Simulation of ladle degassing in steel making process

A multi-phase-species (steel/gas/slag and dissolved elements such as, Al, O, and S) mathematical model based on the fundamental transport equations has been developed. This model was used to study the refining of steel in a ladle, in particular desulphurisation. In this approach, a Computational Fluid Dynamics (CFD) analysis was used to predict the flow pattern of the gas-stirred ladle system. The thermodynamic analysis package MTDATA from the National Physical Laboratory (NPL) was linked to the CFD model to predict the mass transaction at the steel/slag interface during the refining process. A successful linkage between the Fluent (CFD) package and the MTDATA thermodynamics package has been achieved using a Visual Basic 6.0 environment. The predictions have been compared to data from the literature and a good agreement has been found. In this present work, the capability of the model to predict the desulphurisation rate under various operational conditions has been demonstrated. The slag viscosity has been predicted using the NPL slag viscosity model and this has been successfully implemented. Therefore, it is possible to study the influence of the slag system composition variation during the refining process. Also, it will be possible to extend the present model to study other types of steelmaking processes involving slag-metal reactions. In this present work, the influence on the desulphurization rate of allowing the Ca++ mobility and CaS precipitation in the molten slag (slag system CaO-Al2O 3-SiO2-MgO) was examined.