Thermodynamic Modelling of Sulphide Capacity of Ternary Silicate Slags

Abstract

This article proposes a structural thermodynamic model of slags to estimate the sulphide capacity (C_S) of ternary silicate melts. Sulphide ion (S^2-) is incorporated into the silicate structure by substituting quasi-lattice sites in the slag for free oxygen ions (O^2-). 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° + O^2- = 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.