A Thermodynamic Model for Calculating Sulphur Distribution Ratio between CaO–SiO2–MgO–Al2O3 Ironmaking Slags and Carbon Saturated Hot Metal Based on the Ion and Molecule Coexistence Theory

A thermodynamic model for calculating sulphur distribution ratio between CaO–SiO2–MgO–Al2O3 ironmaking slags and carbon saturated hot metal has been developed by using a thermodynamic model for calculating mass action concentrations of structural units or ion couples of ironmaking slags based on the ion and molecule coexistence theory. The calculated mass action concentrations of structural units or ion couples in CaO–SiO2–MgO–Al2O3 ironmaking slags equilibrated with carbon saturated hot metal at 1773 K can be applied to represent reaction ability, like classic concept of activity. The calculated total sulphur distribution ratio shows an acceptable agreement with the tested sulphur distribution ratio between CaO–SiO2–MgO–Al2O3 ironmaking slags and carbon saturated hot metal from desulphurization experiments at 1773 K. Meanwhile, the developed thermodynamic model for calculating sulphur distribution ratio between CaO–SiO2–MgO–Al2O3 ironmaking slags and carbon saturated hot metal can quantitatively determine the respective contribution of free CaO and MgO in CaO–SiO2–MgO–Al2O3 slags. A very significant difference of desulphurization ability between free CaO and MgO has been found with free CaO accounting for 97% desulphurization potential comparing with free MgO as about 3% in CaO–SiO2–MgO–Al2O3 slags equilibrated with carbon saturated hot metal at 1773 K.