JPH0674909B2 - 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

[Prior Art and Problems Thereof] The conventional indoor air cleaning methods or their devices are roughly classified into (1) a mechanical filtration method (for example, a HEPA filter), (2) electrostatic collection of fine particles. There are charging methods using voltage and filtration methods using a conductive filter (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 the fine flow particles, a high voltage of, for example, 15 to 70 kV is required in the pre-charging section, so the device becomes large and there is a problem in terms of safety and maintenance. I got it.

In order to solve these problems, the present inventor has proposed an air cleaning method by ultraviolet irradiation (Japanese Patent Application Laid-Open No. 61-178050, Japanese Patent Application No. 61-226792, Japanese Patent Application No. 61-293395, Japanese Patent Application No. 61-24427).
5, Japanese Patent Application No. Sho 61-293394).

In order to put these systems into practical use, it is necessary to carry them out under operating conditions (suitable UV irradiation conditions) suitable for the application field and application. That is, in the practical operation of these methods, it is necessary to improve the practicability and make it practically more advantageous.

In order to increase the practicality, it is preferable to simultaneously charge the fine particles and sterilize (sterilize) the microorganisms.

In particular, it is important in the biotechnology field where the presence of microorganisms poses a problem.

[Object of the Invention]

The present invention relates to a method and an apparatus for cleaning a gas such as air in which a photoelectron emitting material is irradiated with ultraviolet rays to charge the particles in a gas with the emitted photoelectrons and then the particles are removed. Is used in a range of 5 to 200 mWs / cm ² at a dose of 200 to 350 nm to effectively charge the fine particles and sterilize the microorganisms at the same time.

[Structure of Invention]

The present invention is: 1. In a method for cleaning a gas, which comprises irradiating a photoelectron emitting material with ultraviolet rays to emit photoelectrons, charging the microparticles contained in a gas by the photoelectrons, and then removing the charged microparticles from the gas, A method for cleaning a gas, which comprises irradiating ultraviolet rays having a main wavelength of 200 to 360 nm as ultraviolet rays.

2. The amount of ultraviolet rays is 5-200mWs / cm ² , preferably 5-40mWs / cm
^The method for cleaning gas according to claim 1, which is within the range of ² .

3. In the gas flow path from the gas inlet to the gas outlet, ultraviolet rays with a wavelength of 200 to 360 nm, which is the main wavelength of the photoelectron emitting material, are exposed to 5 to 20 nm.
A gas cleaning device provided with a photoelectron emission unit and a charged particle collection unit for irradiation with a dose of 0 mWs / cm ² .

Is.

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a clean bench combined system in a biological clean room, that is, a system in which only a part of the work area is highly clean.

FIG. 2 is a schematic view showing an embodiment of a photoelectron emitting portion by ultraviolet irradiation.

In the clean room 1, after the coarse particles of the outside air introduced from the pipe 2 are filtered by the ble filter 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 FIG. 2, a schematic view of the photoelectron emitting portion irradiated with ultraviolet rays is mainly shown in FIG.
1, consisting of an ultraviolet lamp 22, an electrode 20 and a photoelectron emitting material 21
A voltage is applied from the fan and the voltage supply unit 8 to the photoelectron emission material 21, ultraviolet rays are applied to the photoelectron emission material 21, and air 50 is passed between the electrode 20 and the photoelectron emission material 21. Are efficiently charged.

The distance between the electrode 20 and the photoelectron emitting material 21 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. 2, 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. Ba, Sr, C in terms of effect and economy
a, Y, Gd, La, Ce, Nd, Th, Pr, Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, Cd, P
b, Al, C, Mg, Au, In, Bi, Nb, Si, Ti, Ta, Sn, P or any of these compounds or alloys are preferable, and these are used alone or in combination of two or more kinds. To be As the composite material, a physical composite material such as amalgam can also be used.

For example, the oxide as a compound, boride, there are carbides, BaO in the _{oxide, SrO, CaO, Y 2 O} 6, Gd 2 O 3, Nd 2 O 3, ThO 2, 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, # copper, 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 10).
wt%) and an alloy of Ba and Al can be used.
Alloys of Mg with Mg, alloys of Cu with Be and alloys of Ba with Al are preferred. As the oxide, a metal plate whose surface is made oxide by heating the metal in air or oxidizing it with a chemical may be used.

As another method, it is possible to heat before use to form an oxide layer on the surface and obtain a stable oxide layer over a long period of time. An example of this is an alloy of Mg and Ag in steam
An oxide thin film can be formed on the surface of the oxide film at a temperature of 0 to 400 ° C, and the oxide thin film is stable over a long period of time.

The shape of these materials to be used may be any shape such as a plate shape, a pleat shape, and a mesh shape, but a shape having a large irradiation area of ultraviolet rays and a contact area with air is preferable, and from such a viewpoint, a mesh shape. Is preferred.

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 present inventor has separately proposed the shape of the surface of the photoelectron emitting material.

The applied voltage is 0.1 to 10 kV, preferably 0.1 to 5 kV, and more preferably 0.1 to 3 kV.
It depends on the material, structure, etc. of the electrode or photoelectron emitting material used.

The ultraviolet ray may be any one as long as the photoelectron emitting material emits photoelectrons upon irradiation thereof, and at the same time has a sterilizing (sterilizing) action on microorganisms such as viruses, bacteria, yeasts, molds, etc. As a result of various studies, the following results were found.

That is, when the main wavelength of ultraviolet rays is 200 to 360 nm, preferably 240 to 280 nm, it is practically convenient because the charging action to the fine particles and the bactericidal action of the microorganisms occur simultaneously at the same time.

The ultraviolet (average irradiation) dose is 5 to 200 mWs / cm ² , preferably 5 to 40 mWs / cm ^2, which is practically effective.

A larger amount of ultraviolet rays is more effective for charging fine particles and sterilizing microorganisms, but is economically problematic (increased irradiation cost). Therefore, it is necessary to appropriately determine the amount of ultraviolet rays depending on the application field, device shape, scale, effect, economical efficiency and the like. For example,
A large amount of dose is required for a device that requires considerably high cleanliness, such as a clean bench used in the biotechnology field, but 10-30 mWs / cm ² for an air purifier for a waiting room such as a hospital. (Relatively weak dose) is acceptable.

The ultraviolet ray source may be any one as long as it has the above wavelength and dose. Usually, a mercury lamp, particularly a sterilization lamp, a low-pressure lamp, and a medium-pressure lamp are preferable because of their effect and simplicity.

In the specific example shown in FIG. ^2, a germicidal lamp having an ultraviolet ray amount of 40 mWs / cm ² is used.

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) method or a method using an electrostatic filter, which is highly efficient and surely collects charged fine particles. 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.

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.

Further, in this embodiment, the photoelectron emitting material is irradiated with ultraviolet rays in the electric field, but it can be carried out even when there is no electric field. These can be appropriately determined depending on the shape, scale, kind, shape, application field, kind, shape, effect, economical efficiency, etc. of the device.

FIG. 3 shows an example of a hospital air purifier.

Reference numeral 500 ₁ is inlet air, 230 is a coarse filter, 100 is a fan,
Reference numeral 200 is an electrode, 210 is a lattice-shaped photoelectron emitting material, 220 is a germicidal lamp (30 mWs / cm ² ), 240 is an electrostatic filter, and 500 ₂ is the cleaned air at the outlet.

The operation of each is as described above.

Example A test was conducted using an air purifier having the shape shown in FIG. However, ultraviolet lamp; mercury lamp, 30W (main wavelength 254nm) or high pressure lamp, 30W (main wavelength 300 ~ 600n)
m) Electron emission material: brass plated with gold, 10cm x 20cm electric field voltage: 1kV, charged particle collection filter; electrostatic filter The generated particles are appropriately diluted with tobacco smoke (average particle size 0.3 to 0.4μm). Air was fed at 20 / min, and the concentration was measured at the inlet (behind the coarse filter) and the outlet (behind the electrostatic filter) using a particle measuring instrument.

In addition, as for the microorganisms generated, Leybacterium or Bacillus subtilis is generated by a nebulizer and is supplied to the flow path in the same manner as fine particles, and sample air is collected at the inlet and outlet (in front of the electrostatic filter) with an under-sensor sampler for microorganisms After culturing, the microbial concentration was measured. The amount of ultraviolet rays of the ultraviolet lamp is 2,8,40 mWs / cm ² .

The results are shown in Table 1.

[Advantages of the Invention] By using ultraviolet rays having an ultraviolet wavelength of 200 to 360 nm, i. Charging of fine particles and sterilization of microorganisms simultaneously occur effectively.

By using ultraviolet rays having an ultraviolet wavelength of 200 to 360 nm at a dose of 5 to 200 mWs / cm ² , i. Practically effectively, the charging of fine particles and the sterilization of microorganisms occur simultaneously.

ii. A sterilizing clean gas can be easily obtained and its practicality is improved.

iii. It is possible to provide a gas cleaning device that is practically effective in fields such as the biotechnology field where the presence of microorganisms particularly affects.

[Brief description of drawings]

FIG. 1 and FIG. 2 are drawings for explaining the gas cleaning method and apparatus of the present invention, which is used in combination with a clean bench in a biological clean room, and FIG. 3 is a hospital air cleaning apparatus to which the present invention is applied. It is drawing which shows an example. 1 ... Clean room, 6 ... Air conditioner, 8 ... Fan and voltage supply unit, 9 ... UV irradiation unit, 10 ... Filter, 11 ... Clean bench, 13 ... Workbench, 20,200
...... Electrode, 100 …… Juan, 21,210 …… Photoemissive material, 2
2,220 …… UV lamp, 24,240 …… Electrostatic filter

Claims (3)

[Claims] 1. A method for cleaning a gas, wherein a photoelectron emitting material is irradiated with ultraviolet rays to emit photoelectrons, the fine particles contained in a gas are charged by the photoelectrons, and then the charged fine particles are removed from the gas. As the main wavelength is 200
A method for cleaning a gas, which comprises irradiating ultraviolet rays of ~ 360 nm. 2. The amount of ultraviolet rays is 5 to 200 mWs / cm ² , preferably 5
The method for cleaning gas according to claim 1, wherein the gas is in the range of -40 mWs / cm ² . 3. A photoelectron emission unit for irradiating a photoelectron emission material with ultraviolet rays having a main wavelength of 200 to 360 nm at a dose of 5 to 200 mWs / cm ² on a flow path of gas from a gas intake port to a discharge port, and charging. A gas cleaning device provided with a particle trap.