JP2001104801A - Catalyst structure for cleaning exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst structure by which increase of pressure drop can be avoided even when a planar catalyst body having a planar thick part at an end is used. SOLUTION: In the catalyst structure for cleaning exhaust gas in which plural sheets of planar catalyst bodies having plate thickness of an end part of a gas entrance side larger than plate thickness of other parts are laminated, the end part of the gas entrance side of the planar catalyst body 1 of alternate sheet is arranged at downstream side of a gas flowing direction 5 by a prescribed space from the end part of the gas entrance side of an adjacent planar catalyst body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst structure for purifying exhaust gas, and more particularly to a nitrogen oxide (hereinafter referred to as NO
x) is efficiently reduced with ammonia (NH ₃ ).

[0002]

2. Description of the Related Art N in exhaust gas discharged from power plants and the like
Ox is a causative substance such as acid rain. As an effective method for removing Ox, exhaust gas denitrification method of performing selective catalytic reduction using NH ₃ as a reducing agent using a catalyst has been widely used mainly in thermal power plants. I have. The above catalyst is usually used after being formed into a honeycomb shape or a plate shape, and various production methods have been proposed.

[0003] Among these, a base material obtained by processing a thin metal plate into a perforated mesh-like metal lath and then impregnating a plate-shaped base material or a woven or non-woven fabric made of ceramic fiber sprayed with aluminum with an inorganic solution such as titania or silica. Material for the substrate,
A plate-shaped catalyst obtained by applying or pressing the catalyst component to this,
After processing into a corrugated element, a large number of these are laminated to form a catalyst structure (JP-A-54-7918).
No. 8, JP-A-59-73053) have excellent features such as low ventilation loss and are hardly clogged with dust and combustion ash of coal, and are widely used for denitration equipment of boiler exhaust gas for thermal power plants at present. Have been.

Further, an unknown device proposed by the present inventor,
A catalyst structure in which a plate-like catalyst body and a flat woven fabric formed in a step-like or corrugated shape are alternately laminated has a processing gas and a catalyst which are disturbed by a gas flow passing through the openings of the woven fabric. The contact speed is greatly enhanced, the reaction speed is dramatically improved, and high performance is obtained, and the manufacturing process can be simplified.

[0005]

In recent years, efforts have been made in many fields to reduce the thickness of the catalyst to reduce the raw material cost and the ventilation loss in order to reduce the size of the exhaust gas denitration apparatus. Also in the field of exhaust gas denitration technology for coal-fired boilers, which used to use a catalyst structure with a large pitch between stacked catalysts at a low gas flow rate, etc. The demand for is growing.

When the thickness of the catalyst body is reduced by applying a reinforcing agent to the end on the gas inlet side in order to maintain the abrasion resistance due to the reduction in thickness of the catalyst body, or when a multifunctional catalyst is manufactured. For this reason, when the entire surface of the catalyst body is impregnated with a liquid containing a catalyst component, and the liquid does not permeate the catalyst body, the liquid attached to the catalyst body moves from top to bottom, and ends of the catalyst body It is unavoidable that a liquid pool portion is formed in the liquid and the thickness of the portion increases. FIG. 10 and FIG. 11 are explanatory views showing a catalyst structure in which a plate-like catalyst body whose one end is thicker than other portions is stacked.

FIG. 10 shows a catalyst structure in which a large number of plate-like catalyst bodies 1 each having a portion 6 whose one end is thicker than other portions (hereinafter, referred to as a plate thickness portion) 6 are stacked. FIG. 11 shows a catalyst structure in which plate-like catalyst bodies 1 having plate-thick portions 6 and net-like materials 2 are alternately stacked.

[0008] In such a conventional catalyst structure, since the catalyst body or both the catalyst body and the reticulated material have the same gas inlet side end positions, the thickness of all the ends is increased.
For this reason, when the lamination pitch is small, the passage porosity at the gas inlet portion is significantly reduced, and the increase in pressure loss due to the contraction of the gas inlet portion is not negligible. That is, in the conventional catalyst structure, even when the plate thickness of the end portion of the catalyst body is thicker than other portions, the end positions of all the catalyst bodies are aligned at the gas inlet end. For this reason, in the catalyst structure in which the end on the gas inlet side is stacked thicker than the other parts due to impregnation of the strengthening liquid or the like, the plate thickness is large at all the ends of the gas inlet. . For this reason, particularly when the pitch between the stacked catalysts is small, the porosity at the gas inlet is significantly reduced, and the increase in pressure loss due to the contraction of the gas at the inlet is too large to be ignored.

It is an object of the present invention to provide a catalyst structure which eliminates the above-mentioned problems of the prior art and which can avoid an increase in pressure loss even when a plate-like catalyst body having a thick portion at one end is used.

[0010]

The problem with the prior art described above is that the end of the catalyst body 1 or the mesh 2 on the gas inlet side is positioned closer to the thicker end of every other adjacent catalyst body. Can also be solved by installing and stacking them so as to be inside (downstream side in the gas flow direction).

That is, the invention claimed in the present application to achieve the above object is as follows. (1) In an exhaust gas purifying catalyst structure in which a plurality of plate-like catalyst bodies in which the plate thickness at the end on the gas inlet side is larger than the other parts are stacked, the gas inlet-side end of the plate-like catalyst body An exhaust gas purifying catalyst structure, wherein every other portion of the catalyst structure is disposed on the downstream side of the gas flow direction in a gas flow direction from a gas inlet side end of an adjacent plate-shaped catalyst body.

(2) The plate-shaped catalyst body A having a plate thickness at the end on the gas inlet side larger than the plate thickness at other portions, and a plate having a plate thickness at the end at the gas inlet side other than the other portions. In the exhaust gas purifying catalyst structure in which a plurality of plate-like catalysts B substantially equal to each other are alternately stacked, the gas inlet side end of the plate-like catalyst B is
An exhaust gas purifying catalyst structure, wherein the catalyst structure A is disposed on a downstream side in a gas flow direction by a predetermined distance from a gas inlet side end of the catalyst structure A.

(3) In (1) and (2), the predetermined distance is set such that the thickness of the catalyst structure from the gas inlet end to the gas inlet end is greater than the thickness of the other portions. A catalyst structure for purifying exhaust gas, wherein a distance from a thicker plate-shaped catalyst body to a terminal portion in a gas flow direction of the thicker portion is set.

(4) In (1) and (2), the end of the gas inlet side is located on the downstream side of the gas inlet end of the adjacent plate-shaped catalyst body in the gas flow direction. Exhaust gas, characterized in that the catalyst body is a catalyst body containing at least one of oxides of titanium oxide and vanadium, molybdenum and tungsten on a substrate made of a mesh made of inorganic fibers. Purification catalyst structure.

(5) The exhaust gas purifying apparatus according to (1) to (4), wherein the thick portion of the plate-shaped catalyst body is formed by supporting an inorganic compound. Catalyst structure. (6) The exhaust gas purifying catalyst structure according to (5), wherein the inorganic compound is supported by impregnation of a mixture of an inorganic oxide powder and an inorganic binder.

[0016]

Next, the present invention will be described in more detail by way of examples. In FIG. 1, a plate-like catalyst body 1 having a plate-thick portion 6 at the gas inlet end is laminated via a plate-like mesh 2 having no plate-thick portion, and the gas inlet side of the plate-like mesh 2 The end is arranged so as to be downstream of the end of the plate-shaped catalyst body by a length corresponding to the plate thickness portion 6 in the gas flow direction. FIG. 4 is a cross-sectional view of the flat net-like object 2 shown in FIG.
Is a catalyst structure using the catalyst body 1 having no plate thickness portion 6.

According to the present invention, the gas inlet side end of the catalyst body or net-like body without the plate thick portion 6 is more in the gas flow direction than the gas inlet side end of the plate catalyst body having the plate thick portion 6. By arranging and laminating them so as to be on the downstream side, it is possible to avoid an increase in pressure loss due to the contraction at the gas inlet.

In the present invention, with respect to the distance by which the end portion is shifted when the end portion is set on the downstream side in the gas flow direction, the stacked catalysts are supported via a support portion so that adjacent catalysts keep a predetermined interval. Therefore, every other layer has no support of the catalyst body, and the strength of the catalyst structure is reduced. Therefore, it is inappropriate to displace it too much inward. When the end of only the catalyst body whose end is located at the gas inlet end is thick, since the width of the end of the catalyst body when performing the end treatment is about 1 cm, the distance to shift the end is about 1 to 5 cm. Most effective. In addition, when both the end located at the gas inlet end and the end located downstream are thicker than the other parts, it is sufficient that both ends do not overlap. Most effective. However, in the present invention, the downstream end may be located more downstream than the thicker end of the catalyst located at the inlet end.
These distances are not particularly limited.

The catalyst used in the present invention, which is shaped like a flat plate, a step, or a corrugated plate, contains titanium oxide as a main component, vanadium (V), molybdenum (M
o), one obtained by adding one or more active components such as tungsten (W) is applied to an inorganic fiber woven fabric so as to fill the mesh, pressed, and then formed into various structures. It goes without saying that known means such as addition of an inorganic fiber or a binder can be used in combination to obtain the catalyst.

As a catalyst substrate, a stainless steel plate is processed into a porous network-shaped metal lath, and then a plate-shaped substrate sprayed with aluminum or a ceramic fiber, woven fabric or mesh material is coated on the surface in an oxidizing atmosphere. An inorganic fiber substrate reinforced by impregnating with an inorganic solution containing titania or silica is used, but is not particularly limited.

The components of the inorganic compound used in the gas inlet end strengthening treatment include a mixture of α-aluminum oxide fine powder and aluminum phosphate, a mixture of cordierite and sodium silicate, and a mixture of catalyst powder and silica sol.
A mixture of an inorganic oxide powder and an inorganic binder is suitable, but is not particularly limited in the present invention.

Further, the reinforcing material or a catalyst component may be supported on the mesh. Also, for the material of the mesh,
Although there are ceramics and glass, there is no particular limitation in the present invention.

In the catalyst structure of the present invention, the position of the end of the catalyst body is shifted every other sheet on the gas inlet side. The opening ratio does not decrease so much as compared with the case where the thickness of the portions other than the end portions is equal, and the increase in pressure loss due to the contraction can be reduced.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. Example 1 A stainless steel thin plate having a thickness of 0.3 mm was processed into a metal mesh having a porous mesh shape, and aluminum was sprayed on the surface in an oxidizing atmosphere to prepare a plate-shaped metal base material, which was used for producing a plate-shaped catalyst. A substrate was used.

On the other hand, 1.2 kg of titanium oxide having a specific surface area of 270 m ² / g was added to ammonium molybdate ((NH ₄ ) ₆ .Mo.
₇ O ₂₄ · 4H ₂ O) and 0.25 kg, ammonium metavanadate 0.23 kg, and oxalic 0.3 kg, further 20
8% by weight of silica sol as SiO ₂ was added, and the mixture was kneaded while adding water to form a paste. 15% by weight of kaolin-based inorganic fiber (trade name: kao wool) was added, and the mixture was further kneaded to obtain a paste having a moisture of 30.5%. Obtained.

520 mm width prepared from the above paste
It was placed between two plate-shaped catalyst-producing substrates, fed between a pair of rolling rollers, rolled with rollers, and the paste was spread on both substrate surfaces and applied to the mesh space and the mesh surface. Thereafter, the resultant was cut into a length of 500 mm to obtain a plate-shaped catalyst body having a thickness of 0.5 mm. The obtained catalyst body was formed by being sandwiched between heating molds having a predetermined shape, and dried to form a step-shaped catalyst body as shown in FIG. At this time, the height h in FIG.
It was 91 mm.

On the other hand, E glass fiber 14 having a fiber diameter of 9 μm
A woven cloth obtained by plain weaving a twisted yarn obtained by twisting 00 pieces into one piece with a roughness of 10 pieces / 25.4 mm, titania 40%, silica sol 2
0%, 1% polyvinyl alcohol slurry impregnated with
It was dried at 50 ° C. to give rigidity and cut into 500 mm square to obtain a net-like material.

Further, 1.2 kg of titanium oxide having a specific surface area of about 270 m ² / g was added to ammonium molybdate ((NH ₄ ) ₆ .Mo.
The _{7 O 24 · 4H 2 O)} 0.25kg, ammonium metavanadate 0.23 kg, and containing added oxalic acid 0.3 kg, yet extrusion granulator after the clay-like material was kneaded by adding water It was formed into a 3φ column shape. After drying the compact, 5
After firing at 50 ° C for 2 hours, pulverize with a fine pulverizer
A catalyst powder having the following particles of 60% or more was obtained. Further, water was added to this powder to prepare a catalyst slurry having a solid content of 40%. This catalyst slurry is impregnated with the entire reinforced mesh, and air is blown at room temperature to open the openings of the mesh other than the portion where the catalyst paste is applied, and then dried at 350 ° C. to form a mesh having a thickness of 0.65 mm. I got something.

Each of the obtained catalyst and the reticulated material was 500 mm wide × 500 mm long in the upstream and downstream directions and 500 mm wide.
× cut into 450mm length in the upstream and downstream direction, width of the net 50
One end of 0 mm is aligned with one end position in the width direction of the catalyst body, and the other end is 50 mm away from the front end of the catalyst body.
mm on the downstream side and alternately laminated, and the side with different end positions is the gas inlet side and the inner dimension is 500 mm x
It was assembled in a 500 mm metal frame. This was calcined at 500 ° C. for 2 hours with ventilation to obtain a catalyst structure having the shape shown in FIG.

Next, a fine powder of α-alumina and aluminum phosphate were mixed at a weight ratio of 20% and 10%, respectively, to prepare a slurry, and the catalyst structure was added to the liquid by shifting the mesh to the downstream side. The catalyst body 1 was immersed at about 2 cm from the inlet end to strengthen only the end of the catalyst body 1, and calcined at 350 ° C. for 2 hours to obtain a catalyst structure as shown in FIG.

Comparative Example 1 The size of the mesh used in Example 1 was 500 mm × 500.
mm, a catalyst structure was prepared in the same manner as in Example 1 except that both ends were aligned with the end of the catalyst body.
It was assembled in a metal frame, and both ends of the gas inlet were reinforced with a reinforcing liquid to obtain a catalyst structure as shown in FIG.

Example 2 The end of the catalyst body of Example 1 was applied to the slurry of Example 1 by about 2 cm.
Soaked. On the other hand, one side of the mesh of Example 1 in the 500 mm width direction was similarly immersed in the slurry of Example 1 by about 2 cm. These were fired at 350 ° C. for 2 hours. The catalyst body and the mesh obtained in this manner, the end position of the slurry impregnated with the mesh in the width direction of 500 mm is placed 50 mm downstream of the end position of the catalyst body impregnated with the slurry and stacked alternately, Inner dimensions 5
The catalyst structure as shown in FIG. 2 was obtained by assembling in a metal frame of 00 mm × 500 mm.

Example 3 Titanium oxide powder (TiO ₂ ), ammonium metatungstate ((NH ₄ ) ₆ [H ₂ W ₁₂ O ₄₀ ]), and ammonium metavanadate (NH ₄ [VO ₃ ]) were mixed with Ti / W / V molar ratio 89
After weighing so as to obtain / 5/6, 30 wt% of water was added to the titanium oxide, and kneading was performed with a kneader for 30 minutes. Thereafter, 25 wt% of kao wool was added to the raw material titanium oxide, and then 30 wt. The mixture was kneaded for a minute to obtain a paste having a water content of 31%.

The above paste was prepared in Example 1 with a width of 50.
Placed between two 0 mm substrates, as in Example 1,
After applying between the mesh and the mesh surface with a pair of rolling rollers,
The plate was cut into a length of 480 mm and a length of 450 mm in the gas flow direction to obtain two kinds of plate-shaped catalyst bodies having different thicknesses of 0.5 mm. This catalyst was press-molded and cut into a width of 480 mm to obtain a corrugated plate-shaped catalyst body.

The two types of catalysts were alternately stacked with one end in the gas flow direction aligned to obtain a catalyst structure as shown in FIG. Next, into a mixture of cordierite and sodium silicate at a weight ratio of 30% and 10% respectively,
The entire catalyst structure was impregnated, air-dried for 3 hours with the side where the ends were not aligned downward, and then calcined at 350 ° C. for 2 hours to obtain a catalyst structure as shown in FIG.

Example 4 The two types of plate-like catalysts obtained in Example 3 were sandwiched between step-type heating dies and dried to form molded catalysts. The catalyst structures having the structure shown in FIG. 7 were obtained by alternately laminating one end position in the direction.

Then, the catalyst structure and the silica sol were mixed at a weight ratio of 25% and 20%, respectively, in the liquid used in Example 1, and the catalyst structure was immersed at about 2 cm at the different end positions so that the ends were changed. Only the end of the catalyst body located outside was impregnated and calcined at 350 ° C. for 2 hours to obtain a catalyst structure as shown in FIG.

With respect to Example 1, Example 2, and Comparative Example 1, the pressure loss was measured under the conditions shown in Table 1. FIG. 9 shows the obtained results.
It was shown to. In FIG. 9, the pressure loss ratio is a value obtained by dividing the obtained pressure loss by the pressure loss of Comparative Example 1.

[0039]

[Table 1]

As shown in FIG. 9, a comparative example 1 in which a large number of plate-like catalyst bodies having a large thickness at the end and a net-like material having a large thickness at the end were laminated so that the positions of the ends were the same. As compared with the pressure loss of the catalyst structure of Example 1, the pressure loss of the catalyst structures of Examples 1 and 2 was about 80%. From this, it is understood that the catalyst structure of the present invention was able to reduce the increase in pressure loss as compared with a catalyst body in which all the positions of the ends of the catalyst body were aligned.

[0041]

According to the present invention, when the end face or the entire surface of the catalyst body is impregnated with a reinforcing liquid or the like, especially when the pitch of the lamination is small, the inlet caused by the increase in the plate thickness due to the liquid pool portion inevitably generated. A large decrease in the porosity of the portion can be suppressed. As a result, it is possible to suppress an increase in pressure loss due to the contraction at the gas inlet.

[Brief description of the drawings]

FIG. 1 is a diagram showing the shape and configuration of a catalyst structure according to a first embodiment of the present invention.

FIG. 2 is a view showing a shape and a configuration of a catalyst structure according to a second embodiment of the present invention.

FIG. 3 is a view showing a shape and a configuration of a catalyst structure according to a third embodiment of the present invention.

FIG. 4 is a view showing the shape and configuration of a catalyst structure according to Example 4 of the present invention.

FIG. 5 is a diagram showing an example of the shape and configuration of a catalyst structure in which the end positions of catalyst bodies or meshes are shifted to the gas downstream side every other sheet.

FIG. 6 is a diagram showing an example of the shape and configuration of a catalyst structure in which the end positions of catalyst bodies or meshes are shifted to the gas downstream side every other sheet.

FIG. 7 is a diagram showing an example of the shape and configuration of a catalyst structure in which the end positions of catalyst bodies or meshes are shifted to the gas downstream side every other sheet.

FIG. 8 is a diagram showing one of the factors representing the shape of the step catalyst body.

FIG. 9 is a view showing a result of comparison between pressure loss of a catalyst structure of the present invention and pressure loss of a conventional catalyst structure.

FIG. 10 is a view showing the shape and configuration of a conventional catalyst structure.

FIG. 11 is a view showing the shape and configuration of a conventional catalyst structure.

[Explanation of symbols]

Reference numeral 1 denotes a step-like or corrugated catalyst body (catalyst body); 2 a flat plate-like mesh; 5 a gas flow;

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Yokoyama 3-36 Takara-cho, Kure-shi, Hiroshima F-term in Babcock Hitachi, Ltd. Kure Research Laboratories 4D048 AA06 AB02 AC04 BA03Y BA06Y BA07X BA07Y BA23X BA23Y BA26X BA26Y BA27X BA27Y BA39X BA39Y BB04 BB07 CC31 4G069 AA03 AA08 BA02B BA04A BA04B BA17 BB02A BB02B BC16B BC50A BC50B BC54A BC54B BC59A BC59B BC60A BC60B CA02 CA08 CA13 EA12 EA20 EA22 EA27 FA04 FA05 FA06 FB15

Claims (6)

[Claims] 1. An exhaust gas purifying catalyst structure in which a plurality of plate-like catalyst bodies having a plate thickness at an end portion on a gas inlet side larger than other plate thicknesses are stacked, wherein a gas inlet of the plate-like catalyst body is provided. An exhaust gas purifying catalyst structure, wherein the side end portions are arranged so as to be on the downstream side in the gas flow direction by a predetermined distance from the gas inlet side end portions of adjacent plate-shaped catalyst bodies. . 2. A plate-like catalyst body A having a plate thickness at an end on the gas inlet side larger than a plate thickness at other portions, and a plate having a plate thickness at an end portion on the gas inlet side other than the plate thickness at other portions. In the exhaust gas purifying catalyst structure in which a plurality of substantially equal plate-shaped catalyst bodies B are alternately stacked, the gas inlet side end of the plate-shaped catalyst body B is closer to the gas inlet side end of the catalyst structure A. A catalyst structure for purifying exhaust gas, wherein the catalyst structure is disposed so as to be downstream of a gas flow direction by a predetermined distance. 3. The plate according to claim 1, wherein the thickness of the catalyst structure at the gas inlet side end from the gas inlet side tip is larger than the thickness of the other portion. A catalyst structure for purifying exhaust gas, characterized in that it is a distance to a gas flow direction end portion of the thick part of the tubular catalyst body. 4. The plate-like catalyst body according to claim 1, wherein the end position on the gas inlet side is located on the downstream side of the gas inlet side of the adjacent plate-like catalyst body in the gas flow direction. Is a catalyst for exhaust gas purification, characterized in that a base material made of an inorganic fiber mesh is loaded with a catalyst component containing at least one of titanium oxide and each oxide of vanadium, molybdenum and tungsten. Structure. 5. The exhaust gas purifying catalyst structure according to claim 1, wherein the thick portion of the plate-shaped catalyst body is formed by supporting an inorganic compound. . 6. The exhaust gas purifying catalyst structure according to claim 5, wherein the inorganic compound is supported by impregnation of a mixture of an inorganic oxide powder and an inorganic binder.