Production of aluminum with low temperature fluoride melts

Abstract

Low cell operating temperature is desirable to minimize corrosion and promote long life of dimensionally-stable anodes and cathodes. Eutectic NaF-AlF 3 melts, with and without added LiF-AlF 3 and KF-AlF 3, have been evaluated in 1 - 40 A laboratory cells at about 750??C over a period of four years with various values of the operating parameters. Particles of Al 2O 3, suspended in the bath by O 2 bubble evolution, dissolve in the anode boundary layer and prevent anode effect to greater than 2 A/cm 2. Operation with multiple, vertical, monopolar anodes and cathodes at 0.5 A/cm 2 each side promises a 20-fold decreases in cell volume compared to conventional H-H cells, with an accompanying decrease in capital cost. Projected specific energy consumption is about 11 kwh/kg.