Effective Binary Diffusivity of Silica and Viscosity of Silicomanganese Slag in the Smelting of Comilog and Wessels Ores

Abstract

Reduction of manganese and silicon oxides in smelting of silicomanganese causes significant changes in slag composition and properties, increasing the slag viscosity and decreasing diffusivities of slag components. These changes can have a strong effect on the kinetics of reduction reactions. This paper analyses effective binary diffusivity of silica and slag viscosity in the process of smelting of silicomanganese from Comilog and Wessels ores. Compositions of slag and metal phases and slag viscosity were calculated using FACTSage Version 7.2 at 1450-1600 oC. Comilog ore contained high concentration of alumina while Wessels ore had lower concentrations of Al2O3 and MnO and higher concentrations of FeO and CaO in comparison with Comilog ore. Silica effective binary diffusivity and slag viscosity were related to the ratio of non-bridging oxygens per tetrahedrally coordinated cations (NBO/T), which decreased in the process of oxides reduction. Changes in the slag composition and NBO/T ratio caused increase in the slag viscosity and decrease in the effective binary diffusivity of silica in the smelting of Comilog ore by more than an order in magnitude. In the smelting of Wessels ore, slag viscosity increased and silica effective binary diffusivity decreased by approximately 5-fold