Abstract
The decomposition voltage of inert anodes at 800 °C is close to the voltage for alumina decomposition, indicating that the anodic overvoltage cannot be too high, and the alumina concentration should be near saturation. Sufficient alumina concentration at the anode may be challenging at low temperatures due to low solubility and diffusion coefficient. The “slurry cell” concept was analysed. The alumina particles need to be very small (<10 μm) to affect the transport rate at the anode. Materials for wetted cathode are discussed. Solid cathodes with a thin metal film are vulnerable to the formation of solids in the less AlF3 rich bath at the cathode. Based on a voltage breakdown, the energy consumption with inert anodes will be higher than in the Hall-Héroult process at current densities above 3.7 kA/m2. The factors above all indicate that the current density needs to be considerably lower with inert anodes than in a traditional cell.