Kinetics and mechanism of silicothermic reduction process of calcined dolomite in magnetherm reactor

• We studied the reduction kinetic which was controlled by solid state diffusion model.
• We discussed the mechanism of the reduction process.
• The C3MS2, CaSi2 and Ca2Si intermediate phases formed during the reduction process.
• The formation of C2S and C3S phases in sintered briquettes lowers the reducibility.

The present study investigates the silicothermic reduction kinetic and mechanism of the dolomitic charges used in the magnetherm type reactors under inert atmosphere. The dolomitic charges are composed of a mixture of calcined dolomite (dolime) and ferrosilicon pressed in the briquettes form. Initially, these briquettes were sintered under argon at different temperatures 700–1000 °C, then reduced in magnetherm reactor. Different technical parameters such as the effect of sintering temperature, the reduction temperature (1450–1550 °C) and reduction time (up to 20 min) were investigated. The produced slag was characterized using XRD, XRF, and SEM techniques. Maximum reduction extent (about 80%) was achieved at optimum reduction conditions. These optimum conditions were double stoichiometric amount of silicon (2 ×) which is necessary to reduce all magnesium oxide present in dolomitic charges, sintering temperature of 700 °C for1 hr, reduction time of 15 min and reduction temperature at 1550 °C. The results showed that the reduction of the dolomitic charge is controlled by the solid state diffusion process and the calculated value of the activation energy was found to be about 498 kj/mol.