Spent Potlining from Aluminium Electrolysis-Are Cells with Vertical Inert Electrodes a Solution?

Spent potlining (SPL) is a term used in the aluminium industry for the spent cathode lining materials of industrial electrolysis cells. SPL is the cathode and sidewall materials that are removed from a cell after being shut down. The treatment of spent potlining is an environmental problem that has been a challenge for a long time and it needs to be solved. Sodium ions are the main carrier of electrical current through the molten cryolite bath during electrolysis, and a small amount of sodium metal is formed as part of the cathode reaction. Sodium penetrates the porous horizontal carbon cathode blocks in the bottom of the cell and causes swelling of the carbon material. With the present cell design it is not possible to eliminate this sodium interaction, and the only way to avoid it is to use a different cell design. The present paper discusses whether the use of cells with vertical inert electrodes will give less sodium penetration in the carbon part of the cell.