Experimental assessment of the performance of a commercial micro gas turbine fueled by ammonia-methane blends

This study reports on the performance of the Ansaldo AE-T100 commercial micro gas turbine (mGT) when fueled by ammonia-methane blends instead of its design fuel, natural gas. This micro gas turbine was used as the experimental platform to understand effects of ammonia addition, and its hardware was only marginally updated. Ammonia was added to the main fuel line in varying proportions, but the pilot flame fuel line was only fed with methane. Experiments were performed for constant electrical output power and turbine outlet temperature of 60 kWe and 645°C, respectively. Important operational parameters and exhaust emissions were continually monitored during the turbine's operation. Results show that stable operation on the mGT was possible until the volume fraction of ammonia in the fuel blend reached X_NH3 = 0.63. To reach this ammonia fraction, it was necessary to increase the power of the pilot flame that provides a continuous ignition source at the base of the main flame. Concentrations of carbon monoxide and unburned hydrocarbon measured in the exhaust did not increase significantly until X_NH3 = 0.22. However, above this value, concentrations increased rapidly, which is indicative of a drop in the combustion efficiency and, in turn, in the thermal efficiency. For X_NH3 = 0.63, the measured thermal efficiency was ∼0.23, which is significantly lower than that found for operation with pure methane, ∼0.27. Although the CO₂ concentration was found to decrease linearly when the ammonia fraction was increased, measurements reveal that NO_x emissions increased rapidly, with a maximum NO_x concentration of 2161 ppmvd. The concentration of N₂O also increased rapidly when the ammonia fraction was increased. Due to N₂O's very large global warming potential, this more than canceled the benefits associated with the reduction of CO₂ emissions. Consequently, results showed that, even though stable operation of the Ansaldo AE-T100’s mGT in its original configuration is possible with ammonia-methane blends at least up to 60 kWe, hardware modifications will be required to comply with current NO_x regulations and ensure sufficiently low N₂O emissions.