Abstract: A self-baking, Soderberg type carbon anode (40) for use in an aluminum electrolyses cell (1) to form product aluminum (11), where the anode (40) is consumable in molten electrolyte (12) in the cell, the anode having top, bottom and side surfaces and at least four layers of vertically disposed plate inserts (48) meltable in the molten electrolyte, the plate inserts (48) preferably made of aluminum and are capable of melting to create hollow vertical slots (52) at the bottom of the anode facilitating any gas bubbles (60) generated to channel to the side of the anode into the electrolyte (12).

Abstract: Methods and apparatus are disclosed for reducing sulfur impurities in aluminum electrolytic production cells in order to significantly increase current efficiency of the cells. An impurity reduction zone may be created in the bath of an inert anode cell by submerging a purifying electrode in the bath. In another embodiment, an oxygen barrier tube may be disposed in a portion of the bath. In a further embodiment, reductants such as aluminum, CO and/or CO2 are added to the bath. In another embodiment, electrode current is interrupted or electrodes are removed from selected regions of the cell in order to allow gaseous impurities to escape from the bath. Sulfur impurity levels may also be reduced in inert anode cells by scrubbing bath emissions from the cell before they are reintroduced into the cell, and by controlling sulfur impurity contents of materials added to the cell.

Abstract: Methods and apparatus are disclosed for reducing sulfur impurities in aluminum electrolytic production cells in order to significantly increase current efficiency of the cells. An impurity reduction zone may be created in the bath of an inert anode cell by submerging a purifying electrode in the bath. In another embodiment, an oxygen barrier tube may be disposed in a portion of the bath. In a further embodiment, reductants such as aluminum, CO and/or CO2 are added to the bath. In another embodiment, electrode current is interrupted or electrodes are removed from selected regions of the cell in order to allow gaseous impurities to escape from the bath. Sulfur impurity levels may also be reduced in inert anode cells by scrubbing bath emissions from the cell before they are reintroduced into the cell, and by controlling sulfur impurity contents of materials added to the cell.