Scaling Up of a Photoreactor for Formic Acid Degradation Employing Hydrogen Peroxide and UV Radiation

A model for scaling up a homogeneous photoreactor was developed and experimentally verified in a pilot-plant-size apparatus. The procedure is exemplified by the oxidation of dilute aqueous HCOOH solutions with UV radiation (254 nm) and H2O2. First, the kinetic model and the kinetic parameters of the HCOOH degradation were obtained in a well-stirred, small, batch flat-plate photoreactor (volume=70 ml). The method employed in the analysis of the experimental results yielded reaction-rate expressions for HCOOH and H2O2 that were independent of the reactor configuration. These kinetic equations and the corresponding kinetic constants were then used in a mathematical, fully deterministic model of a continuous-flow, 2-m-long, annular reactor (0.0065 m2 of cross section for flow) operating in a laminar-flow regime to predict exit concentrations of HCOOH. Irradiation was provided in both cases by two different types of germicidal lamps. No additional experiments were made to adjust the reactor-model parameters. Theoretical predictions from the representation of the reactor performance obtained were compared with experimental data furnished by experiments in the much-larger-size, cylindrical-flow reactor. Results showed good agreement for the range of variables explored; they corresponded to expected operating conditions in water streams polluted with low concentrations of organic compounds.