Dense Phase Mixing in a Solid-Liquid Stirred Tank by Computational Fluid Dynamics Simulation

This study numerically investigates the solid–liquid mixing characteristics in solid–liquid stirred tanks with solid volume fraction as high as 35%, focusing on the effect of impeller and baffle configurations on solid and liquid flow behaviors. Three stirred tanks with different capacities and impellers were analyzed to evaluate liquid flow field, solid suspension, and free surface profiles. It has demonstrated superior shear rate uniformity in the multi-impeller systems compared to the single-impeller, attributed to the enhanced fluid circulation. Multi-impeller systems can achieve near-complete off-bottom suspension, while the single-impeller configuration exhibited band-shaped particle accumulation above the impeller. Free surface vortices, significantly deeper in the 6 m3 multi-impeller tank due to high blade tip velocities, were mitigated through the integration of four circumferentially arranged triangular baffles. The existence of baffles can suppress surface turbulence, promote axial flow patterns, and eliminate particle accumulation at the tank bottom, improving shear rate and solid concentration homogeneity. These findings provide a beneficial guideline for the optimization of solid–liquid mixing efficiency the similar flow system or processes.