Experimental Studies of the Dynamic Formation of the Side Ledge in an Aluminum Electrolysis Cell

Abstract

An experimental setup is created to study the dynamic behavior of the side ledge under the electrolysis in a cryolite-alumina electrolyte. The installation has a built-in window on the side panel, which allows the lining material and, hence, the heat flow to be varied. The dynamic formation of a side ledge is experimentally studied as a function of temperature, the electrolyte velocity, and the heat flow during the electrolysis of aluminum. The rate of the ledge formation and the ledge thickness are determined by the heat flow caused by the electrolyte temperature, the cell side temperature, and the liquidus temperature. As in an industrial electrolysis cell, the side ledge profile formed in the experimental cell can be conventionally divided into the following three zones: the ledge at the bottom in contact with liquid aluminum, the ledge at metal/electrolyte interface, and the ledge at the electrolyte level. If the temperature of the inner wall is higher than the liquidus temperature, the side ledge does not form; if it is lower, the side ledge forms until these temperatures become the same. Therefore, the stability of the side ledge depends on the heat flow from the center to the walls; however, the dynamic behavior (solidification/melting) of the ledge in the metal zone occurs slowly and differs from the behavior of the side ledge.