JPH0448934A - Metal honeycomb catalyst - Google Patents

Abstract

PURPOSE:To enhance the reducing efficiency of a particulate by a method wherein a large number of cells mutually extending in parallel across thin walls by thin metal plates and coating the surfaces of the walls with a catalyst and providing a large number of small recessed parts to the surfaces of the walls. CONSTITUTION:Small recessed parts 5 are formed on the surface of the walls of flat plates 3 and corrugated plates 4 and a gas streams are disturbed to form a large number of small gas streams colliding with the recessed parts 5. Therefore, the dry soot in gas is bonded to the recessed parts 5 to be collected in a certain degree. When the number of cells per a unit area of outer peripheral parts 12 become more than those of inner peripheral parts 13 in respective layers wound in a multiple state, the exhaust temp. of the outer peripheral parts 12 becomes lower than that of the inner peripheral parts 13 by radiation and the catalitic reaction effect of the outer peripheral parts 12 becomes lower than that of the inner peripheral parts, and much gas flows through the inner peripheral parts 13 and catalytic reaction effect is enhanced. The contact efficiency of the gas and the catalyst becomes high even in the outer peripheral parts 12 and catalytic reaction advances in the same degree as the inner peripheral parts. As a result, catalytic reaction effect is enhanced as a whole and, therefore, a particulate can further be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a metal honeycomb catalyst, particularly one used for exhaust purification of a diesel engine.

(Prior Art) A metal honeycomb catalyst is one in which a large number of cells extending in parallel to each other are formed with thin metal plates, and the wall surfaces are coated with a catalyst.

In diesel engines, this metal honeycomb catalyst is installed in the exhaust passage, and when the exhaust from the engine is guided to each cell, the organic soluble components in the exhaust (hereinafter referred to as "5OFJ") react with the catalyst on the wall surface and burn. (Unexamined Japanese Patent Publication No. 1983)
36841, 63-36843, JP-A-1-5301
(See Publication No. 1).

(Am to be solved by the invention) In a diesel engine, the exhaust temperature is relatively low compared to a gasoline engine. However, unlike gasoline engines, the exhaust gas components include particulates (particulates).

This particulate is dry soot (carbon)
and 5OF (mostly unburned fuel components). SOF is easily combusted by a catalytic reaction even at relatively low temperatures (e.g. around 200°C), whereas dry soot is combusted even when a catalyst is not used. Relatively warm (for example 400
℃ or higher), it will not burn, and the combustion reaction rate is slow, so it cannot be burned unless it is attached to a catalyst.

For this reason, conventional honeycomb catalysts have little effect on reducing dry soot.

This invention was made by focusing on such conventional problems, and even with metal honeycomb catalysts, the particulate reduction effect is enhanced by attaching and collecting some dry soot. The purpose is to provide equipment.

(Means for Solving the Problems) The invention of NS1 is a nicum catalyst in which a large number of cells extending parallel to each other with thin walls are formed of thin metal plates, and a catalyst is coated on the surface of the walls. A large number of small recesses were provided on the wall surface.

The second invention is a metal honeycomb catalyst in which a large number of cells extending in parallel to each other are formed with thin metal plates, and the wall surface is coated with a catalyst, in which a large number of small recesses are formed on the wall surface. At the same time, the number of cells per unit volume at the outer periphery is larger than that at the center.

(Function) In each invention, when a small recess exists on the wall surface, the gas flow is disturbed by the recess, so a small gas flow collides with the recess, and dry soot in the gas adheres to and is trapped by the recess. 4s will be given.

In the second invention, a large amount of gas flows through the inner peripheral portion to enhance the catalytic reaction effect. In the outer periphery where the number of cells per unit volume is large, the efficiency of contact between the gas and the catalyst is high.

(Example) FIG. 1 shows the external appearance of a metal nicom catalyst according to an example of the first invention.

In the metal honeycomb structure W1, a large number of cells 2 are formed of thin metal plates and extend parallel to each other across thin walls.

As shown in FIG. 2, on the surface of the wall separating each cell 2,
A large number of PO sections 5 are formed. Note that Figure 2 is A of Figure 1.
It is an enlarged view of the part.

When one of these recesses 5 is further enlarged and shown in Figure tItJ3, the direction of the arrow in the figure is the upstream side, and there is a plane 6 perpendicular to the gas flow from the upstream side, and a plane 6 toward this plane 6 from the fluid side. A recess 5 is formed by a curved surface 7 that gradually becomes deeper. The concave portion is not limited to this, but may be anything that disturbs the gas flow from upstream, and the concave portion 8 formed only with a flat surface or only a curved surface as shown in FIGS. 5 and ff16,
It doesn't matter if it's 9.

The metal honeycomb catalyst 1 shown in FIG. 1 is formed as follows.

As shown in FIG. 2, a metal flat plate 3 and a corrugated plate 4 are prepared, and l'! ! ] A large number of small recesses 5 are provided on both surfaces of the flat plate 3 and the corrugated plate 4 by processing with a compression roller having a large number of small protrusions on the roller surface that fit into the portions 5. The material of each member 3 and 4 is, for example, a material close to stainless steel.

Next, these members 3 and 4 are stacked together as shown in FIG.
The metal honeycomb catalyst 1 shown in Fig. ff11 is completed by multiple winding from the inner circumference. Thereafter, the surfaces of the flat plate 3 and the corrugated plate 4 having the recesses 5 are coated with a catalyst.

The method of multiple winding shown in FIG. 4 is well known. According to this method, the spacing between each layer is equal from the center to the outer periphery, and the corrugated sheet 4 is formed with a substantially uniform size from the winding start end at the center to the winding end end at the outer periphery, so there is a high degree of freedom in shape. Become.

Here, the operation of this example will be explained.

Multiple winding of flat plate and corrugated plate without recesses! In the metal honeycomb catalyst formed by this method, the exhaust gas introduced into the cells passes directly from the cell inlet to the cell outlet, so that almost no dry soot is deposited.

On the other hand, if a small recess 5 is formed in the wall surface composed of a flat plate 3 and a corrugated plate 4 as in this example, the gas flow is disturbed and many small gas flows collide with the recess 5. It's getting smaller. Therefore, the dry soot in the gas is absorbed into the recess 5.
The dry soot will be collected to some extent.

Also, if the contact area with the base increases due to the presence of the recess 5,
Since the contact efficiency between the gas and the catalyst is also increased, not only SOF but also HC and CO can be combusted.

In other words, according to this example, not only can dry soot be adhered and collected to some extent, but the effect of reducing particulates as a whole can be improved.

FIG. 7 is a longitudinal cross-sectional view of a metal honeycomb catalyst 11 according to an embodiment of the invention of pIS2. 1
2, so that the number of cells per unit area in the outer peripheral part 12 is larger than that in the inner peripheral part 13.
ld! It's something like that.

This was done in consideration of the fact that the exhaust gas temperature in the outer circumference 12 is lower than that in the inner circumference 13 due to heat radiation, so the catalytic reaction effect in the outer circumference 12 is lower than that in the inner circumference. A large amount of water flows through the peripheral portion 13 to enhance the catalytic reaction effect. In addition, since the contact efficiency between the gas and the catalyst is increased in the outer peripheral portion 12,
The catalytic reaction proceeds to the same extent as in the inner periphery.

As a result, the overall catalytic reaction effect improves, so
Particulates can be further reduced than in the previous embodiment.

lastly,! In Figure #2, the recesses 5 are provided on both the flat plate 3 and the corrugated plate 4, and also on both sides, but they may be provided only on one side or only on one side.

(Effects of the Invention) In the first invention, since a large number of small recesses are provided on the wall surface, the dry soot can be attached and collected to some extent, and the effect of reducing particulates as a whole is improved.

In the invention of ¥S2, the number of cells per unit volume in the outer periphery is larger than that in the center, so that the overall catalytic reaction effect is improved.

[Brief explanation of drawings]

Figure 1 is a perspective view of a metal honeycomb catalyst according to an embodiment of WSL's invention, Figure 2 is an enlarged view of part A of Figure 11111, and IJS
3 is an enlarged view of the recess of this example, FIG. 4 is a perspective view for explaining the method of forming the metal honeycomb catalyst of this example, and FIGS. 5 and 6 are enlarged views of the recess of other examples. FIG. 7 is a longitudinal sectional view of a metal honeycomb catalyst according to an embodiment of the second invention. 1...Metal honeycomb catalyst, 2...Cell, 3...
Flat plate, 4... Corrugated plate, 5... Concave portion, 6... Plane, 7
...Curved surface, 8°9...Concave portion, 11...Metal honeycomb catalyst, 12...Outer periphery, 13...Inner periphery. Figure 5 Figure 4 Figure 16 Figure

Claims (2)

[Claims] 1. A metal honeycomb catalyst in which a large number of cells extending parallel to each other across thin walls are formed of thin metal plates, and the wall surface is coated with a catalyst, characterized in that the wall surface is provided with a large number of small recesses. honeycomb catalyst. 2. In a metal honeycomb catalyst, in which a large number of cells extending parallel to each other are formed by thin metal plates separated by thin walls, and the wall surface is coated with a catalyst, a large number of small recesses are provided on the wall surface, and the unit volume of the outer periphery is A metal honeycomb catalyst characterized by having more cells in each area than in the center.