Release of fuel-nitrogen during the gasification of Shenmu coal in O2

Formation of NH3, HCN, NO and NO2 from the gasification of a Chinese coal (Shenmu) in a fluidised-bed/fixed-bed reactor in 4.1% O2 in argon was investigated. The presence of O2 even at 673 or 773 K could lead to the gradual gasification of char to form HCN and NH3. The yields of NH3 and HCN showed maxima at about 773 K, amounting to 40% of coal-N. In the presence of O2, the H radicals required for the formation of NH3 and HCN may be generated from the reactions in the gas phase and within the solid particles. The yields of NOx increased from 773 to 973 K. A non-negligible proportion (∼5%) of coal-N was converted into NO2 at 773 K through homogeneous and heterogeneous reactions. The yield of NO2 diminished with increasing temperature. At 1173 K, the reactions between char-N and H2O (or O/H-containing radicals) formed from the oxidation of char and volatiles led to the formation of NH3 but not HCN. This route of NH3 formation is believed to be an important pathway for the formation of NH3 in an air-blown gasifier.