Experimental Study on Combustion of Methane / Ammonia Blends for Gas Turbine Application

Abstract

Hydrogen from renewables or reformed natural gas with CO2 Capture and Storage (CCS) can be used as fuel to achieve CO2 free power production. Because of the challenges related to transport and storage of H2, NH3 has been proposed as a hydrogen carrier as it can be stored in liquid form at moderate pressures and temperatures. NH3 can be used as a fuel directly, but the low reactivity and flame speed in air makes combustion stability challenging in conventional gas turbine combustors. As no solutions are commercially available today, a transitional approach is to only replace part of the fuel with NH3 to limit the change in the combustion properties, although this only partly decarbonizes the fuel. This study investigates combustion of CH4/NH3 blends with air in a downscaled Dry Low Emission (DLE) burner at pressures up to 6 bar and thermal power up to 100 kW. The effects of equivalence ratio and NH3/CH4 mixture ratio on the emissions of NOx, CO, CH4, HCN, N2O, and NH3 are studied at different pressures and power. Even small amounts of NH3 introduction in the fuel results in unacceptable high NOx emissions in a conventional combustor and the flame stability limits the maximum NH3 content in the fuel. However, by using a two-stage combustion strategy with a rich primary zone, NOx emissions down to ca. 100 ppm could be achieved with a NH3 content up to 100%, provided the thermal intensity of the combustor is severely reduced.