Resistance due to gas bubbles in aluminum reduction cells

The contribution of gas bubbles to electrical resistance in aluminum reduction cells is becoming increasingly important as smelters attempt to reduce energy consumption. A prime example is the widespread introduction of slotted anodes to encourage faster gas bubble release from under the anodes. However quantification of the bubble resistance is difficult, which makes evaluation of process changes problematic. Studies of the effect of bubbles on electrical resistance in industrial cells, laboratory-scale electrolysis experiments, and physical models are reviewed in this paper.