Theoretical Investigation of the Inclined Sidewall Design on Magnetohydrodynamic (MHD) Forces in an Aluminum Electrolytic Cell

A mathematical model of magnetohydrodynamic (MHD) effects in an aluminum reduction cell using numerical approximation of a finite element method is presented. In this numerical model, the magnetic field resulting from the cell cathode bus as well as the magnetic field from both downstream and upstream cells are included. The article outlines the three-dimensional simulation of Lorentz force distribution that results from current distribution in both the cathode bus and the cell linings. These forces are important in the side channel of the cell as the current changes its direction because of an inclined sidewall design. Thus, the present work has two main features, which are (1) a numerical model to predict Lorentz field distribution in the electrolytic cell and (2) the influence of sidewall design on current distribution in the side channel and MHD forces. The model predicts that the magnitude of Lorentz force is at its maximum near the sidewall (i.e., along the side channel). The radial component of the Lorentz force creates a concentric rotational flow field, whereas the radial component is responsible for the metal “heave.” Results are obtained for different inclination angles (θ = 50 to 64 deg) of the sidewall insulation and at different pot-line currents (140 kA to 180 kA). The direction of the resultant Lorentz force is greatly influenced by the slope of the sidewall and is important to the convective flow of metal and bath in the cell.