The downstream consequences of rising ni and v concentrations in smelter grade metal and potential control strategies

Technology for controlling smelter metal impurities post reduction has steadily improved. For example, control of sodium has seen the reduction and in some plants elimination of chlorine gas. However, changes in the purity of cell feed materials such as anodes are giving rise to new challenges in impurity control; vanadium and nickel levels are an emerging problem. This paper briefly reviews the important impurities and their effects on downstream casting, forming and final application properties. Particular emphasis is given to nickel and vanadium. Strategies for controlling these impurities are also discussed and areas where new technology is needed are also highlighted. In some cases it is not known where the tolerable limits of impurities are. There are a plethora of metal refining techniques used in the extraction of other metals which can be investigated for control of impurities in smelter grade aluminum