JPH0459027A - Exhaust gas cleaning device by high frequency heating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an exhaust gas purification device that completely burns unburned hydrocarbons and carbon oxides discharged from cooking appliances such as microwave ovens and decomposes them into carbon dioxide gas and water. This invention relates to an exhaust gas purification device that completely burns unburned hydrocarbons, carbon oxides, and nitrogen oxides discharged from automobile engines and decomposes them into carbon dioxide, nitrogen, and water.

Conventional technology Conventionally, this type of exhaust gas purification device coats the surface of a high-density ceramic honeycomb structure such as cordierite with fine particles such as alumina to increase the surface area, and coats the surface with fine particles such as alumina, etc. An exhaust gas purification catalyst supporting noble metal catalysts, recently perovskite-type composite oxides, etc., is heated to a high temperature using exhaust heat generated from a cooking chamber, exhaust heat generated from an automobile engine, or heated by heating means such as an electric heater. was used to raise the temperature to completely burn the unburned gas, such as hydrocarbons, carbon oxides, and nitrogen oxides, and decompose them into carbon gas, nitrogen, and water.

Problems to be Solved by the Invention However, when the exhaust gas purification catalyst body as described above is heated to a high temperature by exhaust heat generated from the heating chamber of a cooker or exhaust heat generated from an automobile engine, the exhaust gas purification catalyst body becomes active. Unburned gas is generated and passes through until the temperature reaches the temperature indicated. For this reason, unburned gas cannot be completely combusted at the initial stage of use. Even when a heating means such as an electric heater is used, the exhaust gas purification catalyst body is heated from the outer periphery, so it is impossible to quickly raise the temperature, and there are problems similar to those using exhaust heat.

Means for Solving the Problems In order to solve the above-mentioned problems, the high-frequency heating exhaust gas purification device of the present invention uses a high-frequency radio wave power absorbing material as a catalyst carrier, and supports a purification catalyst on the surface of the material to form an exhaust gas purification catalyst body. When high-frequency radio waves are supplied to the exhaust gas purification catalyst body, the catalyst carrier itself generates heat, and the temperature quickly rises.

In high-frequency heating using active high-frequency radio waves, the object to be heated absorbs the high-frequency radio power and generates heat itself by dielectric heating or electric resistance heating. In this case, unless the material of the object to be heated has a large dielectric constant and dielectric loss, it will not absorb high frequency radio wave power efficiently and will not generate heat rapidly. The catalyst supports used in conventional exhaust gas purification catalysts are generally cordierite or mullite, but these materials have small relative permittivity and dielectric loss angle values, making them unsuitable for high-frequency heating. A high-frequency radio wave power absorbing material with large values of dielectric constant and dielectric loss angle is used as a catalyst support, and a catalyst is supported on the surface to form an exhaust gas purification catalyst. When power is supplied, the catalyst carrier self-heats, and since the heat is generated internally, there is almost no excess heat escaping to the outside, and the temperature of the exhaust gas purification catalyst increases rapidly. The high-frequency heating exhaust gas purification device of the present invention, which is placed in an exhaust gas stream containing unburned gas, is rapidly heated to a temperature where it functions as a catalyst by being supplied with high-frequency radio waves, and the unburned gas passes through without being decomposed. Prevent things from happening.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. In the figure, 1 is a heating chamber to which high-frequency radio waves are supplied to heat the object to be heated, 2 is a magnetron that is a high-frequency radio oscillation source that supplies high-frequency radio waves to the heating chamber 1, and 3 is a high-frequency radio wave oscillated by the magnetron 2 to the heating chamber 1. waveguide leading to 4
5 is the opening of the waveguide 3 and the high frequency radio wave feeding port to the heating chamber 1;
Reference numeral 6 indicates an intake wall that constitutes the heating chamber 1 and is located on the exhaust gas inlet side, and 6 is an exhaust wall that is also located on the outlet side. The heating chamber 1 acts as a resonance box for high-frequency radio waves, and is made of a heat-resistant metal plate such as stainless steel so as to confine and prevent high-frequency radio waves from leaking. The intake wall 5 and the exhaust wall 6, which constitute a part of the heating chamber 1, are also made of a metal material that does not leak high-frequency radio waves, and are made of a metal transparent material such as a wire mesh or punched metal so that the exhaust gas can flow. 7 is an exhaust gas inlet, and 8 is an exhaust port. Reference numeral 9 denotes a first exhaust gas purification catalyst body, which is provided in the heating chamber 1 on the exhaust wall 6 side. The first exhaust gas purification catalyst body 9 uses a high-density ceramic honeycomb structure of cordierite or mullite as a catalyst carrier, and coats the surface with fine particles such as alumina, and then coats the surface with a noble metal catalyst such as platinum, rhodium, palladium, etc. Or a perovskite type composite oxide catalyst is supported. 10
is a second exhaust gas purification catalyst body, which is provided in the heating chamber 1 on the intake wall 5 side. The second exhaust gas purification catalyst body 10 uses a ceramic honeycomb structure made of a high-frequency radio wave power absorbing material in which halium titanate BaTiO3 is kneaded with cordierite or Murai I- as a catalyst-carrying material in the first embodiment. The above-mentioned noble metal catalyst or Belodisky 1-type composite oxide catalyst is supported on the catalyst. Halium titanate BaTiO3 has large values of relative dielectric constant and dielectric loss angle,
When fed with high-frequency radio waves, it absorbs high-frequency radio power well and rapidly generates heat.

As a second embodiment, the second exhaust gas purification catalyst body 10 uses a ceramic honeycomb structure of silicon carbide (I-SiC) as a catalyst support, and supports a purification catalyst on the surface as in the case of NIL. Silicon carbide SiC exhibits high insulating properties as a pure single crystal, but when it is made into a ceramic structure made by baking fine particles, many defects are generated, and these defects are used to supply electrons. Represents conductivity. When high-frequency radio waves are supplied, heat is generated due to electrical resistance heating due to this conductivity, and as a result, high-frequency radio wave power is well absorbed.

Unlike a simple electrical resistor, it is a ceramic structure with appropriate conductivity, so high-frequency radio waves penetrate into the inside of the catalyst carrier, causing rapid internal heat generation.

The silicon carbide SiC ceramic structure has a large surface area and is suitable for supporting a purification catalyst.

In this way, the catalyst carrier is placed in the second heating chamber 1 made of a heat-resistant metal plate made of a high-frequency radio wave power absorbing material.
An exhaust gas purification catalyst body 10 is provided, and the intake wall 5 and the exhaust wall 6 of the heating chamber 1 are connected so that the high frequency radio waves oscillated from the magnetron 2 are supplied to the heating chamber 1 and the exhaust gas flows through the second exhaust gas purification catalyst body 10. The high-frequency heating exhaust gas purification device of the present invention is constructed of a metal transparent body such as a wire mesh.

In the high-frequency heating exhaust gas purification device of the present invention having such a configuration, when the magnetron 2 is oscillated and high-frequency radio waves are supplied to the heating chamber 1 immediately before the exhaust gas containing unburned gas flows or immediately after the flow starts, the second exhaust gas purification is performed. The catalyst carrier of the catalyst body 10 self-generates heat by dielectric heating or electric resistance heating, and since the heating is internal, the second exhaust gas purification catalyst body 10 rapidly generates heat to a temperature at which it functions as a catalyst, decomposing unburned gas. do. The passage of unburned gas can be prevented or the amount of unburned gas passing can be reduced.

The heating chamber 1 acts as a resonant box for high-frequency radio waves, and standing waves are generated inside. The point where the electric field is strong is located at a distance from the wall of the heating chamber 1 by a length of more than one quarter of the wavelength determined by the frequency of the high-frequency radio wave being used. It is more effective to arrange the second exhaust gas purification catalyst body 10 having the high frequency radio wave power absorbing material at a point where the electric field is strong. For this reason, a gap ρ of 1/4 wavelength or more is provided between the second exhaust gas purification catalyst body 10 and the intake wall 5 which is the inlet side metal transparent body.

A high frequency radio wave is supplied to the second exhaust gas purification catalyst body 10,
In order to quickly generate heat and raise the temperature to a functional level in a short time, it is necessary to reduce the heat capacity, and the size and weight of the second exhaust gas purification catalyst body 10 cannot be increased much. On the other hand, when exhaust gas containing a large amount of unburned gas begins to flow, a large surface area of the purification catalyst is desired. For this reason, it is divided into a first exhaust gas purification catalyst body 9 and a second exhaust gas purification catalyst body 10, so that the high frequency radio wave power is mainly absorbed by the second exhaust gas purification catalyst body 10. The second exhaust gas purification catalyst body 10 is provided on the exhaust gas inlet side of the heating chamber 1, on the intake wall 5 side, and the first exhaust gas purification catalyst body 9 is provided on the outlet side, on the exhaust wall 6 side. With this configuration, the exhaust gas first passes through the second exhaust gas purification catalyst body 10, which is heated to a high temperature in a short period of time, and unburned gas is decomposed. At this time, decomposition heat is generated, and the temperature of the second exhaust gas purification catalyst body 10 becomes higher, and the exhaust heat of the passing exhaust gas becomes high temperature, and this exhaust heat heats the first exhaust gas purification catalyst body 9, causing the catalyst to function. Raise the temperature to the desired temperature. Further, as the operating time of the device passes, the exhaust heat temperature increases, and the first exhaust gas purification catalyst body 9 reaches a state where it can fully demonstrate its unburned gas decomposition function.

High-frequency radio waves are reflected from surfaces with sudden changes in impedance. Therefore, if the opening of the waveguide 3 is placed directly in the vicinity of the second exhaust gas purification catalyst body 10, effective absorption of high frequency radio wave power will not take place. Furthermore, high-frequency radio waves are also traveling waves and are absorbed by objects close to the feeding surface. For this reason, it is effective to feed power into the air gap near the high-frequency radio wave power absorber.
A high frequency radio wave power feeding port 4 is provided in the gap between the intake wall 5 and the second exhaust gas purification catalyst body 10.

As described above, the high frequency heating exhaust gas purification device of the present invention is
A high-frequency radio wave power absorbing material is used as a part of the catalyst carrier of the purification catalyst, and the second exhaust gas purification catalyst 10 using this material is placed on the exhaust gas inlet side, and a gap is provided between it and the intake wall 5. Due to the characteristics of high-frequency radio waves, high-frequency radio power can be efficiently absorbed by supplying power to the body, and since the heat capacity of the high-frequency radio power absorber is small, it generates heat at a high temperature in a short period of time, effectively discharging unburned gas. Decomposition can be carried out, improving the functionality of the exhaust gas purification device.

Effects of the Invention As described above, according to the high frequency heating exhaust gas purification device of the present invention, the following effects can be obtained.

(1) Unlike external heating due to exhaust heat from a cooking device heating chamber, exhaust heat from an automobile engine, or heat from a heating means using an electric heater, this is internal heat generation of the catalyst carrier itself due to high frequency radio waves. The time it takes for the catalyst to rise to the temperature at which it functions actively is short.

(2) Since a high frequency radio wave power absorbing material is used for the catalyst carrier, high frequency radio wave power is efficiently absorbed.

(3) If the exhaust gas purification catalyst body is divided, the heat capacity of the catalyst carrier using a high-frequency radio wave power absorbing material will be smaller, and the catalyst will rise to a higher temperature in a shorter time at the initial stage of operation.

(4) With a configuration that takes advantage of the characteristics of high-frequency radio waves, an exhaust gas purification catalyst body using a high-frequency radio power absorbing material for the catalyst support is effectively heated.

(5) When a part of the catalyst support is brought to the exhaust gas inlet side as a material for absorbing high-frequency radio power, in the initial stage of operation, unburned gas is decomposed by the exhaust gas purification catalyst body on the inlet side, and during normal operation, the surface area is large. It heats a general catalyst carrier with exhaust heat and functions to purify exhaust gas that contains a large amount of unburned gas.

(6) The exhaust gas purification catalyst body is rapidly heated in the initial stage of operation, and it is possible to prevent unburned gas from passing through without being decomposed, or to reduce the amount of unburned gas passing through.

[Brief explanation of drawings]

The figure is a sectional view showing one embodiment of the present invention. 1... Heating chamber, 2... Magnetron,
4... High frequency radio wave power supply port, 10... Second exhaust gas purification catalyst body using a high frequency radio wave power absorbing material as a catalyst carrier. Name of agent: Patent attorney Shigetaka Awano, 1 person, heating type Mac, half-Torof Island, m-wave radio, electric outlet f1115, 1 sujo, 1 tributary, 1 person.

Claims (5)

[Claims] (1) A heating chamber to which high-frequency radio waves are supplied, a high-frequency radio wave oscillation source that supplies high-frequency radio waves to the heating chamber, and a gas-permeable catalyst carrier provided in the heating chamber, the catalyst carrier A high-frequency heating exhaust gas purification device comprising at least a portion of the heating chamber made of a high-frequency radio wave power absorbing material and supporting an exhaust gas purification catalyst, and an exhaust gas inlet and outlet to the heating chamber made of a metal transparent body. (2) The high-frequency heating exhaust gas purification device according to claim (1), wherein a ceramic body obtained by kneading barium titanate BaTiO_3 with cordierite or mullite is used as the catalyst carrier. (3) The high-frequency heating exhaust gas purification device according to claim (1), wherein silicon carbide SiC is used as the catalyst carrier. (4) A high frequency radio wave power absorbing material is used as a part of the catalyst carrier, the high frequency radio wave power absorbing material part is placed on the exhaust gas inlet side of the heating chamber, and the metal transparent body on the inlet side of the heating chamber and the catalyst carrier 2. The high-frequency heating exhaust gas purification device according to claim 1, wherein a gap of one-fourth wavelength or more is provided between the two. (5) The high-frequency heating exhaust gas purification device according to claim 4, wherein a high-frequency radio wave power supply port to the heating chamber is provided in a gap between the metal permeable body on the exhaust gas inlet side of the heating chamber and the catalyst support.