Combined pinch and exergy analysis for post-combustion carbon capture NGCC integrated with absorption heat transformer and flash evaporator

Abstract

Natural gas combined cycle power plant (NGCC) with post-combustion carbon capture (PCC) is a transitional technology for achieving net-zero emissions, but PCC significantly decreased its energy efficiency. In the work, absorption heat transformer and flash evaporator (AHT-FE-aided system) was used to mitigate the energy penalty of NGCC caused by PCC. Subsequently, heat exchange networks (HENs) were constructed for the system, followed by a combined pinch and exergy analysis (CPEA). The results showed that the improved HEN of the NGCC with AHT-FE-aided PCC (proposed system) resulted in 13.4 % less exergy destruction than the NGCC with PCC (reference system). To fully understand the exergy destruction and environmental impact of this system, an exergy distribution analysis and a technical evaluation were conducted. The net energy and exergy efficiency of the proposed system (48.11 %/46.04 %) were 1.73 % and 1.65 % higher than the reference system (46.38 %/44.39 %) respectively. The energy penalty of PCC in the proposed system (8.76 %) was lower than the reference system (11.89 %). In addition, the proposed system decreased fuel consumption by 5.90 g NG/kWh. This study confirms that the AHT-FE-aided system reduces the energy penalty of NGCC caused by PCC, and that CPEA is an effective tool to guide improvements in this area.