CFD modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from X-ray tomography data

Highly porous monolithic alumina columns find a wide variety of applications, including in chromatography, due to increased surface area and good accessibility to the ligands and reduced diffusional hindrances. Several modelling approaches have been applied to describe experimentally observed flow behaviour in such materials, which morphology plays a key role in determining their hydrodynamic and mass transfer properties. In this work, a direct computational fluid dynamics (CFD) modelling approach is proposed to simulate flow behaviour in monolithic porous columns. The morphological structure of a fabricated alumina monolith was first reconstructed using 3D X-ray tomography data and, subsequently, OpenFOAM, an open-source CFD tool, was used to simulate the essential parameters for monoliths' performance characterisation and optimisation, i.e. velocity and pressure fields, fluid streamlines, shear stress and residence time distribution (RTD). Moreover, the tortuosity of the monolith was estimated by a novel method, using the computed streamlines, and yuits value (similar to 1.1) was found to be if the results obtained by known experimental, analytical and numerical equations. Besides, it was observed (for the case of the monolith studied) that fluid transport was dominated by flow heterogeneities and advection, while the shear stress at pore mouths was significantly higher than in other regions. The proposed modelling approach, with expected high potential for designing target materials, was successfully validated by an experimentally obtained residence time distribution (RTD).