Some Observations on the Draining of CaO-SiO2-Al2O3 Slag Bubble Films

Fundamentals of slag foaming were investigated by withdrawing slag bubble films from pools of CaOSiO2-Al2O3 slags using platinum wire frames in order to measure their draining rate and lifetime before rupture. Studies were carried out using a series of developed gravimetric and optical techniques. The results showed that increasing the t emperature increased the rate of draining of the slag films; however, the influence of SiO2 concentration for a given slag temperature appears rather complicated. Measurements of the thickness of bubble film plateau borders as a function of time showed slag temperature to be very important in influencing their draining behavior, i.e., the activation energy for the plat eau-border thinning was found to be ~ 150 kJ/mol, very close to that required for viscous flow in the system studied (~60 kJ/mol). A lowering of the slag surface tension by addition of surface-active oxides (such as P2O5 and Na2O) profoundly decreased the rate of draining of the films, irrespective of the slag temperature.