Meso-scale CFD study of the pressure drop, liquid hold-up, interfacial area and mass transfer in structured packing materials

This work presents a meso-scale CFD methodology to describe the multiphase flow inside commercial structured packings for post-combustion CO₂ capture.Meso-scale simulations of structured packings are often limited in the literature to dry pressure drop analyses whereas mass transfer characteristics and gas-liquid interface tracking are usually investigated at micro-scale. This work aims at testing further capabilities of meso-scale modeling by implementing the interface tracking instead of analyzing only the dry pressure drop performance with single-phase simulations. By doing so, it is possible to present also the hydrodynamics (i.e. liquid hold-up and interfacial area) for a small set of representative elementary units (REUs). The interest in interface tracking using commercial geometries lies on the fact that liquid hold-up and interfacial area have implications of capital importance on the overall performance of the absorber, hence the importance of developing a model to predict them accurately. The results show how the relationship, reported in the literature, between the liquid load and both the liquid hold-up and the interfacial area is reproduced by the present CFD methodology. Also, a more realistic visualization is accomplished with images of the inner irregularities of the flow (i.e. liquid maldistribution, formation of droplets and rivulets, etc.), which lie far from the prevailing assumption of the formation of a perfectly developed liquid film over the packing.Moreover, the effect of operating parameters such as the liquid load, liquid viscosity and liquid-solid contact angle on the amount of interfacial area available for mass transfer is also discussed.Finally, mass source terms are also included to describe the gas absorption into the liquid phase hence testing all the capabilities of micro-scale modeling at meso-scale. The present model could be further used for the analysis and optimization of other structured packing geometries.