Thermodynamic and economic performance of oxy-combustion power plants integrating chemical looping air separation

Abstract

Abstract Oxygen supply from cryogenic air separation unit (ASU) causes high economic cost and energy penalty, which hinders the practicability of oxy-combustion technology. Chemical looping air separation (CLAS) as a thermodynamic-efficient and cost-effective approach can satisfy the oxygen demands for oxy-combustion power plants. To optimize process configuration and identify the effect of recycling position for oxy-combustion power plants integrating CLAS (i.e. OXY-CLAS), the paper focuses on process simulation, thermodynamic analysis and techno-economic evaluation of two typical OXY-CLAS systems. For sastifying the oxygen concentration demand in oxy-combustion, the mixture of recycled flue gas and steam is adopted as the reduction medium in CLAS. For OXY-CCLAS (using cold recycled flue gas as oxygen releasing medium in CLAS), its net efficiency and exergy efficiency are 4.80 and 4.54% points higher than those of oxy-combustion coupled with cryogenic ASU, respectively. Meanwhile, its cost of electricity is reduced about 12.18% whilst its CO2 avoidance cost and CO2 capture cost decrease about 48.14% and 39.34%, respectively. When compared between two OXY-CLAS systems, OXY-WCLAS (utilizing warm recycled flue gas in CLAS) exhibits better performance both on thermodynamic and economic aspects. The exergy efficiency of WCLAS system is 1.29% points higher than that of CCLAS system.