FEM analysis of voltage drop in the anode connector induced by steel stub diameter reduction

Primary aluminium production is a high-energy consumption process, and improving the energy efficiency of smelters could be economically viable. An issue in the Hall–Héroult prebake anode technology is the voltage drop in the anode connector caused by the thermo-electro-mechanical interface contact between steel stub, carbon anode, and cast iron thimble. Steel stubs are exposed to an extremely aggressive environment throughout their service life, involving thermomechanical stresses and chemical attacks that cause shape changes. To estimate voltage drop due to change in stub shape, a 3D finite element model (FEM) of a whole anode was developed and solved with the in-house code FESh++. Steel stub diameter variations were compared with a new stub configuration. Results show a voltage increase of about 10 mV between new and damaged configuration simulations. This holds promising potential for improving energy efficiency. An experimental factorial design was used to determine the main factor in steel stub diameter variation affecting voltage drop in the anode connector assembly.

► A 3D FEM thermo-electro-mechanical numerical model was developed, taking into account the electrical contact resistance, thermal conductance, mechanical contact and displacement, and Joule effect of a whole anode connector assembly used in an aluminium reduction cell.
► Using an experimental design, steel stub diameter variation effect on the voltage drop of the anode assembly was investigated.
► Results indicate that contact pressure in the outer stubs impacts greatly the voltage drop in the model.