Numerical simulation of melt convection in a dual-electrode arc furnace for MgO production

Abstract

DC electric arc melting is emerging as a promising technology for production of fused MgO. The dual-electrode DC electric arc furnace (EAF), an alternative design using an anode and cathode electrode instead of a three phase AC arc furnace, is investigated using computational modelling methods. Since the thermal field of the EAF is significantly influenced by the electromagnetic stirring of the molten bath, the melt convection are investigated with different electric currents and bath dimensions. Only a quarter 3D symmetry sector is considered for the analysis. The coupled non-linear conservation equations for mass, momentum, energy and electrical charge are solved with the commercial software ANSYS. The calculated flow field indicates that the melt convection is fully turbulent when the electric current reaches the rated value. The Lorentz force is the dominating driving force for the convection, and the mean velocity is almost a linear function of the Lorentz force. According to the Richardson number, the buoyancy becomes more important when the bath volume grows and the electric current decreases, and the Lorentz force becomes more important when the bath volume shrinks and the electric current increases. In order to make a comparison of magnetic stirring between DC and AC modes, 50 Hz AC power is assumed to supply the dual-electrode EAF. The time-averaged Lorentz force is computed in the time-harmonic analysis for the AC mode. It is found that the Lorentz force distribution is the same if the effective value of the AC current is equal to the DC current.