End-of-Life Treatment of Spent Potlining from the Aluminum Industry by Low Pressure and Heat

Abstract The environmental footprint of the aluminum industry is affected by greenhouse gas emissions and the amount of waste generated. Spent potlining (SPL) has traditionally been deposited, but increasing scrutiny is put to this practice. The cost of deposit is also increasing. First cut SPL is the carbon rich part and are the remaining cathode at end-of-life of an aluminum cell. A method for cleaning the first cut SPL is proposed which involves high temperature and low-pressure treatment for removal of fluoride-rich electrolyte remains. This way the carbon rich part of the SPL can become a product which can be reused or secondly used as an energy source, instead of being deposited. 5–19 kg of SPL has been treated for four hours in a furnace at low pressure and high temperature, and a post-treatment carbon purity up to 98 wt pct was found. The electrolyte condensate mainly consists of NaF og Na 3 AlF 6 . An LCA study on the process related to Norwegian aluminum smelters has been performed and the distance to the SPL treatment plant, the energy used during treatment and the SPL pre-processing, was found to affect the sustainability of such an industrial process the most.