JP2001010808A - Formation of highly oxidative water and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce highly oxidative water containing ozone and the like in excellent electrical efficiency with high productivity by dissolving an oxygen- rich gas in water under high pressure, then lowering the pressure to generate microfine bubbles of the oxygen-rich gas and exposing the microfine bubbles to the pulsed electric discharge. SOLUTION: Water is introduced into a high-pressure tank, an oxygen-rich gas is blown from a high-pressure bomb 6 through an aerator 7 into the water in microfine bubbles so that the oxygen-rich gas is dissolved in the water. At this time, the pressure in the high-pressure tank is measured with a pressure gauge 5 to adjust the pressure to several to several tens atmospheric pressure. The water saturated with oxygen-rich gas is transferred to the low-pressure tank 2, the pressure-reducing valve 9 is opened to reduce the pressure in the low-pressure tank. At this time, the oxygen-rich gas dissolved in the water is supersaturated with the oxygen-rich gas to generate microfine bubbles wholly in the water. High-voltage pulses are applied from the pulse power supply to the electrode 3 to generate ozone whereby the objective high-oxidative water including high concentrations of ozone and/or OH radical is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a purification treatment of sewage containing organic or inorganic harmful substances such as lake water, river water and industrial wastewater, and particularly to a biodegradable harmful organic substance such as dioxin. Highly oxidizing water (high-concentration ozone and / or O) used for detoxification of contaminated water, cleaning, resist stripping, oxide film formation, etc. in semiconductor manufacturing.
H-radical-containing water).

[0002]

2. Description of the Related Art Biological treatment of wastewater containing organic matter (water to be treated) in the presence of activated sludge containing aerobic or anaerobic microorganisms is widely performed. However, in the case of biological treatment alone, when wastewater contains high-biodegradable substances such as high-molecular substances, aromatic compounds, and COD components, the treatment takes a long time and a satisfactory purification effect cannot be obtained. . Further, when the quality of the water to be treated fluctuates, the quality of the obtained purified water also fluctuates, so that purified water having a stable cleanness cannot be obtained.

[0003] Therefore, when treating wastewater containing a hardly biodegradable substance, gaseous ozone is aerated and stirred to generate ozone water, and the above substance is converted into a biologically treatable substance by utilizing the oxidizing activity of ozone. A method of altering is adopted.
As a method of obtaining gaseous ozone at this time, a high voltage is applied to air or oxygen-enriched air sent through an air supply pipe from electrodes provided at both ends of the pipe to perform discharge, thereby converting oxygen to ozone. A method for causing this to occur is known.

[0004] However, this method has a very poor power efficiency, and the gas ozone itself is unstable, and is easily decomposed thermally due to wall contact during pressurization, transportation, or dissolution in water. Is bad and lacks practicality.

As a measure for overcoming such prior art, Japanese Patent Publication No.
Japanese Patent No. 87320 discloses that by discharging in a COD component-containing wastewater, ozone or active oxygen species (OH radical) is directly generated in water from dissolved air (oxygen), or ultraviolet light is generated as a promoter. A method is disclosed in which the BOD / COD ratio is increased and the wastewater is converted into wastewater that is easily biodegraded before biological treatment. However, in reality, it is difficult to realize stable underwater discharge over a wide area, and thus it has not been put to practical use.

As one method for realizing a wide-area discharge, there is a discharge using a high-speed pulse as disclosed in Japanese Patent Application Laid-Open No. 9-299785. In addition, it has been found that underwater discharge progresses with microbubbles existing to some extent in water as nuclei, and Japanese Patent Application Laid-Open No. 5-319807 discloses that air and oxygen are actively and efficiently supplied between electrodes. A method of generating microbubbles by aeration has been proposed.

However, at present, no technology has been established that can secure a practical level of oxidation performance (ozone and / or OH radical concentration) by underwater discharge under stable power efficiency and productivity.

[0008]

In order to directly generate highly oxidizable water by underwater discharge, it is important to realize a wide area and stable underwater discharge. For this purpose, uniformly sized microbubbles serving as the nucleus of the discharge are generated uniformly and efficiently in the entire discharge space, and the bubbles themselves are mainly composed of oxygen, which is a source of oxidization. Has the property that the high-voltage electric field spreads uniformly throughout the discharge space without local concentration, and that the discharge does not converge and concentrate,
Is important.

Under the circumstances described above, the present invention is based on the above-mentioned important points, and provides a highly oxidizing water containing a high concentration of ozone or OH radical which exhibits a practically sufficient level of oxidation performance by underwater discharge. The object was to provide a method and an apparatus which can be obtained with improved power efficiency and productivity.

[0010]

Means for Solving the Problems The method of the present invention that can achieve the above object is to dissolve an oxygen-rich gas in water under high pressure and then reduce the pressure.
The gist is that the dissolved oxygen-rich gas is generated as fine bubbles in the water and the fine bubbles are exposed to pulse discharge to generate highly oxidizing water having a high dissolution amount of ozone and / or OH radicals. ing.

If the method is applied to wastewater containing organic or inorganic harmful substances as water to be treated by this method, wastewater with high ozone and / or OH radical dissolution can be produced by the above treatment. Purification efficiency by biological treatment can be enhanced by promoting oxidation and decomposition of hard-to-degrade biodegradable harmful substances, and pure water or deionized water is used as the water to be treated. Highly oxidizing water in which radicals are dissolved abundantly can be effectively used as highly oxidizing cleaning water in semiconductor production, or as an agent for stripping resist or forming an oxide film on the surface of various metal materials.

The apparatus of the present invention has been developed as an apparatus for producing the above-mentioned highly oxidizing water. The apparatus comprises a high-pressure tank for dissolving oxygen-rich gas in water under high pressure, And a low-pressure discharge tank that receives the supply of water in which the oxygen-rich gas is dissolved from the high-pressure tank, and a pulse power supply is connected to the electrodes arranged in the low-pressure discharge tank. Has features.

In another apparatus according to the present invention, an aeration / discharge tank provided with an aeration means and a pulse discharge means is provided with an oxygen-rich gas supply means, a water supply means, and a pressure control means. Dissolve oxygen-rich gas in water under high pressure, then reduce pressure to generate oxygen-rich gas bubbles and discharge pulse current, and pressurize and dissolve oxygen-rich gas in water in one treatment tank. It is characterized in that the generation of the oxygen-rich gas bubbles and the pulse discharge can be sequentially performed by decreasing the pressure.

In practicing the present invention, if a rare gas such as argon or xenon is dissolved in addition to oxygen as the oxygen-rich gas, the rare gas contained in the microbubbles generated at the time of pressure reduction will cause a pulse discharge. This is preferable because the generation of ultraviolet rays is enhanced, and the generation efficiency of highly oxidizing water is further increased. Further, if a cooling mechanism is provided in a tank for dissolving the oxygen-rich gas under high pressure, the saturation solubility of the oxygen-rich gas in water can be increased. And / or OH radical generation rate is further preferred.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as described above, first, oxygen-rich gas is dissolved abundantly in water under high pressure, and then the pressure is reduced to dissolve the dissolved oxygen-rich gas into the water. While generating as air bubbles,
By exposing these microbubbles under pulse discharge, ozone and / or OH radicals are efficiently generated, thereby producing a highly oxidizing water having a high dissolution amount of these oxidizing active components, According to this method, fine bubbles can be uniformly generated in the entire water to be treated in the pulse discharge process, and the high-voltage pulse discharge is performed in synchronization with the generation of the oxygen-rich gas bubbles due to the decrease in pressure. Ozone can be generated directly by exciting the enzyme therein.

The microbubbles generated at the time of pressure reduction have an inner surface area larger than the volume thereof, so that a much larger amount of generated ozone can be dissolved in water than in the ordinary aeration / diffusion method. Furthermore, ultraviolet light is generated together with ozone due to the pulse discharge in the fine bubbles, and the action promotes the generation of OH radicals in the water near the bubble surface.

That is, in the present invention, after the oxygen-rich gas is dissolved abundantly in water in the treatment tank, the pressure is reduced to generate fine bubbles of the oxygen-rich gas, and a high-voltage pulse discharge is performed. With a large number of oxygen-containing microbubbles generated as a nucleus, a discharge occurs in the whole area of the wide area water, and the generation reaction of ozone and OH radicals from oxygen by discharge energy in each microbubble progresses efficiently, as a result Generation of highly oxidizing water will be performed with extremely high efficiency.

Hereinafter, the method and apparatus of the present invention will be described.
It will be described in detail with reference to drawings showing specific examples,
The illustrated examples below are of course not limiting in nature of the present invention, and may be implemented with appropriate modifications within a range that can be adapted to the spirit of the invention described above. Included in the range.

FIG. 1 illustrates an apparatus for producing highly oxidizing water according to the present invention. In the figure, 1 is a high-pressure tank, 2 is a low-pressure tank, 3 is a discharge electrode, and 4 is a pulse power source (high voltage pulse potential applying means). ), 5
Indicates a pressure gauge.

[0020] In conducting the preparation of highly oxidizing water using the device, and introducing water into the high-pressure tank 1 from the valve V _1, the oxygen-rich gas from the high pressure oxygen cylinder 6 through the valve V ₂ and aeration device 7 Dissolve by blowing into water in the form of fine bubbles. In this case, while measuring the pressure in the high pressure tank 1 by the pressure gauge 5 is adjusted to a pressure of usually about several atmospheres to several tens atm by the pressure regulating valve V _5. At this time, if an arbitrary cooling means is provided in the high-pressure tank 1 so that the internal water can be cooled, the amount of saturated oxygen-rich gas dissolved in water can be further increased. This is preferable because the time for which the supersaturated state is maintained during depressurization can be extended.

As the oxygen-rich gas, it is possible to use oxygen. Of course, it is also possible to use air, and when it is put to practical use on an industrial scale, oxygen which is cost-effective is preferably used. You. Also, if a small amount of a rare gas (argon, xenon, etc.) is mixed in the oxygen-rich gas, ultraviolet rays are generated together with ozone at the time of the pulse discharge performed in the next step, and the action causes the generation of OH radicals at the interface of the fine bubbles. As a result of promoting the generation, the generation efficiency of the highly oxidizing water can be further increased, which is preferable.

Thereafter, the water in which the oxygen-rich gas is dissolved in a saturated state is transferred from the valve V ₃ to the low-pressure tank 2. And
When the pressure reducing valve 9 is opened to lower the pressure in the low-pressure tank 2, the oxygen-rich gas dissolved in the water to be treated under pressure becomes supersaturated, and as fine bubbles (several to several tens of microns in diameter) throughout the water in the low-pressure tank 2. appear.

Before or after the timing of the generation of the fine bubbles,
When a high voltage pulse is applied to the electrode 3 from the pulse power supply 4,
Underwater discharge grows and expands with fine bubbles as nuclei. At that time, the silent discharge generated in the microbubbles excites the oxygen present in the bubbles to generate ozone.Since the microbubbles have a large internal surface area in comparison with the volume, the generated ozone is quickly generated in the water to be treated. Blends into

Therefore, in the supersaturated state of the water to be treated before the generation of the fine bubbles in the low-pressure tank 2, more preferably, the generation of the fine bubbles is completed by the decompression and the size of the microbubbles is increased by the average diameter. By incorporating a control system for applying a high-voltage pulse potential to the electrodes at the timing before the above, it is possible to efficiently and efficiently generate ozone and OH radicals by pulse discharge.

In the former case, when a high voltage pulse is applied in the saturated state of the water to be treated before the formation of the fine bubbles, the fine bubbles are still small when the high voltage pulse is applied. Even in this case, bubbles are generated and grown along the discharge tree formed in the water to be treated after the application, and as a result, a sufficient amount of fine bubbles are formed. In the present invention, the fine bubbles exposed to the discharge pulse are not limited to those generated only by lowering the pressure after dissolving the oxygen-rich gas under high pressure. Microbubbles generated by stimulation by electric discharge are also included.

If a small amount of a rare gas is mixed in the oxygen-rich gas, the amount of ultraviolet rays generated during pulse discharge increases due to the presence of the rare gas as described above, and the OH radical generation reaction at the interface of the microbubbles occurs. This is preferable because water is promoted and the amount of dissolved OH radicals is increased to produce water having higher oxidation performance.

[0027] ozone and / or OH radicals large amount of dissolved but water is withdrawn from the valve V _4. As described above, when water is used for wastewater containing, for example, a hardly biodegradable harmful substance, the harmful substance is oxidatively decomposed into a readily biodegradable substance by increasing the amount of dissolved ozone and / or OH radicals. The wastewater can be purified with high efficiency by the subsequent biodegradation treatment.

The highly oxidized water obtained by using pure water or deionized water as the water can be effectively used as, for example, cleaning water used in the semiconductor manufacturing field, etc. It can be effectively used as an oxidizing agent for forming an oxide film on a metal material or the like.

FIG. 2 shows another embodiment of the apparatus according to the present invention.
The high-pressure tank 1 in the apparatus shown in FIG.
The low pressure tank 2 can be used as one aeration / discharge tank 10
This is an example. That is, in this device, one aeration / discharge tank
10, a water supply valve V ₁For oxygen-rich gas supply
High pressure oxygen cylinder 6, valve V_TwoAnd aerator 7, pal
Electrode 3, pressure gauge 5, pressure regulating valve 9, high
Oxidizing water discharge valve V_FourAnd so on.

When using this device,
Water was fed from a valve V ₁ to the aeration-discharge tank 10 are dissolved is blown from the high-pressure oxygen cylinder 6 in the water to be treated an oxygen-rich gas through a valve V ₂ and aeration device 7 in form fine cells. At this time, the pressure in the aeration / discharge tank 10 is measured by a pressure gauge 5
While measuring by adjusting any pressure by the pressure regulating valve V _5.

After the dissolution of the oxygen-rich gas is completed, the supply of the oxygen-rich gas is stopped, and the pressure in the tank 10 is reduced by operating a pressure reducing pump (not shown) connected to the pressure regulating valve 9. Then, the oxygen-rich gas dissolved in the water under pressure becomes supersaturated and vaporizes in the water, resulting in fine bubbles.
(Several to several tens of micron diameter) throughout the entire region.
When a high-voltage pulse current is applied from the pulse power supply 4 to the submerged discharge, the underwater discharge grows and expands around the microbubbles as in the case of FIG. 1, and the silent discharge generated in the microbubbles reduces the oxygen inside the microbubbles. When excited, ozone is generated, and the generated ozone quickly dissolves into the water to be treated.

At this time, a cooling mechanism is provided in the tank 10,
If the internal temperature can be lowered when dissolving the oxygen-rich gas, the amount of oxygen-rich gas dissolved under pressure can be increased, and if a rare gas is mixed in the oxygen-rich gas, OH radicals are generated. The amount can be increased, and the oxidation activity of the resulting highly oxidizing water can be further increased, as in the case of FIG. And ozone and / or
Or OH radicals took the dissolved water may be extracted from the up-valve V _4.

As the material of the electrode used in the present invention, any material having conductivity such as metal or conductive ceramic can be used without any particular limitation. Particularly preferred as the cathode is stainless steel or thorium. It is preferable to use a material having low corrosion resistance and a small amount of deposits, such as an alloy, and a material having little loss during discharge, such as a Cu-Zn-Fe alloy or a thorium alloy, as the anode.

The conditions for the pulse discharge are not particularly limited.
As an example of a standard preferable condition, the electrode interval is 2 mm or more and 50 mm or less, preferably 15 mm or more and 30 mm or less, and the applied voltage is 5 kV or more and 100 kV.
Or less, preferably 20 kV or more and 50 kV or less, the frequency of the pulse voltage is 30 Hz or more and 1 MHz or less, preferably 60 Hz or more and 120 Hz or less, and the pulse width is 5 nanoseconds or more and 1 millisecond or less, preferably 1 microsecond or more and 10 μs or more.
0 microseconds or less. When a pulse voltage having such a pulse width is used, power consumption can be reduced as compared with the case where a voltage is continuously applied. In addition, an effect of homogenizing the electric field can be expected due to the polarization effect of the large dielectric constant (ε _r = 80) of the water molecule.

The present invention can be effectively used as a preliminary treatment of wastewater containing organic substances or inorganic harmful substances containing a hardly biodegradable harmful substance as described above, and in particular, wastewater containing a hardly biodegradable organic substance, or The effect is more effectively exhibited by applying to wastewater in which the organic matter content fluctuates.

Examples of the hardly biodegradable organic substance include natural or synthetic polymer compounds such as cellulose, humic substances, surfactants, pigments, rubbers, resins, and the like; benzene, toluene,
Aromatic compounds such as xylene and phenol; aldehyde compounds such as acetaldehyde and crotonaldehyde; and oils and fats, higher fatty acids, and other COD components. Specific examples of these wastewaters include chemical factory wastewater,
Wastewater from a chemical factory, wastewater from a food factory, wastewater from an oil and fat factory, wastewater from a pulp factory, other industrial wastewater, river water, lake water and the like.

The high molecular compounds contained in these wastewaters are reduced in molecular weight by underwater discharge, and benzene, toluene,
Aromatic compounds such as xylene and phenol are degraded to organic acids such as oxalic acid and formic acid and become biodegradable.Furthermore, easily biodegradable organic substances are further degraded by reducing the molecular weight and decomposing. Is improved.

[0038]

The present invention is constructed as described above. After dissolving the oxygen-rich gas under a high pressure and then reducing the pressure, fine oxygen-rich gas bubbles are generated. As a result, a highly oxidizing water containing a high concentration of ozone and OH radicals can be produced at a high efficiency. Therefore, if water containing an organic substance is used as the water, particularly, the water to be treated containing a non-biodegradable organic substance, the non-biodegradable organic substance can be efficiently solubilized or made harmless by generated ozone or OH radicals. .

Highly oxidizing water generated by using pure water or deionized water can be used for cleaning and formation of an oxide film in the production of semiconductors, and requires an agent such as hydrofluoric acid which causes environmental destruction. It can be used effectively as a processing technology that does not.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view illustrating a highly oxidizing water generator according to the present invention.

FIG. 2 is a schematic explanatory view illustrating another highly oxidizing water generator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High pressure tank 2 Low pressure tank 3 Electrode 4 Pulse power supply 5 Pressure gauge 6 Oxygen cylinder 7 Aerator 9 Pressure reducing valve 10 Aeration / discharge tank

Continued on the front page (72) Inventor Yoshihiro Yokota 1-5-5 Takatsukadai, Nishi-ku, Kobe City Inside Kobe Steel Research Institute, Kobe Steel Co., Ltd. (72) Inventor: Adult 2-3-3 Shinhama, Araimachi, Takasago City, Hyogo Prefecture No. 1 Kobe Steel, Ltd. Takasago Works (72) Inventor Kazuhiko Asahara 1-5-5 Takatsukadai, Nishi-ku, Kobe F-term in Kobe Research Institute, Kobe Steel Co., Ltd. F-term (reference) 4D050 AA01 AA12 BB01 BB02 BB20 BC02 BD02 BD03 BD04 BD06 BD08 4D061 DA01 DA08 DB07 DB19 EA15 EB07 FA16 FA20 4G042 CA01 CB01 CE01 4G075 AA15 AA37 BA05 BA06 CA05 CA15 CA51 EB01 EC21

Claims (4)

[Claims] 1. Dissolving an oxygen-rich gas in water under high pressure and then reducing the pressure to generate dissolved oxygen-rich gas as fine bubbles in the water and exposing the fine bubbles under pulse discharge. A method for producing highly oxidizing water, which comprises producing highly oxidizing water having a high solubility of ozone and / or OH radicals. 2. The method according to claim 1, wherein the water is a wastewater containing an organic or inorganic harmful substance, and the wastewater treatment efficiency is increased by producing a wastewater having a high ozone and / or OH radical dissolution amount. . 3. A high-pressure tank for dissolving an oxygen-rich gas in water under high pressure, and a pressure maintained lower than the high-pressure tank.
A low-pressure discharge tank for receiving a supply of water in which oxygen-rich gas is dissolved from the high-pressure tank, wherein a pulsed power supply is connected to an electrode disposed in the low-pressure discharge tank. apparatus. 4. A highly oxidizing water generating apparatus characterized in that an aeration / discharge tank provided with aeration means and pulse discharge means is provided with oxygen-rich gas supply means, water supply means and pressure control means.