Method for producing aluminum fluoride and co-produced high-molecular ratio cryolite

Abstract

The invention discloses a method for producing aluminum fluoride and co-produced high-molecular ratio cryolite. The method comprises the following steps: (1) preparation of aluminum fluoride: heating fluosilicic acid of which the concentration is 13 to 14 percent to be 65 to 75 DEG C through a heat exchanger, and carrying out a stirring reaction on the fluosilicic acid and aluminum hydroxide under 70 to 80 DEG C for 12 to 16 minutes; then obtaining the aluminum fluoride through filtering and desiliconizing, crystallizing, drying, calcining and cooling; (2) preparation of the high-molecular ratio cryolite: carrying out the stirring reaction on a filtered aluminum fluoride mother solution and sodium fluoride under 80 to 90 DEG C for 50 to 60 minutes, filtering a reactant after the reaction is completed, feeding filtrate in a sewage pool for being treated, carrying out flash drying on a filter cake under 120 to 150 DEG C, and obtaining the high-molecular ratio cryolite. The aluminum fluoride prepared by the invention is low in concentration, is stable and is high in yield; the co-produced high-molecular ratio cryolite is high in quality and also high in yield; meanwhile, only the aluminum fluoride mother solution is brought in sewage during a production process, so compared with other production technologies, the method disclosed by the invention has the advantages of less sewage quantity and easiness in treatment.

Description

technical field [0001] The invention relates to a method for producing aluminum fluoride and high molecular ratio cryolite, in particular to a method for producing aluminum fluoride and high molecular ratio cryolite by using low-concentration fluosilicic acid. Background technique [0002] Aluminum fluoride is an important intermediate product of cryolite produced by direct synthesis of fluosilicic acid, a by-product in the production process of fluorite and phosphate fertilizer, and is mainly used in aluminum smelting. Cryolite, also known as sodium fluoroaluminate, its molecular formula is Na 3 AlF 6 According to the molecular ratio of sodium fluoride to aluminum fluoride, it can be divided into high molecular ratio cryolite and low molecular ratio cryolite. Among them, high molecular ratio cryolite (nNaF.AlF 3 , n: 2.8~3.0) is a mixture based on ortho-cryolite, which can be used as a co-solvent for the aluminum smelting industry. It has the advantages of less volatiliz...

AI Technical Summary

Problems solved by technology

[0003] At present, when the traditional direct synthesis method produces aluminum fluoride and high-molecular ratio cryolite, fluosilicic acid mainly comes from the by-products in the production process of fluorite and phosphate fertilizer, and the concentration is between 18 and 20%, which produces more intermediate product hydrogen fluoride Gas or oxyhydric acid puts forward higher requirements for the selection of production equipment materials and environmental protection; at the same time, the higher the concentration of the original fluorosilicic acid, the higher the concentration of aluminum fluoride is correspondingly, and the earlier the crystallization, the aluminum fluoride Yield reduction

However, the lower the concentration of the original fluosilicic acid, the slower the reaction speed, the precipitated silica crystal particles are fine, the slurry is colloidal, and the viscosity is high, which hinders the reaction with aluminum hydroxide. At the same time, the filtration speed is slow, and the filter cake is difficult to wash with water. The liquid content in the cake is high, and the yield of aluminum fluoride decreases