Insights into combustion and emission characteristics of ammonia co-firing with hydrogen-rich gas for gas turbine applications

In this work, hydrogen-rich gas (HRG), a byproduct generated in various chemical engineering processes, is first utilized to enhance ammonia (NH3) swirl flames. Swirl combustion and emission characteristics of ammonia/HRG/air mixtures are explored and kinetic modelling is performed to reveal the controlling effects. Results indicate that increasing the HRG content can substantially enhance the combustion intensity and flame stability of ammonia/HRG/air swirl flames. This approach also helps prevent flashback, a common issue in pure HRG combustion, and achieves a complementary effect in reactivity. The chemical effect is dominant in enhancing flame stability, while the thermal effect also contributes significantly. With the HRG content increasing, NO and NO2 emissions increase, while N2O, NH3 and CH4 emissions decrease. Chemical reactor network simulation shows that higher HRG content shifts the product equilibrium from N2 to NO, driven primarily by increased O, H and OH radicals, showing a trade-off between combustion enhancement and emission control. Despite the relatively high pollutant emissions in the primary stage, low NOx emissions (<200 ppm) can still be achieved with high combustion efficiency under axial staged combustion, indicating direct applicability in gas turbines through selective catalytic reduction technique.