United States	Industrial Environmental Research
Environmental Protection Laboratory
Agency	Research Triangle Park NC 27711
Research and Development
Electrostatic
Precipitator
Technology
Assessment:
Visits in Japan,
November 1977
Interagency
Energy/Environment
R&D Program Report

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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1.	Environmental Health Effects Research
2.	Environmental Protection Technology
3.	Ecological Research
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6.	Scientific and Technical Assessment Reports (STAR)
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This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
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health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
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essary environmental data and control technology. Investigations include analy-
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22t61

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0% iniZui
EPA-600/7-78-110
June 1978
Electrostatic Precipitator
Technology Assessment:
Visits in Japan, November 1977
by
Grady B. Nichols
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
Contract No. 68-02-2610
W.A. 5
Program Element No. EHE624
EPA Project Officer: James H. Abbott
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460

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ABSTRACT
This report describes the results of a particulate control
technology assessment visit to Japan by a team of United States
Investigators. The visit included discussions with personnel
from universities, industries and major installations involved
with particulate control. Significant research activities were
noted in both the academic and industrial sectors related to
particulate control and measurements.
The report summarizes these results of the individual dis-
cussions, observations during these tours, and discussions of
technical papers. Many valuable technical papers were supplied
to the U.S. Team. These papers are reproduced in the Appendix
of this report, EPA-600/7-78-110a.
ii

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EXECUTIVE SUMMARY
This report describes the results of visits and consulta-
tions with research facilities in universities and industrial
installations as well as inspection trips to operating plants.
The visit was planned with the assistance of Dr. Jumpei Ando of
Chuo University in Tokyo and Mr. Kiyoshi Suito of Japan Manage-
ment Association.
The visit with Professor Senichi Masuda of Tokyo University
provided information about their research activities into the
fundamental factors that cause the development of the disruptive
condition termed "back corona" that is related to current flow
through a high resistivity dust layer in operating electrostatic
precipitators.
We also discussed their research into the use of pulse ener-
gization with a three-electrode system used in conjunction with
a high electric field-low current density collector. This com-
bination of technology leads to reasonably effective collection
of high resistivity particulate.
Another interesting area of research at Tokyo University
involves studies of the influence of "electric wind" related to
the directed motion of ions under the influence of the electric
field as well as studies of enhanced scrubbing of gases when the
ionic wind related turbulences and electrical activity are
present. There is currently some disagreement between researchers
as to the influence of electric wind in electrostatic precipita-
tion. The general consensus of United States, Russian, and
European researchers is that the effect of electric wind is
negligible for electrical current densities normally encountered
in industrial applications.
Ill

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Several research groups in Japan are involved in research to
determine the optimum corona to collection electrode spacing in
electrostatic precipitators. In general, wider plate spacings
provide a greater collection efficiency per area of collection
electrode for low mass loading situations. Increases in plate
spacings, coupled with higher operating voltages lead to in-
creased collection rates so long as the average current density
can be maintained in the control device. These wide plate
spacings promise two significant advantages, so long as the col-
lection efficiency can be maintained. First, the cost of a given
installation will be reduced since smaller quantities of steel
will be required and, second, the weight of the control device
will be less which will result in a reduced load on the structure
for roof mounted installations.
An area of research that is related to particulate control
involves measurements of particulate characteristics. Professor
Yoshida of the Osaka University has an extensive research program
in this area. This group has developed an instrument—an ultra-
microscope—that is useful for studying the behavior of particles
suspended in a gas stream. The device consists of a microscope
coupled to a television display system that is used for viewing
particles at a given distance inside a gas stream. This instru-
ment is used to study several aspects of particulate behavior:
growth of particle by condensation, stability of droplets in a
cloud or fog, Brownian diffusion and coagulation, and particle
size analysis.
The Hitachi group has developed an optical particle counting
system that includes a gas dilution system that is useful for
determining particle size distribution for a range of particle
sizes up to about 100 ym diameter. The dilution system is
stated to yield a constant dilution for all particle sizes up to
this 100 ym range.
Some studies of S0X and N0X removal in electrically active
regions are reported. In one case an electron beam (1-2 Mev
electrons) is directed into the gas stream while in another a
high current density corona system provides the ozone necessary
to enhance the oxidation of the gases to reactive states.
In general, the research activities in Japan are on a par
with the United States, Europe and the Soviet Union. In some
instances, particularly pulse energization, electrode spacing
and, perhaps, fundamental studies of back corona, they are ahead
of others. The research efforts should be monitored and infor-
mation exchanged on a routine basis for the mutual benefit of
both the United States and Japan.
iv

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CONTENTS
Abstract 				ii
Executive Summary		iii
1.	Summary 				1
2.	Introduction 			. .	3
3.	Purpose 		4
4.	Assessment Discussions 				6
5.	Literature Review 								23
6.	Technology Assessment 		36
v

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SECTION I
SUMMARY
This report includes the results of discussions and techni-
cal publications from a variety of research and industrial con-
cerns in Japan that are related to particulate control. The
visits reported are with the University of Tokyo relative to
research into the electrostatic collection of particulate. The
significant work with back corona formation and pulse energiza-
tion is reviewed. The visit to Ishikawajima-Harima Heavy
Industries provided information about a commercial application
of a specialized application of the pulsed energization technique
from Tokyo University.
The Hitachi discussions provided information about some
industrial research with high electric field-low current collec-
tors, wider than normal plate spacings and optical particle
sizing instrument development.
The Sumitomo group is a licensee of the U.S. company -
Joy-Western. They also conduct research into variations in plate
spacings. They described the use of pilot scale electrostatic
precipitators in the sizing of new installations.
The visit to Nippon Steel-Kimitsu Works provided an oppor-
tunity to observe the pollution control techniques in one of the
significant Japanese industries. One of the wide plate spacing
electrostatic precipitators was operating successfully at this
site.
The Shinwa Trading Company enjoys a monopoly in the particu-
late control from coke ovens, ferrosilicate arc furnaces and
fugitive emissions from the iron and steel works in Japan. They
are a licensee of American Air Filter. They have developed a
traveling collection system for use in controlling the emissions
from coke oven pushings.
The Isogo Power Station is equipped with Lodge-Cottrell and
Sumitomo electrostatic precipitators. An S03 injection system
is provided for resistivity modification. This station also has
Chemico slurry limestone scrubbers for S0X control.
The visit with Kyoto University provided an opportunity to
discuss some aspects of fabric filter particulate control research.
Papers covering a wide range of topics were provided.
1

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The Osaka University research group has developed an instru-
ment for directly viewing the behavior of particles suspended in
a gas. Many experiments were discussed that were very pertinent
to particulate studies. The instrument is termed an ultramicro-
scope.
The Mitsubishi Research Laboratories gave the research team
an opportunity to closely evalute a significant industrial
research laboratory. This laboratory is equipped with pilot-scale
electrostatic precipitators and a wide variety of related instru-
ments. They are a licensee of Lurgi in Germany.
The results of these discussions and studies led the U.S.
Team to the conclusion that the level of electrostatic precipi-
tator technology in Japan was on a par with and in some instances
superior to research activities in the United States, Europe and
the Soviet Union. The two areas where the Japanese technology
was deemed to be superior was in the area of pulse energization
for electrostatic precipitators and in the fundamental studies
of back coronas.
2

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SECTION II
INTRODUCTION
A research team representing the United States Environmental
Protection Agency visited a number of academic and industrial
research facilities in Japan to assess the level of electrostatic
precipitator technology in Japan. These information transfer
meetings were arranged through the Japan Management Association
working in conjunction with Professor Jumpei Ando of Chuo Uni-
versity in Japan. Japan Management Association provided
interpreters and other valuable assistance during the period of
this visit. Mr. Kiyoshi Suito of J.M.A. was responsible for this
service.
The visits to each installation consisted of discussions
between the U.S. and Japanese members; tours and demonstrations
in the research and industrial facilities; and an exchange of
information between the participants.
The research team consisted of Mr. James H. Abbott, Chief,
Particulate Technology Branch, Industrial Environmental Research
Laboratory, United States Environmental Protection Agency,
Research Triangle Park, NC; Dr. Leslie E. Sparks, Chemical
Engineer, Particulate Technology Branch, Industrial Environmental
Research Laboratory, United States Environmental Protection
Agency, Research Triangle Park, NC; and Mr. Grady B. Nichols,
Associate Director, Engineering and Applied Sciences, Southern
Research Institute, Birmingham, Alabama.
3

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SECTION III
PURPOSE
The principal purpose of this visit was to assess the state
of technology of electrostatic precipitators, both from a
research and applications point of view. In addition, the state
of technology of alternative particulate control devices was
reviewed when appropriate.
Considerable research has been conducted on particulate con-
trol devices in Japan. Some of the work has been reported in
international journals, while much was only available in Japan
proper. In many cases, discussions of techniques and alternative
interpretations are important. In addition, data presented in
international journals are at least one year old. Therefore,
personal contacts with an interchange of ideas are often required.
These discussions aided immeasurably in assessing the state of
particulate control technology in Japan.
In each visit the leader of the U.S. Team opened the meeting
by reviewing the purpose of the visit. The primary purpose was
to assess the state of technology for electrostatic precipitators
in Japan. The significance of the meaningful research and in-
dustrial applications of electrostatic precipitator technology
and how this technology could be used to advantage by the U.S.
was stressed.
The following technical publications from the U.S. Environ-
mental Protection Agency were provided as exchange information to
the Japanese research team:
-	Impact of Switching to Low Sulfur Coal on Particulate
Emissions
-	Control of Fine Particulate Emissions - E.P.A. Program
Description
-	Hand Calculator Program Descriptions - HP25 and HP65
-	Electrostatic Capture of Fine Particles in Fiber Beds
-	High Temperature - High Pressure Particulate Control
Requirements
4

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-	Fine Particle Charging Development
-	Venturi Scrubber Performance Model
-	A Mathematical Model of E.S.P. Performance
-	Proceedings - Particulate Collection Problems Using
ESP's in Metallurgical Industry
-	Procedures Manual for E.S.P. Evaluation
5

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SECTION IV
ASSESSMENT DISCUSSIONS
The technology assessments consisted of discussions between
the U.S. team and research groups from both universities and
industrial concerns. Several areas of significant research were
noted. Two specific examples include studies of the results of
varying the plate to corona electrode spacing and the investiga-
tion of the influence of adding devices designed to increase the
collecting electric fields in a limited region immediately down-
stream from the conventional electrostatic precipitator.
Another area of research that is related to particulate
control is involved with the development of instrumentation to
measure particulate physical characteristics. These research
topics were also included in the discussion.
Each visit is reviewed in this section including a summary
of the discussions and a list of the information exchanged.
Copies of the technical literature received at each meeting are
included as appendices to this report (in EPA-600/7~78-110a).
UNIVERSITY OF TOKYO
Professor Senichi Masuda
Department of Electrical Engineering
Professor Masuda reviewed the current and recently completed
research programs within his department that were related to
electrostatic precipitation. He provided copies of technical
presentations that resulted from this research. The principal
conclusions from the research is included in the discussion
review.
Back Corona Initiation
The electrical breakdown within a layer of material is re-
lated to the electric field that exists within the material.
For materials where Ohm's Law applies, the electric field is
proportional to both the current density and resistivity of the
material (E=jp). This applies when a single stage electrostatic
precipitator operates with a given corona current density (j)
and with a previously collected dust layer with a given resis-
tivity and thickness 
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resistivity is high (p >1011 ohm-cm), the electric field within
the dust layer is greater than that in the gas stream immediately
adjacent to the layer. This step function in the electric field
is caused by a surface charge layer on the dust (a) proportional
to the dielectric constant (a=eAE). This surface charge reaches
a steady state value such that the current density in the layer
is equal to the current density in the space adjacent to the
layer (current continuity),
The above considerations led to the design of some simpli-
fied laboratory experiments where the ash layers were represented
by millimeter thick layers of glass. The glass layers have pin-
holes that extend through the glass layers. Changes in the
normal and tangential electric fields are simulated by displacing
these holes using two sheets of glass. The U.S. team suggested
that the surface charge layer on the mating glass surfaces and
the air space between may upset the idealized conditions.
Several conclusions from these experiments are as follows:
-	Obtain no flashovers if E field low adjacent to collection
electrode (less than 5 kv/cm for this experimental con-
dition - related to mean free path).
-	Without flashovers - small streamers develop and quench
repetitively.
-	Two phenomena occur - streamer (bright) followed by
diffuse glow (low intensity) - must view with image
intensifier.
-	With E between 5 and 8 kv/cm channel streamers develop
into flashover - no back discharge.
-	If E>8 kv/cm flashover similar to those with no dust
layer.
Painting the glass surface with a thin layer of potassium
salt causes the flashover phenomena to change. Masuda postulated
that the emission of potassium atoms into gas stream influences
flashover (possibly surface resistivity is a more likely explana-
tion since extremely trace quantities of K atoms would result).
He also states that presence of N0Z, CLZ or S02 influences flash-
over. Professor Masuda believes that increasing current, when
diffuse glow (back corona) is present, leads to increased per-
formance in electrostatic precipitator. For the high resistivity
case, he expects O.lyA/cra2 is a good current density. (This is
well below any operating electrostatic precipitator.) Again
note - a very high resistivity material was used.
Dr. Masuda has studied the electrical upset phenomena asso-
ciated with current flow through a high resistivity dust layer.
He identified three classes of electrical upsets. The classes
7
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of upset observed parallel the observations of U.S. investiga-
tors . These classes are:
Electrical arc preceded by spark
Distributed glow discharge leading to spark
Glow discharge increasing to arc
These regions of operation are identified in graphs in his paper,
"Flashover Measurements of Back Discharge for Extremely High
Resistivity Dusts". See Section V-l and Appendix A.
Several investigators in various parts of the world have
studied the application of pulse energization for electrostatic
precipitators. In general, the voltage on the collection elec-
trode could be increased as a step function but the time constant
associated with the distributed capacitance of the electrode
system and the dust layer coupled with the dynamic resistance of
the same system causes the decay of voltage to follow a charac-
teristic with approximately 20 millisecond time constant.
Dr. Masuda has added an inductance to this system that leads
to an electrical resonance where sharp rise and fall times are
provided. Thus, a pulse can be added to a D.C. background
voltage that may lead to improved performance in some instances.
This system provides ^150 microsecond pulses to a standard
electrostatic precipitator system. The following figure illus-
trates the technique by which this is accomplished.
Professor Masuda gave us copies of the following papers in-
cluded as Appendix A.
-	Initiation Condition and Mode of Back Discharge
-	Back Discharge Phenomena in A Bias Controlled Pulse
Charging System
-	Light Measurement of Back Discharge
-	Initiation Condition and Mode of Back Discharge for
Extremely High Resistivity Powders
-	Utility Limit and Mode of Back Discharge in Bias-
Controlled Pulse Charging System
-	The Analysis of Electric Wind in Electrostatic
Precipitator by Laser Doppler Velocimeter
-	Fundamental Analysis of Electron Beam Gas Elimination
-	Motion of a Microcharge Particle Within Electrohydro-
dynamic Field
8
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SCR1
DC SOURCE
<-10 - 15kV)
PUUE FORMING CIRCUIT
LOAD
CI: load capacity including cable and stray capacities,
Rl: load resistance corresponding to corona discharge,
Co: main capacitor ( =10 CI)
L1: coil inductance for L-C oscillation
SCR1: switching element triggered by input signal vg,
L2: protective coil,
Rel: fly-wheel rectifier
SCR2: dwitching element for draing off the residual charge
Remark: By triggering the SCR the load condenser is charged up to a peak
value = 2 Vo by transient L-C oscillation through Co-SCR-LI-Q.
Then, the discharging oscillation occurs through CI-L1-L2-Re1-Co.
The following wave form of output pulse voltage can be obtained.
The pulse width is determined by the oscillation period given by:
A
t
At time t0, SCR2 is triggered. The pulse width of 150 - 500 microseconds are obtained.
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-	A Preliminary Study of Reentrainment in an Electro-
static Precipitator
-	Recent Progress in Electrostatic Precipitation
-	Plashover Measurement of Back Discharge
-	Basic Studies on Back Discharge Mode and Streamer
Preparation
-	Present Status of Electrostatic Precipitator
Technology
ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES
The visit with IHI provided an opportunity to develop an
understanding of the viewpoint of an electrostatic precipitator
manufacturer. This company relies heavily upon the developments
of Professor Masuda of Tokyo University. One of their signifi-
cant market items is the screen type collection electrode system
mounted in the exit zone of a conventional electrostatic pre-
cipitator. (See Appendix B.)
Charging Part (PAC Part) (Pulse and Alternating Current Charger)
The PAC part consists of a discharging electrode, a facing
electrode and a controlling electrode. A strong electric field
is generated between the facing electrode and the controlling
electrode by the power source.
The power source intermittently generates negative corona
ions from the discharging electrode and drives these ions to the
area between the facing electrode and the controlling electrode
to charge the dusts in gas with a maximum charge.
The power source will regulate voltage in the controlling
electrode and control the corona current.
Precipitating Part (ES Part) (Electrostatic Screen)
The ES part consists of guide electrode and precipitating
electrode which are placed perpendicularly to the gas current.
Those charged dusts at the PAC part are collected in the pocket
of the precipitating electrode by a strong electrical field
between electrodes and an electrohydrodynamic process which are
generated by the power source.
Attendees: Ichiro Hattory, Chief Engineer
Mikoto Yabe
Yuichi Wada
Akira Shibuya
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HITACHI LTD.
The visit with Hitachi Ltd. provided some insight into in-
dustrial research in Japan. The Research and Development Groups
of Hitachi were represented by Kohji Yoshida, Hikaru Turii,
Keizou Ootsuka, Hiroo Sakai, H. Yamada, Toshiaki Misaoa and
Ryutaro Morita.
Several groups in Japan are investigating the influence of
modifying the collection electrode spacing. Previous studies
have indicated that there is a potential for improving the col-
lection efficiency as a function of the required collection
electrode area by increasing the plate-to-plate spacing while
increasing the applied voltage in electrostatic precipitators.
The more promising applications are those with reasonably low
dust loadings such as roof monitors in metallurgical installa-
tions and similar areas.
The results of their plate spacing study led them to the
conclusion that a wire-to-plate spacing of about 250 mm was an
optimum spacing. They are continuing these studies. Their ex-
periments show that migration velocity is proportional to plate
spacing out to this distance. This, in their opinion, is some-
how related to electric wind transport.
They also have some collection electrode systems with 1.8 cm
diameter corona wires that are placed downstream of a conventional
electrostatic precipitator that is probably related to Professor
Masuda's work termed shoot (chute) baffles. This should provide
high field strengths for collection. (Their opinion is that
large wires decreases "electric wind" and enhances collection.)
Dr. Masuda is also concerned with electric wind where we, the
Soviets, and some Europeans tend to discount it at normal
electrostatic precipitator current densities. TKey show some
"schlieren" photos of electric wind effects and postulate that
this aids in particle transport to plate by increased turbulence.
This device is termed the EP-SB for electrostatic
precipitator-shoot baffle.
Configuration and Principle of EP-SB
The dusts at the entrance are charged electrically at the
EP part where the large size particles are precipitated. The
tiny particles are said to agglomerate to form large ones and
will be carried to the SB part with electrical charges. In the
SB part, the charged dusts are electrostatically precipitated by
the high electric field which is charged to the SB part. These
dusts will collide with shoot baffle and be precipitated
mechanically.
11
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This system is a one unit which is composed of EP part and
SB part. The number of individual units required can be deter-
mined in accordance with necessary performance. Each unit can be
installed in series with the gas flow. In case of using only the
SB part in the already installed electrostatic precipitator for a
purpose of improving efficiency, the exit-side exhaust pipe needs
to be removed and the SB part will be placed in that space.
Effects of Special Shoot Baffle (Patent applied for)
A modified shoot baffle system has been designed for the
purpose of reducing the pressure drop across the baffle system.
A double layer of channels is arranged in the direction of the
gas flow. The baffles have holes in the flat portion that allows
some gas flow through the channel to increase the percentage of
open area. The purpose of the two channels in the direction of
gas flow is to reduce dust reentrainment.
They also discussed a light scattering instrument with a
diluter that measures particles on a number per cubic meter basis
similar to Royco except that it provides a readout in mass when
calibrated. This instrument was claimed to give constant dilu-
tion ratios for particle sizes from 8.5 ym to about 100 ym.
Hitachi now markets both wet (intermittent spray) and dry
type roof mounted electrostatic precipitators for use on roof
monitors for metallurgical installations. The wet system uses
natural draft for air flow. (Dry migration velocity ^3.5/cm/
sec-Wet 5 cm/sec).
Hitachi plans to introduce some high temperature electro-
static precipitators in Japan. The U.S. Team discussed the
advantages and disadvantages of the high temperature precipita-
tors. The American experience with hot-side electrostatic
precipitator fly ash installations was of interest to the
Hitachi group.
Hitachi has also conducted some laboratory experiments using
a corona discharge to enhance the removal of SOz and NOx in a wet
electrostatic precipitator system. It is apparent that rather
high levels of electric power consumption are required because
the ozone concentration in the NOx removal system was about 5%.
At this time the electrical enhancement of SOx and NOx removal
is only of academic interest because of the anticipated high
power requirements. The small electrostatic precipitator
operated at high current densities simulates the use of a high
energy electron beam in promoting the conversion of S02 and NOx
to soluble compounds. In addition, the high current densities
may produce additional gas turbulence to enhance gas liquid con-
tact in the control device. Insufficient data are given to
allow for an engineering analysis of the experiment.
12
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List of papers that are included with translations in Appendix C
-	High Temperature Electrostatic Precipitator for Coal-
Fired Boiler (two papers summarized together)
-	High Temperature Electrostatic Precipitators for Coal-
Fired Boilers (pilot tests)
-	Electric Field Distribution in Wide Plate Spacing
Electrostatic Precipitator
-	Elimination of S02 and NO in a Corona Discharge Field
-	EP-SB Type Electrostatic Precipitators
-	Measurement of Suspended Particulate
-	Hitachi Dust Collection Equipment and Systems
-	List of Hitachi Installations
Sumitomo heavy industries (See Appendix D.)
Sumitomo Heavy Industries is a Japanese licensee of Joy-
Western electrostatic precipitators. They are also involved in
research related to varying the electrode spacing as a means to
develop an optimized electrostatic precipitator design. They
supply wide electrode spacing precipitators for roof monitors
similar to the Hitachi unit discussed previously. They also
have supplied an S03 conditioning system (H2SO^ evaporator) for
the Isogo Power Station. The discussion group from Sumitomo
included Mr. Noboru Watanabe, Shigeyuke Noso and Masakazu Sakai.
The Simitomo group utilizes a laboratory pilot scale elec-
trostatic precipitator to assist in sizing new precipitators.
The experiments make use of a redispersed dust.
The plate spacing experiments were conducted with a labora-
tory scale electrostatic precipitator that has the capability for
varying the collection electrode spacing. The measurements con-
sist of conducting mass loading experiments with a redispersed
dust at representative mass loadings and temperatures. The
precipitation rate parameter (effective migration velocity) is
calculated from the Deutsch equation from the measured efficiency,
volume flow rate, and collection electrode area. The experiments
are conducted over a range of electrode spacings and the results
are either plotted directly as the migration velocity vs plate
spacing or as the ratio of the migration velocity as determined
for a plate-to-plate spacing of 250 mm to that of the
13
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experimental conditions. In either case, the form of the
graphical presentation of the results are as shown below.
An example of the above, consider an experiment where two
channels each with a collection electrode area of five meters
square are used. In the first case, both channels are active.
Assume that an efficiency of 90% results from an area of 10
meters square yielding a precipitation rate parameter (w) of
10 cm/sec. Next, the center collection electrode is removed and
the corona electrodes are centered between the two remaining
collection electrodes. Assume that this experiment also yields
a collection efficiency of 90% with the same volume flow rate
yielding a precipitator rate parameter of 20 cm/sec. Thus, the
ratio of the precipitation rate parameter will be 2 when plotted.
The results of their studies of plate spacing are summarized
below. They find that optimum spacing depends on resistivity,
particle size and dust loading.
Recovery
boiler
w
or
a
Hi p ash
Blast Furnace
Carbon
Black
JL
200 300 400 500 600
Space (nun)
W is normalized to 250 mm for the comparison. Studies of varying
plate spacings are continuing.
A description of the roof mounted electrostatic precipitator
was provided.
NIPPON STEEL-KIMITSU WORKS
The research team visited the Kimitsu Steel Works of Nippon
Steel with Professor Jumpei Ando. The chief of environmental
control at the plant provided a briefing on the air pollution
control equipment installed at this site. The plant proper was
maintained in a very clean condition in all areas. The exterior
areas were decorated with grass, shrubs and trees, in accordance
with Japanese requirements.
The emissions from the stacks were well controlled. The
sinter machine dust was controlled by a wide plate spacing elec-
trostatic precipitator operating at about 200 kilovolts. Hoods
over the blast furnace and convertor effectively captured the
14
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emissions during the tap and oxygen blowing operations. In
general, the air pollution control equipment seemed to be well
designed and operated properly.
No technical literature was provided.
SHINWA TRADING AND ENGINEERING CO.
This company specializes in the control of emissions from
the iron and steel industry. They are a Japanese licensee of
American Air Filter, Louisville, KY. Their main areas of
specialization are coke ovens—charging and pushing, general
plant fugitive emissions and ferrosilicate electric arc furnaces.
They have a monopoly on these installations in Japan. They have
developed a traveling hood that connects into ductwork that
allows individual coke batteries to be controlled during charg-
ing. They utilize wet scrubbers for this application (wet
electrostatic precipitators also possible).
The charging door scrubber typically operates at a 99.9%
efficiency with a pressure drop of 1800 mm W.C. with an outlet
loading of about 40 mg/m3 (normal).
They handle coke battery door leaks via a hooding arrange-
ment. These emissions are usually controlled by the same device
that controls the pushing. (A separate device could be used.)
The control device typically operates for 3 minutes with 6
minutes between for the coke battery pushing emission applica-
tion.
The coke battery bag filter usually has bag life of 3 years.
They operate at ^130°C with polyestor bag material. (Japan has
some difficulty in attaining U.S. quality in glass bags.) Spark
arresters are used in conjunction with this system.
The outlet emissions are limited by statute to about 200
mg/m3 but the plant will typically control to 20 as a good
neighbor.
They also install a fluid coupling to the fan system to con-
serve energy during the quiescent period. This fluid coupling
allows operation from 30% to 100% fan capacity.
Shinwa does not now have any installations outside Japan but
they have the design for one B.H.P.* (Australia Iron and Steel)
in New Castle, Australia and have sold the technique to National
Steel in Detroit.
~Originally Broken Hill Proprietary.
15
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The ferrosilica furnace baghouse is equipped with bags made
of polyestor with stainless steel fibers woven into the material
to eliminate electrostatic effects.
The Japanese bag filter technology uses reverse air clean-
ing.
The U.S. Team questioned them about other future markets.
They stated that since steel is now down they have looked into
auto foundries (some experience with Toyoto), cement industries,
pharmacuetical and blast furnaces; are considering bag filters for
power stations.
VISIT TO ISOGO POWER STATION
We visited the facilities of the Isogo Power Station of the
Electric Power Development Company of Japan. This station is
restricted in S0X emissions to 60 ppm. The two units are
equipped with electrostatic precipitators with sulfuric acid con-
ditioning systems, followed by Chemico limestone scrubbers.
Unit 1 has Lodge Cottrell and Unit 2 - has Sumitomo Electrostatic
precipitators.
The precipitators were designed to attain a 90% collection
efficiency with gas conditioning. The units were initially
equipped with gas conditioning because of the uncertainty in coal
supply. They use coal from the Hokaida field with 15% ash, 0.6%
sulfur and a heating value of 6500 kcal/kg. The stated outlet
emissions from the electrostatic precipitators are 0.4 - 0.6
grams/normal cubic meters from Unit 2 and 0.3 - 0.4 grams/normal
cubic meters of gas.
They have experienced some problems with SO3 emissions when
injecting SO3. When injection exceeds about 20 ppm a brownish
plume results. Probably the formation of a very fine mist that
passes through the scrubbers. Normal injection rate is estab-
lished at 11 ppm.
The Chemico scrubbers operate with a 50% slurry of ground
limestone with a pressure drop of about 600 mm of water column.
The outlet loadings from the scrubbers are each about 0.02 grams
per normal cubic meter of gas. The gypsum formed contains
significant quantities of fly ash and sells for ¥100 per ton
(40C). About 100 tons per day with 15% by weight water is
processed.
The plant did a test burn of Montana coal about 3 years ago.
The particulate control problems (resistivity) in the electro-
static precipitator could not be overcome by S03 injection I The
plant personnel did not know which coal - but we suspect
Coalstrip.
16
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VISIT WITH PROFESSOR IINOYA - KYOTO UNIVERSITY
We met with Professor linoya on November 7, 19 77. We asked
Professor linoya to describe his current work, especially work on
baghouse economics and electrostaticly augmented filters. Pro-
fessor linoya gave us the following papers which he briefly
discussed. (Papers are in Appendix H.)
-	Dynamics of Naturally Cooled Hot Gas Duct
-	Particle Size Classification by Deposition Angle in a
Gas Centrifuge at Reduced Pressure
-	Electrification of Gas-Solids Suspensions Flowing in
Steel and Insulation-coated Pipes
-	Experments on the Electrical Dislodging of a Dust Layer
-	Comparison of Dust Cleaning Performance of Collapse and
Mechanical Shaking Types of .Fabric Filter
-	On the Economically Optimum Design of Bag Filter
-	Performance of a Micro-Cyclone'
-	International Seminar on Dus£ Collection
-	Error in Measurement of Gas Flpw Rate in Gas-Solids
Two-phase Flow by Use of Horizontal Diffuser
-	Dust Cleaning Dynamics in Reverse Collapse Type Bag Filter
-	A Method of Measuring Pressure Drop Parameters for Multi-
Compartment Bag Filter—Mechanical Shaking Type and
Reverse Collapse Type—
-	Performance of Fibrous Powder Bed Filter
Professor linoya is not continuing his work on economics or
any of the other area covered by the above papers.
We toured his laboratories and observed work on mist elimi-
nation and filter pressure drop and efficiency. Work in these
areas was not far enough along to be discussed.
Professor linoya showed us some dust feeders and a large
impactor for ambient sampling.
17
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Professor Iinoya plans to attend the particulate measure-
ment meeting in Ashville, North Carolina in May and the symposium
on particulate control in Denver, Colorado in July 19 78.
UNIVERSITY OF OSAKA, PROFESSOR TETSUO YOSHIDA
This visit to Osaka University was a very interesting part
of the evaluation of Japanese technology. This group was con-
centrating on the measurement of particulate characteristics.
Discussions of papers, research reports, and laboratory demon-
strations of the various measurement techniques were provided.
Dr. Yoshida gave an overall view of the research activities
in his lab according to the outline below.
Dr. Kousaka then discussed the method of size analysis using
gravitational settling with the ultramicroscope. The polydis-
perse aerosol is allowed to settle in a still chamber. By
counting the number and size at a given distance down and knowing
settling velocity the size distribution can be determined. Lower
size limit about 0.2y diameter.
Then a discussion of condensation growth was given. Three
methods of super-saturation work was 1) mixing hot and cold
streams, 2) steam injection, 3) adiabatic expansion. Results of
this work agrees with Southern Research Institute's study of
particle growth.
Les Sparks then summarized the work of Environmental
Protection Agency in condensation growth and the sieve plate
scrubber.
This group at University of Osaka assists in determining
environmental impact of solid waste disposal, organic sludge,
plastic waste, wood waste and hazardous waste. Japanese incin-
erators use electrostatic precipitators and scrubbers (S0X
control).
We were then shown laboratory demonstrations of:
-	Growth by condensation (collection in scrubber)
-	Aerosol size analysis (air sedimentation)
-	Turbulent coagulation of tobacco smoke
-	Thermophoresis effects
-	Particle reentrainment (CaCo3) at velocity from
20-100 M/sec
18
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AEROSOL RESEARCH AT UNIV. OF OSAKA PREFECTURE
ICoosnercialization
'{Coagulation in turbulent, flow
^Application to dust collector
in progress
Application to size analysis
by water sedimentation
Measurement of density oi
aerosol particles	
Application to size analysis for
evaluating collector efficiency
Identification of shape factor
of aggregates		
Particle grcwth in venturi
scrubber
Coagulation in a pipe flow
{J.Aerosol Sci.,in contribution]
Growth of aerosol particles
by condensation	
Coagulation in a stirred tank
IJ„Chem.Eng.Japan,10,142(1977)J
Coag<rtion by BroWtfian coagulation
tJ.cLn.Eng.Japan,8,317^(1975)) j ^
Aerodynamic properties of
aggregate particles
Mechanises of dispersion or
disintegration of aggregates
in fluids
Stability of fine water droplet
clouds
{J.Aerosol Sci.,in contribution]
Particle growth by steals
injection into aerosol
[J.Chen.Eng.Japan,in contribution]
Change in size and number
concentration of aerosol
particles by coagulation
Application to measurement of
thermophoretic velocity of
aerosol particles
tJ. Cheap. Eng .Japan, 9,147 (1976)]
Effect of Brownian coagulation,
diffusion on fine particle size
analysis by sedimentation method
{J.Cheia-Eng. Japan, 10,46(1977)J
Effect of Brownian coagulation
and Brownian diffusion on
gravitational settling of aerosols
[J.Chem.Eng.Japan,8,137(1975)]
Particle growth by mixing of hot
saturated aerosol with cold
aerosol
tt&EC, Fundam., 15, 37(1976]]
Application of particle enlarge-
ment by condensation to
industrial dust collection
(l&EC,Process Design and
Developnientjin contribution]
Development of a new
technique of particle
size analysis using an
ultrainicroscope	
Behavior of aerosols undergoing
Brownian coagulation, Brcwnian
diffusion and gravitational
settling in a closed chamber
(J* Chem.Eng.Japan,9,140(1976)J
Principle of size analysis and
nunber concentration of aerosol
particles including small
water droplets
II&BC, Fundanu, 14, 47(1975)]
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These experiments made use of the ultramicroscope. This
seems to be a most capable group.
The following publications are given in Appendix I:
-	Growth of Aerosol Particles by Condensation
-	Stability of Fine Water Droplet Clouds
-	Behavior of Aerosols Undergoing Brownian Coagulation,
Brownian Diffusion and Gravitational Settling in a
Closed Chamber
-	A New Technique of Particle Size Analysis of Aerosols
and Fine Powders Using an Ultramicroscope
-	Turbulent Coagulation of Aerosols in a Pipe Flow
-	Effects of Brownian Coagulation and Brownian Diffusion
on Fine Particle Size Analysis by Sedimentation Method
-	Constant Pressure Filtration of Power-Law Non-Newtonian Fluids
-	Experimental Study of Thermophoresis of Aerosol Particles
-	Turbulent Coagulation of Aerosols in a Stirred Tank
-	The Effect of Neighboring Fibers on the Single Fiber Inertia-
Interception Efficiency of Aerosols
-	Pressure Drop and Collection Efficiency of an Irrigated
Bag Filter
-	Growth of Aerosol Particles by Steam Injection
-	Effect of Brownian Coagulation and Brownian Diffusion
on Gravitational Settling of Polydisperse Aerosols
-	Change in Particle Size Distributions of Polydisperse
Aerosols Undergoing Brownian Coagulation
-	Application of Particle Enlargement by Condensation to
Industrial Dust Collection
MITSUBISHI HEAVY INDUSTRIES
We visited the Takasago Research Institute of Mitsubishi.
Messrs. Matsui, Saito, Toshiro and Dr. Matsumoto were present.
Mr. Saito reviewed the work of the three Mitsubishi research
laboratories—Takasago, Nagasaki and Heroshima.
20
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The Mitsubishi electrostatic precipitator research is con-
ducted at this laboratory. Mitsubishi does not study specifically
the collection of fine particles but rather studies improving the
overall collection efficiency of the electrosatatic precipitator.
We were given sales brochures and a paper on Dust Collection
Techniques. (See Appendix J.)
The Mitsubishi Heavy Industries group is a cooperative
licensee of the Lurgi group in Germany. They study the electrical
and aerodynamic factors related to particulate collection with an
electrostatic precipitator including the following items:
-	Effect of varying plate spacing
-	High resistivity effects
-	Space charge suppression
-	Corona electrode configuration
-	Temperatures
-	Gas flow distribution
-	Wet and dry collection
Their major high resistivity problem is with Sinter machine
dus t.
Their studies of plate spacing show that so long as a given
current density is maintained, increasing plate spacing with a
constant plate area increases efficiency. This applies to
coarse dustr light loadings and high temperatures.
With respect to high resistivity, they have developed a
measurement cell that allows temperature and pressure to be
varied. They determine the sparkover characteristics with clean
gas and with a dust layer deposit in a wire-pipe electrostatic
precipitator. From this they determine the temperature where the
spark charcteristics are independent of the presence or absence
of the layer. They term this point the back corona vanishing
point. We believe that this term is incorrect, but it does in
fact define the temperature at which the influence of the dust
layer is insignificant and as such is a valuable experiment.
This will yield results similar to those with the electrostatic
precipitator field mobility analyzer developed at Southern
Research Institute. (The electrostatic precipitator system
operates in situ at a given temperature. This Japanese device
has been used to study the fly ash from Hayden, Colorado.)
They have tried a number of methods to reduce the effect of
high resistivity of Sinter machine dust—all failed. Large
spacing, water injection, ammonia injection and mixing carbon
dust with gas stream. The carbon was essentially all collected
in the inlet field. This helped that field only. (They may have
injected only large particles because redispersion is difficult.)
They are now evaluating different corona electrodes.
21
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The space charge suppression can be handled over a limited
range by the use of high current density corona electrodes. The
installation of corona electrodes with a small radius of curvature
leads to a corona inception voltage less than that for normal
electrodes. Thus, a higher current density exists for the same
operating voltage for the smaller diameter wires. Therefore,
since the sparkover voltage will be approximately the same for
the two-wire diameters, the space charge suppression problem will
be alleviated somewhat.
They also design installations for no flow-power off rapping.
Four chambers are installed with dampers. One-fourth is shut off
and rapped. This improves performance for Sinter machine opera-
tion.
They also think "electric wind" erosion is significant.
The laboratory illustrated the effect of back corona by
photographing particle trajectories (8-10jj particles). A strobe
light illuminates the particles. Trajectory is to the plate w/o
back corona but approaches and reverses with back corona.
The design for new installations is generally based on pilot
studies. They scale up with an experience factor. The pilot and
full-scale V-I curves are in general identical except the spark-
over voltage is greater in pilot.
We toured the laboratory to view their equipment. The lab
was well equipped.
Pilot
Pull Scale
V-I
Vspk
W
V-I
V's = Vspk
W' = BW (B is a proprie-
tary parameter)
22
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SECTION V
LITERATURE REVIEW
This section provides summaries of the technical literature
supplied at each meeting that relate to particulate control.
Complete copies of the papers are included in the respective
Appendices. The order for the summaries coincide with the lists
provided in Section IV.
UNIVERSITY OF TOKYO
This group of papers provides information about the research
activities under the direction of Professor Senichi Masuda.
Complete copies of the papers are reproduced in Appendix A.
Initiation Condition and Mode of Back Discharge, S. Masuda and
A. Mizuno
This paper provides a detailed discussion of the development
of back corona in layers of high resistivity material. The dis-
cussion includes the development of the theory, experimental
investigations utilizing tissue paper and millimeter thick layers
of glass and mica, and development of the factors that lead to the
development of back corona. In this research, the thin glass and
mica layers had pinholes through the material such that tangential
electric fields could be established by utilizing two layers with
the pinholes displaced.
The breakdown characteristics are classified into three
modes—space streamer, surface streamer and mixed streamer. The
first and third modes occur when the electric field adjacent to
the layer exceeds about 5 kv/cm with ions formed in the inter-
electrode space. The second mode develops with field strengths
less than 5 kv/cm with ions only generated adjacent to the layer
surface.
This paper provides a good background into the study of back
corona. Even though the experiments utilized a simulated dust
layer, the results in general apply to electrostatically collected
dust layers.
23
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Back Discharge Phenomena in Bias Controlled Pulse Charging System,
S. Masuda, I. Doi, I. Hattori and A. Shibuya
The use of pulsed electrical power supplies has been con-
sidered as a means to reduce the development of back corona in
electrostatic precipitators collecting high resistivity fly ash
by several investigators. Dr. White describes experiments with
pulse power supplies in his book, "Industrial Electrostatic Pre-
cipitation". The Environmental Protection Agency sponsored some
research with Belco Engineering in the early 1970's. In general,
the studies and experiments failed to provide the degree of im-
provement expected. This failure to improve was related to the
filtering action of the collected high resistivity dust layer and
the corona-collection electrode system.
This paper describes experiments with a laboratory and sub-
sequently a pilot scale electrostatic precipitator that involves
the addition of a third electrode located near the corona wire.
This three-electrode system provides a high value of D.C. field
adjacent to the collection electrode by applying a fixed voltage
with very little or no corona current to serve as the collecting
field. The corona current is supplied by applying pulses of
voltage to the corona electrode that provides current pulses of
about one hundred microseconds duration with a variable repetition
rate. This provides a free ion density in the interelectrode
space that is sufficient to charge the particles but low enough,
on the average, to avoid the formation of back corona. The
collection field is provided by a near-passive electrode system
while the charging current is supplied intermittently. This
arrangement simulates a distributed two-stage electrostatic
precipitator.
This technique represents a new approach to the solution of
the high resistivity problem by electrical means. This repre-
sents a significant improvement in the use of pulse energization
for electrostatic precipitators.
Light Measurement of Back Discharge, S. Masuda and A. Mizuno
This paper describes the results of a study of the light
that is associated with the formation of back corona. Two dis-
tinct light forms are categorized. The primary light wave forms
in the dust layer and propagates to the corona electrode. The
secondary wave appears coincident with the arrival of the primary
wave and travels along the dust layer surface. At reduced
pressures (p
-------
Initiation Condition and Mode of Back Discharge Extremely High
Resistivity Powders, S. Masuda, A. Mizuno and K. Akutsu
This laboratory study of the formation of back corona pro-
vides significant fundamental information of the characteristics
of reverse ionization. The study clearly shows the dependence on
dust layer thickness, indicating that the electrical space charge
within the dust layer adds to the Ohm's Law field to cause the
development of a high electric field adjacent to the grounded
electrodes. The most significant point of this research is the
indication that a dust layer of high resistivity material will
build up until a limiting value of electric field is reached
adjacent to the grounded electrode. At this point, back corona
will develop in localized regions reducing the particulate
buildup severely.
Utility Limit and Mode of Back Discharge in Bias Controlled Pulse
Charging System, S. Masuda, I. Doi, I. Hattori, and A. Shibuya
This paper describes the use of a pulsed charging system
that operates with a three-electrode geometry in the charging
section. The pulse charging pulse is superimposed on a D.C.
exitation which, in conjuction with the third electrode, reduces
the development of back corona. This pulse system differs from
attempts to utilize pulsed power supplies in the United States in
that the pulse charging is applied in series with a D.C. Bias,
rather than using a pulse s-upply alone. Sharp rise and fall
edges on the pulse voltage supplied to the electrical assembly
are used. This is also in contrast with attempts by U.S.
researches who could attain sharp rise times but the decay time
of the voltage was related to the electrical time constant of the
electrode system and dust layer combination.
The Analysis of Electric Wind in Electrostatic Precipitator by
Laser Doppler Velocimeter, S. Masuda, K. Akutsu, and K. Aihara
This paper describes experiments conducted with a laboratory
apparatus to investigate the phenomena of the electric wind from
the corona electrode and from back ionization. It is to be noted
that the conditions for this experiment deviates significantly
from those conditions existing in commercial electrostatic pre-
cipitators in that the current densities are expected to be
somewhat greater than that usually encountered aiid the glass
plate represents an unrealistically high resistivity. The point-
to-plane system with close spacing provides for very high current
densities and no requirement for a flow of return air such as is
present in operating units. Therefore, the conclusion from this
paper relates to the experimental conditions existing in the
laboratory apparatus.
25
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In this experiment, electric wind velocities were on the
order of a few meters per second with a current of 5 microamperes.
The actual plate area used for the experiment was not stated but
a current density of 640/vtA/m2 was stated. This suggests a plate
area of about 100 cm2 in the measurement region. However, for a
point-to-plane experiment with 5 cm between the point and plane,
a significant variation in current as a function of distance along
the plane is expected. Thus it is difficult to determine the
current density at the plate.
Fundamental Analysis of Electron Beam Gas Elimination, S. Masuda,
K. Akutsu and M. Harano
This paper discusses the removal of NO and SOx in the pre-
sence of high-energy electrons. A beam of one to two MeV
electrons is injected into the gas stream. The high-energy
electron oxidizes the NO to enhance the removal of this gas. The
removal of SO2 is improved by the injection of ammonia into the
reaction space. The experimental results show that the removal
efficiency for the gases is related to the electric power input
into the reaction space.
Motion of Microcharge Particle With Electrohydrodynamic Field,
S. Masuda and Y. Matsumoto
This paper provides a theoretical analysis of the shoot
(chute) baffle downstream collector that is one of the major
modifications to electrostatic precipitators that Dr. Masuda is
investigating. In addition to the theoretical analysis, experi-
ments utilizing lycopodium particles and photographs of their
trajectories are included. This device is a modified two-stage
precipitator. The paper is a good background paper related to
the behavior of charged particles in an electrostatic field.
A Preliminary Study of Reentrainment in an Electrostatic Precipi-
tator , J.D. Bassett, K. Akutsu and S. Masuda, Journal of Electro-
statics, pp 311-325 (1977)
This paper describes the results of a study to define the
conditions under which direct reentrainment occurs from an
electrostatically deposited dust layer. The study includes
photographs of particle trajectories with and without the exist-
ence of back corona. Distinct differences in the trajactories
were noted with back corona.
Recent Progress in Electrostatic Precipitators, S. Masuda
This paper is a survey of the research programs that were
active in the 1975 period. A general discussion of Electrostatic
Precipitator Theory is used as an introduction. The research
programs at the University of Tokyo are reviewed in detail.
26
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Flashover Measurements of Back Discharge, S. Masuda and A. Mizuno
This paper describes conclusions from measurements from a
gas discharge with a current flow through a high resistivity layer
at varying conditions of temperature and pressure. Two modes of
electrical breakdown were identified: streamer or steady glow.
The development of each mode is dependent upon the gas mean free
path, dust layer thickness and layer resistivity. The streamer
mode includes a steady D.C. component of current with superim-
posed trichel pulses, while the glow mode is characterized by a
steady D.C. current. The mechanism of breakdown begins with a
spark breakdown through the dust layer leading to an ionized
channel. Initially the location of these channels moves randomly
over the surface of the layer. As the voltage (and current
density) is increased the localized breakdown occurs repetitively
in one location, from which a streamer develops. The resistivity
of the dust layer strongly influences the initial point where
electrical breakdown occurs but after breakdown, the layer
resistivity becomes inconsequential.
Basic Studies on Back Discharge Mode and Streamer Propagation,
S. Masuda and A. Mizuno
This paper, presented at the fourth international clean-air
congress, represents a continuation and summary of the research
reported in the first paper in this section, "Initiative Condi-
tions and Mode of Back Discharge". The three modes of layer
breakdown are described in detail and graphically illustrated.
The experiments are with a point-to-plane corona device with a
high resistivity layer simulated. A graph with axes of average
electric field and current density is divided into regions that
yield surface streamers, space streamers and mixed streamers.
Waveforms of the light emitted for the various conditions are
shown. Studies of the influence of ionic mean free path on
flashover voltage are reported.
Present Status of Electrostatic Precipitator Technology, S. Masuda
This paper was presented at the Electrochemical Colloqium of
the Technical University of Munich in 1977. It is closely related
to the previous paper, "Recent Progress in Electrostatic Precipi-
tation". A general discussion of the various aspects of electro-
static precipitation is included. The specific topics covered
were particle charging mechanisms, migration of charged particles,
gas turbulence, jet streams, corona wind, back corona and particle
reentrainment. Also, experiments with variable collection elec-
trode spacing are described. The influence of corona wind is
stressed rather heavily. Professor Masuda attributes several
factors to corona wind that other investigators tend to disregard.
This probably bears further investigation.
27
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ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES NEW PRECIPITATION TECHNIQUES—
"PAC-ES
This technical information bulletin describes two develop-
ments from Professor Masuda; pulse and alternating current charger
(PAC) and the electrostatic screen (ES) collecting device. The
theoretical descriptions of the devices are covered in the litera-
ture from Professor Masuda at Tokyo University (Part 1 of Section
V). The practical factors and some general discussions are
included in the bulletin.
HITACHI LTD. (Papers in Appendix C.)
High Temperature Electrostatic Precipitator for Coal-Fired Boiler,
H. Imanishi, Y. Oafcaki, K. Oofcsuka and K. Waianabe	
This paper is a general discussion paper summarizing the
state of technology for electrostatic precipitators installed on
the hot gas side of air preheaters in coal-fired electric utility
boilers. The paper also includes a short summary of electrostatic
precipitator technology in general. The discussion paper is con-
sidered to be significant because there is limited Japanese
experience with the so-called hot side electrostatic precipita-
tors. This is considered to be a good summary paper.
A second paper of the same name summarizes the results of a
pilot scale test at the Ebetae Generating Station of Hokkaido
Electric Power Company. The conclusion was that the performance
of the high temperature pilot electrostatic precipitator performed
acceptably. This paper was coauthored by Mr. Y. Oataki of
Hokkaido Electric.
Electric Field Distribution in Wide Plate Spacing Electrostatic
Precipitator, T. Misaka, s. Matsubara and K. Fujibayaski
This short paper reports the results of a laboratory inves-
tigation of the electric field distribution within the inter-
electrode space of a wire and plate electrostatic precipitator.
The electric field was mapped for electrode spacing of 250,500
and 750 mm. The method utilized was a conducting sphere dropped
through the interelectrode space into a Faraday cage.
Elimination of SOg and NO in a Corona Discharge Field, K. Ootsuka,
T. Yukitake and M. Shimoda
This paper discusses the results of an experiment to utilize
the ozone formed in a high current density corona to oxidize
sulfur and nitrogen oxides to water soluble forms. The process
requires a considerable amount of electrical energy, since the
ozone concentration in the experimental apparatus was considerably
hitter them in conventional electrostatic precipitators (^5%).
28
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Hitachi EP-SB Type Electrostatic Precipitator
This discussion provides a short summary of a high electric
field, low current density electrostatic precipitator that is
installed downstream from a conventional electrostatic precipi-
tator. Sketches and examples of the specifications applicable
to a cement plant are given.
Measurement of Suspended Particulates, K. Ootsuka, S. Tsuji and
Y« Arikawa
This paper discusses the development of an optical measure-
ment system used in conjunction with a sample dilution system to
determine the concentration of particles suspended in a gas
stream. A sample of the gas stream is extracted, diluted with
clean air and viewed with an optical particle counter. The
authors claim that the readout can be in mass loading as well as
number density when properly calibrated.
There were no summaries provided for Hitachi Dust Collection
Equipment and Systems and List of Hitachi Installations.
SUMITOMO INDUSTRIES (Paper in Appendix D.)
The Sumitomo group provided a publication describing their
capabilities in providing roof mounted electrostatic precipita-
tors for low mass loading applications. This document includes
comparison with alternative particulate control techniques. The
roof mounted electrostatic precipitators utilize wide plate
spacing and high voltage as a means for reducing the weight of
the control device.
There was no literature to review for
Nippon Steel-Kimitsu Works
Shimwa Trading and Engineering Co.
Visit to Isogo Station
KYOTO UNIVERSITY
The research program at Kyoto University is related to the
fundamental behavior of dispersion dusts. The literature review
of the papers (see Appendix H) follows.
Dynamics of Naturally Cooled Hot Gas Duct, K. Hotta, N. Yamamuro
and K. Ixnoya
This paper describes the development of a mathematical model
of the transient thermal behavior of a gas duct that is cooled by
exposure to ambient conditions. The study is applicable to
29
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ductwork leading from a process to a fabric filter installation.
Particle Size Classification by Deposition Angle in a Gas Centri-
fuge at Reduced Pressure/ Z. Tanaka, H. Takai, N. Okada and K.
Iinoya
This paper discusses the results of a study of the operation
of a Bahco type of centrifugal classifier operated at reduced
pressures. The reduction in pressure causes an increase in the
average molecular spacing which causes the Cunningham correction
factor to Stokes Law to become effective at larger particle
diameters. Both theoretical and experimental results are pre-
sented.
Electrification of Gas-Solid Suspensions Flowing in Steel and
Insulating-Coated Pipes, H. Masuda, T. Komatusu, N. Mitsui and
K. Iinoya
This paper discusses the results of a laboratory study of
the contact charging of dust particles flowing in both conducting
and nonconducting pipes. This tribo-electric charging study is
of interest as a potential means for determining mass loading in
a gas stream. This principal is utilized in an instrument, the
Konitest meter, developed in West Germany. This phenomenon is
also responsible for electrical sparking in some dust laden gas
streams that may lead to ignition and possibly explosion, in some
instances.
Experiments on the Electrical Dislodging of a Dust Layer,
K. Makino, K. Iinoya, M. Shibamoto, S. Toyama and M. Ikazaki
This study was aimed at defining electrical means to dis-
lodge both insulating and conducting powders from various types
of transport media. A moving electric field was generated by
applying phased A.C. power to an electrode array. At this time,
this technique does not seem to apply to electrostatic particu-
late collection.
Comparison of Dust Cleaning Performance of Collapse and Mechani-
cal Shaking Types of Fabric Filter, K. Iinoya, K. Makino,
Y. Mori, J. Okutani and H. Kawabe
The cleaning characteristics of the above fabric filter
collectors are studied. Optimal cleaning durations and cycles
are determined experimentally. In general, shorter cleaning
durations are found to be advantageous.
30
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On the Economically Optimal Design of Bag Filter, K. Iinoya,
K. Makmo, and N. Tanaka
This paper develops a method with equations to guide the
designer of a fabric filter system in determining the economically
optimum unit for a given installation. Both theoretical and
practical considerations are included. Assumptions for bag life
related to the cleaning cycle are given.
Performance of a Micro-Cyclone, K. Iinoya and A. Nakai
The performance of a micro-cyclone, collection efficiency
vs pressure drop, was experimentally determined using monodisperse
aerosols. The pressure drop was proportional tc the square of
the inlet velocity. The collection efficiency can be correlated
with an inertia parameter with a modification factor for particle
si ze.
International Seminar on Dust Collection, K. Iinoya
This paper is a summary of a meeting to discuss the general
properties of dust collection. Discussions were presented by
F. Loffler of Germany, E. C. Potter of Austrailia, M. First of
the United States, and W. Stober of Germany. This summary is
reproduced in the Appendix.
Error in Measurement of Gas Flow Rate in Gas-Solids Two-Phase
Flow by Use of a Horizontal Diffuser, H. Masuda, Y. Ito, and
K. Iinoya
This paper discusses errors in measurements of flow in a
gas-solids gas stream. The experimental powders used are un-
usually large but the analytical procedure is useful.
Dust Cleaning Dynamics in Reverse Collapse Type Bag Filter,
K. Makino, Y. Mori, N. Takado, and K. Iinoya	:
This study provides information about the influence of the
cleaning cycle on the operation of the fabric filter. This
particular study was concerned with a collapse type of cleaning.
Time constant for recovery were developed.
A Method of Measuring Pressure Drop Parameters for Multi-
Compartment Bag Filter—Mechanical Shaking Type and Reverse
Collapse Type—-K. Iinoya, K. Makino, K. Ueshima, M. Lin and
Y. Mori
This paper discusses the development of a means for evalu-
ating the performance of bag filters. Typcially, one or two
years is required for a field installation to develop an operating
history. This study discusses the development of a pressure
drop-collection efficiency history for a given installation to
be applied to estimating the performance of new installation.
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Performance of Fibrous Powder Bed Filter, K. Iinoya, K. Makino,
T. Imamura, and H. Okura
This paper discusses the results of a study of the collection
characteristics of a packed bed filter. The collection efficiency
and pressure drop of the device was presented. Empirical per-
formance equations were developed.
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UNIVERSITY OF OSAKA PREFECTURE
The research program at the University of Osaka is concen-
trated on the development of measurement techniques and in the
fundamental behavior of particles suspended in a gas stream.
This group of papers provides a good introduction to the physics
of fine particulates.
Papers have been prepared that consider the combined influ-
ence of growth by condensation, Brownian diffusion and coagulation,
gravitational settling and thermophoretic movements. The group
has perfected the use of an ultramicroscope connected to a tele-
vision optical system to study the various phenomena. The
following summaries describe these papers , reprinted in Appendix I.
Growth of Aerosol Particles by Condensation, T. Yoshida, Y.
Kousaka, and K. Okuyama
This paper addresses the theoretical and experimental aspects
of condensation growth. This principle is used in instruments to
determine number concentrations of fine particles. The experi-
mental determinations were made with the ultramicroscope. Super-
saturated gas streams were found to provide for the growth on the
particles active as condensation nuclei.
Stability of Fine Water Droplet Clouds, Y. Kousaka, K. Okuyama,
K. Sumi and T. Yoshida
This experimental study provided information important to
the use of condensation growth of fine particles. The results of
this study indicates that micron size droplets will evaporate
even in the presence of saturated air. Thus, very few fog par-
ticles will be in a state of equilibrium. Thus, care should be
exercised in the use of this phenomenon in designing size sensi-
tive measurements.
Behavior of Aerosols Undergoing Browning Coagulation, Brownian
Diffusion and Gravitational Settling in a Closed Chamber,
K. Ikuyama, Y. Kousaka and T. Yoshida
This theoretical and experimental paper addresses the funda-
mental behavior of aerosols in a closed chamber. The mechanisms
lead to growth by collisions, wall losses by diffusion and
settling on the bottom surface. This fundamental study leads to
the development of instrumentation for real time determination of
a particle size distribution in a particulate laden gas stream.
A New Technique of Particle Size Analysis of Aerosols and Fine
Powders Using an Ultramicroscope, T. Yoshida, Y. Kousaka and
K. Ikuyama
This paper describes an instrument for sizing particles
while they are suspended in a stationary gas stream. The
33
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ultramicroscope is focused at some distance down into a view
chamber. The instrument is used to view the results of gravita-
tional settling of particles within the view volume. Near real
time results are available. Data for stearic acid, tobacco
smoke, fog and iron oxide particle size distribution are pro-
vided.
Turbulent Coagulation of Aerosols in a Pipe Flow, K. Okuyama,
Y. Kousaka and T. Yoshida "
Two factors lead to collisions between particles suspended
in a turbulent gas stream: velocity differences because of
spatial inhomogeneities in the flow pattern and the differential
inertion of different particle sizes. Both mechanisms are active
for the flow in a pipe. These factors were evaluated using the
ultramicroscopes.
Effects of Brownian Coagulation and Brownian Diffusion on Fine
Particle Size Analysis by Sedimentation Method, K. Okuyama,
Y. Kousaka, fr. Miyazak, and T. Yoshida
This paper discusses the effects of diffusion and coagula-
tion on the Stokes-Cunningham conditions. These factors
influence the accuracy of particle size determinations by sedi-
mentation techniques. Theoretical analyses and some experimental
varifications are included.
Experimental Study of Thermophoresis of Aerosol Particles,
Y. Kousaka, K. Okuyama, S. Nishio, and T. Yoshida
The ultramicroscope described above can be used in conjunc-
tion with a special thermally controlled cell to study the
thermophoretic transport of particles. The results of experi-
ments from a variety of particulates are compared with the
theoretically predicted behavior. Good agreement is indicated
in these comparisons.
Turbulent Coagulation of Aerosols in a Stirred Tank, K. Okuyama,
Y. Kousaka, Y. Kida and TV Yoshida	'
The ultramicroscope serves as a useful tool for evaluating
the many physical phenomena related to fine particles suspended
in a gas stream. This experiment evaluates the turbulent coagu-
lation particles within the view volume of the instrument. The
turbulence is provided by utilizing a stirred tank. Tobacco
smoke was the principal material used in the experiment. The
deviation in results associated with wall depositors were
treated mathematically.
34
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Presssure Drop and Collection Efficiency of an Irrigated Bag
Filter, T. Yoshida, Y. Kousak, S. Inake and S. Nakai
This paper discusses the results of an investigation to
develop a means for utilizing fabric filters on high temperature
applications. The surface of the fabric filter is flooded with
a water film. In addition to thermally protecting the fabric
and removing the material that would form the cake in a conven-
tional bag filter, the liquid film provides two collection
mechanisms that differ from normal^fabric filter collection
mechanism: collection by an orifice in an infinite plate and
collection by the shutter action of an orifice. The liquid
flowing over the fabric surface forms a continuous sheet.
Pressure differentials across the fabric leads to a break in the
surface film. The pressure drop as a function of operating time
is essentially constant because of the action of the liquid film,
in contrast to that in a dry fabric filter when pressure drop
and collection efficiency increase with time of operation.
Growth of Aerosol Particles by Steam Injection, T. Yoshida,
Y. Kousaka, K. Okuyama and F. Nomyra
This paper discusses the results of growing particles by the
condensation of water vapor on the particles. The fine particles
act as condensation nuclei in a supersaturated gas steam. The
results of this experiment are consistent with a similar study in
the United States that led to the development of a condensation
nuclei counter that is currently used for particle number density
determination. Both theory and experimental information are
included.
Effect of Brownian Coagulation and Brownian Diffusion on Gravita-
tional Settling of Polydisperse Aerosols, T. Yoshida, Y. Kousaka,
K. Okuyama and S. Nishio
This paper includes the development of equations based on the
theoretical behavior of a polydisperse aerosol as well as an ex-
perimental study using the ultramicroscope. Stearic acid and
tobacco smoke aerosols were used in the study. The number
densities for the studies ranged from 106 to 108 particles per
cubic centimeter.
Change in Particle Size Distributions of Polydisperse Aerosols
Undergoing Brownian Coagulation, TV Yoshida, K. Okuyama, Y.
Kousaka and Y. Kida
This paper reports the result of a study to evaluate the
influence of a single factor on the particle size distribution—
Brownian coagulations. A very high number density polydisperse
aerosol was confined in a chamber. The high number density
assured that coagulation was the primary mechanism active within
35
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the system. The ultramicroscope was used to study the phenomena
and theoretical confirming equations were provided.
Application of Particle Enlargement by Condensation to Industrial
Dust Collection, T. Yoshida, Y. Kousaka, K. Okuyama and F. Nomyra
Introduction—
Industrial application of the principles of growth of aerosol
particles by condensation was made in this paper. Condensation
of water vapor on aerosol particles, not consisting of soluble
substances, occurs when a certain degree of supersaturation is
produced around the particles. Supersaturation is usually pro-
duced by one of two methods. In one method, hot saturated air is
mixed with cold air, while in the second method steam is injected
into the air. Methods of developing these processes economically
were discussed in this paper. The fundamental considerations of
these two processes were discussed by the authors in an earlier
paper.
Discussion-
Four processes for producing particle growth by condensation
were discussed. The first process named "A" applies for high
temperature and high humidity exhaust gas. In this process, the
humidified gas is divided into two parts. One is contacted with
cooling water and then mixed with the other in a mixing chamber.
In a similar process called "A'", one part of the gas is humidi-
fied and heated by hot water to form high temperature saturated
air while the other part is humidified by cool water to form low
temperature saturated air. The two parts are then mixed. For
low temperature exhaust gas, the steam injection method is effec-
tive, but it requires saturated steam. This process is labeled
"B". At intermediate temperatures of the exhaust gas the process
is called "B'".
In the experiments described in this paper, the temperature
of the gas was several hundred degrees Celsius for process "A"
and about 200 degrees for process "B'". Tobacco smoke with volume
mean diameter of 0.85 microns and dust particles with volume mean
diameter of 0.1 microns were used as condensation nuclei. The
total gas flow rate was 180 1/min.
MITSUBISHI HEAVY INDUSTRIES, LTD.
The Latest Dust Collecting Technique, Y. Saito, K Tashiro, S.
Komura, N. Tachibana, K. Matsui and K. Yada
This paper presents a qualitative summary of the Mitsubishi
philosophy of electrostatic precipitator design and a summary of
precipitator technology. The results of several laboratory in-
vestigations are also mentioned. This summary includes discus-
sions of the significance of reentrainment, high resistivity,
36
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high dust loading of fine
sulfur and nitrogen oxide
particulates and the influence of
removal. (See Appendix J.)
37
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SECTION VI
TECHNOLOGY ASSESSMENT
The Japanese research activities related to electrostatic
precipitation and particulate measurement techniques are judged
to be on a par with, and in some instances, surpass those of the
other major countries in the world. The specific areas where
the electrostatic precipitation technology seemed to lead include
the following:
Fundamental studies of back corona formation,
Pulse electrical energization with a three-electrode
geometry, and
Special electrode configuration to provide high collection
electric fields.
Their experiments with variable collection electrode spacings are
also very timely. Optimizing the electrode spacing to match the
conditions of mass loading, particle size distribution and par-
ticulate resistivity can lead to a reduction in the weight of a
given installation while maintaining the necessary particulate
collection efficiency.
Another area of significant research is that related to par-
ticulate measurement techniques. The development of the ultra-
microscope at the University of Osaka and the optical sizing
instrument with a wide particle size range diluter are two of the
more significant developments in this area.
The efforts of Professor Masuda at the University of Tokyo
represents a most significant area of research related to electro-
static precipitation. His studies of the factors leading to the
formation of back corona represents one of the more fundamental
attempts to investigate this phenomenon. His work with a simu-
lated dust layer has allowed the back corona condition to be
classified into three regions dependent upon the value of the
electric field adjacent to the collected dust layer—space
streamer, surface streamer, and mixed streamer modes.
The next significant contribution to electrostatic precipi-
tator technology is the study of pulse energization for high
resistivity dust applications. Many investigators have evaluated
38
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the use of pulsed power supplies. The basis for considering the
use of short duration pulses was that since the dust layer on the
collection electrode acted as an resistance-capacitance filter,
the average electric field in the dust layer would be propor-
tional to the average current rather than the peak current. Un-
fortunately, the average electric field adjacent to the dust
layer was also reduced and the collection efficiency for the
device was less than hoped for.
Professor Masuda has circumvented this problem by utilizing
a three-electrode system. The collection field is established
by applying a high voltage between passive electrodes that pro-
vide either little or no corona current. The corona electrode
situated in the vicinity of the third electrode is supplied with
short duration pulses (20 microseconds), at a controllable
repetition rate, to provide the current necessary for particle
charging. Thus, the system maintains an acceptable charging
current and a high electric field for collection.
The three-electrode charging system naturally led into
studies of high electric field-low current density collectors.
The charged particles exiting the pulse charging section could be
effectively collected in a high electric field region. This high
field could be supplied by an electrode system consisting of
strategically located channels with low or negligible corona
current. These channel electrodes were called shoot (chute?)
baffles.
Another significant area of technology development is in the
studies of variations in the corona to collection electrode
spacing. Historically, the electrode spacing was dictated by the
availability of high voltage power supplies. Even after higher
voltage power supplies were developed, the standard nine- to
twelve-inch plate-to-plate spacings were retained. However, there
is no reason to believe that nine- to twelve-inch spacings are
the optimum for every condition of mass loading, particle size
distribution, gas density and particulate resistivity. Therefore,
this research into plate spacing is considered to be timely.
Significant research into the measurement of particulate
characteristics is currently active in Japan. Professor Yoshida
and associates at the University of Osaka have developed an
instrument called an ultramicroscope that is extremely useful for
studying particulate characteristics. The ultramicroscope, used
in conjunction with a television display system, is focused some
distance into a particulate laden gas stream. The behavior of
individual particles within an ensemble of particles can be
evaluated. Many studies involving Brownian diffusion and coagu-
lation, thermophoresis gravitational settling and growth by
condensation are conducted with this instrument.
39
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One development by the industrial concern of Hitachi is also
noteworthy. They have developed an optical particle counter that
is used in conjunction with a proprietary dilution system that is
stated to provide constant dilution ratios for particles up to
about 100 ym in diameter. This instrument can read out in number
per unit volume or mass per unit volume when correctly calibrated.
In general, the state of electrostatic precipitator tech-
nology and particle characteristic measurement technology in
Japan is on a par with the United States. In the areas of pulse
energization and fundamental studies of back corona, their
technology perhaps surpasses that in the United States. The
Japanese investigators welcomed discussion of the U.S. research
efforts equally as we did theirs. A continuation of this inter-
change of information is contemplated.
40
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-600/7-78-110
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Electrostatic Precipitator Technology Assessment:
Visits in Japan, November 1977
5. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Grady B. Nichols
8. PERFORMING ORGANIZATION REPORT NO.
Project 3858-5
9. PERFORMING ORGANIZATION NAME AND AOORESS
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
68-02-2610, W.A. 5
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final: 11/77-4/78
14. SPONSORING AGENCY CODE
EPA/600/13
is.supplementary notes ierl-RTP project officer is James H. Abbott, Mail Drop 61,
919/541-2925.
i6. abstract The report gives results of a particulate control technology assessment
visit to Japan by a team of U.S. investigators. The visit included discussions with
personnel from universities, industries, and other major installations involved with
particulate control. Significant research activities were noted in both the academic
and industrial sectors related to particulate control and measurements. The report
summarizes results of the individual discussions, observations during the tour, and
discussions of technical papers. Many valuable technical papers supplied to the U.S.
team are reproduced in the Appendix of the report, EPA-600/7-78-U0a.
17. KEY WORDS AND DOCUMENT ANALYSIS
a- DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Electrostatic Precipitation
Dust
Measurement
Air Pollution Control
Stationary Sources
Japan
Particulates
13B
13H
11G
14B
¦>3. distribution statement
Unlimited
10. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
46
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
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