Nitric oxide emission from diluted CH4/CO/H2 jet diffusion flames

The paper presents an experimental study of nitric oxides from jet diffusion flames with fuels being a low calorific value gas (LCV gas) and mixtures of the given LCV gas and methane. The experiments include N2/CO2 diluted gas mixtures of CH4/CO/H2 with methane concentration in the range of 4 to 76% (vol). The flames investigated are unconfined jet flames with no use of pilot fuel. The Froude number were varied in the range of 70 - 8250 and nozzle exit velocities in the range of 2 - 18 m/s with nozzle diameters of 4 and 6 mm. The results show that the total NOx emissions increase with increasing methane content in the gas mixture with a significant contribution of prompt NOx. The measured Nox emission index is in the range of 0.05 to 2.0 g NOx/kg fuel with a corresponding methane concentration in the gas mixture in the range of 4 to 76 % (vol.). The measured NOx emissions is found to be proportional to 1.36 Fr*3/5 where Fr* is a modified Froude number based on the volume fraction of fuel in the diluted gas mixture.