Nitrous Oxide Concentrations in Coal,Oil,and Gas Furnace Flames

Abstract

Concentrations of N2O, NOx, CO2, and O2 were determined along the axis of coal, oil. and gas flames in a 3 MW experimental furnace, for both single-stage and two-stage combustion conditions. Concentrations of NOx and N2O were found to be strongly correlated along the flames and in the flue gas samples, with approximately one mole of N20 produced for every three moles of NOx. The results suggested that most of the NOx and N2O arose from oxidation of fuel nitrogen, with highest concentrations observed in coal flames and lowest levels in the natural gas flame. Approximately 12 percent of fuel nitrogen was converted to N2O in coal and oil flames. Two-stage combustion, which produces a fuel-rich zone near the burner, substantially lowered emissions of both NOx and N2O in the experimental flames. In most cases the rates of decline were similar for the two gases, suggesting that related processes could account for the reduction of these nitrogen oxides in fuel-rich flames. Staged combustion is seen as an effective method for controlling both N2O and NOx emissions.