Gas Anode for Metal Electrowinning

Consumable carbon anodes are presently used in the aluminium production process, resulting in more than 1.5 tons of CO2 gas per ton of aluminium. Attempts have been made to use ceramic, cermet, or metal based inert oxygen evolving anodes to avoid the gree nhouse emissions of CO2, however, having not yet seen any commercial success. This proposal presents an alternative electrolysis process using a gas to depolarize the anode reaction. The anode, having connecting pores or channels, carries both the reduci ng gas to the anode-electrolyte interface and the current. The anodic reactions occur at the anode-liquid electrolyte interface and the supplied gas takes part in the reaction and lowers the need for electrical energy by giving a new anode product. Prel iminary experiments with aluminium electrolysis in a cryolite bath have been carried out, supplying natural gas through a permeable carbon anode. The anode consumption was reduced compared with using only a carbon anode; although lower temperatures than i n the existing process is needed to avoid competing reactions between carbon and natural gas. The major advantages of using natural gas instead of carbon are a reduction of 50 % CO2 emission and the elimination of perodic anode changes due to stable dimen sions. Other potential benefits are: -Added value to the natural gas -Improved energy efficiency compared to using electricity produced from fossil sources -Applicable for new and more efficient cell designs The project will focus on developing the anod e concept, using laboratory cells to study the electrochemical and chemical reactions, as well as the process efficiency.