Foam in Iron and Steelmaking

Abstract

A review. Foam is common in Fe and steelmaking processes. Fe and steelmaking slags have inherent foaminess but the presence of strong surface active compounds like P2O5, Cr2O3, CaS, V2O5, and CaF2 make the foam more stable. Stable foam can form only in the presence of surface active agents. When a bubble rises on the surface of a liquid, the film around it develops a concentration gradient of surface active agents such that Marangoni force acts in upward direction. This prevents liquid drainage from the film. The presence of surface active agents favors formation of smaller bubbles and prevents bubble rupture as well. So a strong surface active agent where ds/dc is high makes the foam very stable. When a bubble comes into contact with a solid surface, the dynamic contact angle is different from the equil. value. If the former is less than the latter, there is a resultant outward force which tries to make the bubble flat. This force is responsible for the collapse of foamy slags in the presence of large carbonaceous particles. This force is not significant for very small bubbles and is not effective when carbon particles are much smaller than the bubble.