The influence on current distribution by the initial shape and position of an anode and by the curvature of the aluminium in prebake aluminium cells

摘要

Mathematical modelling of the secondary current distribution in prebake aluminium cells was used to study the influence of (i) a modified anode shape, (ii) curvature of the metal, and (iii) an anode being set too high or too low. The calculations show that if the lower corners of a new anode are cut off by 5 cm (diagonally), the steady state shape of the anode is reached after 3 days, as against 6-8 days for rectangular corners. If the metal curvature corresponds to a 3 cm difference in height per 100 cm length, and the sloping metal is facing a newly set horizontal anode, the current density varies across the anode with a maximum of 125 % of the normal value (0.75 A cm"2), and it takes 4 days until the anode is aligned with the metal. If a new anode is set 1 cm too low or too high, the initial current through that anode after heat-up is 123 % and 84 % respectively, compared to the normal value, and it takes 4.2 and 7.7 days respectively, until the interpolar distance is correct (45 ± 1 mm).