JPS63147566A - Method and apparatus for cleaning gas - Google Patents

Abstract

PURPOSE:To miniaturize the apparatus and to easily maintain the operation by preliminarily removing electrostatically charged fine particles in a gas and electrostatically charging the noncharged fine particles in an gas cleaning method for removing the fine particle in the gas by photoelectrons. CONSTITUTION:The air 24 containing electrostatically charged fine particles is flowed through a preliminary catching filter 9 where positive and negative charged fine particles are removed. Then, neutral (noncharged) fine particles are electrostatically charged by an ultraviolet irradiation part consisting of a photoelectron emitting material 21 and an ultraviolet lamp 22. These charged fine particles are caught by a charged fine particle catching filter 23, and a clean air 25 is obtained. In this case, photoelectrons are emitted in the ultraviolet irradiation part 10 by irradiating the photoelectron emitting material 21 with ultraviolet rays from the ultraviolet lamp 22. By these photoelectrons, the fine particles in the air 24 are efficiently charged. As the charged fine particles are preliminarily removed, the photoelectrons are efficiently acted to charging due to low density of fine particles to be charged.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to: ■ clean rooms, clean booths, clean tunnels, clean pliers, A method for purifying gases such as air, oxygen, and nitrogen in safety cabinets, sterile rooms, bath boxes, sterile air curtains, clean tubes, etc.

■ Methods for cleaning gases emitted from various industries and industries, such as flue gas and automobile exhaust gas.

■ Air purification methods for homes, businesses, hospitals, etc.

and an apparatus for implementing the methods described in (1), (2), and (2).

Regarding.

[Conventional technology and its problems]

Conventional indoor air purification methods and devices can be roughly divided into: (1) Mechanical filtration methods (e.g. HKPA filter) (
2) There are filtration systems using high-voltage charging and conductive filters (for example, MKSA filters) that electrostatically collect fine particles, but each of these systems has the following drawbacks.

In other words, in the mechanical filtration method, 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. The life of the filter is short, and not only is it troublesome to maintain, manage, or replace the filter, but when replacing the filter, it is necessary to stop work during that time, and it takes a long time to recover. The drawback was poor production efficiency.

Additionally, in order to improve the cleanliness of the air, the number of times of ventilation (the number of times air is circulated by a fan) has been increased, but this has the drawback of increasing power costs.

In addition, conventional filter methods are only intended to remove particulates, so they can be used in industrial clean rooms, but filters almost always have pinholes, which can cause some of the contaminated air to leak out. Therefore, there were limits to its use in biological clean rooms.

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

In order to solve these problems, the present inventor proposed an air purification method using ultraviolet irradiation or radiation irradiation (Japanese Patent Application No. 18725/1982, Special Patent Application No. 85996/1983).
.

Although these methods are effective depending on the field of application, there is room for improvement in specific fields and applications. Improvements need to be made in such a way as to further improve practicality and make the method more practically advantageous.

These cleaning methods proposed above charge fine particles in the gas with photoelectrons emitted by irradiating a photoelectron emitting material with ultraviolet rays and/or radiation, and collect and remove the charged particles. be.

That is, since this method is a method of charging fine particles and collecting the charged particles, it can be said that in principle it is a particularly effective method for cleaning gases in which uncharged fine particles are present.

[Purpose of the invention]

The present invention efficiently charges the uncharged particles with Ho's device by removing the charged particles in advance before charging the uncharged particles present in the gas, and the charged particles The object of the present invention is to provide a method and apparatus for purifying gas by removing.

[Structure of the invention]

The present invention provides a gas that emits photoelectrons by irradiating a photoelectron emitting material with ultraviolet rays and/or radiation, charges fine particles contained in the gas with the photoelectrons, and then removes the charged fine particles from the gas. In the cleaning method of
A gas cleaning method and apparatus characterized in that charged fine particles in the gas are removed in advance.

Generally, positive, negative, and neutral (uncharged) fine particles coexist in a gas, for example, in the air. The proportion of these particles differs depending on the cause of their generation and the environment in which they exist, but for example, the proportion of positively and negatively charged particles in indoor cigarette smoke to the total concentration of generated particles is 6.
It can reach up to 80%.

Therefore, if these positively and negatively charged fine particles are collected and removed from the gas in advance, the number of symbolic particles to be collected and removed by the method of the present invention will be reduced, which is practically advantageous. .

That is, since the concentration of particulates is reduced, the ultraviolet ray and/or radiation irradiation section can be simplified and miniaturized, making operation management easier.

In addition, in the method proposed earlier in which positive, negative, and neutral (uncharged) fine particles are mixed and charged, they are charged positively or negatively depending on the charging atmosphere and charging conditions, and the charged particles at the rear are not captured. Two types of particulate collecting parts, positive and negative, are required, which can sometimes be troublesome to handle.

On the other hand, if charged particles, such as positively and negatively charged particles, are collected and removed in advance, only neutral (uncharged) particles need be charged, which makes charging easier and handling easier. In other words, the charge of only neutral (uncharged) particles is
It is easy to handle because it can be charged only negatively.

The present invention collects and removes positively and/or negatively charged particles in the gas in advance, charges only the uncharged particles that have passed through without being collected, and collects and removes the charged particles at the rear. It is something to do.

Hereinafter, the present invention will be explained in more detail based on the drawings.

Based on FIG. 1, an air cleaning method using an ultraviolet irradiation method or a method in combination with a clean bench in an IJ room, that is, a method of keeping only a part of the working area at a high level of cleanliness, will be explained.

Inside the clean room 1, after filtering the coarse particles of the outside air introduced from the pipe 2 with a pre-filter 5, the air is taken out from the air outlet 4 of the clean room 1 and passed through the fan 5 to the air conditioner 6. Air is circulated and the temperature and humidity are adjusted and particulates are removed by HEPA filter 7, and the cleanliness (class) is 10,000.
It is maintained at a certain level.

On the other hand, inside the clean room 1, there is a fan section 8, a preliminary collection filter 9, an ultraviolet irradiation section 10. The workbench 13 in the clean pente 12 provided with the filter 11 is maintained in a sterile atmosphere of high cleanliness (class 10).

That is, in the clean pliers 12, air with a cleanliness IQ of about 0,000 in the clean room 1 is sucked by the fan in the fan section 8, and the pre-collection filter 9 naturally collects the load 1 in the air. (Charged) and transmitted positive and negative particles are collected and removed.

Next, the fine particles in the air that are not collected or removed by the preliminary collection filter 9 and pass through are charged by photoelectrons emitted by irradiating the photoelectron emitting material with ultraviolet rays in the ultraviolet irradiation section 10, and virus After microorganisms such as bacteria, yeast, and mold are sterilized, the filter 10 removes the charged particles, thereby maintaining the workbench 15 at a high level of cleanliness.

Instruments, products, etc. are taken in and out of the workbench 15 in the clean bench 12 using a movable shutter 14 provided on the clean pliers 12.

A preliminary collection filter 9 that collects fine particles that are naturally charged (electrified) in the air, which is a feature of the present invention; an ultraviolet irradiation unit 10 that mainly charges neutral (uncharged) fine particles; The charged particle collection filter 11 is schematically shown in FIG.

That is, the air 24 containing charged particles sucked by the fan of the fan section 8 is collected and removed by the pre-collection filter 9, and then is mainly After neutral (uncharged) fine particles in the air are charged by the ultraviolet irradiation unit 10 consisting of a photoelectron emitting material 21 and an ultraviolet lamp 22, the charged fine particles are collected by a charged fine particle collection filter 25, and clean air 25 is generated. can get.

In the ultraviolet irradiation section 10, photoelectrons are emitted by irradiating the photoelectron emitting material 21 with ultraviolet rays from the ultraviolet lamp 22, and fine particles in the air 24 are efficiently charged by the photoelectrons.

The preliminary collection filter 9 may be of any type as long as it can collect positively and/or negatively charged particles in the air, and any known method can be used as appropriate.

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.

Furthermore, electret materials can also be suitably used.

Furthermore, a method of collection using an ion exchange filter, which has already been proposed by the present inventor, is also effective.

For collection, these collection methods can be used alone or in combination of two or more of these methods as appropriate.

Among these collection methods, preferable methods include single-filter methods, such as methods using ion exchange filters (anion exchange filters, cation exchange filters), and electrostatic filters, which are highly efficient and can reliably collect charged particles. This is convenient because it allows you to

In particular, in addition to fine particles, ion exchange filters can also
Since tars and odorous substances can be collected and removed at the same time, this method is effective depending on the application field and use of this device.

Does the photoelectron emitting material 21 emit photoelectrons when irradiated with ultraviolet light? Any material may be used as long as it emits light, and the smaller the photoelectric work function, the more preferable it is. From the viewpoint of effectiveness and economy, Ba, Sr
, Ca, Y, Gd, La, Co, Ncl.

Th, Pr, Be, Zr, Fe, Ni, Zn, Cu, A
g, Pt, Cd, Pb, AI.

C, Mg, Au, In, Bi, N'b, Si, T
Any one of i, Ta, Sn, and P, or a compound, alloy, or mixture 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 carbides, and oxides include BaO, SrO, OaO, and Y2O6.

Gdvos r Nd103 * Th01 HZr0
1, Fe, 031 ZnO, OuOlAg20.

PtO, PbO, AI, ○s * Mgo + engineering n1o
1, BiO, Nb0, 13eO, etc., and borides include YB, , GdB, , LaB6.
CeB, .

PrEs, ZrB, etc., and carbides include ZrC, TaC, Tic! , NbC, etc.

In addition, alloys include brass, bronze, phosphor bronze, Ag and Mg.
(2-20 wt% Mg), Cu and Be
(Be 1-10 wt%) and Ba and A
An alloy with I can be used, and the alloys of Ag and Mg, alloys of Cu and Be, and alloys of Ba and AI are preferred. Oxides can also be obtained by heating only the metal surface in air or by oxidizing it with chemicals.

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, an 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 oxide thin film is stable for a long period of time.

These materials may be used in any shape, such as a plate, pleats, curved surface, or net, but it is preferable to use a shape that has a large area of irradiation with ultraviolet rays and a large area of contact with air. Reticulated ones are preferred.

The shape of the photoelectron emitting material varies depending on the shape and structure of the device, desired efficiency, etc.

Emission of photoelectrons from the photoelectron emitting material can be effectively carried out by appropriately using a reflective surface, a curved reflective surface, etc., as already proposed by the present inventor.

The type of ultraviolet rays may be any type as long as the photoelectron emitting material can emit photoelectrons when irradiated with the ultraviolet rays, but it is preferable to use ultraviolet rays that also have a bactericidal effect.

It can be determined as appropriate depending on the field of application, work content, purpose, economic efficiency, etc. For example, in the biological field, it is preferable to use deep ultraviolet rays together in terms of bactericidal action and efficiency.

Charged particles containing dead microorganisms are filtered through filter 1.
Collected on 1,25.

Any collector for charged particles may be used.

It may be the same as the preliminary collection filter 9. 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. Electret materials can also be suitably used.

Furthermore, a method of collection using an ion exchange filter, which has already been proposed by the present inventor, is also effective.

For collection, these collection methods can be used alone or in combination of two or more of these methods as appropriate.

Among these collection methods, preferable methods include filter-based methods such as ion-exchange filters (anion-exchange filters, cation-exchange filters), and electrostatic filters, which are highly efficient and can reliably collect charged particles. This is convenient because it allows you to

Preliminary collection filter 9 and charged particle collector 1
1.25 can be selected and used as appropriate depending on the field of application of the device, structure, charge state of fine particles, effect, economical efficiency, etc.

For example, a case where an ion exchange filter (anion exchange filter, cation exchange filter) is used as the preliminary collection filter 9 and the charged particle collector 11.23 will be described below.

The type, filling amount, and ratio of the anion exchange filter and cation exchange filter to be used depend on the charge state and concentration of charged particles in the gas flow, or the type and concentration of accompanying acidic gas, alkaline gas, and odorous gas. It can be determined as appropriate.

For example, anion exchange filters are effective for collecting loaded electrical particles and acidic gases, and cation exchange filters are effective for collecting positively charged particles and alkaline gases. The filling amount of the filter and its ratio can be determined appropriately according to the concentration and concentration ratio of the substance to be collected as described above, taking into consideration the shape, structure, pressure drop, etc. of the device. .

Single-filter types are easy to handle, have good performance,
Although it is effective from the point of view of economy, since clogging occurs after use for a certain period of time, stable operation can be achieved over a long period of time by using a cartridge structure as necessary and replacing it by detecting pressure loss.

In addition, as a method of charging fine particles in the air, we have explained a method of charging without forming an electric field on the charging part, but it is possible to charge photoelectrons by irradiating the photoelectron emitting material with ultraviolet rays in an electric field with a relatively high voltage applied. is released efficiently,
It is also possible to efficiently charge particles in a gas flow.

Moreover, the same effect can be obtained by irradiating the fine particles with radiation instead of irradiating them with ultraviolet rays.

Further, the preliminary collection filter 9 may collect both positive and negative particulates as in this embodiment, but if the charge (electrification) of the particulates is biased toward either positive or negative, In some cases, only one side may be collected.

When installing the preliminary collection filter 9, a coarse filter for collecting relatively coarse particles may be installed in front.

In this embodiment (FIG. 2), the photoelectron emitting material 21 and the ultraviolet lamp 22 are positioned perpendicular to the airflow, but they may also be provided parallel to the airflow. 22 may be placed outside (in the airflow) of the clean pliers 12.

In addition, the photoelectron emitting material 21 is irradiated with ultraviolet rays in a spot (
Irradiation (with narrowing down using a lens, etc.) or full-scale irradiation can be selected and used as appropriate depending on the device structure, field, scale, material, shape, effect, economical efficiency, etc. of the photoelectron emitting material.

Further, the photoelectron emission from the photoelectron emitting material 21 can be effected by using a reflective surface, as already proposed by the present inventor.

〔Effect of the invention〕

1. By collecting and removing the already charged fine particles present in the gas in advance, (1) the concentration of the fine particles to be charged is reduced, so that the action of photoelectrons on the fine particles can be carried out effectively. Moreover, the energy of ultraviolet rays or radiation can be used effectively.

■ Since fine particles can be charged reliably and with high efficiency, highly clean gas can be obtained simply by installing an appropriate charged particle collection unit such as an electrostatic filter or ion exchange filter on the downstream side. .

■ Ultrafine particles can also be charged and collected, making it possible to create ultra-clean air chambers.

■ The device, especially the charging part and the charged particulate collection part, can be easily and miniaturized, operation management becomes easier, and practicality is improved.

By using one type of filter as the λ pre-collection filter or the collector for charged particles, ■ The collection of charged particles becomes reliable and highly efficient, improving practicality and becoming a practically advantageous method. .

■ As a single filter type, especially by using an ion exchange filter, acidic gases (e.g., H, S, HO/), alkaline gases (e.g., NII!, ), tars, and odorous substances can be collected and removed at the same time. Therefore, depending on the field of application and use, this method is more advantageous in practice.

(5) By irradiating with ultraviolet rays or radiation, ■ Sterilized and clean gas can be obtained.

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

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an example of the method of the present invention, FIG.
The figure is a preliminary drawing for explaining a charged particulate preliminary collection part, a charging part, and a charged particulate collection part according to the present invention. 1-Clean room, 3...-Prefilter-14-...
・Air outlet, 6-...Air conditioner, 7-...HE
PA filter, 8--Fan section, 9--Preliminary collection filter, 10--Ultraviolet irradiation section, 11--
・Filter, 12-Clean pliers, 15--Workbench, 21--Photoelectron emitting material, 22--Ultraviolet lamp, 25-Filter, Patent applicant: Ebara Research Institute, Ltd. Ebara Corporation Manufacturer

Claims (1)

[Claims] 1. A photoelectron emitting material is irradiated with ultraviolet rays and/or radiation to emit photoelectrons, fine particles contained in a gas are charged by the photoelectrons, and then the charged fine particles are converted into a gas. 1. A gas cleaning method characterized in that charged fine particles in the gas are removed in advance. 2. In an electric field, photoelectrons generated by irradiating the photoelectron emitting material with ultraviolet rays and/or radiation,
Claim 1, wherein the fine particles in the gas are charged.
Gas purification method described in section. 3. The gas 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,
4. The gas cleaning method according to claim 3, comprising one of materials 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, Si, Ta, Ti,
The gas cleaning method according to claim 3, comprising an alloy, a mixture, or a composite material 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.
A gas cleaning method according to claim 3. 7. The photoelectron emitting material is an alloy of Cu and Be.
A gas cleaning method according to claim 3. 8. The photoelectron emitting material is an alloy of Ba and Al.
A gas cleaning method according to claim 3. 9. The gas cleaning method according to claim 3, wherein the photoelectron emitting material is made of one material selected from brass, bronze, and phosphor bronze. I0. The gas cleaning method according to any one of claims 1 to 9, wherein the photoelectron emitting material has a net shape. 11. According to any one of claims 2 to 10, the electric field voltage is 0.1 to 10 kV, preferably 0.1 to 5 kV, more preferably 0.1 to 1 kV. gas purification method. 12. The gas cleaning method according to any one of claims 1 to 11, wherein charged particles in the gas are collected and removed in advance using an ion exchange filter or an electrostatic filter. 13. On the gas flow path from the gas inlet to the gas outlet,
A gas purification device comprising a preliminary collection section, an ultraviolet ray or radiation irradiation section, a photoelectron emission section, and a charged particle collection section. 14. On the gas flow path from the gas inlet to the gas outlet,
14. The gas purifying device according to claim 13, which comprises a preliminary collection section, an ultraviolet ray or radiation irradiation section, an electric field, a photoelectron emission section, and a charged particle collection section.