Grant: Collaborative Research and Development Grants

In this proposed 5-year project, in collaboration with Rio Tinto Alcan, we will extend fundamental knowledge and develop physicochemical models for the dissolution of alumina and behaviour of the side-ledge (freeze) in Hall-Héroult aluminium electrolysis cells, using both experimental methods and modeling from basic principles. Dissolution and distribution of alumina in the molten electrolyte (bath) is a very limiting factor in the stable operation and in the improvement of energy efficiency of the Hall-Héroult process. The side-ledge is formed on the sidewall by extracting heat and solidifying a part of the bath. Its thickness can vary much as non steady-state events occur (anode effect, alumina feeding, anode change, tapping). The presence of the ledge on the sidewall protects the integrity of the cell and improves the service life of the cells by improving the thermal stability during the transients. The alumina transport and ledge dynamics are strongly coupled by the thermal and physicochemical mechanisms present in the molten electrolyte. Measurements and modeling of the alumina distribution and side-ledge behaviour will give Rio Tinto Alcan the necessary tools for improved simulation, operation and cell design. Rio Tinto Alcan produces two million tons of aluminium in Hall-Héroult cells in Canada every year and the international competition, especially from Russia and fast emerging Asian economies is now very strong. The proposed experimental study and modeling of alumina dissolution and side-ledge behaviour will provide a unique advantage to Rio Tinto Alcan both by improving of the energy consumption and by reducing of the pollution of the environment.