Phosphate Fertilizer Industry Byproduct Fluosilicic Acid Utilization

With the growth of the capacity of wet-process phosphoric acid (WPA) and phosphate fertilizer industry, the quantity of by-product fluosilic acid is mass. Production of 1 ton WPA or 1 ton single superphosphate (SSP) (100%P2O5) will product about 0.06 ton fluosilic acid (100%H2SiF6). People pay more and more attention to the problem of its market. Aiming at the problem, the by-product fluosilic acid of phosphate fertilizer industry is used to product sodium fluosilicate in the thesis. The use of Sodium fluosilicate is wide. The fluorine of fluosilic acid comes from phosphate rock. Phosphate rock contains about 2~5% fluorine. In the process of production of WPA, about 60% of fluorine go into gas. The absorbed gas can be used, the other go into liquid phosphoric acid and solid phosphogypsum. The interrelated data of fluorine and the distribution in every composition of production of WPA and triple superphosphate (TSP) is given. The production process of sodium fluosilicate, experimental raw material and physicochemical characteristics, use, quality standard of production is described.The desilica with ammonia from fluosilic acid and experiment of ammonium fluoride solution reacting with sodium chloride solution to produce sodium fluosilicate is emphasized. Experiment show: the process route is feasible, operation uncomplicated, and the suitable process parameters are obtained:(l)raw material is removed impurity ;(2)the excessive ratio of ammonia above 20%;(3) reaction time is 75~90 min ; (4)about 70 ℃ ammoniated to remove silica, filter after quickly cooling;(5)depositing filtrate benefit for desilica; (6) the excessive ratio of sodium chloride solution is above 20%; (7) synthesis time of sodium fluoride is above 80 ℃; (8) condensing the feed slurry; (9) dealing with ammonium chloride solution by evaporating crystallization or cooling salt solution. Material balance is calculated, the received ratio of F is 97.15%, and the flow sheet of the process is presented.The production process of sodium silicofluoride is briefly introduced. Comprehensive utilization the solution from production process of sodium silicofluoride by the SSP method is tried in yunnan three circles chemicals. CO. LTD, the solution is used to product precipitation phosphate fertilizer. Experiment show: this process route is feasible. The experiment of calcining sodium silicofluoride to produce sodium fluoride is roughly done, and sodium carbonate solution is used to deal with residual of sodium silicofluoride. Experiment show: it can obtain about 94% sodium fluosilicate by calcining about 800℃ in laboratory, and can obtain about 98% sodium fluosilicate of class I after dealing with by sodium carbonate solution.Raw material cost of two process route in the paper is the lowest through comparing with many other process route of sodium silicofluoride. The cost of the process of using ammonia to deal with fluosilic acid is 519.01 yuan, and that of calcining sodium silicofluoride is 662.15 yuan. Occupational health and environmental protection can be achieved national standard in the process of production, and utilization of fluosilic acid in other field is also briefly introduced.