On the control of NOx emission from a micro gas turbine combustor fueled with mixtures of methane and ammonia

With the renewed interest in ammonia as a fuel, the potentials of methane-ammonia mixtures as low-carbon fuels for gas turbines are being evaluated. The significantly high NOx production in the flames of ammonia-containing mixtures presents an important challenge to their application. In this study, PIV, OH-PLIF, and FTIR exhaust gas analysis were employed to study the characteristics of a micro gas turbine combustor fueled with CH4-NH3-air mixtures at 0.10 MPa, and methods for controlling emissions from the flames are proposed. The concentration of ammonia in the fuel which was expressed in terms of the heat fraction, _NH3, varied from 0 to 0.3. The results show that NO emissions from the ammonia-containing flames can be more than 5000 ppmv (parts per million volume) in single-stage combustion. Emissions control was achieved with two-stage rich-lean combustion and an optimum equivalence ratio upstream of the combustor for low NOx emission was found to be around 1.30 for _NH3= 0.20 and 0.30, and 1.35 for _NH3= 0.10. At these optimum upstream equivalence ratios, the NO emission from the combustor was in the order of 40 ppmv at 16% O2 concentration with complete fuel consumption over a wide range of overall equivalence ratios.