Numerical simulation of slag foaming on bath smelting slag (CaO–SiO2–Al2O3–FeO) with population balance modeling

A computational fluid dynamic (CFD) model has been developed for the simulation of slag foaming on bath smelting slag (CaO–SiO2–Al2O3–FeO) by considering foam as a separate phase. The CFD model has been used to predict the foam height, bubble number density and the multiphase flow phenomena in the system. The height of foam is dynamically balanced by the formation of foam due to transformation of both gas and liquid into foam and its destruction due to liquid drainage and bursting of bubbles, transforming foam back to liquid and gas. The bubble break-up and coalescence were considered in gas–liquid dispersion whereas in the foam layer, the bubble coalescence due to film rupture was incorporated. A population balance modeling was used to track the number density of different bubble classes and fixed pivot method was used to discretize the population balance equation. The model predicted the foam height of the slag system (CaO–SiO2–Al2O3–FeO). The content of FeO was changed and its effect on the foam height predicted. The foaming index was calculated and the results from the model predict that the foaming index decreases with increase of FeO content in slag. The CFD model also predicts that the foaming index of a slag with Al2O3 is higher than that of slag without Al2O3. Dimensionless analysis was performed based on the model available in the literature to correlate the foaming index with the physical properties of the slag. The predicted results from the present study are in reasonable agreement with available experimental data.