Study of an alternative route for alumina production: Integration of calcium looping to Pedersen process aiming at zero emissions and bauxite residue avoidance

The aluminium industry is a notable emitter of CO₂ and a significant contributor to mineral scarcity. Alumina extraction, typically conducted via the Bayer process, faces two main challenges: using fossil fuels and generating bauxite residue. A recently proposed approach, the Pedersen process, aims to address these challenges by removing the iron oxide content from the ore through an additional iron smelting step, thereby eliminating the generation of bauxite residue. This study evaluates the material and energy performance of alumina and pig iron co-production from bauxite using the principles of the Pedersen process. Different thermodynamic simulations of a Pedersen process layout were carried out using Aspen Plus software, and key parameters were validated against existing literature. Additionally, diverse CO₂ capture configurations based on calcium looping were assessed, performing an energy optimization to achieve carbon-neutral and zero-residue alumina production.

Results indicate that the energy demand of the Pedersen process is notably higher than the average Bayer process for bauxites with high aluminium/iron ratios, with an estimated energy consumption of 11.92 GJ per tonne of products. However, low aluminium/iron ratios render better energy performances (10.15 GJ per tonne), showing potential feasibility in terms of energy consumption. The integration of a calcium-looping plant led to low energy penalties, thanks to the replacement of CaCO₃ in the Pedersen plant by adding purged CaO from the calcium-looping plant. The energy penalties, estimated at a minimum of 1.10-2.79 GJ per tonne of CO₂ avoided, show favourable results that could pave the way for a smarter use of resources and a decarbonized alumina production.