Exergetic Analysis of a Natural Gas Combined-Cycle Power Plant with a Molten Carbonate Fuel Cell for Carbon Capture

Abstract

This study aims to propose the repowering of an existing Italian natural-gas fired combined cycle power plant through the integration of Molten Carbonate Fuel Cells (MCFC) downstream of the gas turbine for CO2 capture and to pursuit an exergetic analysis of the two schemes. The flue gases of the turbine are used to feed the cathode of the MCFC, where CO2 is captured and transported to the anode while generating electric power. The retrofitted plant produces 787.454 MW, in particular, 435.29 MW from the gas turbine, 248.9 MW from the steam cycle, and 135.283 MW from the MCFC. Around 42.4% of the exergy destruction has been obtained, the majority belonging to the combustion chamber and, in minor percentages, to the gas turbine and the MCFC. The overall net plant efficiency and net exergy efficiency are estimated to be around 55.34 and 53.34%, respectively. Finally, the specific CO2 emission is around 66.67 kg/MWh, with around 2 million tons of carbon dioxide sequestrated.