JP2002159844A - Low temperature plasma generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit a temperature rise and to generate an ozone at high yield by generating no discharge equilibrium at a discharge part without providing a specific cooling means in a coaxial type low temperature plasma generation device. SOLUTION: The low temperature plasma generation device is concentrically provided with an inner side discharge part 3 having an electrode 1 and a dielectric 2; and an outer side discharge part 6 having a dielectric 4 and an electrode 5. Both ends of both discharge parts are closed by seal bodies 10a, 10b. A conducting pipe 11 penetrating through one seal body 10 is connected to a space 7 at an inner side of the electrode 1 and is connected to a space 8 between both discharge parts by a connection space 15 of the other seal body 10b. A medium including ozone generated at the discharge space of the space 8 by a discharge action is discharged from a discharge pipe 12 of one seal body.

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 typical example of a low-temperature plasma generating apparatus for generating ozone by silent discharge, a coaxial type in which stainless steel pipe electrodes are provided concentrically inside and outside are 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, and both ends are sealed with a sealing body. A medium such as air or oxygen flows from one of the conduction holes provided in the sealing bodies at both ends through the other space, and the ozone O _{3 is} discharged by a high voltage of 10 to 20 kV applied to both electrodes. Generate media.

[0003] In addition to the above, as a silent discharge type ozone generator, a contact type electrode in which a stainless steel pipe electrode is closely adhered to the outer periphery of a glass dielectric and an inner electrode of a coiled thin wire is closely adhered to the inner periphery of the glass dielectric is used. And JP-A-8-1859
There is also a special example disclosed by Japanese Patent Publication No. 55-55.

[0004]

In the above-described ozone generator of the coaxial type, when a medium such as air or oxygen is decomposed by a discharge action to generate ozone, a state of discharge equilibrium occurs near the downstream end. In addition, there is a problem that the heat generation of the dielectric material becomes remarkable and the temperature rises. When a high voltage is applied to decompose a medium such as air or oxygen, in the downstream side of the discharge portion long Todokotamari time O ₃ from the upstream side (ozone), O ₃ concentration is also high but, O ₃ concentration This is because as the value of O increases, the decomposition of O ₃ due to electron collision increases, and O ₃ does not increase.

For this reason, generally, it is necessary to provide cooling fins on the outer periphery of the discharge part and to forcibly cool it by wind or water. Also, if high concentration air containing a lot of water is used as the medium,
The OH radicals generated by the discharge unit themselves decompose ozone to lower the yield, and at the same time, generate nitric acid from nitrogen oxides due to nitrogen contained in the air to cause deterioration of the electrode. For this reason, in order to reduce this as much as possible, measures have been taken such as inserting silica gel into the air supply side and sending out the air as dry air by a heater or the like.

Therefore, since the above various measures are taken, the equipment is complicated and the cost is high. Also, the contact-type ozone generator, which is widely used, has the same problems as described above.Furthermore, the structure is also considered so that the electrode can be cleaned and the electrode can be replaced immediately, and frequent maintenance and inspection are required. However, due to the complicated structure, maintenance and inspection are difficult, and much labor and labor are required.

The present invention has been made in consideration of the above-described various problems, and has been made to prevent a discharge equilibrium state by being effectively cooled using a medium such as air or oxygen supplied without forcibly cooling with cooling fins. It is another object of the present invention to provide a low-temperature plasma generator capable of generating ozone with high yield.

[0008]

According to the present invention, as a means for solving the above-mentioned problems, an inner discharge portion and an outer discharge portion are provided concentrically at a predetermined space in a radial direction and sealed at both ends. The inner discharge part has a cylindrical inner electrode inserted inside the cylindrical dielectric, and the outer discharge part has a cylindrical outer electrode inserted outside the cylindrical dielectric. A conductive tube penetrating one of the sealing bodies is connected to the cylindrical dielectric of the inner discharge part, a medium such as air or oxygen is introduced, and the medium is inverted by the other sealing body to form an outer discharge part. Thus, a low-temperature plasma generator is configured to flow through the space described above and discharge the medium generated from the medium by the discharge action between the two electrodes from the discharge part provided in one of the sealing bodies.

The low-temperature plasma generator configured as described above generates ozone at a high yield without providing a special cooling device. When a medium such as air or oxygen is sent from the conduction tube into the inner space of the cylindrical inner electrode of the inner discharge unit,
It spreads in the space inside the sealed body on the opposite side passing through the inner space, where the flow direction is reversed and the discharge space between the cylindrical dielectric of the inner discharge part and the cylindrical dielectric of the outer discharge part And flows toward one of the sealing bodies.

When a high voltage is applied to both electrodes while the medium flows through the discharge space to cause a discharge action on the medium, the medium is decomposed and ozone is generated. In the flow of the medium containing ozone, the ozone concentration increases as it flows downstream, and when the ozone concentration increases, the temperature generally rises due to the heat generated by the dielectric. In this device, the medium is supplied inside the discharge space. Since the medium flows in contact with the inner discharge part,
Cooling is performed along the entire length of the discharge space. Particularly near the downstream side, the temperature of the medium supplied through the conduit is the lowest, so that the cooling effect is large and the temperature rise is effectively suppressed. Therefore, a medium having a high ozone concentration can be obtained with almost no discharge equilibrium.

[0011]

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. This device comprises an inner discharge section 3 in which a cylindrical dielectric 2 is inserted outside a cylindrical inner electrode 1, and a cylindrical outer electrode 5 outside a cylindrical dielectric 4.
Are provided concentrically with the outer discharge portion 6 in which is inserted. A cross section of another shape such as an ellipse other than the circular cross section may be used. Cross-sectional spaces 8 and 7 having predetermined dimensions are formed between the outer discharge portion 6 and the inner discharge portion 3 and in the inner electrode 1, respectively, so that a medium such as air or oxygen and a generated medium can flow. I have. Although not shown,
It is preferable to provide an insulating protection member in close contact with the outside of the outer electrode 5.

Both ends of the inner discharge portion 3 and the outer discharge portion 6 are sealed by sealing members 10a and 10b.
A conduit 11 for introducing a medium such as air or oxygen,
A discharge pipe 12 for discharging the generated medium is provided. The conduit 11 is connected to the inner space 7 through the introduction chamber 13.
The discharge pipe 12 communicates with the outer space 8 via the discharge chamber 14. Further, inside the sealing body 10b on the opposite side, the inner space 7 is connected to the outer space 8 via the connection space 15. 12a is a discharge hole, 16 is O
-A ring. 1a and 5a are electrode rods, respectively.

The inner electrode 1 of the inner discharge part 3 and the outer discharge part 6
A high-frequency high voltage is applied to the outer electrode 5 from the power source P via the electrode rods 1a and 5a, and discharge is performed between the electrodes 1 to 5 through the dielectric. Air or oxygen is sent from the air pump F or an oxygen cylinder (not shown) to the introduction pipe 11,
These media are decomposed by the discharge action while flowing from the inner space 7 to the outer space 8, generate a medium such as ozone, and are discharged from the discharge pipe 12.

The electrodes 1 and 5 of the discharge portions 3 and 6 are made of conductive stainless steel pipes and are closely fitted to dielectric members 2 and 4 made of glass or ceramics. Due to errors, it is difficult to bring the electrodes 1 and 5 into complete contact with the dielectrics 2 and 4. For this reason, in the illustrated example, as shown in FIGS. 2 and 3, mesh-like joining members 1 ′ and 5 ′ each formed by knitting a stainless steel thread cover the outer periphery of the electrode 1 and the inner periphery of the electrode 5. In this case, the joining members 1 ′ and 5 ′ make close contact with the dielectrics 2 and 4. In the illustrated example, the threads of the joining members 1 'and 5' are set to 0.
A 2 mmφ diameter is used.

The sealing bodies 10a and 10b are made by molding an inorganic or organic adhesive in a predetermined mold and solidifying it, but may be molded by any other method. The inner electrode 1 is groove 1 _T at the tip is provided in a ring shape (see FIG. 4), when assembling the inner electrode 1, the groove 1 _T
Is inserted through a small hole provided in the sealing body 10b at a position corresponding to
Tip fixed the electrode rod 1a are electrode rods 1a is detachably attached to the sealing body 10b to be fitted into the groove 1 _T.

Ozone is generated with high efficiency by the low-temperature plasma generator of the embodiment having the above-described configuration. In a low-temperature plasma generator, when a high voltage is applied between both electrodes, discharge is suppressed by a dielectric and the electron temperature is extremely high (plasma).
, But the temperature of the molecules is kept at about room temperature (low-temperature plasma) and is thus called an ozone generator or ozonizer. Hereinafter, it is referred to as an ozone generator.

The medium, such as air or oxygen, sent from the air pump F or the like passes through the space 7 in the inner electrode 1 from the conduction tube 11, and is reversed in the sending direction in the connection space 15, so that the outer discharge part 6 and the inner discharge part 3 are separated. It is fed into the interspace 8 and discharged from the discharge pipe 12 through the discharge hole 12 a from the discharge chamber 14. While the medium flows through the space 8, the medium is decomposed by the silent discharge action of the high voltage applied to the inner and outer discharge units 3, 6 to generate ozone,
The generated ozone flows toward the sealing body 10a on the inflow side while the ozone concentration increases.

If the ozone concentration increases while the medium containing ozone advances in the space 8 to the end of the sealing body 10a on the inflow side, the ozone concentration generally reaches a discharge equilibrium state and the ozone concentration increases to a certain level or more. Then, the vicinity of the downstream end generates a particularly large amount of heat and the temperature rises. However, in this embodiment, the space 8 is connected to the downstream discharge pipe 12.
The entire space is in contact with the space 7 and the conduit 11 over its entire length, and a discharge chamber 14 is provided inside the sealing portion 10a. The discharge chamber 14 is in contact with the conduit 11 on the inflow side.

For this reason, the discharge portion is largely cooled by the medium such as air or oxygen introduced from the outside, especially on the downstream side thereof, so that the temperature rise near the downstream end hardly occurs. For this reason, a discharge equilibrium state is unlikely to occur, the decomposition action by the discharge action is promoted, and ozone is efficiently generated. For example, the temperature near the downstream end of the outer electrode 5 only rises by about 55 ° C. under the condition of a blowing rate of 2 l / min even if the apparatus shown in the drawing is energized continuously at a room temperature of 20 ° C. for 3 hours. Therefore, there is no need for additional cooling in a short-time operation.

It should be noted that the above measured data shows that the low-temperature plasma generator disclosed in Japanese Patent Application No. 11-156584 by the present inventor produced about the same amount of ozone at a blowing rate of 5 l / min, but about less than half. It can be seen that the ozone concentration in the medium is doubled by the small amount of air blow. This is because the medium is introduced into the inner electrode 1 and the medium having the lowest temperature in the inflow-side sealing body is cooled, so that the cooling effect is extremely large.

The low-temperature plasma generator of this embodiment is
There is no need to provide any special cooling means outside the device, and the configuration is extremely simple with the inner discharge portion 3 and the outer discharge portion 6 provided concentrically. The inner discharge portion is inserted and fixed from one sealing body. Since the insertion and fixing method is made detachable by using the screw portion, it can be easily attached and detached. Therefore, at the time of maintenance and inspection, the inner discharge portion can be easily removed, and the inside can be cleaned.

[0022]

As described above in detail, the low-temperature plasma generator of the present invention is provided with an inner discharge portion and an outer discharge portion having an electrode and a dielectric, respectively, concentrically and sealing both ends of these discharge portions. Close with a stopper, connect a conductive tube penetrating through one sealing body to the space inside the inner electrode, allow a medium such as air or oxygen supplied from outside to flow, and invert inside the other sealing body. Since a medium such as ozone is generated by the discharge action while flowing through the space between the inner and outer discharge parts and is discharged from the discharge pipe of one of the sealing bodies, the medium flows through the inner discharge part. By cooling the medium containing ozone in the discharge space with the medium flow, the temperature rise of the dielectric, particularly at the inflow side end, can be suppressed with high efficiency without providing any special cooling means, and high yield can be achieved. Ozone can be generated at a rate The effect is obtained that.

[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 exploded perspective view of an inner discharge unit.

FIG. 4 is a partial perspective view of the inside of a sealing body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner electrode 2, 4 Dielectric 3 Inner discharge part 1 ', 5' Joining member 5 Outer electrode 6 Outer discharge part 7, 8 Space

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G042 CA01 CC03 CC09 CC16 CE04 4G075 AA03 AA42 BA01 BA06 CA15 CA47 DA02 EB27 EB41 EC01 EC06 EC21 EE01 FB02 FB04 FB06 FC15

Claims (2)

[Claims] An inner discharge portion and an outer discharge portion are provided concentrically outside the inner discharge portion with a predetermined space in the radial direction, and both ends are sealed with a sealing body. The inner discharge portion is formed of a cylindrical dielectric. A cylindrical inner electrode is inserted inside, and the outer discharge part is formed by inserting a cylindrical outer electrode outside the cylindrical dielectric, respectively, and a sealing body is formed in the cylindrical dielectric of the inner discharge part. A medium such as air or oxygen is introduced by connecting a conducting tube that penetrates one of them, and the medium is inverted by the other sealing body to flow through the space with the outer discharge portion, and the medium is discharged from the medium by the discharge action between the two electrodes. A low-temperature plasma generator configured to discharge the generated medium from a discharge portion provided in one of the sealing bodies. 2. The low temperature according to claim 1, wherein a thin joining member formed by knitting a material of the electrode as a thread is put on the outside or inside of the electrode of the inside or outside discharge part and is closely inserted into a dielectric. Plasma generator.