THE THERMAL DENO(X) PROCESS - INFLUENCE OF PARTIAL PRESSURES AND TEMPERATURE

The effect of partial pressures of the reactants in the Thermal DeNO(x ) process has been investigated in Row reactor experiments. The experi ments were performed at atmospheric pressure for temperatures ranging from 923 to 1373 K. Initial concentrations were varied for NH3/NO (400 /200, 1000/500, 2800/1400 ppm) and O-2 (0-50%). The data confirm earli er observations that in the temperature range revered, presence of O-2 is required in order for NO to be reduced by NH3. As the initial O-2 concentration is increased, the lower boundary for the process is shif ted towards lower temperatures. The temperature range for NO reduction is widened, but the NO reduction potential decreases. At high oxygen concentrations the maximum NOx reduction is below 40%. Under these con ditions, significant amounts of NO2 and N2O are formed. Two mechanisms for N2O formation in Thermal DeNO(x) have been identified. One is act ive at higher temperatures and low O-2 concentrations, while the other , which presumably involves NO2 as a precursor, is dominant at lower t emperatures and high O-2 levels. The implications of the results for a pplication of Thermal DeNO(x) in high pressure systems such as pressur ized fluidized bed combustion is discussed. Comparisons of the experim ental data with recent chemical kinetic models indicate that the detai led chemistry of the Thermal DeNO(x) system is not completely understo od.