JP2000024521A - Method for regenerating catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate a catalyst in which a masking layer is formed on the surface simply by a method in which when the catalyst in which catalyst components are supported on a carrier is regenerated, the raw material slurry of the catalyst components and the carrier is applied on the surface of the catalyst and dried or baked, and a coating film is formed. SOLUTION: In order to decompose/remove harmful substances in exhaust gas, NOx, ammonia, and others are decomposed into nitrogen gas stream and others by the reaction in which the exhaust gas is brought into contact with a catalyst in which catalyst components are supported on a porous carrier. By continuing the decomposition treatment, trace amounts of components such as As in the exhaust gas are deposited gradually on the surface of the catalyst to form a masking layer. When the functional deterioration of the catalyst takes place, the catalyst is immersed in the raw material slurry of the catalyst components and the carrier to apply the slurry on the surface of the catalyst and heated in a heating furnace to be dried or baked. In this way, the catalyst can be regenerated by forming a new coating film to be a catalyst layer on the surface of the masking layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to reproducing method of the NO _X such decomposing catalyst contained in the exhaust gas produced by thermal power plants.

[0002]

Exhaust gas resulting from accidental BACKGROUND ART thermal power plant, because it contains harmful substances such as NO _X, the catalyst components by contacting the exhaust gas catalyst is retained in a carrier NO _X and ammonia Are reacted to decompose into nitrogen gas, water vapor and the like, and then exhausted. When the exhaust gas is contacted with the catalyst in this manner, an activity inhibiting component such as a sodium component, a potassium component, or a calcium component in the exhaust gas adheres to the catalyst component and reduces the activity of the catalyst component. After the catalyst has been used for a predetermined period, the catalyst is regenerated by washing with water or an acid to remove these activity inhibiting components.

[0003]

However, trace components such as As and siloxane contained in the exhaust gas gradually adhere and accumulate on the surface of the catalyst to form a masking layer. And cannot be easily removed by washing. For this reason, if such a masking layer is formed on the surface of the catalyst, it is considered that the catalyst is regenerated by mechanically shaving the surface of the catalyst by sand blasting or the like and removing the masking layer. Although,
Not only is it extremely difficult to regenerate the catalyst by such a method without unevenness, but also the support after the regenerating treatment has a reduced strength, which is not practical.

[0004] Accordingly, an object of the present invention is to provide a method for regenerating a catalyst which can be easily regenerated even if a masking layer is formed on the surface.

[0005]

A method for regenerating a catalyst according to the present invention for solving the above-mentioned problems is a method for regenerating a catalyst in which a catalyst component is held on a carrier. After applying the raw material slurry to the surface of the catalyst, the catalyst is dried or fired to form a peritoneal membrane.

In the above-mentioned method for regenerating a catalyst, the thickness of the coating film is 20 to 200 μm.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for regenerating a catalyst according to the present invention will be described below. The method for regenerating a catalyst according to the present invention is a method for regenerating a catalyst in which a catalyst component is held on a carrier, and the raw material slurry of the catalyst component and the carrier is applied to the surface of the catalyst, and then the catalyst is dried or calcined. To form the peritoneum.

That is, in order to decompose and remove harmful substances such as NO _{X in} exhaust gas generated in a thermal power plant or the like,
By the catalyst components made of metal such as vanadium and tungsten in the catalyst was held in the porous carrier of the honeycomb type or the like made of titanium oxide is contacted with the flue gas reacting NO _X with ammonia, nitrogen Decomposition into gas, water vapor, etc., and as this processing is continued, trace amounts of components such as As and siloxane contained in the exhaust gas gradually adhere to and accumulate on the surface of the catalyst to form a masking layer. When causes a decrease in function, after immersing the catalyst in the raw material slurry of the catalyst component and the carrier and applying the slurry to the surface of the catalyst, the catalyst is heated at a predetermined temperature in a heating furnace. By drying or baking, a new coating film serving as a catalyst layer is newly formed on the surface of the masking layer to regenerate the catalyst.

The exhaust gas purification treatment is performed again using the catalyst thus regenerated, and when a masking layer is newly formed on the surface of the peritoneal membrane and the function of the catalyst is reduced again, By immersing the catalyst again in the raw slurry and drying or calcining it, a new peritoneal membrane can be formed again on the surface of the masking layer previously formed on the surface of the catalyst to regenerate the catalyst. The catalyst can be reused repeatedly.

[0010] Therefore, the catalyst can be regenerated without mechanically shaving the surface of the catalyst with sand blasting or the like.
Regeneration can be performed without reducing the strength of the carrier.

Therefore, according to such a method for regenerating the catalyst, the catalyst can be easily regenerated even if the masking layer is formed on the surface.

The relationship between the thickness of the coating formed on the surface of the catalyst and the denitration rate of the catalyst was examined.
As shown in the figure, it was found that when the coating film thickness was less than 20 μm, the denitration ratio was reduced to about 80% or less. From this, it is preferable that the coating film thickness is 20 μm or more.

The relationship between the coating thickness and the pressure loss of the exhaust gas passing through a porous carrier such as a honeycomb type was examined. As shown in FIG. 2, the coating thickness was 200 μm.
It has been found that, when the pressure exceeds the limit, the pressure loss becomes about 60 mmAq or more, and wasteful energy is required for feeding the exhaust gas to the catalyst. From this, it is preferable that the coating film thickness is 200 μm or less.

[0014]

The method for regenerating a catalyst according to the present invention is a method for regenerating a catalyst in which a catalyst component is held on a carrier, and the raw material slurry of the catalyst component and the carrier is coated on the surface of the catalyst and then applied to the catalyst. Since the peritoneal membrane is formed by drying or baking the catalyst, a new coating film that becomes the catalyst layer is formed on the surface of the masking layer formed on the surface with the use of the catalyst, and the catalyst is regenerated. Therefore, even if a masking layer is formed on the surface, the catalyst can be easily regenerated.

The thickness of the coating film is 20 to 200 μm.
m, the denitration rate can be about 80% or more, and the pressure loss can be about 60 mmAq or less.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a coating film thickness and a denitration rate.

FIG. 2 is a graph showing a relationship between a coating film thickness and a pressure loss.

Claims (2)

[Claims] 1. A method for regenerating a catalyst in which a catalyst component is held on a carrier, wherein a slurry of the catalyst component and the carrier is applied to the surface of the catalyst, and then the catalyst is dried or calcined to be coated. A method for regenerating a catalyst, comprising forming a membrane. 2. The method for regenerating a catalyst according to claim 1, wherein said coating film has a thickness of 20 to 200 μm.