1. Field of the Invention
The invention relates to a device and a reactor including photocatalyst.
More particularly, this invention relates to the method in which the photocatalyst is activated by light rays with relatively short wavelength and a substance is subject to reaction of oxidation and/or reduction when the substance is in contact with or in close vicinity to the photocatalyst. Further, the invention relates to the device having photocatalyst layer including photocatalyst and further the invention relates to the reactor having photocatalyst layer including photocatalyst and a light source generating the light rays with relatively short wavelength.
2. Description of Related Art
It is well know that a photocatalyst activating by light rays with relatively short wavelength decomposes or dissolves an organic substance which is in contact with, in close vicinity to, or deposited on the photocatalyst by reaction of oxidation and/or reduction or photocatalyst effect.
Typical photocatalyst is a kind of photo activated semiconductor such as Titanium Dioxide (TiO2).
There are many fields of application of such photocatalyst, for instance, cleaning to delete dirty component from the surface of articles, dirt protection to prevent depositing of dirty component, prevention from spread of infection, deleting of odor, cleaning of air, processing of exhausting gas, cleaning of water, processing of exhausting water, dissolving of a water to make Hydrogen, speeding up of a chemical reaction and dissolving of pollutant which cause social pollution.
All the applications as mentioned above utilize the photocatalyst reaction of photocatalyst function by strong oxidation-reduction power to exert when the photocatalyst is activated by light.
For example, the photocatalyst being radiated by the light rays with short wavelength activates any Oxygen(O2) existing in the air, that dissolved or mixed in water, to form Ozone(O3) or activated Oxygen(O1). The Ozone or the activated Oxygen decomposes microorganisms such as fungi (i.e. molds) bacteria and organic chlorine compound containing in the water by oxidization. Therefore, the odor-less or color-less water is obtained and the water is sterilized.
Furthermore, the photocatalyst being radiated by the light rays having short wavelength shows a high activity of water's decomposition and helps to decompose the water(H2O) to activated oxygen(O) and hydrogen(H2).
Moreover, the photocatalyst as the material to eliminate or decrease environmental pollution. contributes to the decomposition of pollutants in which the pollutants contain a volatile organic solvent such as trichroloethylene, tetrachroloethylene, a chemical agent for agriculture such as grass eliminating agent bioinsecticide, an organic phosphate and a harmful inorganic chemical compound such as cyan and a kind of chrome.
Where multiple photocatalyst particles are used directly for reaction of oxidation-reduction with any substance, it is very difficult to separate and collect the photocatalyst particles and a device to utilize photocatalyst particles becomes complicated and large scale.
While, where multiple photocatalyst particles are used as a form of photocatalyst supported substrate in which a layer including the photocatalyst particles is fixed and supported on the substrate, recycling of the photocatalyst particles can be easily done because the separation and collection of the photocatalyst particles are not needed.
As for the latter case using the photocatalyst supported substrate, the publication of unexamined patent application of Japan No. 155726/1993 discloses that a Titanium Dioxide layer of photocatalyst is coated on a substrate such as metal, ceramic and glass, for the purpose of protecting a surface of the substrate from growth of bacteria.
Referring to FIG. 5 and FIG. 6, a typical prior art showing a device including photocatalyst(a substrate device supporting photocatalyst, a device with photocatalyst, or a photocatalyst device) is explained in which a layer including photocatalyst particles is fixed on a substrate.
FIG. 5 illustrates a schematic perspective view of a photocatalyst reactor showing the prior art of FIG. 6 illustrates a schematic enlarged cross-sectional view taken along the line B--B in FIG. 5, showing the photocatalyst device 300.
In FIG. 5 and FIG. 6, the photocatalyst device 300 consists of a plate like substrate 30 made from metal, ceramic or glass and a photocatalyst layer 20 made of binder layer including many photocatalyst particles in which the photocatalyst layer 20 is formed or fixed on the substrate 30.
As shown in FIG. 5, a conventional photocatalyst reactor consists of the photocatalyst device 300 having the substrate 30 and the photocatalyst layer 20 and a short wavelength light source 210(typically Ultraviolet light source) generating short wavelength light rays, such as Ultraviolet(UV) light rays. The light source 210 is preferably composed of a lamp having a linear shape (i.e. a tubular shape).
The short wavelength light source 210 is installed at a location, distant from the photocatalyst layer 20 of photocatalyst device 300, keeping a vertical distance "D".
As shown in FIGS. 5 and 6, the UV light rays L10 generating from the Ultraviolet light source 210 are directed toward a front surface of the substrate 30 and radiate directly a front surface of photocatalyst layer 20 coated on the front surface of the substrate 30.
Reference mark "OB" indicating as circle in FIG. 5 shows an object to be cleaned-up or purified, or a dirty component such as dirty substance by foods, molds, bacteria, dirty substance by oil, which is in contact with, inclose vicinity to, or deposited on the photocatalyst layer 20.
In an area which the dirty object "OB" exists, a large amount of the UV light rays L10 is absorbed (or reflected) at the dirty object "OB", on the way passing through the dirty object "OB". Therefore only a small amount of such light rays L10 reaches to the photocatalyst layer 20 in the area and the photocatalyst layer 20 in the area is activated or energizes in small rate by the UV light rays L10 with reduced lighting power.
Further, where the object "OB" composed of various media such as liquid(water, etc.) or gas(exhaust gas, etc.) are cleaned-up or process to react for clarification, the object "OB" exists between the UV light source 210 and the photocatalyst device 300. In this case, the object "OB" absorbs (or reflects) some amount of the UV light rays L10 radiated from the UV light source 210 and the photocatalyst layer 20 of the photocatalyst device 300 receives the remaining amount of UV light rays L10. Therefore, only the remaining amount of UV light rays L10 activates the photocatalyst layer 20.
As well known, water(generally liquid) can easily transmit visible light rays, while it absorbs short wavelength light rays L10 such as UV rays instead of transmitting.
Accordingly, in the prior art, an efficiency of short wavelength light rays L10 used for activation of photocatalyst is too low, because the object "OB" is existing between the short wavelength light source 210 and the photocatalyst layer 20 of the photocatalyst device 300.
Therefore, the prior art has such disadvantage that an effective use is not made for the short wavelength light rays L10 radiating(emitting) from the short wavelength light source 210 and a large volume of the short wavelength light source 210 with high power is required to accelerate a photocatalyst reaction in the photocatalyst reactor 300 and 210.