Effect of flue gas recirculation on efficiency of an indirect supercritical CO_2 oxy-fuel circulating fluidized bed power plant

摘要

This paper deals with and oxy-fuel circulating fluidized bed (Oxy-CFB) power plant with air separate unit (ASU), CO2 compression and purification unit, and an indirect supercritical CO2 cycle. This novel power plant was designed and modeled by using Aspen Plus at commercial scale to investigate the possibility and the effect of recirculated flue gas conditions. The indirect S-CO2 oxy-CFB power plant had higher net efficiencies compared with oxy-CFB power plant with steam cycles because the phase of CO2 does not change during the operation. Also, the effect of the amount of water retained in flue gas stream generated at the CFB boiler on the overall net efficiency was analyzed. By decreasing the temperature of recirculated flue gas from 90 degrees C to 40 degrees C, water retained in flue gas decreased, and input O-2 concentration in combustor increased from 34.7 to 38.5 vol%. When flue gas recirculation temperature was 40 degrees C, the boiler efficiency was 99.6%, and the overall net efficiency was 43.1%. Although approximately 20% of the total power is the power consumption of the ASU and CPU, high net efficiency was achieved in this novel power plant. (C) 2021 Elsevier Ltd. All rights reserved.