A thermodynamic model for calculating manganese distribution ratio between CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 ironmaking slags and carbon saturated hot metal based on the IMCT

Abstract

ABSTRACTA thermodynamic model (IMCT-LMn) for calculating manganese distribution ratio between CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 slags and carbon saturated liquid iron have been developed based on the ion and molecule coexistence theory. The predicted manganese distribution ratio shows a reliable agreement with the measured ones. With the aid of the IMCT-LMn model, the respective manganese distribution ratio of (Mn2+ + O2−), MnO·SiO2, 2MnO·SiO2, MnO·Al2O3, MnO·TiO2, and 2MnO·TiO2 are investigated. The results indicate that the structural units SiO2 + FeO play a key role in CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 slags in demanganisation process in the course of hot metal treatment at 1673 K. The manganese distribution ratio at a given binary basicity range increases with CaF2 content, while that decreases with TiO2 content at different binary basicity scopes, which demonstrate that high Mn in the metal is favoured by TiO2 content. In the present study, various critical experiments are carried out in an effort to clarify the effect of temperature on demanganisation ability, indicating that the lower temperature of molten metal is, the faster the rate of demanganisation reaction is and the shorter the thermodynamic equilibrium time is and the lower end-point Mn content is. It can be deduced from the obtained experimental results that the greater oxygen potential of slags or iron-based melts, lower content of basic oxides in slags, and lower temperature at reaction region is benefit for demanganisation reaction.