An Advanced Model for the Description of Conversion Processes of Nitrogen Oxides in Plumes of Large Point Sources
A descriptionis given of a model which is used to predict the oxidation rate of nitrogen oxides in plumes of large point sources such as power plants. Results of this model can be used both to calculate concentrations of NO and NO2 in the vicinity of the source and for sub-grid parametrisation of chemical reactions in meso- or large-scale models. To model the fast non-linear oxidation reaction of NO, we focus on the dispersion and mixing of the plume and the chemical reactions occurring simultaneously. The dispersion for the first 30 – 60 seconds after emission from the source is described by a jet phase module. For distances up to about 25 km, dispersion parameters of an instantaneous plume are used which were derived from SF6 tracer gas experiments. The effect of concentration fluctuations on the oxidation rate wad also taken into account. The model is validated by observed airbone NOx conversion data. Furthermore a sensitivity analysis was carried out. The latter showed that the highest uncertainties are caused by errors in the size of the instatneous plume. This may explain also differences between measurements and model calculations.
KeywordsOxidation Rate Nitrogen Oxide Dispersion Parameter Concentration Fluctuation Plume Dispersion
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