Optimization of mixing behaviors in a multistage vanadium shale leaching tank by a double-layer impeller at different speeds

Abstract

BackgroundMultistage vanadium-containing shale leaching tanks often suffer from uneven solid phase distribution and mineral deposition at the bottom of the tank, leading to low leaching efficiency. MethodsIn this study, the solid‒liquid flow, tracer diffusion and power consumption in a multistage vanadium shale leaching tank with an inlet and outlet were numerically investigated and compared, the samples were stirred by a double-layer impeller with the same and different speeds, and the numerical model was validated by water model experiments. Significant FindingsThe results showed that the maximum velocity near the liquid surface increased from 1.24 m/s to 1.47 m/s and the average velocity increased from 1.15 m/s to 1.24 m/s when the lower impeller speed increased from 34 r/min to 44 r/min. The volume of the low-speed region decreased from 1.15 m3 to 0.63 m3, and the stirring power was reduced by 14.7%. In addition, increasing the lower impeller speed could effectively shorten the response time and increase the peak molar concentration of the tracer. A stirring speed of 34 rpm for the upper impeller and 44 rpm for the lower impeller could achieve good stirring efficiency with proper stirring power.