Micromixing efficiency optimization of the premixer of a rotating packed bed by CFD

Rotating packed bed (RPB) as an HiGee process intensification reactor can provide high micromixing efficiency, which is essential for fast reactions in fine chemicals, pharmaceutical and crystallization fields. In this paper, a Computational Fluid Dynamics (CFD) model is developed to investigate the micromixing efficiency in the premixer and packing zone of an RPB based on Villermaux-Dushman reaction system and a modified Finite-rate/Eddy dissipation micromixing model. The numerical results agree well with the experimental data in the literature on the liquid flow pattern and segregation index X_S. An important model constant A_m is obtained after the validation of CFD model, which shows correlation with the liquid viscosity. It is shown that better micromixing efficiency could be achieved using higher liquid flow rate, lower viscosity or higher rotational speed. Shorter premixer and smaller inlet diameter ratio can improve the micromixing efficiency at μ = 1.0cp, and longer premixer and larger inlet diameter ratio is a better combination at μ = 219.2cp. Cross flow mixing angle could reduce the segregation index X_S in both cases. Finally, guiding principles are proposed for designing the premixer for systems with different viscosities, which can be employed for premixer optimization in order to improve the micromixing efficiency of RPBs.