Research On Numerical Simulation Of The Multi-field In New Mode Cathode Cells

The multi-fields of aluminum reduction cell have significant influenced on the current efficiency and the cell life, so the numerical simulation of the multi-fields in aluminum reduction cells is very important to optimize the conventional cells and the design the new model cells. The mathematical model of electromagnetic field, flow field, temperature field and thermal-stress field was established in the paper. The multi-field of the 160kA conventional and new model cathode (invented by Feng Naixiang of Northeast University) cells was numerically calculated with commercial software ANSYS.The calculated results of the 3D electromagnetic field show that:the current distribution of the conventional cells is similar to those of the new model cathode cells, but in aluminum of the new model cathode cells, the Z Current density decreased, while the X (long axes) Current density of aluminum that is up from the surface of convex cathode increased, in additional, the voltage drop in electrolyte of the new model cathode cells reduces 0.38V, which proves that the new model cathode cells is advantageous in energy conservation;The magnetic distribution of the conventional cells and new model cathode cells is similar, the magnetic line forms a clockwise swirl, and the measured data was consistent with the simulated results.The Lorentz force distribution of the conventional cells and new model cathode cells is differ, but the value is similar, the Lorentz force in aluminum of the conventional cell become higher near the surface of the cathode, while the Lorentz force in aluminum of the new model cathode cells decreased at first, then increased at the concave of cathode, the Lorentz force in electrolyte of the conventional cell become higher away from the surface of the cathode, while the Lorentz force in electrolyte under the anode bottom of the new model cathode cells is evenly distributed, then decreased in gap of the anode.The calculated results of the 3D flow field show that:in the new model cathode cells, the velocity of the aluminum and electrolyte is smaller than the one of the conventional cell, and there is wider zero velocity region; at the interface of aluminum and electrolyte of the new model cathode cells, the peak of Z velocity is smaller and denser, replace the larger and sparser peak of Z velocity at the interface of aluminum and electrolyte of the conventional cells, so it can conclude that the fluctuation of the new model cathode cells is smoother, therefore, the new model cathode cells is steadier.The calculated results of the 3D temperature field show that:the measured data was consistent with the simulated results, the new model cathode cells is cooler because of the bad insulation work of the bottom carbon block, and after designed, the bottom temperature of the new model cathode cells is hearth.The calculated results of the 3D thermal-stress field show that:the stress concentration is at the joints of the convex and the surface of cathode in the new model cathode cells, while the stress concentration is at the ends of long axis of cathode in the conventional cells; in the new model cathode cells, the XZ shear stress concentration is enhanced, but the XY and YZ shear stress concentration is released.In conclusion, the numerical simulations provide an exact and high efficiency method for the multi-field of the new model cathode cells, and have the important references values for project analysis and diagnose.