Investigating Magnetohydrodynamic Stability of an Aluminium Electrolytic Cell under Various Manufacturing Process Conditions

Mathematical simulation of industrial aluminium electrolytic cell operation allows us to predict and indicate the causes of magnetohydrodynamic (MHD) instability and bath level skewing, as well as investigate other features of the aluminium electrolysis process. In order to analyse the MHD stability of the electrolytic cell, we adapted a three-dimensional mathematical model that uses a multi-phase approach to describing the media (aluminium, electrolyte and gas) and treats the hydrodynamic, electromagnetic, thermal and electrochemical processes in the bath as interrelated. Our test calculations confirmed that the model is adequate and that the numerical solution proposed converges with sufficient accuracy. The paper describes our numerical investigation results concerning MHD stability of a multi-anode electrolytic cell when its thermal conditions and working space shape configuration change; our simulation included the metal-electrolyte phase interfaces and took into account the MHD instability developing when replacing burnt-out anodes. We estimated how various initial crust configurations affect the MHD stability. We investigated how the process parameters affect the working space shape in the bath, which is a dynamic object, same as the metal-electrolyte interface and the reverse oxidation zone surface. We specifically studied the way changes in potential affect the MHD stable shape of the working space in the bath. We show that varying the potential between any given pair of anodes can change the shape of the working space, that is, crust melts as potential increases, while lowering potential leads to further accretion. As this happens, we note that there is an increase in the vibration magnitudes of the liquid metal and the lower reverse oxidation zone boundary, but these variations are still within the range acceptable in terms of MHD stability of the electrolysis process

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