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FP11 In-situ
Measurement of Local Particle Fluxes in a Laboratory-scaled ESP
Hans-Joachim
Schmid and Heinz Umhauer
Insititute of Mechanical Process Engineering and Mechanics
University of Karlsruhe
Abstract
An earlier investigation on grade efficiencies of ESP’s
yielded significantly higher separation efficiencies for small
particles with a diameter of less than 2 µm than predicted by any
model. Therefore,
several experiments were conducted in a lab-scaled type model
precipitator with flat plates and smooth wires with monodisperse 1
µm particles to verify and understand this phenomenon:
An optical in-situ measurement yields local particle flux
profiles. By integrating
these profiles balances for several small parts of the precipitator
can be made giving deeper insight in local particle precipitation.
Furthermore particle change measurements for an aerosol
sample directly from the precipitator channel were done.
The flux profiles show the development of a
concentration profile along the duct which gets steeper towards the
wall. These profiles are
very similar, if for different operating parameters the Duetsch-number
is kept constant. On the
other hand the local balances always show a much higher separation
efficiency that predicted the Deutsch theory and partly even higher
than predicted by laminar flow mode.
The charge measurements yielded significantly higher
particles charges than predicted by common charge models
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FP12 Influence
of Dust Particles on V-I Characteristics in an Electrostatic
Precipitator
Joon-Ho Ko, Dong-Goo Kang,
Hyoung-Kuen Park and Cha-Seok Mun
Energy & Environment Research Department
Hyundai Industrial Research Institute
Hyundai Heavy Industries, Co. Ltd.
Cheonha-don, Dong-ku Ulsan, Republic of Korea
Abstract
A new model was developed in the wire-plate type electrostatic
precipitators (ESPs) for estimating the electric performance in the
presence of dust particles. To
solve corona current distribution in diverging field, two
interactive methods were used. In
small particles, the turbulent flow interaction has an influence on
the removal efficiency by the diffusion force.
Accordingly higher particulate space charge gave strong
suppression of corona due to the inhibition of ion’s flow from
wire to plate. It
reduced the average corona current and the collection efficiency in
the electrostatic precipitator.
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FP13
A
Preliminary Study on the Adhesive Forces of Precipitated Dust Layer
Tang Minkang and Chen Guofang
Department of Construction Engineeering Southern Institute of
Metallurgy
Abstract
The mechanical properties of precipitated dust layer on the
collection electrode in ESP have a direct effect on rapping and
removing dust layer. The
properties and their effect are discussed in detail in electrostatic
forces produced by dust particles which carry free charges or by
polarizing dust particles or by contacting closely between particles
or between particles and the collection surface of the electrode.
The results indicate when dust particles
carrying free charge reach the collection electrode the direction of
the electrostatic forces acted on the particles point towards the
electrode and this direction can be changed with the time.
The resistivity of particles is on of effecting factors for
this change. The
polarizing electrostatic force produced by fetter charge makes the
dust particle arrange along the lines of the electric field and
closely agglomerate together. The
contacting electrostatic force between particles has a significant
effect on rapping and removing dust from the plate, and the one
between particles and collecting plate take advantage of
agglomeration and collection of the particle.
To change work function of the contacting materials is an
important way to improve result of rapping and removing dust layer.
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FP14
A
Preliminary Study on the Adhesive Forces of Precipitated Dust Layer
Yuan Yongtao and Zhao Yi
environmental Engineering Department
Abstract
The dielectric properties of Li, K and Na et al in FA were
verified by many experiments. The
clear and identical conclusions of electrical conduction for Fe and
C have had been obtained. It
is found by tests in this paper that the electrical conduction of
carbon not only depends on the total content of carbon, but also
more depends on the coalification. The electrical conduction of high
coalification carbon particles is greatly different from that of low
coalification carbon particles; the electrical conduction of Fe
depends on its speciation. The
specific resistivity and the field strength of electrical breakdown
were affected by FecO4 greatly, and by F32O3
slightly. The initial
theory analysis for the conclusions of the above two test is done in
the paper.
The
dielectric properties are shown using the specific resistivity and
the field strength of electrical breakdown.
The study of dielectric properties of FA has a special
significance in the field of electrostatic precipitation.
The dielectric properties of FA depend on both outside
conditions (flue gas parameter) and inside factors (chemical
component of FA). The
charge conduction of Na2O, LiO and K2O et al
in FA has been verified by some experiments.
But the experimental study on the components of iron and
carbon is very little, and the results are relative different, even
the some viewpoints are opposite.
In this paper, the investigation of the dielectric properties
of iron and carbon in FA was carried out by experiment, and some
advances were obtained.
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FP15
An Experimental Study of Electrostatic Precipitator Plate Rapping
and
Reentrainment
Jae-Keun Lee, Jae-Hyun
Ku, Jung-Eun Lee, Seong-Chan Kim, You-Chull Ahn, Jin-Hyouk Shin, and
Seok-Heui Choung
School of Mechanical Engineering
Abstract
An electrostatic precipitator is useful for the removal of the
particulate emissions from industrial power plants.
However, few research papers related to the rapping process
to separate fly ash from the collecting plates have been published.
In this research, the physical, chemical, and electrical
characteristics of fly ash generated from coal fired power plants
were analyzed using a particle counter, a filter sampler, a scanning
electron microscope, and a resistivity meter.
The evaluation of the rapping process and reentrainment in a
laboratory scale electrostatic precipitator is performed using a
plate rapping system, an ash feeder, and a power supply.
The principal ingredients of fly ash used at present in the
coal fired power plant were SiO2(65.5%), Al2O3(24.0%),
and Fe2O3(5.0%).
The mass median diameter was measured about 20 ~ 30 µm.
Fly ash resistivity at 150OC was measured of 1010
Ω cm and it was expected that the collection efficiency might
decrease due to back-corona phenomena.
The rapping efficiency was found to increase with increasing
the thickness of ash layer and rapping acceleration.
Also the rapping efficiency at power-off in a discharger was
higher than that at power-on. The
ash size of reentrainment at
rapping were smaller than that of the fly ash supplied.
The optimal rapping condition was found to be 3.5mm thick in
fly ash layer deposited in the collecting plates.
Therefore, collection efficiency, rapping efficiency, and
reentrainment to design the high efficiency electrostatic
precipitator should be considered.
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