Challenges in Stub Hole Optimisation of Cast Iron Rodded Anodes

Abstract

Reduction of cell voltage through redesign of the stub holes of cast iron rodded anodes is an attractive idea. In practice, stub hole optimisation is not an easy task and in situ trials may yield what seem to be counter-intuitive results.A closer examination reveals a complex behaviour of the steel stub -cast iron -carbon joint. It was shown in previous work [1] to be a non-linear thermal-electrical-mechanical coupled system. Minimisation of the stub-to-carbon voltage drop is a balancing act between contact surface area and electrical contact resistance.To gain insights into the merits of different designs, a finite element demonstration model was built using the in-house code FESh++. Alternative configurations were studied. Potential industrial applications are discussed. IntroductionCast iron is typically used to connect the steel stubs of the anode hangers to the carbon anodes used in Hall-Héroult cells. The steel stubs are positioned into specially designed holes in the carbon anode -the stub holes -where molten iron can be cast. The solidified cast iron in the stub hole plays the role of a mechanical, thermal and electrical connection.

A Fully Coupled Thermal‐Electrical‐Mechanical Transient FEA Model for a 3D Anode Assembly

“…It is well known that opportunities for significant energy savings exist in the electrical connections and in particular the stub-tocarbon (STC) connection of pre-baked anode assemblies used in Hall-Héroult cells [1][2][3][4][5][6]. Given that smelting of metals is highly energy intensive and is performed on a large scale, any small improvement made in the design of anode assemblies is likely to translate into a large saving in operating costs and, potentially, to a reduction in greenhouse gas emissions.…”