Effect of fuel composition on NOx formation in high‐pressure syngas/air combustion

In this study, an experimental investigation of lean premixed syngas/air flames with H₂/CO ratio of 1.0 and equivalence ratio of 0.5 has been conducted in a high‐pressure burner facility to investigate the effects of pressure and the presence of hydrocarbons on NO_x speciation. Detailed NO_x speciation measurements in the post‐flame region were conducted for various pressures up to 1.5 MPa (15 bar) using Fourier transform infrared (FTIR) spectroscopy. When the pressure is increased, NO concentration decreases while NO₂ increases due to pressure dependence of NO to NO₂ conversion. For a given pressure, the presence of hydrocarbons in syngas leads to an increase in NO_x concentrations possibly due to prompt NO formation. Comparison of NO concentrations in presence of CH₄ at different pressures shows that the effect of CH₄ due to prompt NO formation is more dominant than the effect of pressure on NO. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3134–3140, 2018