A thermodynamic and kinetic model of reoxidation and desulphurisation in the ladle furnace has been developed by using a two-dimensional fluid-flow model combined with equations expressing the thermodynamics of reoxidation and desulphurisation. More specifically, ladle vacuum treatment of a gas-stirred ladle has been simulated. In order to describe the activities of the oxide components of the slag, expressions by Ohta and Suito¹⁾ were adopted. The thermodynamic model describes the slag/metal equilibria between Al, Si, O, Mn and S in the molten steel and Al₂O₃, SiO₂, FeO, MnO and S in the slag. A fluid dynamic model that considers the slag, steel and argon phases derives the kinetics. Results from an isothermal calculation have been heuristically compared with industrial plant data and they show good agreement. The model results have also revealed that the reduction of silica plays a part in aluminium loss during ladle treatment.