Conversion of volatile nitrogen and char nitrogen to NO in oxy-biomass combustion

In this paper, the volatile and char combustion were separated in a high temperature fixed bed reactor. The effects of temperature (700-1300 degrees C) and oxygen concentration (5%-40%) on volatile-N and char-N, as well as the nitrogen conversion mechanism of three different biomass were studied in O-2/CO2 and O-2/Ar atmospheres. The results show that the release amount of fuel-NO increases first and then decreases with temperature in both coupled and separated combustion. Nitrogen redistribution caused by the interaction between volatile and char during pyrolysis at high temperatures can affect the final release amount of fuel-NO. Thus, below 1100 degrees C, the release amount of fuel-NO in coupled combustion is smaller than that in separated combustion, while the opposite trend is shown after 1100 degrees C. With temperature increasing, the release amount of volatile-NO increases first and then decreases, while the release amount of char-NO decreases continuously. The release amount of volatile-NO in O-2/CO2 is less than that in O-2/Ar, and the release amount of char-NO also shows the same result at low temperature, and shows the opposite trend at high temperature. With oxygen concentration increasing, the release amount of fuel-NO in coupled and separated combustion, as well as volatile-NO and char-NO increases first and then decreases.