Empirical modeling of the selective non-catalytic reduction of NO comparison with large-scale experiments and detailed kinetic modeling

An empirical model for the selective non-catalytic reduction (SNR) of NO with NH₃ as reductant is proposed. The model is based on two empirical reactions: one reaction describing the oxidation of NH₃ to NO, and the other the reduction of NO by reaction with NH₃ to N₂. It is shown that the model describes the influence of the major parameters that can be varied in the SNR process (injection temperature, temperature gradient, residence time, amount of injected NH₃ and amout of injected additive). The model predictions are compared to experiments carried out in a fluidized bed boiler and in a pilot plant using flue gas withdrawn from a coal fired utility boiler and it is compared with the kinetic model of Miller and Bowman (1989). When ideal mixing between the injected NH₃ and the flue gas can be assumed, as in the cyclone of the fluidized bed boiler, a good agreement between the model predictions and the experiments is obtained. The empirical model gives a better description of the result for a fluidized bed boiler than the kinetic model of Miller and Bowman (1989). In the coal fired pilot plant the mixing process is not ideal, this seems to influence the process performance.