JPH0518529A - Purification system for exhaust gas - Google Patents

Abstract

PURPOSE:To purify exhaust gas containing contaminative constituents by a process having a long life span and good efficiency. CONSTITUTION:Absorbents 3 are placed in an exhaust gas duct 1, and oxidative catalysts 4 are located on both outsides thereof, and heaters 5 are, furthermore, located on both outsides of the oxidative catalysts 4. When exhaust gas is not flowing in the exhaust gas duct 1, an electric current is applied to the heaters 5, and the oxidative catalysts 4 are heated up to an active temperature thereof. In this way, contaminative constituents are separated from the absorbents 3 and are oxidized away with the oxidative catalysts 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention removes odorous components contained in exhaust gas and various gases contained in environmental pollutant components in household and industrial equipment, and uses the cream as an exhaust gas component. The present invention relates to an exhaust gas purification system.

[0002]

2. Description of the Related Art Conventionally, there are roughly two methods for removing pollutant components of exhaust gas. That is, an oxidation catalyst is installed in the middle of the exhaust gas passage to oxidize and decompose pollutants into carbon dioxide and water. An adsorbent such as activated carbon is installed in the exhaust gas passage to selectively adsorb pollutants and clean the exhaust gas.

However, in the former method, it is necessary to raise the oxidation catalyst to a predetermined temperature, and in the latter adsorbent, the adsorption amount is limited, so that it cannot be used for a long period of time.

[0004]

Therefore, a system combining these two methods (Japanese Patent Application No. 63-159981 and the like) is conceivable. However, the exhaust gas flow path must be frequently changed, and a heater, There is a drawback that the sequence of turning on and off the fan becomes complicated.

An object of the present invention is to provide an exhaust gas purification system which can easily treat pollutant components desorbed from an adsorbent without leaking to the outside.

[0006]

In order to solve the above-mentioned problems, the present invention installs an adsorbent in an exhaust gas flow path, and installs an oxidation catalyst at both ends of the adsorbent so as to sandwich the adsorbent,
Further, a heater for heating the oxidation catalyst is placed in the vicinity thereof.

[0007]

With the above structure, the pollutant component in the exhaust gas is captured by the adsorbent, and the heater for heating the oxidation catalyst works when the exhaust gas is not flowing, and the oxidation catalyst is heated. Even if the temperature of the adsorbent placed in the center is not as high as the temperature of the oxidation catalyst, the pollutant components are sufficiently desorbed and can be decomposed by the adjacent oxidation catalyst. At this time, it is not necessary to forcibly blow the air into the exhaust gas flow path, and depending on the configuration, supplementation of diffused air can sufficiently achieve the purpose. Since the oxidation catalysts are installed at both ends of the adsorbent, no matter which direction pollutants flow, it will not leak out of the system, and the configuration will be simple, and the operation sequence will also be improved. Very easy.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of the present invention.

In the exhaust gas purifying system of the present invention, the exhaust gas flows in the exhaust gas flow passage 1 from the lower side to the upper side in FIG. The adsorbent 3 made of hanikacam made of activated carbon wound in is installed. On both ends of the adsorbent 3, an oxidation catalyst 4 wound with a ceramic felt 2 is also installed with a slight space left between them. The oxidation catalyst 4 uses a cordierite honeycomb (400 cells / in ² ) as a carrier and has a γ-
This is a catalyst which is usually used, in which a washcoat mainly composed of Al ₂ O ₃ is applied and platinum (1 g / l) is supported on the washcoat. A sheath heater 5 is provided at both ends of the oxidation catalyst.
Is arranged so that the oxidation catalyst 4 can be heated.

Next, the operation of the exhaust gas purification system having the above structure will be described. The exhaust gas containing the pollutant flows from the lower part of the exhaust gas flow path 1 toward the upper part, and is trapped by the adsorbent 3 installed on the way. At this time, the heater 5 does not work, and the oxidation catalyst 4 does not work as a catalyst because it has not reached the predetermined activation temperature. Next, when the exhaust gas does not flow, the sheath heater 5 is energized to heat the adjacent oxidation catalyst 4, and the temperature reaches 300 to 400 ° C., depending on the type of the processing gas. Since the adsorbent 4 is installed at a position farther from the heater 5, the temperature is 100 to 200 ° C.,
The adsorbed pollutant begins to desorb. The desorbed pollutant component reaches the oxidation catalyst 4 by diffusion and is oxidized and removed by the diffusion air outside. In the example of FIG. 1, the exhaust gas flow path 1
Is a vertical type, and when the heater 5 is turned on, the pollutant components flow upward from the lower side due to the ascending air current and are processed by the upper oxidation catalyst, but even if the exhaust gas flow path is horizontal However, the pollutant is caught on either oxidation catalyst and will not leak out of the system without treatment.

Further, in the present embodiment, the fan is not forced to work when treating the pollutant, but a small amount of air may be sent. However, sending in too much air is not a good idea economically because the amount of heat taken out from the heater is also large, and depending on the adsorbed component and its amount, sufficient oxygen is supplied for the oxidation reaction. It is enough if possible.

FIG. 2 is a sectional view showing another embodiment. FIG. 2 is a model of the embodiment of FIG. 1 in which the size of the oxidation catalyst 4 is reduced. The adsorbent 3 plays a major role during normal operation of this system, and a large amount of adsorbent is required, but when desorbing pollutant components and treating them with the oxidation catalyst 4, a high concentration of pollutant components is required. Since it is discharged little by little over time, the size of the oxidation catalyst 4 may be small.
The structure and operation of FIG. 2 are similar to those of the embodiment of FIG.

In the above examples, activated carbon was used as the adsorbent. However, if the adsorbent has a property of adsorbing a component at a low temperature and desorbing it by raising the temperature, its physical condition is It can be used together.
Therefore, in addition to activated carbon, activated alumina, silica gel, and various zeolites can be used.

[0014]

As described above, the exhaust gas purification system of the present invention has the following effects. (1) Contaminant components can be efficiently removed even with low-temperature exhaust gas, and it is not necessary to raise the exhaust gas temperature to the catalyst activation temperature in the case of only the conventional oxidation catalyst, which is energy saving. (2) The system itself has a simple structure, and the adsorption of pollutant components and the regeneration may be the same. (3) The capacity of the oxidation catalyst may be small.

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust gas purification system showing an embodiment of the present invention.

FIG. 2 is a sectional view of an exhaust gas purification system showing another embodiment of the present invention.

[Explanation of symbols]

1 Exhaust gas flow path 3 Adsorbent 4 Oxidation catalyst 5 sheathed heater

Claims (2)

[Claims] 1. An exhaust gas purification system in which an adsorbent having adsorptivity is installed in an exhaust passage, an oxidation catalyst is installed at both ends of the adsorbent, and an electric heater is installed in the vicinity thereof. 2. The adsorbent comprises at least one selected from activated carbon, activated alumina, zeolite and silica gel,
The exhaust gas purification system according to claim 1, wherein the exhaust gas purification system is a regenerable adsorbent in which adsorbed components are desorbed by applying heat.