Thermal shock resistance of anode carbon for aluminium electrolysis

摘要

Anode carbon is consumed in the aluminium electrolysis process. As each anode is consumed, it is replaced by a new one. The new anode is suddenly exposed to severe thermal shock as it is submerged in the hot electrolyte. Temperature gradients in the anode cause mechanical stresses and may induce cracks. These cracks can result in spalling off corners or more severe cracking shortly after the anodes have been put into service. When fracture occurs, pieces of the anode can fall into the pot and disturb the pot operation. The aim of this work was to develop a way to determine the thermal shock resistance of carbon materials for aluminium production, specially for anodes. The parameters that are reviewed are pitch content, granulometry of coke particles, and kind of coke. Methods to measure the thermal shock resistance directly are developed and tested with regard to their ability to distinguish between anodes with small differences in composition. For both laboratory and full scale anodes, the shock resistance is calculated from measured thermal and mechanical material properties. The full scale anodes are set in electrolysis, and the calculated results are compared to the crack frequency of the full scale anodes. 49 refs., 109 figs., 44 tabs.