Thermodynamic Assessment of MnO and FeO Activities in FeO–MnO–MgO–P₂O₅–SiO₂(–CaO) Molten Slag

Abstract

The activity coefficients of MnO and FeO in an FeO–MnO–MgO–P₂O₅–SiO₂(–CaO) slag system were measured on the basis of the equilibrium between Ag and molten slag at 1673 K under a controlled atmosphere. On the basis of experimental results, the activity coefficients of MnO and FeO in this multicomponent slag were evaluated using a regular solution (RS) model, FactSage, and an empirical formula. In the case of the RS model, the interaction energies and conversion factors to fit the calculated values to experimental results were reassessed. By the used of the empirical formula, FactSage and the regular solution model of present work, the activity coefficient ratio of MnS and FeS in a Fe–Mn–O–S matte that was equilibrated with a FeO–MnO–MgO–P₂O₅–SiO₂ slag system was evaluated. When the RS model was used to calculate the γ_MnO/γ_FeO ratio, the γ_MnS/γ_FeS ratio decreased slightly with an increase in the X_MnS/X_FeS ratio. In contrast, when the empirical formula and FactSage were used, the γ_MnS/γ_FeS ratio was almost constant when the X_MnS/X_FeS ratio was increased.