Fast reversible reactions in power plant plumes: Application to the nitrogen dioxide photolytic cycle

Abstract

Fast reversible reactions of trace components in which plume mixing times are long compared to characteristic reaction times or k ƒ[A] 0b 0/u 0 > 1.0 are incorporated into the buoyant plume theory of Hoult et al. (1969). A set of non-linear algebraic relations representing the bulk mean concentration of species are derived for a bimolecular reaction of the form A + B→ k r k ƒ AB and suggestions are made to adapt the results to realistic temporal and spatial concentration variations for the case in which the neglect of ambient turbulence is justified. Approximate solutions for the concentration of species are derived in the near and far-field and compared with numerical results, with and without reactant entrainment. For the case of contained reactants far-field asymptotic results predict that the product concentration [AB]~x − 8 3 while the reactant concentrations [A] and [B] ~x − 4 3 . Moreover, if B is entrained [A] and [AB] ~x − 4 3 . The far-field results are also adapted to the problem of predicting NO and NO 2 concentrations in the photolytic nitrogen dioxide cycle. Typical numerical solutions are demonstrated and compared with field measurements and a simple expression is provided for the distance to NO oxidation for important cases in which the effects of atmospheric turbulence can be neglected and there are no inversions.