Computational Fluid Dynamics Simulation and Experimental Measurement of Gas and Solid Holdup Distributions in a Gas–Liquid–Solid Stirred Reactor

The lack of convincing computational fluid dynamics models and basic experimental data makes it difficult to design and scale up a gas–liquid–solid three-phase stirred reactor such as in environmentally benign bioleaching processes. In this work, a steady state gas–liquid–solid Eulerian–Eulerian multifluid model was developed to predict flow field and local phase holdup distribution. The measurements of gas and solid holdup distributions in a gas–liquid–solid stirred reactor were simultaneously obtained for the first time by a new improved sample withdrawal technique. The influence of the presence of a second dispersed phase on interphase drag force was taken into account, and good agreement for the local phase holdup was obtained between the predictions and the experimental data. The solid concentration increased, and the gas holdup decreased along the radial direction from the reactor axis to the wall. A simplified bubble-size model considering the effect of turbulence dissipation rate was incorporated in the model instead of a fixed size. It was found that smaller bubbles concentrated in the impeller region, and the bubble size increased near the free surface. The mixing efficiency could be enhanced obviously when double impellers were employed.