CFD Simulation and Experimental Study of Liquid Dispersion in Randomly Packed Metal Pall Rings

Abstract

The radial dispersion of liquid phase in a large scale packed column (0.6 m diameter) filled with 25.4 mm metal Pall rings was studied in terms of liquid radial concentration profiles using a tracer technique. The effects of operating condition and liquid distributor design on liquid dispersion at different packed bed heights were investigated. It was found that the effect of gas flow rate is most significant, especially above the loading point. The extent of radial mixing in the liquid phase was found to increase with the gas flow rate. To simulate the liquid dispersion in a random packed column, a set of volume averaged equations for the hydrodynamics and mass transport has been solved with the commercial Computational Fluid Dynamics (CFD) software, CFX4.2. The empirical correlations for the two-phase flow pressure drop, inter-phase interaction, and mass dispersion have been incorporated into the volume averaged equations to provide the closure relations. The spatial variation of void fraction in packed beds due to inhomogeneity of the bed, particularly near the wall has also been included in the models. This approach can be used to predict the flow and concentration development in both radial and axial directions taking into account different radial and axial dispersion. The simulation results agree well with the experimental data. Capturing these features is an important first step in building a Computational Fluid Dynamics based mass transfer model to study distillation and absorption in packed columns.