CALCULATION OF BYPASS CURRENTS IN MOLTEN-SALT BIPOLAR CELLS

A theoretical model is given for calculation of parasitic currents (by pass currents) for a stack of bipolar cells used in molten salt electr olysis. A simplified bypass current calculation was confirmed by the n umerical solution of the Laplace equation for Galvani potentials in th e interelectrode space and in the free space of the cell stack for the aluminium cell of the 'Alcoa Smelting Process' (AlCl3 electrolysis) w ith 11 bipolar electrodes. Due to the bypass currents the current effi ciency of the electro-chemical process was lowered to 82%-94%, dependi ng on the height of the stack, i.e. the thickness of the bipolar elect rodes. These values were in a good agreement with values obtained on t he basis of the simplified approach. The numerical solution of the Lap lace equation allowed a detailed description of the influence of the b ypass current flow on the current distribution at the edges of the bip olar electrodes.