High-purity, solar cell-grade silicon production involves reacting gaseous silicon monoxide and solid carbon in an oxygen-free atmosphere

摘要

High-purity silicon production by reduction of silicon-oxygen compound involves reacting silicon monoxide gas and solid carbon (both of solar cell purity) in oxygen-free atmosphere by indirect heating at at least 1,850 degrees C to form silicon carbide (SiC) such that: (1) molar ratio SiO:SiC is at least 2.5:1; (2) the silicon formed is removed; and (3) SiO is added and reaction gases removed, with SiO:SiC molar ratio held at at least 2.5:1 until conversion to silicon is complete. An Independent claim is also included for apparatus comprising the following parts : an evaporation chamber (1) in which a mixture of pure solid silicon monoxide or of silicon dioxide and Si is heated in an evaporation vessel (2) under vacuum at at least 1,300 degrees C; a connection pipe (3) and a gas inlet (4) in which the SiO gas is conveyed into a reaction chamber (5); a carbon electrode (6) which heats the chamber (5) via an indirect device (7) to at least 1,850 degrees C and around which the gas is led; a heated collecting vessel (8) for the liquid silicon dripping from electrode (6); and a condensation chamber (9) into which the reaction gas is fed for separation out of any excess of silicon monoxide.