Effect of anodic gas release on current efficiency in Hall-Heroult cells

The convection in Hall-Heroult cells caused by anodic gas evolution is computed for different cell geometries. The fluid flow data are applied to compute local mass transfer coefficients, in order to estimate the current efficiency as a function of the internal cell geometry defined by the sideledge thickness at the metal-bath interface. The results indicate that there is a non-linear relationship between current efficiency and the width of the side channel. When increasing the channel width, there is initially a sharp drop in current efficiency, while the current efficiency seems to be less affected if the channel is wide. The model results show good agreement with measured data from industrial cells.