Numerical Simulation of Slag Foaming in High Temperature Molten Metal with Population Balance Modeling

A computational fluid dynamic (CFD) model has been developed for the simulation of slag foaming on bath smelting slag (CaO-SiO-Al2O3-FeO) by considering foam as a separate phase which is comprised of a mixture of gas and liquid. The model accounts for the formation of foam due to transformation of both gas and liquid into foam and it's destruction due to liquid drainage and bursting of bubble. The bubble break-up and coalescence was considered in gas-liquid dispersion whereas in the foam layer, the bubble coalescence due to film rupture was incorporated. Population balance modelling was used to track the number density of different bubble class. The model predicted the foam height of the slag system (CaO- SiO-Al2O3-FeO). The foam height was found to increase with the increase of superficial gas velocity. The content of FeO was changed and its effect on the foaming index was observed. The results from the present model show that foaming index decreases with increase of FeO content in slag. The results from the CFD model also show that the foaming index of a slag with Al2O3 is higher than that of slag without Al2O3. The predicted results from the present study are in reasonable agreement with the experimental data.