JPH09286604A - Electric discharge treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a gaseous ozone generating efficiency by generating creeping discharge over an entire area of a spacing L between linear electrodes on a surface of a dielectric body. SOLUTION: Plural linear electrodes 4 and 4 are arranged at a regular internal L on the surface of the dielectric body 7. A back surface electrode 3 is disposed at a back surface of the dielectric body 7, and high voltage is applied between the linear electrodes 4 and 4 and the back surface electrode 3 from an AC power source 5. The spacing L between the linear electrodes is decided so that (nd) value may be less than 2.2×10<18> cm<-2> a density of a gaseous starting material is (n), discharge length if (d) and L=nd. The creeping discharge is generated over the entire area of the spacing L between linear electrodes 5 and 4 on the surface of the dielectric body 7 by deciding the spacing L in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge treatment device such as an ozone generator for generating ozone from a gas such as air or oxygen by silent discharge.

[0002]

[Prior Art] Conventionally, sterilization, deodorization and decolorization of water and sewer
Ozone is used to deodorize and decolorize industrial wastewater, decolorize pulp, and sterilize medical equipment. As an ozone generator, there is known one having a plurality of electrodes and generating a silent discharge between the plurality of electrodes to generate ozone from an ozone source gas.

[0003]

The conventional ozone generator generates a silent discharge between a plurality of electrodes as described above,
Ozone is generated by this silent discharge. In this case, conventionally, a large capacity and high efficiency ozone generator has been desired, but the technology is not yet developed.

The present invention has been made in consideration of the above points, and an object thereof is to provide a large-capacity and high-efficiency discharge treatment apparatus.

[0005]

The present invention provides a dielectric and a plurality of linear electrodes arranged at regular intervals on the surface of the dielectric, and by a silent discharge generated on the surface of the dielectric,
In an electric discharge treatment device for treating the supplied source gas,
When the distance L between the linear electrodes is n = source gas density, d = discharge length, and L = 2d, the nd value is 2.2 × 10 ¹⁸ cm.
^-2 Discharge treatment device characterized in that it is defined to satisfy the following conditions.

According to the present invention, the spacing L between the linear electrodes is
By determining that the d value satisfies the condition of 2.2 × 10 ¹⁸ cm ⁻² or less, creeping discharge can be generated in the entire space L between the linear electrodes on the dielectric surface.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of an ozone generator according to the present invention.

In FIGS. 1 and 2, an ozone generator as a discharge treatment device is a dielectric 7 made of glass or ceramic, a back electrode 3 provided on the back surface of the dielectric 7 and made of a conductive metal, and a dielectric. On the surface of 7 a constant distance L
And a plurality of linear electrodes 4 and 4 arranged at intervals. Of these, the back electrode 3 is formed as a base material, and the dielectric 7 is coated on the back electrode 3 as a base material.

The back side of the back electrode 3 is cooled by cooling water 10. Further, an AC power supply 5 for applying a high voltage is connected between the electrodes 4, 4 and the back electrode 3,
The back electrode 3 is grounded. Also, the linear electrodes 4, 4
By applying a high voltage from the AC power supply 5 between the rear electrode 3 and the rear electrode 3, a creeping discharge 6 can be generated on the surface of the dielectric 7, and the creeping discharge 6 produces ozone from the ozone source gas.

The interval L between the linear electrodes 4 is, for example, 1.8 mm.
It is defined below. Next, the interval L between the linear electrodes 4 will be described in detail below.

As shown in FIG. 2, when a high voltage is applied between the linear electrodes 4 and 4 and the back electrode 3, electric lines of force generated from the linear electrode 4 to the back electrode 3 through the dielectric 7. A creeping discharge 6 is generated along. In this case, the distance L between the linear electrodes 4
However, as described above, since it is extremely short at 1.8 mm or less, it is possible to generate the creeping discharge in the entire region of the interval L.

In FIG. 2, the linear electrode 4 is symmetrical with respect to the C plane provided at the position of L / 2 which is half the interval L. Therefore, the line of electric force always faces downward on the C plane. Therefore, the creeping discharge 6 is generated from the linear electrode 4 and stops at the position where the C surface and the dielectric 7 are in contact with each other. Therefore, when the distance L between the linear electrodes 4 is as short as 1.8 mm or less, the discharge length d of the creeping discharge 6 generated along the lines of electric force is approximately L / 2.

Next, the operation of the present embodiment having such a configuration will be described.

When a high voltage is applied from the AC power supply 5 between the linear metals 4, 4 and the back electrode 3, a creeping discharge 6 is generated on the surface of the dielectric 7. At this time, ozone is generated from the ozone source gas by supplying ozone source gas such as dry air to the surface of the dielectric 7.

Next, the relationship between the discharge length d, the ozone source gas density n, the electric field E in the creeping discharge 6, and the average energy <e> of electrons will be described with reference to FIG. Generally, the effective discharge initiation electric field E is determined by the product nd of the discharge length d and the density n of the ozone source gas. The average energy <e> of the electrons is determined by the so-called converted electric field E / n obtained by dividing the effective discharge starting electric field E by the density n of the source gas. In FIG. 3, the horizontal axis represents the converted electric field E / n, and the vertical axis represents the average energy <e> of electrons and the nd product. From this, it is possible to show the relationship between the average energy <e> of electrons and the en product.

In FIG. 3, when the nd product is reduced, the converted electric field E / n does not change so much up to nd = 2.2 × 10 ¹⁸ cm ^-2 . However, in a region smaller than this, the converted electric field E / n sharply rises. At this inflection point X, the converted electric field E / n becomes approximately 230 Td, the average energy <e> of the corresponding electrons becomes 7 eV, and the average energy of the electrons falls within the high efficiency region.

By the way, the minimum dissociation energy of the oxygen molecule (O2) to the atom (O) is 6.8 eV, and only electrons having an energy higher than this contribute to the dissociation of the oxygen molecule. The dissociated oxygen atom (O) combines with another oxygen molecule (O2) to become ozone (O3). Since the average energy <e> = 7 eV of electrons corresponding to the inflection point X is higher than the minimum dissociation energy 6.8 eV of the oxygen molecule, if the reduced electric field E / n above the inflection point X is to be obtained. It enables high ozone generation efficiency and ultra-high concentration ozone generation.

As described above, such a condition means that the nd product is 2.2 × 10 ¹⁸ cm ^-2 or less.
When the density n of the ozone source gas at atmospheric pressure and an absolute temperature of 300 K is, for example, 24.5 × 10 ¹⁸ cm ⁻³ , the discharge length d is 0.09 cm = 0.
The area is 9 mm or less. As described above, the discharge length d is approximately half the distance L between the linear conductive electrodes 4 and 4 L / 2.
Therefore, by setting the interval L to 1.8 mm or less, which is twice the discharge length d = 0.9 mm, it is possible to achieve high ozone generation efficiency and ultra-high concentration ozone generation.

In the present embodiment, the case of ozone generation is described, but it is also applicable to a plasma reaction apparatus requiring high electron energy such as smoke exhaust treatment.

By the way, the creeping discharge 6 is generated in the vicinity of the surface of the dielectric 7 as described above, but in order to efficiently remove the heat generated by the creeping discharge 6, it is most preferable to cool the dielectric 7. This is an efficient cooling method. In the present embodiment, as shown in FIG.
By cooling with, the dielectric 7 can be cooled via the back electrode 3. In this case, since the dielectric 7 is coated on the back electrode 3 which is a conductive metal on the back surface of the dielectric 7, even if the dielectric 7 is damaged, the back electrode 3 which is the base exists. Therefore, there is no concern that water, which is a cooling medium, leaks out, and high reliability can be obtained. Therefore, the cooling efficiency can be increased, the gas temperature in the creeping discharge 6 can be suppressed to a low level, and the ozone decomposition efficiency can be improved by preventing the thermal decomposition of ozone, and ultra-high concentration ozone can be obtained. be able to.

Next, referring to FIG. 4, a modification of the present invention will be described. The modification shown in FIG. 4 is one in which an additional dielectric 8 is provided on the dielectric 7 and the linear electrodes 4 and 4, and is otherwise the same as the ozone generator shown in FIG. 4, the same parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

That is, as shown in FIG. 4, an additional dielectric 8 is coated on the dielectric 7 and the electrode 4. The additional electric body 8 is coated on the upper portion of the linear electrode 4, and the linear electrodes 4 and 4 are embedded inside the additional dielectric 8. At this time, the linear electrode 4
When a high voltage is applied between the dielectric 7 and the back electrode 3 to generate the creeping discharge 6, the linear electrode 4 is not directly exposed to the creeping discharge 6, so that spatter deterioration due to the discharge of the linear electrode 4 is caused. Alternatively, there is no change due to ozone oxidation, and long life and high reliability can be obtained.

Next, a further modification of the present invention will be described with reference to FIG. In the modification shown in FIG. 5, the back electrode 3 is removed from the back surface of the dielectric 7, a high voltage is applied from the AC power supply 5 to the linear electrodes 4 and 4, and the dielectric 7 and the linear electrodes 4 and 4 are further applied. 4 is coated with an additional dielectric 8 and is otherwise substantially the same as the ozone generator shown in FIG. 5, the same parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

In FIG. 5, when a high voltage is applied between the linear electrodes 4 and 4, a creeping discharge 6 is generated between the linear electrodes 4 and 4. In this case, since the linear electrodes 4 and 4 are coated with the additional dielectric material 8, spatter deterioration due to discharge or deterioration due to ozone oxidation can be prevented, and long life and high reliability can be obtained.

Next, a further modification of the present invention will be described with reference to FIG. In the modification shown in FIG. 6, a back surface dielectric 3 is provided on the back surface side of the back surface electrode 3, and stacked bodies 4, 3 and 12 including the dielectric material 7, the back surface electrode 3 and the back surface dielectric 12 are formed in a cylindrical shape. Others are shown in Figure 1.
It is almost the same as the ozone generator shown in FIG. 6, the same parts as those of the ozone generator shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, as shown in FIG. 6, a dielectric 7, a back electrode 3 and a back dielectric 1 which constitute an ozone generator.
The laminated body 7, 3, 12 made of 2 is formed in a cylindrical shape. When a high voltage is applied between the linear electrodes 4 and 4 and the back electrode 3 by the AC power supply 5, a creeping discharge 6 occurs on the surface of the dielectric 7.
Occurs. In this case, when the ozone source gas is supplied into the cylindrical dielectric 7, the creeping discharge 6 produces ozone from the ozone source gas.

[0027]

As described above, according to the present invention,
A creeping discharge can be generated over the entire space L between the linear electrodes on the surface of the dielectric. Thus, since the creeping discharge can be generated over the entire space L between the linear electrodes, the processing efficiency of the raw material gas can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a discharge treatment apparatus according to the present invention.

FIG. 2 is a diagram for explaining a gap between linear electrodes.

FIG. 3 is a discharge length, a density of ozone source gas, an electric field,
The figure which shows the relationship with electron average energy.

FIG. 4 is a diagram showing a modified example of the discharge treatment apparatus according to the present invention.

FIG. 5 is a diagram showing a modified example of the electric discharge treatment apparatus according to the present invention.

FIG. 6 is a view showing a modified example of the discharge treatment apparatus according to the present invention.

[Explanation of symbols]

 3 Rear Electrode 5 AC Power Supply 6 Creeping Discharge 7 Dielectric 8 Additional Dielectric 10 Cooling Water 12 Rear Dielectric

Front page continued (72) Inventor Akira Ishii 2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Hamakawasaki Plant (72) Inventor Hideaki Deguchi No. 1 Toshiba-cho, Fuchu, Tokyo Toshiba Fuchu Plant (72) Inventor Yuji Okita 1-24-2 Harumicho, Fuchu-shi, Tokyo Toshiba FA System Engineering Co., Ltd.

Claims (2)

[Claims] 1. An electric discharge comprising a dielectric and a plurality of linear electrodes arranged at regular intervals on the surface of the dielectric, and treating a supplied source gas by silent discharge generated on the surface of the dielectric. In the processing apparatus, the interval L between the linear electrodes is set so that n = source gas density, d = discharge length, L = 2d, and that the nd value satisfies the condition of 2.2 × 10 ¹⁸ cm ⁻² or less. Discharge treatment device characterized by being provided. 2. The discharge processing apparatus according to claim 1, further comprising a back electrode provided on the back surface of the dielectric.