Exergy Analysis of a Natural Gas-Fired Gas Turbine Combined Cycle Power Plant with Post-Combustion Carbon Capture

Abstract

Post-combustion carbon capture (PCC) plays an important role in reducing the greenhouse gas emissions. In the present study, an exergy analysis is conducted to assess the exergy destruction and exergetic efficiency of a natural gas-fired combined cycle gas turbine (CCGT) system coupled with the PCC unit. The overall exergetic performance of the system is compared against the baseline CCGT by using realistic data. The working temperature and composition of the exhaust flue gas are two critical parameters that have significant impact on the performance of the absorption liquid and equipment operation. Results show that the highest exergy destruction occurs in the combustion chamber and condenser are 15.69 MW and 11.78 MW, occupying more than 45 % of the exergy destruction of the overall system for the conventional CCGT system. For the CCGT system with PCC unit, the exergy destruction of absorber is relatively high with an exergetic efficiency of 56.18 %. The highest exergetic efficiency is found in the units of combustion chamber and heat recovery steam generator (HRSG), which are 90.23 % and 87.01 %, while the condenser has the lowest efficiency. Identification of the low efficiency component presents an opportunity for improvement of the system.