The invention relates to a method for the production of high purity silicon,
characterized by the following steps: a) reaction of metallic silicon with silicon
tetrachloride (SiCl4), hydrogen (H2) and hydrochloric acid
(HCl) at a temperature of 500 to 800 C. and a pressure of 25 to 40 bar to
give a trichlorosilane-containing (SiHCl3) feed gas stream, b) removal
of impurities from the resultant trichlorosilane-containing feed gas stream by
scrubbing with condensed chlorosilanes at a pressure of 25 to 40 bar and a temperature
of 160 to 200 C. in a multi-stage distillation column, to give a purified
trichlorosilane-containing feed gas stream and a solid-containing chlorosilane
suspension and a distillative separation of the purified feed gas stream into a
partial stream essentially comprising SiCl4 and a partial stream, essentially
comprising SiHCl3, c) disproportionation of the SiHCl3-containing
partial stream to give SiCl4 and SiH4, whereby the disproportionation
is carried out in several reactive/distillative reaction zones, with a counter-current
of vapour and liquid, on catalytic solids at a pressure of 500 mbar to 50 bar and
SiHCl3 is introduced into a first reaction zone, the lower boiling SiH4-containing
disproportionation product produced there undergoes an intermediate condensation
in a temperature range of -25 C. to 50 C., the non-condensing SiH4-containing
product mixture is fed to one or more further reactive/distillative reaction zones
and the lower boiling product thus generated, containing a high proportion of SiH4
is completely or partially condensed in the head condenser and d) thermal
decomposition of the SiH4 to give high purity silicon.
