Photocatalytic NOx abatement: mathematical modeling, CFD validation and reactor analysis

A 2D CFD model was implemented for the numerical simulation of NO _x abatement in a photocatalytic reactor, considering the effect of relative humidity (10–60%), light intensity (0.3–13 W⋅m ⁻²) and inlet NO concentration (0.1–1.0 ppm). Significant differences of NO _x concentration at the catalytic surface and bulk gas were found (Δ _max of ∼12% and ∼16% for NO and NO ₂, respectively) and corrections were proposed to achieve intrinsic rate laws from a model available in the literature. An analysis of the reactor performance was conducted and a nonlinear behavior was observed when the channel height (H) was varied. A point of maximum for the integral rate of NO and NO ₂ consumption as a function of H was found (Δ _NO of ∼2% and ∼-1% for H→2H→4H; Δ _{NO 2} of ∼46% and -8.5% for H→2H→4H). Additionally, the NO conversion decreased from ∼29% to ∼7% and the selectivity decreased from ∼85% to ∼80% (passing through a point of minimum at 2H) when the height was varied in the range H-4H. When comparing the results from the CFD simulations and the predictions of a plug flow model, deviations for NO conversion and selectivity increased with H (Δ _max of ∼2% and ∼45%, respectively).