ALUMINIUM ELECTROWINNING CELLS WITH METAL-BASED ANODES

摘要

A cell for the electrowinning of aluminium comprises a metal-based anode (10) containing at least one of nickel, cobalt and iron, for example an anode made from an alloy consisting of 50 to 60 weight % in total of nickel and/or cobalt; 25 to 40 weight % iron; 6 to 12 weight % copper; 0.5 to 2 weight % aluminium and/or niobium; and 0.5 to 1.5 weight % in total of further constituents. The anode (10) may have an applied hematite-based coating and optionally a cerium oxyfluoride-based outermost coating. The cell contains a fluoride-containing molten electrolyte (5) at a temperature below 940° C., in which the anode is immersed and which consists of: 5 to 14 weight % dissolved alumina; 35 to 45 weight % aluminium fluoride; 30 to 45 weight % sodium fluoride; 5 to 20 weight % potassium fluoride; 0 to 5 weight % calcium fluoride; and 0 to 5 weight % in total of one or more further constituents. A nickel-containing anode stem (14b) can be used to suspend the anode (10) in the electrolyte facing a cathode (21,21A,25) that has an aluminium-wettable surface (20), in particular a drained horizontal or inclined surface.