(199g) NOx Emissions from Premixed Syngas/Air Flames at Atmospheric Pressure

Syngas combustion offers a considerable opportunity for clean power generation applications with high efficiency in decreasing pollutant emissions from gas turbines. Hydrogen in syngas results in elevated combustion temperatures that facilitate the thermal formation of nitrogen oxides (NO_x). In contrast, higher temperatures promote complete combustion and reduce the emission of carbon monoxide (CO). Lean premixed combustion has been used to reduce pollutant emissions by controlling the flame temperature. The optimum flame temperature of a lean premixed combustor is designed to be near the lean flammability limit and consequently, its performance is characterized by a CO/NO_x trade-off. The efficiency of the process can be improved through the identification of various parameters such as pressure, temperature, and composition of the fuel, while a detailed understanding of the NO_x formation is required in order to reduce the emissions.

 This study reports an experimental investigation of the effects of different parameters on the structure and emission characteristics of premixed H₂/CO/air flames generated on a McKenna burner. Axial and radial temperature profiles in the post-flame zone for various stoichiometries, (equivalence ratio from 0.5 to 1 with H₂/CO ratio ranging from 0.25 to 1) and flow rates were obtained. Acquiring an accurate temperature profile throughout the system is critical for making accurate predictions via kinetic simulations. Samples from the post-flame zone were drawn via a water-cooled quartz sampling probe feeding into a Fourier transform infrared (FTIR) spectrometer. Using the FTIR technique, concentrations of CO and individual NO_x species, i.e. NO, NO₂ and N₂O can be distinguished as opposed to the total NO_x measurements reported in the literature. Additionally, kinetic simulations are being performed employing a gas turbine reaction network to obtain species profiles in the post-flame zone and a comparison with the experimental data will be provided.