JP2012076044A - Catalyst and catalyst structure for treatment of exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for treatment of exhaust gas and its structure capable of exhibiting the catalyst performance to the maximum by bringing gas flow speed in a crest part close to gas flow speed in a flat plate part, that is, by reducing the maximum gas flow speed in a flow passage.SOLUTION: This plate shaped catalyst for treatment of exhaust gas is so configured that a catalyst component is carried on a plate shaped body with a plurality of rows of projecting line and recessed line parts (crest parts) of a specified height, alternately arranged in the flat plate part with intervals. In the recessed and protruded crest parts arranged on the flat plate part, a width w (width of the crest part) of the foot of a crest flow passage formed from a starting point α from the flat plate part to an end point γ in a position on the flat plate same with the starting point via a vertex β of the crest part is less than the height of the crest part (w<h or w/h<1.0).

Description

  The present invention relates to a catalyst for exhaust gas treatment and a catalyst structure, and more particularly to a plate-like catalyst for purifying harmful substances contained in exhaust gas and the structure thereof.

The catalyst for purifying harmful substances contained in the exhaust gas has various shapes such as a plate shape, a honeycomb shape, a granular shape, a cylindrical shape, and a pellet shape, and a plate shape or a honeycomb shape is usually applied.
When dust is contained in exhaust gas such as coal fired boilers, clogging and wear of the catalyst due to dust becomes a problem, but as a normal plate catalyst, as shown in FIG. There is known a catalyst structure in which catalyst elements 1 formed alternately in a row are stacked as shown in FIG. 8 (Patent Documents 1 and 2). Such a plate-like catalyst structure has a structure in which flat-plate catalyst elements are laminated, and thus is more resistant to end wear than other shapes, has excellent durability against clogging and wear, and has other shapes. It has the advantage that the pressure loss is lower than that. Further, in the case of a shape other than a plate shape, since the substrate and the carrier are not included inside, the strength of the catalyst itself must be maintained high, whereas the reaction efficiency of the catalyst may be sacrificed, In the case of a plate-like catalyst, the strength can be maintained by a substrate or a carrier, and the catalyst component on the catalyst surface has an advantage that the composition can maximize the reaction efficiency.

Japanese Patent Publication No.58-50137 Japanese Patent Laid-Open No. 11-347422

Conventionally, in a plate-like catalyst having a convex and concave row portion (hereinafter sometimes referred to as a peak portion) structure, the height h of the peak portion and the width w of the peak portion that are usually applied are substantially equal (w≈ h, w / h ≒ 1.0), because the flow velocity distribution is locally faster as shown in Fig. 10 (a) and (b), there is a possibility that the amount of process gas increases and the performance of the catalyst may not be maximized. There is. Further, when the distance (pitch) between adjacent catalyst elements is wide when stacked, and the peak portion is similar and large, gas may blow through the peak portion shown in FIG. 9 (a) depending on conditions.
An object of the present invention is for exhaust gas treatment capable of maximizing the catalyst performance by bringing the gas flow rate in the peak portion close to the gas flow rate of the flat plate portion, that is, by reducing the maximum gas flow rate in the flow path. It is to provide a catalyst and its structure.
In order to solve the above problems, the present inventors examined a conventional plate-like catalyst structure, and in the conventional catalyst structure shown in FIGS. 11 (a) and 11 (b), the height of the peak portion is high. Depending on the dimensions, there is a possibility that gas blow-through may occur in the portion indicated by (8) in FIG. 9 (a). Furthermore, in the shape of FIG. 10 (a), the phenomenon that the gas flow velocity of the mountain-shaped channel part, (8) of FIG. 9 (a) becomes higher than the channel between the flat plates was confirmed. It has been found that the processing gas flow rate per catalyst surface area in the flow path increases, and the catalyst performance may not be maximized.
As a result of various investigations on the dimensions of the above ridges, the present inventors have found that a fast flow velocity can be locally reduced within a certain appropriate range.

That is, the invention claimed in the present application is as follows.
(1) A plate-like catalyst body in which a catalyst component is supported on a plate-like body in which a plurality of rows of convex rows and concave rows (peaks) having a predetermined height are alternately formed in a flat plate portion, In each of the concave and convex crests installed on the flat plate portion, the mountain-shaped flow path formed by the end point γ that is the same flat plate position as the start point from the start point α from the flat plate portion via the apex β of the peak portion A plate-like catalyst for exhaust gas treatment, wherein the width w (width of the ridge) is less than the height of the ridge (w <h or w / h <1.0).
(2) The plate catalyst according to (1), wherein a ratio w / h between the width w of the peak and the height of the peak is in the range of 0.2 to 0.7.
(3) It is characterized in that a plurality of sheets are laminated so that the convex row portion and the concave row portion of the plate catalyst are in contact with the adjacent plate catalyst flat plate portion, and a gas flow path is formed between the plate catalysts. A catalyst structure for exhaust gas treatment using the plate catalyst according to (1) or (2).

  According to the present invention, it is possible to suppress the gas blow-through in the mountain-shaped flow path and to suppress the maximum gas flow rate corresponding to the blow-through, so that the performance of the catalyst can be maximized.

The explanatory view of the catalyst structure in Example 1 of the present invention. Explanatory drawing of the catalyst structure in Example 2 of this invention. Explanatory drawing of the catalyst structure in Example 3 of this invention. Explanatory drawing of the catalyst structure in the comparative example 1 of this invention. Explanatory drawing of the catalyst structure in the comparative example 2 of this invention. (a) Explanatory drawing of the catalyst structure in this invention. (b) Explanatory drawing which shows the detail of the peak part in this invention. Explanatory drawing of the catalyst body in this invention. Explanatory drawing of the catalyst structure in this invention. (a) Explanatory drawing of the flow path 8 of the conventional catalyst structure. (b) Explanatory drawing of the flow path 8 of the catalyst structure in the present invention. (a) The figure explaining the gas flow velocity measurement position 9 in the peak part of a plate-shaped catalyst. (b) The figure which shows the flow-velocity distribution in a peak part and a flat plate part. (a) The figure which shows the shape (mountain Z type) of the conventional plate-shaped catalyst. (b) The figure which shows the shape (mountain W type | mold) of the conventional plate-shaped catalyst. Explanatory drawing of a catalyst structure. The figure which shows the relationship between w / h and reaction rate in each Example and a comparative example. The figure which shows the relationship between w / h and the maximum gas flow velocity in each Example and a comparative example.

According to the present invention, by forming a catalyst structure in which the ridge width w of the ridge is less than the height h of the ridge (w / h <1.0), the local structure as shown in FIG. Since the gas blow-through can be suppressed and the gas flow rate in the mountain-shaped channel can be reduced, the performance of the catalyst can be maximized. This effect can be obtained not only in the structure having the Z-shaped peak in FIG. 11 (a) but also in the structure having the W-shaped peak in FIG. 11 (b).
Even if the width w of the peak portion is narrow, there is no problem in performance, and even when ash is deposited on the peak portion, it does not progress to other portions. However, when the ratio (w / h) of the peak height h to the peak width w does not reach 0.2, it is not practically desirable because the catalyst surfaces overlap and the effective surface area decreases. In addition, if the width w of the ridge is extremely narrow, the machining process of the ridge during manufacturing of the structure may increase as compared with the prior art, leading to an increase in cost. For this reason, the ratio (w / h) of the width w of the ridge portion to the height h of the ridge portion in the present invention is preferably less than 1.0, and practically in the range of 0.2 to 0.7.
Hereinafter, the present invention will be described in more detail with reference to examples.

The catalyst component is applied to stainless steel expanded metal, and then processed by pressing so that the height of the crest is 7 mm, and the catalyst gas flow direction length is cut to 500 mm and the width to 150 mm, as shown in Fig. 1. A catalyst body 1 was obtained. At this time, the ratio of the width w of the crest 2 to the crest width w was 0.2 (w = 1.4, h = 7), and the crests formed in the gas flow direction all have the same width. Thereafter, all 24 catalyst bodies 1 were stacked and assembled into a 150 mm square unit as shown in FIG.
As the catalyst component, a denitration catalyst having a composition ratio of Ti: W: V = 90: 5: 5 was used. Evaluation items were reaction rate and pressure loss, ash deposition, and gas flow rate. Among these, the reaction rate and the pressure loss were measured with a bench test apparatus using the conditions shown in Table 1. As shown in Table 2, the ash deposition was evaluated by disassembling the catalyst structure after passing gas containing ash for 24 hours. Furthermore, the heat transfer in the catalyst unit channel was simulated, and the heat transfer on the catalyst was assumed to be a NOx reaction, and the reaction rate and the maximum gas flow rate corresponding to the blow-through in the channel were evaluated. Table 3 shows the measurement conditions.
The measurement results obtained are the reaction rate ratio, the pressure loss ratio, the maximum gas flow rate, the gas when the ratio of the width w to the height h of the ridge is 1.0 (w / h = 1.0). Table 4 shows the situation of ash accumulation. Further, FIG. 13 shows the relationship between w / h and reaction rate in the catalyst flow path, and FIG. 14 shows the relationship between the maximum gas flow rate and w / h based on the simulation results.
According to the results of Example 1, it can be seen that the reaction rate is higher than that of the conventional catalyst body shown in Comparative Example 1, and the maximum gas flow rate corresponding to blow-through is reduced. This is presumably because the gas flow velocity became uniform by narrowing the width of the peak as shown in FIG. The pressure loss and ash accumulation were the same as those in Comparative Example 1.

After the catalyst component was applied to the expanded metal in the same manner as in Example 1, a catalyst body 1 was manufactured in which the width w of the crest 2 was processed wider than in Example 1 as shown in FIG. A simple catalyst structure was manufactured. At this time, the ratio of the peak width w to peak height h is 0.7 (w / h = 0.7, w = 4.9, h = 7), and the width w of the peaks formed in the gas flow direction is all the same. .
According to the result of Example 2, the gas flow velocity in the portion corresponding to the peak portion was lower than that in Comparative Example 1, and the reaction rate was slightly higher than that in Comparative Example 1. The pressure loss and ash accumulation were the same as in Comparative Example 1.

After applying the catalyst component to the expanded metal in the same manner as in Example 1, a catalyst body 1 having a width w of the ridge portion 2 processed narrower than in Example 1 as shown in FIG. 3 was manufactured and laminated, as shown in FIG. A simple catalyst structure was manufactured. At this time, the ratio of the peak height w to the peak height h is about 0 (w / h≈0, w≈0, h = 7), and the width w of the peaks formed in the gas flow direction is the same. did.
According to the result of Example 3, the maximum gas flow rate was lower than that of Comparative Example 1, and the reaction rate was higher than that of Comparative Example 1. On the other hand, the reaction rate ratio is slightly lower than that in Example 1, which is thought to be because the catalyst overlapped at the peak and the effective surface area decreased. The pressure loss and ash accumulation were the same as in Comparative Examples 1 and 2. In this example, since w / h≈0, the processing at the time of manufacturing the catalyst structure was more difficult than in the other examples, so the productivity was not so good.

[Comparative Example 1]
After applying the catalyst component to the expanded metal in the same manner as in Example 1, the width w of the crest 2 is equal to the crest height h (w / h = 1.0) as shown in FIG. The catalyst body 1 having the same width as that of the commonly used structure is manufactured, and then the catalyst structure body as shown in FIG. 12 is manufactured by stacking 24 sheets of the catalyst bodies 1. . This structure is the same as a commonly used structure.
In this example, the gas flow rate in the portion corresponding to the peak portion was higher than in each example, and the reaction rate was lower than in each example. The pressure loss and ash accumulation were the same as in Example 1 having a similar shape.
[Comparative Example 2]
After applying the catalyst component to the expanded metal in the same manner as in Example 1, the width w of the peak is 1.6 (w / h = 1.6) as shown in FIG. A catalyst body having the same width as that of a commonly used structure was manufactured, in which the widths of all formed peaks were the same. Thereafter, twelve of the catalyst bodies were laminated to produce a catalyst structure as shown in FIG.
In this example, the gas flow rate in the portion corresponding to the peak portion was higher than in each example, and the reaction rate was lower. The pressure loss and ash accumulation were the same as in Example 1 having a similar shape.

1. Catalytic body
2. Yamabe
3. Mountain width w
4. Mountain height h
5. Origin α from the flat plate in the mountain
6. Top of the mountain β
7. End point γ from the flat plate of the mountain
8. Corresponding part of gas blow-by
9. Gas flow velocity measurement position
10. Catalyst inlet gas flow rate
11. Catalyst outlet gas flow rate

Claims (3)

A plate-like catalyst body in which a catalyst component is supported on a plate-like body in which a plurality of rows of convex rows and concave rows (peaks) having a predetermined height are alternately formed in a flat plate portion, The width of the chevron of the mountain-shaped channel formed at the end point γ, which is the same flat plate position as the starting point, from the starting point α from the flat plate part through the apex β of the peak part in each concave and convex peak portion installed in A plate-like catalyst for exhaust gas treatment, wherein w (width of the ridge) is less than the height of the ridge (w <h or w / h <1.0). 2. The plate catalyst according to claim 1, wherein a ratio w / h between the width w of the peak and the height of the peak is in a range of 0.2 to 0.7. The plurality of sheets are laminated so that the convex row portion and the concave row portion of the plate catalyst are in contact with the adjacent plate catalyst flat plate portion, and a gas flow path is formed between the plate catalysts. A catalyst structure for exhaust gas treatment using the plate catalyst according to 1 or 2.

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