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Bath for electrolytic reduction of alumina and method therefor

United States Patent

November 26, 2002
View the Complete Patent at the US Patent & Trademark Office
An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode. Removing sulfur from the bath can also minimize cathode deposits. Aluminum formed on the cathode can be removed directly from the cathode.
Brown; Craig W. (Seattle, WA), Brooks; Richard J. (Seattle, WA), Frizzle; Patrick B. (Lynnwood, WA), Juric; Drago D. (Bulleen, AU)
Northwest Aluminum Technology (The Dalles, OR)
09/ 721,836
November 25, 2000
The work described herein was partially funded by Pacific Northwest National Laboratory, a unit of the U.S. Department of Energy, operated by Battelle Northwest; the contract number is 310468-A-UF.