JPH11166411A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate particle materials(PM) in exhaust gas without any increases in exhaust resistance. SOLUTION: In the entire area of an exhaust pipe 3 positioned more downstream than a catalyst converter, a recessed part 5 is formed nearly on the full surface inside of the exhaust pipe 3, and this is covered with a net body 6 to form a space part 7. PM 10 in exhaust gas flows through the hole of the net body 6 into space part 7 while flowing down the exhaust pipe 3, is clashed with the inner wall surface of the recessed part 5 to be stuck, or clashed with PM already stuck to the inner wall surface of the recessed part 5 to be stuck, and the particle diameter of the PM is gradually grown. Because of the large particle diameter, the PM 22 grown in the inner wall surface of the recessed part 5 is prevented from being shifted from the space part even if it tries to flow through the hole of the net body 6, even when it is peeled off from the inner wall surface. NO2 or SO3 in exhaust gas is clashed with the PM 11 in the space part 7 and adsorbed on the PM 11.

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 apparatus for purifying exhaust gas discharged from an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, particularly a diesel engine, soot and SOF (Soluble Organic Frac
It is necessary to remove particulate matter (hereinafter abbreviated as PM) such as exhaust gas and discharge the exhaust gas to the atmosphere. Conventionally, a filter called a DPF (Diesel Particulate filter) is provided in an exhaust passage, and this is used. PM was being collected.

As disclosed in Japanese Utility Model Application Laid-Open No. 58-132520, a conventional DPF has a large number of elongated cells separated by a porous thin wall, and the upstream side is opened and the downstream side is closed. The exhausted gas passes through the thin wall from the cell with the upstream opening to the cell with the downstream opening through the thin wall. It has a structure in which PM in the exhaust gas is collected on the thin wall at that time.

[0004]

However, in the conventional DPF, as the amount of trapped PM increases, the thin wall becomes clogged, the pressure loss increases, and the exhaust resistance increases. There is a problem that the load increases.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to solve the problem of exhaust gas of an internal combustion engine which does not increase exhaust resistance even if PM is collected. It is to provide a purification device.

[0006]

The present invention has the following features to attain the object mentioned above. The present invention relates to an exhaust gas purification device that purifies exhaust gas discharged from an internal combustion engine, and a particle growth unit that attaches and grows particulate matter in the exhaust gas to at least a part of an inner surface of an exhaust passage through which the exhaust gas flows. And a particle outflow regulating means for allowing exhaust gas to flow through the particle growth section and preventing the particulate matter grown in the particle growth section from flowing out.

[0007] PM in the exhaust gas passes through the particle outflow restricting means together with the exhaust gas, flows into the particle growing section, collides with the wall surface of the particle growing section, and adheres. Further PM adheres to the PM that has adhered to the particle growth part one after another,
PM grows by gradually increasing its particle size. Even if the PM having such a large particle diameter separates from the wall surface of the particle growth part, it cannot pass through the particle outflow control means, so that it stays in the particle growth part and drastically reduces the amount of PM released to the atmosphere. Can be done. Since the exhaust gas can flow on the axial center side of the exhaust passage rather than the particle outflow restricting means, even if the amount of PM collected in the particle growing portion increases,
The exhaust resistance does not increase. Further, since PM has the ability to adsorb NOx and SOx, NOx and SOx in the exhaust gas are adsorbed by the PM collected in the particle growth section. Further, the PM collected in the particle growth section is slowly oxidized to CO ₂ at the exhaust gas temperature, and at the same time, NOx and SOx attached to the PM are reduced to NO and SO ₂ gas. It is released from the PM, discharged through the exhaust passage through the particle outflow control means, and released to the atmosphere.

The particle growth section and the particle outflow control means are preferably provided all around the inner surface of the exhaust passage, and are preferably provided as long as possible in the flow direction of the exhaust gas. The muffler can be considered as a part of the exhaust passage, and a particle growth portion and a particle outflow regulating member may be provided on the inner surface of the muffler.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, a catalyst having an oxidizing ability is provided in the exhaust passage, and the particles are provided on the entire inner surface of the exhaust passage over substantially the entire length of the exhaust passage downstream of the catalyst. A growth unit and a particle outflow control unit may be provided. In this way, NOx or SOx generated when the exhaust gas passes through the catalyst can be adsorbed by the PM collected in the particle growing section. Examples of the catalyst include an oxidation catalyst and a NOx catalyst.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described below with reference to FIGS.

FIG. 1 is an overall configuration diagram of an exhaust gas purification apparatus applied to a diesel engine 1 as an internal combustion engine. Exhaust gas discharged from the diesel engine 1 flows out of an exhaust manifold (exhaust passage) 2 to an exhaust pipe (exhaust passage) 3. A catalytic converter 4 containing a NOx catalyst therein is provided in the exhaust pipe 3. NOx in the exhaust gas is decomposed and purified by the NOx catalyst.
Some of which may flow downstream of the catalytic converter 4 in the form of NO _2. Further, the exhaust gas contains a large amount of SO ₂ generated by burning the sulfur content of the fuel,
This SO ₂ may be oxidized by the catalytic converter 4 to become SO ₃ .

As shown in FIG. 2, a concave portion 5 is formed on almost the entire inner surface of the exhaust pipe 3 in the entire area of the exhaust pipe 3 located downstream of the catalytic converter 4. The recess 5 is covered with a net 6 having an extremely small hole diameter, and a space 7 is formed between the net 6 and the inner wall surface of the recess 5. Here, the mesh body 6 constitutes a particle outflow regulating member, and the concave portion 5 and the space portion 7 constitute a particle growth portion. Instead of the net 6, a porous body (ceramic or sintered metal) having a small hole (cell) diameter can be used.

By the way, part of the PM in the exhaust gas (mainly SOF) is oxidized to CO ₂ when passing through the catalytic converter 4, but most of the PM (mainly soot) remains as it is. It passes through the catalytic converter 4 in the form. As shown in FIG. 2, the PM 10 that has passed through the catalytic converter 4 flows into the space 7 through the hole of the mesh body 6 while flowing down the exhaust pipe 3, and collides with and adheres to the inner wall surface of the recess 5. Or, it collides with PM already attached to the inner wall surface of the concave portion 5 and adheres.
In this way, the PM adhering to the inner wall surface of the concave portion 5 gradually grows the particle size. P grown on the inner wall surface of the recess 5
Even when M11 is separated from the inner wall surface by vibration or the like, the separated PM has a large particle size, and thus passes through the hole of the mesh body 6 to form the space 7
Cannot be detached from In other words, the hole diameter of the mesh body 6 is set so that fine PM can pass through but not larger than a predetermined size.

[0014] On the other hand, since the PM (mostly soot) is capable of adsorbing NO ₂ or SO _3, NO ₂ and SO ₃ in the exhaust gas flowing downstream of the catalytic converter 4 is present in the space portion 7 When colliding with PM11, these NO ₂ and SO _{3 become} PM11
Is adsorbed.

The PM 11 in the space 7 slowly oxidizes at the temperature of the exhaust gas, and takes a long time to emit CO2.
₂ and at the same time, NO ₂ and SO ₃ adsorbed on the PM 11 are reduced to become NO or SO ₂ gas and desorbed from the PM 11, pass through the holes of the mesh body 6, and pass through the exhaust pipe 3. And is released to the atmosphere.

Note that PM has less activity than activated carbon,
Since the exhaust gas does not pass through the layer of PM 11 formed in the space 7, the PM in the space 7 does not burn at a normal exhaust gas temperature, and a slow oxidation reaction occurs. Present.

As described above, in this exhaust gas purifying apparatus, PM in the exhaust gas is collected in the space 7 of the exhaust pipe 3 and at the same time, a part of it is released to the atmosphere as CO ₂ . On the other hand, most of the NOx is purified in the catalytic converter 4, but the NO.
₂ and SO ₃ generated by oxidation in the catalytic converter 4
The PM is adsorbed by the PM in the space 7, and a part of the PM is further oxidized to NO or SO ₂ gas and released to the atmosphere. In any case, PM in the exhaust gas can be removed, NOx and SOx can be reformed and released to the atmosphere.

Further, as described above, even if the PM adhering to the inner wall surface of the concave portion 5 is separated from the inner wall surface of the concave portion 5 due to vibration or the like, the separated PM has a large particle size.
From SO _2, and therefore NO ₂ or SO ₃
There is no possibility that the PM adsorbed is desorbed from the space 7 and released to the atmosphere.

Further, since the PM layer formed on the inner surface of the exhaust pipe 3 functions as a heat insulating material, the exhaust gas is kept warm,
Promotes the oxidation reaction of PM. As shown in FIG. 3, porous bodies 8 and 9 made of ceramic or metal foam (sintered metal) are laminated on the inner surface of the exhaust pipe 3, and the first layer of porous body 8 near the inner surface of the exhaust pipe 3 is formed. Is constituted by a porous body having a relatively large pore (cell) diameter, the porous body 8 is used as a particle growth part, and the porous body 9 of the second layer on the far side from the inner surface of the exhaust pipe 3 has a pore (cell) diameter The porous body 9 may be configured as a particle outflow restricting means.

In this case, the PM in the exhaust gas passes through the holes of the porous body 9 of the second layer, reaches the holes of the porous body 8 of the first layer, and collides with the inner wall surface of the holes of the porous body 8. And grow the particle size. When the particle size of the PM becomes larger than the pore size of the porous body 9 of the second layer, the PM cannot be removed from the porous body 8 of the first layer.

Further, a particle growth section and a particle outflow regulating member may be provided on the inner surface of the muffler forming a part of the exhaust passage.

[0022]

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, a particle growth section for adhering and growing particulate matter in the exhaust gas to at least a part of the inner surface of the exhaust passage through which the exhaust gas flows is provided. By having a particle outflow regulating means that allows exhaust gas to flow through the particle growth section and prevents the particulate matter grown in the particle growth section from flowing out, without increasing exhaust resistance, Particulate matter can be removed from the exhaust gas.

In the case where a catalyst having oxidizing ability is provided in the exhaust passage, and the particle growth portion and the particle outflow regulating means are provided on the entire inner surface of the exhaust passage over substantially the entire length of the exhaust passage downstream of the catalyst. Can remove not only particulate matter in the exhaust gas but also NOx and SOx in the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an exhaust gas purification device for an internal combustion engine according to the present invention.

FIG. 2 is a sectional view of an exhaust passage of the exhaust purification device.

FIG. 3 is a cross-sectional view of an exhaust passage according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine (internal combustion engine) 2 Exhaust manifold (exhaust passage) 3 Exhaust pipe (exhaust passage) 4 Catalytic converter 5 Depressed part (particle growth part) 6 Network (particle outflow regulation means) 7 Space part (particle growth part) 8th One layer porous body (particle growth part) 9 Second layer porous body (particle outflow regulating means) 10, 11 Particulate matter

Claims (2)

[Claims] 1. An exhaust gas purifying apparatus for purifying exhaust gas discharged from an internal combustion engine, wherein a particle growing section for attaching and growing particulate matter in the exhaust gas to at least a part of an inner surface of an exhaust passage through which the exhaust gas flows. And a particle outflow regulating means for permitting exhaust gas to flow through the particle growing portion and preventing the particulate matter grown in the particle growing portion from flowing out. Purification device. 2. The method according to claim 2, wherein a catalyst having an oxidizing ability is provided in the exhaust passage, and the particle growth portion and the particle outflow regulating means are provided on the entire inner surface of the exhaust passage over substantially the entire length of the exhaust passage downstream of the catalyst. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein: