Regulation System to Improve Quality of the Metal Sucked During Tapping Operation

One of the objectives you can target from the whole process of primary aluminium production is to deliver a metal free from impurities. The tapping operation consisting in sucking liquid aluminium from the pot in a crucible through a tapping tube remains an operation requiring precautionary measures. On one hand, the operator has to correctly insert the tapping tube into the electrolytic cell at the lower part of the metal pad. And on the other hand, the volumetric flow during tapping is difficult to regulate. If the flow is excessive, it can result in bath being sucked with the metal. Bath adjunctions have many negative effects both on electrolytic cell operation and equipment soiling but above all on metal casting.To avoid such concern, ECL works in close collaboration with Rio Tinto Alcan in order to develop and adapt a system described in patent and based on components of the shelves. This system allows the control and the regulation of the flow rate of aluminium sucked from the pot by means of loops control and signal processing in PLC which controls a valve on the compressed air supply. 200 tapping operations have been performed in Alma’s plant resulting in ensuring the efficiency and reliability of the solution and significant benefits such as less equipment cleaning cycle and better metal casting.