Thermal integration of natural gas combined cycle power plants with CO2 capture systems and organic Rankine cycles

Abstract

In this paper, the thermal integration of a natural gas combined cycle (NGCC) power plant integrated with post-combustion carbon capture (PCC) and CO2 compression is proposed. With the objective of finding a heat exchanger network (HEN) that decrease the energy impact of the PCC process, which reduce the power output of the turbines as it requires a large amount of steam for its operation and it uses part of the power generated by the NGCC power plant. Also, the possibility of implementing an Organic Rankine Cycle (ORC) to generate electricity with the wasted energy of the process is analyzed. This study consists of a 453MWe NGCC power plant with an MEA-based PCC process, and the option to consider a fixed 260kWe ORC or an ORC with variable power output, which are simulated in ASPEN PLUS® to obtain all the process inventories. Then the thermal integration is performed using the SYNHEAT model. Result show that the proposed HENs can reduce the use of steam in the striper reboiler to 65.43Kg/s and it can also reduce the use of hot water to heat the input of natural gas producing a 126.571MWe power output of the steam turbines increasing the thermal efficiency to 50.94% whereas the implementation of the ORC can increase the power output up to 1.651MWe using the wasted energy of the plant and also the global warming potential (GWP) decrease 78% due to the reduction in CO2 emission and the generation of more power in comparison with the stand alone NGCC.