Pressure Effects on the Thermal De-NOx Process

The effect of pressure on the thermal de-NOx process has been investigated in flow reactor experiments. The experiments were performed at pressures from 1 to 10 bar and temperatures ranging from 925 to 1375 K. The inlet O-2 level was varied from 1000 ppm to 10%, while NH3 and NO were maintained at 1000 and 500 ppm, respectively At the highest pressure, CO was added to shift the regime for NO reduction to lower temperatures.

The results show that the pressure affects the location and the width of the temperature window for NO reduction. As the pressure is increased, both the lower and the higher boundaries for the process are shifted toward higher temperatures. Overall, the temperature range for NO reduction appears to be slightly broadened. The shift in chemistry toward higher temperatures is mast pronounced at low oxygen concentrations. High oxygen levels act to counterbalance the inhibiting effect of the pressure but also cause a slight decrease in the NO reduction potential.

The results are consistent with recent atmospheric pressure experiments of thermal de-NOx covering a wide range of reactant partial pressures. Comparisons of the experimental data with the recent chemical kinetic model of Miller and Glarborg show satisfactory agreement. The implications of the results for application of thermal de-NOx in high-pressure systems, such as pressurized fluidized bed combustion and gas turbines, are discussed.