JPS63305922A - Method for treating waste ozone - Google Patents

Abstract

PURPOSE:To remove waste ozone efficiently, by passing gases containing waste ozone over a photo-catalyst irradiated by light in an electric field. CONSTITUTION:Gases containing waste ozone enter a photo-catalytic reactor 2 through an inlet portion 1 to be decomposed by means of a photo-catalyst members 4(4-1-4-6) composed of oxides of Ti, Co, Ag, Fe, Ni etc. In this case, the photo-catalysts 4 is irradiated by an ultraviolet lamp 5 and at the same time an electric voltage of 50V-30KV is applied to the catalysts by an electrode to form an electric field. In this manner, the waste ozone is decomposed efficiently and discharged from an outlet 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detoxifying waste ozone.

[Conventional technology and its problems]

Ozone is used in a wide range of fields because of its strong bactericidal and oxidizing power.

In other words, it has various uses in a wide range of fields as shown in Table 11, such as water treatment such as high-level treatment of wastewater, deodorization in living areas and production processes, food storage and medical fields. It is used in

Table 1 Fields and Applications of Ozone However, on the other hand, there is the problem of releasing unreacted ozone (waste ozone) after using ozone. Ozone is highly toxic even at low concentrations and may cause pollution, so it is desired to completely detoxify waste ozone.

For example, the concentration of waste ozone varies depending on the field of use or application, but is generally on the order of several ppm to several hundred ppm. When this is discharged, the discharge concentration is l 1 pp
It is necessary to process it so that it becomes less than m. For example 100
To reduce the concentration of ppm ozone to less than αlppm 9
A processing efficiency of 99 degrees or higher is required.

Waste ozone includes the unreacted ozone released when using ozone as mentioned above, as well as ozone generated from IHJ, IT, copying machines, ozone generated when using electron beam accelerators, etc. A similar problem exists with waste ozone.

Conventional methods for treating ozone include an activated carbon method, a catalyst method, a chemical cleaning method, and a thermal decomposition method, but each method has the following drawbacks.

■ Activated carbon method Niosin and activated carbon react to produce CO, Co,
In addition to producing F and consuming the activated carbon, these reactions are exothermic, so there is a risk of fire or explosion if used incorrectly. For this reason, it is necessary to sufficiently manage driving and operation.

In addition, pressure loss is high and running costs are relatively high.

■Catalytic method: The effectiveness may be low if used intermittently.

■Cleaning method using chemical solutions: Chemical costs are high.

Furthermore, since it is a wet method, a scrubber is required, the equipment is relatively large, and waste liquid must be treated.

■ Thermal decomposition method: requires a temperature of 350°C or higher, which is unfavorable in terms of economy and compactness. Also, it is not suitable for intermittent use.

Furthermore, in these conventional methods, relatively high concentrations of ozone can be treated with relatively high efficiency, but in the case of low concentrations (for example, several ppm), the treatment efficiency is low.

[Purpose of the invention]

The present invention solves the above problems and allows various concentrations of V
The purpose of the present invention is to provide a waste ozone treatment method that decomposes Pel waste ozone to a low concentration and that can be operated stably and continuously for a long period of time.

[Structure of the invention]

The present invention relates to a method for decomposing ozone by passing a waste ozone-containing gas over a photocatalyst that is irradiated with light in an electric field, as well as methods for treating waste ozone other than this method, such as an activated carbon method, a catalyst method, and a method for treating waste ozone. This is a method of treating ozone in combination with/or a method of using an ozone scavenger.

Next, the present invention will be explained based on the drawings.

FIG. 1 shows an example in which waste ozone treatment equipment is applied to waste ozone treatment in a food factory, for example, using a photocatalyst that is irradiated with light in an electric field.

1Vi is the inlet of waste ozone discharged during food sterilization. Waste ozone with a medium concentration is decomposed in the photocatalytic reactor 2 which forms an electric field and is irradiated with light, becomes an extremely low concentration ((L 1 ppm or less)), and is discharged from the outlet 6.

The photocatalytic reactor 2 includes a photocatalytic material 4 (4-1 to 4-6), an ultraviolet lamp 5, and an electrode (FIG. 2, described later) for forming an electric field on the surface of the photocatalytic material.

The photocatalytic material 4 is irradiated with ultraviolet light by an ultraviolet lamp 5, and an electric field is formed around the photocatalytic material by the electrodes.

FIG. 2 shows an example of electric field formation.

The photocatalytic material 4 is fixed on the Ti plate electrode 6, and the T
An electric field is created by applying a voltage between the i-plate electrode 6 and another electrode (tungsten) 7.

By irradiating the surface of the photocatalyst material with light, electrons are released in the vicinity, and the waste ozone is first decomposed and removed by the action of the electrons. Next, waste ozone that has not been decomposed and removed by the action of electrons is decomposed and removed on the photocatalyst surface.

Here, the decomposition and removal function of waste ozone in the photocatalyst is as follows.
As described above, this is improved by forming an electric field on the photocatalyst, and waste ozone is decomposed and removed to an extremely low concentration. This is thought to be because by placing the photocatalytic material in an electric field, the surface of the photocatalyst has a reducing effect on ozone, so that the ability of the photocatalyst to decompose ozone is significantly improved.

According to the present invention, usually about 1 to several tens of ppm of ozone is reduced to cL 1 ppm or less, preferably I:L 05 ppm.
The following will be processed.

Next, the photocatalyst materials 4-1 to 4-6 will be explained.

The photocatalyst material may be any material as long as it is excited by light irradiation, emits electrons, and promotes ozone decomposition by being placed in an electric field. Generally, semiconductor materials are preferred because they are effective, readily available, and have good processability.

From the viewpoint of effectiveness and economy, Se, Ge, Si, Ti
.

Zn, Ou, At, Sn, Ga, In, P,
As, S't)+C,O(1,S,Te,Ni,F
e, C! o, Ag9MopSr, W, Or, Ba, Pb
or their compounds, alloys, or oxides are preferred, and these are used alone or in combination of two or more.

For example, the elements include Si, Ge, Se,
Compounds include AtP, AtAs, GaP,
AIBb, GaA day.

Engineering nP, Garb, Engineering nAs, Engineering nsb,
OdS, Ca5e.

ZnS t Mo5g, WTel, Cr1Tli1
3. MoTetC! uzs.

W8. , as oxides TiO2, Eiz03,
Ouo.

01120 HZnO, MoO3, engineering no., Ag
l0, PbO.

5rTiO1, BaTiO3, C! o304. F(
There is 320g2 NiO.

As a method for forming the electric field, a well-known method as shown in FIG. 2 can be used as appropriate. Tie as a photocatalyst material was fixed on the T1 plate, and Tie! A tungsten electrode may be installed at a position t5- above.

As a method for fixing the photocatalytic material, known methods such as sintering, vapor deposition, and sputtering can be used as appropriate.

The material and structure of the electrode may be those used in conventional electric field generation equipment. For example, as the electrode material, suanreth, copper, and tungsten are appropriately used in a linear, net, plate, or other shape.

These materials are designed in consideration of deterioration caused by light irradiation and ozone.
Heat treatment in air, chemical treatment, metal thin film deposition, T1
0! It is possible to make the material stable for a long period of time by coating the surface with a stable semiconductor such as.

In FIG. 2, 8 indicates an inlet gas flow, and 9 indicates an outlet gas flow.

The shape of the photocatalyst material 4 is such that waste ozone-containing air can pass through it, and depending on the type of device, it can be shaped like a grid, plate, or
It may be in the form of grains, pleats, mesh, etc. Further, it can be used by being supported on a carrier. This allows it to have an arbitrary structure.

The voltage applied as an electric field is 50V to 30KV.

Preferably, Q is 1 to 20 KV, and the voltage can be appropriately determined by preliminary tests etc. based on the type of device, the material of the electrodes used, the structure, efficiency, economical efficiency, etc.

For ultraviolet rays, a lamp that emits wavelengths in the light absorption region determined by the type of photocatalyst material may be selected.

For example, in the case of Tie, the light absorption is in the near ultraviolet range, so a lamp that emits light with a wavelength in the near ultraviolet range is used.

As the light source, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, etc. can be used as appropriate.

It goes without saying that the lamp is preferably of a type that does not generate ozone due to ultraviolet irradiation, such as an ozone-less lamp.

The light source may be installed inside the photocatalytic reactor as shown in Figure 1, but as another example, it may be installed outside the reactor and the ultraviolet rays can be applied to the photocatalytic material by using a reflective surface or through an irradiation window. It may also be irradiated.

Next, a case will be described in which waste ozone treatment by the method of the present invention and waste ozone treatment by a method other than the present invention are performed in combination.

FIG. 3 is a flow diagram illustrating a waste ozone treatment method in sewage treatment that uses waste ozone treatment equipment using a photocatalyst that forms an electric field, and equipment using a catalyst method as waste ozone treatment equipment other than this method.

In FIG. 3, reference numeral 10 is the inlet of waste ozone discharged from an ozone reaction device (not shown) in sewage treatment, and high concentration waste ozone is decomposed into a relatively low concentration in the catalyst filling section 11. Then, it is decomposed in the photocatalyst section 12 in which an electric field is applied, resulting in an extremely low concentration (α1 ppm or less), and is discharged from the outlet 13.

The catalyst filling section 11 is a reactor filled with a catalyst. The catalyst is usually Mn01. Co oxide added MnO2
, FeO, NiO and other metal oxide catalysts, Ag, Pt,
A catalyst in which a noble metal catalyst such as Pa is supported on 8102 or γ-alumina is used.

The ozone decomposition rate in the catalyst filling section 11 is usually 90 to 9.
It is about 9%.

That is, in the catalyst filling part 11, the amount of
0 ppm, usually several 10 ppm to several 100 pl)m
of waste ozone is treated to 1 to several JOppmi degrees.

Reference numeral 12 denotes a photocatalytic reactor in which an electric field is formed, and this reactor is the same as that described in FIGS. 1 and 2 of the previous embodiment.

In the photocatalytic reactor 12, waste ozone (1 to several tens of ppm) that cannot be treated in the catalyst filling unit 11 and is emitted is decomposed and removed to an extremely low concentration by passing over the photocatalyst that is irradiated with light in the k electric field. .

The waste ozone treatment method other than the present invention in combination with the method of the present invention may be any method as long as high concentration ozone is treated to a relatively low concentration. , or activated carbon method is preferred.

In addition, when the waste ozone concentration is relatively low, it is preferable to use the method of using an ozone scavenger already proposed by the present inventor (Japanese Patent Application No. 17324/1982) from the viewpoint of treatment effect, operability, scale of the device, etc. I can do it.

An example of a preferred form of the waste ozone treatment method is shown below.

Whether to use the method of the present invention alone or in combination with methods other than the present invention as a waste ozone treatment method depends on the type of waste ozone source, scale, coexisting components, economic efficiency, operability, effectiveness, etc. Based on this, laws can be made as appropriate.

Example of waste ozone treatment method Next, examples will be described.

Example-1 As shown in Fig. 1, air containing 5 ppm of ozone was supplied from an ozone generator to a waste ozone treatment device at a rate of [11 t /
The ozone concentration at the outlet was measured.

The results are shown in Table 2.

Formation of electric field: As shown in Fig. 2, a photocatalyst was fixed on a Ti plate (negative electrode), and the photocatalyst surface was separated from the tungsten electrode (positive electrode) by 1.5 points. Apply oxv.

Ozone generator: Discharge method Ultraviolet lamp: Mercury lamp 20W Equipment size: 50 x 't OOX 200 ■Table
2 Again, T10! and for C03o4 photocatalyst material, about 1
Table 3 shows the results (outlet ozone concentration) of continuous operation for several months.

Table 6 As a comparative example, the results were conducted without applying an electric field to the photocatalyst.
．． It was 5 ppm.

Example 2 Similar to Example 1, 650 M'm of ozone was generated from an ozone generator, passed through a waste ozone treatment device as shown in Figure 6 at a rate of l3L/min, and the outlet ozone concentration was similarly adjusted. Remember to measure.

The results are shown in Table 4.

Catalyst: CO acid oxide 1 group (150℃) Photocatalyst: Ti01, Ag2O Ultraviolet lamp: Mercury lamp 20W Equipment size: so*x100 horizontal x! IO 01111
Table 4 Table 5 shows preliminary results (outlet ozone concentration) of Tie and Ag2O photocatalyst materials after approximately one month of continuous operation.

Table 5 [Effects of the invention] 1. By using a photocatalyst and forming an electric field around the photocatalyst as a waste ozone treatment method, (1) the ozone decomposition effect of the photocatalyst was significantly improved.

■ We were able to process waste ozone with high efficiency and in a stable manner over a long period of time.

■ We were able to reduce the emitted ozone concentration to a virtually negligible level (extremely low concentration).

■ It has the same effect whether it is used continuously or intermittently.

Z By using the method of the present invention together with a waste ozone treatment method other than the present invention, it was possible to provide a waste ozone treatment device that can handle a wide variety of sources.

We have created a practically effective device that takes advantage of the features (advantages) of both methods.

That is, since the catalyst method and the activated carbon method mainly rely on decomposition reactions, the higher the concentration of ozone, the more effective they are.

Furthermore, the method using an ozone scavenger uses a scavenging (adsorption) action and is therefore effective at moderate to low concentrations.

In contrast, the method of the present invention is effective at moderate to low concentrations.

■ A waste ozone treatment device has been created that is highly practical even in continuous operation, intermittent operation, or in the case of exhaust gas with fluctuating inlet concentration.

■ We were able to reduce high concentration waste ozone to an extremely low concentration.

[Brief explanation of drawings]

Figure 1 is a diagram showing an outline of a photocatalytic reactor for explaining the method of the present invention, Figure 2 is a diagram showing an example of an electrode for forming an electric field, and Figure 3 is a diagram showing a method of the present invention and a method other than the present invention. FIG. 4.4-1 to 4-6... Photocatalyst material, 5-... Ultraviolet lamp, 6... Ti plate electrode, 7... Tungsten electrode, 11... Catalyst filling part, 12... Photocatalyst reactor

Claims (1)

[Claims] 1. A method for treating waste ozone, which comprises passing waste ozone-containing gas over a photocatalyst that is irradiated with light in an electric field. 2. The method for treating waste ozone according to claim 1, wherein the photocatalyst is a semiconductor. 3. Photocatalyst is Se, Ge, Si, Ti, Zn, Cu, S
n, Al, Ga, In, P, As, Sb, C, Cd, S
, Te, Ni, Fe, Co, Ag, Mo, Sr, W, C
3. The method for treating waste ozone according to claim 2, which comprises a composite of one or more selected from r, Ba, Pb, or their compounds, alloys, or oxides. 4. The waste ozone treatment method according to any one of claims 1 to 3, wherein the voltage of the electric field is within the range of 50V to 30KV. 5. Waste ozone treatment according to claim 1, which is a combination of a waste ozone treatment method different from the method according to claim 1 and the waste ozone treatment method according to claim 1. Method. 6. As a waste ozone treatment method different from the method described in claim 1, at least one of the activated carbon method, the catalyst method, and the method using an ozone scavenger is used as described in claim 5. How to treat waste ozone.