METHOD OF PRODUCING CALCIUM FLUORIDE FROM FLUOROSILICIC ACID Russian patent published in 2020 - IPC C01F11/22 C01B33/12 C01C1/02 C01C1/26 B01J10/00 

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. Method of producing synthetic calcium fluoride involves reacting fluorosilicic acid H₂SiF₆ with ammonium hydroxide or ammonia in the first reactor to produce a first suspension. Said suspension is filtered to obtain a filtrate containing ammonium fluoride solution. Obtained ammonium fluoride solution is treated with calcium carbonate in a second reactor to obtain a second suspension containing calcium fluoride and ammonium carbonate. Said second suspension is filtered to obtain a filtered precipitate containing calcium fluoride and a filtrate containing ammonium carbonate solution. Filtered precipitate is washed and dried. Part of the second suspension is returned to the second reactor. Main portion of ammonia from the second reactor is removed by partial decomposition of ammonium carbonate and further purification and return of said ammonia to the first reactor.

EFFECT: invention enables to recycle fluorosilicic acid formed as a by-product during production of superphosphates and extraction phosphoric acid to obtain marketable calcium fluoride and recycling the used ammonia.

8 cl, 1 dwg, 4 ex