Kinetics of Slag Reduction in Silicomanganese Production

Abstract

In this study, the reduction of three silicomanganese charges prepared from industrial raw materials was investigated under isothermal conditions between 1783 K and 1933 K (1510 °C and 1660 °C). The main reactions examined are MnO and SiO2 slag reduction following the chemical equations MnO(l) + C = Mn(l) + CO(g) and SiO2(l) + 2C = Si(l) + 2CO(g). The charges containing a combination of Assmang ore, Comilog ore, high-carbon FeMn slag with quartz were pre-reduced, melted to a MnO-SiO2-Al2O3-MgO-CaO quinary slag and reduced in presence of coke using a thermogravimetric set-up. The reduced slags were further analyzed using electro-probe micro-analysis to evaluate their MnO and SiO2 contents. It is observed that the reduction pathway occurred in two stages: a first slow and stable stage was followed by a rapid rate increase during the second stage. The rate change shift between the two stages was found to depend on the initial charge’s composition and the extent of reduction, but not on the temperature. Using an established rate equation, the kinetics of MnO and SiO2 reduction were modeled over the first stage. A good fit was obtained between simulated and experimental data.