Reducing the Energy Penalty of Retrofit Decarbonization in Combined Cycle Power Plants

This study is a continuation of previous work aimed at elucidating the effect of hydrogen-cofiring and exhaust gas recirculation (EGR) on combined cycle (CC) performance. The thermodynamic analysis was expanded to include post-combustion capture (PCC) by means of mono-ethanolamine (MEA). Attention was paid to net power output and thermal efficiency.

Part-load operation of the CC without carbon capture was taken as reference. Decarbonization solutions, in ascending order of complexity, included the following: 1) adding a PCC unit; 2) combining EGR with PCC, so as to exploit the increase in the flue gas CO₂ concentration while reducing the exhaust gas flow delivered to the absorber; 3) including hydrogen co-firing at the largest capability dictated by the gas turbine (GT) combustion system, with the opportunity to explore a wider range of EGR rates, while still relying on PCC of the residual CO₂ in flue gas, before discharge into the environment.

Scenarios were firstly discussed under the same GT load for consistency with the published literature, thus enabling the validation of the modelling procedure. Then, CC net power production was assumed as the basis of comparison. The third solution was found to be the most promising thus minimizing both the energy penalty due to carbon capture and CO₂ emission intensity (EI).