Thermal and Economic Assessments for Post-Combustion Co2 Capture in Natural Gas Combined Cycle with Waste Heat Recovery

Abstract

This paper reports a system integration study on natural gas combined cycle (NGCC) with CO2 capture. When the alkali-based CO2 capture system is integrated into a typical NGCC power plant with 134.53 MW net power generation, the extracted steam for desorption unit and additional power for solid circulation lead to 12.05% thermal efficiency reduction. To fully recover the low-level heat of the CO2 capture system, a new integration configuration for NGCC with CO2 capture is proposed by adding an absorption heat transformer. In comparison, the new integrated system fully recovers the low-level heat of the CO2 capture system by sacrificing a portion of power generation. As a result, it provides 110.22 MW extra heat output in trade for a reduction of 21.07 MW power generation. Economic analysis shows that the cost of electricity and cost of avoided CO2 of the new integrated system are reduced by 8.26 $/MWh and 34.74 $/t CO2, respectively, due to the extra economic benefits by heat output.

Keywords: Natural gas combined cycle, System integration, Waste heat recovery process, Thermal and economic analysis