Performance viability of a natural gas fired combined cycle power plant integrated with post-combustion CO2 capture at part-load and temporary non-capture operations

Natural gas combined cycle (NGCC) power plants fitted with carbon capture and storage (CCS) technologies are projected to operate as mid-merit plants in the future of the decarbonised energy market. This projection stems from an inherent characteristic of the NGCC plants of being flexible in operation and able to rapidly change their output power. Therefore, it is expected that the NGCC-CCS plants will continue to operate flexibly for a range of operational loads; and therefore compliment the intermittent electricity generation of other low carbon plants to securely maintain the quality of electricity supply. This study aims to evaluate the performance of a triple pressure NGCC power plant fitted with a post combustion CO2 capture plant (PCC) at power plant part loads, and assess the effect of the temporary shutdown of the PCC plant. Steady state simulations of the integrated plant at part loads were performed, as well as the integrated plant in non-capture operating mode. These demonstrated that the PCC steady state performance is viable at part loads down to 60%. However, operation in non-capture mode revealed a negative impact on the steam turbine performance, especially on the low pressure (LP) and intermediate pressure (IP) cylinders, as well as the cold end. Suggesting that it is not beneficial to operate in the non-capture mode, regardless of inevitable situations where the PCC or the CO2 compression unit trip.