Using computational fluid dynamics to calculate transversal dispersion in a structured packed bed

Abstract

Structured packed beds filled with catalyst pellets are very useful reactors for heterogeneous or catalytic reactive distillation. The scope is to determine hydrodynamics of liquid in this kind of packing using CFD techniques to eventually describe scale up properties. First a simplifying model, the Toblerone model, is developed. This model simplifies the problem of multiphase flow in structured packed beds to single phase flow in intersecting triangular channels. The model gives an operation window for reactor operation and is a powerful tool to determine design properties. The liquid flow field is solved using the Ergun equation to account for porous flow trough the pellets. In this article the transversal dispersion coefficient is calculated with the Toblerone model. Using this technique it was found that the transversal dispersion coefficient is a factor 40 higher compared to single phase packed bed flow. This number is a reminder that transversal dispersion of the liquid phase in structured packed beds is never the limiting property with design.