Study on the Dissolution of Alumina in Cryolite Electrolyte Using the See-Through Cell

Abstract

By using the see-through cell, the dissolution phenomenon of alumina in the cryolite electrolyte was clearly visible. In this paper, the dissolution processes of primary and secondary alumina in typical aluminum bath were shown and the dissolution rates were compared as well as the temperature fluctuations during dissolution. Both the video and temperature measurements confirm the three key steps of the dissolution process: fast dissolution upon feeding, crust formation and sludge dissolution. And the dissolution rate in each step is very different. Secondary alumina displays a quite different dissolution behavior from primary alumina. Meanwhile, the dissolution rate of secondary alumina is much faster than that of primary alumina. The mechanism for alumina dissolution under the influences of MOI, LOI, surface area, absorbed fluorine and carbon content was also discussed.