Effect of Syngas Composition and CO2-Diluted Oxygen on Performance of a Premixed Swirl-Stabilized Combustor

Abstract

Future energy systems based on gasification of coal or biomass for co-production of electrical power and fuels may require gas turbine operation on unusual gaseous fuel mixtures. In addition, global climate change concerns may dictate the generation of a CO2 product stream for end-use or sequestration, with potential impacts on the oxidizer used in the gas turbine. In this study the operation at atmospheric pressure of a small, optically accessible swirl-stabilized premixed combustor, burning fuels ranging from pure methane to conventional and H2-rich and H2-lean syngas mixtures is investigated. Both air and CO2-diluted oxygen are used as oxidizers. CO and NOx emissions for these flames have been determined from the lean blowout limit to slightly rich conditions (ϕ ∼ 1.03). In practice, CO2-diluted oxygen systems will likely be operated close to stoichiometric conditions to minimize oxygen consumption while achieving acceptable NOx performance. The presence of hydrogen in the syngas fuel mixtures results in more compact, higher temperature flames, resulting in increased flame stability and higher NOx emissions. Consistent with previous experience, the stoichiometry of lean blowout decreases with increasing H2 content in the syngas. Similarly, the lean stoichiometry at which CO emissions become significant decreases with increasing H2 content. For the mixtures investigated, CO emissions near the stoichiometric point do not become significant until ϕ > 0.95. At this stoichiometric limit, CO emissions rise more rapidly for combustion in O2–CO2 mixtures than for combustion in air.