(539f) Investigation Based On Electric Field to Optimize and Design An Energy-Saving Magnesium Electrolysis Cell

Fused salt electrolytic technology for light metal production is complex process, which includes six important physics fields affecting performance of electrolysis cell, such as electric field, magnetic field, temperature field, flow velocity field, concentration field and stress field. To obtain an advanced electrolysis cell by optimizing the behaviors of these physics fields, Conventional experimental methods have to take a lot of money, time and labor requirements, and have to bear a risk of failure. However, with a great increase of computer power in the last ten years, a novel numerical simulation (FEM) has become an effective tool in the design or modeling of a physical phenomenon in various engineering disciplines with the help of ANSYS®. This approach makes it possible to study the effect of each physics field in isolation and evaluate the electrolysis cell responses to variation of the process and design parameters, relatively successful applications were made in design advanced aluminum reduction cells by optimizing electric field, magnetic field, and temperature field. As is known to us, the cell performance mainly depends on current efficiency and cell voltage including decomposition voltage, excess voltage and resistance voltage, which decide the energy consumption. In order to develop the energy-saving magnesium electrolysis cell by FEM, this paper aimed at optimizing electric field that is energy foundation of operation and source of the other physics fields, mainly focused on investigating how to reducing resistance voltage (Ohmic voltage) by changing cell structure parameters, such as relative positions of anodes and cathodes, et al. Firstly, an investigation based on electric field of magnesium electrolysis cell was employed to optimize a 120 kA cell, where the cell with the dimension 2.91×1.87×1.40 m, 8 anodes with dimension 2.20×1.00×0.15 m, 9 cathodes with dimension 0.950×2.235×0.050 m, and the anode and cathode distance as 0.07 m. The major work was to look for the best cell structure by adjusting the extended distance of cathode relative to anode in the direction toward cell bottom, the extended distance between cathode and back wall, the shorten distance between cathode and cell bottom, the shorten distance between cathode top and electrolyte surface and the extended distance between cathode and partition. In theory, effective work is done in the region between anode and cathode, the least bypass current going into other regions is expected. Comparing figure 1 and figure 2, the voltage potential distributions in regions II and IV are close to desired state. Thus, simulation results indicate that suitable modification of cathode and cell profiles could obtain good resistance voltage distribution. Furthermore, an orthogonal test was conducted to verify the optimum 120 kA cell, and the optimization criterion was applied to the amplification of 250 kA cell. The computed resistance voltage of the optimized 250 kA is also the minimum voltage 1.631312 V among provided solutions, and the potential distributions in region B and D is more perfect than that in regions A and C, which are shown in figure 3 and figure 4. If decomposition and over voltages are 2.735 V, external voltage is assumed 0.25 V, and then theoretical cell voltage could attain 4.616312 V. Comparing with the magnesium electrolyzers in commercial use, this cell is more competitive in energy consumption. Hence, the developed model and simulated results will be useful for optimization and design of the magnesium electrolyzers.