JP2000348848A - Low-temperature plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-yield device capable of preventing generation of nitrogen oxides due to secondary discharge action and temperature rise due to heat generation in the lower stream side end of a discharge part in a silent discharged low-temperature plasma generator and of generating an ozone and a hydroxyl group. SOLUTION: This low-temperature plasma generator is constituted therein an outer side discharge part 4 and an inner side discharge part 7 are protected with predetermined spaces by placing an outer side space 8 and an inner side space 9 and both ends of a glass protective tube 1 are sealed by sealing bodies 10a and 10b, the outer side discharge part 4 has an outer side electrode 2 disposed on the outer periphery of a dielectric 3 and the inner side discharge part 7 has an inner side electrode 6 disposed in a dielectric 5 concentrically inserted into the glass protective tube 1. An introducing path 11 is disposed inside the sealing body 10a and is communicated with the outer side space 8 through an introducing chamber 13. The inner side space 9 is communicated with an evacuation path 12 through an evacuation chamber 14. Inside the other sealing body 10b, the outer side space 8 is communicated with the inner side space 9 through a communication camber 15. The outer side electrode 2 is provided with a plurality of small holes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for sterilizing ozone,
Alternatively, the present invention relates to a low-temperature plasma generator that is generated by silent discharge to be used for sterilization, deodorization, and maintaining freshness of food products.

[0002]

2. Description of the Related Art As a system for generating ozone, there are an ultraviolet system for irradiating ultraviolet rays to oxygen in the air, a discharge system using silent discharge, and an electrolysis system for electrolyzing water. It is often used as a material that is suitable for generating large quantities in the world. There are several types of low-temperature plasma generators based on the discharge method, that is, ozone generators, and a silent discharge type, a creeping discharge type, a corona discharge type and the like are known.

[0003] The principle structure of the silent discharge type is that one or both of a pair of electrodes are covered with a dielectric such as glass or ceramics, and are opposed to each other. And a medium of 50 Hz between both electrodes.
A high voltage having a frequency of about 2 kHz is applied to decompose the acidity O ₂ to generate ozone O ₃ . As an example of such a silent discharge type ozone generator, a coaxial type in which stainless steel pipe electrodes are provided concentrically double inside and outside is generally used.

In this coaxial type device, the inside of the outer electrode and the outside of the inner electrode are each surrounded by a dielectric such as glass.
A predetermined space is provided between the outer and inner dielectrics, both ends are sealed with a sealing body, and air or oxygen passes through the space from one side to the other of the conduction holes provided in the sealing bodies at both ends. The medium is circulated, and a medium such as ozone O ₃ is generated by a discharge action by a high voltage of 10 to 20 kV applied to both electrodes.

[0005] Another example of a silent discharge type ozone generator generally widely used is a contact type ozone generator.
In this contact type, a stainless steel pipe is closely attached to the outer periphery of a glass dielectric, inserted and used as a ground electrode, and the inner electrode is a coil-shaped thin metal wire containing molybdenum, titanium, etc. It is composed of a body closely attached to the inside of the body. A relatively low voltage of 5 to 8 kV is applied between both electrodes to efficiently generate ozone. Cooling fins are attached to the outer periphery of the stainless steel pipe, and some of them are cooled by water cooling. It is one of the most frequently used ozone generators because of its simple structure and low cost.

In addition to the general silent discharge type ozone generator described above, a special example disclosed in Japanese Patent Application Laid-Open No. 8-185555 is known. In the ozone generator according to this publication, a rod-shaped conductor is inserted into a cylindrical ceramic dielectric, both ends are integrally joined by a sealing body, and a plurality of sealed electrodes are joined between the ceramic dielectrics in a line contact state. The device is placed in the air or water, and ozone is generated by a discharge generated between the dielectrics.

[0007]

By the way, the above-mentioned general coaxial ozone generator has the following various problems. The amount of O atoms generated by applying a high voltage to decompose a medium such as air or oxygen is proportional to the current, and thus the amount of O ₃ generated is generally proportional to the current. Because medium is circulated to the downstream side from the longitudinal upstream side of the apparatus, but O ₃ concentration increases the residence time of the O ₃ from the upstream side in the downstream end side of the discharge portion is increased, O ₃ concentration It becomes higher when the decomposition of O ₃ by the electron collision against O ₃ also increases, increasing the O ₃ will not occur. That is, a state of discharge equilibrium is reached, and near the downstream end of the discharge part, the heat generation of the dielectric material is remarkable and the temperature rises.

For this reason, generally, it is necessary to provide cooling fins on the outer periphery of the discharge portion to perform forced cooling or cooling with water.
In addition, when high humidity air containing a large amount of water is used as a medium, the OH radicals generated by the discharge unit themselves decompose ozone to lower the yield, and at the same time, convert nitric acid from nitrogen oxides due to nitrogen contained in the air. The generated air causes deterioration of the electrodes, and in order to reduce the generated air as much as possible, the air to be supplied is inserted with silica gel on the blowing side and is sent as dry air by a heater or the like. For this reason, costs are incurred. In addition, the above-mentioned problems are similar in the contact-type ozone generator which is widely used, and the structure is also considered so that the electrode can be cleaned or replaced immediately, so that frequent maintenance and inspection are required. Must.

Furthermore, since the dimensional tolerance at the time of manufacture is large and the gap between the dielectric glass and the dielectric glass inserted inside the outer electrode is loose, a very small gap is generated between the two. A secondary discharge is generated in this gap. For this reason, a small amount of ozone is generated, and if used for a long period of time, it will corrode wiring and electronic equipment. Also, the wiring box is particularly corroded.

[0010] The above-mentioned various problems apply almost directly to the special apparatus of the above-mentioned patent publication, and the apparatus of this patent publication merely improves the production yield of ozone and the like. Is not a fundamental solution.

The present invention is directed to a low-temperature plasma capable of generating ozone at a high yield without releasing ozone generated by a secondary discharge to the outside, taking into account the various problems of the conventional ozone generator described above. It is an object to provide a generator.

An object of the present invention is to provide a low-temperature plasma generator which can be manufactured at an economical cost with an extremely simple structure, while suppressing the temperature rise due to heat generation at the downstream end of the discharge part together with the first problem. As a second problem.

[0013]

According to the present invention, as a means for solving the above-mentioned problems, an outer discharge portion and an inner discharge portion are concentrically provided with a predetermined space in the radial direction inside a cylindrical protective member. The outer discharge portion is provided with a cylindrical outer electrode inserted outside the cylindrical dielectric, and the inner discharge portion is provided inside the cylindrical dielectric material. A medium such as air or oxygen is introduced by connecting the introduction path provided in one of the sealing bodies to each space to introduce a medium such as air or oxygen, and a medium generated from the medium by a discharge action between both electrodes. Is passed through each space to be discharged from a discharge path provided in the other sealing body.

In the low-temperature plasma generator configured as described above, ozone is generated with a high yield. When a medium such as air or oxygen is sent from the outside via the introduction path, the air flows through the outer and inner spaces, but at this time, when a high voltage is applied between the outer and inner electrodes, the outer electrode and the dielectric are interposed. Ozone is generated in a small space by the secondary discharge action. The ozone generated in this way flows out from both ends of the outer electrode, is combined with air or oxygen flowing in the outer space, and is carried to the downstream side.

At the same time, the medium flowing through the inner space is decomposed by the primary discharge action of the two electrodes to generate a medium of ozone, which is conveyed to the downstream side and generated by the secondary discharge action before the discharge path. And is discharged from the discharge path. In this case, since the medium is also sent to the space between the outer electrode and the protection member, the outer electrode is cooled by the medium. Accordingly, the cooling of the primary discharge and the secondary discharge is performed by the medium in the outer space, thereby delaying the saturation state of ozone due to the primary discharge. For this reason, the generated medium can be obtained in a higher yield than a conventional ozone generator.

A low-temperature plasma generating apparatus according to a second aspect of the present invention is based on the apparatus according to the first aspect of the present invention, and a part thereof is configured as follows. That is, the introduction path provided in the one sealing body is communicated with the outer space of the space to introduce a medium such as air or oxygen, and the flow is reversed in the other sealing body to form the inner space. And a low-temperature plasma generator configured to discharge the medium generated from the medium by the discharge action of the two electrodes through an exhaust path provided in one of the sealing bodies so as to flow through the inner space.

In the second aspect of the present invention, the introduction path and the discharge path are provided in one of the sealed bodies, and the medium flowing in the outside space due to the reversal of the flow in the other sealed body is transferred to the inside space. Flows. While the medium containing ozone flows through the inner space, the air or oxygen containing ozone is decomposed by the primary discharge action of the silent discharge between the two electrodes to generate a medium such as ozone. As it flows to the side, the concentration of ozone increases. In this case, the saturation of the primary discharge due to the temperature rise of the medium such as ozone is also delayed by the cooling of the medium in the outer space as in the first invention. However, the temperature rise due to the discharge portion occurs near the sealing body on the inflow side that sends air or oxygen from the outside to the sealing body, and the cooling action by the air or oxygen sent from the outside is greater on this inflow side, For this reason, the temperature rise can be suppressed more effectively.

As described above, ozone is generated by adding secondary ozone generation to primary discharge ozone, so that the ozone generation yield is higher than that of the conventional one-pass type. Greatly increase. If ozone generated by the secondary discharge action remains in a small gap between the outer electrode and the dielectric for a long period of time, the electrode exerts a corrosive action. In this invention, ozone flows out from both ends of the outer electrode. Therefore, the conventional corrosive action is reduced.

The outer electrode of the outer discharge portion according to the first and second aspects of the present invention has a cylindrical shape and is inserted outside the cylindrical dielectric. However, the outer electrode may be provided with a number of small holes. it can. As described above, there is a small gap between the outer electrode and the dielectric. However, when a large number of small holes are provided in the outer electrode, the secondary discharge action is further increased through the edges of the small holes. Since the medium such as ozone generated by the secondary discharge can flow out of the small hole to the outside in the radial direction of the outer electrode, the medium generated by the small gap and the small hole is smaller than that of the first and second inventions. Further increase. Since this medium is sent downstream together with the medium flowing outside the outer electrode, more medium flows out from the discharge path provided in the sealing body, and the yield of medium generation is improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a main cross-sectional view of the low-temperature plasma generator of the embodiment. Reference numeral 1 denotes a glass protective tube, in which an outer discharge portion 4 and an inner discharge portion 7 are provided concentrically. Although a circular cross section is shown in the illustrated example, a cross section of another shape such as a rectangular shape may be used. The outer discharge section 4 is formed by inserting a cylindrical dielectric 3 inside a cylindrical outer electrode 2.

The inner discharge portion 7 is formed by inserting a cylindrical dielectric 5 outside a cylindrical inner electrode 6. An outer space 8 and an inner space 9 having predetermined dimensions are formed between the glass (quartz glass) protective tube 1 and the outer discharge portion 4 and between the outer discharge portion 4 and the inner discharge portion 7, respectively. Alternatively, a medium such as oxygen or a generated medium can be circulated.

Both ends of the protective tube 1, the outer discharge part 4 and the inner discharge part 7 are sealed by sealing members 10a and 10b, and a medium such as air or oxygen is introduced into one of the sealing members 10a. A path 11 and a discharge path 12 for discharging the generated medium are provided. The introduction path 11 communicates with the outer space 8 via the introduction chamber 13, and the discharge path 12 communicates with the inner space 9 via the discharge chamber 14. Also, the sealing body 10b on the opposite side
Inside, the outer space 8 is connected to the inner space 9 via a connection space 15.

The inner electrode 6 of the inner discharge part 7 and the outer discharge part 4
A high-frequency high voltage is applied to the outer electrode 2 from the power source P, and discharge is performed between the electrodes 2 to 6 via the dielectrics 3 and 5. Air or oxygen is sent to the introduction path 11 from an air pump F or an oxygen cylinder (not shown), and these mediums are decomposed by a discharge action while flowing through the outer space 8 and the inner space 9 to form a medium such as ozone. And discharge path 1
Exhausted from 2.

The outer electrode 2 of the outer discharge section 4 is made of a dielectric 3
In this case, a stainless steel pipe is used for the outer electrode 2 as a conductive metal material in order to make the outer electrode 2 adhere to the surface of the dielectric 3, and is shown in the cross section of FIG. As described above, a partly cut circular cross section cut at one location on the circumference by a cutting line along the longitudinal direction is put on the outside of the dielectric 3 and elastically closes inward so as to contract inward. Attach as follows. Conversely, the inner electrode 6 of the inner discharge portion is also made of a stainless steel pipe, and a partly cut circular cross-section obtained by cutting one location on the circumference along a cutting line along the longitudinal direction is used as the dielectric material 5. It is mounted inside and is closely attached to and inserted into the dielectric 5 due to the elasticity of the pipe that tends to spread outward.

Each of the dielectrics 3 and 5 is made of a glass dielectric or a ceramic dielectric. Sealing body 1
Reference numerals 0a and 10b are formed by solidifying an inorganic or organic adhesive. Further, as shown in FIGS. 3 and 4, a large number of small holes 2a are randomly arranged in the outer electrode 2. 2
This is because the medium generated by the next discharge is released to the outer space 8. The large number of small holes 2a are processed so that the area obtained by subtracting the total area of the small holes formed from the outer electrode 2 becomes the outer peripheral area of the inner electrode 6 or more.

As shown in FIG. 4, the size, number and arrangement of the outer electrodes 2 are set such that the total area of a large number of small holes 2a in the stainless steel plate is the above-mentioned ratio. Then, the thin plate is bent by a roll and formed into a pipe with a partially cut circular cross section. The outer electrode 2 thus formed is closely attached to and inserted into the outer periphery of the dielectric 3 as described above, so that there is almost no gap between them.

However, since there is actually a dimensional tolerance in the production, there is a very small tolerance gap as shown in the cross section of FIG. As will be described later, a medium such as ozone is generated by the secondary discharge action from the cross section of the tolerance gap and the small holes, and these mediums are discharged from the large number of small holes 2a to the outer space 8.

The low-temperature plasma generator of the embodiment configured as described above operates as follows. In a low-temperature plasma generator, when a high voltage is applied between both electrodes, the discharge is suppressed by the dielectric and the electron temperature reaches an extremely high temperature, but the temperature of the molecules is kept at almost normal temperature (low-temperature plasma). It is generally called an ozone generator or ozonizer. Hereinafter, an ozone generator will be described.

The medium such as air or oxygen fed from the air pump F or the like passes through the outer space 8, is reversed in the feed direction in the connection space 15, is sent into the inner space 9, and is discharged into the discharge chamber 1.
4 and is discharged from the discharge path 12. Due to the high voltage applied to the outer discharge part 4 and the inner discharge part 7 during the passage of the medium, the secondary discharge is caused by a very small tolerance gap between the outer electrode 2 and the dielectric 3 and the cross section of the small hole. Action occurs.

This secondary discharge action is due to the corona discharge action generated between the edges of the many small holes 2a provided in the electrode 2 and the dielectric 3, and the secondary discharge action causes a slight discharge. Ozone is generated by decomposing oxygen in the air from the narrow gap and the cross section of the small holes, and the generated ozone is generated by the large number of small holes 2a.
Out into the outer space 8. The ozone flowing into the outer space 8 flows to the inner space 9 together with the air or oxygen flowing through the outer space 8.

While moving along the longitudinal direction of the inner space 9, the two electrodes 2 and 6 are decomposed by the silent discharge action to generate ozone, and the generated ozone is sealed on the inflow side while the ozone concentration increases. It flows toward the stop 10a. When this medium advances to the end of the inner space 9 on the side of the sealing body 10a, the ozone concentration increased by the discharge during that time reaches a discharge equilibrium state, and the ozone concentration does not increase beyond a certain level.

In such a state, in the case of the conventional ozone generator, the vicinity of the downstream end at which the discharge is equilibrated is particularly heated and the temperature rises.
Since the introduction chamber 13 communicating with the outer space 8 is provided inside a, the discharge portion is entirely cooled by a medium such as air or oxygen introduced from the outside. Therefore, the temperature rise near the downstream end is also greatly suppressed. For example, even if electricity is continuously supplied for 3 hours at a room temperature of 20 ° C. by using the illustrated apparatus, the temperature of the external glass protection tube 1 is 5 ° C. under the condition of a blowing rate of 5 l / min.
It only raises the temperature to 5 ° C. For this reason, there is no need for cooling in a short operation. It is considered that the temperature rise due to the primary discharge is very slow since it is a discharge through the inner and outer electrode co-glass dielectrics, and does not affect the temperature rise.

Further, the amount of ozone generated by the secondary discharge between the outer electrode 2 and the dielectric 3 is smaller than the amount of air or oxygen blown, and the cross section of the small holes becomes the resistance of the blow, thereby promoting cooling. NO oxides are measured. Therefore, rust is not generated on the electrode 2 or the wiring due to the nitrogen oxide, and deterioration due to long-term use of the electrode and the like does not occur.

In the above-described first embodiment, the introduction path 11 and the discharge path 12 are provided in one sealing body 10a. However, as in the second embodiment shown in FIG. The introduction path 11 may be provided, and the discharge path 12 may be provided in one of the sealing bodies 10a. In this example, a medium such as air or oxygen introduced from the introduction passage 11 flows to both the outer and inner spaces 8 and 9 through the communication chamber 15 and the other communication chamber 13 provided in the sealing body 10a. And are discharged from the discharge path 12.

The other configuration is basically the same as that of the first embodiment, and the same reference numerals are given and the description is omitted. In this example, the introduction path 11 is provided on the side opposite to the discharge path 12, but the temperature rise of the discharge section is entirely caused by the inflow of the medium by air or oxygen from the introduction path 11 as in the first embodiment. Since the medium is cooled, the generation of the medium such as ozone by the secondary discharge is performed in the tolerance gap between the outer electrode 2 and the dielectric 3 and a large number of small holes as in the first embodiment.
The point that a high yield is obtained is the same as in the first embodiment.

In the first and second embodiments, the outer electrode 2 is provided with a large number of small holes, but these small holes can be omitted. If a large number of small holes are not provided, it is impossible to generate a medium such as ozone by secondary discharge through the edge of the small holes. However, the point where the intersecting gap actually exists between the outer electrode 2 and the dielectric 3 is the same, and a secondary discharge action is exerted on the air or oxygen contained in the intersecting gap to generate a medium such as ozone. This is the same as in the first and second embodiments.

The medium generated in the tolerance gap is the outer electrode 2
Are gradually leaked to the outside from both ends and are contained in a medium such as air or oxygen flowing outside the outer electrode 2 and are sent downstream. Therefore, even if there are not many small holes, a small amount of the medium is sent to the downstream side. Further, as described above, the generation of the medium due to the primary discharge in the inner electrode 6 increases due to the cooling effect of the medium flowing in the outer space 8 as in the first and second embodiments. Therefore, it is apparent that the generation yield of the medium as a whole is improved as compared with the conventional example.

[0038]

As described above in detail, in the low-temperature plasma generator of the present invention, a predetermined space is provided in the protective member, the outer discharge portion and the inner discharge portion are provided concentrically, and both ends are sealed. Because the medium is introduced from the introduction path of one of the sealing bodies, the medium is introduced to flow through each space, and the medium generated by the discharge action of both electrodes is discharged from the discharge path provided in the other sealing body. While the medium flows through each space, the medium is decomposed by the discharge action of both electrodes to generate a medium such as ozone, the medium is cooled by the medium passing through the outer space, and the medium generated by the primary discharge in the inner space is saturated with the medium. The medium yielded by the secondary discharge flows out from both ends of the outer electrode into the space outside the outer discharge part through a slight gap between the electrode and the dielectric of the outer discharge part. Discharged to the discharge path, and Medium to be of the occurrence by just not secondary discharge occurs even remarkable effect that it is possible to generate a medium such as ozone in a high yield by being added is obtained.

In the above generator, the introduction path provided in one of the sealed bodies is communicated with the outer space, and the medium to be introduced is reversed in the other sealed body to flow through the inner space, When the medium is discharged from the discharge path provided in one of the sealing bodies so as to communicate with the inner space while the medium flows through the outer and inner spaces, the medium generated by decomposing the medium by the discharge action of both electrodes is discharged. In the same manner as in the above-described invention, an effect is obtained that a medium such as ozone can be generated at a higher yield by discharging the medium generated by the primary discharge and the secondary discharge. Therefore, there is no need to provide a cooling fin outside the conventional discharge unit and cool it with a blower, and the advantage is obtained that it can be manufactured extremely simply and economically.

Further, in any of the above-described generators, when a large number of small holes are provided in the cylindrical body of the outer electrode, a medium such as ozone is generated by a secondary discharge action by corona discharge at the edge portion of the large number of small holes. The medium is generated, flows out of the small holes into the outer space, and merges with the medium by the primary discharge in the inner space, so that the effect of further improving the generation yield of the medium is obtained.

[Brief description of the drawings]

FIG. 1 is a main longitudinal sectional view of a low-temperature plasma generator of an embodiment.

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

FIG. 3 is a partially enlarged sectional view of an outer discharge portion.

FIG. 4 is a developed plan view of the outer electrode 2.

FIG. 5 is a schematic diagram of a low-temperature plasma generator according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass protective tube 2 Outer electrode 3, 5 Dielectric 4 Outer discharge part 6 Inner electrode 7 Inner discharge part 8 Outer space 9 Inner space 10a, 10b Sealing body 11 Introducing path 12 Discharge path 13 Introducing chamber 14 Discharging chamber 15 Communication chamber

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yosuke Nomura 3-279, Hino, Daito City Nomura Electronics Industry Co., Ltd. F-term (reference) 4B021 LT03 MC01 MK01 MK13 MP06 4C080 AA07 BB02 BB05 CC01 HH02 JJ01 KK02 LL01 MM08 QQ17 4G042 CA01 CC03 CC06 CC10 CC16 CC20

Claims (5)

[Claims] 1. An outer discharge portion and an inner discharge portion are provided concentrically with a predetermined space in the radial direction inside a cylindrical protection member, and both ends are sealed with a sealing body. The cylindrical outer electrode is inserted outside the cylindrical dielectric, and the inner discharge part is formed by inserting the cylindrical inner electrode inside the cylindrical dielectric, respectively. A medium such as air or oxygen is introduced by connecting the provided introduction path to each space, and a medium generated from the medium by the discharge action between the two electrodes flows through each space to discharge the other sealing body. A low-temperature plasma generator configured to be discharged from a road. 2. A medium such as air or oxygen is introduced by connecting an introduction path provided in the one sealing body to an outer space of the space, and a flow is reversed in the other sealing body. A medium flowing through the inner space, a medium generated from the medium by the discharge action of the two electrodes is passed through the inner space, and is discharged from a discharge path provided in one of the sealing bodies. 2. The low-temperature plasma generator according to 1. 3. The low-temperature plasma generator according to claim 1, wherein a number of small holes are provided in the outer electrode. 4. The number of the plurality of small holes and the number of the small holes so that the area obtained by subtracting the entire area of the small holes from the outer peripheral area of the outer electrode is equal to or larger than the outer peripheral area of the inner electrode. The low-temperature plasma generator according to claim 3, wherein an area is set. 5. The outer discharge portion is formed in a cylindrical shape, the outer electrode is formed using an elastic conductive metal plate, and has a partially cutout circular cross section cut in the longitudinal direction to form an outer electrode. The low-temperature plasma generator according to any one of claims 1 to 4, wherein the low-temperature plasma generator is closely attached and inserted so as to contract around the circumference.