JPH0617638A - Exhaust gas purifying device - Google Patents

Abstract

PURPOSE:To improve durability and oxidizing resistance, and burn and eliminate particulates rapidly. CONSTITUTION:A porous body 12 made of silicon carbide is provided on the way of an exhaust gas flow passage in such constitution as crossing the inside of the flow passage 10. A micro wave radiation port 14 is opened on the pipe wall part of the flow passage 10, and a magnetron 18 is arranged on the outside of the micro wave radiation port 14 through a wave leading pipe 16. It is thus possible to heat the porous body 12 made of silicon carbide rapidly so as to burn and eliminate particulates rapidly. And also it is excellent in oxidizing resistance property and durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for purifying combustion / exhaust gas from a diesel engine or the like.

[0002]

2. Description of the Related Art Currently, a collection system of particulates in combustion exhaust gas of a diesel engine uses a porous ceramic (for example, cordierite) as a collection material.
Combustion exhaust gas is brought into contact with this porous ceramic to trap particulates. The particulates trapped in the particulates are burned on the spot by an electric heater or a gas burner, or the trapped particulates are separated from the trapping material by vibration or backwashing with gas, etc. Dust is collected and burned off by electric heaters and gas burners.

[0003]

Since cordierite has a small expansion coefficient and is resistant to thermal shock, it has been conventionally used as a catalyst carrier for treating exhaust gas of automobiles, but it is not so excellent in strength and heat resistance. Therefore, when used for a particulate trap system and attempting to burn particulates trapped in cordierite on the spot, cracks are generated and cracked at a burning temperature of 1000 ° C. or higher. Further, if the temperature becomes higher (about 1400 ° C.) due to abnormal combustion or the like, it may melt, so it is necessary to burn particulates under strict temperature control.

In the method of removing particulates from cordierite traps and burning them, it is difficult to completely remove particulates from cordierite, and traps tend to be clogged, or the structure becomes large and large. There are problems such as.

In any of the above methods, there is a problem in the durability of the heater material and the electrodes in the heating and burning by the electric heater.

The present invention solves the problems of the particulate trap system in which the porous cordierite described above is used as a particulate trap in the exhaust gas of a diesel engine or the like and the trapped particulates are burned and removed. An object of the present invention is to provide an exhaust gas purifying apparatus for removing particulates, which can easily remove particulates by heating and burning.

[0007]

An exhaust gas purifying apparatus according to a first aspect of the present invention comprises an exhaust gas passage and a particulate collecting porous body provided in the passage so as to come into contact with the exhaust gas. In an exhaust gas purifying apparatus, a magnetron for arranging a silicon carbide-based porous body as the porous body and irradiating the silicon carbide-based porous body with a microwave to inductively heat the porous body to burn and remove particulates. Is provided.

An exhaust gas purifying apparatus according to a second aspect is the exhaust gas purifying apparatus according to the first aspect, wherein the surface of the porous body is provided with irregularities.

An exhaust gas purifying apparatus according to a third aspect is the exhaust gas purifying apparatus according to the first aspect, wherein the porous body is a mat of silicon carbide fibers.

An exhaust gas purifying apparatus according to a fourth aspect is the exhaust gas purifying apparatus according to the first aspect, wherein the porous body is a ceramic fiber mat impregnated with silicon carbide.

[0011]

Function Silicon carbide (SiC) has a larger coefficient of thermal expansion than cordierite, but has a high strength and extremely high heat resistance. Silicon carbide is a microwave absorbing material and is capable of dielectric heating by irradiation with microwaves.

By using such a silicon carbide porous body as a particulate trap, it is possible to provide a system having high heat resistance and easy heating for burning and removing the trapped particulates.

In order to facilitate dielectric heating of the silicon carbide porous body, it is preferable to provide irregularities on the surface of the silicon carbide porous body so that local heating occurs.

Such a silicon carbide porous body can be manufactured by a normal sintering method or a reaction sintering method, but the inner and outer surfaces of the microwave permeable porous body are coated with silicon carbide by CVD or carbon. It is preferable that the inner and outer surfaces of the porous base material such as the above are coated with SiC by CVD and then the base material is removed.

In order to facilitate dielectric heating of the silicon carbide porous body, it is also preferable to use the silicon carbide porous body as a fiber mat. It is considered that this is because the microwave is rapidly heated by being concentrated at the tip of the fiber.
The fiber mat may be a mat formed by accumulating silicon carbide fibers, or may be a ceramic fiber mat impregnated with silicon carbide by CVD. Further, it may be manufactured by impregnating a mat of ceramic fibers with carbosilane or the like which is thermally decomposed to become SiC and then heat-treating the mat.

[0016]

EXAMPLES Examples will be described below with reference to the drawings. In the first embodiment shown in FIG. 1, the exhaust gas passage 10
In the middle of, a silicon carbide based porous body 12 is provided so as to cross the inside of the flow path. A microwave irradiation port 14 is opened in the pipe wall portion of this flow path, and a magnetron 18 is arranged outside the microwave irradiation port 14 via a waveguide 16.

In this exhaust gas purifying apparatus, the magnetron 18 is operated to generate microwaves into the silicon carbide based porous material 1
When 2 is irradiated, the porous body 12 is rapidly heated and the particulates are burned and removed.

Next, specific examples will be described.

Example 1 Porosity 90%, Pore diameter 40P
As shown in FIG. 1, a urethane foam type smashed SiC porous body of PI was installed in an engine exhaust gas pipe to form a particulate trap. Then, a microwave of 2.45 GHz _Z output 500W from the side portion of the SiC porous body S
When the iC porous body was irradiated, it was irradiated with SiC for 50 seconds.
The porous body generated heat at 700 ° C., and the particulates trapped in the porous body were quickly burned and removed.

(Embodiment 2) In FIG. 1, a porosity of 87
%, A urethane foam type crushed silicon carbide porous body having a pore diameter of 60 PPI and a silicon carbide porous body having irregularities on the surface was used as a trap. FIG. 2 is a schematic cross-sectional view of this silicon carbide, and the pitch a of the irregularities on the surface of the porous body 12A is about 3 to.
It is about 20 mm. Output of 500W to this trap 2.
When irradiated with a microwave of 45 GHz, the projections on the surface generated heat at 800 ° C. by irradiation for 20 seconds, and the particulates trapped in the silicon carbide porous body were quickly burned and removed.

Example 3 A silicon carbide-impregnated silicon carbide fiber mat having a porosity of 90% and a fiber density of 0.06 g / cc was used as a trap. When this trap was irradiated with a microwave of 2.45 GHz with an output of 500 W, the temperature partially reached 700 ° C. in 20 seconds, and the trapped particulates were quickly burned and removed.

[0022]

As described above, according to the first to fourth aspects of the present invention, it is possible to rapidly burn and remove particulates by rapid heating, and to purify exhaust gas excellent in oxidation resistance and durability. A device is provided. Note that claims 2 to 4
In, the silicon carbide based porous material can be heated extremely rapidly.

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust gas purifying apparatus according to an embodiment.

FIG. 2 is a schematic cross-sectional view of the surface of a silicon carbide porous body.

[Explanation of symbols]

 10 Channel 12 Silicon Carbide Porous Material 14 Microwave Irradiation Port 16 Waveguide 18 Magnetron

Claims (4)

[Claims] 1. An exhaust gas purifying apparatus comprising an exhaust gas flow passage and a porous body for collecting particulates provided in the flow passage so as to come into contact with the exhaust gas, wherein the porous body is made of silicon carbide. While installing the porous body,
An exhaust gas purifying apparatus comprising a magnetron for irradiating the porous body made of silicon carbide with microwaves to inductively heat the porous body to burn and remove particulates. 2. The exhaust gas purifying apparatus according to claim 1, wherein the surface of the porous body is provided with irregularities. 3. The exhaust gas purifying apparatus according to claim 1, wherein the porous body is a mat of silicon carbide fibers. 4. The exhaust gas purifying apparatus according to claim 1, wherein the porous body is a ceramic fiber mat impregnated with silicon carbide.