PP16
Studies of SO2 Conversion in Discharge with a Dielectric Barrier at
an Alternating Polarity Form
of the Impulse Voltage
V.I. Perevodchikov, V.A. Fedorov,, E.F. Prozorov,
K.N. Uljanov
The Russian Federation State Centre
Abstract
Efficiency of SO2 conversion in a stream of mixture
of SO2 with air was studied experimentally.
A discharge was provoked in a reactor composing of
dielectric-covered metallic plates with metallic strings stretched
between them. Reactor
was applied with a 100 Hz alternating polarity impulse voltage.
Each impulse was a non-symmetric voltage wave including a
number of positive and negative semiwaves.
A discharge was excited at the first positive voltage
semiwave. Burning of the
discharge occurred for two subsequest semiwaves.
During the first negative and the second positive semiwaves
an alternating polarity current was practically in phase with the
voltage. Energy
contribution into discharge took place at the first positive, the
first negative and the second positive semiwaves.
Current and voltage oscillograms were recorded.
Gas stream parameters (velocity, temperature, mixture
composition before and after action) were controlled SO2
content was charged from 150 to 750 ppm, maximum specific energy
contribution attained 16 Wh/nm3.
Experimental studies showed conversion of SO2 to
95% of the initial concentration and determined efficiency of the
conversion as a function of energy contribution and initial
concentration of SO2.
With this method of discharge excitation the presence of a
dielectric barrier on one of the electrodes and capability of
changing the envelope of the voltage impulse and number of positive
and negative semiwaves permit to obtain additional means of
improvement of the conversion efficiency. The implemented
experiments indicate prospects of the given method of SO2
conversion to get a required concentration of SO3
to carry out gas conditioning prior to the electric precipitator.
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PP17
Non-thermal Plasma Processing of Flue Gas with Catalytic
Reactions and Water Vapor
Kazuo Shimizu, Toshiyuki
Hirano, and Tetsuji Oda
Department of Electrical Engineering, The University of Tokyo
Abstract
NOx removal enhancement from flue gas by using non-thermal plasma
processing combined with a catalyst was studied.
Catalysts tested in this paper were copper-coated zeolite,
conventional 3-way catalysts. The
combined process of the catalyst reactor and the non-thermal plasma
reactor was examined experimentally.
Water vapor from 5 to 15% was added in the flue gas to
simulate real exhaust gas condition.
With 5% of water vapor, the best removal rate
of about 80% was obtained with Na-ZSM-5 catalyst at 200-300oC
without non-thermal plasma. Combined
with non-thermal plasma and water vapor improves NOx removal rate
with NA-ZSM-5 at higher temperature.
Such high removal rate was caused by chemical reactions and
absorption by the catalyst. While
non-thermal plasma degrades NOx removal rate with Cu-ZSM-5, when the
gas temperature of 300oC or above.
When the gas temperature was 100oC, the
non-thermal plasma process is enhanced by the combination of
non-thermal plasma and catalyst.
The catalyst does not work at such low temperature.
Gas temperature of around 300 or 400oC,
3-way catalyst does not require non-thermal plasma to remove about
70% of NO.
Absorption characteristics was also
investigated and only Na-ZSM-5 showed higher absorption
characteristics compared to that of Cu-ZSM-5 or 3-way catalyst.
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PP18
Dynamic
Behavior of the Corona Discharge in Air
Sung-Taek Chun
Division of Physics, Eulji Medical College
Jong-Sik Kim and Gon-Ho Kim
Department of Physics, Hanyang University
Abstract
The spatial and temporal behavior of pulsed corona discharge
produced in a coaxial wire-cylinder type reactor has been
investigated theoretically. The
model plasma is produced at atmospheric pressure by applying high
voltage pulses to a thin center wire of the reactor.
A self-consistent one dimensional fluid model is used to
analyze the formation and evolution of the corona; the ion and
electron densities, the potential profiles in the discharge region
in the reactor are obtained, and the characteristics of the
propagation of ionization front are analyzed.
It has been shown that the non-neutral space charges produced
by the opposite movements of ions and electrons can induce electric
field sufficient to cancel the externally applied electric field
inside the bulk discharge region. The dynamics of electrons near the
ionization front modifies the electric field, and it is shown to be
responsible for the propagation of the ionization front.
The numerical study indicates that the characteristics of the
discharge plasma depends strongly on the characteristics of input
voltage pulses and the reactor geometry.
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PP19
Negative Ion Chemistry of Air Cleaning Coaxial Wire-Tube
Electrostatic Precipitators
J.S. Chang and A.L.C. Kwan
Department of Engineering Physics
McMaster University
Abstract
In this work, a negative dc corona discharge chemistry in a coaxial
wire-tube electrostatic precipitator is numerically simulated. The
purpose of this work is to try to gain a better fundamental
understanding of the corona discharge chemical process.
In this model, the continuity equations and the charged (or
neutral) particle transport equations are solved simultaneously with
the Poisson’s equations. One
hundred and ninety-five chemical reactions for 38 different chemical
species are included. These
species can be divided into three groups.
The first group is the negative ions which include O-,
O2-, O3-, O4-,
NO-, NO2-, NO3-,
N2O2-, and N2O3-.
The second group is the neutral species which include O, O2,
O3, N, N2, NO, NO2, N2O,
NO3, N2O4, and N2O5.
The third group is the positive ions which include O+,
O2+, O4+, O6+,
N+ N2+, N3+,
N4+, NO+, NO2+,
NO3+, NO4+, N2O+,
N2O2+, N2O3+,
N2O4+, N3O+
and N4O2+.
The simulation results show that the concentrations of
neutral radicals and ions (both positive and negative) increase with
increasing applied voltage. In
all the simulations, the negative ion with the highest concentration
is N2O2-, while the radical with
the highest concentration is N2O.
For the positive ion, the species with the highest
concentration is N3O+ at the lower applied voltage and N2O3+
at the higher applied voltage.
Also several toxic byproducts like O3, NO, NO2,
N2O4, and N2O5 are
observed in the simulation results.
However, their maximum computed concentrations are within the
acceptable limits.
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