Numerical Simulation of Multi-Physics Fields in Fused Magnesia Furnace

In this paper, a 3D transient multi-physical field model is developed to capture the complex processes inside a fused magnesia furnace. The multi-physics model integrates electromagnetism, thermodynamics, decomposition reactions, and flow. The three-phase submerged magnesia furnace includes an arc, magnesite ores, a melting pool, and a solidification ingot. For a more comprehensive analysis of the optimal design of industrial operations, the influence of the key index of electrode insertion depth on temperature and reaction is also discussed. The results show that the current density in the fused magnesia furnace is almost the same as the joule heat distribution, and there is an obvious area of low energy density affected by the skin effect, which leads to the waste of electric energy. The temperature at the center of the arc reaches 12,000 K, and the plasma areas formed at the end of the three electrodes are connected to each other to form a closed current path, which provides energy for the process of melting magnesia. The arc region is an ellipsoid with a length of ~30 mm and a diameter of ~49 mm. The decomposition reaction of magnesite mainly occurs in the arc area, and the radiation heat provided by the high-temperature arc is used as the heat source. There is almost no magnesite in the molten pool, and the molten pool only provides energy for the melting process of magnesia. When the electrode insertion depth is 0.4, 0.5, 0.6, and 0.7 m, the arc length is 0.049 m, 0.066 m, 0.068 m, and 0.059 m, respectively. According to the simulation results, there is an optimal electrode insertion depth.