JPH08321397A - Atmospheric plasma generator and atmospheric plasma generation method using the generator - Google Patents

Abstract

PURPOSE: To provide an atmospheric plasma generator as well as an atmospheric plasma generation method, having the capability of generating a homogeneous glow discharge under the application of extremely small power even when such gases as air, nitrogen and oxygen are used, and ensuring high energy efficiency as well as high reaction efficiency. CONSTITUTION: This atmospheric plasma generator has an electrode pair 1 formed out of an electrode 1a connected to an AC power supply 5 and an earth electrode 1b, and AC electrical field is applied across the pair 1 in the presence of gases to generate a glow discharge plasma under the atmospheric pressure. Regarding the generator so formed, the gap of the electrode pair 1 is filled with particle type materials 4 made of a conductor covered with an insulator all around. In this case, the conductor 4 is metal and the insulator is an inorganic dielectric substance. Also, the electrode pair 1 is a metallic net. Furthermore, AC electrical field is applied across the pair 1 in the presence of gases, using the generator, thereby generating a glow discharge plasma under the atmospheric pressure. Also, the gases are mainly composed of the air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric pressure plasma generating apparatus capable of generating a stable glow discharge even in air under atmospheric pressure and an atmospheric pressure plasma generating method using the apparatus.

[0002]

2. Description of the Related Art Conventionally, many methods for generating electric discharge under atmospheric pressure have been developed. For example, a corona treatment device, an silent discharge, an ozonizer by creeping discharge, and the like can be used.
Corona discharge is generated by causing a local dielectric breakdown of gas when a high DC voltage is applied with a sharp discharge electrode and a smooth electrode facing each other and the gas is turned into plasma. This is a streamer-like state in which a portion having a very high current density and a portion in which no discharge occurs are mixed in the gas. In addition, creeping discharge is an extremely partial discharge, in which an electrode is formed on the surface of an inorganic material such as ceramics and an internal electrode is applied to generate a discharge on the surface of the ceramic. As disclosed in Japanese Patent Laid-Open No. 63-50478, a method of generating a glow discharge that is a uniform discharge under atmospheric pressure has been developed in recent years, but an expensive gas such as helium or argon is required. There was a drawback. Further, JP-A-5-155605 or JP-A-6-155605
As disclosed in Japanese Patent Laid-Open No. 119995, there is a method of generating a glow discharge of air, nitrogen, etc. by devising an electrode, but the discharge space is extremely small and there is a problem in stabilizing the discharge. Although a method of generating a strong partial discharge by filling a dielectric ceramic between wire mesh electrodes and applying an alternating electric field has been reported, an extremely high applied voltage is required due to the need to fill an inorganic material. There was a problem of doing.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to achieve a uniform glow discharge even when a gas such as air, nitrogen or oxygen is used. An object of the present invention is to provide an atmospheric pressure plasma generation apparatus that can be generated with a small applied power and is excellent in energy efficiency and reaction efficiency, and an atmospheric pressure plasma generation method using the apparatus.

[0004]

An atmospheric pressure plasma generator according to claim 1 of the present invention is provided with an electrode pair 1 consisting of an electrode 1a connected to an AC power source 5 and a ground electrode 1b, and the presence of gas. Below, by applying an alternating electric field between the electrode pair 1,
An atmospheric pressure plasma generator for generating glow discharge plasma under atmospheric pressure is characterized in that a space between the electrode pair 1 is filled with a granular body 4 formed by covering an entire surface of a conductor 2 with an insulator 3. .

The atmospheric pressure plasma generator according to a second aspect of the present invention is characterized in that the conductor 2 is a metal and the insulator 3 is an inorganic dielectric.

An atmospheric pressure plasma generator according to a third aspect of the present invention is characterized in that the electrode pair 1 is a metal net.

According to a fourth aspect of the present invention, there is provided an atmospheric pressure plasma generation method using the atmospheric pressure plasma generation apparatus according to any one of the first to third aspects, in the presence of gas, the electrode pair. An alternating electric field is applied between the two to generate glow discharge plasma under atmospheric pressure.

The atmospheric pressure plasma generating method according to a fifth aspect of the present invention is characterized in that the gas contains air as a main component.

[0009]

In the atmospheric pressure plasma generator according to claim 1 of the present invention, the electrode 1a connected to the AC power source 5 and the ground electrode 1b are connected.
In the atmospheric pressure plasma generator for generating glow discharge plasma under atmospheric pressure by providing an electrode pair 1 composed of and, in the presence of gas, an AC electric field is applied between the electrode pair 1. Since the entire surface of the conductor 2 is filled with the granular body 4 formed by covering the insulating body 3, the conductive body 2 in the granular body 4 constitutes an electrode having a small size, and the insulating body 3 serves as a dielectric barrier. And by so-called dielectric barrier discharge,
The gas is turned into plasma in the gap between the granular bodies 4.
Since the gap between the granular bodies 4 is small, a homogeneous glow discharge can be generated with a very small applied power and a plasma can be generated even with a gas having a large discharge starting voltage such as oxygen or nitrogen.

In the atmospheric pressure plasma generator according to claim 2 of the present invention, since the conductor 2 is a metal and the insulator 3 is an inorganic dielectric, it is excellent in durability and heat resistance.

In the atmospheric pressure plasma generator according to claim 3 of the present invention, since the electrode pair 1 is a metal net, gas can pass through the electrode pair 1.

According to a fourth aspect of the present invention, there is provided an atmospheric pressure plasma generation method using the atmospheric pressure plasma generation apparatus according to any one of the first to third aspects, in the presence of gas, the electrode pair. Since an AC electric field is applied between the two to generate glow discharge plasma under atmospheric pressure, the gas is turned into plasma in the gap between the granular bodies 4.

In the atmospheric pressure plasma generation method according to the fifth aspect of the present invention, since the gas contains air as a main component, ozone is generated. Therefore, when a slight amount of impurity gas is present in the air, This impurity gas is decomposed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings related to the embodiments.

1 (a) and 1 (b) are schematic views of an embodiment of an atmospheric pressure plasma generator according to the present invention.

The atmospheric pressure plasma generator according to the present invention comprises:
As shown in FIGS. 1A and 1B, an electrode pair 1 including an electrode 1a connected to an AC power source 5 and a ground electrode 1b.
By providing an AC electric field between the electrode pair 1 in the presence of gas to generate glow discharge plasma under atmospheric pressure, various surface treatments, ozone generation, exhaust gas treatment, etc. are performed. Is something that can be done. Between the electrode pair 1,
As shown in FIG. 2A, the entire surface of the conductor 2 is filled with the granular body 4 formed by covering the insulator 3. Examples of the conductor 2 include metals such as stainless steel, copper, brass, aluminum, iron, tungsten, nickel and tantalum, and carbon, but when durability and heat resistance are required, the metal is excellent. There is. Further, as the insulator 3, any organic or inorganic substance such as nylon, polyester, polyimide, Teflon, polysulfone, or epoxy can be used, but when durability and heat resistance are required, glass,
Inorganic dielectrics such as ceramics and enamels are excellent.
The method of coating the entire surface of the conductor 2 with the insulator 3 is not particularly limited. To be When the entire surface of the conductor 2 is coated with the organic material as the insulator 3, for example, an organic material such as a resin is coated around the conductor 2 by heat curing. It is preferable that the conductor 2 and the insulator 3 are brought into close contact with each other with as little space as possible in order to improve discharge efficiency. As shown in FIG. 2B, the granular body 4 may have a plurality of conductors 2 inside an insulator 3. That is, the conductor 2 may be dispersed in the insulator 3. The size of the granular body 4 varies depending on the use, but is generally on the order of 0.1 mm to several tens of mm. The shape may be spherical, angular, or indefinite, and is not limited. The coating thickness varies depending on the granular material and the coating method.

The material of the electrode pair 1 consisting of the electrode 1a and the ground electrode 1b is preferably a metal flat plate or a metal mesh. In the case of a metal net, 0.01 to 0.
It is preferable that the wire is made of a thin metal wire having a thickness of about 5 mm. Examples of the material of this metal net include stainless steel, copper, brass, aluminum, iron, tungsten, nickel, tantalum and the like. Various methods such as plain weave, twill weave, and tatami weave can be adopted as the weaving method of the metal net.

By placing the electrode 1a and the ground electrode 1b substantially in parallel, filling the granular body 4 and applying an AC electric field between the electrode pair 1 in the presence of gas, the atmospheric pressure is maintained. Then, a uniform glow discharge plasma is generated between the granular bodies 4. The mechanism of this glow discharge plasma generation is considered as follows. That is, the conductor 2 in the granular body 4 constitutes a small electrode, and the insulator 3 constitutes a dielectric barrier.
The so-called dielectric barrier discharge causes the gas to become plasma in the gaps between the granular bodies 4. Since the gap between the granular bodies 4 is small, a homogeneous glow discharge can be generated with an extremely small applied power and a plasma can be generated even with a gas having a large discharge starting voltage such as oxygen or nitrogen. Therefore, even air can be discharged. In addition, gases having a low discharge starting voltage such as hydrogen, argon, and helium can naturally be turned into plasma. As described above, since the granular body 4 constitutes the small dielectric barrier, the electrode interval and the electrode size can be arbitrarily set, but the discharge sustaining voltage becomes higher according to the size.

The AC frequency required for discharge can be used in the range of 50 Hz commercial frequency to high frequency (MHz). The method can be used for various processes. For example, as the surface treatment, when the object to be treated is installed in the downstream of the plasma space, the gas radicalized in the plasma remains without disappearing and acts on the surface of the object to be treated, so-called low temperature plasma treatment can be performed. Further, when the gas is air, ozone is generated by the air passing through the discharge space. According to the atmospheric pressure plasma generation method of the present invention, since the discharge space is large, the generation efficiency is higher than that of the conventional method. Further, by passing a gas containing a malodorous component such as ammonia or hydrogen sulfide, these malodorous components can be decomposed and rendered harmless. This is because the discharge is uniform,
The decomposition efficiency is higher than that of the conventional method.

An example of a method for generating atmospheric pressure plasma using the atmospheric pressure plasma generator of the present invention will be described below.

(Embodiment 1) In the atmospheric pressure plasma generator shown in FIG. 1 (a), a parallel plate electrode pair 1 consisting of a stainless steel electrode 1a and a ground electrode 1b connected to an AC power source 5 is set to 3 cm. Installed at intervals. The space of the electrode pair 1 was filled with the granules 4 formed by spraying alumina around the copper granules with a diameter of 3 mm to a thickness of 100 μm. A voltage of 60 Hz and 5 KV was applied to both ends of the electrode pair 1, and dry air (79% nitrogen, 21% oxygen) was passed through the space at a flow rate of 10 l / min to generate plasma.
A high density polyethylene film was placed for 1 minute downstream of the plasma space (not shown). The plasma-treated high-density polyethylene film was bonded to an aluminum plate via an epoxy adhesive, and the adhesive strength (shear stress test) was measured. It was found that the plasma-untreated product had an adhesive strength of 500 psi. The adhesive strength of the plasma-treated product was 2800 psi, and the adhesive strength of the plasma-treated product was significantly improved as compared with the plasma-untreated product.

(Embodiment 2) In the atmospheric pressure plasma generator shown in FIG. 1B, a stainless wire mesh of 325 mesh with a wire diameter of 0.035 mm, which is connected to an AC power source 5, is composed of an electrode 1a and a ground electrode 1b. Used as electrode pair 1,
Inject dry air (79% nitrogen, 21% oxygen) for 60H
A voltage of z and 5 KV was applied to generate plasma. The ozone generation energy efficiency at this time was investigated. As a result of measuring the current-voltage characteristics with an oscilloscope, creating a Lissajous figure, and examining the discharge energy, it was confirmed that the efficiency was improved by about 35% as compared with the conventional energy efficiency of ozone generation by silent discharge.

(Example 3) In Example 2, the dry air containing 100 ppm of ammonia gas (nitrogen 79%,
Oxygen 21%) was passed through the plasma space at a flow rate of 10 l / min. A voltage of 60 Hz and 5 KV was applied to this to generate plasma. As a result of analyzing the concentration of the outlet gas with a gas detector tube, the ammonia concentration was reduced to 5 ppm.

In Examples 1 to 3, the granular body 4 was not formed by covering the entire surface of the conductor 2 with the insulator 3, but the granular body 4 formed by only the insulator 3 was used. In case of 60Hz, 5KV, of course, 6
Plasma was not generated even when a voltage of 0 Hz and 15 KV was applied.

[0025]

According to the atmospheric pressure plasma generator of the first aspect of the present invention, even in the case of gas such as oxygen, nitrogen or air having a high discharge start voltage, a uniform glow discharge is generated with an extremely small applied power. As a result, stable glow discharge can be generated even in air under atmospheric pressure, and atmospheric pressure plasma having excellent energy efficiency and reaction efficiency can be generated.

According to the atmospheric pressure plasma generator of the second aspect of the present invention, the conductor 2 is a metal and the insulator 3 is a metal.
Since it is an inorganic dielectric, it has excellent durability and heat resistance in addition to the above.

According to the atmospheric pressure plasma generator of the third aspect of the present invention, since the electrode pair 1 is a metal mesh, gas can pass through the electrode pair 1, and therefore energy efficiency and reaction efficiency can be further improved. Excellent in.

According to the atmospheric pressure plasma generation method of the fourth aspect of the present invention, the electrode is formed in the presence of gas by using the atmospheric pressure plasma plasma generation apparatus of any one of the first to third aspects. Since an AC electric field is applied between pair 1 to generate glow discharge plasma under atmospheric pressure, the granular material 4
Since the gas is turned into plasma in the gap between the granular body 4 and the granular body 4, a uniform glow discharge can be generated with an extremely small applied power, and thus a stable glow discharge can be generated even in air under atmospheric pressure. Excellent in efficiency and reaction efficiency.

According to the atmospheric pressure plasma generation method of the fifth aspect of the present invention, ozone is generated, the efficiency of ozone generation energy is improved, and the impurity gas in the air is decomposed, so that the exhaust gas is polluted. Can purify substances.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an atmospheric pressure plasma generation device according to an embodiment of the present invention, FIG. 1 (a) is a sectional view of a main part of the atmospheric pressure plasma generation device in which a material of an electrode pair is a flat metal plate, and FIG. )
FIG. 3 is a cross-sectional view of a main part of an atmospheric pressure plasma generator in which a material of an electrode pair is a metal mesh.

FIG. 2 is a sectional view of a granular body used in an atmospheric pressure plasma generator according to an embodiment of the present invention, (a) is a sectional view of the granular body formed by coating the entire surface of a conductor with an insulator, b) is a cross-sectional view of a granular body in which a plurality of conductors exist inside an insulator.

[Explanation of symbols]

 1 Electrode pair 1a Electrode 1b Grounding electrode 2 Conductor 3 Insulator 4 Granular body 5 AC power supply

Claims (5)

[Claims] 1. An electrode (1) connected to an AC power source (5)
An electrode pair (1) including a) and a ground electrode (1b) is provided, and an AC electric field is applied between the electrode pair (1) in the presence of gas to generate glow discharge plasma under atmospheric pressure. In the atmospheric pressure plasma generator, the granular body (4) formed by covering the entire surface of the conductor (2) with the insulator (3) is filled between the electrode pair (1). Atmospheric pressure plasma generator. 2. The atmospheric pressure plasma generator according to claim 1, wherein the conductor (2) is a metal and the insulator (3) is an inorganic dielectric. 3. The atmospheric pressure plasma generator according to claim 1, wherein the electrode pair (1) is a metal net. 4. An atmospheric pressure plasma plasma generator according to claim 1 is used to apply an AC electric field between the electrode pair (1) in the presence of gas, A method for generating atmospheric pressure plasma, characterized in that glow discharge plasma is generated under atmospheric pressure. 5. The atmospheric pressure plasma generation method according to claim 4, wherein the gas contains air as a main component.