JPH0893455A - Device and method for controlling exhaust emission using infrared ray - Google Patents

Abstract

PURPOSE: To excellently control NOx even in the atmosphere with high oxygen concentration by providing an infrared ray generating part to emit the infrared ray by the exhaust heat in an exhaust gas passage of an internal combustion engine, and providing a catalyst reacting part to control the atmospheric pollutant in the exhaust gas in the downstream of the infrared ray generating part. CONSTITUTION: The exhaust gas introduced in an exhaust gas inlet 12 from a lean burn gasoline engine passes through a jacket passage 9 arranged on the outer circumference of an infrared ray generating part 1, and HC gas and CO gas are burned. The exhaust gas then passes an oxidation catalyst 10 to transfer the heat to the infrared ray generating part 1, and then is introduced to the infrared ray generating part l. The infrared ray generating part 1 is uniformly heated by the heat of the exhaust gas, and generates the infrared ray mainly consisting of the prescribed wavelength suitable for making NOx in the excited condition. NOx which passes through the infrared ray generating part 1 and is in the excited condition is easily reduced and controlled, and the controlled exhaust gas is discharged from an exhaust gas outlet 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying exhaust gas discharged from an internal combustion engine and a method for purifying exhaust gas, and more particularly to exhaust gas from an internal combustion engine such as a lean burn gasoline engine or diesel engine in a lean burn state. Exhaust gas purifying apparatus and exhaust gas purifying method.

[0002]

2. Description of the Related Art Exhaust gas discharged from an internal combustion engine (engine, etc.) of an automobile or the like contains harmful components such as NO _x and causes a problem of air pollution.
To reduce the harmful components O _X such, it is already known to arrange an exhaust gas purification catalyst such as a three-way catalyst in an exhaust gas passage of an internal combustion engine.

Further, there is known a purifying apparatus for purifying HC and CO components in exhaust gas by providing a coat layer containing an infrared radiation substance and a catalyst component on the surface of a catalyst carrier carrying an exhaust gas purifying catalyst ( JP-A-4-87625).

On the other hand, in recent years, lean-burn gasoline engines using a lean gas mixture have been attracting attention and are being used because of improved fuel economy.

[0005]

However, in purifying exhaust gas, it is generally said that the NO _x reduction reaction does not easily proceed in an atmosphere with a high oxygen concentration. In particular,
Under operating conditions such as lean burn gasoline engine in a lean combustion state where the amount of oxygen becomes excessive, it is difficult to reduce NO _x in the exhaust gas by a purification catalyst such as a three-way catalyst. .

Conventionally, NO _{x in} the exhaust gas of a lean burn gasoline engine to which a purifying catalyst such as a three-way catalyst cannot be applied.
As a method of removing NOx, for example, hydrocarbons and the like are coexisted in the exhaust gas as a reducing agent, and NO _x in the exhaust gas is removed by a purifying catalyst.
919 JP have been proposed in JP-A 6-63359 discloses such, exhaust gas from lean burn gasoline engines, originally carbon monoxide, since the combustible materials such as hydrocarbons is small, NO _x by this method In order to remove the above, there was a disadvantage that hydrocarbons had to be added from the outside to the exhaust gas of the lean burn gasoline engine.

In the purifying apparatus described in Japanese Patent Laid-Open No. 4-87625, the catalyst component and the infrared irradiating substance are carried on the same catalyst carrier, so that the efficiency of the infrared irradiating is poor and the catalytic reaction Since infrared rays are generated at the same time, the temperature rises at the inlet of the purifier due to a catalytic reaction,
Since the temperature rise is low near the outlet, there is a problem that it is difficult to generate infrared rays having a uniform wavelength and it is difficult to uniformly carry out the catalytic reaction on the catalyst carrier. Furthermore, this purification device is not intended for exhaust gas purification of an internal combustion engine in a lean burn state, nor is there any mention of NO _x removal.

Therefore, according to the present invention, it is not an essential requirement to add hydrocarbons even in an atmosphere with a high oxygen concentration (lean side), and an exhaust gas purifying device and an exhaust gas which can purify NO _x well. The purpose is to provide a purification method. A further object of the present invention is to provide an exhaust gas purifying apparatus and an exhaust gas purifying method that can be mounted on an internal combustion engine that uses a wide range of air-fuel ratios including a lean burn gasoline engine and the like.

[0009]

In order to solve the above-mentioned problems, an exhaust gas purifying apparatus using infrared rays according to the present invention is an exhaust gas discharged from an internal combustion engine, particularly in a lean burn state. An exhaust gas passage for exhaust gas discharged from an internal combustion engine is provided with an infrared generator capable of emitting infrared rays by heat of the exhaust gas itself discharged from the internal combustion engine, and on the downstream side of the infrared generator. It is characterized in that a catalytic reaction unit capable of purifying air pollutants contained in the exhaust gas by a catalytic reaction is provided.

Further, in the exhaust gas purifying method using infrared rays of the present invention, (1) a layer of a black body substance is formed on the carrier by the heat of the exhaust gas itself discharged from the internal combustion engine in a lean burn state. Infrared rays are emitted from the infrared ray generating part formed by (2) the NO _x in the exhaust gas is activated by the infrared rays, and (3) the exhaust gas containing the activated NO _x ,
It is characterized in that purification is carried out by the catalytic action of a catalytic reaction section having a three-way catalyst or a NO _x reduction catalyst provided downstream of the infrared ray generation section.

The heat supplied to the infrared ray generating portion of the exhaust gas purifying apparatus of the present invention may be the heat of the exhaust gas itself, as well as the heat from another heat generating source. In order to stably irradiate the exhaust gas with infrared rays in the infrared ray generation section, it is effective to use such another heat generation source in combination.

In the exhaust gas purifying apparatus of the present invention, the infrared ray generating portion has a jacket passage whose outer periphery is covered with an exhaust gas passage for exhaust gas discharged from the internal combustion engine, and the jacket passage has infrared rays generating portion. It is preferable to communicate with the inlet of the section in order to uniformly heat the infrared ray generating section.

When an oxidation catalyst for generating infrared rays in the infrared ray portion by the combustion heat of HC and / or CO is arranged in the jacket passage, the combustion heat is introduced into the infrared ray generating portion. Strength increases, NO
NO performed after _x is activated more
_x There is an advantage that the purification process is performed more effectively.

In the exhaust gas purifying apparatus of the present invention, the infrared ray generating portion can be manufactured by forming a layer of a black body substance on a carrier, and allows the exhaust gas to pass through after the exhaust gas comes into contact with the carrier. The structure. For the infrared ray generating portion having such a structure, for example, a monolith type carrier, a pellet type carrier, or a plate-shaped carrier on which a layer of a blackbody substance is formed can be used. The surface area of the carrier is preferably large in order to increase the infrared irradiation area of the exhaust gas. As the material of the carrier, ceramics, metal or the like can be used.

In the exhaust gas purifying apparatus of the present invention, the black body substance used in the infrared ray generating portion is a black body substance which emits infrared rays by heat, and has a certain heat resistance (200
The material does not matter as long as it has a temperature of around ℃. For example,
Yellow-brown alumite, alumina, or 60% MnO ₂ , FeO 20%, CuO 10% on petalite and limestone,
An example is one in which a calcined product obtained by calcining a composition consisting of 10% CoO at 1100 ° C. was added. The method of forming the layer of the blackbody substance on the surface of the carrier can be performed by a general coating means, impregnation means, thermal spraying means or the like. Since the absorption region for the infrared rays of NO _x is the near infrared region and the mid-infrared region, it is preferable that the infrared ray generated by the infrared ray generating portion has these wavelength regions.

In the exhaust gas purifying apparatus of the present invention, the catalytic reaction section is a well-known three-component catalyst carrier that carries a catalytic metal capable of decomposing and purifying NO _x , HC, CO and the like on the catalyst carrier. the original catalyst, or NO _X reduction catalyst can be used.

The exhaust gas purifying device of the present invention is not only applicable to an exhaust gas purifying device discharged from an internal combustion engine in a lean burn state such as a lean burn gasoline engine or a diesel engine, but a three-way catalyst is used. It can also be applied to the exhaust gas of a general engine used.

[0018]

The heat of the exhaust gas itself emitted from the engine heats the infrared ray generating portion to radiate infrared rays from the black body material. NO _x in the exhaust gas absorbs the emitted infrared rays and NO _x molecules are heated and activated to be in an excited state. The excited NO _x reaches the catalytic reaction part as it is. Therefore, conventionally, it was difficult to purify NO _{x in} the exhaust gas of the internal combustion engine in the lean burn state, but in the present invention, the purified catalytic reaction in the catalytic reaction portion is promoted by the excited state of NO _x. .

In the exhaust gas purifying apparatus of the present invention, since the infrared ray generating section and the catalytic reaction section are independent, the infrared ray is efficiently generated and the heating becomes uniform, so that it is suitable for exciting NO _x. Infrared rays having various wavelengths (specific wavelengths in the range of 5 to 6 μm) can be generated, and the excited NO _x is then effectively purified in the catalytic reaction part.

In the exhaust gas purifying apparatus of the present invention, since the outer periphery of the infrared ray generating portion is covered with the jacket passage through which the exhaust gas from the internal combustion engine passes, the infrared ray generating portion is uniformly heated and uniform infrared ray generation is performed. Be seen. Therefore, infrared rays mainly having a wavelength effective for exciting NO _x (a specific wavelength in the range of 5 to 6 μm) are uniformly generated, and then the excited N is excited.
The O _x can be effectively purified by the catalytic reaction section.

[0021]

【Example】

[Embodiment 1] FIG. 1 shows an experimental apparatus used in an experiment for confirming the effect of the exhaust gas purifying apparatus using infrared rays according to the present invention. Reference numeral 1 denotes an infrared ray generation unit for irradiating infrared rays to exhaust gas from the gasoline engine 3 which is in a lean burn state with an air-fuel ratio A / F of about 15.7. The infrared ray generating section 1 is obtained by applying a general ceramic powder for infrared heaters in a slurry form with an organic solvent to a monolithic carrier made of stainless steel, which is known as a general catalyst carrier, and drying it to 700 to 1 Sintered at 1,000 ° C. FIG. 2 shows the entire structure of the infrared ray generator 1 used in this embodiment.

The infrared ray generating section 1 is a catalytic reaction section 2 which comprises a gasoline engine 3 and a three-way catalyst for catalytically decomposing harmful substances such as NO _x , HC and CO in exhaust gas.
Is disposed on the exhaust gas passage 6 between An exhaust gas measuring device 5 for collecting a part of the exhaust gas and measuring its components is disposed on the exhaust gas passage 7 downstream of the catalytic reaction unit 2. In order to facilitate the setting of the temperature condition of the infrared ray generator 1, the infrared ray generator 1 is provided with a gas burner 4.

The infrared generator 1 was heated to about 500 ° C. by the gas burner 4 using the experimental apparatus shown in FIG. Next, the gasoline engine 3 was started, and at the same time, the exhaust gas measuring device 5 measured the concentration change of NO _{x in} the exhaust gas with respect to the elapsed time. The result is shown in FIG. In FIG. 3, a curve a indicates that the temperature is from room temperature to 70 without heating the three-way catalyst.
A comparative example when the temperature of the exhaust gas rises up to ℃ is shown. A curve b shows a comparative example when the temperature of the three-way catalyst is heated to 200 ° C. constantly. A curve c shows an example of the present invention when the temperature rises by irradiating the exhaust gas with infrared rays and reacting from room temperature to 200 ° C. without heating the three-way catalyst.

According to FIG. 3, when the NO _x concentration in the exhaust gas is stabilized, the present invention (curve c) is 98% more than the comparative example (curve a), and the comparative example (curve b). It can be seen that the NO _x concentration in the exhaust gas is reduced by about 96% as compared with (1). Therefore, it is understood that the exhaust gas purifying apparatus using infrared rays according to the present invention has a remarkable effect in decomposing and removing harmful components in exhaust gas, particularly NO _x . Moreover, when CO in the exhaust gas was measured by the exhaust gas measuring device 5, there was a reduction effect of about 25% as compared with the conventional purification device (only the three-way catalyst).

[Embodiment 2] In Embodiment 2, a jacket passage covered with an exhaust gas passage for exhaust gas discharged from an internal combustion engine is arranged on the outer periphery of the infrared ray generating portion, and a jacket passage is provided downstream of the infrared ray generating portion. FIG. 4 is an example of an exhaust gas purifying apparatus in which a catalytic reaction part made of a three-way catalyst is arranged on the side, and FIG. 4 shows a cross-sectional view of the exhaust gas purifying apparatus.

In FIG. 4, the exhaust gas introduced into the exhaust gas inlet 12 passes through the jacket passage 9 arranged on the outer periphery of the infrared ray generating section 1, and the HC gas, the CO gas provided in the middle of the jacket passage 9 After burning the gas and passing through the oxidation catalyst 10 for transmitting heat to the infrared ray generator 1,
It is guided to the infrared ray generator 1. The infrared ray generator 1 is uniformly heated by the heat of the exhaust gas passing through the jacket passage 9, and when the exhaust gas passes, NO _x is generated.
Infrared rays mainly having a specific wavelength (specific wavelength in the range of 5 to 6 μm) suitable for bringing into the excited state are generated. Exhaust gas containing NO _X gas that has been excited by passing through the infrared ray generating unit 1 then passes through the catalytic reaction unit 2 including a three-way catalyst, and the excited NO _X in the exhaust gas can be easily converted. The reduced and purified exhaust gas is discharged from the exhaust gas outlet 13. A three-way catalyst is held by the mesh 11 on the outlet side of the catalytic reaction unit 2.

[0027]

INDUSTRIAL APPLICABILITY The exhaust gas purifying apparatus using infrared rays according to the present invention has a feature that NO _x can be satisfactorily purified without adding hydrocarbons in an atmosphere with a high oxygen concentration (lean side). , Lean-burn gasoline engines, etc., and can be mounted on lean-burn internal combustion engines.

In the exhaust gas purifying apparatus utilizing infrared rays of the present invention, since the infrared ray generating section and the catalytic reaction section are independent, the infrared ray generating efficiency is high and the infrared ray having a uniform wavelength suitable for exciting NO _x is generated. Then, NO _x can be excited, and then NO _x can be effectively purified in the catalytic reaction part. Therefore, normally, the NO in the exhaust gas of an internal combustion engine in a lean burn state is
_{Although x} was difficult to purify with a three-way catalyst or the like, the present invention enables purification.

In the exhaust gas purifying apparatus using infrared rays according to the present invention, the outer circumference of the infrared ray generating portion is covered with the jacket passage through which the exhaust gas from the internal combustion engine passes, so that the infrared ray generating portion is uniformly heated and uniform. Infrared radiation is generated. Therefore, infrared rays having a wavelength effective for exciting NO _x can be uniformly generated, and then the excited NO _x can be effectively purified by the catalytic reaction part.

[Brief description of drawings]

FIG. 1 shows an experimental apparatus used in an experiment for confirming the effect of an exhaust gas purifying apparatus using infrared rays according to the present invention.

FIG. 2 shows the entire structure of an infrared ray generating unit used in the examples.

FIG. 3 shows changes in the concentration of NO _{x in} the exhaust gas with the passage of time when the exhaust gas purifying apparatus using infrared rays according to the present invention is used.

[Fig. 4] Exhaust gas purification in which a jacket passage covered with an exhaust gas passage for exhaust gas discharged from an internal combustion engine is arranged on the outer periphery of an infrared generation portion, and a catalytic reaction portion is arranged on the downstream side of the infrared generation portion. It is sectional drawing of an apparatus.

[Explanation of symbols]

 1 Infrared ray generating part 2 Catalytic reaction part 3 Gasoline engine 4 Gas burner 5 Exhaust gas measuring device 6,7 Exhaust gas passage 9 Jacket passage 10 Oxidation catalyst 11 Mesh 12 Exhaust gas inlet 13 Exhaust gas outlet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01D 53/74 B01J 19/12 ZAB Z 9342-4D 35/02 J F01N 3/08 ZAB C 3 / 24 CL ZAB A (72) Inventor Ryoichi Yamanouchi 2-19-12 Sotokanda, Chiyoda-ku, Tokyo Equas Research Co., Ltd. (72) Inventor Naoto Chikakawa 2-19-12 Sotokanda, Chiyoda-ku, Tokyo No. In stock company Equus Research (72) Inventor Masao Kawai 2-19-12 Sotokanda, Chiyoda-ku, Tokyo Within Equus Research company

Claims (8)

[Claims] 1. An infrared generator capable of emitting infrared rays by heat of the exhaust gas itself discharged from the internal combustion engine is provided in an exhaust gas passage for the exhaust gas discharged from the internal combustion engine. An exhaust gas purifying apparatus using infrared rays, characterized in that a catalytic reaction portion capable of purifying air pollutants contained in the exhaust gas by a catalytic reaction is provided on the downstream side of the exhaust gas. 2. An infrared generator capable of emitting infrared rays by the heat of the exhaust gas itself discharged from the internal combustion engine is provided in an exhaust gas passage for the exhaust gas discharged from the internal combustion engine. On the downstream side, a catalyst reaction part capable of purifying air pollutants contained in the exhaust gas by a catalytic reaction is provided, and the infrared ray generation part is a carrier in which a layer of a black body substance is formed, Further, the exhaust gas purifying apparatus utilizing infrared rays is characterized in that the catalytic reaction part is a three-way catalyst or a NO _x reduction catalyst in which a catalyst metal is carried on a carrier. 3. The infrared generator has a jacket passage whose outer periphery is covered with an exhaust gas passage for exhaust gas discharged from an internal combustion engine, and the jacket passage communicates with an inlet of the infrared generator. An exhaust gas purifying apparatus using infrared rays according to claim 1 or 2, characterized in that: 4. The exhaust gas purifying apparatus using infrared rays according to claim 3, wherein an oxidation catalyst for generating infrared rays by combustion heat of HC and / or CO is arranged in the jacket passage. . 5. The internal combustion engine is a lean burn internal combustion engine.
Alternatively, an exhaust gas purifying apparatus that uses infrared rays according to 4 above. 6. (1) The heat of exhaust gas itself discharged from an internal combustion engine in a lean burn state causes infrared rays to be emitted from an infrared ray generating section formed by a layer of a blackbody substance on a carrier, 2) The infrared rays activate NO _x in the exhaust gas, and (3) the exhaust gas containing the activated NO _x is a three-way catalyst or NO _x reduction provided downstream of the infrared ray generating section. An exhaust gas purifying method using infrared rays, characterized by purifying by a catalytic action of a catalytic reaction portion having a catalyst. 7. A method of radiating infrared rays from an infrared ray generating section in which a layer of a blackbody substance is formed on a carrier by the heat of exhaust gas itself discharged from an internal combustion engine in a lean burn state is an infrared ray. The exhaust gas purification method using infrared rays according to claim 6, wherein heat conducted from a jacket passage through which exhaust gas discharged from an internal combustion engine that covers the generating portion is indirectly used. 8. The method of radiating infrared rays from the infrared ray generating section uses, in addition to the heat of the exhaust gas itself discharged from the internal combustion engine, heat from another heat generating source in combination. An exhaust gas purification method using infrared rays according to claim 6 or 7.