The Role Of Part-Load Control Strategies In Optimizing The Efficiency Of A Decarbonized Combined Cycle Power Plant In Load-Following Mode

In pursuit of the goal of decarbonization, post-combustion capture (PCC) by means of mono-ethanolamine (MEA), exhaust gas recirculation (EGR) and hydrogen co-firing were applied to a 2x1 combined cycle (CC) under load-following operation in two typical summer/winter days. Keeping the same electrical demand profiles as in a previous study by the same author, the main novelty is to determine the part-load gas turbine (GT) control strategy that can maximize the CC net electric efficiency (ηCC,n) when applying different decarbonization solutions such as: 1) addition of PCC unit, 2) addition of PCC unit with EGR, when the fuel supply is 100% natural gas (NG) or 65% vol hydrogen co-firing. The multivariable optimization problem, with ηCC,n as objective function, under the constraint of net power output (PCC,n) equal to electricity demand, has been updated to include the following decision variables: - load of each GT; - EGR rate, depending on the fuel type: [0; 0.4] for 100% NG vs. [0; 0.55] for hydrogen blending; - GT inlet air flow and fuel flow, in a range such that the GT outlet temperature is maintained within the limit of about 50°C above the nominal value. The main finding is that the operating guidelines depend not only on the load but mainly on the environmental conditions. Under hot weather and part-load conditions, the recommendation is to rely on modulating the air/fuel flow at the GT inlet rather than applying EGR.