Abstract
Most laboratory systems investigating the aluminium production process utilize a single anode set-up. When approaching alumina depletion under constant current conditions in such a system, the potential will increase to high levels (>10 V) and initiate an anode effect and perfluorocarbon generation. However, it has been discovered by industrial measurements that perfluorocarbon generation may also occur at normal cell voltages. With the use of a two-anode setup in parallel with an electronic load this phenomena was investigated in the laboratory. The results indicate that as long as the rest of the cell can acquire the extra load, partial passivation of one or more anodes is possible and can be accompanied by small amounts of PFC evolution (0–3 ppm mol CF4). Individual anode potentials can be highly elevated, albeit the changes get buried in the total cell voltage. Only when the total load becomes too large the voltage rises abruptly and substantial amounts of PFC can be produced (≫1000 ppm mol CF4).