Property Changes of Cathode Lining Materials During Cell Operation

Abstract

Carbon cathode materials are catalytically graphitized during the aluminium electrolysis. The graphitization has been characterized by X-ray diffraction. The graphitization and salt penetration cause profound changes in electrical and thermal conductivities. These properties have been determined for different commercial cathode materials as function of operational time and temperature. The assumed correlation between electrical and thermal conductivity is found to be poor. The changes in thermal conductivities of refractory and insulation materials have also been determined and actual examples of cell deterioration are given. Heat balance calculations based on the changing values of electrical and thermal conductivities demonstrate drastic changes as the cell get older. Calculations based only on virgin materials properties will give quite erroneous results.