Thermoexergetic analysis and response optimisation of selective exhaust gas recirculation with solvent-based CO₂ capture in a natural gas-fired combined cycle power plant

The present study investigates the impact of integrating selective exhaust gas recirculation (SEGR) with a combined cycle gas turbine system (CCGT) and post-combustion capture (PCC) in a model power plant. The impacts of ambient temperature, turbine inlet temperature (TIT), and pressure ratio (PR) on the overall thermal and exergetic efficiencies at component and system levels are evaluated. Results show that the combustion chamber and absorber are the two components with the largest exergy destructions in CCGT and PCC units, with a fraction of 44.8% and 52.9%, respectively. After integrating with SEGR, CO₂ concentration in flue gas rises from 3.61 to 6.08%, whereas PCC exergetic efficiency increases by 6%. A design of experiments statistical model was applied through a full factorial design to optimise the responses of minimising total exergy destruction while maximising both the thermal and exergetic efficiencies. The optimised input set for TIT of 1300 °C, PR of 15, and SEGR recycle ratio of 25% leads to the best outcome of 415.08 MW, 56.53%, and 51.04% for total exergy destruction, thermal efficiency, and exergetic efficiency, respectively. The predictor equations produced have high degrees of correlation and predictive capabilities and could be used to form empirical equations to replace thermodynamic calculations entirely. Graphical Abstract: (Figure presented.)