Changes of Effective Binary Diffusivity of Silica and Viscosity of Silicomanganese Slag in the Process of Reduction of MnO and SiO₂

Reduction of manganese and silicon oxides in smelting of silicomanganese causes significant changes in slag composition and properties: decreasing the ratio of non-bridging oxygens per tetrahedrally coordinated cations (NBO/T), 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 ore. Compositions of slag and metal phases and slag viscosity were calculated using FACTSage V.7.2 at 1723 K to 1873 K (1450 °C to 1600 °C). Silica effective binary diffusivity and slag viscosity were related to the NBO/T ratio which decreased in the process of MnO and SiO₂ reduction from 3.18 (molten charge) to 0.97 at 1723 K (1450 °C), 0.486 at 1773 K (1500 °C), and 0.38 at 1823 K to 1873 K (1550 °C to 1600 °C). Changes in the slag composition and NBO/T ratio caused increase in the slag viscosity and decrease in the effective binary diffusivity of silica by more than an order in magnitude.