AUTOPSIES OF SPENT POT LININGS - A REVISED VIEW

摘要

Cathode autopsies performed after pot failures or shutdowns of cells have frequently been used to investigate pot failure and degradation of cathode lining. The sequence of materials observed from the cathode to the non-reacted refractory lining has been assumed to reflect the situation before the pot was taken out of service. Here we demonstrate that this is not necessary the case. Based on annealing experiments, X-ray diffraction and electron microscopy we propose that the thermal gradient in the lining is reversed during cooling and that the physical appearance of the lining reflects a combination of cooling and operation of the cell. The presence of molten phases below the carbon cathode may therefore solidify from the top rather than towards the bottom of the lining. Finally, we show experimental evidence that Na (g) infiltrate the refractory lining and is the main attacking chemical specie in the reaction front.