METHOD OF REFINING METALLURGICAL SILICON Russian patent published in 2012 - IPC C01B33/37 

FIELD: chemistry.

SUBSTANCE: invention relates to methods of purifying silicon using plasma technology during industrial production of silicon. The method involves heating crude silicon in a crucible until a melt is obtained and treating the melt with a plasma jet containing an inert gas, a reducing gas and water vapour. The silicon is treated with an argon plasma jet with a water vapour admixture, directed vertically from bottom-up through a hole in the bottom of a quartz crucible in a vacuum. The silicon is preheated to 1400°C using an induction heater and a graphite cylinder. Temperature of the wall of the graphite cylinder is controlled using an optical pyrometre. Cooling and directed crystallisation of silicon from the walls of the crucible to the centre of the hole in the melt is carried out by gradually reducing temperature of the plasma jet. Further, the induction heater is switched off and after complete cooling, the ingot is removed, from which the bottom part of the skull layer is cut off and the remaining part is ground.

EFFECT: obtaining from metallurgical silicon with purity of 98-99,9% a polycrystalline silicon ingot of purity 99,9999 % with phosphorus content of not more than 0,1 ppmw, boron content of 0,1-1 ppmw, which is suitable for industrial production of photoconverters.

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