JP2623290B2 - Gas cleaning method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention relates to a process for producing a gas stream containing particulate matter and gaseous pollutants such as acidic gas, alkaline gas and odorous gas.
The present invention relates to a method and an apparatus for removing gaseous pollutants such as an acidic gas, an alkaline gas and / or an odorous gas together with the particulate matter.

More specifically, clean rooms, hyological clean rooms, clean booths in the electronics industry, pharmaceutical industry, food industry, agriculture and forestry industry, medical care, precision machinery industry, etc.
Clean tunnel, clean bench, safety cabinet, bio-clean unit, sterile room, bath box,
Air in aseptic air curtains, clean tubes, etc.
A method for purifying gases such as oxygen and nitrogen.

A method for purifying gases discharged from various industries, such as flue gas and automobile exhaust gas.

 Air purification method in homes, offices, hospitals, etc.

And an apparatus for performing the described method.

It is about.

[Conventional technology and its problems]

Conventionally, removal of particulate matter from gas streams, acid gas,
Removal of gaseous contaminants such as alkaline gas and odorous gas has been performed by separate methods and apparatuses.

For example, the method of removing particulate matter (solid particles) in a room or the like can be roughly classified into: (1) Mechanical over-method (for example, HEPA filter) (2) Charging by high voltage that electrostatically collects fine particles There are two methods, that is, a method using a conductive filter and an over-type method (for example, a MESA filter). These methods have the following disadvantages.

That is, in the mechanical over system, it is necessary to use a fine filter in order to increase the cleanliness (class) of the air. In this case, however, the pressure loss is high, and the increase in the pressure loss due to clogging is also remarkable. , The filter life is short,
Not only is maintenance, management or replacement of the filter troublesome, but when replacing the filter, it is necessary to stop the work during that time, and it takes a long time to return, and the production efficiency is poor. Atsuta.

In addition, in order to increase the cleanliness of the air, the number of ventilations (the number of air circulations by fans) is also increased,
In this case, there is a disadvantage that the power cost is high.

In addition, since the conventional filter method is intended only for removing fine particles, it can be used for industrial clean rooms, but the filter always has pinholes as much as possible and some of the contaminated air leaks For,
There is a limit to its use in biological clean rooms.

In the method of electrostatically collecting fine particles,
Since a high voltage of, for example, 15 to 70 KV is required for the preliminary charging unit, the device becomes large, and there are problems in terms of safety and maintenance.

On the other hand, gaseous pollutants have been carried out by passing a gas containing them through an adsorbent, for example, a layer filled with activated carbon, and adsorbing the adsorbent.

As described above, the removal (collection) of particulate matter and gaseous pollutants has been performed using separate methods and devices, respectively, so that the devices are complicated and large, and maintenance and management are troublesome. There was.

On the other hand, as a method for removing particulate matter, the present inventor has previously proposed an air cleaning system by irradiating ultraviolet rays or radiation (Japanese Patent Application Nos. 60-18723 and 61-85996). This method also has a drawback that when a dust collecting plate (dust collecting electrode) is used as a method for collecting charged particulate matter, gaseous pollutants cannot be collected.

[Object of the invention]

It is an object of the present invention to provide a method and apparatus for simultaneously removing particulate matter and gaseous pollutants in a gas stream.

[Configuration of the invention]

SUMMARY OF THE INVENTION The present invention provides a method for producing a gas containing particulate matter and gaseous pollutants by irradiating the gas containing ultraviolet light and / or radiation onto a photoelectron emission material and a photocatalyst material by photoelectrons. The substance is charged, and the charged particles are collected and removed by a charged particle collection section downstream, and gaseous pollutants such as SO ₂ , H ₂ S, NOx, NH ₃ , and O coexist due to the action of a photocatalyst. _It decomposes and removes various solvents and solvents and / or malodorous substances such as mercaptans, sulfides, thiophenes, and turn-like substances.

It also kills and removes microorganisms and bacteria by the action of ultraviolet energy and photocatalyst.

 Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a system using a bioclean unit in a biological clean room, that is, a system in which only a part of the working area is highly clean.
It is the schematic which shows the Example of an ultraviolet irradiation part, a photoelectron emission part photocatalyst part, and a fine particle collection part.

In the clean room 1, coarse particles in the outside air introduced from the pipe 2 are passed through the pre-filter 3, and then together with the air taken out from the air outlet 4 of the clean room 1 via the fan 5 in the air conditioner 6. After adjusting the temperature and the 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 worktable 13 in the bioclean unit 11 provided with the fan and coarse filter unit 8, the ultraviolet irradiation units 9 ₁ and 9 ₂ and the fine particle collection units 10 ₁ and 10 ₂ in the clean room 1 has high cleanliness ( The sterile atmosphere of class 10) is maintained, and the air discharged from the bioclean unit 11 is also sterile and clean air and discharged.

That is, in BIOCLEAN Units - 11 is sucked cleanliness in the clean room 1 (class) 10,000 about air by Juan Juan and coarse filter unit 8, at the entrance of the ultraviolet irradiation unit 9 ₁ photoelectron emitting material and photocatalytic material with particles in the air is charged by irradiating the ultraviolet rays, odorous gases are decomposed and removed, viruses, Bakuteriya, yeast, after microorganisms mold or the like is sterilized, microparticles charged at the inlet of the filter 10 ₁ By removing
The worktable 13 is kept at a high cleanliness.

Microorganism has occurred in the working platform, the secondary product gas odorous gases such as generated by fine particles and work including the bacteria is irradiated with ultraviolet rays the ultraviolet irradiation unit 9 _second outlet, as well as the fine charged as above, decomposition of odorous gases, and subjected to sterilizing action, charged fine particles are trapped by the filter 10 _{and second} outlet, sterile, high clean air is discharged. The features of the bioclean unit 11 are mainly composed of a UV irradiating section for irradiating ultraviolet rays or radiation onto the photoelectron emitting material and the photocatalyst material, and a filter section, and a schematic diagram thereof is shown in FIG.
That is, the coarse filter 100, the fan 20, the ultraviolet lamps 30, 3
1, composed of photoelectron emission materials 40, 41, photocatalyst materials 50, 51, electrodes 70, 71, charged particle trapping filters 80, 81, and work table 13; moving and unloading of equipment and products to and from work table 13 Perform according to 12.

The air 60 in the clean room 1 is sucked after coarse particles are removed by the coarse filter 100 by the fan 20 and then. In the clean unit 11, a voltage is applied from a voltage supply unit (not shown) between the electrodes 70, 71 and the photoelectron emitting materials 40, 41, and ultraviolet light is applied to the photoelectron emitting materials 40, 41 and the photocatalytic materials 50, 51. Irradiation between the electrodes 70 and 71 and the photoelectron emission materials 40 and 41.
By passing through 90 and 91, the fine particles in the air 90 and 91 are efficiently charged, and the odorous gas is decomposed and removed.
The distance between the electrodes 70, 71 and the photo-emissive materials 40, 41 depends on the shape of the device, but is generally preferably 2 to 20 cm, particularly preferably 3 to 10 cm.
cm is preferred.

The material of the electrode and its structure may be those used in a normal charging device. Usually, a tungsten wire is used. In FIG. 2, the charged fine particle collecting filters denoted by reference numerals 80 and 81 are electrostatic filters.

The operation of the ultraviolet irradiation unit and the filter unit in front and behind the clean unit 11 will be described.

At the front, the photoelectron emission material 40 and the photocatalyst material 50 are irradiated by the ultraviolet lamp 30 at the entrance. The photoelectron emission material 40 is
It emits photoelectrons, thereby efficiently charging fine particles in the air stream. On the other hand, a trace amount of odorous gas is decomposed and removed by the photocatalyst 50. In addition, microorganisms and bacteria die due to ultraviolet energy, the action of a photocatalyst, and the like. Charged fine particles containing dead microorganisms and bacteria are collected by the filter 80, and highly clean and sterile air is supplied to the workbench 13.

In the rear, for example, operations on microorganisms and bacteria in the operation of the work table 13, a new microorganism,
Bacteria may form and flow to the downstream. Also, by using reagents and gases, etc., acid gas, alkaline gas,
Odorous gases (gaseous pollutants) are generated and flow to the downstream. Therefore, the photoelectron emission material 41 and the photocatalyst material are irradiated by the ultraviolet lamp 31 in the downstream of the work table 13 as described above.
Here, ultraviolet energy, microorganisms and bacteria are killed by the action of the photocatalyst 51, and odorous gas is oxidized and decomposed by the action of the photocatalyst, and microorganisms that are generated and charged are charged particulate matter containing bacteria, The charged fine particles containing bacteria are collected by the filter 81, and the clean and sterile air 61 is discharged.

In the above description, the case where the direction of the airflow flows from the top to the bottom has been described, but the airflow direction is not limited at all, and can be appropriately determined according to the type of work such as the lateral direction, the type, the scale of the device, the shape, the economic efficiency, and the like. .

Also, the photocatalyst material was installed both on the front and back,
Either one can be appropriately determined depending on the properties of the gas, the form and type of operation, the scale and shape of the apparatus, and the like.

In addition, the sterilizing effect and the decomposition of odorous gas can be improved by using an ultraviolet lamp as an ozone generating lamp or combining an ordinary ultraviolet lamp with an ozone generating lamp (sterilization by ozone and odorous gas). Of the work, the type of work, the scale of the equipment,
It can be determined as appropriate depending on performance, economy, and the like. in this case,
The generated ozone is decomposed by the photocatalyst, so that the leakage waste ozone has a low concentration.

The photoelectron emitting materials 40 and 41 may be any materials that emit photoelectrons by irradiating ultraviolet rays, and those having a small photoelectric work function are preferable. In terms of effectiveness and economy, Ba, S
r, Ca, Y, Gd, La, Ce, Nd, Th, Pr, Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, C
d, Pb, Al, C, Mg, Au, In, Bi, Nb, Si, Ta, Sn, P or any of these compounds or alloys is preferable, and these may be used alone or in combination of two or more. Can be As the composite material, a physical composite material such as amalgam can 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,
ZrO ₂ , Fe ₂ O ₃ , ZnO, CuO, Ag ₂ O, PtO, PbO, Al ₂ O ₃ , MgO, In ₂ O ₃ , Bi
O, NbO, BeO, etc., and the borides are YB ₆ , GdB ₆ , La
B ₆ , CeB ₆ , PrB ₆ , ZrB _{2 and the} like.
There are rC, TaC, TiC, NbC and the like.

The alloys include brass, bronze, phosphor bronze, an alloy of Ag and Mg (Mg is 2 to 20 wt%), and an alloy of Cu and Be (Be is 1 to
10wt%) and alloys of Ba and Al can be used.
An alloy of Ag and Mg, an alloy of Cu and Be, and an alloy of Ba and Al are preferable. Oxides can also be obtained by heating the metal surface alone in air or oxidizing it with chemicals.

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

 Next, the photocatalyst will be described.

Any photocatalyst material can be used as long as it is excited by light irradiation and can decompose and remove gaseous pollutants.

Generally, semiconductor materials are preferable because they are effective, easily available, and have good workability.

In terms of effect and economy, Se, Ge, Si, Ti, Zn, Cu, Al, Sn, G
a, In, P, As, Sb, C, Cd, S, Te, Ni, Fe, Co, Ag, Mo, Sr, W, Cr, Ba, P
Preferred is any one of b, their compounds, alloys, or oxides. These may be used alone or in combination of two or more.

For example, the elements are Si, Ge, Se, and the compound is AlP,
AlAs, GaP, AlSb, GaAs, InP, GaSb, InAs, InSb, CdS, CdSe, Zn
S, MoS ₂ , WTe ₂ , Cr ₂ Te ₃ , MoTe, Cu ₂ S, WS ₂ , oxide as Ti
O ₂ , Bi ₂ O ₃ , CuO, Cu ₂ O, ZnO, MoO ₃ , InO ₃ , Ag ₂ O, PbO, SrTiO ₃ , Ba
_{TiO 3, Co 3 O 4,} Fe 2 O 3, there is NiO or the like.

As shown in FIGS. 2 and 3, the installation position of the photocatalyst material is fixed in the airflow and fixed to the wall surface, and the photocatalyst material can be used by being suspended in the airflow. The immobilization of the photocatalyst material, coating the photocatalyst material on the surface of glass or glassy substance or coating the photocatalyst material on a suitable material such as plate, line, net, film or fiber, or wrapping, or You may pinch and fix and use. The photocatalyst can be used as it is in the form of a powder, but can also be used in an appropriate shape by a known method such as sintering, vapor deposition, or sputtering.

These can be appropriately selected depending on the scale and shape and type of the device, the type and shape of the light source, the type of photocatalyst, the desired effect, the economic efficiency, and the like.

Further, in order to improve the photocatalytic action, Pt, A
A substance such as g, Pd, KOH, RuO ₂ or Co ₃ O ₄ can be added and used.

In the illustrated example, the photoelectron emission material and the photocatalyst material are separately provided. However, a material having both functions may be used. For example, a material having both photoemission and photocatalytic functions, for example, Si, Ti, Zn, Cu, Al, Sn, P, C, Ni, Ag, Sr, P
Either b or Cd, or a compound, an alloy, or an oxide thereof is used, and these are used alone or in combination of two or more. Further, the photoelectron emission material and the photocatalyst material can be mixed or combined.

Whether the photoelectron emission material and the catalyst material are separately provided or a material having both functions can be determined depending on the application field, type, scale of the apparatus, performance, economy, and the like.

The use shape of these materials may be any of a plate shape, a pleated shape, a curved surface shape, a linear shape, a film shape, a fiber shape, and a net shape,
A shape having a large ultraviolet irradiation area and a large catalyst area with air is preferable, and a net-like shape is preferable from such a viewpoint.

The type of the ultraviolet light may be any as long as the photoelectron emitting material can emit photoelectrons by the irradiation and has a wavelength that can be absorbed by the photocatalyst material.

As the light source, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, or the like can be appropriately used alone or in combination of two or more.

The voltage applied between the electrode and the photoelectron emitting material or photocatalyst material is 0.1 to 10 KV, preferably 0.1 to 5 KV, more preferably
The voltage is 0.1 to 3 KV, but the voltage varies depending on the shape of the device, the material or structure of the electrode or photoelectron emitting material used, the photocatalytic material, and the like. By using the photoelectron emission material and the photocatalyst material in an electric field, the respective effects are enhanced.

Any collector may be used for collecting the charged fine particles. Generally, a dust collecting plate (dust collecting electrode) or an electrostatic filter system in a normal charging device is used. However, a structure in which a collecting unit itself forms an electrode, such as a steel wool electrode, is also effective. Further, a method using an ion-exchange filter already proposed by the present inventors is also effective (Japanese Patent Application Nos.
-221792) The electrostatic filter method is effective in terms of easy handling, performance and economy, but it causes clogging after a certain period of use, so if necessary, use a cartridge structure and detect pressure loss. By performing the replacement, stable operation can be performed for a long period of time.

It is to be noted that the use of an ion-exchange filter is advantageous because both particulates and gaseous pollutants can be collected and removed.

That is, the action of the photocatalyst roughly decomposes and removes gaseous pollutants, and it is possible to collect and remove them to an extremely low concentration with a downstream ion exchange filter.

In the method of charging fine particles in the air, the method of irradiating photoelectron emission material and photocatalyst material with ultraviolet rays to emit photoelectrons in an electric field to which a relatively high voltage is applied has been described. By irradiating the emitting material and the photocatalytic material with ultraviolet rays or radiation, it is possible to charge fine particles in the air and to decompose and remove gaseous pollutants. In this case, the configuration for forming the electric field in the embodiment of FIG. 2 can be omitted.

The positional relationship among the fan, the ultraviolet light source, the radiation source, the electric field, the photoelectron emitting material, and the photocatalyst material in the present invention differs depending on the type and scale of the cleaning system, the method of airflow, and the like, and is not limited.

In the irradiation of ultraviolet rays or radiation, the photoelectron emission material and the photocatalyst material can be effectively irradiated by using the reflecting surface as already proposed by the present inventors (Japanese Patent Application No. 61-24427).
Five).

The above-mentioned bio-clean unit 11 is a system in which room air is sucked and discharged by the fans 8 and 20 to make a positive pressure in the vicinity of the work table. Needless to say, the method may be used. In addition, the air purifying mechanism has been described in which the working space is narrow and the suction side and the discharge side are provided on both sides. However, it is needless to say that either one may be used depending on the application field, application, apparatus scale, type economical efficiency, and the like. Nor.

Next, FIG. 3 is a schematic view showing an example of the air purifier of the present invention used in homes, offices, hospitals and the like.

The indoor contaminated air 101 is sucked by the fan 102. Coarse particles are removed by the coarse filter 103. The fine particles are charged by photoelectrons emitted from the metal surface 105 as a photoelectron emitting material irradiated by the ultraviolet lamp 104, and the odorous gas is decomposed and removed by the photocatalyst. In the vicinity of the ultraviolet lamp, the sterilizing action is maintained by the ultraviolet energy and the photocatalyst.

A voltage is applied between the photo-emissive material 105 and the electrode 107.

The photoelectron emission material 105 and the photocatalyst material 106 are efficiently irradiated with ultraviolet light from the ultraviolet lamp 104 by a reflection surface (not shown).

The charged fine particles are collected by a downstream electrostatic filter 108, and high-purity air 109 is discharged.

Each configuration and operation are as described in FIGS. 1 and 2.

Example 1 A test was performed using the air purifier shown in FIG.

However, ultraviolet lamp; mercury lamp (20W) Photoelectron emission material; brass Electric field voltage; 1KV photocatalyst material; Pt 0.2% supported on TiO ₂ Charged particle collection filter; electrostatic filter The generated fine particles are cigarette smoke (average Using a particle diameter of 0.3 to 0.4 μm), the mixture was appropriately diluted with clean air and supplied with air at a rate of 20 / min, and the concentration was measured at the inlet (behind the coarse filter) and the outlet (behind the electrostatic filter) using a particle meter.

In addition, H ₂ S and NH _{3 were} each supplied with 5.0 ppm in the same manner, and the concentration at the outlet was measured. The O ₃ concentration at the outlet was also measured.

 Table 1 shows the results.

In Comparative Example 1 in Example 1, it was examined H ₂ S and NH ₃ concentration at the outlet of the case not including the photocatalytic material.

The results were 4.8 ppm for H ₂ S and 4.5 ppm for NH ₃ .

Comparative Example 2 In Example 1, the concentration of fine particles at the outlet when no electron emitting material was installed was examined.

 The result was 0.08 mg / 960,000 /.

〔The invention's effect〕

1. The use of a photoelectron emission material and a photocatalyst material as a method of collecting and removing particulate pollutants such as particulate matter and acidic gas, alkaline gas, odorous gas, etc. (1) Particulate matter and acidity in gas particles Gaseous pollutants such as gas, alkaline gas, and odorous gas can be removed with a single device with high efficiency.

(2) Since the bactericidal action of microbial bacteria by the photocatalyst is added to the ultraviolet energy, the bactericidal effect is enhanced.

(3) Particles and gaseous contaminants in the gas stream are collected with high efficiency so that the flow to the downstream is substantially negligible, and a sterilized ultra-clean gas stream is obtained.

(4) It can be applied to various fields and applications, and especially to the degradation that is affected by the presence of microorganisms especially in the clean room related, especially biotechnology related, which was limited and difficult in the conventional method. Particularly effective equipment can be provided.

2. Since a photocatalyst material is used, (1) When a lamp capable of generating ozone is used as an ultraviolet lamp, the effect of disinfecting microorganisms and bacteria and the effect of decomposing and removing odorous gas are further enhanced.

(2) Since ozone is decomposed by the photocatalyst, the concentration of leaked waste ozone is reduced.

(3) When an ion-exchange filter is used for collecting charged fine particles, the ion-exchange filter can collect and remove gaseous pollutants at the same time. Thus, depending on the application field and the device, a suitable device can be made.

For example, it is possible to roughly remove the decomposition of gaseous pollutants by using a photocatalyst, and to collect and remove to an extremely low concentration by using a downstream ion exchange filter.

3. By using the photocatalyst material in an electric field, the effect of decomposing and removing the photocatalyst on gaseous pollutants and the effect of bacteria on microorganisms and bacteria are enhanced.

In other words, the action of the photocatalyst is considered that when the photocatalytic material absorbs the energy of light, oxygen active species (eg, active oxygen, OH radicals) are generated, and a chemical reaction (decomposition action and sterilization action) is caused.

The use of a photocatalytic material in an electric field effectively produces these oxygen-active species and promotes a chemical reaction.

[Brief description of the drawings]

1, 2 and 3 are schematic diagrams for explaining the method and apparatus of the present invention. 1 ... clean room, 3 ... pre-filter, 6 ...
Air conditioning room, 7… HEPA filter, 8,100,103… Coarse filter, 9 ₁ , 9 ₂ … Ultraviolet irradiation section, 10 ₁ , 10 ₂ … Particle collection section, 11… Bioclean unit, 13… Work Table, 30, 31, 104… UV lamp, 40, 41, 105… Photoelectron emission material, 50, 51, 106… Photocatalytic material, 70, 71, 107… Electrode
80,81,108 …… Filter for collecting charged fine particles

Claims (7)

(57) [Claims] A photoelectron emitting material is irradiated with ultraviolet rays and / or radiation to emit photoelectrons, and the photoelectrons charge fine particles contained in a gas, and then remove the charged fine particles from the gas. A gas cleaning method comprising irradiating a photocatalyst and a photoelectron emitting material with ultraviolet light and / or radiation. 2. The gas cleaning method according to claim 1, wherein the photoelectron emission material also functions as a photocatalyst. 3. The gas cleaning method according to claim 1, wherein the photoelectron emission material and / or the photocatalyst material is formed in a net shape. 4. The method according to claim 1, wherein the photoelectron emitting material and / or the photocatalyst is irradiated with ultraviolet light and / or radiation in the presence of an electric field.
Or the cleaning method according to 3. 5. The electric field voltage is 0.1 to 10 KV, preferably
Claims 1 and 2, wherein it is 0.1 to 3 KV, more preferably 0.1 to 3 KV.
5. The gas cleaning method according to 3 or 4. 6. A gas purifying apparatus comprising a photoelectron emitting section, a photocatalyst section, an ultraviolet and / or radiation irradiating section for these, and a charged particle collecting section provided on a gas flow path from a gas inlet to a gas outlet. 7. The gas purifying apparatus according to claim 6, wherein an electric field generating means is provided in the photoelectron emitting section and the photocatalyst section.