Techno-economic Analysis of a Natural Gas Combined Cycle Power Plant Integrated with a Ca-looping Process for Post-combustion Capture

Abstract

In this study, it was sought to find an efficient way to integrate a natural calcium oxide looping process with a Natural Gas Combined Cycle (NGCC) power plant for its post-combustion CO2 capture. To achieve 90% carbon capture from the NGCC flue gases containing no more than 4.0% CO2, the carbonator should operate at a lower temperature than when it runs for a coal-fuelled power plant due to the thermodynamic limit of chemical reaction equilibrium of CO2 with calcium oxide (CaO). In turn, the decreased carbonator temperature gives rise to 1) more solids circulating due to reduction of the CO2 absorption rate and 2) more fuel consumption in the calciner for heating up the solids. To alleviate the adverse effects, it was proposed to implement exhaust gas recirculation (EGR) by which the CO2 content could increase up to 6.8%, enabling the NGCC to have a net power efficiency to an extent similar to ones integrated with amine capture. As a result of economic analysis of the capture cases, it was concluded that integrating a NGCC with a Ca-looping unit would be more lucrative than amine capture cases with respect to the cost of electricity (COE) and cost of CO2 avoided (COA).