JP2004113961A - Gas component decomposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas component decomposition method which is simple and economical and excellent in gas component decomposition ability. <P>SOLUTION: The gas component decomposition method is for oxidizing and decomposing a gas component to be treated by introducing a gas containing the gas component to be treated into a reactor, heating the gas at 50-500°C, and bringing the gas into contact with a photocatalytic particle to which electromagnetic beam is radiated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a gas component decomposition method.
[0002]
[Prior art]
In factories, various factories, livestock and other waste treatment facilities, odorous gas is inevitably generated and must be released to the atmosphere. Of course, due to the problem of the surrounding environment, we try to pass through the deodorizing device and release it with no odor.
There is no problem if a very large and expensive deodorizing device is provided. However, it is a difficult problem for SMEs.
[0003]
Conventional deodorizing apparatuses are mainly of a combustion type, a cleaning type, an adsorption type and the like, but recently there are photocatalytic types and the like. The combustion type burns malodorous components to form oxides, and is performed at a high temperature using an oxidation catalyst. The cleaning type is one that is chemically neutralized or oxidatively decomposed.
[0004]
In the photocatalyst type, the photocatalyst is fixed to a wall tile, a paint, or a filter having a honeycomb structure, and is irradiated with ultraviolet rays to be decomposed by the oxidizing action of the photocatalyst.
[0005]
[Problems to be solved by the invention]
However, in the conventional deodorizing apparatus, none of them is completely perfect, and the odor may be released as it is.
In addition, even if it is odorless, there are many harmful substances, and it is needless to say that it is desirable to make such substances as harmless as possible.
[0006]
[Means for Solving the Problems]
In view of the above situation, the present inventor has completed the gas component decomposition method of the present invention as a result of diligent research, and the feature of the method is that the gas containing the gas component to be treated is supplied to the reactor. And heated to 50 ° C. to 500 ° C. in the reactor and brought into contact with the photocatalyst particles irradiated with the electromagnetic wave to cause oxidative decomposition.
[0007]
The gas component to be treated in the present invention is usually an odorous gas, but any gas that needs to be decomposed may have no odor. Usually, it is a compound of nitrogen and sulfur such as ammonia and mercaptan, and other odorless harmful substances.
[0008]
The gas containing such a gas component may be combustion waste gas, waste gas from a factory, exhaust gas from a poultry farm, a pig farm, or any other gas. Further, the gas may have been subjected to some kind of processing in advance.
[0009]
The reactor may be a simple container, as long as gas can be introduced and discharged. The reactor is provided with a heater. Any system such as an electric system, a gas system, and an oil system may be used. The gas is heated to 50 to 500 ° C. by this heater. Of course, the heater is initially heated at all, but if an exothermic reaction occurs inside the reactor, the energy is saved.
[0010]
The photocatalyst particles are put in this reactor. The particles may basically be fixed to something or introduced freely.
The photocatalyst is one that is excited by an electromagnetic wave (such as ultraviolet light or visible light) and functions as an oxidation catalyst or the like. At present, titanium oxide anatase crystals are well known. The size of the particles is not particularly limited, but is preferably several μm to several tens μm. However, if the reactor is freely charged, a larger one may be desirable with regard to entrainment problems.
[0011]
As a solution to the entrainment problem, a water spraying device may be provided near the discharge port (not necessarily in the vicinity) to prevent entrainment with water. It is the same as hitting a dusty place with water. Further, the water molecules are oxidized by a photocatalyst to form hydroxyl radicals and the like, which is effective for assisting the oxidation.
The quantity is preferably such that it is evaporated and discharged.
[0012]
Photocatalyst particles may be supported on small particles (ceramic, stone, metal, etc.) and may be filled free. The size of the particles is preferably such that they soar in the gas flow. If the degree of sowing is small, it may be soared by a stirrer.
[0013]
In the present invention, there is no need to separately supply oxygen as long as the gas containing the gas component to be treated contains oxygen necessary for oxidation. However, if there is little oxygen, such as combustion waste gas, air is introduced into the reactor. The opening may be simply provided and pulled by the suction force of the draft of the reactor, or may be pushed by a blower.
Oxygen instead of air, or water as described above (or the above) may be used. In short, any material that assists the oxidation reaction may be used.
[0014]
In the end, the method of the present invention involves contacting the gas component to be treated with a photocatalyst to oxidatively decompose it. is there. It is known that a photocatalyst is excited by irradiating an electromagnetic wave, but the present inventors have found that a catalytic effect can be significantly improved by heating the photocatalyst to normal temperature or higher.
[0015]
The electromagnetic wave applied in the present invention may be any electromagnetic wave, but is usually ultraviolet light. However, photocatalysts that excite even visible light have recently been called out. Of course, an electron beam having a shorter wavelength may be used. The cheapest is irradiation with an ultraviolet lamp.
[0016]
In the present invention, the heating temperature is 50 to 500C. This is because this effect is sufficient, and even if it is further increased, the photocatalytic effect does not change and the combustion simply occurs.
A major feature of the present invention is that the effect is exhibited at such a low temperature as compared with the combustion method. This makes it possible to reduce the generation of dioxins or to decompose gas components without generating them at all depending on the temperature. At present, it is said that the possibility of generating dioxin is high at 300 to 600 ° C, but if it is operated at 300 ° C or lower, the possibility of generating dioxin is extremely small.
[0017]
Even if the problem of dioxin is not considered, 200-300 ° C. was the most efficient from the viewpoint of the balance between the effect and the cost. However, even at about 50 ° C., the decomposition efficiency was clearly higher than that of the case without heating.
[0018]
If the temperature is taken into account as described above, the generation of dioxin can be almost eliminated regardless of what is contained, but not only that, when a gas containing dioxin is treated, the dioxin is removed. It is also expected to be oxidatively decomposed.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic sectional view showing one example of a reactor 1 for carrying out the method of the present invention. A two-layer filter 2 is provided inside. The filter 2 is a nonwoven fabric, and the photocatalyst particles are fixed to the fiber. The method of fixing may be bonding or simply physically stuck. A heater 3 is provided at the center of the filter 2. In this example, an electric heater is used, but another heater may be used. Here, the heater 3 heats up to 270 ° C.
An ultraviolet lamp 4 is provided on the ceiling and the bottom of the reactor 1. This is for irradiating the photocatalyst particles with ultraviolet rays and is not directly receiving the heat of the heater.
[0020]
The gas enters through the inlet 5, passes through the two-layer filter 2, and is discharged through the outlet 6. It is considered that the gas component is oxidatively decomposed when the gas component comes into contact with the photocatalyst particles in the filter 2 or by superoxide or hydroxyl radical generated by the photocatalyst.
[0021]
In this example, when air mixed with 50 ppm of methyl mercaptan was introduced, the discharge side was completely odorless. The flow rate was about 1 m / S at the center of the reactor.
Here, the same experiment was performed at room temperature with the heater turned off, but a slight odor remained.
[0022]
FIG. 2 is a schematic cross-sectional view showing one example of a reactor 1 for performing the method of the present invention as in FIG. In this example, the photocatalyst is fixed not to the filter but to the ceramic particles 7 (size: 2 to 10 mm). The ceramic particles are sandwiched and fixed by the net 8 from above and below. A heater similar to that of FIG. 1 is provided inside the ceramic particle layer. The driving method and effects are almost the same as those in FIG.
[0023]
FIG. 3 shows an example in which the photocatalyst particles 9 are freely filled, and are suspended in the reactor 1 by a gas flow. The ultraviolet lamp 4 is provided on the side wall. The heating device is a gas burner 10. In this example, large particles are used for the photocatalyst particles in order to reduce entrainment with gas as much as possible. For example, about 100 μm.
The filter 11 is provided in the reactor 1 in two stages. This is to reduce the momentum in the exit direction by causing particles to collide with the filter 11. Therefore, it is better to provide a coarse material in multiple stages, instead of a fine material such as fibrous clogging.
[0024]
Further, in order to prevent the discharge of the photocatalyst particles 9, a water spray nozzle 12 is provided near the discharge port 6.
Further, in this example, a cyclone type dust collector 13 is provided behind the discharge port 6 to prevent the photocatalyst particles from going out of the system. Of course, the photocatalyst particles recovered here can be reused in the reactor.
This example is more efficient than the examples shown in FIGS. Probably because of the large contact between the gas component and the photocatalyst particles.
[0025]
【The invention's effect】
The gas component decomposition method of the present invention has the following great advantages.
(1) Since the photocatalyst particles are heated, the photocatalytic effect is improved, and the decomposition efficiency of the gas component is improved. Almost all common odor components are decomposed.
(2) Since a simple device is sufficient, it can be easily adopted in any equipment that emits odor.
(3) If the photocatalyst particles are of a floating type, the gas component can be decomposed more effectively.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of a reactor for carrying out the method of the present invention.
FIG. 2 is a schematic sectional view showing another example of a reactor for carrying out the method of the present invention.
FIG. 3 is a schematic sectional view showing another example of a reactor for carrying out the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reactor 2 Filter 3 Heater 4 Ultraviolet lamp 5 Inlet 6 Outlet 7 Ceramic particle 8 Net 9 Photocatalytic particle 10 Burner 11 Filter 12 Water spray nozzle 13 Cyclone dust collector

Claims (4)

A gas containing a gas component to be treated is introduced into a reactor, heated to 50 ° C. to 500 ° C. in the reactor, and brought into contact with photocatalyst particles irradiated with electromagnetic waves to oxidize and decompose. Gas component decomposition method. The gas component decomposition method according to claim 1, wherein the photocatalyst particles are fixed to a filter. The gas component decomposition method according to claim 1, wherein the photocatalyst particles are freely movable in the reactor. 4. The gas component decomposition method according to claim 3, wherein water is sprayed on the photocatalyst particles in the reactor.

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