Modeling and CFD simulation of flow behavior and dispersivity through randomly packed bed reactors

Packed bed reactors (PBRs) are multiphase reactors in which gas and liquid phases flow over a solid packing. PBRs find widespread use in petroleum refining, chemical and process industries, pollution abatement and biochemical industries. In this paper numerical study of flow behavior through random packing of non-overlapping spheres in a cylindrical geometry has been carried out using a commercially available computational fluid dynamics package (FLUENT). Dimensionless pressure drop was studied for a fluid through randomly packed bed at different Reynolds numbers based on pore permeability and interstitial fluid velocity. Numerical solution of Navier-Stokes equations in a three-dimensional randomly porous packed bed illustrated that the results are in good agreement with those of reported by Macdonald et al. (1979) in the range of Reynolds number studied. By injection of solute into the system, the dispersivity over a wide range of flow rate has also been investigated. The simulation results have been evaluated by comparing with published experimental results in term of dispersion coefficient. It is shown that the lateral fluid dispersion coefficients in randomly packed beds can be estimated by comparing the concentration profiles of solute obtained by numerical simulations and those derived analytically by solving the macroscopic dispersion equation for the present geometry. (c) 2008 Elsevier B.V. All rights reserved.