Design, operation and electrochemical aspects of Hall-Héroult cells containing solid wetted cathodes: a 30-year chronicle

Abstract

The investigation of solid cathodes for aluminum reduction cells dates back to the late 1950's. These early tests showed that substituting a wetted stable cathode for the turbulent metal cathode allows the anode-cathode distance (ACD) to be decreased with an attendant voltage reduction of about IV, depending on current density. Since high efficiency is retained, specific energy consumption is decreased by about 20%. These savings are not as great as anticipated, however, because the effective electrical resistivity of the electrolyte increases as the ACD is lowered. This effect is related to the void fraction of anode gas in the interpolar space. Although TiB2 materials are available that withstand the harsh chemical environment, cell working operations result in an inordinate amount of part breakage. From an operational viewpoint the ideal cathode material would be a durable TiB2 composite coating that could be troweled onto conventional cathode (carbon) blocks.