Numerical and dimensional analysis of slag emulsification due to bottom gas injection in ladles

Bottom gas injection in ladle metallurgy is an important method to improve mixing, which in turn promotes more homogeneous chemical composition and heat distribution of the slag/metal system which can also result in higher refining rates and productivity. Emulsification of the top slag layer, if it is under control, it offers important improvement on mass transfer but can be easily run out of control and affect the steel quality due to entrapment of slag droplets. In this work, slag emulsification has been investigated through both physical and mathematical modelling. The results have been analyzed using dimensional analysis to provide a new equation which defines slag emulsification as a function of the velocity at the slag/metal interface, a parameter obtained by the numerical model. Furthermore, another dimensionless expression has also been developed to obtain the velocity at the slag/metal interface using experimental values on the slag eye area and inlet gas velocity. The equation proposed can easily be employed to define the effect of the physical properties of the slag and gas injection conditions on the extent of slag emulsification.