Method for reducing ammonium fluorosilicate in ammonium fluoride

Abstract

The invention discloses a method for reducing ammonium fluorosilicate in ammonium fluoride. The method comprises the steps as follows: fluosilicic acid is subjected to an amination reaction to producean ammonium fluoride mixed solution containing silicon dioxide, wherein the mass concentration of ammonium fluoride is 20%-35%, the mass concentration of silicon dioxide is 2%-15%, and the PH value is 8.0-10; the ammonium fluoride mixed solution is filtered by a filter press, most silicon dioxide is removed, and an ammonium fluoride solution containing a little silicon dioxide is obtained; the ammonium fluoride solution containing a little silicon dioxide is left to stand and clarified in a filtrate tank for 1-3 h, most silicon dioxide settles to the bottom, an upper clear ammonium fluoride liquid is subjected to refined filtration by micropores with the diameter being 3-10 micron again, and a wet filter cake returns to a feeding tank of the filter press; a filtrate enters a concentratedraw material tank to be left to stand and clarified for 1-3 h, an upper clear ammonium fluoride liquid is taken to enter a concentration system, conventional concentration, ammonia introduction, crystallization and centrifugal separation are performed later and an ammonium fluoride product is obtained. The method can effectively reduce ammonium fluorosilicate in ammonium fluoride and is low in energy consumption and environmentally friendly.

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 fluoride. Background technique [0002] Ammonium fluoride products are produced from fluosilicic acid by-products of phosphate fertilizer enterprises. The process is to generate silicon dioxide and ammonium fluoride through the ammoniation reaction of fluosilicic acid. After removing the silicon dioxide by filtration, ammonium fluoride solution is obtained and the The ammonium fluoride solution after silicon is concentrated, and liquid ammonia is added to the concentrated solution, and the ammonium fluoride product is obtained through cooling, crystallization and separation. 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 guarante...

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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 silicon dioxide is brought into the concentration system along with the ammonium fluoride solution. Concentration is a process of high-temperature evaporation and continuous ammonia overflow. Silicon dioxide and ammonium fluoride are easily dissolved and reacted to form ammonium fluorosilicate, ammonium fluorosilicate With the concentrated liquid, it is separated by cooling and crystallization, and part of it is brought into the ammonium fluoride 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 fluoride products