Process for producing polycrystal silicon using sodium fluorosilicate as by-product of phosphate fertilizer industry

Provided is a process for producing polycrystal silicon from sodium fluorosilicate. Silane is produced from raw materials sodium aluminum tetrahydride and silicon tetrafluoride obtained from the decomposition of sodium fluorosilicate, a by-product of the phosphate fertilizer industry, and then is decomposed to form polycrystal silicon and hydrogen, wherein, the obtained hydrogen is used to hydrogenize sodium aluminum tetrafluoride, and the hydrofluoric acid produced as a by-product of the reaction is used to prepare fluoride salt product. The process is simple, low in cost, convenient to operate, environment-friendly and energy-saving, and the purity of the obtained polycrystal silicon is high.