Integration of the steam cycle and CO2 capture process in a decarbonization power plant

•Energy equilibrium in CO2 capture process is deeply analyzed in this paper.•System integration is conducted in a coal-fired power plant with CO2 capture.•The steam ejector is introduced to utilize the waste energy from CO2 capture process.•Thermodynamic, exergy and techno-economic analyses are quantitatively conducted.•Energy-saving effects are found in the new system with minimal investment.

A new integrated system with power generation and CO2 capture to achieve higher techno-economic performance is proposed in this study. In the new system, three measures are adopted to recover the surplus energy from the CO2 capture process. The three measures are as follows: (1) using a portion of low-pressure steam instead of high-pressure extracted steam by installing the steam ejector, (2) mixing a portion of flash-off water with the extracted steam to utilize the superheat degree of the extracted steam, and (3) recycling the low-temperature waste heat from the CO2 capture process to heat the condensed water. As a result, the power output of the new integrated system is 107.61 MW higher than that of a decarbonization power plant without integration. The efficiency penalty of CO2 capture is expected to decrease by 4.91%-points. The increase in investment produced by the new system is 3.25 M$, which is only 0.88% more than the total investment of a decarbonization power plant without integration. Lastly, the cost of electricity and CO2 avoided is 15.14% and 33.1% lower than that of a decarbonization power generation without integration, respectively. The promising results obtained in this study provide a new approach for large-scale CO2 removal with low energy penalty and economic cost.