Exhaust gas recirculation applied to single-shaft gas turbines: An energy and exergy approach
2022
Hachem, Joe | Schuhler, Thierry | Orhon, Dominique | Cuif-Sjostrand, Marianne | Zoughaib, Assaad | Molière, Michel
The present energy mix is leaning towards natural gas as solution to reduce our carbon footprint due to its relatively low GHG emission factor. Gas Turbines could therefore be a great short-to-mid-term solution to fight climate change. The gas turbine flexibility, or part-load operation, is an indispensable asset in some O&G applications and in the hybridization with renewable energies applications. However, operating at part-load also means degrading the cycle efficiency. Exhaust gas recirculation ‘EGR’ applied to gas turbines is a well-known technology used to decrease the NOx emissions and enhance carbon capture and storage, but also, to potentially improve the part-load efficiency. In this article, the impact of EGR is investigated on full-load and part-load operations of gas turbines while dissociating the two effects generated by the EGR, the Inlet Air Heating ‘IAH’ and the change in air composition ‘CAC’. The energy approach using a thermodynamic model showed the intrinsic negative impact of EGR on gas turbines that can reach up to 0.25 points at 50 % recirculation at full-load; however, it is also showed the potential part-load efficiency compensation due to the IAH effect that could improve by 1 point the efficiency at 50 % load and 50 % recirculation rate.
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