JP4126382B2 - Ozone generator and ozonized gas production method - Google Patents

Description

The present invention relates to an ozonized gas production apparatus used for water and sewage treatment, pulp bleaching treatment, sterilization treatment, deodorization treatment, and the like, and a method of operating the device. Moreover, it is related with the ozonized gas manufacturing method with a high density | concentration.

Conventionally, ozonized gas has been used for various treatments such as water and sewage treatment, pulp bleaching treatment, sterilization treatment, and deodorization treatment. As a method for producing the ozonized gas, a silent discharge method in which air or oxygen gas is used as a source gas and an AC high voltage is applied to discharge while supplying the source gas between electrodes of opposing electrodes arranged with a dielectric is used. Manufacturing methods are known. This method is economical compared to other ozone production methods, and since ozone gas having a high concentration can be efficiently produced by using a raw material gas containing oxygen gas with high purity, in recent years ozonization It is often used as a method for producing gas.

When trying to produce ozonized gas by this silent discharge method, it is known that the distance between the electrodes of the opposing electrodes, more precisely, the discharge gap length between the electrodes has a great influence on the concentration of ozone generated. Yes. In other words, if the energy applied between the electrodes is the same, it is necessary to shorten the discharge gap length in order to improve the ozone concentration.
On the other hand, in order to supply ozonized gas in large quantities, the ozone generator has been enlarged. An electrode used in the silent discharge method is also large, and an electrode having a length of 0.5 m or more is frequently used. The discharge gap length of the electrode is currently 1 mm or less with respect to 0.5 m of the discharge electrode. In order to improve the ozone concentration of the ozonized gas to be generated, the gap length may be shortened to, for example, about 0.2 mm. However, the discharge gap length of an electrode having a length of 0.5 m or more is set to 0.5 mm. It is not realistic to set it to 2 mm. In particular, setting the discharge gap length of the electrode to 0.2 mm with respect to the discharge power of 0.5 m in a commonly used coaxial cylindrical tube is not a practical method in view of the yield.

Further, if a large amount of energy is input between the opposing electrodes, an ozonized gas having a high concentration can be produced. However, this method is not economical and cannot be a practical method.
In addition, when the ozonized gas is produced continuously for a long time by the silent discharge method using high-purity oxygen gas, the problem that the ozonized gas concentration decreases with the passage of time becomes clear, and in order to solve the point, A technique for producing ozonized gas by adding air or nitrogen gas to a source gas containing oxygen has been disclosed by the present applicant. That is, in Patent Document 1, high purity oxygen gas is used as a raw material gas for producing ozonized gas, and when the raw material gas is mixed with air at a rate of 3 vol%, the generated ozone and nitrogen react to generate. It is disclosed that the compound binds to water molecules adsorbed on the electrode surface, and as a result, the decrease in the concentration of ozonized gas is suppressed.
JP 2001-172005 A

Accordingly, an object of the present invention is to provide a method for obtaining an ozonized gas having a high concentration and an efficient method and an apparatus for carrying out the method. Another object of the present invention is to provide a method for efficiently obtaining a high-concentration ozonized gas using a counter electrode in which the gap length between discharge electrodes remains the same, and an ozone generator for carrying out the method. It is in providing the operating method of an apparatus.

In order to achieve the above-mentioned problems, the present inventors have conducted intensive research and have reached the following invention.
Patent Document 1 discloses a technique for producing ozonized gas by using high-purity oxygen and mixing this raw material gas with air. However, in this case, air is mixed at a rate of 3 vol%. Since it is described that it is preferable and 3 vol% of air is converted to 2.4 vol% of nitrogen gas, it is different from the mixing ratio of nitrogen gas defined by the present invention, and the purpose of mixing nitrogen gas is also different. Patent Document 1 is not related to the present invention.

That is, the invention according to claim 1 of the present invention supplies an AC high voltage between the electrodes while supplying a source gas mainly composed of oxygen between the electrodes of the counter electrode having a dielectric disposed on at least one of the electrodes. In the method of producing an ozonized gas by applying and generating electric discharge, a raw material gas in which 0.1 to 0.6 vol% of nitrogen is mixed with a raw material gas mainly composed of oxygen, and the gas pressure is 0.1 to It is a method for producing an ozonized gas characterized by being 0.2 MPa.

The invention according to claim 2 of the present invention is the method for producing ozonized gas according to the invention of claim 1, wherein the discharge gap interval is 0.3 mm to 0.5 mm.

Hereinafter, the present invention will be described in detail.
The electrode structure of the present invention is composed of opposing electrodes in which a dielectric is disposed on at least one of the electrodes, and can generate an electric discharge by applying an alternating high voltage, and the raw material gas of ozonized gas is used between the electrodes. Take a structure that can be supplied to.
As the opposing electrode, an electrode normally used in an ozone generator may be used. For example, a high voltage electrode and a ground electrode are arranged in a state of maintaining a constant interval. A typical counter electrode is a coaxial cylindrical tubular electrode having a cross-sectional structure as shown in FIG. The material constituting the electrode is not particularly limited, and is constituted by a general material.
In the present invention, it is necessary to dispose a dielectric on the surface of at least one electrode, but it is preferable that a dielectric be disposed on both electrodes. The dielectric is not particularly limited as long as it is a general material, but for example, glass is used.

The two electrodes are arranged so as to maintain a constant distance. That is, as the discharge gap interval of the ozone generator is narrower, higher concentration of ozone can be obtained. However, considering the manufacturing difficulty, the optimum value of the discharge gap interval is in the range of 0.3 to 0.5 mm.
It is desirable to provide cooling means on at least one or both of these electrodes to absorb the generated heat. In particular, the internal electrode tends to become high temperature, so the cooling effect is great. The cooling means is not particularly limited as long as it is a general means, but it may be any means as long as it purifies and supplies at least the cooling water necessary for the ozone generator. Although industrial water may be used for cooling the ground electrode, it is desirable to use cooling water with reduced electrical conductivity for cooling the high voltage electrode in order to prevent leakage of electric power due to the cooling water. A heat exchanger is usually used for heat exchange with the outside of the cooling water.

In the present invention, an alternating high voltage is applied between the electrodes to form a discharge in the discharge space. The raw material gas that passes through the discharge space changes to an ozonized gas. A general method may be used as a method of applying the alternating high voltage.
An ozone generating raw material gas is supplied between the electrodes in the electrode structure or to the discharge space. It is advantageous to use high-purity oxygen gas as the source gas. In order to obtain high-purity oxygen gas, typically, an adsorption-type oxygen production apparatus or liquid oxygen equipment is used. The adsorption-type oxygen production apparatus is an apparatus that obtains oxygen-enriched air having an oxygen concentration of 90% or more by adsorbing nitrogen or carbon dioxide in the air with an adsorbent. The liquid oxygen equipment is equipment for obtaining high-purity oxygen gas that is vaporized from liquid oxygen.
Nitrogen gas is mixed with this oxygen gas, but it is sufficient that the gas is mixed at a predetermined ratio before entering the ozone generating tube, and the mixing means is not particularly limited, The obtained gas source may be liquid oxygen and liquid nitrogen, or may be a gas cylinder.

  When high purity oxygen gas supplied from a liquid oxygen facility is used as a raw material gas for an ozone generator, the oxygen purity is usually 99.6% or more. Most of the components corresponding to 0.4% or less other than oxygen are argon, and nitrogen is present at 0.01% or less. In the experimental conditions where the results shown in FIG. 1 are obtained, high-purity oxygen gas obtained from a liquid oxygen source as described above is used as the source gas. Since the nitrogen gas component is hardly contained in the oxygen gas obtained from the liquid oxygen source as described above, the nitrogen gas content in the raw material gas is indicated by the amount of nitrogen gas added.

In the present invention, it is important to mix 0.1 to 0.6 vol% of nitrogen gas with oxygen gas. This is one of the features of the present invention. That is, it was found that when the oxygen gas as the raw material gas was mixed with 0.1 to 0.6 vol% nitrogen gas, the generated ozone concentration was remarkably improved to about 14% (see FIG. 1).
The technology for producing ozonized gas using electric power with high energy cost as the energy source is mainstream, and in view of the current technology which is an extremely difficult technical field to increase the ozone concentration by 10% or more, as in the present invention, 14 It can be said that the ozone concentration can be increased by about%, which is an extremely excellent effect.
It is apparent from FIG. 4 that the ozone concentration generated increases as the gap length between the discharge electrodes becomes narrow, and that it is extremely difficult to increase the ozone concentration by about 10%. In other words, when the gap length between the discharge electrodes is 0.3 mm, the generated ozone concentration becomes maximal when the input power to the discharge electrodes is about 65%, and power is supplied between the discharge electrodes to increase the ozone concentration. Even if it is added, the ozone concentration never increases. However, when the gap length between the discharge electrodes is narrowed to 0.2 mm, the ozone concentration can be increased, and when the input power is about 80%, it increases about 1.15 times.
From these facts, it can be seen that it is extremely difficult to increase the ozone concentration by 10% or more, avoiding the difficulty of narrowing the gap length between the discharge electrodes, and changing the nitrogen gas to 0.1% oxygen gas. It can be said that the present invention capable of increasing the ozone concentration with a simple configuration of mixing ~ 0.6 vol% is extremely practical.

According to the present invention, it is possible to provide an ozone production technique in which the generated ozone concentration is improved. That is, it is possible to increase the ozone concentration by about 14% by mixing oxygen gas with 0.1 to 0.6 vol% nitrogen gas and performing a simple operation of setting the gas pressure to 0.1 to 0.2 MPa. It has become possible. This method is a method that makes it possible to improve the ozone concentration without having to change the electrode that is currently used, and since it does not require more energy than the energy currently used, it can be said to be an economical method. Moreover, since it can be said that it is a technique that can efficiently produce ozone, it is extremely practical.
The ozonized gas having a high concentration can be used in a wide range of fields such as water and sewage treatment, pulp bleaching treatment, sterilization treatment, and deodorization treatment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments.
FIG. 2 is a schematic view showing an example of an electrode structure in the ozone generator of the present invention.
This electrode structure has a structure in which the high voltage electrode 1 and the ground electrode 2 are opposed to each other, and the dielectrics 3 are arranged on the surface on the discharge space side. The source gas passes from the source gas In 10 through the discharge space 4 formed by the high voltage electrode 1 and the installation ground electrode 2 and flows to the ozonized gas out 11. An alternating high voltage is applied between both electrodes to form a discharge in the discharge space 4 to change the source gas into an ozonized gas.

FIG. 3 is a diagram showing an ozone production flow using the ozone generator of the present invention.
A raw material gas mainly composed of oxygen is supplied from the oxygen production facility 20 to the ozone generator 24 through the flow meter 22. Nitrogen gas is mixed with the raw material gas mainly composed of oxygen from the nitrogen gas production device 21 through the flow meter 23 and supplied to the ozone generator 24. In the ozone device, an alternating high voltage is applied between the counter electrodes (not shown), a discharge is formed in the discharge space (not shown), and the raw material gas passing through the space changes to an ozonized gas. Each of the electrodes constituting the counter electrode of the ozone generator is cooled by cooling water from the cooling device 25. The ozonized gas is injected from the ozone generator 24 through an ozone meter 26 into a device that requires ozone. The excess ozonized gas is decomposed in the ozonolysis tower 27 and released into the atmosphere.

Ozonized gas was manufactured using the ozone generator which has the said electrode structure. The ozone generator has a discharge gap interval of 0.4 mm, and both of the pair of discharge electrodes are covered with a dielectric and cooled with cooling water of about 10 ° C. The raw material gas to the ozone generator, gas pressure is supplied in 0.18 M Pa. The result is shown in FIG. In FIG. 1, the horizontal axis indicates the amount of nitrogen added (volume ratio to oxygen), and the vertical axis indicates the ozone generation concentration normalized based on the ozone concentration obtained when the nitrogen gas addition amount is 0 vol%.

It can be read from the graph that the ozone generation concentration is improved by adding nitrogen gas to the source gas. Improvement of ozone generation concentration by adding nitrogen gas depends on the amount of nitrogen gas added. When the amount of nitrogen gas added to the raw material gas is 0.05 to 2.0 vol%, the ozone generation concentration obtained when nitrogen is not added is obtained. On the other hand, high concentration ozone of 1.1 times or more is obtained.
Further, it can be seen that when the nitrogen gas addition amount is 0.1 to 0.6 vol%, the generated ozone concentration is most improved, and is improved by about 14% with respect to the reference value. The improvement due to the addition of nitrogen gas is the optimum value, and the addition of nitrogen exceeding 0.6 vol% increases the ozone generation concentration relative to the reference value, but this concentration tends to gradually decrease.
The optimum gas pressure at this time is 0.2 MPa when the discharge gap interval is 0.3 mm, and 0.1 MPa when the discharge gap interval is 0.5 mm. Further, in contrast to the case where only the liquid oxygen source is used as the source gas, the range of the amount of nitrogen added to obtain a high ozone output concentration by adding nitrogen does not depend on the range of the discharge gap interval.

  The result shown in FIG. 1 is a result of the electrode configuration in which the dielectric is arranged on both of the electrodes shown in FIG. 2, but also when the dielectric is arranged on one of the opposing electrodes (not shown) The same can be said. Although the electrode configuration shown in FIG. 2 has a silent discharge type structure, although not shown, the same effect can be obtained in a creeping discharge type structure, in which nitrogen is added to a raw material gas supplied to an ozone generator. The effect can be obtained similarly regardless of the electrode shape and method.

From the above description, the present invention can also be described as follows.
(1) While supplying a raw material gas mainly composed of oxygen and mixed with 0.1 to 0.6 vol% of nitrogen into a space including a counter electrode in which a dielectric is disposed on at least one electrode, an alternating current is provided between the electrodes. A method for producing an ozonized gas, wherein a high voltage is applied to generate a discharge.
(2) A structure in which a dielectric is disposed on at least one of the electrodes arranged opposite to each other, and discharge is performed by applying an alternating high voltage while supplying a source gas mainly composed of oxygen therebetween. In the operation method of the ozone generator having the electrode structure to be generated,
A method for operating an ozone generator, wherein nitrogen gas is mixed in an amount of 0.1 to 0.6 vol% in the raw material gas introduced into a discharge section in the ozone generator.
(3) In the method for operating an ozone generator according to (2), ozone generation characterized by supplying a raw material gas in which 0.1 to 0.6 vol% of nitrogen gas is mixed with a raw material gas mainly composed of oxygen. How to operate the device.
(4) Opposite electrodes in which a dielectric is disposed on at least one of the electrodes, source gas supply means for supplying a source gas mainly composed of oxygen between the electrodes, and applying an alternating high voltage to generate a discharge In the ozone generator having AC high voltage application means,
An ozone generator characterized by mixing 0.1 to 0.6 vol% of nitrogen gas in a raw material gas mainly composed of oxygen introduced into a discharge part in the ozone generator.
(5) The ozone generator according to (4), further comprising a cooling means on at least one of the electrodes.

It is a figure which shows the change of the generated ozone density | concentration by the nitrogen gas addition amount to the source gas which has oxygen as a main component. It is the schematic which shows an example of the electrode structure in the ozone generator of this invention. It is a figure which shows the ozone manufacturing flow using the ozone generator of this invention. It is a figure which shows the gap length dependence between discharge electrodes of ozone concentration.

Explanation of symbols

1: High voltage electrode 2: Installation electrode 3: Dielectric material 4: Discharge space 10: Source gas In (inlet)
11: Raw material gas Out (exit)
20: Liquid oxygen equipment 21: Nitrogen gas production device 22: Flow meter 23: Flow meter 24: Ozone generator 25: Cooling device 26: Ozone meter 27: Ozone decomposition tower 29: Device that requires ozone

Claims (2)

While supplying a source gas mainly composed of oxygen between the electrodes of the counter electrode in which a dielectric is disposed on at least one electrode, an alternating high voltage is applied between the electrodes to generate an electric discharge to produce ozonized gas And a raw material gas in which 0.1 to 0.6 vol% of nitrogen is mixed with a raw material gas containing oxygen as a main component, and the gas pressure is 0.1 to 0.2 MPa. How to manufacture. The method for producing ozonized gas according to claim 1, wherein a discharge gap interval is 0.3 mm to 0.5 mm.

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