Oscillating Currents Stabilize Aluminum Cells for Efficient, Low Carbon Production

Abstract

The electrolytic current in an aluminum smelter can amplify resonant motions on the Al–electrolyte interface, producing a circulating wave that can grow out of control. Thick electrolyte layers prevent this magnetohydrodynamic metal pad instability (MPI) but sacrifice efficiency because the electrolyte is a poor conductor. In high-fidelity simulations of a TRIMET 180 kA smelter, we found that adding an oscillating component to the current prevented the MPI and replaced it with stable standing waves. We also found that initiating an oscillating current component can halt the MPI in progress. In our simulations, stable operation with steady current required a 4.3-cm anode–cathode distance (ACD), but stable operation with oscillations was achieved at 3.8 cm ACD, with heat power reduced by 12% and overall power by 4%. Different frequencies or amplitudes might allow further ACD reduction. Our method could allow Al production at lower cost, with less energy, and a smaller carbon footprint.