Abstract
Long term measurement campaigns were conducted at Hydro Aluminium’s Reference Centre in Årdal. The work comprised high frequency measurements of all individual anode current loads in three test cells. Typical patterns of current load as a function of the anode age are presented and discussed. Middle-aged anodes showed increased current fluctuations, which could be related to the anode setting pattern. The current load started increasing when the anode slots had worn away. This is apparently explained by a decreasing anode-cathode distance. It was possible to provoke local anode effects (AE) at one or more individual anodes by manipulation of the alumina feeders. Such AEs were detected as sudden drops in the current without significant increase in the cell voltage. All observed general AEs were initiated on old anodes where the slots had worn away.