JPH11319583A - Plate-like catalyst element and catalyst structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst element and a catalyst structure which ensure a prescribed strengh by making the catalyst element into a thin sheet and eliminating anisotropy of bending strength of a catalyst structure prepd. by laminating the catalyst elements. SOLUTION: A plate-like catalyst element 1a with a number of step-like step differences wherein plate parts 2 and step defference parts 3 are alternately provided by bending a plate-like catalyst prepd. by coating a woven fabric of an inorg. fiber with a catalyst paste is provided and the woven fabric of the inorg. fiber consists of a sheet of the woven fabric of the inorg. fiber and when the curvature radius of a bent part where the catalyst paste coated face of the woven fabric of this inorg. fiber is projected is rA and the curvature radius of the bent part where it is recessed is rB, the relation of rA and rB is rA>rB and when the step difference of flat plate part before and after the bent part is d, the relation between this step difference d and the curvature radius rA is rA<=d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-like catalyst element and a catalyst structure, and more particularly to a plate-like catalyst element produced by rolling and applying a catalyst paste on an inorganic fiber base material, and a catalyst structure obtained by laminating the same. TECHNICAL FIELD The present invention relates to a plate-shaped catalyst element and a catalyst structure, which have a small ventilation pressure loss, hardly accumulate dust in exhaust gas, and can downsize the entire catalyst device.

[0002]

2. Description of the Related Art As a catalyst for exhaust gas treatment, for example, a selective catalytic reduction denitration method using ammonia (NH ₃ ) as a reducing agent, a honeycomb-shaped or plate-shaped catalyst is known, for example. . Among them, plate-like catalysts (for example, JP-A-54-79188, JP-A-59-730)
No. 53, etc.) have the characteristic that the ventilation pressure loss is small and the accumulation of ash and dust (hereinafter, referred to as dust) generated from the combustion device is small. In recent years, the catalyst device has been downsized. Accordingly, a reduction in the thickness of the catalyst plate and a reduction in the pitch between the catalysts are required.

[0003] In order to respond to such a demand,
The shape of the catalyst element has a stepped cross section, and the accumulation of dust is suppressed by minimizing the corners where the gas flow rate is low in the catalyst stack (hereinafter referred to as the catalyst structure), thereby reducing the thickness of the catalyst. It is conceivable to employ an unknown technique of the present inventor that attempts to make the pitch narrower. FIG. 6 shows a catalyst structure in which catalyst elements 7 having such a stepwise cross section are stacked and housed in a catalyst frame 8.

However, even with such a catalyst structure, it is difficult to use a conventional plate-like catalyst element which is rolled with two inorganic fiber woven fabrics as a base material and a catalyst paste interposed therebetween. However, there is naturally a limit in reducing the thickness of the catalyst, and it is not possible to sufficiently respond to recent demands for downsizing the catalyst device. On the other hand, in the case of a plate-shaped catalyst obtained by rolling the catalyst paste on one inorganic fiber woven fabric, the thinning becomes easier as compared with a catalyst using two woven fabrics,
There is a difference in properties, that is, bending strength, between the surface on which the catalyst paste is applied and the back surface, which causes a problem that the bending strength in a specific direction is significantly reduced. FIG. 7 is an explanatory diagram of a case where a load is applied to a plate-shaped catalyst obtained by rolling and applying a catalyst paste on one inorganic fiber woven fabric. In FIG. 7, the catalyst-coated surface (the surface where the inorganic fiber woven fabric 5 is covered with the catalyst component 9)
When a load is applied to the catalyst (a) and when a load is applied to the back surface (the surface where the woven fabric 5 is exposed) (b), the catalyst-coated surface is convex in order to curve the catalyst in the same manner. (B) requires less load, ie, the bending strength when the catalyst-coated surface is bent so as to be convex is such that the catalyst-coated surface is bent so as to be concave. It can be seen that the bending strength is smaller than the case. Therefore, when a large number of such catalyst elements are stacked in the same direction to form a catalyst structure, there is a problem that the bending strength of the catalyst structure in a specific direction is weakened.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to make the catalyst element as thin as possible, and to eliminate the anisotropy in bending strength of the catalyst structure in which the catalyst element is laminated. To provide a plate-shaped catalyst element and a catalyst structure.

[0006]

Means for Solving the Problems To achieve the above object, the invention claimed in the present application is as follows. (1) A plate-like catalyst element having a large number of step-like steps, wherein a plate-like catalyst obtained by applying a catalyst paste to an inorganic fiber woven fabric is provided alternately with a flat plate portion and a step portion, The cloth is made of one inorganic fiber woven cloth, and the radius of curvature of the bent part where the catalyst paste application surface of the inorganic fiber woven cloth is convex is r _A , and the radius of curvature of the bent part where the concave part is concave is r.
_{When B} , the relationship between r _A and r _B is r _A > r _B , and when the step between the flat plate portions before and after the bent portion (hereinafter referred to as pitch) is d, the curvature radius r _A plate-shaped catalyst element, wherein the relationship between _A and the step d is r _A ≦ d.

(2) The plate-shaped plate according to (1), wherein the bending angle of the bent portion where the catalyst paste application surface is convex and the bent portion where the catalyst paste application surface is concave are 90 ° ± 10 °, respectively. Catalyst element. (3) A catalyst structure, wherein a large number of the plate-like catalyst elements according to the above (1) or (2) are stacked such that the front and back surfaces of adjacent catalyst elements are reversed.

In the present invention, in order to make the catalyst element thinner, a catalyst paste is rolled and applied to one inorganic fiber woven fabric to form a plate catalyst, and the plate catalyst is bent to form a flat plate portion. Stepped portions are alternately provided to form a plate-shaped catalyst element having many stepped steps. In such a plate-shaped catalyst in which the catalyst paste is applied to one piece of inorganic fiber woven fabric, the catalyst application surface (the surface where the inorganic fiber woven fabric is covered with the catalyst)
Then, a difference in bending strength occurs between the opposite side and the surface on which the inorganic fiber woven fabric is exposed, so that the radius of curvature of the bent portion when the step-like step is provided is defined. That is, in the present invention, the radius of curvature r _{A of the} bent portion where the catalyst-coated surface is convex.
And the relationship between the radius of curvature r _B of the concave bent portion and r
And _A> r _B. Further, when a step-like step, that is, a step (pitch) between the flat plate portions before and after the bent portion is d, the relationship between the step d and the radius of curvature r _A of the bent portion where the catalyst-coated surface becomes convex is represented by Let r _A ≦ d. As a result, a plate-like catalyst element having many step-like steps can be obtained without causing cracks on the catalyst surface.

The principle of the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory diagram showing a situation in which the outside of a convex bent portion extends when the plate-shaped catalyst 1 is bent.
In FIG. 1, the length of the outside (outer circumference) of the bent portion is L ₁
In this case, L ₁ is represented by 2π (r + dr) / 4.
On the other hand, if the original length is L ₀ , L ₀ is 2π (r +
dr / 2) / 4.

Therefore, the extension width of the outer periphery of the bent portion is L
₁₋ L ₀ = πdr / 4, and the elongation is (L ₁ −L ₀ ) / L ₀ = (πdr / 4) / [2π (r +
dr / 2) / 4] = dr / (2r + dr) = 1 / (2r
/ Dr + 1), and when dr≪r, (L ₁ −L ₀ ) / L ₀ ≒ dr
/ 2r.

That is, the elongation rate of the outer circumference is proportional to a value obtained by dividing the thickness dr of the plate catalyst by the radius of curvature r. Therefore, when the thickness of the catalyst is constant, the smaller the radius of curvature r, the larger the extension of the outer periphery of the bent portion, and the larger the radius of curvature of the bent portion, the larger the extension of the outer periphery of the bent portion. It is possible to prevent the strength from being reduced due to cracks in the bent portion.

In the present invention, the plate-shaped catalyst in which the catalyst paste is applied to one inorganic fiber woven fabric has a low bending strength, particularly at a portion where the catalyst-coated surface is bent so as to be convex. If the radius of curvature of the bent portion is increased, the occurrence of cracks can be prevented and the shape retention can be ensured. On the other hand, at the portion where the surface (back surface) where the inorganic fiber woven fabric is partially exposed is bent so as to be convex, the fiber is on the convex surface side, so that even if the radius of curvature is small, no cracks are formed and the fiber is maintained. There is no deterioration in shape. It is preferable that the radius of curvature is large even in the bent portion where the back surface is convex, but if the pitch d of the catalyst is to be kept constant, the catalyst coated surface is bent so as to be convex as described above. Since it is necessary to increase the radius of curvature of the portion, it is necessary to relatively reduce the radius of curvature of the portion bent so that the back surface becomes convex. In the present invention, therefore, r _A> r the relationship between the curvature radius r _B of the radius of curvature r _A and bent portion in the concave bent portion of the catalyst coated surface in a convex shape (a portion bent back surface in a convex shape) _B.

FIG. 2 is a diagram showing the relationship between the radius of curvature r, the pitch d and the bending angle when the plate catalyst 1 is bent. In FIG. 2, the radius of curvature r of the portion A where the catalyst is bent in a convex shape must be equal to or smaller than the interval between the flat plate portions 2 before and after bending, that is, the pitch d of the plate-shaped catalyst. In the above, the relationship between the radius of curvature r _A of the portion where the catalyst application surface is bent in a convex shape, which is the largest radius of curvature, and the pitch d is r _A ≦ d.

FIG. 3 is an explanatory view showing the relationship between the bending angle of the catalyst in the plate-shaped catalyst 1 and the acting direction of the stress when a load is applied to the bent portion. In the figure,
When the bending angle deviates from 90 °, as shown in FIG. 3B, the vertical stress (==
Load) acts in the direction of reducing the catalyst pitch d, that is, the direction in which the catalyst is deformed, so that the dimensional accuracy of the catalyst in the width direction is reduced. In order to avoid such inconvenience, as shown in FIG.
° must be as close as possible. In the present invention, the bending angle is set to 90 ° ± 1 in order to make the stress for deforming the catalyst sufficiently smaller than the stress in the vertical direction.
0 °, more preferably 90 ° ± 5 °. If the bending angle is in the range of 90 ° ± 10 °, a plate-like catalyst can be manufactured with the same dimensional accuracy as the conventional one.

In the present invention, when the catalyst elements having stepped steps are stacked to form a unit, it is preferable to stack the catalyst elements adjacent to each other so that the front and back of the catalyst are reversed. This is because, when all the catalysts are arranged in the same direction, the catalyst structure has a characteristic that the catalyst structure has a strong bending strength with respect to a load in a specific direction, but has a weak property with respect to a load in the opposite direction. Also,
In the present invention, in order to make the gas flow path cross section in the catalyst structure uniform, for example, it is preferable that the ends of the respective elements are laminated while being slightly shifted.

In the present invention, if the value obtained by dividing the thickness of the catalyst by the radius of curvature (dr / r) is constant, the bending strength of the plate-like catalyst can be reduced even if the pitch of the catalyst is reduced by reducing the thickness of the catalyst. The size of the catalyst device can be reduced without lowering the size. In the present invention, as the inorganic fiber woven fabric, for example, a glass fiber woven fabric is used, and as the shape thereof, for example, a wire mesh is used, but the shape is not particularly limited to this.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 A net-like material (500 mm width) in which 800 twisted yarns of E glass fibers having a fiber diameter of 6 μm are entangled with a roughness of 2.5 mm between fiber bundles.
× length 360 m, thickness 0.25 mm) was impregnated with a reinforcing solution obtained by mixing silica sol (silica content: 20% by weight), titania and polyvinyl alcohol in a weight ratio of 50: 50: 1, and then impregnated at 150 ° C. It was strengthened by drying for a time to obtain a catalyst substrate.

On the other hand, titania powder (specific surface area of about 100 m
² / g), ammonium molybdate and ammonium metavanadate were weighed so that Ti / Mo / V = 93/5/2, 60% by weight of water was added to the titania powder, and the mixture was kneaded with a kneader for 30 minutes. After that, silica alumina fibers having a fiber diameter of 2.8 μm were simultaneously added at a ratio of 15% by weight to the titania powder as a raw material, and kneaded for further 30 minutes to obtain a catalyst paste.

The obtained catalyst paste 6 is applied to the previously prepared inorganic fiber woven fabric 5 using a pair of catalyst application rollers 4 as shown in FIG.
Rolled and coated so that the width becomes 2
5 mm, pitch 3 mm, the radius of curvature of the bent portion 3 where the catalyst application surface is bent in a convex shape is 2 mm, the radius of curvature of the bent portion bent so that the back surface is convex is 0.3 mm, and the bending angles are respectively A catalyst element was formed by forming the catalyst element at a right angle. As shown in FIG. 5, a large number of the obtained catalyst elements 1a are laminated and unitized so that the front and back sides are opposite to each other between adjacent elements and are sequentially shifted by 5 mm from one end. 500 ℃
For 2 hours to obtain a catalyst structure.

Example 2 A catalyst element was prepared under the same conditions as in Example 1 except that the bending angle of each bent portion in the catalyst element was set to 100 °, and the catalyst element was similarly unitized to obtain a catalyst structure. Comparative Example 1 A catalyst element was prepared in the same manner as in Example 1 except that the bending angle of each bent portion in the catalyst element was set to 60 °.

Comparative Example 2 A catalyst element was prepared in the same manner as in Example 1 except that the bending angle of each bent portion in the catalyst element was set to 120 °, and a catalyst structure was obtained by unitizing in the same manner. Comparative Example 3 The radius of curvature of the portion where the catalyst application surface was bent in a convex shape was 0.3.
mm, the radius of curvature of the part where the back surface is bent in a convex shape is 2 mm
A catalyst element was prepared under the same conditions as in Example 1 except for the above, and was similarly unitized to obtain a catalyst structure.

Comparison of whether the catalyst structures obtained in Examples 1 and 2 and Comparative Examples 1 to 3 can be made into a unit was made by visual observation of the laminated state. In Comparative Examples 1, 2 and 3, The bent part is crushed,
Although a gap was formed in the upper part of the catalyst unit, such a gap was not found at all in the catalysts of Examples 1 and 2, and no collapse of the bent portion in the catalyst element was observed.

[0023]

According to the first aspect of the present invention, 1
In a catalyst element in which a plate-shaped catalyst in which a catalyst paste is applied to a sheet of inorganic fiber woven fabric and a flat plate portion and a step portion are alternately provided, the radius of curvature of the bent portion where the catalyst application surface becomes convex is r _A , the concave radius is If the composed bent portion the radius of curvature of the set to r _B, if the relationship of r _a and r _B and r _a> r _B, and the flat plate portion mutual level difference before and after the bent portion is d, and r _a By setting the relationship of d to r _A ≦ d,
Since a plate-like catalyst element that is thinner and has a smaller pitch than before can be easily manufactured without lowering the bending strength, it is possible to sufficiently cope with a demand for downsizing the catalyst device. In addition, since the number of the inorganic fiber woven fabric is one, the amount of raw materials used and the amount of waste generated when the same number is manufactured can be reduced, so that an increase in manufacturing cost can be suppressed.

According to the second aspect of the present invention, the bending angle of each of the bent portion where the catalyst-coated surface is convex and the bent portion where the catalyst-coated surface is concave is 90 ° ± 10 °. In addition to the effects described above, deformation when the catalysts are stacked is prevented, and the dimensional accuracy in the width direction is improved. According to the invention of claim 3 of the present application, the catalyst element is
By forming a large number of stacked catalyst elements so that the front surface and the back surface of the adjacent catalyst elements are opposite to each other, the bending strength of the catalyst structure with respect to the load in each direction can be made uniform.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is an explanatory diagram illustrating the principle of the present invention.

FIG. 4 is an explanatory view showing a method of applying a catalyst paste to a woven inorganic fiber fabric.

FIG. 5 is a view showing a part of a catalyst structure according to one embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a cross-sectional structure of a prior art catalyst structure.

FIG. 7 is an explanatory diagram showing the bending strength of a catalyst element obtained by applying a catalyst paste to one inorganic fiber woven fabric.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plate catalyst, 1a ... Catalyst element, 2 ... Flat plate part, 3
... Bending part, 4 ... Application roller, 5 ... Inorganic fiber woven cloth, 6
... catalyst paste, 7 ... catalyst element, 8 ... catalyst frame, 9
... catalyst component.

Claims (3)

[Claims] 1. A plate-like catalyst element having a large number of step-like steps, wherein a plate-like catalyst obtained by applying a catalyst paste to an inorganic fiber woven fabric is bent to provide alternately flat plate portions and step-like portions. The fiber woven fabric is made of one inorganic fiber woven fabric, and the radius of curvature of the bent portion where the catalyst paste application surface of the inorganic fiber woven fabric is convex is r _A , and the radius of curvature of the bent portion where the concave portion is concave is r _B When the relationship between r _A and r _B is r _A > r _B and the step between the flat plate portions before and after the bent portion is d, the relationship between the curvature radius r _A and the step d is _A plate-like catalyst element, wherein r _A ≦ d. 2. The bending angle of each of the bent portion where the catalyst paste application surface is convex and the bent portion where the catalyst paste application surface is concave is 90 ° ± 10 °.
A plate-like catalyst element according to item 1. 3. A catalyst structure, wherein a large number of the catalyst elements according to claim 1 or 2 are stacked such that the front and back surfaces of adjacent catalyst elements are reversed.