Computational modelling of a photocatalytic UV-LED reactor with internal mass and photon transfer consideration

Abstract

Photocatalytic breakdown of organic pollutants was modelled and experimentally validated using phenol as probe molecule and UV-LEDs as the radiation source. A nanocrystalline TiO2 film was immobilized in a quartz continuous parallel plate reactor and illuminated by an array of 88 LEDs, each emitting 375nm radiation. The degradation of phenol in steady state conditions was recorded for different irradiances and a pseudo first order reaction rate constant was obtained for this process. The rate constant was found to be of the order of 10−4s−1. A computational fluid dynamics (CFD) coupled with reaction model for the studied reactor was developed. The model considers the catalyst coating as a porous medium instead of a surface. It accounts for the mass transfer and light penetration within the immobilized catalyst. The model has one degree of freedom which was validated for different light intensities and flow rates. The degree of freedom in the model can be defined as “rate of free radical generation” and the unit is molL−1s−1. This variable was experimentally coupled by a linear relation to the irradiance on the catalyst coating. Photonic efficiency of the system was also investigated. A photonic efficiency range of 0.44–1.4% was obtained at light intensities of 2000 and 200μWcm−2, respectively. The model and the data obtained are scalable and applicable to different reactors. Comparison of photonic efficiencies obtained, show that the immobilized TiO2 reactor has similar efficiency to referred works which considered slurry reactors.