A study of the interaction between volatile and char on the mechanism of NO and N2O conversion during nitrogen-containing biomass model (amino acids) combustion

The interaction between volatile and char is widespread in combustion. The effect of this interaction on the conversion of fuel-N to NOx is significant, but the mechanism remains to be comprehensively unveiled. Thus, in this paper, the NO and N2O conversion of nitrogen-containing biomass models (glutamate, glycine, phenylalanine) during combustion at high temperatures (800∼1500°C) is investigated using two combustion modes, separated combustion (in which volatile and char are burned separately) and coupled combustion (in which volatile and char are burned simultaneously), in an O2/Ar atmosphere. A new pathway for N2O formation resulting from the interaction between volatile and char is identified. At low temperatures, this interaction facilitates the conversion of fuel-N to N2O. For instance, during the separated combustion of glutamate at 800°C, the conversion rates of fuel-N to N2O and NO are 26.3% and 20.4%, respectively. However, in coupled combustion, these conversion rates shift to 48.1% for N2O and 3.6% for NO. At high temperatures, this interaction promotes the conversion of fuel-N to NO. For instance, during the separated combustion and coupled combustion of glutamate at 1500°C, the conversion rates of fuel-N to NO are 6.2% and 16.6%, respectively. Similar patterns are observed for the other two amino acids. In both combustion modes, the co-firing of cellulose, lignin, and hemicellulose with glutamic acid significantly suppresses the production of N2O. The conversion rate of N2O decreases by about 7%∼10%, while the impact on NO release shows either a suppressive or promotive effect in different temperature intervals. These results play a crucial role in the development of efficient and clean combustion technology for biomass.