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A4-1 A Methodology to Simplify the ESP
Models
Jean Salvi
Abstract
Much work has been carried out on the modeling of electrostatic
precipitators since their development began. A distinction can
be made between two types of approach. A first approach,
influenced by the academic culture, aims to describe all the
physical phenomena that occur during the electrostatic precipitation
process. The second approach, emerging from the problems faced
by the suppliers, focuses on the process as a whole. On the
basis of experimental knowledge, a behavioral law is established to
determine the influence of the main operating parameters on the
efficiency of collection.
The two approaches are not in opposition; they are
complementary. Moreover, several investigations have aimed to
link them, for example, by seeking to justify the Deutsch law on the
basis of physical considerations. The purpose of this article is to
take this method further by plotting theoretical continuity between
the most complex models based on the physics of the process, and the
simplest models covering all these phenomena. This
concentration on the whole of the models makes it possible t set out
the underlying hypotheses accurately according to the degree of
complexity allocated to a given model. It then become possible
to compare these hypotheses with the actual conditions of
application to determine whether the model is pertinent in relation
to the configuration studied.
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A4-2 ESP Modeling From University Studies to
Industrial Application
Veronique Arrondel, Gianluca
Bacchiega, Ivo Gallimberti
Abstract
The need to understand variations in the performance of an
electrostatic precipitator, in order to remain in compliance with
the regulations whatever coal is burned, leads us to place a the
disposal of the operator a user-friendly expert investigation tool
based on a complete description of the phenomena involved during the
dust collection.
The code used, obtained from much work in universities, calculates
the dust collection efficiency per size class, as a function of the
inlet velocity distribution and the ESP operating conditions.
Before this code can be used on any industrial site, two actions
must be taken; the performance of a "blind" validation
test on a 250 MW plant and the reduction of code calculation time to
fulfill the operator's requirements.
To test the code, a one-day test was performed on a recently
renovated ESP. A limited number of data (gas flow rate, inlet
dust concentration and size distribution, ESP geometry, voltage) was
provided to permit the efficiency calculation. The values
calculated by the software were then compared with the values
measured; secondary current intensity, outlet dust concentration and
size distribution. The comparison between the calculations and
measurements shows a difference of less than 15% for the majority of
these variables.
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A4-3 Modeling of Electrode Geometry Effects
on Dust Collection Efficiency of Wire-Plate Electrostatic
Precipitators
D. Brocilo, J.S. Chang
and R.D. Findlay
Abstract
A dust particle collection efficiency model of electrostatic
precipitator was developed. The model includes the electrode
geometry effect through current-voltage characteristics,
volume-averaged electric field and ion density via multi-dimensional
simulation of the electric field and ion density profiles, and the
modified Deutsch dust collection equation. The ion density
distribution was obtained by solving the ion transport equation and
the current continuity equation, including the convective transport
due to the gas flow, transport due to the ion diffusion and ion
drift due to the electric field. Further, diffusion and field
charging are implemented based on the Knudsen number of particular
dust particle diameter for a wide range of dust sizes (10-3
to 102 µm). Smooth round and spiked geometries are
considered as discharge electrodes (DE), as well as the I, U and C
geometries of collecting electrodes (CE). Numerical results
indicate significant improvement of the collection of submicron
particles for the spike-type discharge electrode and the C-type
collecting electrode.
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A4-4 Drift Velocity of Fine Particles
Estimated from Fractional Efficiency Measurements in a
Laboratory-Scale Electrostatic Precipitator
L.M. Dumitran, P. Atten
and D. Blanchard
Abstract
We discuss the evaluation of drift velocity w E
of charged particles in a
laboratory scale electrostatic precipitator having a special
geometry. Estimating the particles drift velocity requires to
control the electric conditions inside the electrostatic
precipitator (electric field of collection, particles charge) as
well as to know "barbed" ionizing electrodes were used
leading to charging of the particles and also to some dust
precipitation. The collection of pre-charged fine particles is
studied in the second section where the electric field is
uniform. Using the model of Leonard et al.
(convection-diffusion equation) the drift velocity of particles is
estimated from measurements of collection efficiency in the second
section of the ESP. This is performed through the
determination of an appropriate value of the turbulent diffusivity
consistent with the estimated drift velocities. Finally, the
influence of gas flow turbulence is discussed.
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A4-5 Correlation Between Current Density,
Dust Layer Structure and Re-Entrainment in a Laboratory ESP
Didier Blanchard, L.M.
Dumitran, Pierre Atten
Abstract
On the basis of visual observations showing that there is a
geometrical pattern for the dust layer deposited in an electrostatic
precipitator, we seek to characterize the physical phenomena leading
to such a deposit. Following experiments of precipitation, we
present here results on the dynamics of the collection, mass flux
and size distribution of the powder depending on the zones of
collection. We finally propose a new possible mechanism for
the layer erosion.
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A4-6 Estimated Operating V-I Curves for Rigid
Frame Discharge Electrodes for Use in ESP Modeling
J.D. McCain
Southern Research Institute
Abstract
Modeling of ESP performance requires that operating voltages and
currents for each section of the precipitator be provided. In
the absence of measured values, estimates are needed for these
values. The original SRI/EPA/EPRI model(s) provided algorithms
for estimating these values when wire-type discharge electrodes of
then typical dimensions were employed. These estimates could
be made through either electrical discharge theory or from a set of
empirical correlations developed by SRI for the Electric Power
Research Institute. This paper describes a means of
extrapolating the EPRI empirical correlations to applications with
rigid frame electrodes. The method of extrapolation is
detailed and comparisons of predicted and measure operating voltage
and currents at a coal-fired utility are presented.
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