EFFICIENCY EVALUATION IN A FIXED-BED PHOTOCATALYTIC REACTOR. RADIATION MODELING USING THE MONTE CARLO METHOD

MANASSERO, A.; SATUF, M. L.; ALFANO, O. M.

San Diego

Conferencia; 19th International Conference on Semiconductor Photocatalysis and Solar Energy Conversion; 2014

Redox Technologies Inc.

Photocatalytic slurry reactors with suspended TiO2 particles are the most common type of reactors employed for research purposes. However, for practical applications, reactors with immobilized catalyst are preferred: no separation of catalyst particles is needed, and they allow operation under continuous mode. The main drawback of immobilized systems is the low area-to-volume ratio, which generally leads to mass transfer limitations and low reaction rates. This disadvantage can be overcome by proper reactor design. Maximum utilization of radiation is crucial to obtain efficient configurations of reactors with immobilized catalyst. In this work, the radiation model of a photocatalytic reactor filled with TiO2 coated rings is presented. The efficiency of the reactor for the degradation of an endocrine disrupting compound, clofibric acid (CA), is evaluated under different operating conditions. Experimental runs were carried out in a cylindrical reactor (diameter: 5 cm; length: 2.75 cm) irradiated from one side through a circular flat window. The reactor was filled with 5  5 mm glass rings coated with TiO2 P25 (Evonik). UV radiation was provided by a halogenated mercury lamp (150W Powerstar HQI from OSRAM). The incident radiation flux, experimentally measured by ferrioxalate actinometry, was 1.52  10-8 Einstein/(s cm2). The reactor operates in a closed recirculating circuit driven by a peristaltic pump. The reactor volume was 54 mL and the total volume, 1000 mL. Experiments were carried out employing glass rings with 1, 3 and 5 catalyst coatings, and different levels of irradiation (100%, 62%, and 30%). The performance of the reactor was objectively assessed by the quantum efficiency parameter, which relates the moles of pollutant degraded per mol of absorbed photons in the reactor. The Monte Carlo method was applied to know the spatial distribution of radiation absorption in the reaction space. This method uses randomly generated numbers to determine the trajectories and fates of all photons that arrive at the reactor window from the lamp. The reactor length was divided into spatial cells to store the number of photons absorbed in each cell and subsequently calculate the local superficial rate of photon absorption (LSRPA). Highest efficiencies were obtained in the reactor containing rings with 3 catalyst coatings and under 62 % irradiation level.