Numeerical Simulation Of Solid/Liquid Suspension Process In Stirred Tank

Mixing equipments are widely used in many industry processes. Solid-liquid suspension is one of the most important processes in stirred operations. For the fluid flow in solid-liquid stirred tank, it is important to study velocity distributions for both solid and liquid in the tank, and then to investigate the influence of particle concentration on liquid velocity distribution. The new method of using Computational Fluid Dynamics (CFD) for the study of flow and mixing characteristics in stirred tank is adopted more and more frequently.In this study, based on the function provides by the commercial CFD code (FLUENT), the power curve in a stirred tank has been simulated by means of computational fluid dynamics (CFD) techniques. Different methods have been employed at various Reynolds numbers. The Multiple Frames of Reference (MFR) method was adopted for the simulation. The calculated power curve is consistent with the literature data. Three different methods were used for the simulation of the transition flow region. The simulation result shows that the power number, which was calculated by different methods in this region, was closed to each other.An understanding of the just-suspended speed of impeller, Njs, and the distribution of solids, is critical to the efficient operation of industry processes involving solid-liquid suspensions. In this study, the just- suspended impeller speed, Njs, in solid-liquid stirred tank was predicted using CFD and validated against experimental data obtained from the literature. The investigation was carried out in a fully baffled, flat bottom, cylindrical vessel, with 500mm diameter, equipped with a Rushton turbine. Sand particle were chosen as the dispersed phase. The particle volumetric concentration was 5%. The multiphase flow is modeled using the Eulerian Granular Multiphase model. Two different criterions were used to predict Njs. The CFD predictions are in good agreement with literature data. Solids concentration distribution and the velocity distribution of solids and liquid were predicted. The performance of solids suspensions under different agitation speeds was studied.The local liquid mean velocities were studied by CFD simulation method in a solid-liquid suspension system. The investigation was carried out in a fully baffled, cylindrical, with 800mm diameter, equipped with an axial flow propeller (CBY III) to push the water downward. Sand particles were chosen as the dispersed phase. The particle volumetric concentration was 5.4%. In the jet flow region and the wall region with the solid volumetric concentration being zero and 5.4%, the liquid velocity distributions were simulated at different location to explore the effect of particle concentration on liquid local velocities. The CFD predictions are in good agreement with literature data.