METHOD OF PRODUCING POLYCRYSTALLINE SILICON IN CLOSED CIRCUIT Russian patent published in 1998 - IPC

FIELD: silicon production. SUBSTANCE: method includes hydrogen reduction of trichlorosilane, separating and purifying components of gas mixture (SiHCl₃,SiCl₄,H₂,HCl) leaving reactor, reusing these components to prepare polycrystalline silicon and carrying out trichlorosilane synthesis. According to invention, gas mixture of trichlorosilane reduction products is cooled to temperature from 0 to 40 C, filtered to remove solid impurities, and condensed at liquid nitrogen temperature to separate recycled hydrogen. Hydrochloric acid is sublimed at 85 C and then evaporated. Chlorosilanes are separated, and trichlorosilane is directed into hydrogen reduction apparatus. Silicon tetrachloride together with hydrogen chloride are directed into trichlorosilane synthesis apparatus, where industrial-grade silicon is also used. EFFECT: enabled closed-circuit conditions and improved product quality.