JPH0674908B2 - Gas cleaning method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electronic industry, a pharmaceutical industry, a food industry, an agriculture and forestry industry, medical treatment,
Clean room, clean booth, clean tunnel, clean bench, safety cabinet, aseptic room, bath box, aseptic air curtain, cleaning method for gases such as oxygen, nitrogen, etc. in the precision machinery industry.

A method for cleaning gases emitted from various industries and industries such as flue gas and automobile exhaust gas.

 Air cleaning methods for homes, businesses, hospitals, etc.

And an apparatus for performing the described method.

Regarding

[Conventional technology and its problems]

The conventional indoor air cleaning methods or the apparatus therefor are roughly classified into (1) a mechanical filtration method (for example, a HEPA filter) (2) a high-voltage charged and conductive filter that electrostatically collects fine particles. There are methods (for example, MESA filter), but each of these methods has the following drawbacks.

That is, in the mechanical filtration method, it is necessary to use a fine filter to increase the air cleanliness (class), but in this case, the pressure loss is high, and the pressure loss due to clogging is also remarkable. , The life of the filter is short,
Not only is it difficult to maintain, manage, or replace the filter, but when replacing the filter, it is necessary to stop the work during that time, and it takes a long time to restore the product. Atsuta

Further, in order to improve the cleanliness of the air, the number of ventilations (the number of air circulations by a fan) is also increased, but in this case, there is a drawback that the power cost becomes high.

In addition, the conventional filter method can be used as an industrial clean room because it is only intended to remove fine particles, but the filter has pin holes enough to say that some of the contaminated air leaks. Therefore, there is a limit to the use in the biological clean room.

In addition, in the method of electrostatically collecting fine particles, a high voltage of, for example, 15 to 70 KV is required for the pre-charging portion, so the device becomes large and there are problems in terms of safety and maintenance. It was

In order to solve these problems, the present inventor has proposed an air cleaning method by ultraviolet irradiation or irradiation (Japanese Patent Laid-Open Nos. 61-178050 and 62-244459).

Although these methods are effective depending on the application field, there is room for improvement in specific fields and applications. In order to improve, it is necessary to make the method more practical and more practical.

In order to increase the practicality, the photoelectrons are more effectively emitted from the photoelectron emitting material to efficiently charge the fine particles, and in the field where the presence of microorganisms is a problem like the biotechnology field, the It is necessary to completely sterilize the kind.

[Object of the Invention]

The present invention relates to a method and apparatus for cleaning a gas such as air in which a photoelectron emitting material is irradiated with ultraviolet rays or radiation to charge particles in the gas with the emitted photoelectrons, and then the particles are removed. The surface of the material is provided with a large number of concave projections, and in particular, the projections are sharpened and / or spherical to accelerate the emission of photoelectrons from the photoelectron emitting material and efficiently charge the fine particles. It is a thing.

[Structure of Invention]

According to the present invention, 1. The photoelectron emitting material is irradiated with ultraviolet rays and / or radiation to emit photoelectrons, the fine particles contained in the gas are charged by the photoelectrons, and then the charged fine particles are removed from the gas. A method for cleaning a gas, characterized in that a photoelectron emitting material having a large number of irregularities formed on the surface thereof is used.

2. The method for cleaning a gas according to the above item 1, wherein a photoelectron emitting material having a sharpened and / or spherical convex portion is used.

3. UV rays to the photo-emissive material and / or many irregularities formed on the surface of the gas flow path from the gas inlet to the gas outlet
Alternatively, a gas cleaning device provided with a radiation irradiator and a charged particle collector.

4. The gas cleaning device according to the above item 3, wherein the projections of the photoelectron emitting material are sharp and / or spherical. Is.

The present invention will be described mainly with reference to the drawings in the case of irradiating ultraviolet rays.

FIG. 1 is a schematic view showing an embodiment of a photoelectron emitting part by irradiation of ultraviolet rays, and FIG. 2 is a clean bench combined system in a biological clean room, that is, a system in which only a part of the working area is highly clean. FIG.

First, based on FIG. 2, a gas cleaning method in combination with a clean bench in a biological clean room will be described.

In the clean room 1, after the coarse particles of the outside air introduced from the pipe 2 are filtered by the prefilter 3, the temperature of the air in the air conditioner 6 is adjusted through the fan 5 together with the circulating air taken out from the air outlet 4 of the clean room 1. After adjusting the temperature and humidity, the air from which fine particles have been removed by the HEPA filter 7 is circulated and supplied, and the cleanliness (class) is maintained at about 10,000.

On the other hand, the fan and the voltage supply member 8 in the clean room 1, the ultraviolet irradiation unit 9 on the photoelectron emitting material, the filter 10
The workbench 13 in the clean bench 11 provided with is maintained in a sterile atmosphere of high cleanliness (class 10).

That is, in the clean bench 11, the clean room 1
Air with a cleanliness (class) of about 10,000 inside is sucked by the fan of the fan 8 and the fine particles in the air are charged by the photoelectrons generated by irradiating the photoelectron emitting member with ultraviolet rays, and at the same time, the ultraviolet energy causes a virus, After the microorganisms such as bacteria, yeasts and molds are sterilized, the charged fine particles are removed by the filter 10, so that the workbench 13 is maintained at a high cleanliness.

As shown in the schematic view of FIG. 1, the photoelectron emitting part by ultraviolet irradiation mainly comprises an electrode 20, a photoelectron emitting material 21 having a mountain-shaped surface, and an ultraviolet lamp 22, and the electrode 20 and the surface are mountain-shaped. A voltage is applied from the fan and the voltage supply unit 8 to the photoelectron emission material 21, and the photoelectron emission material 21 having a mountain-shaped surface is irradiated with ultraviolet rays, so that the electrode 20 and the photoelectron emission material 21 having a mountain-shaped surface are formed. By passing the air 50 between them, the fine particles in the air 50 are efficiently charged.

The distance between the electrode 20 and the photoemissive material 21 having a mountain-like surface depends on the shape of the device, but is generally preferably 2 to 20 cm, and particularly preferably 3 to 10 cm.

The material of the electrode 20 and its structure may be those used in conventional charging devices. Tungsten is usually used. In FIG. 1, reference numeral 23 is a coarse filter and reference numeral 24 is an electrostatic filter.

Next, the photoelectron emitting material 21 may be any material as long as it emits photoelectrons upon irradiation with ultraviolet rays, and a material having a smaller photoelectric work function is preferable. From the viewpoint of effect and economical efficiency, Ba, Sr, Ca,
Y, Gd, La, Ce, Nd, Th, Pr, Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, Cd, Pb,
Any one of Al, C, Mg, Au, In, Bi, Nb, Si, Ti, Ta, Sn and P or a compound or alloy thereof is preferable, and these are used alone or in combination of two or more kinds. As the composite material, a physical composite material such as amalgam can also be used.

Examples of compounds include oxides, borides, and carbides, and oxides include BaO, SrO, CaO, Y ₂ O ₅ , Gd ₂ O ₃ , Nd ₂ O ₃ , ThO ₂ , and Fe.
₂ O ₃ , ZnO, CuO, Ag ₂ O, PtO, PbO, Al ₂ O ₃ , MgO, In ₂ O ₃ , BiO, NbO, B
eO, etc., and borides include YB ₆ ,, GdB ₆ ,, NaB ₆ ,, CeB ₆ ,, P
rB ₆ , ZrB _2, etc., and further carbides such as ZrC, TaC, Ti
C, NbC, etc.

As the alloy, brass, bronze, phosphor bronze, an alloy of Ag and Mg (Mg is 2 to 20 wt%), an alloy of Cu and Be (Be is 1 to 1).
10 wt%) and an alloy of Ba and Al can be used.
Alloys of Ag and Mg, alloys of Cu and Be, and alloys of Ba and Al are preferable. As an oxide, heat a metal in air,
Alternatively, it is also possible to use a metal plate whose surface is made to be an oxide by being oxidized with a chemical.

As another method, it is possible to obtain a stable oxide layer over a long period of time by heating before use and forming an oxide layer on the surface. An example of this is that an alloy of Mg and Ag can be formed into an oxide thin film on its surface in water vapor at a temperature of 300 to 400 ° C. This oxide thin film is stable over a long period of time. Is.

The present invention is to use, in the use of these materials, those having a large number of irregularities on the surface thereof, in particular those having a sharpened or spherical convex portion. For example, there are those provided with a large number of mountain-shaped projections, sword mountain type, needle type, and spherical type, and one type or a combination of two or more types can be used as appropriate. That is, when the surface of the photoelectron emitting material is formed into the shape, the electric field of the sharpened portion (the peak portion in the case of the mountain shape in FIG. 3) becomes dense, and the substantial surface area of the photoelectron emitting material increases, so Is effectively generated, and as a result, the charging efficiency of fine particles is improved.

The shape of the surface of the photoelectron emitting material can be processed and formed by an appropriate method. For example, the shape of the spherical sphere can be made by coating or adhering the particulate photoelectron emitting material on a material having an appropriate shape.

These optimum shapes can be determined by conducting preliminary tests as appropriate depending on the scale of the apparatus, shape, type of electron emitting material, application of electric field, effect, economical efficiency and the like.

FIG. 3 shows a mountain-shaped one as an example of the photoelectron emitting material provided with sharp-edged convex portions.

The shape of the photoelectron emitting material used and the shape of the surface thereof differ depending on the shape, structure or desired efficiency of the device, and can be appropriately determined depending on the scale, shape, effect of the device, type of photoelectron emitting material, economical efficiency and the like.

The voltage applied to form the electric field is 0.1 to 10 KV, preferably 0.1 to 5 KV, more preferably 0.1 to 3 KV,
The voltage varies depending on the shape of the device, the material or structure of the electrode or the photoelectron emitting material used.

The type of ultraviolet rays or radiation may be any as long as the photoelectron emitting material can emit photoelectrons by its irradiation,
In the biological field, those having a bactericidal action are also preferable.

As a light source of ultraviolet rays, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube or the like can be appropriately used in one kind or in combination of two or more kinds.
It can be appropriately determined depending on the economical efficiency. For example, in the biological field, it is preferable to use a light source having deep ultraviolet rays from the viewpoint of bactericidal action and efficiency.

Α rays, β rays, γ rays, etc. are used as the radiation, and cobalt 60, cesium 137, strontium 9 are used as irradiation means.
There is a method of using radioactive same elements such as 0, or radioactive waste produced in a nuclear reactor and radioactive materials appropriately treated and processed as radioactive sources.

Charged particulates containing dead organisms are filtered 10,2
Captured at 4.

The charged particle collector may be any collector.

A dust collecting plate (dust collecting electrode) or an electrostatic filter system in a normal charging device is generally used, but a structure in which the collecting portion itself constitutes an electrode such as a steel wool electrode is also effective.

Further, the method of collecting by using the ion exchange filter, which the present inventor has already proposed, is also effective.

For collection, these collection methods can be used alone, or two or more kinds of these methods can be combined and appropriately used.

Among these collection methods, a preferable method is a filter method, for example, an ion exchange filter (anion exchange filter, cation exchange filter) or a method using an electrostatic filter is capable of collecting charged fine particles with high efficiency and reliability. This is convenient because it can be done.

The filter system is easy to handle,
Although it is effective from an economical point of view, it will be clogged when used for a certain period of time.Therefore, if necessary, adopt a cartridge structure and replace it when pressure loss is detected to enable stable operation over a long period of time. Become.

Incidentally, the photoelectron emitting material 21 and the ultraviolet lamp in this embodiment
The position of 22 is parallel to the air flow, but it may be at a position perpendicular to the air flow or at any position between the parallel and right angles. It may be installed in.

Irradiation of the photoelectron emitting material 21 with ultraviolet rays may be spot irradiation (narrowing down) irradiation or whole surface irradiation.

Further, the photoelectron emission from the photoelectron emission material 21 can also be performed by utilizing the reflecting surface, as already proposed by the present inventor. These can be appropriately determined depending on the shape, scale, kind, shape, application field, kind, shape, effect, economical efficiency, etc. of the device.

Also, instead of irradiating with ultraviolet rays, by irradiating with radiation, the same effect can be obtained by electrically charging the fine particles.

Although the field of gas cleaning has been described as a field of use of the present invention, the same applies to the electron-emitting material of the “particle measuring device utilizing the photoelectric effect (Japanese Patent Laid-Open No. 62-2428385)” that the present inventor has already proposed. Applicable.

Example A test was conducted using an air purifier having the shape shown in FIG.

However, ultraviolet lamp; mercury lamp 30W electric field voltage; 2KV charged particle collection filter; electrostatic filter For the generated particles, use cigarette smoke (average particle size 0.3 to 0.4 μm), dilute it appropriately and send it at 20 / min, and use a particle measuring instrument at the inlet (rear of the coarse filter) and the outlet (rear of the electrostatic filter). The concentration used was measured.

The results are shown in Table 1.

Comparative Example In the example, a photoelectron emitting material made of brass (a flat plate having a flat surface of 8 cm × 20 cm and having a surface of 8 cm × 20 cm) and plated with gold was used, and the same test was performed.

The outlet concentration was 2520 pieces /.

〔The invention's effect〕

By making the shape of the surface of the photoelectron emitting material sharp, and / or uneven and / or spherical, the emission of photoelectrons was promoted, and the charging of the fine particles became effective.

Since the charging of the fine particles is effective, the device can be downsized (compact) and the processing capacity is increased.

Contaminants such as fine particles in the air stream were collected with high efficiency so that the flow to the wake was practically negligible, and a sterilized gas stream of ultra-high cleanliness was obtained.

It can be applied to various fields and applications, and is particularly effective in fields in which the presence of microorganisms has a particular effect, such as those related to clean rooms, which are limited and difficult with conventional methods, and particularly related to biotechnology. We were able to provide equipment.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the gas cleaning method and its apparatus of the present invention, FIG. 2 is a schematic diagram for explaining a gas cleaning apparatus using a clean bench in a biological clean room, and FIG. 3 is a mountain. It is drawing which shows the perspective view of the photoelectron emission material which provided the sharpened part of a type | mold. 1 ... Clean room, 6 ... Air conditioner, 8 ... Fan and voltage supply unit, 9 ... UV irradiation unit on photoelectron emitting material, 10 ... Filter, 11 ... Clean bench, 13
…… Workbench, 20 …… Electrode, 21 …… Photoelectron emitting material, 22 ……
UV lamp, 24 ... Electrostatic filter

Claims (4)

[Claims] 1. A gas which emits photoelectrons by irradiating a photoelectron emitting material with ultraviolet rays and / or radiation, charges the fine particles contained in a gas by the photoelectrons, and then removes the charged fine particles from the gas. In the cleaning method of
A method of cleaning a gas, which comprises using a photoelectron emitting material having a large number of irregularities formed on its surface. 2. The method for cleaning gas according to claim 1, wherein a photoelectron emitting material having a sharpened and / or spherical convex portion is used. 3. An ultraviolet ray and / or radiation irradiating section and a charged particle collecting section for a photoelectron emitting material having a large number of irregularities formed on the surface of a gas flow path from a gas suction port to a gas discharge port. Gas purifier. 4. The gas cleaning device according to claim 3, wherein the projections of the photoelectron emitting material are sharp and / or spherical.