JP2001314751A - Plasma reaction vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a reaction vessel compact and simultaneously to improve reaction efficiency by uniformizing the flow velocity distribution of a gas passing in the vessel. SOLUTION: This plasma reaction vessel is provided with the first metallic flat-plate electrode 11A and second metallic flat-plate electrode 11B opposed to each other, a dielectric 12 interposed between the electrodes 11A and 11B and a means for imparting a potential difference between the electrodes 11A and 11B, and a high voltage is impressed between the electrodes 11A and 11B to plasma-decompose the introduced gas 15 in the region 16 between the electrodes 11A and 11B. The electrodes 11A and 11B and dielectric 12 are formed into a doughnut-shaped disk, respectively, and placed on one another, and a gas passage is provided inside and outside the gap between the electrodes 11A and 11B, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma reactor for reforming a gas by a plasma treatment with high efficiency.

[0002]

2. Description of the Related Art Conventionally, polluting gases in the environment (for example, N
_Ox , VOC (volatile organic compound, Volatile
As a method of purifying harmful substances such as organic compounds and ethylene, for example, a gas plasma decomposition treatment method using discharge (silent discharge, barrier discharge) is known.

Hereinafter, this conventional gas plasma processing method will be described.

FIG. 9 is a block diagram of a tubular gas reactor according to the prior art.

[0005] As shown in FIG. 9, a conventional tubular gas reactor comprises a cylindrical dielectric 02 formed by coating an inner surface of a metal outer cylindrical electrode 01 and a cylindrical dielectric 02. It comprises a central electrode 03 arranged substantially coaxially with the axis, and a high-voltage power supply 04 for applying a high voltage between the electrodes 01 and 03. An AC high voltage is applied between the electrodes 01 and 03. The plasma discharge is generated in a state where the voltage is applied and the dielectric 03 is interposed between the poles. According to this device, the electrodes 01,
A ring-shaped discharge is generated by applying an AC high voltage from a high-voltage power supply 04 during the period 03, and a gas 06 to be decomposed is supplied to the discharge space 05 to perform a plasma decomposition process.

FIG. 10 is a block diagram of a parallel plate type gas reactor which is another plasma decomposition processing technique.

As shown in FIG. 10, the conventional parallel plate type gas reaction apparatus has opposed flat plate electrodes 07A and 07 made of metal.
B, a dielectric 08 disposed on the surface of one of the electrodes (lower side in the figure) 07B, and a high-voltage power supply 04 for applying a high voltage between the electrodes 07A and 07B. Plasma discharge is generated by applying an AC high voltage. In this device, a high-voltage power supply 0 is connected between the electrodes 07A and 07B.
By applying an AC high voltage from 4, a discharge uniformly spread in a flat plate shape is generated, and a gas 06 to be decomposed is supplied to the discharge space 05, whereby plasma decomposition processing is performed.

By utilizing the silent discharge and the barrier discharge in which the dielectric is inserted between the electrodes as described above, the discharge volume can be increased even under a relatively high gas pressure near the atmospheric pressure. Increases the probability of
Gas reaction (decomposition) can be performed efficiently.

[0009]

However, in the conventional tubular reactor shown in FIG. 9, it is difficult to reduce the size of the reaction vessel when processing a larger flow rate of gas. There is.

That is, in a reaction vessel in which a gas reaction is performed by utilizing discharge, it is necessary to increase the plasma volume in accordance with an increase in the flow rate of the processing gas. However, in a tubular reactor as shown in FIG. Considering the case of enlarging the diameter of the container, it is necessary to generate a discharge at a voltage of about several kilovolts that is generally feasible under gas pressure near atmospheric pressure.
The discharge interval needs to be about several millimeters, and the diameter of the center electrode needs to be increased as the diameter of the cylindrical dielectric increases. As a result, the ratio of the discharge volume in the reaction vessel is reduced, and there is a problem that the volume of the reaction vessel itself becomes larger than the discharge volume.

When considering increasing the length of the reaction vessel, it is necessary to bend the reaction vessel itself in order to make the reaction vessel compact, but this is difficult in terms of production technology. At the same time, there is a problem that the manufacturing cost for that purpose increases separately.

On the other hand, in a parallel plate type reaction vessel, it is easy to make the reaction vessel compact by a technique such as forming electrodes in a laminated structure, but as shown in FIG. 11, the reaction vessel passes through the inside of the reaction vessel. Since the flow velocity distribution of the gas 06 is different between the vicinity of the electrode in the discharge space and the central part,
There is a problem that the flow velocity distribution becomes non-uniform. As a result,
There is a problem that the residence time of the gas in the plasma at the high flow velocity portion (center of the space) becomes short, and a highly efficient reaction cannot be performed.

In view of such circumstances, it is an object of the present invention to provide a plasma reaction vessel which realizes a compact reaction vessel and has a uniform flow velocity distribution of a gas passing through the reaction vessel.

[0014]

According to a first aspect of the present invention, there is provided a first plate type electrode and a second plate type electrode which are opposed to each other, and a first plate type electrode and a second plate type electrode which are opposed to each other. And a potential difference applying means for applying a potential difference between the first and second electrodes, and a high voltage is applied between the first and second electrodes for introduction. In a plasma reaction vessel for decomposing gas in a plasma decomposition region between electrodes, the first and second electrodes and a dielectric material are stacked in a donut disk shape, and the first and second donut disk shapes are stacked and arranged. A gas flow path that is respectively circulated on the inner peripheral side and the outer peripheral side of the gap between the electrodes.

According to a second aspect of the present invention, in the first aspect, at least one of the inner peripheral side and the outer peripheral side of the first electrode, the dielectric, and the second electrode is a gas-permeable inner cylinder. Alternatively, the plasma reaction container is supported by an outer cylinder.

According to a third aspect of the present invention, in the first or second aspect, the dielectric-interposed pole is defined as one unit,
A plasma reaction vessel comprising a plurality of the units laminated.

According to a fourth aspect of the present invention, there is provided a plasma reaction vessel according to the third aspect, wherein one of the first electrode and the second electrode is shared between adjacent units. .

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a plurality of convex portions are formed on both surfaces or any one of the surfaces of the dielectric. In the reaction vessel.

According to a sixth aspect of the present invention, in the fifth aspect, the planar shape of the convex portion formed on the surface of the dielectric is any one of a rhombus, a polygon, a circle, an ellipse, and an ellipse. A plasma reaction vessel characterized in that:

According to a seventh aspect of the present invention, there is provided a plasma reaction vessel according to the sixth aspect, wherein a part of a convex portion formed on the surface of the dielectric is lowered.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(First Embodiment) FIG. 1 shows a schematic view of a gas reactor according to the present embodiment. FIG. 2 shows the II-
FIG. 2 is a sectional view taken along line II.

As shown in these drawings, the gas reactor according to the present embodiment has a donut disk-shaped opposed first metal flat plate-shaped electrode (hereinafter, also simply referred to as an electrode) 11A.
And a second metal plate electrode (hereinafter, also simply referred to as an electrode)
11B, a donut disk-shaped dielectric 12 covering the surface of the second metal plate electrode 11B, and a second metal plate-shaped dielectric 11A covered with the first metal plate electrode 11A. The inner cylindrical insulating tube 13 and the outer cylindrical insulating tube 14 are each formed of a gas-permeable double tube in which the inside and outside of the donut disk of the metal flat electrode 11B are fitted. And is housed inside the container body 10.
A plasma discharge is generated between the electrodes 11A and 11B by applying an AC voltage from a power supply unit (not shown), and the gas 15 introduced from the inner cylindrical insulating tube 13 is discharged.
The plasma processing is performed in the discharge space 16 to reform the gas, and the reformed gas 17 is discharged. The inner cylindrical insulating tube 13 includes the electrodes 11A and 11B and the dielectric 12
It is provided for holding and fixing.

The upper end of the inner tubular insulating tube 13 is closed by a closing member 18, and the gas 15 introduced by the gas introducing tube 19 is supplied to the electrode 11 A through the pores of the inner tubular insulating tube 13. , 11B, and reacts while passing through the plasma from the center to the outside to reform the gas.

The reformed reformed gas 17 is discharged outside through the pores of the outer cylindrical insulating tube 14.

The material of the outer cylindrical insulating tube 14 may be made of ceramics having an infinite number of pores. Alternatively, pores or partial openings for facilitating gas permeation may be provided. In this case, the outer cylindrical insulating tube 14 is not necessarily required to be provided.

The gas 15 may be introduced from the outside instead of from the inside.

As described above, the expansion of the discharge volume in order to cope with an increase in the flow rate of the processing gas is also achieved by the donut-shaped electrode 11.
By increasing the diameters of A and 11B, it is possible to easily cope with the problem.

The first electrode 11A having a donut disk shape is also provided.
And the second electrode 11B and the dielectric 12 inserted between the electrodes
And a single unit, and by stacking a plurality of such units as one unit, a desired volume can be easily secured.

In addition, the flow velocity distribution of the gas passing through the discharge becomes a uniform gas flow from the center to the outer periphery, and the gas flow is made uniform, so that the efficiency of the gas decomposition reaction can be greatly improved. .

(Second Embodiment) FIG. 3A shows a schematic view of a gas reactor according to the present embodiment, and FIG. 3B shows the state of electric wiring. FIG. 4A shows the IV-
FIG. 4 is a sectional view taken along line IV. FIG. 4B is a cross-sectional view taken along the line IV-IV when the convex portion is a rhombus.

As shown in FIGS. 3A and 4A, the gas reactor according to the present embodiment has first and second gas reactors.
The basic configuration is the same as that of the first embodiment except that two units each composed of an electrode and a dielectric are laminated, and thus the same reference numerals are given and the description of the members is omitted.

That is, the second electrode 1 in the form of a donut disk
A first electrode 11A is arranged on each side of 1B, and a dielectric 12 is arranged between the first electrodes 11A. The dielectric 12 has a plurality of hemispherical convex portions 20 on the surfaces on both sides, and is arranged in a non-contact state with the first and second electrodes 11A and 11B. As described above, in the present embodiment, one electrode is shared by two units, a high voltage is applied to each of the first electrodes 11A, and the shared second electrode 11B is set to GND.

According to this embodiment, the presence of the plurality of protrusions 20 independent of each other allows the introduced gas molecules to flow between the protrusions 20 while branching and merging.
The frequency of collisions increases, whereby the reaction efficiency can be improved.

If it is not necessary to form the convex portions 20 on both sides, they may be formed on only one side.

The shape of the convex portion 20 is not limited to a hemispherical shape as in the present embodiment, but may be a shape that can increase the frequency of gas collision, for example, a polygonal shape,
Any shape such as a circular shape, an elliptical shape, and an elliptical shape may be used.

Further, the convex portions 20 may be brought into contact with the electrodes. In this case, gas flows between the convex portions 20. FIG. 5 shows a gas flow path when the convex portion 20 has a hemispherical shape.

(Third Embodiment) FIG. 6 is a schematic view of a main part of a gas reactor according to the present embodiment.

As shown in FIG. 6, in the gas reactor according to the present embodiment, the height of the convex portion 20 formed on the surface of the dielectric 12 according to the second embodiment is partially reduced. The first metal flat electrode 1
It is also possible to partially form a strong electric field portion between the first and second electrodes 1A to generate a local discharge and generate a composite barrier discharge together with a silent discharge.

As described above, according to the present embodiment, by providing the plurality of convex portions 20 with the convex portions 21 partially lower in height, the mist-like barrier discharge and the lightning-like local concentrated discharge can be prevented. A composite barrier discharge is enabled, the plasma energy level is improved, and the frequency of collision of the introduced gas molecules due to the presence of gas decomposition is increased, thereby improving the gas reaction efficiency.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

Example 1 CO ₂ decomposition tests were carried out using the following various plasma reaction vessels (1) to (4).

The conditions for decomposing CO ₂ gas according to this embodiment are shown below. Gas composition: CO ₂ (10%) + O ₂ (10%) / N ₂
(Balance) ・ Gas flow rate: 500 cc / min ・ Target reaction: CO ₂ decomposition reaction (CO ₂ → CO + 1 / 2O)
₂ ) ・ Reactor type

(1) Tubular reaction vessel Central electrode: diameter 40 mm × length 160 mm Reaction vessel volume: 286 cc

(2) Laminated parallel plate type reaction vessel Electrode dimensions: 50 mm × 150 mm Electrode unit: 6-stage configuration Reaction vessel volume: 286 cc

(3) Donut disk stack type reaction vessel (dielectric: smooth surface) Electrode outer diameter: 100 mm Electrode inner diameter: 30 mm Electrode unit: 6-stage configuration Reaction vessel volume: 283 cc

(4) Donut disk stack type reaction vessel (dielectric: with convex portion) Electrode outer diameter: 100 mm Electrode inner diameter: 30 mm Electrode unit: 6-stage configuration Reactor container volume: 283 cc Dielectric convex portion: Φ3 mm 48 places

The test results of this example are shown in Table 1 and FIG.

[0049]

[Table 1]

As shown in Table 1 and FIG. 7, the reaction rate of the tubular reaction vessel according to the prior art (1) was low because the discharge volume was small. Further, in the flat plate type reaction vessel according to the prior art (2), although the discharge volume was sufficiently ensured, the residence time of some gases in plasma was short, and the reaction rate was low.

On the other hand, the donut disk-stacked reaction vessels (3) and (4) of the present invention exhibited a higher reaction rate than the vessel (2), despite the smaller discharge volume.

[0052] using a variety of plasma reactor (Example 2) from above (1) (4) was subjected to decomposition test of NO _x.

The conditions for decomposing NO _x gas according to this embodiment are shown below. Gas _{composition: NO (500ppm) + O 2} (10%) /
N ₂ (balance) Gas flow rate: 500 cc / min Power supply: voltage (3.2 kVp), frequency (10 kHz)
z), waveform (rectangular wave)

The test results of this example are shown in Table 2 and FIG.

[0055]

[Table 2]

As shown in Table 2 and FIG. 8, the reaction rate of the tubular reaction vessel (1) was low because the discharge volume was small. In addition, the flat plate type reaction vessel of (2) has a sufficient discharge volume, but has a higher decomposition efficiency than the vessel of (1), but has a short residence time in plasma in a part of the gas, and has a high reaction rate. Was low.

On the other hand, the donut disk-stacked reaction vessels (3) and (4) according to the present invention exhibited a high reaction rate even though the discharge volume was smaller than that of the vessel (2).

[0058]

According to the present invention, since a donut disk-shaped electrode is used, the gas decomposition efficiency can be improved without increasing the discharge volume, and high-efficiency gas reforming becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a plasma reaction vessel according to a first embodiment.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a schematic view of a plasma reactor according to a second embodiment.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a gas flow path in a reaction vessel according to a second embodiment.

FIG. 6 is a schematic view of a plasma reactor according to a third embodiment.

FIG. 7 is a comparison diagram of a CO ₂ reaction rate according to Example 1.

FIG. 8 is a comparison diagram of a NO _x reaction rate according to Example 2.

FIG. 9 is a schematic view of a tubular reaction vessel according to the prior art.

FIG. 10 is a schematic view of a parallel plate type reaction vessel according to the prior art.

FIG. 11 is a schematic diagram of a distribution of a gas flow velocity in a parallel plate type reaction vessel according to the prior art.

[Explanation of symbols]

 Reference Signs List 11A First metal flat electrode 11B Second metal flat electrode 12 Dielectric 13 Inner cylindrical insulating tube 14 Outer cylindrical insulating tube 15 Gas 16 Discharge space 17 Modified gas 18 Closure member 19 Gas Inlet tube 20 Convex part 21 Convex part (low)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Fujishiro 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Inventor Kenji Dosaka 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Minoru Torii 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Kazuo Ando 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Inventor Koji Kotani 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. 4G075 AA03 BA01 BA05 CA47 EB42 EC21 FA05 FC15

Claims (7)

[Claims] A first plate-type electrode and a second plate-type electrode opposed to each other, a dielectric interposed between the first and second electrodes, and a first electrode between the first and second electrodes. And a potential difference applying means for applying a potential difference to the first and second portions.
In a plasma reaction vessel for decomposing a gas introduced by applying a high voltage between the electrodes in a plasma decomposition region between the electrodes, the first and second electrodes and a dielectric are arranged in a donut disc shape and stacked and arranged. A gas flow path which is provided on the inner peripheral side and the outer peripheral side of the gap between the donut-shaped first and second electrodes, respectively. 2. The method according to claim 1, wherein at least one of an inner peripheral side and an outer peripheral side of the first electrode, the dielectric, and the second electrode is supported by a gas-permeable inner cylinder or an outer cylinder. A plasma reactor. 3. The plasma reaction vessel according to claim 1, wherein the first and second electrodes having the dielectric interposed therebetween constitute one unit, and a plurality of the units are stacked. 4. The plasma reactor according to claim 3, wherein one of the first electrode and the second electrode is shared between adjacent units. 5. The plasma reaction vessel according to claim 1, wherein a plurality of convex portions are formed on both surfaces or one of the surfaces of the dielectric. 6. The method according to claim 5, wherein the planar shape of the convex portion formed on the surface of the dielectric is a rhombus, a polygon, a circle, an ellipse,
A plasma reaction vessel having any one of elliptical shapes. 7. The plasma reaction vessel according to claim 6, wherein a part of the convex portion formed on the surface of the dielectric is lowered.