Carbothermic Reduction Methods for Alumina

The Hall–Héroult process for the electrolytic reduction of alumina was developed at the end of the 19th century and is still currently the only industrial process for the production of primary aluminum. Today, this process is ranked among the most energy- and CO2intensive industrial processes. Direct carbothermic reduction of alumina has been proposed as an alternative process, which can substantially improve the sustainability of primary aluminum production, leading to energy savings of up to 21% and reduction in greenhouse gas emission of up to 52%, while plant capital costs can be reduced up to 50%. However, processes developed so far suffer from low aluminum yields, primarily due to aluminum carbide and oxycarbide formation and aluminum vaporization phenomena. This article presents a thermodynamic study of the Al–C–O system and a review on the alumina carbothermic processes developed so far.