Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1986-11-21
1988-06-14
Hart, Charles
Gas separation
Means within gas stream for conducting concentrate to collector
55102, 55279, 422 24, B01D 5300
Patent
active
047509171
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of and an apparatus for cleaning the air in clean rooms, clean booths, clean tunnels, clean benches, safety cabinets, aseptic rooms, bath boxes, aseptic air curtains, or clean tubes in the electronics industry, medicines industry, food industry, agricultural and forestry industries, medical facilities and precision machine industries.
Conventional air cleaning methods or apparatus in a room are generally classified into the following: voltage and collecting the particles electrostatically by means of a conductive filter (e.g., a MESA filter).
These types have the following drawbacks:
In the mechanical filter type, it is necessary to use a fine filter to improve the quality (the cleaning class) of the air. In this case, the pressure loss is high, the increase in pressure loss due to clogging is remarkable, the lifetime of the filter is short, and the maintenance, the management and the exchange of the filter are complicated. When the filter is exchanged, it is necessary to stop working during the exchange, and it takes a long time to recover the system which deteriorates the production efficiency.
The number of times for ventilations (the number of times for circulating the air by a fan) is increased to improve the quality, i.e., to raise the cleaning class of the air, but the cost of power increases.
Since the only purpose of the conventional filter method is to remove fine particles, it can be used as an industrial clean room, but as the filter always has pin-holes which leak part of the contaminated air, its use in a biological clean room is limited.
In the type for electrostatically collecting fine particles, a high voltage such as 15 to 70 kV is necessary in a preliminary charger to cause the system to increase in size, and there are safety, maintenance and management drawbacks.
In order to solve the above mentioned drawbacks, the inventor of the present invention has proposed an air cleaning system by irradiation of ultraviolet rays (Japanese Patent Application No. 216293/1984). Such a system is effective for a certain application field and utility, but is insufficient if applied to the purification of air containing ultrafine particles and any special field.
SUMMARY OF THE INVENTION
The present invention is a method of cleaning the air by irradiating the air with ultraviolet rays so as to electrically charge the fine particles therein and thereafter remove the charged fine particles from the air, comprising the steps of irradiating a photo-electron discharge member with ultraviolet rays, electrically charging the fine particles by using the photo-electrons generated due to this irradiation, and removing the fine particles charged by the photo-electrons from the air.
Further, in order to execute the above mentioned method, the present invention discloses an apparatus for cleaning the air comprising an ultraviolet ray irradiation portion, photo-electron discharge portions and a charged fine particle-collecting portion on an air flow passage from an air intake port to an air exhaust port.
As a preferred embodiment, there are provided a method of and an apparatus for charging fine particles in the air by photo-electrons generated due to the irradiation of ultraviolet rays to the photo-electron discharge members in an electric field.
As the photo-electron discharge members, there is preferably selected a substance having small photoelectric work function, a compound or alloy thereof to be used solely or as a composite material with two or more types.
Advantages of the invention include the following: members in an electric field applied with a relatively high voltage by the irradiation of the ultraviolet rays to the photo-electron discharge portions: as compared with the conventional electrostatic filter type; i.e., air of high cleaning class can be provided merely by disposing a collector of suitable charged particles such as an electrostatic filter at the trailing stream side; superclean room can be obtained; and particle collecting type
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patent: 4477263 (1984-10-01), Shaun et al.
patent: 4553992 (1985-11-01), Boissinot et al.
patent: 4574004 (1986-03-01), Schmidt-Ott et al.
Tohoku University Fundamental Electronics Introductory Course, vol. 13, "Photoelectric Device", Author Masanopu Wada, Published Dec. 15, 1959.
Ebara Research Co. Ltd.
Hart Charles
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