Experimental study of nitrogen conversion during char combustion under a pressurized O2/H2O atmosphere

Pressurized O-2/H2O combustion is a promising oxy-fuel technology for reducing CO2 emissions while improving the overall efficiency of power plants. However, this process is complex, and the associated char-N conversion are not well understood. In the present work, a pressurized horizontal furnace reactor was used to investigate the effects of different factors on the migration and transformation of char-N. Flue gas analysis and X-ray photoelectron spectroscopy were employed to assess the effects of pressure (over the range of 0.1-1.3 MPa), steam concentration (0%-60%) and residence time (60-240 s) on NO emissions and the transformation of char-N. Pressure was found to affect NO emissions and the lowest relative migration of char-N to NO was at 0.4 MPa. With increases in pressure, the proportions of N-5 and N-X groups increased and decreased, respectively center dot H2O promoted the migration of char-N to NO and the formation of N-X functional groups. As the reaction time prolonged, the proportion of N-5 groups decreased in the early stage of the reaction, that of N-X groups increased in the late stage and N-6 and N-Q groups remained stable.