Numerical Simulation Of Solid-Liquid Two Phase Flow In Dual-Impeller System

Solid-liquid heterogeneous reactions exist extensively in the production process of chemical industry, hence the solid distribution in stirred tank plays a critical role in the reaction process. The performance of solid-liquid suspension in a stirred tank with dual impellers has been simulated numerically by computational fluid dynamics (CFD). The Multiple Reference Frame and Eulerian multiphase flow model have been adopted to simulate the solid-fluid flow. Effects of structure parameters of dual impellers, baffles and material parameters of the research system on solid suspension are analyzed based on the computational results. The main conclusions are as follows:The synergistic effect generated by the combination of two down-pumping pitched blade turbines can efficiently improve the solid suspension performance; Dual impellers with blade angle of 45° and impeller space of 0.5T can generate strong axial flow and turbulent fluctuation with lower energy consumption and hence homogeneous particle distribution can be achieved; Moreover, streamlined dish bottom can well comply with the moving direction of fluid in the stirred tank and thus eliminate dead zone in the bottom.The installation of baffles can effectively eliminate the tangential motion and prompt overall axial circulation in the stirred tank and the best particle suspension quality can be achieved when baffle numbers equal to 4 and the distance from wall is 3.4 mmParticle suspension uniformity in the stirred tank decreases with the increase of particle diameter、particle density and solid volume fraction and it will become worse with less viscous fluids. Meanwhile, it has also been found that compared with single-impeller stirred system, dual-impeller stirred tank is more sensitive to particle density and particle diameter, but its adaptability to solid volume fraction is better.