RU2053200C1 - Method for producing aluminum bearing coagulator - Google Patents

Abstract

FIELD: water cleaning. SUBSTANCE: coal ash is mixed with concentrated sulfuric acid. The mixture obtained is sintered at 300 - 350 C during 60 - 80 min. The sintered material is leached with water at 80 C during 30 min. with relation between liquids and solids equal to 1:(3.5 - 4). Then the mixture is filtered, concentrated and dried. 80 - 84 % of Al₂O₃ is extracted to solvent. EFFECT: simplified process of coagulator producing, decreased power consumption. 2 tbl

Description

 The invention relates to chemical technology, in particular to methods for producing coagulants based on aluminum salts by utilizing production wastes, namely, ashes from burning coal, and can be used in the metallurgical, chemical industry, as well as in the treatment of drinking and industrial water and in fire fighting.

A known method of producing an aluminum-containing coagulant from spent calcined catalyst sludge [1]
According to this method, the sludge after calcination is mixed with water in a ratio of 1: 3 (by weight), and then concentrated sulfuric acid is added to the mixture. The resulting mixture was heated and maintained at 105-110 ^C for 30 min. Then the hot mixture (95-105 ^about C) is filtered, washed with water. The filtrate was neutralized with concentrated ammonia solution to pH 5.5 6.5 and cooled to 0-10 ° ^C. The precipitated crystals were washed vodoatsetonovoy mixture in a ratio of 1: (1-1.2). The yield of the finished product based on the content of Al ₂ O ₃ 87 96.2 in the waste
However, this method is unacceptable when used as a waste ashes from coal combustion, as in processing with concentrated sulfuric acid at 105-110 ^{° C} an aluminum compound contained in the ash, remain there in the form of sparingly water-soluble acid or aluminum silicate compounds.

Closest to the proposed technical essence and the achieved result is a method of producing aluminum sulfate from ashes from coal combustion [2]
In this method, coal is mixed with limestone and burned VARIATIONS 850 ^{° C,} then the ash is kept in a reducing atmosphere generated unburned carbon for 1 h, leached 24% solution of sulfuric acid for 60 minutes at 95 ^C. The resulting sulfate solution aluminum is filtered to obtain a solution and cake, which is washed with water and then the solution is purified from iron impurities by known methods, for example, high-temperature hydrolysis. The degree of extraction of Al ₂ O ₃ in solution 95.2
However, in this method, when burning coal with the addition of limestone, a cake is formed that requires grinding, which complicates the method and increases the energy consumption for obtaining coagulant.

 The objective of the invention is to simplify the method of producing coagulant.

This is achieved in that the processing of the ash are concentrated sulfuric acid at 300-350 ^{° C} for 60-80 min, and the leaching is carried out with water.

 When processing ashes from burning coal with concentrated sulfuric acid at these parameters, they are sintered, as a result of which the mullite contained in the ash goes into readily soluble compounds of aluminum sulfate salts of iron and iron, which are then leachable with water, which simplifies the production of coagulant by eliminating a number of operations, in particular such as preliminary preparation of ash for processing, its exposure after heat treatment in a reducing atmosphere, as well as through schelachivaniya water instead of dilute sulfuric acid and elimination of use (thanks to the latter circumstance) acid-resistant special steel and the use of other protective measures against corrosion.

In the initial sol, aluminum is in the form of a mullite compound, which is hardly soluble in water or acid. The destruction of this compound occurs by sintering with sulfuric acid at 300 350 ^about C for 60 to 80 minutes.

When processing ash concentrated sulfuric acid at a temperature below 300 ^{° C} and time below 60 min is negligible chemical reaction rate, the sintering does not occur, resulting in the aluminum retained in the ash in the form of sparingly water-soluble compounds. At temperatures above 350 ^C and a time of 80 minutes is thermally decomposed with sulfuric acid, increases the solubility of the silicon and its transition into the solution, which is undesirable.

PRI me R. As the source of aluminum-containing raw materials use ash TPP from burning Ekibastuz coal of the following composition, wt. Al ₂ O ₃ 30; SiO ₂ 50-60; Fe ₂ O ₅ 4-5; CaO 1-2; C 2-4.

Ash is mixed with concentrated sulfuric acid in an amount of 80 to 85% of the stoichiometrically necessary. The resulting mixture is sintered in a muffle furnace at 250; 300; 330; 350 ^about C for 120; 80; 70 and 60 minutes, respectively. The resulting cake was leached with water at 80 ^about C for 30 minutes in the ratio of Zh T 1 (3,5 4). The mixture is then filtered, evaporated and dried. Extraction into the solution of alumina Al ₂ O ₃ is 80 84%. The solid leach residue, containing up to 70 SiO ₂ , after washing and drying can be sent to the cement industry or construction industry.

 Table 1 shows the operations of the proposed method in comparison with the known, as well as the result of comparing these operations.

 From table 1 it is seen that in the proposed method there are no such time-consuming operations, such as exposure of the obtained ash in a reducing atmosphere, grinding of ash, as well as purification of the obtained aluminum sulfate solution from iron impurities by high-temperature hydrolysis, which confirms the simplification of the proposed method.

 In the table. 2 provides information on the degree of extraction of alumina depending on the sintering temperature and sintering time.

 From table 2 it is seen that the degree of extraction of aluminum oxide when using the modes in the proposed range is 82-84%, which corresponds to GOST 12966-85 (grade B) and satisfies the consumer despite the lower degree of extraction compared to the prototype due to its simplicity receipt.

 The use of the invention provides, in comparison with the prototype, the following advantages: simplification of the method for producing coagulant; reduction in energy costs; lack of consumption of an expensive reagent (CaO); the exclusion of the use of acid-resistant special steel and the use of other corrosion protection measures.

Claims (1)

METHOD FOR PRODUCING ALUMINOUS COAGULANT from ashes from coal burning, including treating the ash with sulfuric acid, leaching and filtering the resulting pulp, characterized in that the zone is treated with concentrated sulfuric acid at 300-350 ^° C for 60-80 minutes, and leaching is carried out with water.

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