(209d) NOx Formation in Syngas/Air Combustion at Elevated Pressure

Combustion of high hydrogen content (HHC) fuels is central to the implementation of integrated gasification combined cycle (IGCC) systems or to other configurations that would optimize power production while minimizing emissions. Gas turbines utilizing HHC fuels for power generation applications will be required to meet stringent pollutant emission standards, particularly with respect to nitrogen oxides (NO_x). One of the effective NO_x reduction technologies for gas turbines is lean premixed (LPM) combustion method. Accurate numerical prediction of NO_x from such combustors using multi-dimensional models has only been of limited success. This is to some extent due to the complexity of NO_x formation chemistry in LPM combustion. Experimental data is necessary for generating accurate computational models of NO_x production in combustion. Improvement of the model predictions could be accomplished by validation against data from well-defined experiments to design a very low emission process with optimum efficiency. For gas turbine conditions, reliable high-pressure data is needed to both validate and improve reaction mechanisms to simulate NO_x chemistry.

In this study, NO_x formation in post-flame gases of syngas combustion was studied at elevated pressures. A high-pressure burner facility well suited to the study of reaction mechanisms was designed and fabricated. A series of experiments were performed to investigate the NO_x formation from lean premixed syngas/air combustion with various stoichiometries (equivalence ratio between 0.5-1.0 and H₂/CO ratio between 0.25-1.0). Acquiring an accurate temperature profile throughout the system is critical for making accurate predictions via kinetic simulations. Flame temperature and two-dimensional temperature distribution were measured under various conditions. Detailed NO_x speciation measurements in the post-combustion zone were conducted by Fourier transform infrared spectrometer (FTIR). Additionally, computational fluid dynamics (CFD) simulations with detailed chemical kinetics were employed to predict the temperature and species profiles.