METHOD FOR PRODUCTION OF CRYSTALLINE SILICIUM Russian patent published in 1996 - IPC

FIELD: metallurgy. SUBSTANCE: mixture of quartzite, charcoal, petroleum coke, wood chips, and semicoke is dosed, mixed and melted. Mentioned above semicoke is preliminary treated by nitric acid and washed by water. Then said semicoke is initially treated with alkali solution not more than twice, then by hydrochloric acid and is then washed again. Before said chemical treatment semicoke is screened against the finest fraction and is separated into fractions of low- and high sol content. Each of thus obtained fractions is affected by treatment with acids and alkali. Products of heat treatment of fractions having low sol content are added into mixture for melting silicium of high quality. Products of heat treatment of fractions having high sol content are added into mixture for melting silicium of poor quality. Said treatment by acid and alkali solutions and by water is carried out within 1-5 h at 90-100 C, ratio of solid and liquid phase being 1:(5-10). 30 % alkali solution and 17 % solution of hydrochloric acid are used for said treatment. EFFECT: decreases expense of charcoal and losses of silicium during melting. 4 cl, 2 tbl