Study on Bubbling Behaviour in Hall Hero

In the Hall-Heroult electrolytic process of aluminium smelting, CO2 bubbles are generated under the horizontal anode which play an important positive role in homogenisation of the alumina distribution and the temperature field in the electrolytic bath. On the other hand, the gas bubbles increase the ohmic voltage drop underneath the anode surface which in turn results in higher energy consumption for the smelting process. Therefore, a clear understanding of the bubble generation mechanism and movement underneath the horizontal surface is important to optimize the process. In the present study, the formation and movement of a single bubble underneath the horizontal anode was investigated first. Bubble size was found to decreases at lower surface tension of the electrolyte. Then, a 1/4 th scale low temperature electrolytic model of the Hall-Heroult process was developed to investigate the electrolytic bubble behaviour under the horizontal anode surface. Dynamic similarity between the model and real cell was maintained using dimensionless Eotvos number. It was observed that electrolytic bubbles generate uniformly under the whole anode surface and grows through gas diffusion and coalescence. At higher current density and higher anode inclination angles bubbles escaped quickly from underneath the anode surface.