Abstract
Plasma melting furnaces, as an innovative application of thermal plasma, have seen extremely limited numerical studies of their internal plasma arcs, remaining largely in the nascent stages. Due to the complexity of the material composition, the ultra-high currents and temperatures pose great challenges to the numerical calculation of the plasma arc, especially for plasma melting furnaces with an industrial-scale production capacity of 30 t/d. Therefore, this study uses computational fluid dynamics to deeply investigate the fluid flow and heat transfer of the plasma arc in a single-electrode plasma melting furnace operating at a current of 8000 A and a voltage of 170 V. Special attention is given to the impact of the plasma arc on the bath surface, with additional discussions on the effects of electrode gap and cathode bottom shape. The conclusions show that the plasma arc column exhibits a typical bell-shaped profile, and the reduced radial Lorentz force induces an outward expansion of the relevant parameters. The plasma arc achieves a maximum velocity of 2116 m/s and attains the peak temperatures of 19991 K. The heat transfer efficiency from the plasma arc to the bath surface is about 28 %. An innovative evaluation metric for the effective melting region on the bath surface is proposed, and it is currently circular with a radius of 0.525 m. The electrode gap has a minimal effect on the plasma arc. Enlarging the electrode gap can expand the effective melting region, while also bringing about numerous adverse effects. The graphite cathode with the planar bottom exhibits the optimal performance overall, followed by the cambered surface, with the conical surface showing the worst.
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