Monitoring the operation of aluminium smelter cells using individual anode current measurements

In recent years, productivity and flexibility of aluminium smelting are becoming important economic drivers due to the changing cost structure. In modifying operating practices to meet these requirements there is an increase in occurrence of abnormalities, such as anode effect, which impacts control strategy as well as cell performance [1]. Therefore it is important to monitor the cell conditions during operation to detect the anomalies that will adversely affect the efficiency of operation. Monitoring and control in the Hall Heroult process are commonly based on the continuous measurements of cell voltage and line current. They reflect global process behaviour, and are used to regulate average alumina concentration, and to maintain voltage balance as well as overall heat balance in the cell [2]. Nevertheless, the Hall Heroult process is highly distributed and exhibits a strong internal coupling between process parameters. This makes cell control based on the cell voltage and line current measurements difficult to address changes in local cell conditions and to isolate process abnormalities at a localised level, especially for large modern cells, since spatial variations are more significant as cell dimensions increase [3].