Simulation On Optimization Of Multiphase Flow Behaviors In Stirring Leaching Tank Of Hydrometallurgical Vanadium Extraction

Hydrometallurgical vanadium extraction is a multistage continuous process.There are some problems in the leaching tank,such as uneven distribution of solid phase and too much deposition of minerals at the bottom of the tank,which restrict the leaching efficiency.Therefore,it is of great significance to investigate the multiphase flow behaviors in the leaching tank.In this study,the multi-stage vanadium shale stirred leaching tank was taken as the research object.The multiphase flow field and concentration field in the leaching tank under mechanical stirring and gas-mechanical combined stirring were numerically to improve the operation parameters of impeller and stirring model,and the numerical model was validated by water model experiments.The present study can provide theory guide for higher leaching efficiency.The results were showed as follows:(1)Based on the multiple reference frame(MRF)method,the Euler model is established to simulate the solid-liquid two-phase flow field,concentration field and solid-liquid two-phase flow behavior in the stirred leaching tank.The numerical simulation results are verified by water model experiments,which indicated that the simulated results are basically in good agreement with the experimental results.(2)By changing the speed of the single-layer impeller,the solid-liquid mixing effect was basically the same as that of the double-layer impellers with the same stirring speed.When the speed of the lower impeller increases from 34 rpm to 44 rpm,the concentration of vanadium shale particles in the upper part of the leaching tank is mostly about 0.36,which is basically the same as that of the double-layer impellers stirring with the same speed of 44 rpm.In addition,increasing the speed of the lower impeller can shorten the response time of TMC(Tracer Molar Concentration)curve,increase the peak value of the curve,and save about 72.98 % of the stirring energy consumption.(3)The stirring mode has a significant effect on the multiphase flow field and concentration field in the leaching tank.When the stirring mode changes from only blowing stirring to only mechanical stirring,the flow velocity of vanadium shale in the upper part of the top impeller increases from 0.9 m/s to 1.8 m/s,and the volume ratio of low concentration area of vanadium shale at the top of the tank decreases from 20.54%to 0.84%,and the volume ratio of vanadium shale deposition area at the bottom decreases from 4.88% to 0.32%.When the stirring mode changes to mechanicalblowing combined stirring,the high velocity area of vanadium shale between the stirring blades and near the stirring shaft increases significantly,and the volume ratio of the low concentration area at the top decreases from 0.84 % to 0.178 %,and the volume ratio of the deposition area decreases from 0.32 % to 0.026 %.(4)Increasing the gas inlet velocity will enhance the chaotic behavior of multiphase flow in the leaching tank.When the inlet velocity increases from 20 m/s to60 m/s,the volume ratio of the low concentration area of the top vanadium shale decreases from 1.23 % to 0.032 %,the bottom deposition area decreases from 0.25 %to 0.012 %,and the shortest residence time of bubbles in the tank decreases from 10.05 s to 5.95 s.Meanwhile,the peak of bubble residence time and the distribution of residence time are significantly improved,thus less affecting the interaction between the solid-liquid phases.