Investigation of Anodic Gas Film Behavior in Hall-Heroult Cell Using Low Temperature Electrolyte

A novel one-fourth scale low temperature electrolytic model of the Hall-Heroult cell was constructed to investigate the electrolytic bubble formation, coalescence, and movement under the horizontal anode surface. The principles of geometric and dynamic similarities were applied in developing this model electrolytic cell for the first time. A 0.28 M aqueous CuSO4 + 20 pct H2SO4 solution was used as the electrolyte. Analogous to the Hall-Heroult cell, copper (Cu) was deposited at the cathode and oxygen (O-2) bubbles were generated underneath the anode. The bubble generation mechanism, development, coalescence, and detachment underneath the anode were observed using a high speed camera. It was found that electrolytic bubbles were generated uniformly under the entire anode surface and grew through gas diffusion and coalescence. With increasing current density (CD) and anode inclination angle to the horizontal, bubble velocity increased underneath the anode surface. Moreover, the bubble layer thickness and bubble sizes decreased with an increase in anode inclination angle. Bubble coverage under the anode also decreased with increasing anode inclination angle, but was found to be insensitive to the change in CD. Finally, the calculated bubble resistance was found to decrease with increasing anode angle. (C) The Minerals, Metals & Materials Society and ASM International 2013