Influence of the Sulphur Content in the Carbon Anodes in Aluminium Electrolysis – a Laboratory Study

Abstract

The chemistry of sulphur in carbon anodes is not fully understood, especially its influence on the electrolysis parameters. The results of this study are indicative of an important link between the sulphur content in the anode material and the carbon consumption as well as the current efficiency during aluminium electrolysis. By performing a laboratory scale investigation of different carbon anodes with sulphur contents ranging from 1.97 to 3.82 wt% S in addition to graphite anodes with sulphur content close to zero, it was found that increasing sulphur content contributes significantly to a decrease in the current efficiency and a rise in the carbon consumption. When going from 0 to 3.82 wt% S, the current efficiency decreased from 92 to 85% (1.8 % per 1 wt% S), and the carbon consumption rose from 108 to 128% (5.2 % per 1 wt% S).