JPH08117607A - Platelike catalyst for denitrifying exhaust gas and its production - Google Patents

Abstract

PURPOSE: To provide the catalyst which has improved wear-resistant strength with respect to dust and shows a controlled degree of deterioration in catalytic performance below a low level and a low degree of SO2 oxidation. CONSTITUTION: In this production, an inorganic fiber 2 such as glass fiber contg. a calcium component, etc., and water are added to a catalyst composition 1 consisting of titanium and at least another catalyst component such as molybdenum, vanadium, tungsten, etc., and the resulting mixture is kneaded by a kneader 3 to produce a catalyst composition paste 4. Then, the surface of a lath sheet 5 fabricated from a thin metal sheet is coated with this paste 4 by using coating rolls 6 and the coated lath sheet 5 is formed into a platelike catalyst 8 having a prescribed shape by using a molding machine 9 and thereafter, the platelike catalyst 8 is dried and then calcined at 450 to 550 deg.C and subsequently, impregnated with a liquid 11 contg. a sulfuric acid component. Thereafter, the resulting impregnated platelike catalyst 8 is dried and then calcined at 350 deg.C to produce the objective platelike catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas denitration plate catalyst and a method for producing the same, and more particularly to a metal substrate, particularly a metal lath (a thin metal plate in a zigzag arrangement with a predetermined pitch and a predetermined length (for example, 3 to 10 mm)). And a plate-shaped catalyst in which a catalyst composition is supported on a mesh-shaped metal thin plate formed by applying tensile force to the thin plate in a direction perpendicular to the cut, and a plate catalyst for denitration with enhanced wear resistance and a method for producing the same. Regarding

[0002]

2. Description of the Related Art As a method for removing nitrogen oxides in exhaust gas, a method in which a catalyst is selectively reduced with ammonia is the mainstream, and these denitration catalysts are generally titanium oxide (TiO ₂ ). A catalyst composition made of an oxide such as molybdenum (Mo), vanadium (V), or tungsten (W) is formed into a granular shape, a plate shape, a honeycomb shape, or the like. Above all, in the case of boiler exhaust gas that uses heavy oil or coal as a fuel, it is necessary to treat a gas containing a large amount of soot dust and ash with a low pressure loss, and a combination of plate catalysts (for example, Japanese Patent Publication No. 61- No. 28377) and a honeycomb catalyst having a large opening ratio, etc., having a passage parallel to the gas flow direction (Japanese Patent Publication No. 60-3856).

In order to secure the structural strength of these catalysts, inorganic fibers are added to the catalyst composition for strengthening, but the wear resistance of the catalyst is particularly high in the case of a boiler containing a large amount of dust in the exhaust gas. Therefore, there has been proposed a method of adding an inorganic binder such as silica sol to increase the strength (for example, JP-A-55-155740).

[0004]

In the case of strengthening the catalyst with the above-mentioned inorganic binder, the binder closes the pores of the catalyst to increase the density and improve the wear resistance, which causes the diffusion of the reaction gas in the catalyst. Therefore, there is a problem that the denitration performance is impaired due to the inhibition of the denitrification, or the component becomes a catalyst poison depending on the type of the inorganic binder, and the denitration rate decreases.

Taking these things into consideration, a certain degree of denitrification
In order to satisfy the
In anticipation of a decrease in the denitrification rate caused by
Easy to increase the amount of metal active component in the catalyst composition
It can be considered as a means to treat exhaust gas containing SOx
In the case of, SO₂SO₃Oxidation rate (hereinafter, SO ₂
Ammonia, which is a reducing agent,
Reacts with ammonium sulfate to produce ammonium sulphate easily
There is a risk of damage to the equipment on the flow side.

The object of the present invention is to eliminate the above-mentioned problems of the prior art, to improve the wear resistance strength against dust in exhaust gas, and to suppress the deterioration of the denitration performance due to it, resulting in the SO ₂ oxidation rate. The object is to provide a plate catalyst for exhaust gas denitration with low exhaust gas and a method for producing the same.

[0007]

In order to achieve the above object, the invention claimed in the present application is as follows. (1) In a plate catalyst for exhaust gas denitration, which is formed by coating a paste-like material made of a catalyst composition on the surface of a substrate obtained by lathing a thin metal plate, and processing the paste into a predetermined plate shape, calcium (Ca) is contained in the catalyst composition. Inorganic fibers containing components are interposed,
A plate catalyst for exhaust gas denitration, wherein the interface between the fiber and the catalyst composition is filled with CaSO _{4 as a} reaction product by being impregnated with sulfuric acid after being processed into a predetermined plate shape. .

(2) In a method for producing a plate catalyst for exhaust gas denitration, which comprises coating a paste made of a catalytically active component material on a lath-processed base material of a thin metal plate, molding the paste into a predetermined plate shape, and then drying and firing the catalyst. Ca-containing inorganic fibers and water are added to and mixed with the catalytically active component raw material to form a paste, which is applied to a base material, formed into a predetermined shape, dried and fired, and then impregnated with a sulfuric acid component-containing liquid. A method for producing a plate catalyst for exhaust gas denitration, which comprises drying and calcining so that the content of SO ₄ ^2- in the catalyst composition is 6 to 10 wt%.

(3) In the method for producing a plate catalyst for exhaust gas denitration, as described in (2), the content of SO ₄ ^2- in the catalyst raw material paste is 3 wt% or less.

[0010]

When the catalyst containing a Ca component is impregnated with sulfuric acid, the present inventor produces CaSO ₄ , and the Ca reactant present in the catalyst composition adheres to the catalyst compositions or to Ca. Focusing on the fact that the mechanical strength enhances the wear resistance strength, as a result of intensive research, it was found that the wear resistance strength is significantly improved when the Ca component is present in the catalyst as a fibrous material. It was

On the other hand, in the present invention, the reaction product Ca
Since SO ₄ is not water-soluble, the adverse effect such as clogging of pores is small and the denitration performance is not significantly deteriorated. That is, C
By the reaction between the component a and sulfuric acid, the abrasion resistance can be improved without impairing the denitration rate. The reason why it is preferable to supply Ca as a component contained in the fibrous material in the present invention is that a fiber composite made of a ceramic material or the like as one method for improving strength is also effective for the catalyst targeted in the present invention. In addition, by filling the gap formed at the interface between the fiber and the catalyst composition with CaSO _{4 which} is the reaction product, the mechanical contact portion increases and the resistance to dust impact is provided.

In the present invention, it has been found that, as a method of sufficiently reacting the Ca component and SO ₄ ²⁻ in order to sufficiently bring out the strength improving effect, the catalyst is manufactured and then impregnated with an aqueous sulfuric acid solution. That is, in order to sufficiently react Ca with SO ₄ ^2−, it is sufficient to increase the amount of SO ₄ ²⁻ in the catalyst composition, but if the reaction is performed during paste kneading, drying shrinkage or the like that occurs during catalyst production, etc. It becomes insufficient to fill the gap between the fiber and the catalyst composition. Therefore, it is desirable to react the Ca component so as to fill the gap between the fiber and the catalyst composition after the fiber is added to produce the catalyst. That is, the sulfate SO ₄ ^2-amount of catalyst composition at fiber addition point is lowered to suppress the reaction of Ca, Ca is much SO ₄ ^2-amount to sufficiently react by impregnation sulfate after catalyst production Will be required. In the present invention, it is effective to specifically set the amount of SO ₄ ²⁻ at the time of paste kneading to 3 wt% or less, and to make it 6 to 10 wt% by impregnating sulfuric acid after catalysis, and it is desirable to manufacture under such conditions. . SO ₄
^The reason why the ^2- content is 6 to 10 wt% is that when the content is less than 6 wt%, the reaction with the added Ca component becomes insufficient, and as a result, the degree of improvement in wear resistance becomes small. On the other hand, SO
_This is based on the fact that if the 42 ^- content exceeds 10 wt%, the strength of the fiber itself may be reduced by passing through the reaction of the thin surface layer of the glass fiber.

[0013]

EXAMPLES Specific examples will be described below with reference to FIG. Example 1 As the metal base material 5, a material obtained by lathing a thin plate having a material of SUS430 and a thickness of 0.2 mm was used.

As the catalyst composition 1, titanium oxide, molybdenum trioxide and vanadyl sulfate were added, and Ti / Mo / V = 94 /
Blended so as to have an atomic ratio of 5/1, to which 10 parts of E glass fiber having a fiber diameter of 10 μm and an average diameter of 2.5 μm
Inorganic fiber 2 consisting of 10 parts of alumina-silica fiber (kao wool) and water were added and kneaded into a paste by a kneading machine 3. SO ₄ ²⁻ content at this time is 1.1 wt.
%, And the water content of the paste 4 is 28.9 wt%. The base material 5 and the catalyst paste 4 are simultaneously supplied to a rolling roll 6 to carry (referred to as coating) the catalyst paste on both surfaces of the base material, which is molded into a predetermined shape by a press molding machine 9 and dried. Calcination was performed at 550 ° C. to obtain a plate-shaped denitration catalyst.

17 wt% of this plate catalyst was treated with sulfuric acid
% Of was impregnated with an aqueous sulfuric acid solution 11, SO ₄ ^{2-impregnation} weight becomes 7.0 wt%, which was calcined at 350 ° C. After drying, SO ₄ in the catalyst composition (inorganic fiber is free, the same applies hereinafter) ^2- was 8.1 wt%. Example 2 Without adding the kaool of Example 1, 20 parts of E glass alone was added as the inorganic fiber, a plate-like catalyst was prepared in the same manner except that it was impregnated with a 17 wt% sulfuric acid aqueous solution. . The amount of SO ₄ ²⁻ in the catalyst composition of this example was 8.7 wt.
%Met.

Comparative Example 1 The E-glass added in Example 1 was not added, only 20 parts of kaool was added as the inorganic fiber, and a plate-like catalyst was prepared in the same manner except that the 17 wt% sulfuric acid aqueous solution was used. Was impregnated. The amount of SO ₄ ²⁻ in the catalyst composition of this example was 7.5 wt.
%Met. Comparative Example 2 A catalyst was prepared in the same manner as in Comparative Example 1 except that the sulfuric acid impregnation of Comparative Example 1 was not performed and 5 parts of silica sol was added as an inorganic binder during the paste kneading preparation. Comparative Example 3 In place of the E glass fiber of Example 1, 10 parts of Ca-free S glass fiber (including Mg component) was added, and a plate-like catalyst was prepared in the same manner except for the above, and the amount of 17 wt% Impregnated with aqueous sulfuric acid solution. The amount of SO ₄ ²⁻ in the catalyst composition of this example was 8.2 wt%.

Comparative Example 4 SO ₄ ²⁻ in the catalyst composition before adding the fiber of Example 1
Was prepared in the same manner as above, except that it was 8 wt%, and was impregnated with a 17 wt% sulfuric acid aqueous solution. The amount of SO ₄ ²⁻ in the catalyst composition of this example was 11 wt%. Comparative Example 5 A plate-like catalyst was prepared in the same manner except that the E glass fiber of Example 1 was not added, and instead 2 parts of Ca (OH) ₂ was added, and impregnated with a 17 wt% sulfuric acid aqueous solution. .
The amount of SO ₄ ²⁻ in the catalyst composition of this example was 7.1%.

Table 1 shows the status of the addition of fibers and the treatment with sulfuric acid in Examples and Comparative Examples. Table 2 shows the compositions of the inorganic fibers used in Examples and Comparative Examples.

[0019]

[Table 1]

[0020]

[Table 2] With respect to the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 to 5, the measurement results of wear resistance, SO ₂ oxidation rate and denitration rate are summarized in Table 3 with Example 1 as a reference. Wear resistance here is that 8 kg of steel grit is naturally dropped from a height of 1 m,
It was made to collide with the catalyst plane at an angle of 45 °, and the abrasion loss at that time was evaluated. The SO ₂ oxidation rate is 380 ° C at the reaction temperature.
And the denitration rate at 350 ° C. was expressed as a ratio.

[0021]

[Table 3] According to Table 1, Examples 1 and 2 to which E glass, which is a Ca component and a fibrous substance, was added, had wear resistance equivalent to that of Comparative Example 1 in which no Ca component was added, but the denitrification rate decreased. small. This is because in Comparative Example 1 in which only the alumina-silica fiber was added, water-soluble aluminum sulfate was generated by the sulfuric acid treatment and the pores were blocked. Comparative Example 3 is Ca
This is the case when S glass containing no components is added.
Due to the presence of the components, a water-soluble reaction product is generated, which causes a reduction in the denitration rate.

In Comparative Example 2, the inorganic binder is filled in the pores to lower the denitration rate, but the abrasion resistance is rather poor because the gap between the fiber and the catalyst composition is not filled sufficiently. In Comparative Example 4, Ca reaction was caused on the glass fiber surface at the paste preparation stage, and CaS after the catalyst was calcined.
Even if the E glass fiber whose surface is covered with O ₄ is impregnated with sulfuric acid,
It can be said that the reaction cannot be promoted enough to fill the interface gap.

Comparative Example 5 is a granular Ca component,
The fiber composite effect is smaller than that of Example 1 in which E glass fiber is added, and the abrasion resistance is low. In Examples 1 and 2, the primary firing temperature after forming into a predetermined shape was 550 ° C.
It can be appropriately selected in the range of 0 to 550 ° C. The higher the calcination temperature, the higher the abrasion resistance strength, but if it exceeds 550 ° C., the Mo component in the catalyst composition scatters. If tungsten (W) is used instead of Mo, this is not a concern and it can be allowed up to about 600 ° C. However, if the firing temperature is raised too much, the catalytic activity will decrease. Also, the secondary firing temperature after impregnation with the sulfuric acid component is 350 ° C.
However, this is because the water of crystallization in the generated calcium sulfate is skipped and the sulfate radicals are left, and there is no problem even if it is slightly shifted up and down at 350 ° C.

As the catalytically active component, those composed of titanium, molybdenum and vanadium have been mentioned, but oxides of tungsten, iron, Cu, Ni, Cr and the like can also be used as the catalytic component. Most preferably, titanium is added with one or more of molybdenum, vanadium and tungsten. Moreover, the addition amount of the inorganic fiber is 5 to 25.
It can be selected in the range of%. If it is less than 5%, the strength is insufficient, and if it exceeds 25%, the abrasion resistance strength decreases.

[0025]

EFFECTS OF THE INVENTION According to the present invention, a plate-like catalyst for exhaust gas denitration which does not have a high SO ₂ oxidation rate can be obtained because the effect of improving wear resistance strength comparable to that of an inorganic binder can be obtained and the denitration rate is small. In addition, the use of general-purpose E glass fiber is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a plate-shaped catalyst according to the present invention.

[Explanation of symbols]

1 ... Catalyst composition, 2 ... Inorganic fiber, 3 ... Kneader, 4 ... Paste, 5 ... Metal lath substrate, 6 ... Coating roll, 7 ... Coating sheet, 8 ... Plate catalyst, 9 ... Press molding machine, 10 ... Catalyst storage unit frame, 11 ... Sulfuric acid aqueous solution.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01J 27/053 ZAB A 37/02 101 A

Claims (3)

[Claims] 1. A plate catalyst for exhaust gas denitration, wherein a paste-like material made of a catalyst composition is applied to the surface of a base material obtained by lathing a thin metal plate and formed into a predetermined plate shape, and calcium ( The interface between the fiber and the catalyst composition is filled with CaSO _{4 as a} reaction product by interposing an inorganic fiber containing a component (Ca), and after being processed into a predetermined plate shape and impregnated with sulfuric acid. A plate catalyst for exhaust gas denitration, which is characterized in that 2. A method for producing a plate catalyst for exhaust gas denitration, which comprises applying a paste made of a raw material for catalytically active components to a substrate obtained by lathing a thin metal plate, shaping the paste into a predetermined plate shape, and then drying and firing the catalyst. The active ingredient raw material is added with Ca-containing inorganic fibers and water to form a paste, which is applied to a base material, formed into a predetermined shape, dried and baked, then impregnated with a sulfuric acid component-containing liquid, and dried. A method for producing a plate catalyst for exhaust gas denitration, comprising calcination so that the content of SO ₄ ²⁻ in the catalyst composition is 6 to 10 wt%. 3. The method for producing a plate catalyst for exhaust gas denitration according to claim 2, wherein the content of SO ₄ ²⁻ in the catalyst raw material paste is 3 wt% or less.