Flotation of Alumina on the Surface of the Electrolyte in an Aluminum Electrolysis Cell

A model of flotation was developed and applied to alumina in the aluminum electrolysis cell. The conditions of flotation for alumina on the cryolitic bath surface were determined for disc and sphere geometries. The contact angle between alumina and cryolitic bath, which had not been found in the literature, was measured and it was found to be around 30 deg. Experiments with compressed alumina discs on the cryolitic bath surface were conducted, and the results were compared to the model. The experiments showed how impurities on the bath surface influence the flotation; and how a slight asymmetry in the system may accelerate sinking.