TiO 2 absorption and scattering coefficients using Monte Carlo method and macroscopic balances in a photo-CREC unit

Abstract

The radiation field inside photocatalytic reactors can be predicted by solving the Radiative Transfer Equation (RTE). From the solution of the RTE, the Local Volumetric Rate of Energy Absorption ( LVREA) can also be obtained. This LVREA is an important parameter in photocatalytic reactor design, energy efficiency assessments and kinetic studies of photocatalytic reactions. However, when solving the RTE, two optical parameters are needed: (1) the absorption and scattering coefficients and (2) the phase function. In the present study, the Monte Carlo (MC) method along with an optimization technique is shown to be effective in predicting the wavelength-averaged absorption and scattering coefficients for three different TiO 2 powders. To accomplish this, the LVREA and the transmitted radiation ( P t ) in a Photo-CREC annular photoreactor have to be determined using a macroscopic balance. The optimized coefficients are calculated ensuring that they comply with a number of physical constrains, falling in between bounds established via independent criteria. The optimization technique is demonstrated by finding the absorption and scattering coefficients for three different semiconductors that best fit the experimental values from the macroscopic balance minimizing the least-squared error of objective functions for the LVREA and P t . The proposed approach is a general and promising one, not being restricted to reactors of concentric geometry, specific semiconductors and/or particular photocatalytic reactor unit scale.