JP4272865B2 - Gas component decomposition method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a gas component decomposition method.
[0002]
[Prior art]
Odor gas is inevitably generated in factories, various manufacturing facilities, livestock industry, and other waste disposal facilities, which must be released to the atmosphere. Of course, we try to pass through the deodorizing device due to the surrounding environment and release it without odor. However, the simple deodorizing device is not perfect, and there are some conflicts with local residents.
There is no problem if a very large and expensive deodorizing device is provided. However, this is a difficult problem for SMEs.
[0003]
Conventional deodorizing apparatuses are mainly a combustion type, a cleaning type, an adsorption type, and the like, but recently, there are a photocatalyst type and the like. The combustion type burns malodorous components into oxides and is performed using an oxidation catalyst at a high temperature. The cleaning type is chemically neutralized or oxidatively decomposed.
[0004]
In the photocatalyst type, the photocatalyst is fixed to a wall tile or 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, none of the conventional deodorizing apparatuses are completely complete, and the odor may be released as it is.
Moreover, even if it is odorless, there are many harmful substances, and it goes without saying 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 intensive studies, and the feature thereof is that a gas containing a gas component to be treated is introduced into a reactor. And is brought into contact with photocatalyst particles heated to 50 ° C. to 500 ° C. and irradiated with electromagnetic waves in the reactor to be oxidatively decomposed.
[0007]
The gas component to be treated in the present invention is usually a malodorous gas, but it does not have to be malodorous if it is a gas that requires decomposition. Usually, it is a nitrogen or sulfur compound such as ammonia or mercaptan, and other odorless harmful substances.
[0008]
The gas containing such a gas component may be any combustion gas, waste gas from a factory, exhaust from a poultry farm or pig farm, or any other gas. Further, the gas may be processed in advance.
[0009]
The reactor may be a simple container as long as gas can be introduced and discharged. This 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, all are initially heated by this heater, but if an exothermic reaction occurs inside the reactor, that amount will be energetically saved.
[0010]
Photocatalyst particles are placed in the reactor. Basically, these particles may be fixed to something or introduced free.
A photocatalyst refers to one that is excited by electromagnetic waves (ultraviolet rays, visible light, etc.) and functions as an oxidation catalyst or the like. At present, anatase-type crystals of titanium oxide are well known. The size of the particles is not particularly limited, but is preferably several μ to several tens μ. However, when the reactor is filled free, a larger one may be desirable with respect to entrainment problems.
[0011]
Further, as a solution to the problem of entrainment, a water spray device may be provided near the discharge port (not necessarily near) to prevent entrainment by water. It is the same as hitting water in a dusty place. In addition, this water molecule is oxidized by a photocatalyst to become a hydroxyl radical or the like, which is effective for assisting the oxidation.
In terms of quantity, it should be evaporated to be discharged.
[0012]
Photocatalyst particles may be supported on small particles (ceramic, stone, metal, etc.) and filled free of charge. The size of the particles should be such that it soars with the flow of gas. Further, if the degree of soaring is small, it may be soared with a stirring device.
[0013]
In the present invention, it is not necessary to supply oxygen separately if the gas containing the gas component to be treated contains oxygen as much as necessary for oxidation. However, if there is little oxygen like combustion waste gas, air is introduced into the reactor. It may be simply provided with an opening and pulled by the suction force of the reactor draft, or may be pushed in with a blower.
It may be oxygen, not air, or water as described above (or the above). In short, it may be anything that helps the oxidation reaction.
[0014]
After all, in the method of the present invention, the gas component to be treated is brought into contact with the photocatalyst to undergo oxidative decomposition, but it is natural that the photocatalyst is irradiated with electromagnetic waves, but in the present invention, it is also heated. is there. The photocatalyst is known to be excited when irradiated with electromagnetic waves, but the present inventors have found that the catalytic effect is remarkably improved when it is heated to room temperature or higher.
[0015]
The electromagnetic wave irradiated in the present invention may be anything as long as it is an electromagnetic wave, but is usually ultraviolet light. However, photocatalysts that excite even visible light have recently been shouted. Of course, it may be an electron beam having a shorter wavelength. The cheapest is irradiation with an ultraviolet lamp.
[0016]
In the present invention, the heating temperature is 50 to 500 ° C. This is because there is a sufficient effect at this level, and the photocatalytic effect does not change even if it is further increased, and it is merely combustion.
A significant feature of the present invention is that it is effective at such a low temperature as compared with the combustion method. As a result, the generation of dioxins can be reduced or the gas component can be decomposed without being generated at all depending on the temperature. At present, it is said that the possibility of dioxin generation is high at 300 to 600 ° C., but if it is operated at 300 ° C. or lower, the possibility of dioxin generation is extremely small.
[0017]
Even if the problem of dioxins is not taken into consideration, 200 to 300 ° C. is the most efficient from the viewpoint of the balance between the effect and the cost. However, even at about 50 ° C., the decomposition efficiency clearly increased as compared with the case of not heating.
[0018]
If the temperature is taken into consideration as described above, the generation of dioxins can be almost eliminated regardless of what is contained, but not only that, but when the gas containing dioxins is treated, the dioxins are reduced. Oxidative decomposition is also expected.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic sectional view showing an example of a reactor 1 for carrying out the method of the present invention. Two layers of filters 2 are provided inside. The filter 2 is a non-woven fabric, and photocatalyst particles are fixed to the fiber. The fixing method may be adhesion or simply physical hooking. A heater 3 is provided at the center of the filter 2. In this example, although it is an electric heater, other heating tools may be used. Here, the heater 3 is heated to 270 ° C.
An ultraviolet lamp 4 is provided on the ceiling and bottom of the reactor 1. This is for irradiating the photocatalyst particles with ultraviolet rays, and prevents the heater from receiving heat directly.
[0020]
The gas enters from the introduction port 5, passes through the two-layer filter 2, and is discharged from the discharge port 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, hydroxy radical, or the like generated by the photocatalyst.
[0021]
In this example, when air mixed with 50 ppm of methyl mercaptan was introduced, it was completely odorless on the discharge side. The flow rate was about 1 m / S in the middle of the reactor.
Here, the same experiment was tried at room temperature with the heater turned off, but a slight odor remained.
[0022]
FIG. 2 is a schematic cross-sectional view showing an example of a reactor 1 for carrying out the method of the present invention as in FIG. In this example, the photocatalyst is fixed to the ceramic particles 7 (size, 2 to 10 mm) instead of the filter. These ceramic particles are sandwiched and fixed by a net 8 from above and below. A heater similar to that shown in FIG. 1 is provided inside the ceramic particle layer. The operation method and effects are almost the same as in FIG.
[0023]
FIG. 3 shows an example in which the photocatalyst particles 9 are filled freely, and the photocatalyst particles 9 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, the photocatalyst particles use large particles to reduce entrainment with gas as much as possible. For example, it is about 100 μm.
A filter 11 is provided in the reactor 1 in two stages. This is because the particles collide with the filter 11 to reduce the momentum in the exit direction. Therefore, it is better to provide coarse things in multiple stages rather than fine things that clog the fibers.
[0024]
Further, a water spray nozzle 12 is provided in the vicinity of the discharge port 6 in order to prevent the discharge of the photocatalyst particles 9.
Further, in this example, a cyclone type dust collector 13 is provided behind the discharge port 6 to prevent the photocatalyst particles from coming 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 of FIGS. Probably because there are many contacts 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 malodorous components are decomposed.
(2) Since a simple device may be used, it can be easily adopted in any facility 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 Photocatalyst particle 10 Burner 11 Filter 12 Water spray nozzle 13 Cyclone type dust collector

Claims (1)

A method of introducing a gas containing a gas component to be treated into a reactor, bringing the gas component into contact with a photocatalyst heated to 50 ° C. to 500 ° C. and irradiated with electromagnetic waves, and oxidatively decomposing the gas. The photocatalyst particles are carried on small particles of ceramic, stone or metal, the loaded ones are filled free into the reactor, and near the outlet of the reactor to prevent the discharge of the free particles A gas component decomposition method characterized by spraying water on the surface .

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