| 摘要 |
Process for the production of anhydrous calcium fluosilicate from anhydrous calcium chloride and impure fluosilicic acid solution, a by-product of the acid treatment of phosphorus ores containing fluorine, characterized in that a calcium fluosilicate dihydrate is precipitated at low temperature and quantitatively by suitable adjustment of the fluosilicic acid concentration and the molar ratio CaCl2/H2SiF6 and that after filtration, washing and drying of the precipitate, an anhydrous calcium fluosilicate which can be easily decomposed by heat treatment is obtained to restore calcium fluoride and silicon tetrafluoride suitable for the manufacture of pure hydrofluoric acid and fluosilicic acid. For gravimetric concentrations of H2SiF6>25% and molar concentration ratios CaCl2/H2SiF6 between 2 and 5, the yields of the anhydrous calcium fluosilicate obtained are greater than 94%. |
