Design optimization of plasma generator for refractory metal purification

High-purity refractory metals are recognized as critical raw materials supporting the development of the advanced electronic information industry. However, mainstream purification methods such as electron beam melting and plasma arc melting are generally plagued by technical limitations, including limited removal efficiency of gaseous impurities and high susceptibility of electrodes to contamination. Inductively coupled plasma melting(ICPM) technology is proven to effectively overcome these drawbacks, thus emerging as a highly efficient and clean purification approach. As the core component of ICPM equipment, the rationality of the structural design of the plasma generator directly determines the stability and continuity of the ICPM purification process. Therefore, numerical simulations are first carried out via Fluent software to optimize the key structural parameters of the generator. Results demonstrate that a stable and symmetrical vortex zone as well as an optimal flow field with uniform cooling can be formed inside the generator when the number of central gas inlet holes is set to 8, the incident angle of the inlet holes is 8°, and the diameter of the cooling gas inlet slot is 6 mm. Furthermore, a magneto-thermal-fluid multi-field coupling model is established by means of COMSOL software to investigate the influence laws of process parameters(including coil power, central gas flow rate and cooling gas flow rate) on the plasma temperature field and flow field. It is found that the enhancement of coil power and central gas flow rate can significantly strengthen the plasma jet intensity and elevate its temperature. In contrast, a critical threshold exists for the cooling gas flow rate; beyond this threshold, a further increase in the flow rate will instead lead to the reduction of plasma jet intensity and temperature. Results of experimental verification indicate that the plasma generator designed achieves stable operation, and the measured morphology of the plasma torch shows high consistency with the simulation results. Conclusions drawn from the work are expected to provide scientific basis and technical support for the engineering design of plasma generators for ICPM equipment.