Numerical Investigation of Bubble Induced Electrical Resistance in Aluminium Reduction Cells
نویسندگان
چکیده
A gas layer in the form of bubbles exists at the bottom surface of anodes in aluminium electrolytic cells in the HallHeroult process. The gas bubbles increase electrical resistance, cause an additional voltage drop and increase energy consumption. While the presence of gas bubbles is an inherent feature of the process, it is important to assess their contribution to voltage drop however this is difficult to study in detail experimentally. This paper presents a quantitative assessment of the bubble induced electrical resistance using a computational fluid dynamics (CFD) modelling platform. Using twodimensional geometry of part of an electrolytic cell as test bed, the current flow was simulated with the presence of a bubble layer beneath the anode. Detailed information on the bubble layer was obtained from an air-water model using a digital camera to capture the transient bubbling dynamics. The simulations were conducted at different gas generation rates representing different current densities. The simulated bubble induced voltages are within the range of the experimental measurement results on commercial cells from other researchers. Predicted bubble resistances are within the range of published empirical correlations, but do not fit in any particular expression. The presence of bubbles does not greatly affect global current flow in the whole cell, but it does significantly affect the local current flow at the anode bath interface. Local peaks in current flow occur at the bubble and liquid boundary on the anode.
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