Multiphase behaviors in a multistage vanadium leaching tank with mechanical-vapor combined stirring

Background

The improvement of conventional mixing methods on the problems of uneven solid phase distribution and bottom mineral deposition in multi-stage vanadium-bearing shale agitated leach tanks is limited, and more novel mixing methods need to be proposed and developed.

Method

In this study, vapor-liquid-solid flow, dead-zone buildup and bubble residence time in a multistage vanadium-bearing shale leaching tank with inlet and outlet were numerically investigated and compared. Three different stirring methods, namely mechanical stirring, vapor blowing stirring, and combined mechanical vapor blowing stirring, were used to stir the samples, and different inlet speeds were compared, and the numerical models were validated by water modeling tests.

Significant Findings

The results showed that the combination of mechanical mixing and vapor blowing could reduce the ratio of the "dead zone", in which the top low-concentration zone was reduced from 0.84% to 0.178%, and the bottom deposition zone was reduced from 0.32% to 0.026% compared with only mechanical mixing. Increasing the inlet vapor flow rate would enhance the stirring effect of vanadium shale leaching tank and reduce the residence time of bubble particles in the tank. The minimum residence time of bubble particles was shortened from 10.05 s to 5.95 s, and the peak residence time of bubble particles and the distribution of vapor residence time were improved significantly. The combination of mechanical stirring and vapor blowing was favorable for solid-liquid two-phase leaching reaction. Increasing the flow rate could effectively reduce the effect of bubbles on the mixing of solid-liquid phase.