JPH059123B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method and an apparatus for removing charged particles from a gas stream containing them, and in particular to the electronic industry, the pharmaceutical industry, the food industry, the agriculture and forestry industry,
Removes charged particles from gas flows such as air, nitrogen, and oxygen in clean rooms, clean booths, clean tunnels, clean benches, safety cabinets, sterile rooms, bath boxes, sterile air curtains, clean tubes, etc. in the medical and precision machinery industries. TECHNICAL FIELD The present invention relates to a method and an apparatus for removing charged particulates from particulate-containing gases emitted from various industries such as flue gas and automobile exhaust gas. [Prior art and its problems] Conventional methods and devices for purifying indoor air can be roughly divided into: (1) Mechanical filtration methods (e.g. HEPA filters) (2) Electrostatic collection of particulates There are charging methods using high voltage and filtration methods using conductive filters (for example, MESA filters), but each of these methods 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, which reduces production efficiency. There was a drawback that it was bad. 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, the conventional filter method is only intended to remove particulates, so it can be used for industrial clean rooms, but filters almost always have pinholes, and some of the contaminated air can leak out. Therefore, there were limits to its use in biological clean rooms. In addition, methods that electrostatically collect particles require a high voltage of, for example, 15 to 70 kV 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 inventors
Earlier, we proposed a method for purifying the air by charging fine particles in gas by irradiating them with ultraviolet rays or radiation, and then collecting them (Japanese Patent Application 1983-
(No. 18723, Japanese Patent Application No. 61-85996), there were cases in which charged particles were not collected sufficiently. For example, when using a dust collection plate (dust collection electrode) as a method for collecting charged particulate matter, not only is the collection efficiency of ultrafine particles (for example, particles of 0.5〓m or less) insufficient, but also unsteady operation is required. Occasionally, the collected particles would scatter. [Object of the Invention] An object of the present invention is to provide a method and apparatus for efficiently collecting charged particles, especially charged fine particles, in a gas flow. [Structure of the Invention] The present invention allows a gas flow containing charged particles to be
The particles are precharged by passing them through an ion exchange filter in which an ion exchanger is supported by graft polymerization on a polymeric support, and further by irradiating the gas flow containing the particles with ultraviolet rays or radiation. A method for removing charged particulates from a gas flow by passing the charged particulates onto a filter to cause the filter to collect the charged particulates; Alternatively, it is a device for removing charged fine particles from a gas flow, which is sequentially provided with a precharging section consisting of a radiation irradiation section and an ion exchange filter in which an ion exchanger is supported by graft polymerization on a hollow polymer support. Next, an example in which an embodiment of the present invention is applied to a clean room, in which fine particles in the air are charged by irradiating ultraviolet rays and then collected by a filter, will be described with reference to FIG. In Fig. 1, numeral 1 is a clean room, 2 is an outside air intake pipe, 3 is a pre-filter, 4 is an air outlet from the clean room, 5 is a fan, 6 is an air conditioner, 7 is a HEPA filter, and 8 is a fan in the clean room. , 9 is an ultraviolet irradiation section, 10 is an ion exchange filter in which an ion exchanger is supported on a fibrous polymer support, 11 is a clean bench, 12 is a movable shutter, and 13 is a workbench. Inside the clean room 1, coarse particles from the outside air introduced from the pipe 2 are filtered by a pre-filter 3, and then sent to the air conditioner 6 through the fan 5 along with the air taken out from the air outlet 4 of the tureen room 1. After adjusting the temperature and humidity using the HEPA filter 7, the air is circulated to remove particulates and maintained at a cleanliness level (class) of about 10,000. On the other hand, the workbench 13 in the clean bench 11 equipped with the fan section 8, the ultraviolet ray irradiation section 9, and the ion exchange filter 10 in which an ion exchanger is supported on a fibrous polymer support in the clean room 1 is highly clean. Maintained in a sterile atmosphere at a temperature of 10 degrees (Class 10). That is, in the clean bench 11, air with a cleanliness level (class) of about 10,000 in the clean room 1 is sucked in by the fan in the fan unit 8, and fine particles in the air are charged by irradiating ultraviolet rays with the ultraviolet ray irradiation unit 9. At the same time, after microorganisms such as viruses, bacteria, enzymes, and molds are sterilized and charged, the charged particles are removed by the filter 10, thereby maintaining a high level of cleanliness on the workbench 13. Note that instruments, products, etc. can be taken in and out of the workbench 13 inside the clean bench 11.
This is done by a movable shutter 12 provided in the. FIG. 2 shows the ultraviolet ray irradiation section which is the preliminary charging section. In FIG. 2, numerals 8 and 10 have the same meanings as shown in FIG. prefilter,
24 indicates the flow of purified air. Prefilter 23 taken in by fan 8
The fine particles in the filtered air 20 are efficiently charged by photoelectrons emitted from the photoelectron emitting material 21 by ultraviolet rays irradiated from the ultraviolet lamp 22. Next, a fibrous ion exchange filter 10
The charged particles are efficiently collected and clean air 24 is obtained. The photoelectron emitting material 21 may be any material as long as it emits photoelectrons when irradiated with radiation or ultraviolet rays, and the smaller the photoelectric work function, the more preferable it is.
In terms of effectiveness and economy, 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,
Any one of Bi, Nb, Si, T ₁ , Ta, Sn, 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. Examples of compounds include oxides, borides, and carbides, and oxides include BaO, 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 , B ₁ O, NbO, BeO, etc., and borides include YB ₆ , GdB ₆ , LaB ₆ , CeB ₆ , PrB ₆ ,
ZrB ₂ , etc., and carbides such as ZrC,
Examples include TaC, T ₁ C, and NbC. In addition, alloys include brass, bronze, phosphor bronze,
Alloy of Ag and Mg (Mg 2-20wt%), Cu and Be
(Be is 1 to 10 wt%) and an alloy of Ba and Al can be used, and the alloy of Ag and Mg mentioned above,
An alloy of Cu and Be and an alloy of Ba and Al 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, a thin oxide film can be formed on the surface of an alloy of Mg and Ag in water vapor at a temperature of 300 to 400°C, and this thin oxide film is stable over a long period of time. . These materials can be used in any shape such as plate, pleat, or net, but it is preferable to use a shape that has a large area of ultraviolet irradiation and contact with air, and from this point of view, a net is preferable. is preferred. 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. The ion exchange filter 10 becomes clogged when used for a certain period of time, so by adopting a cartridge structure as necessary and replacing it by detecting pressure loss, stable operation can be achieved over a long period of time. As a method of charging fine particles in the air, we have described a method that does not create an electric field in the ultraviolet irradiation part, but it is also possible to charge ultraviolet rays (or radiation) on the photoelectron emitting material in an electric field with a relatively high voltage applied. Irradiation makes it possible to more efficiently emit photoelectrons and charge particles in the air. Next, the ion exchange filter will be explained in detail. The ion exchange filter may be of any type as long as it has the function of collecting charged particles from the gas flow. Those in which the body is supported by graft polymerization are used, and these can be appropriately manufactured by well-known methods. As the ion exchanger, an anion exchanger or a cation exchanger can be used. Supports include polymers of aliphatic unsaturated hydrocarbons such as polyethylene, polypropylene, polybutylene, and polybutene, polymers of aromatic hydrocarbons such as polystyrene and polymethylstyrene, and alicyclic polymers such as polyvinylcyclohexane. hydrocarbon polymers, or copolymers of these hydrocarbons, polytetrafluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymers,
Polymers of fluorine-containing unsaturated hydrocarbons, such as tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers, or copolymers thereof, etc. are used. It is also possible to use polyvinyl alcohol, polyamide, polyester, cellulose, wool, silk, or mixtures thereof. These supports are used as hollow supports, and may have any shape as long as they have a large contact area with the gas flow and low resistance, such as suitable thin film-like cloth, preferably net-like shapes, etc. An appropriate shape such as a woven or fibrous shape is used. Vacancy The vacancy rate of the support is 10-95%, preferably 50
~85%. Shape, thickness, and void of support
The rate can be appropriately determined depending on the shape of the device, the materials used, the structure, the expected effects, etc. The ion exchanger that can be used in the present invention is not particularly limited, and various cation exchangers or anion exchangers can be used. For example, exchangers containing cation exchange groups such as carboxyl groups, sulfonic acid groups, phosphoric acid groups, and phenolic hydroxyl groups; Examples include an exchanger containing an ion exchange group, or a polymerized or condensed type homogeneous or heterogeneous ion exchanger containing both the cationic and anionic ion exchangers. Typical examples include acrylic acid, methacrylic acid,
or styrene, halomethylstyrene, acyloxystyrene, hydroxystyrene, aminostyrene, styrene compounds such as vinylbenzenesulfonic acid, vinylpyridine, 2-methyl-5-vinylpyridine, 2-methyl-5-vinylimidazole,
Polymers of acrylonitrile or monomers having cationic or anionic exchange groups such as sulfuric acid, chlorosulfonic acid, sulfonic acid, or groups convertible thereto, or these monomers and divinylbenzene, trivinylbenzene, butadiene, ethylene glycol Copolymers with monomers having two or more double bonds such as divinyl ether, ethylene glycol dimethacrylate, etc., or polymers obtained by graft polymerizing styrene onto polyethylene, polyvinyl fluorocarbon ether, or polytetrafluoroethylene, etc., as required. An ion exchanger obtained by introducing a cationic and/or anionic ion exchange group or converting into an ion exchange group, a vinyl monomer such as tetrafluoroethylene, chlorotrifluoroethylene, and an ion exchange group or an ion exchange group. There are ion exchangers made of copolymers with perfluorovinyl monomers having groups that can be used. The method for supporting the ion exchanger on the support is not particularly limited, and can be carried out by any known method. For example, the support may be irradiated with ionizing radiation such as ultraviolet rays, rays, rays, electron beams, rays, or oxygen, ozone, chlorosulfonic acid, hydrogen peroxide, etc.
A method in which a monomer is grafted after treatment with an oxidizing agent such as benzoyl peroxide or peracetic acid, or two or more of these treatments to support an ion exchanger, and a support (e.g. polyethylene) is exposed to ionizing radiation. After irradiation, a method may be mentioned in which a graft polymer is obtained by reacting an aqueous solution of acrylic acid and/or methacrylic acid, and then treated with an aqueous sodium hydroxide solution. Another method is to make the support support the ion exchanger through a polymer layer (adhesive layer) that has a high affinity for the ion exchanger. In this method, first, a monomer for forming an adhesive layer with an ion exchanger is graft-polymerized onto a support. As the monomer for forming the adhesive layer, one whose polymer has a high affinity or adhesion to the ion exchanger is used. Examples of such monomers include olefin monomers such as propylene, halogenated vinyl monomers such as vinyl chloride, styrene derivatives, monomers having a nitrile group such as acrylonitrile, diene monomers such as butadiene, vinyl acetate, and ethyl acrylate. There are monomers with acid ester groups. These monomers are graft-polymerized onto the support by means such as irradiation with ionizing radiation and/or treatment with an oxidizing agent as described above. That is, after the support is pretreated by these means, it is impregnated with the monomer solution to be grafted and polymerized, or in the case of ultraviolet rays or radiation, the support is irradiated with the monomer solution impregnated. Also good. Next, the ion exchanger is supported on a support. This method varies depending on the type of ion exchanger, its manufacturing method, etc., but is carried out, for example, as follows. Either the raw material monomer mixture of the ion exchanger is impregnated into a support before poly(condensation) and the monomer mixture is poly(condensed) after impregnation, or the monomer mixture is partially poly(condensed) in advance.
The initial poly(condensation) polymer is impregnated into the support as it is, or if necessary, dissolved in a suitable solvent, and the poly(condensation) polymerization is completed after impregnation. The feature of this method is that since the support contains a graft polymer having a high affinity with the ion exchanger forming monomer, the adhesive layer of the support is formed by the monomer mixture or its initial poly(condensation) product. It swells or dissolves, and impregnation takes place satisfactorily. As a result, the subsequent polymerization of the monomer mixture or its initial poly(condensation) product provides a structure in which the polymer is closely integrated with the support via the graft polymerization layer. If the polymer impregnated into the support and polymerized does not have sufficient ion exchange groups, then cation or anion exchange groups are introduced by well-known means to obtain an ion exchange filter. In this way, an ion exchange filter is manufactured, and a fibrous or woven anion exchange filter and a cation exchange filter are obtained. The type, filling amount, and ratio of the anion exchange filter and cation exchange filter to be used can be appropriately determined depending on the charge state, concentration, etc. of the charged fine particles in the gas flow. For example, an anion exchange filter is effective for collecting negatively charged particles, and a cation exchange filter is effective for collecting positively charged particles. Further, the filling amount and its ratio may be appropriately determined in accordance with the concentration and concentration ratio of the charged fine particles, taking into consideration the shape, structure, pressure loss, etc. of the device. For example, the fine particles are negatively charged due to pre-charging, and since there are naturally positively charged fine particles in the air, the anion exchange filter is 80 (V/V%), while the cation exchange filter is 20 (V/V%). %) may be used. In the explanation regarding the drawings, a method was explained in which the ion exchange filter is used only in the filter 10 downstream of the precharging section, but the coarse filter 2 at the inlet of the precharging section is used.
Needless to say, it can be used for 3 as well. Example: Using a fibrous ion exchange filter manufactured by the following method and using the air purifier shown in FIG.
A test was conducted using the air purifier shown in the figure. However, ultraviolet light source: mercury-xenon lamp Photoelectron emission surface: brass Filling ratio: anion exchange filter 70%: cation exchange filter 30% (filter is fibrous) Generated fine particles are cigarette smoke (average particle size 0.3 to 0.4) 〓
m), the mixture was appropriately diluted with clean air and suctioned at 10/min, and the concentration was measured using a particle meter at the inlet (behind the coarse filter) and the outlet (behind the ion exchange filter). The results are shown in Table 1 below.

〔Effect of the invention〕

1. By using an ion exchange filter as a method for collecting charged particles, we were able to efficiently collect charged particles in a gas flow. There was no re-scattering of the collected particles, and a steady state of operation could be maintained for a long period of time. 2 By making the ion exchange filter into a woven or fibrous shape such as a net, practical anion exchange filters and cation exchange filters with low resistance were obtained. 3 By pre-charging with ultraviolet irradiation or radiation irradiation and collecting charged particles with an ion exchange filter in the wake, the particles in the gas stream are so high that their outflow to the wake can be virtually ignored. An ultra-clean gas stream was obtained with efficient collection. It can be applied to various fields and uses, and in particular, we were able to supply effective equipment for clean rooms, where conventional methods had limitations and were difficult, especially for bio-clean rooms. 4. Anion exchange filters and cation exchange filters can be used appropriately or in combination depending on the charge state of particles, etc., making it possible to provide optimal collection methods and devices depending on the purpose. 5 By using an ion exchange filter in the flow path without precharging (using it as a prefilter upstream of the precharging section), the load on the downstream precharging section is reduced and maintenance management becomes easier. , continuous operation was possible for a longer period of time. As a result of the above, the application fields and uses of the ultraviolet irradiation method and the radiation irradiation method have expanded.

[Brief explanation of the drawing]

FIG. 1 is a drawing for explaining an example in which the present invention is applied to a clean room, and FIG. 2 is a drawing for explaining a pre-charging section in more detail. 1... Clean room, 6... HEPA filter, 8... Fan section, 9... Ultraviolet irradiation section, 10
... Ion exchange filter, 11 ... Clean bench, 13 ... Workbench, 21 ... Photoelectron emission material, 2
2...Ultraviolet lamp.

Claims (1)

[Scope of Claims] 1. A gas flow containing charged fine particles, characterized in that the gas flow containing charged fine particles is passed through an ion exchange filter in which an ion exchanger is supported by a graft polymerization method on a hollow polymer support. A method for removing charged particles from. 2. The method of claim 1, wherein the particles in the gas stream are precharged and then passed through an ion exchange filter. 3. The method according to claim 2, wherein precharging is performed by irradiating ultraviolet rays or radiation. 4 Claim 3 in which precharging is performed using an electric field
The method described in section. 5. The method according to any one of claims 1 to 4, wherein the ion exchange filter is woven or fibrous. 6 A pre-charging section consisting of at least an ultraviolet ray irradiation section or a radiation irradiation section and an ion exchange filter are sequentially provided on the gas flow path from the gas flow inlet to the gas flow outlet containing charged particles. Device to remove. 7. The device according to claim 6, wherein an electric field is provided in the pre-charging section.