Process integration of a Calcium-looping process with a natural gas combined cycle power plant for CO2 capture and its improvement by exhaust gas recirculation

In this study, it was sought to find an efficient way to integrate a Ca-looping process with a Natural Gas Combined Cycle (NGCC) power plant for its post-combustion CO2 capture. Compared to its application to coal combustion flue gas, Ca-looping would incur augmented energy penalty when integrated with a NGCC of which the flue gas contains only 4.0 mol% CO2. The reduced CO2 concentration in the feed requires the carbonator to operate at a lower temperature and more solids to circulate between carbonator and calciner for keeping up the carbon capture efficiency at 90%. However, this study demonstrated that such negative effects could be alleviated greatly by implementing 40% exhaust gas recirculation to the NGCC with the CO2 concentration in the flue gas increasing up to 6.8%. Accordingly, the resulting net power efficiency increased notably 1.6% points in comparison to its equivalent non-EGR NGCC case and it was only 0.9% points less than amine capture case. This study exhibited that exhaust gas recirculation would be crucial in decarbonising a NGCC power plant by Ca-looping.