Calcium looping with supercritical CO2 cycle for decarbonisation of coal-fired power plant

Abstract

State-of-the-art integration scenarios of calcium looping (CaL), which is an emerging CO2 capture technology, assume that excess heat is used to raise steam for the steam cycle and result in a net efficiency penalty of 6.0–8.0% points. In this study, a concept using the supercritical CO2 cycle (s-CO2) instead of the conventional steam cycle is proposed. Retrofit of CaL with recompression s-CO2 cycle to the 580 MWel coal-fired power plant was found to result in a net efficiency penalty of 6.9%HHV points. This is 1%HHV point lower than that for the same system linked with the steam cycle having the same turbine inlet conditions (593.3 °C/242.3 bar). A further reduction of the net efficiency penalty to 5.8%HHV points was achieved through considering a pump instead of a first CO2 compression stage and increasing the turbine inlet temperature to 620 °C and pressure to 300 bar. As the s-CO2 cycle's specific capital cost is up to 27% lower than that of the equivalent steam cycle, CaL with s-CO2 cycle is a viable option for the coal-fired power plant decarbonisation. Moreover, it can be expected that this cycle can be successfully implemented in other high-temperature looping cycles, such as chemical looping combustion.