Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Reexamination Certificate
1999-08-09
2001-08-14
Mayekar, Kishor (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
Reexamination Certificate
active
06274006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an apparatus and method for treating toxic or hazardous substances, such as NO
x
and SO
x
or the like, contained in exhaust or flue gases of, for example, a thermal (electric) power plant, a garbage burning facility (namely, a refuse incinerating facility), a toxic substance treating facility and a car by using a streamer discharge plasma. More particularly, the present invention relates to a streamer discharge plasma treatment apparatus and method for decomposing and detoxifying nitrogen oxides (hereunder described as NO
x
) and sulfur oxides (hereunder described as SO
x
) contained in exhaust or flue gases of a thermal power plant and so forth. Further, the present invention is applied to the decomposition and detoxification of VOC (namely, Volatile Organic Compound) gases generated in a chemical factory or the like. Furthermore, the present invention relates in general to a pulse generator for use in the aforementioned exhaust gas treating apparatus and method, and more particularly, to a pulse generator which is useful as a power supply in the case that electrodes are placed in gases such as exhaust gases discharged from a thermal power plant or the like, that a (streamer discharge) plasma is then generated by delivering pulse power (or energy) to these electrodes (namely, by applying a pulse voltage across the electrodes) and that toxic substances are treated through electrical action.
2. Description of the Related Art
Hitherto, for instance, what is called an ammonia catalytic reduction method has been employed for decomposing NO
x
. Further, what is called a lime-gypsum method has been employed for decomposing SO
x
. Thus, what is called chemical processing or treatment methods (or processes) have been principal techniques for removing NO
x
and SO
x
, which are contained in exhaust or flue gasses, therefrom.
Meanwhile, in recent years, a streamer discharge plasma exhaust gas treatment method has come to be employed as such a technique. In an apparatus for treating toxic substances contained in exhaust gases by using a streamer discharge plasma, the streamer discharge plasma is generated in a (plasma) reactor chamber. The configurations of, for example, a conventional line-pair cylindrical reactor chamber A and another conventional line-pair flat-plate-like reactor chamber B are illustrated in
FIGS. 15 and 16
, respectively. Streamer discharge plasmas are generated in the reactor chambers A and B by applying (same) high voltages V
0
across a line electrode
01
and a cylindrical electrode
02
of FIG.
15
and across a line electrode
06
and a plate electrode
08
of
FIG. 16
, respectively.
Electrons originated (or drawn) from a streamer discharge plasma are accelerated by an electric field, so that these electrons become high-energy ones. The high-energy electrons contained in the streamer discharge plasma decompose and detoxify toxic substances, such as NO
x
and SO
x
, which are contained in exhaust gases, by colliding with the toxic substances. For instance, in the case of decomposing NO
x
such high-energy electrons collide with NO and N
2
to thereby induce the following reaction: NO+N→N
2
+O. Thus, NO is decomposed.
Radical density contributing to the decomposition of NO is determined by energy cast or applied to the streamer discharge plasma. Moreover, the reaction rate of a reaction component of a reaction system is also determined (incidentally, note that the treatment rate of NO is physically determined when the radical density is determined).
In the conventional method or system, one high-capacity high-voltage power supply and one high-capacity reactor chamber are used so as to generate a streamer discharge plasma. Incidentally, in
FIGS. 15 and 16
, reference characters
04
,
05
,
010
and
011
designate electric current introduction lines.
However, in the case of a reactor, which has one high-voltage power supply and one reactor chamber as illustrated in
FIGS. 15
or
16
, constant energy is cast into the entire reactor chamber, regardless of the concentration of the toxic substance. Thus, there is caused an excessive waste of energy in a region, in which the concentration of the toxic substance is low, in an outlet of the reactor chamber. Consequently, the energy required for the treatment is increased. Namely, when the concentration of the toxic substance is lowered to a target value in a reactor chamber, energy of the amount, which is not less than the necessary amount of energy, is consumed in the region in which the concentration thereof is low.
Further, as compared with the conventional chemical processing or treatment methods, the conventional streamer discharge plasma exhaust gas treatment method has large merit in that the facility therefor is in-expensive and that a space required to install the facility is small. The conventional streamer discharge plasma exhaust gas treatment method has large demerit in that the energy consumption required for generating a streamer discharge plasma is about 10 Wh/Nm
3
and is thus a little under two times that (namely, about 6 Wh/Nm
3
) required in the case of the conventional chemical processing or treatment method.
Meanwhile, a pulse generator for generating large voltage pulses has been used as a power supply for use in an apparatus for performing the streamer discharge plasma exhaust gas treatment method.
FIG. 17
is a diagram conceptually illustrating the configuration of a conventional pulse generator of the distributed constant (or parameter) type that uses coaxial cables. In this figure, reference characters
1
-1
and
1
-2
denote distributed constant (or parameter) lines (namely, transmission lines);
3
a high-voltage side wiring line (or wire);
4
a low-voltage side wiring line; V
0
a D.C. charger; S
1
a shortcircuit switch; V
1-1
and V
1-2
voltages generated in the direction of arrows corresponding to the distributed constant lines
1
-1
and
1
-2
respectively; Z a load; and V
p
voltage applied to the load Z.
The distributed constant lines
1
-1
and
1
-2
are coaxial cables, whose characteristic impedances are Z
1a
and Z
1b
, respectively, and whose lengths are L. Further, each of the distributed constant lines
1
-1
and
1
-2
is composed of: a corresponding one of cores (or core lines)
1
-1a
and
1
-2a
; and a corresponding one of outer conductors (made of shield braid or cladding materials or the like)
1
-1b
and
1
-2b
which surround the cores
1
-1a
and
1
-2a
through insulating materials (not shown), respectively. Incidentally, a folding-back point or portion is constituted only by the cores
1
-1a
and
1
-2a
that are not sheathed. These cores
1
-1a
and
1
-2a
are connected in series with each other. Further, an end (namely, an input-side portion) of these cores is connected to the D.C. charger V
0
through the high-voltage side wiring line
3
. On the other hand, the outer conductors
1
-1b
and
1
-2b
are connected to each other by a shortcircuit line
5
-1
at the side of the shortcircuit switch s
1
(namely, at the input-side terminal or end portion) and is thus shortcircuited. Moreover, the input-side terminal portion of the outer conductor
1
-1b
is connected to a grounding or earthing line serving as the low-voltage side wiring line
4
. Furthermore, the input-side terminal portion of the outer conductor
1
-2b
is connected to the high-voltage side wiring line
3
through the shortcircuit switch S
1
.
In this case, the impedance of the D.C. charger V
0
acting as a power supply is matched to that of the load Z. Namely, Z=Z
1a
+Z
1b
.
Furthermore, in the case that the characteristic impedances of the distributed constant lines
1
-1
and
1
-2
are equal to each other, namely, in the case that the very same distributed constant lines
1
-1
and
1
-2
are used, the (voltage) propagation velocities of voltage signals in these distributed constant lines
1
-1
and
1
-2
are equal to each other. In the case where the dielectric c
Kawamura Keisuke
Murata Masayoshi
Shigemizu Tetsuro
Yoshida Hirohisa
Foley & Lardner
Mayekar Kishor
Mitsubishi Heavy Industries Ltd.
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