Modelling of TiO2-based packing bed photocatalytic reactor with Raschig rings for phenol degradation by coupled CFD and DEM

As an alternative to the photocatalyst research, it is a promising approach by optimizing the macrostructure and reaction conditions to improve the photocatalytic performance of the TiO2-based packing bed photocatalytic reactor with Raschig rings. In this work, a packing bed photoreactor model with Raschig rings for the phenol degradation in wastewater is proposed based on the coupled computational fluid dynamics (CFD) and discrete element method (DEM), and verified by the experimental data. The multi-physical fields are presented and the photocatalytic performances are analyzed. The results show that the close cells perpendicular to the axis of the container, derived from the rings, lead to the weakened photocatalytic performance. However, the lower particle Reynolds number is favorable to the photocatalytic performance. The total decomposed phenol increases by 100.8% as the incident irradiation increases from 25 to 100 W/m(2), and by only 11.4% from 100 to 200 W/m(2). Besides, the photocatalytic reaction rate increases with reducing the diameter ratio of the rings to container and increasing the thickness of rings. As the aspect ratio of rings increases from 0.25 to 1.25, the outlet phenol concentration decreases by 10% after 30 min of reaction. This work could fill the knowledge gap between the unstructured geometry generation technologies and the real-geometry-based CFD modelling of packing bed photoreactors.