Energy and Exergy Analyses of a Power Plant With Carbon Dioxide Capture Using Multistage Chemical Looping Combustion

A thermodynamic model and parametric analysis of a natural gas-fired power plant with carbon dioxide (CO₂) capture using multistage chemical looping combustion (CLC) are presented. CLC is an innovative concept and an attractive option to capture CO₂ with a significantly lower energy penalty than other carbon-capture technologies. The principal idea behind CLC is to split the combustion process into two separate steps (redox reactions) carried out in two separate reactors: an oxidation reaction and a reduction reaction, by introducing a suitable metal oxide which acts as an oxygen carrier (OC) that circulates between the two reactors. In this study, an Aspen Plus model was developed by employing the conservation of mass and energy for all components of the CLC system. In the analysis, equilibrium-based thermodynamic reactions with no OC deactivation were considered. The model was employed to investigate the effect of various key operating parameters such as air, fuel, and OC mass flow rates, operating pressure, and waste heat recovery on the performance of a natural gas-fired power plant with multistage CLC. The results of these parameters on the plant's thermal and exergetic efficiencies are presented. Based on the lower heating value, the analysis shows a thermal efficiency gain of more than 6 percentage points for CLC-integrated natural gas power plants compared to similar power plants with pre- or post-combustion CO₂ capture technologies.