Thermal Integration of Postcombustion CO2 Capture in Existing Natural Gas Combined Cycle–Combined Heat and Power Plant

In this study, a 470-MWh natural gas combined cycle–combined heat and power plant (NGCC-CHP) in Beijing is the research object. For the industrial NGCC-CHP plant, the introduction of 90% postcombustion carbon capture (PCC) highlighted an outstanding issue: limited low-pressure steam allocation between district heating and CO2 capture. This work evaluates four options for providing the energy necessary for the amine reboiler when most of the low-pressure (LP) steam was extracted for district heating: electric heating of the reboiler, direct natural gas firing of the amine reboiler, a standalone gas-fired boiler to generate low-pressure steam, and integration via supplementary firing of the heat recovery steam generator. The study focused on net power output, CO2 capture level, CO2 emission intensity, and profit ratio. The results show that supplementary firing improves the steam turbine power output up to 135.84 MWh with the firing of 217.65 MW of additional natural gas, whereas the net equivalent efficiency is approximately 50.2%. The integration via supplementary firing of the heat recovery steam generator (HRSG), therefore, is shown to have a higher technical and economic performance advantage over other options.