A NOx Plume Dispersion Model with Chemical Reaction in Polluted Environment(<Special Issue>Urban Air and Environment Control Technologies)

Recently, because of the regulatory enhancement together with the technology development, concentration of pollutants in emission sources are decreasing significantly. Nitrogen oxides concentrations in stack gases of electric power plants are around 10ppm, and for gas combined power plant it is less than that for facilities constructed in city areas. Therefore, the concentrations at emission sources are less than one hundred times of the ambient concentrations in urban areas or for some cases almost ten times of them. The ventilation towers for automobile tunnels in urban areas are an another typical example. For such kind of low concentration sources, particularly, for nitrogen oxides dispersion, the inert gas assumption of usual plume dispersion model is not suitable, since the dispersion and chemical reactions took place together in the atmosphere. They are the major controlling factors of the diffusion in the atmosphere. We developed an Integrated Plume Dispersion Model of NO_x with Chemical Reactions and examined the performance of the model. The model is based on Gaussian plume dispersion model in integrated forms, and atmospheric diffusion and chemical reactions of NO, NO_2, O_3, O in the plume and ambient atmosphere are described by a set of ordinary differential equations. The model was solved for different emission conditions and back ground concentrations, and reasonable results were obtained.