Some observations on the draining of CaO-SiO2-Al2O3 slag bubble films

Fundamentals of slag foaming were investigated by withdrawing slag bubble f ilms from pools of CaO-SiO2-Al2O3 slags using platinum wire frames in order to measure their draining rate and lifetime before rupture. Studies were c arried out using a series of developed gravimetric and optical techniques. The results showed that increasing the temperature increased the rate of dr aining of the slag films; however, the influence of SiO2 concentration for a given slag temperature appears rather complicated. Measurements of the th ickness of bubble film plateau borders as a function of time showed slag te mperature to be very important in influencing their draining behavior, i.e. , the activation energy for the plateau-border thinning was found to be sim ilar to 150 kJ/mol, very close to that required for viscous flow in the sys tem studied (similar to 60 kJ/mol). A lowering of the slag surface tension by addition of surface-active oxides (such as P2O5 and Na2O) profoundly dec reased the rate of draining of the films, irrespective of the slag temperat ure.