JP2020186152A - Ozone generator - Google Patents

Abstract

To provide an ozone generator capable of efficiently generating ozone.SOLUTION: An ozone generator for generating ozone used for purifying exhaust gas comprises a decomposition part for decomposing at least a part of moisture contained in a raw material gas. The ozone generator includes an ozone generation part for generating ozone by using a raw material gas in which water is decomposed in the decomposition part. The decomposition part includes a flow passage for the raw material gas, at least part of which has a photocatalyst. The decomposition part includes a light source part for irradiating the photocatalyst with light.SELECTED DRAWING: Figure 2

Description

The techniques disclosed herein relate to ozone generators.

A technique using ozone generated by an ozone generator is known to purify the exhaust gas of a car or the like. For example, Patent Document 1 discloses a related technique.

Japanese Unexamined Patent Publication No. 2004-105811

If the raw material gas used to generate ozone in the ozone generator contains water, the water will inhibit the production of ozone or decompose the generated ozone, resulting in a decrease in the amount of ozone produced. .. In particular, when the outside air is used as the raw material gas in an in-vehicle environment, the raw material gas contains water, which is a problem. The present specification provides a technique capable of efficiently supplying ozone.

One embodiment of the ozone generator disclosed in the present specification is an ozone generator that generates ozone used for purifying exhaust gas. The ozone generator includes a decomposition unit that decomposes at least a part of the water contained in the raw material gas. The ozone generator includes an ozone generating unit that generates ozone using a raw material gas in which water is decomposed in the decomposition unit. The decomposition section is a flow path for the raw material gas, and includes a flow path in which a photocatalyst is arranged at least in part. The decomposition unit includes a light source unit that irradiates the photocatalyst with light.

The photocatalyst can decompose the water contained in the raw material gas into OH, hydrogen, oxygen, or their ionic species / radicals. Even if these decomposition products are contained in the raw material gas, the decrease in ozone production can be suppressed. Therefore, it is possible to suppress a decrease in ozone generation ability by promoting decomposition of water contained in the raw material gas by catalytic action.

At least a part of the flow path may be provided with uneven portions. The photocatalyst may be arranged on the surface of the uneven portion. Details of the effect will be described in Examples.

The light source unit may be a light emitting diode. The light source unit may generate light having an intensity distribution having a wavelength biased in the vicinity of the absorption peak wavelength of the photocatalyst. Details of the effect will be described in Examples.

The decomposition unit may further include a light guide plate for surface-irradiating the entire photocatalyst with the light emitted from the light source unit. Details of the effect will be described in Examples.

Photocatalysts are titanium oxide (TIO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), strontium titanate (SrTiO ₃ ), tantalum nitride (Ta ₃ N ₅ ), acid At least one of tantalum nitride (TaON) may be contained.

The concentration of ozone generated by the ozone generation unit may be 100 ppm or more.

It is a block diagram of an exhaust gas purification system 1. It is a bird view schematic diagram of a photocatalyst reactor 100. It is a bird view schematic diagram of the ozone generation reactor 200.

(Configuration of exhaust gas purification system 1)
FIG. 1 shows a block diagram of the exhaust gas purification system 1 of this embodiment. The exhaust gas purification system 1 includes an air suction port 2, an ozone generator 3, and a NOx storage reduction catalyst 4. The ozone generator 3 includes a photocatalyst reactor 100 and an ozone generation reactor 200.

Air is supplied to the photocatalyst reactor 100 from the air suction port 2 (arrow Y1). Air is a raw material gas for ozone generation. The photocatalyst reactor 100 is a site that decomposes at least a part of water contained in air. Air in which moisture is decomposed is supplied from the photocatalyst reactor 100 to the ozone generation reactor 200 (arrow Y2). The ozone generation reactor 200 is a portion that generates ozone using air in which moisture is decomposed. Air containing a high concentration of ozone is supplied from the ozone generation reactor 200 to the NOx storage reduction catalyst 4 (arrow Y3). The NOx storage reduction catalyst 4 occludes NO ₂ or NO ₃ in the exhaust gas using the supplied ozone.

(Structure of Photocatalyst Reactor 100)
FIG. 2 shows a schematic diagram of the bird view of the photocatalyst reactor 100. The photocatalyst reactor 100 includes a substrate 110, a light guide plate 120, and a plurality of light emitting diodes 130. Air is supplied from the left side of the substrate 110 (arrow Y1), and air is exhausted to the right side (arrow Y2). Therefore, as shown by the dotted arrow, the air flow path P0 is formed. Air is a raw material gas for ozone generation. A plurality of fins 111 are arranged on the upper surface of the substrate 110. Since the fins 111 can form uneven portions in the air flow path P0, the surface area in contact with the air can be increased. The substrate 110 and the fins 111 are dielectrics.

Note that FIG. 2 shows a state in which the light guide plate 120 is separated upward from the substrate 110 for the sake of clarity. Actually, the lower surface of the light guide plate 120 is in contact with the upper surface of the fin 111. Then, the slit portion between the fins 111 functions as the flow path P0.

The photocatalyst 112 is applied to the upper surface of the substrate 110 and the surface of the fins 111. In FIG. 2, the photocatalyst 112 is shown in the gray area. As a result, the photocatalyst 112 is arranged in at least a part of the flow path P0. The photocatalyst 112 includes titanium oxide (TIO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), strontium titanate (SrTiO ₃ ), tantalum nitride (Ta ₃ N ₅ ), and the like. It is a substance containing at least one of tantalum oxynitride (TaON). In this example, anatase-type titanium oxide was used.

The light emitting diode 130 is a portion for irradiating the photocatalyst 112 with light to exhibit a catalytic action. The light emitting diode 130 is a light source having a wavelength in the ultraviolet to visible region. The light emitting diode 130 generates light having a specific wavelength at which catalytic action is generated. That is, the light emitting diode 130 generates light having an intensity distribution (spectrum) having a wavelength biased to the vicinity of the absorption peak wavelength of the photocatalyst. When the photocatalyst is anatase-type titanium oxide, the absorption peak wavelength is around 380 nanometers.

The light guide plate 120 is a plate that uniformly surface-emits the light input from the upper surface. As a result, the light emitted from the light emitting diode 130 can be uniformly surface-irradiated to the entire photocatalyst 112. Light may be introduced from the end face of the light guide plate 120.

When the semiconductor, which is the photocatalyst 112, is irradiated with light having an energy equal to or higher than the band gap, electrons in the valence band are excited into the conduction band. Excited electrons reduce water to produce hydrogen. On the other hand, the holes formed in the valence band oxidize water to generate oxygen. By such a decomposition reaction, the water contained in the air can be decomposed into OH, hydrogen, oxygen, or their ionic species / radicals.

(Structure of ozone generation reactor 200)
FIG. 3 shows a schematic diagram of the view of birds of the ozone generation reactor 200. The ozone generation reactor 200 is a discharge type ozone generation device. The ozone generation reactor 200 includes a first dielectric 11 and a second dielectric 12. The first dielectric 11 is a plate-shaped member having a first surface 31 on the lower surface. The first dielectric 11 includes a plurality of first electrodes 21 inside. The second dielectric 12 is a plate-shaped member having a second surface 32 on the upper surface. The second dielectric 12 is internally provided with a plurality of second electrodes 22 arranged in the vicinity of the second surface 32. The first dielectric 11 and the second dielectric 12 are arranged so that the first surface 31 and the second surface 32 face each other. The discharge space E1 is formed by the gap between the first surface 31 and the second surface 32. The distance D between the first dielectric 11 and the second dielectric 12 is 0.5 to 1.0 [mm].

The inflow port 41 is an inflow port of the raw material gas into the discharge space E1. The raw material gas (air in which moisture is decomposed) exhausted from the photocatalyst reactor 100 is supplied to the inflow port 41 (arrow Y2). The discharge port 42 is a discharge port for the raw material gas from the discharge space E1. Therefore, the inflow port 41, the discharge space E1, and the discharge port 42 form a gas flow path P1 for the ozone raw material gas. In FIG. 3, the gas flow path P1 is indicated by a dotted arrow. The flow velocity of the raw material gas is preferably 100 [m / sec] or less. The lower limit of the flow velocity of the raw material gas is about 1.0 [m / sec]. If there is such a flow velocity, the generated ozone is scavenged from the vicinity of the surface of the dielectric.

Further, the ozone generator 3 includes a voltage application unit (not shown). The voltage application unit applies a first voltage between the first electrode 21 and the second electrode 22. The first electrode 21 serves as a positive electrode, and the second electrode 22 serves as a negative electrode. The first voltage is an AC voltage or a pulse voltage. The first voltage is, for example, 5 [kV]. As a result, a streamer-like utility pole is generated between the first electrode 21 and the second electrode 22 that face each other. Ozone is generated where the utility pole is generated. The generated ozone is scavenged by the continuous supply of the raw material gas and supplied to the outside.

(simulation result)
A simulation experiment was conducted on the amount of ozone generated by the ozone generator 3 according to this embodiment. Experimental Example 1 is a comparative example in which the photocatalyst reactor 100 is not used. In Experimental Example 1, air having a temperature of 35 ° C. and a relative humidity of 85% was used as a raw material gas. Experimental Example 2 is an example in which the photocatalyst reactor 100 is used. Moisture in air having a temperature of 35 ° C. and a relative humidity of 85% was decomposed by the photocatalytic reactor 100. As a result, the relative humidity decreased from 85% to 8%, about 1/10. Then, air having a temperature of 35 ° C. and a relative humidity of 8% was used as a raw material gas. As a result, in Experimental Example 2, the amount of ozone produced could be tripled as compared with Experimental Example 1.

(effect)
Industrially used ozone generators (eg, water purification and cleaning) often use bomb gas such as pure oxygen that does not contain water as a raw material gas. However, since the ozone generator used for purifying exhaust gas may be mounted on a vehicle, it may be necessary to use outside air (air) as a raw material gas. Since air contains water, this water inhibits the production of ozone and decomposes the generated ozone. As a result, the amount of ozone produced is reduced. In the technique of the present specification, water contained in air, which is a raw material gas, can be decomposed into OH, hydrogen, oxygen, or their ionic species / radicals by a photocatalyst. The effect of water decomposition products on ozone generation and ozone decomposition is small. Therefore, it is possible to suppress a decrease in ozone generation ability by promoting decomposition of water contained in the raw material gas by catalytic action.

In the technique of the present specification, the light emitting diode 130 irradiates light. Light emitting diodes have very high conversion efficiency because semiconductors directly convert electrical energy into light. As a result, the power consumption can be reduced to several tenths as compared with the case of irradiating light with plasma emission, for example. Further, the intensity distribution (spectrum) of the wavelength of the light emitting diode can be adjusted according to the type of the compound semiconductor and the impurity concentration. Therefore, for example, the intensity distribution of the wavelength can be freely designed as compared with the light emitted by plasma emission. As a result, the photocatalyst can be irradiated with light having an intensity distribution having a wavelength biased to the vicinity of the absorption peak wavelength of the photocatalyst. Since the efficiency of generating the catalytic action of the photocatalyst can be increased, power saving can be achieved.

In the technique of the present specification, by using the light guide plate 120, the light emitted from the light emitting diode 130 can be uniformly irradiated to the entire photocatalyst 112. As a result, the efficiency of generating the catalytic action of the photocatalyst can be increased, so that power saving becomes possible.

When a device that removes or decomposes moisture from air is mounted on a vehicle, it is necessary to meet all three requirements of being maintenance-free, having low energy consumption, and having immediate startability. As a method for removing the moisture contained in the air, an adsorption method, an absorption method, a cooling method, a compression method and the like are known. However, these methods do not meet all of the above three requirements. That is, the adsorption method requires maintenance to dry the solid on which moisture is adsorbed at a high temperature. The absorption method requires maintenance to heat and concentrate the liquid on which water is adsorbed. The cooling method requires a refrigerator and consumes a lot of energy. The compression method requires a compressor and consumes a large amount of energy. Therefore, in the technique described in the present specification, a photocatalytic method is used as a method for decomposing the moisture contained in the air. As a result, all of the above three requirements can be satisfied. That is, since the photocatalyst has a function of decomposing dirt by itself, it can be made maintenance-free. Further, since the light is irradiated by the light emitting diode, the energy consumption is low as described above. And since the water is decomposed by the excitation of electrons, it has immediate startability. This makes it possible to configure an ozone generator suitable for in-vehicle use.

Since the ozone generator 3 described in the present specification can suppress a decrease in ozone generation ability, it can generate ozone having a high concentration of 100 ppm or more. Therefore, it is possible to enhance the purifying action of the exhaust gas in the NOx storage reduction catalyst 4.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

(Modification example)
In the photocatalyst reactor 100, there may be various forms in which the uneven portion is formed in the air flow path P0. For example, fine protrusions may be formed on the upper surface of the photocatalyst reactor 100.

The ozone generation reactor 200 is not limited to the discharge type and may have various modes. For example, it may be EUV irradiation type.

The light source unit that irradiates the photocatalyst with light is not limited to the light emitting diode, and various light sources can be used. For example, it is possible to exert a catalytic action with visible light by doping the photocatalyst. In this case, natural light can be used to act on the photocatalyst.

The shape of the photocatalyst reactor 100 is not limited to the form shown in FIG. For example, it may have a cylindrical shape. Further, the flow path P0 is not limited to a linear shape and may be bent.

The photocatalyst reactor 100 is an example of a decomposition unit. The ozone generation reactor 200 is an example of an ozone generation unit. The light emitting diode 130 is an example of a light source unit. The fin 111 is an example of the uneven portion.

1: Exhaust gas purification system 2: Air intake port 3: Ozone generator 4: NOx storage reduction catalyst 100: Photocatalyst reactor 110: Base 111: Fin 112: Photocatalyst 120: Light guide plate 130: Light emitting diode 200: Ozone generation reactor P0: Channel

Claims (6)

An ozone generator that generates ozone used to purify exhaust gas.
The ozone generator
A decomposition part that decomposes at least a part of the water contained in the raw material gas,
An ozone generation unit that generates ozone using the raw material gas whose water is decomposed in the decomposition unit,
With
The disassembled part
The flow path of the raw material gas, wherein the photocatalyst is arranged at least in a part thereof.
A light source unit that irradiates the photocatalyst with light,
Equipped with an ozone generator. At least a part of the flow path is provided with an uneven portion.
The ozone generator according to claim 1, wherein the photocatalyst is arranged on the surface of the uneven portion. The light source unit is a light emitting diode.
The ozone generator according to claim 1 or 2, wherein the light source unit generates light having an intensity distribution having a wavelength biased in the vicinity of the absorption peak wavelength of the photocatalyst. The ozone generator according to any one of claims 1 to 3, further comprising a light guide plate for surface-irradiating the entire photocatalyst with light emitted from the light source unit. The photocatalyst includes titanium oxide (TIO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), strontium titanate (SrTiO ₃ ), tantalum nitride (Ta ₃ N ₅ ), and the like. The ozone generator according to any one of claims 1 to 4, which comprises at least one of tantalum oxynitride (TaON). The ozone generator according to any one of claims 1 to 5, wherein the concentration of ozone generated by the ozone generating unit is 100 ppm or more.

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