Global warming potential and net power output analysis of natural gas combined cycle power plants coupled with CO2 capture systems and organic Rankine cycles

Abstract

The objective of this study was to analyze the environmental and energetic analysis of a natural gas combined cycle (NGCC) power plant integrated with post-combustion carbon capture (PCC) and an organic Rankine cycle (ORC) as an alternative to increase net power output using thermal integration between the three processes. This study consisted of the calculation of the global warming potential (GWP) and the net power output as a function of the amount of CO2 captured. For the analysis, the base was taken as the simulation of a 453-MWe NGCC power plant with a monoethanolamine-based PCC process and an ORC. The base case shows that the ORC could generate a considerable amount of energy using a stream of hot water to evaporate the working fluid; this stream was previously extracted from the low pressure turbine and used in the stripper reboiler. Then three study cases were considered. For case 1 (NGCC + PCC + ORC), the power output is 381.2 MW with a capture of 42.43 kg/s of CO2 and a production of 2.02 MW in the ORC with a GWP of 94.75 g CO2e/kWh. For case 2, exhaust gas recirculation (EGR) was considered. For this case, the energy production is 386.52 MW, with 1.905 MW produced in the ORC. For case 3 with PCC and NGCC thermal integration, the net power output is 391.42 MW. These three cases were analyzed and the amount of combustive gases were varied to determine the effect on the power output, CO2 captured, and the GWP of these processes. The results show the tradeoffs between the considered goals and set an objective framework for policymakers to better operate these types of systems.