Full-Scale CFD Modeling of Multiphase Flow Distribution in a Packed-bed Absorber with Structured Packing Mellapak 250Y

A full-scale multi-environment Eulerian CFD model for a countercurrent packed-bed absorber with structured packing Mellapak 250Y was built in ANSYS Fluent 2019 R1 in order to model CO2 capture using physical solvents. The objective of the model is to predict the overall absorber gas-liquid internal flow profiles within the complex packing geometry, while accurately predicting the hydrodynamic parameters, such as liquid holdup and pressure drop. The gas-solid and gas-liquid drag coefficients were fitted and validated using the following experimental data by Green et al. (2006. “Hydraulic Characterization of Structured Packing via X-ray Computed Tomography”; 2007. “Novel Application of X-ray Computed Tomography: Determination of Gas/liquid Contact Area and Liquid Holdup in Structured Packing.” Industrial & Engineering Chemistry Research 46: 5734–53.): dry pressure drop, irrigated pressure drop, and liquid holdup. The validated CFD model was used to study the effect of liquid distributor design on the liquid distribution in the absorber using three distributors provided with seven, thirteen, and twenty orifices of 0.2 mm diameter. The CFD model predictions revealed that the distributor with the largest number of orifices resulted in the least liquid maldistribution in the absorber, which led to increasing the overall CO2 absorption efficiency in Selexol as a physical solvent. Also, the overall CO2 absorption efficiency decreased with increasing the superficial liquid velocity due to the shorter contact times between CO2 and Selexol in the absorber at higher superficial liquid velocities.