Scale-Up Methodology for Bench-Scale Slurry Photocatalytic Reactors Using Combined Irradiation and Kinetic Modelling

The present study focuses on developing a predictive methodology to scale-up a slurry annular photoreactor using a TiO2 Degussa P25 from the bench-scale to a pilot-plant scale. The bench-scale photoreactor is a Photo-CREC-Water II, a 2.65 L internally-irradiated slurry annular photocatalytic reactor. The pilot-plant scale photoreactor is a Photo-CREC Water Solar Simulator, a 9.8 L pilot-plant photoreactor, externally irradiated by eight lamps. The adopted methodology allows the independent validation of radiative and kinetic models avoiding cross-correlation issues. The proposed approach involves two Monte Carlo methods, to model the Radiative Transfer Equation (RTE) inside each photoreactor. With this end, a novel probe is developed to measure irradiance at different radial positions for improved RTE parameter estimation This allows determining both adequate boundary conditions in the photo-CREC-Water II unit as well as establishing a phase function for Degussa P25 TiO2. On the other hand, a kinetic model and kinetic parameters are established by carrying out photocatalytic degradations of a model pollutant (Oxalic Acid). Kinetic experiments are developed at different photocatalyst concentrations and various irradiance conditions. Additionally, convective and dispersive transport models are proposed and solved by Finite Element (FE) Method to determine the photocatalyst irradiation time in each photoreactor unit and ultimately to predict the overall photocatalytic efficiency. Finally the kinetic-irradiance based model is validated. This is done by predicting irradiance profiles and degradation rates at different photocatalyst concentrations and irradiance conditions on the larger Photo-CREC Water III (Photo CREC Water Solar Simulator) photoreactor

Efficiency Factors in Photocatalytic Reactors: Quantum Yield and Photochemical Thermodynamic Efficiency Factor

Photocatalytic efficiency is evaluated using quantum yields (QYs) and the photo- chemical thermodynamic efficiency factor (PTEF). The PTEF allows establishing reactor efficiency as the ratio of utilized enthalpy for the formation of consumed OH. free radicals over the absorbed photon energy. A key consideration for the evaluation of efficiency factors is the establishment of macroscopic energy balan- ces together with an accurate assessment of evolved and absorbed photons. Of considerable help are the experimental devices developed at the Chemical Reactor Engineering Centre (CREC)/University of Western Ontario (UWO) laboratories. Photoconversion kinetics is required for calculation of the OH. consumption rates and establishment of the related kinetic parameters. PTEFs and QYs have been applied by CREC-UWO researchers for efficiency calculations in photocatalytic reactors for the decontamination of air, water, and hydrogen production

Annual Optical Performance of a Solar CPC Photoreactor with Multiple Catalyst Support Configurations by a Multiscale Model

In this work, the seasonal and yearly optical performance of supported catalyst CPC solar photocatalytic reactors has been theoretically analyzed. A detailed model for the optical response of the anatase catalyst films is utilized, based on the characteristic matrix method, together with Monte Carlo ray tracing simulations. The catalyst is supported over glass tubes contained inside a larger glass tube that functions as receiver of the CPC reflector. Arrangements with four, five, and six tubes are considered. Overall, the four-tube scenario presents the worst performance of all, followed by the five-tube case. In general, the six-tube configuration is better. Nevertheless, important differences can be observed depending on the specific arrangement of tubes. The six-tube case surpasses the absorption rate of all the other configurations when the distance between tubes is extended. This configuration exhibits 27% increased yearly energy absorption with respect to the reference case and 47% with respect to the worst case scenario

Efficiency Factors in Photocatalytic Reactors: Quantum Yield and Photochemical Thermodynamic Efficiency Factor

Photocatalytic efficiency is evaluated using quantum yields (QYs) and the photo- chemical thermodynamic efficiency factor (PTEF). The PTEF allows establishing reactor efficiency as the ratio of utilized enthalpy for the formation of consumed OH. free radicals over the absorbed photon energy. A key consideration for the evaluation of efficiency factors is the establishment of macroscopic energy balan- ces together with an accurate assessment of evolved and absorbed photons. Of considerable help are the experimental devices developed at the Chemical Reactor Engineering Centre (CREC)/University of Western Ontario (UWO) laboratories. Photoconversion kinetics is required for calculation of the OH. consumption rates and establishment of the related kinetic parameters. PTEFs and QYs have been applied by CREC-UWO researchers for efficiency calculations in photocatalytic reactors for the decontamination of air, water, and hydrogen production

Effective radiation field model to scattering – Absorption applied in heterogeneous photocatalytic reactors

A new mathematical model for the calculation of the radiation field in heterogeneous photocatalytic reactors using the new concept of ‘‘effective radiation field model’’ or ERFM is proposed. In this concept, the incident radiation associated to the photons flow is an energy cloud. The generated space-phase and the properties of the cloud are considered isotropic and independent of the propagation angle and photon frequency. The isotropic nature of the ERFM concept provides a simple estimation of the radiation field of a catalyst in suspension (particles and fluid) for polychromatic radiation and the solar spectrum. The ERFM is an alternative model for the calculus of the radiant energy distribution in heterogeneous photocatalytic reactors as an extension of concept to the overall volumetric rate photon absorption – OVRPA. The local volumetric rate of photon absorption (LVRPA) predicted by the ERFM were compared with the Six Flux Model (SFM) and the rigorous solution using Discrete Ordinate Method (DOM) for the radiative transfer equation (RTE). The calculated LVRPA with the ERFM was found to be closer to the solution of the RTE-DOM. These results were attributed to the performance of the phase function in both models