Modelling of a Multi-annular Photoreactor for the Degradation of Perchloroethylene in Gas Phase

IMOBERDORF, G.E.; IRAZOQUI, H.A.; CASSANO, A.E.; ALFANO, O.M.

Río de Janeiro, Brasil

Congreso; 2º Congreso de Ingeniería Química del Mercosur y 4º Congreso del Mercosur de Ingeniería de Sistemas y Procesos - ENPROMER 2005; 2005

Universidade Federal do Rio de Janeiro, Brazil

A number of volatile chlorinated organic compounds are used industrially as solvents in operations of dry cleaning and degreasing of metals. Among them, tetrachloroethylene or perchloroethylene (PCE) is a toxic and carcinogenic agent, highly persistent in the environment. Photocatalytic reactions using TiO2 as the catalyst are an effective means for its elimination. Photoreactors design requires knowing the mechanism and kinetics of the photocatatalytic reactions involved, including the steps describing the interaction of the radiation field with the catalytic surface. In previous work, the degradation of PCE in an air stream was studied for different values of PCE feed concentrations, relative humidity and irradiation levels in a flat-plate reactor without mass limitations. An expression of the intrinsic reaction kinetics was developed. This expression allows us to design a reactor with cylindrical geometry and mass limitations. Four borosilicate glass tubes (UV transparent) were placed concentric each other, forming annular channels, where the polluted air flows. A black-light UV lamp was placed in the center of them. The TiO2 catalyst was immobilized to the tubes walls using a sol-gel technique. The thickness of the TiO2 films was adjusted to allow to the UV radiation to reach all the reactor walls. The reactor presents a good effectiveness in the PCE degradation A radiation model was developed to predict the Local Superficial Rate of Photon Absorption (LSRPA) in each point of the reactor, value that is necessary to evaluate the reaction rate. A 2-D mass transference model was developed taking account the kinetics model developed, mass limitations and the radiation model. The predictions show a good agreement with the experimental results.