Method for preparing ammonium fluorosilicate by utilizing fluorine-containing white slime in anhydrous hydrogen fluoride production

Abstract

The invention discloses a method for preparing ammonium fluorosilicate by utilizing fluorine-containing white slime in anhydrous hydrogen fluoride production. The method comprises the following steps of: under the condition that the mol ratio of ammonium fluoride calculated based on SiO2 to the fluorine-containing white slime is 9-15, adding the fluorine-containing white slime, a mixed mother liquid and a supplementary ammonium fluoride solution under the conditions that the temperature is 90-108 DEG C and the pressure is minus 15 to 0Kpa, performing a dissolution reaction until the white slime is completely dissolved, so as to obtain a dissolved solution; while the dissolved solution is hot, filtering the dissolved solution to remove undissolved SiO2 and mechanical impurities, so as to obtain a mixed solution; performing heat exchange on the mixed solution until the temperature is 60-70 DEG C; cooling to 12-30 DEG C, separating out ammonium fluorosilicate crystal and performing liquid solid separation, so as to obtain a crystallization mother liquid and crystal ammonium fluorosilicate; washing and filtering to obtain the crystal ammonium fluorosilicate; and drying the crystal ammonium fluorosilicate, so as to obtain the product ammonium fluorosilicate. The method disclosed by the invention has the advantages of simple technical process, less equipment, simplicity and convenience in operation and low production cost.

Description

technical field

[0001] The invention belongs to the technical field of chemical industry, and specifically relates to a method for preparing ammonium fluorosilicate by utilizing fluorine-containing silicon slag, a by-product produced in the production of anhydrous hydrogen fluoride.

[0002] Background technique

[0003] A large amount of fluorosilicic acid is by-produced in the production process of phosphate fertilizer industry. When anhydrous hydrogen fluoride (AHF) is produced by the one-step method of contacting concentrated sulfuric acid with fluorosilicic acid as raw material, a large amount of fluorine-containing silicon slag is produced by-product. Silicic acid exists in the form of free fluorine and lattice fluorine. How to make good use of fluorine and silicon resources in fluorine-containing silicon slag is a major issue in clean production and comprehensive utilization of resources.

[0004] Ammonium fluorosilicate [(NH 4 ) 2 SiF 6 ] Also known as ammonium ...

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