A Sulphide Capacity Prediction Model of CaO–SiO2–MgO–Al2O3 Ironmaking Slags Based on the Ion and Molecule Coexistence Theory

Abstract

A sulphide capacity prediction model of CaO-SiO2-MgO-Al2O3 ironmaking slags has been developed based on the ion and molecule coexistence theory (IMCT) and verified by two groups of sulphide capacity data of CaO-SiO2-MgO-Al2O3 ironmaking slags by different researchers. A hot metal pretreatment slags of CaO-SiO2-MgO-Al2O3 with high binary basicity is also applied to verify the feasibility of the developed IMCT model. The predicted sulphide capacity of CaO-SiO2-MgO-Al2O3 ironmaking slags at 1773 K as well as high alumina CaO-SiO2-MgO-Al2O3 ironmaking slags in a temperature range of 1773-1873 K by the developed IMCT model has higher accuracy than the measured as well as the predicted by other sulphide capacity prediction models. The calculated equilibrium mole numbers, mass action concentrations of structural units or ion couples and optical basicity are recommended to represent slag composition for correlating with sulphide capacity of the slags compared with mass percentage of components or binary slag basicity. The developed IMCT model can calculate not only the total sulphide capacity of the slags but also the respective sulphide capacity of free CaO and MgO in the slags. Largely increasing Al2O3 content from 15 to 25% and decreasing CaO content from 40 to 34%, MgO content from 9 to 4% can improve contribution of free CaO from 97 to 99% while decreasing contribution of free MgO from 3 to about 1% to the total sulphide capacity of CaO-SiO2-MgO-Al2O3 ironmaking slags.