Nitric Oxide Formation From Fuel-N in Staged Combustion for Liquid Fuels

Nitric oxide formation from fuel nitrogen in staged combustion is investigated to assess the impact of fuel properties on the formation and control of NO emissions. Effects of operating conditions such as stoichiometric ratio, fuel types, and amount of fuel nitrogen were examined experimentally for six liquid fuels with nitrogen content from 0.04 to 9.5%. Exhaust NO emissions were found to be directly related to the amount of oxidizable nitrogen species leaving the first stage. NO, HCN and NH3 concentration were measured in the fuel-rich zone of the staged combustor as a function of stoichiometry for three liquid fuels. Similar characteristics were observed for all liquid fuels. As the first stage stoichiometry was reduced, NO concentrations at the first stage exit decreased, and below SR1=0.8±0.05 HCN and NH3 concentrations increased. Thus, the total fixed nitrogen (TFN=NO+HCN+NH3) concentration passed through a minimum. Both staged and excess air combustion could be predicted from the TFN concentration data exiting the first stage of combustion.