Prediction of voltage loss on electrical connections for aluminium smelter reduction cells

Abstract

Aluminium smelter reduction cells typically operate at 4.5 V and 100–400 kA DC. The voltage loss associated with electrical conductors and connections is approximately 0.4 V, which equates to 10 per cent of the total electricity consumed in the reduction cell. It is estimated that process improvements of 5 MW per plant (50 000 t CO₂e pa for coal based electricity) are possible through optimization of the stub to carbon (STC) contact interfaces within the anode assembly. The objective of this study is to develop a finite element analysis (FEA) model to predict the voltage loss through the STC contact interfaces as a function of electrical contact resistance (ECR) and thus evaluate the effect of this ECR on cell operation. ECR is affected by the pressure and temperature at the STC contact surfaces and is potentially sensitive to a change in stub diameter or thermal properties of cover material. In this article, a sequentially coupled thermo-mechanical-electrical FEA has been developed to model the process of casting in a typical anode assembly and its subsequent usage in the reduction cell. The ECR and its dependence on temperature and contact pressure have been derived from data available in the public domain. The FEA results are presented and discussed.