Reactivity of Binder Cokes Doped with Sodium Salts

Anodes used in the electrolytic production of aluminium are made from calcined petroleum coke and a liquid pitch binder, then baked at a temperature close to 1200°C (prebaked) or in situ at cell operating temperature (soderberg, ~960°C). In addition to electrolytic consumption, anode carbon is consumed by gasification reactions with CO₂ and air and anode sloughing (dusting). Anode dusting is caused by selective reactivity, i.e. the binder coke is eaten away faster than the aggregate coke, thus releasing petroleum coke particles into the bath. Of binder pitch impurities that may catalyze the gasification reactions, Na is one of the most important.