Effect of Transient Thermal Conditions in the Slag Region on Ladle Refining

Most studies on desulfurization during ladle processing are reported under isothermal conditions. The current study examines the impact of prevailing non-isothermal conditions during ladle processing on ladle refining. A transient, multiphase thermo-fluid model of ladle processing is implemented using Ansys Fluent. The bubble plumes are modeled using discrete phase model (DPM). Temperature-dependent thermophysical properties of slag, obtained from FactSage, are incorporated in the model as user-defined function (UDF) to study the effect of non-isothermal conditions. Rising argon bubble plumes and the opening of the slag-metal interface have a cooling effect in the slag-eye region, which causes changes in the thermophysical properties of the slag phase. The local variations in the temperature of slag near the slag-metal interface are significant and far removed from the average metal temperature. These are reflected in the flow and mass transfer characteristics of this complex multiphase system. A comparative study is undertaken to demonstrate that non-isothermal conditions in the slag-metal region have a significant effect on the slag-eye opening and desulfurization kinetics. It is found that non-isothermal effects have a significant bearing on slag properties and thereby must be considered for realistic prediction of slag-eye opening, desulfurization, and all phenomena involving slag-metal interactions.