INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Optimal Design of a Corrugated Wall Photocatalytic Reactor using Efficiencies in Series and CFD
Autor/es:
PASSALÍA, C.; ALFANO, O. M.; BRANDI, R. J.
Lugar:
Jacksonville, Florida
Reunión:
Congreso; AOTs-18: Advanced Oxidation Technologies for Treatment of Water, Air and Soil; 2012
Resumen:
Photocatalytic reactors are devices of proven efficiency in the abatement of gas phase pollutants. Such reactors rely on the properties of a sensitized semiconductor like titanium dioxide. Within the possible geometrical configurations for air treatment, one would typically need the photocatalyst immobilization on a substrate; one of these types is the photocatalytic wall reactor. In order to evaluate de overall performance of these reactors, the concept of efficiencies in series may be used. This methodology allows to evaluate in an independent way all the phenomena and parameters that contribute to the global efficiency of the process. In addition, this treatment makes possible the identification of particular variables to improve the design of the photocatalytic devices. Among the parameters and variables identified as relevant to the different individual efficiencies, one can mention the radiation source, the outer reactor configuration, the inner reactor geometry, the optical properties of the materials, the flow regime and the pollutant kinetics. The approach of efficiencies in series that contribute to the overall device performance was applied to the optimal design of a corrugated wall photocatalytic reactor. The reactor itself consists of a series of triangular section channels, with one inlet and one outlet operating in continuous mode. The goal of the study was to obtain an optimum for the folding angle of the central plate, subject to certain constraints: fixed reactor volume and dimensions, fixed radiation flux and fixed airflow. A simple geometry flat plate reactor was used in a previous stage to obtain intrinsic pollutant kinetics for formaldehyde. Once the kinetic parameters were obtained, they were used in the corrugated reactor modeling. The simulations of the reactor were performed computationally. The entering radiation flux coming from two sets of actinic UV lamps was evaluated through a ray tracing based algorithm written ad hoc. The radiation interchange inside the reactor was modeled by the use of local view factors. The mass balance for the pollutant in the reactor was obtained by using a CFD package in which the radiation boundary conditions, reflection and absorption phenomena were introduced by custom defined functions. The folding angles studied ranged from 10 to 100 degrees. The influence of the fraction of reflected radiation on the incidence efficiency was also studied. The results showed an opposite behavior of the two key variables. On the one hand, the relative catalytic area per unit window area increases drastically when reducing the angle; this is a logical and expected result. On the other hand, the relative incident flux that reaches the triangular channel increases almost linearly. Given that the incidence efficiency comprises the product of the two mentioned variables, there was a maximum identified nearby 20° of folding. The methodology of defining independent parameters to account for the overall reactor performance allowed the identification of key configuration variables aiming at the optimization of designs. The methodology may be applied to any photocatalytic wall reactor geometry.