Modelling of NO photocatalytic degradation in an experimental chamber

Almost real-life experiments of abatement of a pollutant, actually nitrogen monoxide, were carried out in a 10m3 chamber, the walls of which were covered with plasterboard samples, themselves coated with a photocatalytic dispersion. The experimental protocol consisted in first injecting NO polluted air into the chamber to a certain level, then maintaining a steady level of pollution by tuning the flow rate to balance the leaks and, finally, illuminating the chamber. In a first stage of analysis, a three-flow (injection, leakage and renewal flows) model was used in order to characterize the leakage flow rate. This model was based on the difference of NO concentration between the interior and the exterior rather than on a pressure difference. A two-parameter empirical law was specially formulated for this purpose. In a second stage, the photocatalytic phenomenon was described by a four-flow model completing the previous one, the fourth flow being associated with the photocatalytic oxidation of NO. This flow was described by a rate law derived from the Langmuir-Hinshelwood (L-H) law, which was generalized to the experimental chamber. The parameters K (adsorption constant) and k (abatement kinetics constant) of the rate law were identified using a standardized lab-scale reactor. The equations, integrated by finite differences, fitted the experimental results correctly. The diffusive zone thickness was introduced as the thickness of the air layer potentially concerned by the photocatalysis and was quantified. This first attempt to model photocatalysis on a large scale was promising. However, further research work is needed to enable the model to take more parameters into account.

Automated summary

Real-life experiments were conducted in a 10m3 chamber to study the abatement of nitrogen monoxide. Two models, a three-flow model and a four-flow model, were used to characterize leakage flow rate and photocatalytic oxidation of NO, respectively. Parameters for the rate law were identified using a standardized lab-scale reactor and the experimental results were correctly fitted with finite differences integration.