Columns with structured packings are frequently used to treat acid gases (CO2, H2S) contained in natural gas. In the future, their use is likely to be extended to the CO2 recovery from flue gases with the development of carbon capture/use/storage processes.

Packings are also used in distillation processesgas production or biogas purification. In these columns, the liquid phase, tasked with capturing the unwanted gases flows over the packing plates, which have a complex geometry designed to maximize the exchange surface.

In order to develop optimized geometries, numerical hydrodynamics calculations are used to reproduce wetting phenomena. The latter have an impact on liquid film flows on complex surfaces, due to the development of dry zones and hence “contact lines” (three-phase), the dynamics of which need to be taken into account.

A CFD (Computational Fluid Dynamics) methodology has been developed to simulate these liquid flows. Since wetting is dependent on nanometric-scale phenomena and given that it is impossible to numerically solve equations on this scale, it was examined from a dynamic contact angle, calculated using a subgrid model(1).

The results have been validated in the case of a 3D sliding droplet (figure).

Simulation d’une goutte glissant sur un plan incliné menant à une instabilité capillaire
Simulation of a drop sliding down an inclined plane
leading to capillary instability(1).

Film thickness and interfacial velocity values, obtained using specially developed methods, will enable validation of calculations for structured packing plates. Measurements and calculations will then be reproduced on an arrangement of several plates.

This new CFD methodology marks a key step in the development of predictive models for the flows considered. Ultimately, it will be useful for the design of new packing geometries, with a view to improving the performance of gas/liquid contactors.

* Thesis entitled “Study of dual-phase flows and wetting in structured packings

(1)  Z. Solomenko, P. D.M. Spelt, P. Alix, J. Comput. Phys. 348 (2017) 151-170.
DOI: 10.1016/j.jcp.2017.07.011

Scientific contact: pascal.alix@ifpen.fr