Simulation of the Ferrosilicon Process Using Small-Scale Laboratory Furnace

The production of silicon (Si) and ferrosilicon (FeSi) alloys is one of the largest metallurgical industries in Norway. These alloys are smelted in electric arc furnaces. The aim of this work is to increase process understanding and operational efficiency by simulating such furnaces using laboratory equipment. Graphite crucibles were filled with coke, quartz, iron ore pellets, and wood chips provided by an industrial partner, and heated in an induction furnace. Three sets of experiments were carried out to simulate the production of three different alloy grades: 96, 75, and 52% Si (by mass) at two different temperatures of 1850°C and 1900°C, and a constant holding time of 30 min. The crucibles were later cast in epoxy, and various domains were analysed using scanning electron microscopy. The phases evidenced in the different zones of the crucibles are discussed and compared to observations from industrial furnace excavations. The effect of the alloy grade on the distribution of the products is also considered. The production of FeSi 52 was deemed possible under the experimental conditions and a cavity was present in the crucible. Increasing the holding to 60min, a cavity was present in the case of FeSi 96 but the amount of metal produced was negligible. Two Si producing mechanisms were observed: sweating of Si metal from the layer of brown condensate around the crater and Si production on SiC particles according to SiO + SiC = 2Si + CO. the reduction of the iron ore pellets appeared to follow the shrinking core model, with the reduction of wüstite to Fe being the rate limiting reaction.