Formation of silicon carbide from microsilica waste by means of lignite semicoke

Abstract

The formation of silicon carbide from briquetted batch consisting of microsilica waste from silicon and silicon-alloy production is investigated. The batch is treated at 1873, 1923, and 1973 K, for 5–30 min, with various reducing agents: lignite semicoke, coal semicoke, coke breeze, and coke dust. The best results are obtained when using lignite semicoke from the Berezovsk deposit in Kansko-Achinsk Basin: the yield of silicon carbide is 97.00–97.62%; it constitutes 82.52–84.90% of the products obtained. The optimal treatment temperature and time are determined: 1923–1973 K for 15–20 min. The products consist predominantly of cubic silicon carbide (β SiC). Chemical enrichment increases the SiC content in the products to 90–91%; this is higher than in abrasive micropowder of grain size 1–2 μm. The effectiveness of enrichment in terms of oxide and iron impurities is high: 87–95%. The silicon carbide is characterized by a high silica content: more than 7%. Accordingly, it may be regarded as a promising material for the production of siliconcarbide refractories used in silica binder. Silicon carbide is obtained as micropowder with irregular particles in the size range 0.2–1.0 μm.