Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
1999-09-20
2001-05-29
Gorgos, Kathryn (Department: 1741)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
Reexamination Certificate
active
06238631
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a three-dimensional, photocatalytic filter apparatus for removing organic or inorganic pollutants in a gas or liquid stream by using a semiconductor photocatalyst.
Ever increasing use of petrochemicals has caused serious environmental pollution problems. To solve the pollution problems, proposal has been made to purify a fluid by the photocatalytic oxidative decomposition of pollutants with a semiconductor photocatalyst. For example, an apparatus or instrument having a porous substrate supporting a semiconductor photocatalyst is placed in a flow path of a fluid containing pollutants to decompose the pollutants with the semiconductor photocatalyst.
In this method, to enhance the photocatalytic efficiency, it is needed to increase the photocatalytic surface area and to sufficiently activate the semiconductor photocatalyst with light having a wavelength capable of activating the photocatalyst. Several proposals have been made to increase a photocatalytic surface area to increase the opportunity of contact between pollutants and a semiconductor photocatalyst, and to form a photocatalyst layer with increased photocatalytic surface area. See Japanese Patent Laid-Open Nos. 5-309267, 8-196903, etc.
Well known in the art to increase the photocatalytic surface area is the formation of a photocatalyst layer on a porous substrate having a large surface area such as a layer of bonded fine particles, a nonwoven fabric, glass wool, a spongy substrate, etc. However, when a plurality of porous filter plates are arranged in a filter apparatus, a semiconductor photocatalyst deposited on all the porous substrates cannot be activated, because each porous substrate absorbs or cuts an activating light. If a layer of silica glass powder, soda glass powder or glass wool were used as the porous substrate, the activating light would reach comparatively deeper inside the porous substrate. However, such a porous substrate cannot be formed larger than about 30 mm in diameter due to its poor mechanical strength. Also, to achieve sufficient light-absorbing efficiency, the porous substrate should be as thin as about 2 mm or less. Therefore, this porous substrate is not promising in practical applications.
Some proposals also have been made to improve the shape and arrangement of a photocatalytic filter. For example, Japanese Patent Laid-Open No. 7-108138 discloses a photocatalytic filter apparatus comprising photocatalyst-supporting thin plates arranged in a blind form in a flow path of a fluid. Japanese Patent Laid-Open No. 8-121827 discloses a photocatalytic filter apparatus comprising a photocatalyst-supporting, corrugated nonwoven fabric on both sides of an ultraviolet lamp in a flow path of a fluid. Japanese Patent Laid-Open No. 9-187491 discloses a photocatalytic filter apparatus placed in a flow path of a fluid, the apparatus comprising a plurality of porous substrates each supporting a photocatalyst on both surfaces and radially fixed around a light source. Japanese Patent Laid-Open No. 9-248426 discloses a movable, photocatalytic filter apparatus comprising a photocatalyst layer formed on a convex member for conveying or stirring a fluid, and an ultraviolet source placed inside the convex member.
When a fluid containing pollutants is brought into contact with a semiconductor photocatalyst, active radicals generated by the semiconductor photocatalyst oxidatively decompose pollutants. If the total amount of pollutants exceeds a capacity of the conventional photocatalytic filter apparatuses, the pollutants would not fully come into contact with the photocatalyst, suffering disadvantages that it takes a lot of time to ensure contact of all the pollutants with the photocatalyst. It is difficult to increase a flow rate of the fluid in the conventional photocatalytic filter apparatuses, while enhancing decomposition efficiency. To enhance photocatalytic efficiency, it is necessary to use a suitable activating light that can sufficiently irradiate the semiconductor photocatalyst. Therefore, the development of a photocatalytic filter apparatus capable of efficiently irradiating the semiconductor photocatalyst has been desired.
In addition, intermediate products formed in the oxidative decomposition of nitrogen compounds, sulfur compounds, chlorine compounds, etc. tend to stick to a surface of the semiconductor photocatalyst, making it necessary to remove the intermediate products from the semiconductor photocatalyst at regular intervals. Accordingly, the photocatalytic filter apparatus is required to have a structure capable of being easily cleaned to prevent reducing a decomposition capacity thereof.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a three-dimensional, photocatalytic filter apparatus having an increased photocatalytic surface area for efficient decomposition of pollutants.
Another object of the present invention is to provide a three-dimensional, photocatalytic filter apparatus ensuring satisfactory irradiation of an activating light to a photocatalytic surface, as well as making good use of scattered light.
As a result of intense research in view of the above objects, the inventors have found the following facts:
(1) When a plurality of porous filter plates are three-dimensionally assembled such that each filter plate is inclined relative to a fluid stream, sufficient contact is achieved between the fluid stream and the semiconductor photocatalyst, thereby removing pollutants efficiently.
(2) When a plurality of porous filter plates are three-dimensionally assembled such that each filter plate is inclined relative to an activating light, sufficient irradiation of the activating light on the photocatalytic surface and enough utilization of scattered light are ensured.
Thus, the first three-dimensional, photocatalytic filter apparatus according to the present invention comprises a plurality of porous filter plates each carrying a photocatalyst for decomposing pollutants in a fluid stream which comes into contact with the porous filter plates, the porous filter plates being arranged in a path of the fluid stream such that each porous filter plate is inclined relative to both the fluid stream and a light source, to achieve sufficient contact with the pollutants and sufficient exposure to the light source.
The flow path means is preferably constituted by a pair of parallel, transparent sheets such as transparent glass or plastics, with the light source disposed outside at least one of the parallel, transparent sheets.
Each porous filter plate is preferably inclined by 15-75° relative to the fluid stream and by 15-75° relative to the light source.
The porous filter plates may intersect each other in a lattice pattern, such that all of the porous filter plates are inclined relative to both the fluid stream and the light source. The porous filter plates in one direction are inclined preferably by 15-75° relative to the light source, and the porous filter plates in the other direction are inclined preferably by 75-15° relative to the light source.
The second three-dimensional, photocatalytic filter apparatus according to the present invention comprises (a) a flow path means through which a fluid stream containing pollutants passes; (b) a plurality of porous filter plates each carrying a photocatalyst for decomposing the pollutants; (c) a light source; and (d) at least one support member for arranging each porous filter plate in a path of the fluid stream in the flow path means, at such a three-dimensional position that each porous filter plate is inclined relative to both the fluid stream and the light source, to achieve sufficient contact with said pollutants and sufficient exposure to the light source.
The flow path means is preferably a pipe having a longitudinal axis along which an elongated light source extends, and a plurality of the porous filter plates extend in the pipe spirally around the light source in parallel therewith, the porous filter plates being fixed to the support membe
Ogata Shiro
Sonomoto Kazuhiko
Gorgos Kathryn
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tao Inc.
Tran Thao
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