A thermodynamic model for calculating manganese distribution ratio between CaO–SiO 2 –MgO–FeO–MnO–Al 2 O 3 –TiO 2 –CaF 2 ironmaking slags and carbon saturated hot metal based on the IMCT

Abstract

A thermodynamic model (IMCT-L _Mn) 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-L _Mn 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.