JP2732073B2 - Cleaning agent for denitration catalyst during coal combustion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cleaning agent for removing scale adhering to a denitration catalyst during combustion of coal.

<Prior Art> Oil-fired and coal-fired denitration catalysts are very expensive, and if they have deteriorated due to the adhesion of scale, it is desirable to wash and reuse them. And, when washing the catalyst, in the case of oil-fired, most of the attached scale is a water-soluble alkali metal salt, so it can be washed with water, but for coal-fired, silica, aluminum, calcium, such as fly ash, etc. At present, an effective cleaning agent has not been found because it is an oxide such as magnesium and has a low solubility. Some attempts have been made to polish the surface of the catalyst.However, there are problems such as labor required for polishing, labor and time required to reduce the thickness of the surface to minute cracks contributing to the denitration reaction, and shortening the service life by polishing. Has not been reached.

<Problems to be solved by the invention> Since the scale attached to the denitration catalyst in the case of coal firing as described above has little effect with water washing and general cleaning agents, furthermore, from the problem of shortening the life in surface polishing,
Replacing the denitration catalyst with a new one would be an obstacle especially in economics. However, as described above, if the surface of the denitration catalyst can be cleaned, the denitration catalyst deteriorated by the attached scale can be regenerated, so that a simple and effective cleaning agent is removed.

<Means for Solving the Problems> The present invention relates to a detergent for a denitration catalyst at the time of coal combustion, obtained by solubilizing or emulsifying a salt of a carbonate and a chelating agent in water.

The carbonate used in the cleaning agent of the present invention is at least one kind of a water-soluble carbonate such as sodium carbonate, potassium carbonate and ammonium hydrogen carbonate and a carbonate which becomes soluble in water by a chelating agent such as calcium carbonate and magnesium carbonate. Is blended.

The salt of the chelating agent is a salt of a carboxylic acid chelating agent such as ethylenediaminetetraacetic acid, diethylenetriaminetriacetic acid, hydroxyethyliminodiacetic acid, succinic acid, citric acid, malic acid, diglycolic acid, gluconic acid, and maleic acid. At least one compound is mixed with an acid, a sodium salt such as ethylene tetracarboxylic acid, an ammonium salt, a potassium salt, an alkanolamine salt and the like.

The cleaning agent for the denitration catalyst during coal combustion of the present invention is carbonate,
In addition to the salt of the chelating agent, a surfactant may be added for the purpose of improving the wetting to the scale and the permeability. Such surfactants include anionic, nonionic,
Both amphoteric and cationic surfactants can be used,
Preferred are nonionic surfactants such as polyoxyethylene alkylphenyl ether and polyoxyethylene alkyl ether having an HLB of about 10 to 16 having excellent wettability to scale and excellent permeability.

The carbonate and the chelating agent of the detergent for denitration catalyst during coal combustion according to the present invention have no effect when each is dissolved in water. When dissolved in water in combination, the scale on the surface of the denitration catalyst dissolves in a short time only by immersion, and a part of the scale is peeled off and removed from the catalyst surface, and is regenerated by washing with water and drying. Although the theory of the effect of the combined use is not clear, it is presumed that a synergistic effect works to help the metal component of the scale and the salt of the chelating agent to chelate. Further, the cleaning agent of the present invention does not dissolve materials such as V, W, Fe, and Ti, which are denitration catalysts.

The detergent for the denitration catalyst at the time of coal combustion according to the present invention preferably contains 0.1 to 50% by weight, particularly 0.1 to 40% by weight, of the total amount of the carbonate. %
It is preferred to contain.

<Examples> Examples of the present invention will be described below.

The deteriorated surface of the used coal-fired denitration catalyst of Company K was cut into the same area, and the cleaning agents of Examples 1 to 6 and Comparative Example 1 described below were cut.
After being immersed in cleaning agents Nos. 1 to 4 for a certain period of time, washed with water and dried, the state of scale removal on the surface was observed with an electron micrograph. Table 1 shows the results.

Example 1 Ethylenediaminetetraacetic acid / trisodium 25 wt% sodium carbonate 10〃 water 65〃 Example 2 Nitrosotriacetic acid / trisodium 20 wt% sodium bicarbonate 8〃 polyoxyethylene oleyl ether 3〃 (number of moles of ethylene oxide added = 10 mol) 69% by weight of water Example 3 Diethylenetriamine triacetic acid / trisodium 22% by weight Ammonium citrate 3〃 Calcium carbonate 5〃 Polyoxyethylene nonyl phenyl ether 5〃 (Number of moles of ethylene oxide added: 7.5 mol) Water 65〃 Example 4 Malic acid Triethanolamine 1wt% Potassium carbonate 0.1〃 Polyoxyethylene sorbitan fatty acid ester 1〃 (Number of moles of ethylene oxide added = 20 mol) Water 97.9〃 Example 5 Sodium gluconate 10wt% Sodium carbonate 40〃 Water 50〃 Example 6 Ethylenediamine 4 Acetic acid・ Tetraammonium 50wt% sodium carbonate 10wt% water 40 水 Comparative Example 1 Ethylenediaminetetraacetic acid 酢 酸 tetrasodium 25wt% polyoxyethylene oleyl ether 3〃 (the number of moles of ethynylene oxide added = 10 mol) water 72〃 Comparative Example 2 sodium hydrogen carbonate 20 wt% polyoxyethylene nonyl phenyl ether 5〃 (number of moles of ethylene oxide added = 7.5 mole) Water 75〃 Comparative Example 3 Hydrochloric acid (35%) 10 wt% polyoxyethylene oleyl ether 5〃 (number of moles of ethylene oxide added = 10 mole) Water 85〃 Comparative Example 4 Water 100wt% As can be seen from Table 1, the cleaning in Examples 1 to 6 was almost completed by immersion for 30 minutes. In comparison, in Comparative Examples 1 to 4, 30
Washing is not sufficiently performed by minute immersion, and only about 40% is washed.

<Effects of the Invention> As described above, according to the present invention, the denitration catalyst at the time of coal combustion can be easily washed only by immersing for a short time. Further, since the cleaning agent can be reused until saturation is reached, it is economically incomparable compared to the case where the cleaning agent is replaced with a new one. Also, as compared with polishing cleaning, an excellent cleaning effect can be obtained without much trouble and labor, and without a problem of shortening the service life due to wall thinning.

Claims (4)

(57) [Claims] 1. A detergent for a denitration catalyst at the time of coal combustion, obtained by solubilizing or emulsifying a salt of a carbonate and a chelating agent in water. 2. The detergent for a denitration catalyst during coal combustion according to claim 1, wherein the salt of the chelating agent is a salt of a carboxylic acid-based chelating agent. 3. The detergent for a denitration catalyst at the time of coal combustion according to claim 1, wherein the detergent contains 0.1 to 40% of a carbonate. 4. The detergent for a denitration catalyst during coal combustion according to claim 1, wherein the chelating agent contains 1 to 50% of a salt in the detergent.