Numerical simulation on micromixing of viscous fluids in a stirred-tank reactor

Micromixing of viscous systems in a stirred-tank reactor with Rushton turbine is investigated numerically. It is characterized by the product selectivity of parallel competitive reactions. Flow fields inside the reactor are determined by the Reynolds Stress Model (RSM). A computational fluid dynamics (CFD) method combining the standard E model and Finite-Rate/Eddy-Dissipation (FR/ED) model is implemented and is validated using experimental data in the literature. The simulations show that a higher agitation speed, a lower fluid viscosity and/or a feeding location closer to the discharge area of the impeller favor micromixing and the reaction rate. The trajectory of the reaction plume also influences the micromixing performance. The value of the FR/ED model parameter determined by lab-scale experiments decreases with increasing fluid viscosity. However, it is little affected by the agitation speed. These results provide useful guidelines for the scale-up of industrial reactors with complex chemical reactions.

► We study the micromixing of viscous fluid in a stirred-tank reactor.
► We combine the standard E model and Finite-Rate/Eddy-Dissipation model in CFD.
► Better micromixing prefers higher agitation speed and lower fluid viscosity.
► Feeding location and reaction zone trajectory also impact final product selectivity.