CFD Simulation of the Fluid Hydrodynamics in a Continuous Stirred-Tank Reactor

Continuous stirred-tank reactors (CSTR) are widely applied in the chemical, food, and pharmaceutical engineering fields. The micro-scale fluid dynamics are important for the optimal processing study since they have a dominating influence on the overall performance of the reactor. In this article, 3-dimensional Computational Fluid Dynamics (CFD) simulations are carried out to portray the flow characters in the CSTR of the mini-plant of the Collaborative Research Center InPROMPT coordinated by the Technische Universität Berlin. In InPROMPT, the reactor is used to perform a rhodium-catalyzed hydroformylation of long chain alkenes. In this study, cases of a vessel with and without baffles are compared. The results show the existence of a high speed velocity toroidal zone in different horizontal sections in the CSTR without baffles, comparing to the common pervasive conception which is the assumption of a complete uniformity of the fluid velocity magnitude in a CSTR at the final steady state. Moreover, under the rotation speed of 400 rpm, the baffles in the CSTR can significantly prevent the formation of a surface vortex, for the mean tangential velocity magnitude is dramatically decreased. On the other hand, the mean radial and axial velocity is tremendously increased when the baffles are added. Therefore, the baffles in the tank lead to a greater vertical fluid exchange in CSTR. Besides, in the specific domain of CSTR region, both the fluid velocity direction and magnitude carry on a cyclical variation, when the baffles are inserted into the CSTR.