METHOD OF PRODUCTION OF PURE SILICON

摘要

The method of production of pure silicon by aluminothermic reduction of silicon dioxide in silicon-containing phosphorous slags for PV industry and solar batteries manufacture.Phosphorous slag is loaded into open graphite crucible and then heated in the induction furnace at the eutectic melting temperature, whereupon it is added with aluminium. Obtained silicon separated from the slag emerges on the slag's surface. Then it is loaded with the new portion of slag and aluminium. The process should be repeated for several times, until full sedimentation of the reacted slag and its separation from silicon, which appeared in the top part of reactor. Obtained silicon is discharged into the graphite mould and cooled up to formation of the grain patterns with average sizes of crystals less than 1 mm. Than the silicon is crushed and sifted for the removal of small particles and exposed to hydrochemical treatment with aqueous solutions of mineral acids in two stages. Thus, this process allows receiving silicon powder with total purity of 99.99 %.Favorable results may also be obtained when up to 30 mole % of alkaline earth metal fluorides or other substances that increase the solubility in the slag or the aluminum oxide that is formed are added to the slag.