitator and
fabric filter installations, with associated
ash handling systems, were studied.
Operation and maintenance histories
were compared. The results are presented
in graphic form.
Section E - Conditioning
Economical Fly Ash
Collection by Flue Gas
Conditioning
E. L. Coe, Jr.
Wahlco, Inc.
This paper discusses the application c
sulfur trioxide flue gas conditioning to th
collection of high resistivity fly ash i
coal-fired power plants. A large portion <
the world's coals produce ash falling i
this category. Peformance figures for
600-MW U.S. plant having this type i
equipment in operation are given. Th
plant had conditioning installed as a pa
of the original plant equipment. A con
parison of emissions to those of ba
houses is included, along with data <
maintenance and operating costs.
6
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Experiences at Detroit Edison
Company with Declining
Performance of Sulfur Tr/oxide
Flue Gas Conditioning
Equipment
L A. Kasik
W. A. Rugenstein
J. L. Gibbs
Detroit Edison Co.
The generation of sulfur trioxide in
some of our Company's sulfur-burning
flue gas conditioning systems has been
found to decrease significantly over a
period of a few years. The deteriorating
performance went undetected because
SOz to 80s conversion efficiency was
measured with what later proved to be an
inadequate procedure. A fall-off in S03
output can seriously affect precipitator
collection efficiency resulting in opacity
and/or mass emission excesses. The
vanadium pentoxide catalyst bed was
suspected to be at fault because in some
systems very little heat was being gener-
ated in the bed. A new test procedure, a
modified EPA Reference Method 8, was
used to overcome the inadequacies of the
old procedure. Using the new procedure,
conversion efficiency on one particular
boiler was found to have dropped from
about 80 percent to about 30 percent
after five years of service.
ESP Conditioning with
Ammonia at the Monroe Power
Plant of Detroit Edison Company
E. B. Dismukes
J. P. Gooch
G. H. Merchant, Jr.
Southern Research Institute
An investigation of ammonia condition-
ing was conducted recently at Monroe
Unit 1, a 720-MW unit burning coal with
about 2% sulfur and collecting fly ash in
cold-side ESPs around 270°F (132°C).
Experience has shown that 8 ppm of
ammonia substantially lowers stack
opacity. Tests confirmed the 99.72 to
99.83% on an overall mass basis and
from 99.20 to 99.68% for particle sizes
below 6 urn. Particle-size data and ESP
electrical data indicate that conditioning
mechanisms include space-charge en-
hancement of the electric field by means
of a fume of ammonium sulfate or bisul-
fate. The resistivity of the ash without
conditioning(± 1 x 1010 ohm-cm) was not
altered by ammonia addition. Data on
outlet particle sizes show evidence of
reduced rapping reentrainment through
increased ash cohesiveness.
Fly Ash Chemistry Indices for
Resistivity and Effects on
Electrostatic Precipitator
Design and Performance
Herbert J. Hall
J. J. Hall Associates, Inc.
Field data on coal-ash properties and in
situ fly ash resistivity measurements for
24 cases of cold side precipitators are
correlated with various ash chemistry
indices for resistivity prediction. Coals
studied, principally low sulfur, are from
eastern and western U.S.A., western
Canada, and several other countries;
boiler sizes are 50-800 MW. Most uni-
versally applicable general indices for low
S coals seem to be those based upon
sodium content, per se, and on a silicate
type index long used by the author. Under
special conditions, other indices may also
be useful. Ash chemistry indices proposed
by investigators such as Selle, Dunston,
Matts, Soviet ESP designers, Bickelhaupt,
Hall, and others are reviewed. Compari-
sons of useful indices with resistivity data
calculated from a computer program
based on Bickelhaupt's work are illus-
trated for an additional 16 cases which
are also compared with the in situ field
data. Some quantitative aspects of coal-
ash properties as affecting precipitator
design and performance are discussed.
Section F - Control Systems
A New Energization Method for
Electrostatic Precipitators
Mitsubishi Intermittent
Energization System
Takashi Ando
Naoji Tachibana
Mitsubishi Heavy Industries, Ltd.
Kobe Shipyard & Engine Works
Dr. Yoichi Matsumoto
Mitsubishi Heavy Industries, Ltd.
Takasago Technical Institute
Mitsubishi Heavy Industries, Ltd.,
developed a new energization system for
ESPs and has proved its favorable per-
formance on many operating full-scale
ESPs with high resistivity ash. This paper
is to introduce the new equipment named
Mitsubishi Intermittent Energization
System (abbreviated to MIE) which sup-
plies high voltage to ESP intermittently
with adjustable supplying and suppress-
ing times by means of power control
thyristors with electronic circuit. MIE
mitigates the degradation of collecting
efficiency due to back corona and its
effect can be estimated by voltage-current
characteristics at gas load operation. The
best improvement is expected for the
case of low voltage and large current. A
long term actual operation on an iron ore
sintering machine has shown that the
modified migration velocity wk of 100% at
conventional energization is improved to
147% by MIE and at the same time the
power consumption of 100% is reduced
to 20%.
The advantages of MIE can be summar-
ized as follows:
(1) improvement in collecting efficiency
for high resistivity ash;
(2) energy saving; and
(3) small additional cost.
This paper includes explanation of equip-
ment, result of laboratory test and
measurement of full-scale ESPs.
Some Measured
Characteristics of an
Electrostatic Precipitator
Obtained Using a
Microcomputer Controller
M. J. Duffy
T. S. Ng
Z. Herceg
K. J. McLean
University of Wollongong
This paper presents a new microcom-
puter control system for electrostatic
precipitators. The system, currently in its
second stage of development is capable
of actively controlling, monitoring and
recording the characteristics of an elec-
trostatic precipitator.
The results of tests carried out on the
precipitator along with the output of a
dust monitor mounted on the precipitator
output are also presented in an attempt to
determine the optimum operating condi-
tions.
Electrostatic Precipitator
Energization and
Control Systems
K. M. Bradburn
K. Darby
Lodge-Cottrell Dresser
This paper reviews the development of
systems for the energization and control
of electrostatic precipitators, ranging from
heavy duty thyristors used to control the
input to the T/R set to the use of micro-
processor technology which gives the
facility for a precipitator total energy
management system (TEMS). The impact
of these changes is described first on the
T/R set, then on the automatic voltage
control system to maximize precipitator
efficiency.
U. S. GOVERNMENT PRINTING OFFICE-.! 985/559 111/10802
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Reference is made to the electrical
demands of a precipitator, under varying
operating conditions, to justify the advan-
tages of the TEMS concept.
The system comprises a local control
and power unit for each T/R set, a super-
visory control unit and a control room
monitor which allow visual (CRT) display
and print out of operating data and
parameters remote from the precipitator.
In addition to improved automatic vol-
tage control, TEMS offers the facility for
integrating additional operations and
parameters such as stack opacity, rap-
ping, hopper heating, hopper ash level
alarm, precipitator startup and shutdown.
This results in complete system control
and improved operation with lower power
consumption and operating costs.
Using a telephone modem, precipitator
engineers remote from the plant can
accurately and instantaneously monitor
and adjust precipitator operation and give
technical support to plant engineers for
prompt correction of any operating prob-
lems.
Applying Modular
Microcomputer Control
Elements in a Precipitator
Control System
Ira M. Wexler
Environmental Elements Corporation
The declining cost of microcomputers
allows the control designer to implement
microcomputers into individual compo-
nents of a precipitator control system.
This distributed processing technique
allows the integration of the individual
controls with a master computer, and
also provides the controls with intelli-
gence required to operate independently,
should the need arise. The individual
microcomputer elements used to control
transformer/rectifers, rapping systems
and alarm systems are described. Tech-
niques used to integrate these elements
with a master precipitator controller
providing data acquisition, energy man-
agement, and control optimization are
also defined. In addition, a fail-safe
operating philosophy which takes advan-
tage of the intelligence designed into the
individual controls is presented. Finally,
the impact of this technology on the end
user is discussed, using an actual instal-
lation at a utility boiler.
Section G - Plenary Session
The Current Status, Future
Directions, and Economic
Conditions in the
Applications of ESP's
Sabert Oglesby
Southern Research Institute
The subjects being most widely dis-
cussed for advancements in electrostatic
precipitators are conditioning to modify
dust resistivity, pulsed power supplies,
precharging, wide-plate spacing, micro-
computer controls, alternative rapping
schedules, and different electrode geom-
etries. There are some relatively new
concepts in conditioning, such as addition
of sodium compounds to coal to reduce
resistivity of fly ash for hot-side precipita-
tors, andthe use of ammonia compounds
to achieve better performance in some
precipitators by reducing both resistivity
and reentrainment or increasing the
collection electric field by space charge
enhancement.
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 Paniculate Control Technology: Volume II. Electrostatic Precipitation, "(Order
No. PB 85-161 909/AS; Cost: $40.00, Set of three volumes PB 85-161
883/AS; Cost: $95.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
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, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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U S ENVIR PROTECTION AGENCY
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