JPS62244459A - Method and apparatus for purifying air by irradiation of radioactive rays - Google Patents

Abstract

PURPOSE:To purify air only by providing a dust collecting plate to a downstream side, by generating a photoelectron by irradiating a photoelectron discharge material with radioactive rays and charging fine particles by the photoelectron to remove charged fine particles. CONSTITUTION:Air with a purifying degree of about 10,000 in a clean room is sucked in a clean bench 11 by a fan 5. Further, a photoelectron discharge member 21 is irradiated with radioactive rays to generate a photoelectron and fine particles in air are charged by said photoelectron. For example, when a <137>Cs or <60>Co ray source having sterilizing action is used as radioactive rays, microorganisms such as a virus, bacteria, yeast or fungi are sterilized and, thereafter, the charged fine particles are removed by a filter 10 to hold the top surface of the working bench 13 at a high purifying degree.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to the electronic industry, pharmaceutical industry, food industry, agriculture and forestry industry,
The present invention relates to air cleaning methods and devices for clean rooms, clean benches, clean tunnels, clean benches, safety cabinets, sterile rooms, bath boxes, sterile air curtains, clean tubes, etc. in the medical and precision machinery industries.

[Prior art and its problems] Conventional indoor air purification methods and devices can be roughly divided into: (1) mechanical filtration methods (for example, HE P /4 filters); (2) electrostatic collection of particulates; Charging with high voltage and filtration method with conductive filter (for example, MESA
filters), but each of these methods had the following drawbacks.

In other words, when using mechanical filtration methods, it is necessary to use a fine-mesh filter in order to improve the air cleanliness (class), but in this case the pressure drop is high, and the increase in pressure drop due to clogging is also significant. and the filter life is short.
Not only is it troublesome to maintain, manage, and replace filters, but when replacing filters, it is necessary to stop work during that time, and it takes a long time to recover, resulting in poor production efficiency. Fell.

In order to improve the cleanliness of the air, the number of ventilations (the number of times air is circulated by a fan) has been increased, but this has the disadvantage of increasing power costs.

In addition, the conventional filter method is aimed only at removing particulates, so it can be used for industrial clean micrometers, but filters almost always have pinholes, which remove contaminated air. Because some of it leaks,
There were limitations to its use in biological clean rooms.

In addition, in the method of electrostatically collecting particles, a high voltage of, for example, 15 to 70V is required in the pre-charging section, which increases the size of the device and poses problems in terms of safety and maintenance. It was small.

In order to solve these problems, the present inventor proposed an air cleaning method using ultraviolet irradiation (Japanese Patent Application No. 59-216
No. 295), this method is effective depending on the field of application and use, but it is still not sufficient for purifying air containing ultrafine particles or for application to specific fields.

[Structure of the invention]

The present invention provides an air cleaning method in which fine particles in the air are charged by irradiating radiation, and then the charged fine particles are removed from the air. A method for purifying air, comprising: charging the fine particles with the photoelectrons for a second, and then removing the charged fine particles from the air. and 2. An air purifying device U4 comprising a radiation irradiation unit for photoelectron emitting material and a charged particle collection unit sequentially provided on the air flow path from the air inlet to the air outlet.

In an electric field, the fine particles in the air are charged by photoelectrons generated by irradiating the electron emitting material with radiation, and then the charged particles are removed by a method and an apparatus thereof. .

As the photoelectron emitting material, preferably a substance with a small photoelectric work function, a compound or an alloy thereof is selected, and these are used alone or as a composite material of two or more types,
Ru.

In No. 2, the present invention will be explained in detail based on the drawings.

FIG. 1 shows a schematic diagram of a method in which a biological clean frame is used in combination with a clean bench, that is, a method in which only a part of the row area is kept clean.

FIG. 2 is a schematic diagram showing an embodiment of a photoelectron emission section by radiation irradiation.

Inside the clean room 1, after filtering the coarse particles of the outside air introduced from the pipe 2 with a pre-filter 3, a clean μm
After adjusting the temperature and humidity of the circulating air taken out from the air outlet 4 of the air conditioning system 1 through the fan 5 and the air conditioner 6, the HEPA filter is installed. Air from which particulates have been removed is circulated through Letter 7, and the cleanliness (class) is 10.
,000.

On the other hand, the fan and voltage supply member 8 in the clean room 1
, a radiation irradiation unit 9 onto the photoelectron emitting material, a filter 10
The workbench 15 in the clean bench 11 provided with the above is maintained in a sterile atmosphere of high cleanliness (class 10).

That is, in the clean bench 11, air of about m cleanliness (class) I n, 00 () in the clean μm 1 is sucked by the fan 8, and radiation is irradiated 44 onto the photoelectron emitting member. The generated photoelectrons charge particles in the air, and when a +37 CB or 6°Co radiation source, which has a sterilizing effect as radiation, is used, microorganisms such as viruses, bacteria, yeast, and mold are sterilized. Thereafter, by removing the charged particles with the filter 10, the workbench 13 is maintained at a high level of cleanliness.

As shown in the schematic diagram in FIG. 2, the photoelectron emitting section due to radiation irradiation mainly consists of a discharge electrode 20, a photoelectron emitting material 21, and a source of potassium between the discharge electrode 20 and the photoelectron emitting material 21. Applying voltage from the fan and voltage supply unit 8, and irradiating the photoelectron emitting material 21 with radiation,
By passing air 50 between discharge electrode 20 and photoelectron emitting material 210, fine particles in air 50 are efficiently charged.

The distance between the discharge electrode 20 and the photoelectron emitting material 21 depends on the shape of the device, but is generally preferably 2 to 20 steps, particularly 3 steps.
~101M is preferred.

The material and structure of the discharge electrode 20 may be those used in ordinary charging devices. Tungsten wire is usually used. In FIG. 2, numeral 25 is a coarse filter, numeral 24
is an electrostatic filter.

In the example shown in FIG. 2, the photoelectron emitting material 21 as a photoelectron emitting material and the discharge electrode 20 are constructed as separate members in order to form an electric field, but of course the photoelectron emitting material 21 may also be used as a discharge ttHM. It's okay. In this case, the second
The discharge electrode 20 is omitted from the illustrated example, and voltage is applied to the photoelectron emitting material 21 from the fan and the voltage supply unit 8.

Next, the photoelectron emitting material 21 may be any material as long as it emits photoelectrons when irradiated with radiation, and the smaller the photoelectric work function, the more preferable it is. From the viewpoint of effectiveness and economy, Ba,
Sr, Ca, Y, ()d, La.

Ce, Nd, Th, Pr, Be, Zr, F
e, Ni, Zn, Cu, Ag.

Pt, Cd, Pb, A4 C, Mg, Au,
In, Bi, Nb, Si,.

Any one of Ti, Ta, 8n, and P, or a compound or alloy thereof is preferred, and these may be used alone or in combination of two or more. As the composite material, a physical composite material such as amalgam can also be used.

For example, compounds include oxides, ferrides, and ashes, and oxides include Bad, SrO, and Cab.

Y2 o61 aa, o3. Nd2031 'rho
, , FE3203, Z no, Cuo.

A g20r P t+ Og P b OHA Z2
03 + M g O9I n203 + B 10+
There are NbO, BeO, etc., and borides include YB6°G4B6, LaB6, CeB6. PrB6
, ZrB2, etc., and carbides such as ZrC
, TaC, TiC, NbC, etc.

In addition, alloys include brass, bronze, and phosphor bronze.

Alloy of Ag and Mg (Mg 2-20 vrt%), C
An alloy of u and Be (1 to 10 wt% Be) and an alloy of Ba and AL can be used, and the above-mentioned Ag and M
An alloy of Cu and Be, and an alloy of Ba and Al are preferable. The oxide may be one in which only the surface of the metal plate is made into an oxide by heating the metal in air or oxidizing it with a chemical.

Still another method is to heat the material before use to form an oxidized layer on the surface to obtain a stable oxidized layer over a long period of time. As an example of this, a thin oxide film can be formed on the surface of an alloy of Mg and Ag in water vapor at a temperature of 500 to 400°C, and this thin oxide film is stable over a long period of time. .

These materials may be used in any shape such as plate, pleat, or net, but it is preferable to use a shape that has a large radiation irradiation area and a large contact area with air, and from this perspective, a net is preferable. is preferred.

The voltage to be applied is [1,1 to 15 kV, preferably α1 to 5 kV, more preferably 01 to 3 kV, but the voltage depends on the shape of the device, the material and structure of the electrode or photoelectron emitting material used. Varies depending on etc.

The radiation may be irradiated with any material that causes the photoelectron-emitting material to emit photoelectrons by the irradiation, and can be performed by a conventionally known method, but radiation that also has a bactericidal effect is preferred. For example, a 137 C8,60CO source with bactericidal activity is preferred. It can be determined as appropriate depending on the field of application, content, purpose, economic efficiency, etc. For example, in the biological field, it is preferable to use irradiation that also has a bactericidal effect.

For example, alpha rays, beta rays, gamma rays, etc. are used as radiation, and the irradiation means is 60°Cesium 157.
Methods that use radioactive isotopes such as strontium-90, radioactive waste produced in nuclear reactors, and radioactive materials that have been appropriately treated as radiation sources, methods that use nuclear reactors directly as radiation sources, electron beam accelerators, etc. Use methods such as those using particle accelerators.

When electron beam irradiation is performed using an accelerator, high-density irradiation can be achieved by performing it at low output, making it more effective. The acceleration voltage is 5
00 kV or less, preferably 50 kV to 300 kV
It is V.

Charged particles, including dead organisms, are removed by electrostatic filters.
Collected at -10. Any collector for charged particles may be used. A dust collection plate (dust collection electrode) or an electrostatic filter in a normal charging device is common, but a structure in which the collection part itself constitutes an electrode, such as a steel wool electrode, is also effective. Single-type electrostatic filters are effective in terms of ease of handling, performance, and economy, but they tend to clog after being used for a certain period of time, so they are designed as cartridges and are replaced when pressure loss is detected. This allows stable operation over a long period of time.

Instruments, products, etc. are taken in and out of the workbench 13 in the clean pliers 11 using a movable shutter 12 provided on the clean bench 11.

As a method of charging fine particles in the air, we have explained a method in which the metal surface of the photoelectron emitting material is irradiated with radiation to emit photoelectrons in an electric field with a relatively high voltage applied.
By irradiating a photoelectron emitting material with radiation without forming an electric field, fine particles in the air can be charged. In case B, the configuration for forming an electric field can be omitted in the embodiment shown in FIG.

Note that the positional relationship among the fan, radiation source, electric field, and photoelectron emitting material in the present invention varies depending on the type and scale of the air purification system, the airflow method, etc., and is not limited.

Types of air cleaning methods include methods that make a part of the work area highly clean, and methods that make the entire room highly clean, but the former is generally more economical.

When using the present invention in the field of biotechnology,
It is more effective to use nitrogen-enriched air, which was previously proposed by the present inventor (see Japanese Patent Application No. 59-21iS293).

It is also effective to carry out sterilization using ultraviolet lamps and the charging formula according to the method of the present invention, or sterilization using radiation and the charging method using ultraviolet rays (Japanese Patent Application No. 60-18723) already filed by the present inventor in combination. Needless to say.

〔Effect of the invention〕

1. By irradiating the photoelectron emitting material with radiation, or by irradiating the photoelectron emitting material with radiation in an electric field with a relatively high voltage applied, (1) Compared to the conventional electrostatic filtration method, This enables efficient charging of fine particles in the air.

(2) Since fine particles can be charged with high efficiency, a maple tree, for example, an electrostatic filter or a dust collection plate (dust collection electrode), is installed as a collection part for appropriate charged particles on the downstream side. Only with
Highly clean air can be obtained.

(3) Since ultrafine particles can be collected by being charged, it is possible to obtain an ultra-clean air room (super clean room).

(4) Compared to the conventional method of electrostatically collecting particles, it is safe because it does not require high voltage, and maintenance is easy and costs can be reduced.

2. By giving radiation a sterilizing effect, (1) sterilizing clean air can be obtained.

(2) It is particularly effective in fields where the presence of microorganisms has a particular influence, such as the field of biotechnology.

(3) In the field of biotechnology, the collection of charged particles does not have to be strict, and a small amount of leakage is tolerated, making it possible to create devices with low acid costs.

5. Although it was difficult to obtain ultra-high cleanliness (class 1, class 10) with the conventional technology, it can be easily achieved with the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a method using the clean pliers combination method of the present invention, and FIG. 2 is a schematic diagram showing an embodiment of the apparatus of the present invention. 1...Clean room, 3...Pre-filter, 4.
... Air intake port, 5... Fan, 6... Air conditioning room, 7... Filter, 8... Fan and air supply unit, 9... Radiation irradiation unit onto photoelectron emitting material, 10...
・Filter, 11...Clean pliers, 13...
Workbench, 20...Discharge electrode, 21...Photoelectron emission material, 22...Radiation source, 25...Rough filter 24...
・Electrostatic filter μter

Claims (1)

[Claims] 1. In a method of purifying the air by charging fine particles in the air by irradiating them with radiation and then removing the charged fine particles from the air, irradiating the photoelectron emitting material with radiation 1. A method for cleaning air, which comprises: generating photoelectrons, charging fine particles in the air with the photoelectrons, and then removing the charged fine particles. 2. The air cleaning method according to claim 1, wherein the fine particles in the air are charged with photoelectrons generated by irradiating the photoelectron emitting material with radiation in an electric field. 3. The air cleaning method according to claim 1 or 2, wherein the photoelectron emitting material is made of a substance with a small photoelectric work function. 4. The photoelectron emitting material is Ba, Sr, Ca, Y, Gd
, La, Ce, Nd, Th, Pr, Be, Zr, Fe,
Ni, Zn, Cu, Ag, Pt, Cd, Pb, Al, C
, Mg, Au, In, Bi, Nb, Si, Ta, Ti,
The air purifying method according to claim 3, wherein the air purifying method is made of one material selected from Sn, P, and compounds thereof. 5. The photoelectron emitting material is Ba, Sr, Ca, Y, Gd
, La, Ce, Nd, Th, Pr, Be, Zr, Fe,
Ni, Zn, Cu, Ag, Pt, Cd, Pb, Al, C
, Mg, Au, In, Bi, Nb, S1, Ta, Ti,
The air cleaning method according to claim 3, comprising a composite material or alloy of at least two or more materials selected from Sn, P, and compounds thereof. 6. The photoelectron emitting material is an alloy of Ag and Mg.
An air cleaning method according to claim 5. 7. The air cleaning method according to claim 5, wherein the photoelectron emitting material is an alloy of Cu and Be. 8. The photoelectron emitting material is an alloy of Ba and Al.
An air cleaning method according to claim 5. 9. The air cleaning method according to claim 5, wherein the photoelectron emitting material is made of one material selected from brass, bronze, and phosphor bronze. 10. The air cleaning method according to any one of claims 1 to 9, wherein the photoelectron emitting material has a net shape. 11. The electric field voltage is 0.1 to 15 kV, preferably 0.
The air cleaning method according to any one of claims 2 to 10, wherein the voltage is 1 to 5 kV, more preferably 0.1 to 3 kV. 12. On the air flow path from the air inlet to the air outlet,
An air purifying device comprising a radiation irradiation section on a photoelectron emitting material and a charged particle collection section sequentially provided. 13. The air purifying device according to claim 12, further comprising a device for applying an electric field to the radiation irradiation section onto the photoelectron emitting material.