Inorganic fluorides production in fluor treatment of phosphate raw material in the USSR

Abstract

The manufacture of inorganic fluorine compounds by phosphate raw material treatment ranks in the USSR a significant place as to providing country with fluoride products. At present over 35% of technical fluoride salts in the country is produced by mineral fertilizers plants. P:F ratio in apatite cocentrate is 5.8, while its 4.1 in Karatau phosphate concentrate obtained by flotation. With due account of the commercially possible value of fluorine recovery (40–60%), fluorine reserves in phosphate rocks of the USSR 2–3 times exceed those in fluorspar. The fluorine utilization of phosphate raw materials is realized almost exclusively from Kola apatite concentrate. In the manufacture of fertilizers and phosphoric acid by the wet process, the off-gases containing fluorine are trapped in the scrubbing systems, the thus obtained silicohydrofluoric acid solutions are fed for further treatment with the formation of AlF3, Na3AlF6, Na2SiF6, K2SiF6, (NH4)zSiF6,NH4HF2 and NaF. The various fluoride production routes are used in the USSR, which secure in most of cases product quality meeting the requirements of world market. Moreover, the production processes of granular fluoride salts, calcium fluoride have been developed; in continuous operation are the plant production of anhydrous hydrogen fluoride and hydrofluoric acid from bifluoride-fluoride ammonium. The USSR is exporting aluminium fluoride, Na2SiF6 and is prepared to increase the export of fluorine products if the respective production lines are retrofitted.