58674 - Analysis of the Emission Reduction Potential and Combustion Stability Limits of a Hydrogen-fired Gas Turbine with External Exhaust Gas Recirculation 

Proceeding towards the world-wide goal of net-zero greenhouse gas (GHG) emissions by 2050 is integral to sustain the livelihood of humanity on earth. GHG emissions must be minimized in all sectors. Therefore, electrification is seen as a promising measure if driven by renewable energy sources such as wind and solar. However, due to the inherent volatility and limited predictability of renewable power generation, flexible and dispatchable power generation technologies such as gas turbines are an essential measure to maintain grid stability. Nevertheless, these gas turbines must be run with CO₂-neutral fuels like hydrogen or in combination with carbon capture (and storage) plants to suffice the requirement of a GHG-neutral power generation sector.

Previous studies showed that partial external exhaust gas recirculation (EGR) is an effective way to increase the efficiency of carbon capture units in gas turbine power plants. Moreover, EGR technology potentially enables the safe and clean combustion of hydrogen by creating an oxygen depleted environment in the combustor, suppressing the high reactivity of hydrogen fuel and its tendency towards increased nitric oxide (NO_x) emissions. A preceding model-based study by the authors already assessed the impact of hydrogen combustion and external EGR on the gas turbine process. However, the underlying challenges regarding the combustion of hydrogen and the potentially positive impact of the application of external EGR on those challenges were neglected within the scope of this study. Therefore, to gain a deeper understanding of such influences, the present model-based study presents a first-order approach to the formation of emissions (e.g. NO_x) and combustion stability by means of a 1-D-flame simulation. The results show that the implementation of EGR in hydrogen-fired gas turbines indeed reduces the formation of nitric oxides through the thermal pathway. Moreover, combustion suppression due to an oxygen-depleted environment is very well matched with the high reactivity of hydrogen. Therefore, EGR eventually paths the way for the safe and flexible utilization of hydrogen as gas turbine fuel.