Method for reducing ammonium fluorosilicate in ammonium bifluoride

Abstract

The invention discloses a method for reducing ammonium fluorosilicate in ammonium bifluoride. The method comprises the steps as follows: fluorosilicic acid is subjected to an ammoniation reaction anda silicon dioxide-containing ammonium fluoride mixed solution is obtained, wherein the mass concentration of ammonium fluoride is 20%-35%, the mass concentration of silicon dioxide is 2%-15%, and thePH value is 8.0-10; the ammonium fluoride mixed solution in step (1) is filtered by a filter press, most silicon dioxide is removed, a filtrate enters a filtrate tank and left to stand and clarified for 1-3 h, most silicon dioxide settles to the bottom, and the upper layer is a clear ammonium fluoride liquid; the upper clear ammonium fluoride liquid in step (2) is finely filtered again by micropores with the diameter being 3-10 micron, and a wet filter cake returns to a feeding chute of the filter press; a refined filtrate enters a concentrated raw material chute to be left to stand and clarified for 1-3 h, an upper clear ammonium fluoride liquid enters a concentration system, conventional concentration, acid addition, crystallization and centrifugal separation are performed later, and anammonium bifluoride product is obtained. The method can effectively reduce ammonium fluorosilicate in ammonium bifluoride, has low energy consumption, introduces no other impurities and avoids waste emission.

Description

technical field [0001] The invention relates to the technical field of chemical industry, in particular to a method for reducing ammonium fluorosilicate in ammonium bifluoride. Background technique [0002] Ammonium bifluoride products are produced from fluosilicic acid by-products of phosphate fertilizer enterprises. The process is to use fluosilicic acid to react with ammonium to generate silicon dioxide and ammonium fluoride. After removing silicon dioxide by filtration, ammonium fluoride solution is obtained, and the The ammonium fluoride solution after silicon is concentrated, and the concentrated solution is added with anhydrous hydrogen fluoride or hydrofluoric acid, cooled, crystallized, and separated to obtain ammonium bifluoride product. But it has the following problems: since the ammoniation reaction of fluorosilicate is mainly driven by the addition of excess ammonia to complete the reaction, it is filtered and separated by a filter press, but it is difficult ...

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Problems solved by technology

But it has the following problems: since the ammoniation reaction of fluorosilicate is mainly driven by the addition of excess ammonia to complete the reaction, it is filtered and separated by a filter press, but it is difficult to guarantee 100% solid-liquid separation by simple filter press filtration, and a small amount of The filtered silica is brought into the concentration system along with the ammonium bifluoride solution. Concentration is a process of high-temperature evaporation and continuous ammonia overflow. Silica and ammonium bifluoride are easily dissolved and reacted to form ammonium fluorosilicate. Ammonium fluorosilicate The liquid is separated by cooling and crystallization, and part of it is brought into the ammonium bifluoride product, which affects the product quality. The mass concentration of ammonium fluorosilicate is 2.5-5%.

There is no report on the method for removing ammonium fluorosilicate impurities in ammonium bifluoride products at present