Experimental Identification of the Operability Limits in Exhaust Gas Recirculation Rates Under Transient Control for a Micro Gas Turbine

Abstract Exhaust gas recirculation (EGR) has been identified as a key adaptation for gas turbines to mitigate the efficiency penalty of amine-based post-combustion carbon capture. By reducing the exhaust gas flow rate and increasing CO2 concentration, EGR enhances capture efficiency while also significantly lowering NOx emissions and residual O2, both of which influence amine stability. However, the impact and limitations of EGR in dynamic operation remain largely unexplored, representing a critical gap in operability assessments. Understanding these aspects can facilitate the development of control strategies and optimization algorithms where EGR serves as an additional control variable to mitigate pollutant emission peaks. To address this, a 3 kWe mGT setup with enhanced EGR was tested under sudden EGR variations, while monitoring emissions. Additionally, emissions were measured during hot starts with different pre-applied recirculation levels. Results indicate that NOx peaks occur during EGR transitions, and high EGR rates prevent successful turbine startup. Identifying these transient behaviours, in terms of emissions and combustion stability, provides initial insights into defining operability boundaries for EGR application. The development of control algorithms to manage EGR levels is left for future work.