Catalytic activity of lime for N2O decomposition under coal combustion conditions

To understand the contribution of lime to the abatement of N2O emission fro m fluidized coal combustor, the catalytic activity of the lime for the deco mposition of N2O under coal combustion conditions was studied. Lime was act ive for the catalytic decomposition of N2O, and its activity was stable in the simulated coal combustion flue gas in the absence of SO2 at 800 degrees C. The catalytic activity of lime was depressed by the presence of CO2, H2 O, and SO2. The affect of the presence of SO2 seemed to be most important: the catalytic activity of the lime gradually decreased as the degree of sul fation increased, and the specific surface area decreased with the progress ion of sulfation. From N2O pretreatment and temperature-programmed desorpti on studies on the used lime, it was found that two oxygen species and one s pecies of NO desorbed. A surface character change due to sulfation is expec ted from these gas desorptions. From the relation of the activity to the su rface area or the desorption of the gases or both, it was concluded that a decrease in the surface area contributed to the decay of the activity more effectively than the surface character change caused by the sulfation.