Kinetic characterization of phosphorus removal from the surface of metallurgical grade (MG) silicon droplets during electromagnetic levitation

Abstract

In this study, the kinetic mechanism of phosphorus atoms removal under partial pressure condition was analyzed by developing a full-domain control model of phosphorus migration behavior in the liquid phase, at the liquid-gas interface, and in the gas phase. Simultaneously, the dephosphorization experiments of metallurgical grade silicon by electromagnetic levitation in different melting time and temperature were investigated to verify the model results. The results show that the limiting step for phosphorus atoms removal at lower melting temperatures (<1800 K) is the evaporation of phosphorus from the surface under finite vacuum conditions. When the system temperature increases (>1900 K), the limiting step becomes to phosphorus atoms diffusion within the boundary layer of liquid phase. In the melting temperature range 1823–2123 K, the total mass transfer coefficient predicted by EML refining model for P removal from Si melt has the following relationship with temperature: lnk(P)=−8.49−12609/T.