(73d) Diluent Effect on NOx Formation in Pressurized Combustion of Syngas/Air

Increasing interest in syngas combustion in gas turbines has led to highlighting the environmental feasibility, in particular the control of nitrogen oxide (NO_x) emissions. Despite the established feasibility of syngas, there are challenges with the variations in the syngas composition depending on the type of feedstock and production process used to generate syngas. Presence of diluent species such as CO₂, N₂ and H₂O in the fuel can affect the NO_x emissions in the post-flame region. A detailed investigation of high-pressure syngas combustion is required to provide both practical information regarding NO_x emissions from gas turbine systems and fundamental understanding of reaction pathways to verify and develop chemical kinetic models.

In this study, an experimental investigation of premixed syngas flames has been conducted in a high-pressure burner facility to investigate the effects of pressure and the presence of diluents on NO_x speciation. Syngas consisting mainly of H₂ and CO was blended with nitric oxide (NO), and different concentrations of carbon dioxide (CO₂) as a diluent prior to combustion at high pressure. Hot combustion products were supplied to the high-pressure vessel by a flat flame burner operating with lean, premixed syngas/air mixtures with H₂/CO ratio of 1.0 and equivalence ratio of 0.5. Detailed NO_x speciation measurements as well as temperature measurements in the post-flame region were conducted for different diluent concentrations at various pressures up to 15 bar using Fourier transform infrared (FTIR) spectrometer. High-pressure speciation data that is obtained in this study can provide validation information needed for improving the kinetic models available in the literature by providing further constraints.