Thermodynamic modelling of sulphide capacity of ternary silicate slags

This article proposes a structural thermodynamic model of slags to estimate the sulphide capacity (C_S) of ternary silicate melts. Sulphide ion (S²⁻) is incorporated into the silicate structure by substituting quasi-lattice sites in the slag for free oxygen ions (O²⁻). This structural model can take into account the effect of substituting one metal oxide for another in ternary systems, since it considers that each metallic oxide produces a de-polymerisation reaction of O° + O²⁻ = 2 O⁻ with a characteristic free energy change. The Cs of ternary silicates can be calculated by this model solely from the data of the binary sub-systems − no ternary terms are required. A good agreement was obtained between the experimental and the model results for the ternary slags of the SiO₂–CaO–MgO–MnO–FeO system.