Production of Aluminum with Low Temperature Fluoride Melts
Low cell operating temperature is desirable to minimize corrosion and promote long life of dimensionally stable anodes and cathodes. Eutectic NaF A1F3 melts, with and without added LiF AlF3 and KF A1F3, have been evaluated in 1 40 A laboratory cells at about 750degC over a period of four years with various values of the operating parameters. Particles of A12O3, suspended in the bath by O2 bubble evolution, dissolve in the anode boundary layer and prevent anode effect to greater than 2 A/cm2. Operation with multiple, vertical, monopolar anodes and cathodes at 0.5 A/cm2 each side promises a 20 fold decrease 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.