Numerical Simulation Of Mixing Process In A Stirred Tank

Mechanically agitated reactors are widely used in many industrial processes. Mixing time is one of the key parameters to the design of stirred reactors. Only a few studies were carried out on the numerical simulation of mixing process by using computational fluid dynamics (CFD). The mixing time in the stirred tank of 0.476m diameter with single and dual impellers was studied respectively by using CFD package FLUENT6.0. Rushton turbine and three narrow blade hydrofoil CBY impeller were used in the simulation. The multi-reference frame (MRF) and standard k－ε turbulent model were used in the simulation. For the single impeller agitator, the mixing time predicted by CFD is in a good agreement with the experiment. For the dual impeller agitator, the mixing time of dual CBY impeller predicted by CFD is in a good agreement with the experiment, the mixing time of dual Rushton turbine predicted by CFD is about two times that of experiment. The effects of tracer feeding and detecting positions on mixing time were also investigated. The simulation results indicate that the mixing process is dominated by the flow field in the stirred tank. Feeding and detecting positions have important effect on mixing time. Feeding of tracer at the impeller region has a much shorter mixing time than at the liquid surface. The results are of importance to the optimum of industry stirred reactors.