Aluminum fluoride production process

Aluminum fluoride, Aluminum fluoride Molecular formula: AlF3 Molecular weight: 83.98 Character: White crystal or powder. The relative density at 25°C is 2.882, slightly soluble in water, acid and alkali solution, insoluble in most organic solvents, and has greater solubility in hydrofluoric acid solution. Anhydrous aluminum fluoride is very stable in nature; it does not react with liquid ammonia even when heated with concentrated sulfuric acid to fumes, does not change with hydrated potassium hydroxide, is not reduced by hydrogen, and does not decompose when heated, but sublimates, with a sublimation temperature of 1291. °C. It can be partially hydrolyzed to hydrogen fluoride and aluminum oxide at 300-400°C. poisonous.
Aluminum Fluoride Product Use: As an electrolytic bath component in the production of aluminum, to reduce the melting point and increase the conductivity of the electrolyte. Used as an inhibitor of fermentation when producing alcohol. It is used as a fluxing agent for non-ferrous metals in ceramic glazes and enamel glazes. Used for welding liquids in metal welding. Used to make optical lenses. Also used as a catalyst for organic synthesis and raw materials for artificial cryolite.
Aluminum fluoride production process:
First, the wet production process (a phase-out process): sulfuric acid and fluorite gas generated after high-temperature reaction, direct absorption into 30% to 35% of hydrofluoric acid, and aluminum hydroxide synthesized at about 90 °C AlF3? 3H2O, After filtration, it is dehydrated and dried at a high temperature, and finally aluminum fluoride AlF3 is finished. Since the water vapor generated during the dewatering decomposes AlF3, the wet aluminum fluoride content is low, the impurities are large, the moisture content is high, the bulk density is low, and the fluidity is poor. Basically not suitable for use in modern electrolyzers. Chemical indicators: F ≥ 57%, Al ≥ 28%, Na ≤ 3.5%, H2O ≤ 7%.
Second, the dry production process (dry aluminum fluoride): 1, crude acid dry method: sulfuric acid and fluorite gas after high temperature reaction, after rough washing into the fluidized bed, and aluminum hydroxide reaction after drying, Generates aluminum fluoride at high temperatures. Since the content of hydrogen fluoride after rough washing is about 96%, the impurities are relatively high and the impurities of the aluminum fluoride product are relatively high; in particular, there is no desilication, so that the silica content of the aluminum fluoride product reaches 0.25%. These impurities will affect the quality of electrolytic aluminum and increase the power consumption during electrolysis. F ≥ 61%, Al ≥ 30%, Na ≤ 0.5%, H2O ≤ 0.5%, SiO2 ≤ 0.28%, P2O5 ≤ 0.04%, Fe2O3 ≤ 0.1%
2, dry acid method: sulfuric acid and fluorite gas after high temperature reaction, after rough washing, freezing, degassing, distillation into the evaporator, then the hydrogen fluoride content is generally 99.5%; evaporated hydrogen fluoride gas ( The amount is close to 100%) Enter the fluidized bed and react with wet aluminum hydroxide to produce aluminum fluoride at high temperatures. Due to the high purity of hydrogen fluoride, the quality of the aluminum fluoride thus produced is very good and the impurities are very low. In particular, the content of silicon dioxide is only 0.02%, and the content of phosphorus pentaoxide is only 0.007%, which is very favorable for the production of electrolytic aluminum. F≥62%, Al≥32%, Na≤0.5%, H2O≤0.5%, SiO2≤0.03%, P2O5≤0.01%, Fe2O3≤0.03%.