2-FLUX RADIATION-FIELD MODEL FOR AN ANNULAR PACKED-BED PHOTOCATALYTICOXIDATION REACTOR

One of the remaining challenges in application of heterogeneous photoc atalysis for treatment of air streams containing dilute VOCs is to des ign a cost-effective photocatalytic reactor that simultaneously allows efficient contact of the contaminated air and solid catalyst while un iformly irradiating the solid catalyst with light. A pseudohomogeneous model was developed to study effects of system parameters on process performance for a gas - solid lamp-in-tube annular-photocatalytic-oxid ation (PCO) reactor in which the annular space is filled with photocat alyst-coated packing. In this model the flow field is assumed to be un iform and radial diffusion negligible. Homogeneous reactions are negle cted. Heterogeneous reaction rates follow Langmnir-Hinshelwood-Houghen -Watson kinetics with rate parameters extracted from independent exper iments. A I-D ''two-flux'' incidence submodel is used to account for t he radial UV light distribution throughout the reactor annular space. This submodel requires knowledge of the UV lamp radiant emittance, the optical characteristics of the catalytic thin-film coating, and the U V irradiance at the outer wall of the reactor and contains only a sing le adjustable parameter - the mean free path between photon - catalyst interactions. The model was validated with experimental performance m easurements for destruction of acetone and isopropyl alcohol in a benc h-scale photoreactor. The validated model can be used to predict the o ptimum catalyst film thickness for given reactor dimensions, packing s hape and size, and VOC abatement problem.