| 摘要 |
The invention relates to a method for producing silane (SiH4) by a) reacting metallurgical silicon with silicon tetrachloride (SiCl4) and hydrogen (H2), to form a crude gas stream containing trichlorosilane (SiHCl3) and silicon tetrachloride (SiCl4), b) removing impurities from the resulting crude gas stream by washing with condensed chlorosilanes, c) condensing and subsequently, separating the purified crude gas stream by distillation, d) returning the partial stream consisting essentially of SiCl4 to the reaction of metallurgical silicon with SiCl4 and H2, e) disproportionating the partial stream containing SiHCl3, to form SiCl4 and SiH4 and f) returning the SiH4 formed by disproportionation to the reaction of metallurgical silicon with SiCl4 and H2, the crude gas stream containing trichlorosilane and silicon tetrachloride being liberated from solids as far as possible by gas filtration before being washed with the condensed chlorosilanes. The washing process with the condensed chlorosilanes is carried out at a pressure of 25 to 40 bar and at a temperature of at least 150° C. in a single-stage distillation column and is carried out in such a way that 0.1 to 3 wt. % of the crude gas stream containing trichlorosilane and silicon tetrachloride is recovered in the form of a condensed liquid phase consisting essentially of SiCl4, this liquid phase then being removed from the SiCl4 circuit and expanded to a pressure of 1 bar outside said SiCl4 circuit and cooled to a temperature of 10 to 40° C., whereby dissolved impurities separate out and are then removed by filtration.
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