Preparation of High-Purity Vanadium Metal by Iodide Refining Based on Numerical Simulation Using SIMPLE Algorithm

In this study, the iodide refining of high-purity vanadium metal was investigated experimentally and by two-dimensional numerical simulations based on the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm. The effects of system temperature, K values (characterizing the deposition filament temperature), initial iodine amount, and raw material packing configuration on the deposition rate, crystal morphology, and mass transport were studied in a custom-built iodide apparatus. The experimental results showed that the deposition rate exhibited a bell-shaped dependence on the source temperature. The optimal source temperature and optimal K value were 1123-1173 K and 40-50, respectively, at which the average deposition rate reached its peak. Both the average deposition rate and the average reaction time increased slightly with increasing initial iodine amount, but the increases were limited. Full loading of the raw material yielded crystal rods of uniform size. Vanadium crystal rods with a diameter of approximately 20 mm were obtained after refining. The metallic impurities Fe, Cr, Al, and Si were reduced to 0.025-0.033 wt.%, <0.001 wt.%, <0.001 wt.%, and <0.002 wt.%, respectively, while the interstitial impurities O, C, and N were reduced to <0.01 wt.%, <0.002 wt.%, and <0.002 wt.%, respectively, indicating that iodide refining can effectively reduce the contents of both interstitial and metallic impurities in vanadium metal. Numerical simulation results showed that the mass transport rate decreased monotonically with increasing total pressure, increased with rising temperature owing to the enhanced VI₂ partial-pressure difference, and decreased with increasing transport distance. The flow pattern transitioned from pure diffusion/advection at 300 Pa to transitional vortices at 1000 Pa, and finally to fully developed recirculation at 3000 Pa. The simulation results are qualitatively consistent with the experimental observations, providing a theoretical basis for process optimization. To further improve the purity and scale-up potential of the process, it is necessary to conduct more in-depth research, including the development of fully coupled models that incorporate gas-phase dissociation, non-equilibrium surface kinetics, and composition-dependent mixture properties, as well as three-dimensional simulations and reactor material optimization.