JPH0221947A - Catalytic structure for treating gas - Google Patents

Abstract

PURPOSE:To prevent the bulging-out of a dust deposit by providing 2 partial steps in a gas flowing direction on the end face of a wall surrounding respective gas passages in the catalyst itself constituting a gas-inflow side end. CONSTITUTION:The end face 6 of the wall 5 separating the gas passage into four sections is recessed from the end face 4 of the wall 3 surrounding the four gas passages 2 in the catalytic structure 1, and a step 7 is provided between both end faces. The gas 8 flows in direction of the arrow, and the dust in the gas is deposited on the end faces of the structure 1. The dust 9 deposited on the end face 4 of the surrounding wall 3 and the dust 10 on the end face 6 of the partition wall 5 are not formed in the same cross section by the presence of the step 7 between end faces 4 and 6. The deposited dust bulge out into the gas passage, but does not narrow the gas passage. As a result, clogging can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a parallel flow type catalyst structure used in an exhaust gas denitrification device, an internal combustion engine, an exhaust gas treatment device such as an internal combustion engine, or a gas engine.

(Prior Art) FIG. 3 is a conceptual diagram of a gas downflow type denitrification reactor. The reactor 17 has a built-in catalyst structure 1 in which vertical gas passages are provided in parallel, and the exhaust gas 8 is introduced from the gas port 18 and passes through the waste passage of the catalyst structure 1 to the gas outlet 1.
Denitrated gas is discharged from 9.

Conventionally, as shown in FIG. 4, catalyst structures used in this type of exhaust gas treatment device include (a) a hexagonal honeycomb cross-sectional shape, (b) a square grid-like cross-sectional shape, and (
c) Parallel gas passages are formed by bending a part of a plate-shaped catalyst and the convex part is brought into contact with the flat plate part; (d) Parallel gas passages are formed by inserting a wave-shaped catalyst between the flat catalysts. There are things.

(Problems to be Solved by the Invention) Figure 5 shows the specific surface area and mesh size (which determine the catalyst performance) using a lattice catalyst structure as an example of the above-mentioned catalyst structures.
This is a graph showing the relationship between pitch and pitch. Here, the pitch is the length of one side of the gas passage plus the thickness of one flat catalyst plate, and the specific surface area is the surface area per unit bulk volume. The larger this value is, the greater the catalytic ability is, so it is desirable to select a catalyst structure with a small pitch. However, if the pitch is small (
Because it is easy for one blockage to occur due to dust, etc., there is a certain limit to the size of the pitch depending on the properties of the dust.

Further, the end of this type of parallel flow type catalyst structure is formed in a single plane for manufacturing reasons, and the clogging phenomenon usually occurs at the end on the gas inlet 1 side.

FIG. 6 is a conceptual diagram of a conventional lattice catalyst structure.
(a) is a perspective view of the end on the side of gas man 1, and (h) is an enlarged view of the end. (c) and (d) are diagrams showing the state in which dust is attached to this catalyst structure, (c) is a V-V or Vl-Vl sectional view of (b), and (d) is a wing It is a front view. Note that in (d), the shaded area shows only the dust part where the dust protrudes into the gas passage.

Generally, the adhesive dust has a particle size of 1 μm or less and contains oil mist. Such a clogging phenomenon due to dust occurs when dust collides with the end of the catalyst structure and −',j ('
I'? Then, the dust that flies after that accumulates on the adhering trash 1-, is consolidated by the inertia of the flying dust and the dust pressure, and protrudes from all sides toward the dust passage, gradually reducing the passage. It is thought that when the size becomes smaller to a certain extent, the gas flow is suppressed and the accumulated dust forms bridges with each other, leading to complete blockage. In particular, it has been found that when the end face of the catalyst structure is an intermediate face, the protrusion phenomenon progresses simultaneously from all sides of the gas passage opening, resulting in clogging in a short period of time.

The present invention aims to eliminate the drawbacks mentioned above, to provide a catalyst structure that prevents the tast deposits from simultaneously protruding into the waste passage from all sides, and suppresses the progress of clogging of the gas passage. It is.

(Means for Solving the Problems) The present invention provides a catalyst structure for gas treatment in which a plurality of waste passages pass through in parallel, the catalyst itself constituting the gas inflow side end, or an auxiliary member attached to the catalyst end. This catalyst structure is characterized in that the end face of the wall surrounding each waste passage is provided with two or more partial steps in the gas flow direction.

(Function) The present invention provides two or more steps on the inlet side end face of the wall forming each gas passage of the gas parallel flow type catalyst structure, so that dust that adheres and accumulates on the end face is removed from the gas passage side. At the same time, it is possible to prevent dust from leaking out, delay bridging of dust, and suppress the progress of clogging phenomenon. As a result, even if the pinch of the catalyst structure is smaller than before, it is now possible to substantially secure the gas passage cross section for a long time, making the denitrification equipment, etc. that incorporates the catalyst structure significantly more compact. This made it possible to reduce the cost of the device extremely low.

(Example) FIGS. 1 and 2 are conceptual diagrams of a lattice-shaped catalyst structure that is an example of the present invention. (a) of both figures is a perspective view of the catalyst structure gas cylinder [21 side], and (1) is an enlarged view of the end of the catalyst structure. In addition, (c) and (d) show the state in which Tas 1- is attached to the catalyst structure, and (c)
) is a cross-sectional view of (b) (Fig. 1 (c) is a cross-sectional view of II or I + -, 11, and Fig. 2 (c) is a cross-sectional view of III-T
(Diagram combining TI cross-sectional view and IV-IV cross-sectional view), (d)
is a plan view of (c) seen from the flow direction of waste. (The shaded area shows only the part where the adhered dust protrudes into the gas passage.) The catalyst structure 1 shown in FIG. , the hW and H surfaces 6 of the wall 5 that divides the gas passage into 4-
The gas flow 8 is in the direction of the arrow. The dust in the residue adheres and accumulates on the end face of the catalyst structure 1, but the accumulated dust 9 on the end face of the colored surrounding wall 3 and the accumulated dust 10 on the end face of the partition wall 5 and the end face of the partition wall 5 are as follows. , due to the presence of the step 7 between the end faces 4 and 6, are not formed within the same cross section as shown in FIG. 1(c). Therefore, although some of the accumulated dust protrudes into the waste passage as shown in Fig. 1(d), both accumulated dust within the same cross section.
It does not narrow the waste passage. On the other hand, in the conventional catalyst structure shown in FIG. 6(c), it can be seen that the protruding part of the dust deposited on the end face narrows the gas passage within the same cross section.

In the lattice-shaped catalyst structure 1 shown in FIG. 2, the end surface 14 of the wall 13 that partitions the gas passages in each row is recessed relative to the end surface 12 of the wall 11 that separates the gas passages 2 in each row, and both end surfaces Figure 2 (
The step 7 shown in c) is provided, and the gas flow 8 is in the direction of the arrow.

By providing such a step 7 on the end face of the catalyst structure 1, dust 15 deposited on the end face 12 of the separation wall 11 and dust 16 deposited on the end face 14 of the partition wall 13 are reduced.
are not formed within the same cross section as shown in FIG. 2(c). Therefore, although the accumulated dust protrudes into the gas passage as shown in FIG. 2(d), the accumulated dust does not narrow the gas passage within the same cross section.

In addition, in the lattice-like catalyst structure, the gas passages are arranged at y [By making the end faces of the four constituent walls all at different positions, the dust deposited on each end face is placed at a cross-sectional position of W in total. is possible, and it is possible to further prevent narrowing and clogging of the gas passage.

In addition, even in a catalyst structure made of a combination of honeycombs or plate-like bodies other than a lattice-like structure, by providing two or more steps on the gas inlet side end face of the wall surrounding the gas passage, it is possible to It is possible to position the deposited tast on different cross sections 1-. As a result, similar to the lattice-shaped catalyst structure described above, narrowing or clogging of the gas passages can be prevented, so a structure with a smaller pitch can be used compared to the conventional (conventional) grid-shaped catalyst structure. Ta.

(Effects of the Invention) The present invention employs the configuration described in ``2'' to simplify clogging of the parallel flow type catalyst structure with dust.
As a result, it is possible to make the pitch smaller than that of conventional catalyst structures, so that catalyst structures with the same performance can be made significantly more compact. The device for embedding the catalyst structure could be made extremely inexpensive.

[Brief explanation of the drawing]

1 and 2 are conceptual diagrams of a lattice-like catalyst structure according to an embodiment of the present invention, in which (a) is a perspective view from the gas population side, (b) is an enlarged view of the end, (c) is a sectional view, and (d) is a plan view. Figure 3 is a conceptual diagram of a reactor containing a catalyst structure, Figures 4 (a) to (d) are cross-sectional views of various parallel flow type catalyst structures, and Figure 5 is a diagram of a lattice catalyst structure. It is a graph showing the relationship between pitch (mm) and specific surface area (m'#n3). FIG. 6 is a conceptual diagram of a conventional lattice-shaped catalyst structure, in which (a) is a perspective view of the gas inlet side, (b) is an enlarged view of the end, (c) is a cross-sectional view, and (d) is a plan view. It is a diagram.

Claims (1)

[Claims] In a gas processing catalyst structure in which a plurality of gas passages pass through in parallel, the catalyst itself constituting the gas inflow side end or the auxiliary member attached to the catalyst end has a gas inlet on the end face of the wall surrounding each gas passage. A catalyst structure characterized by having two or more partial steps in the flow direction.