Investigation of slag and condensate from the charge top in a FeSi75 furnace

Abstract

Metallurgical silicon/ferrosilicon is produced industrially in submerged arc furnaces by carbothermic reduction of quartz. In addition to raw materials, oxide impurities are present in the furnace. Accumulated slag is typically found along the furnace walls towards the charge top, as well as the furnace bottom and taphole. During optimal tapping, the slag will follow the alloy. Accumulated slag in the furnace will affect the furnace operation. Large amounts of accumulated slag will have a negative effect on the operation and lead to more CO2 emissions. A partly melted charge at the surface from a FeSi75 furnace has been collected and analyzed. All samples contained slag and/or condensate, carbon, and/or unreacted SiO2. The slag samples contained SiO2, in addition to oxides of Fe, Na, K, Mg, Al, and Ca. Slag at the charge surface may be due to sufficiently high temperature to produce slag, which again can affect how the materials distribute in the furnace.