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Abstract As a high-performance power cycle, S-CO 2 cycle has drawn a lot of attention in various energy utilization field. As one of the clean and efficient forms for coal utilization, coal-fired power plants still need novel power generation systems to have rational use of coal. So, it is necessary to explore the characteristic when a coal-fired power system integrated with S-CO 2 cycle. However, this application is confronted with many challenges related to boiler, such as pressure drop problem due to large mass flow rate and residual heat problem due to narrow CO 2 temperature difference. Focus on the residual heat problem, in this paper, a coupling analysis model between boiler and reheat S-CO 2 cycle is established. The proposed system consists of a thermal-hydraulic calculation module in boiler, a residual heat treatment module in tail flue and a thermodynamic calculation module of S-CO 2 cycle. The three modules can make the calculation results more credible for cycle characteristics. All the modules are programmed by Fortran. Base on the analysis result, the residual heat problem can be solved by raising turbine inlet pressure. But when turbine inlet temperature is higher, the turbine inlet pressure will be raised unacceptable. By adding a flue gas cooler (FGC), above limitation will be removed. So, in a certain temperature range, adding an FGC is a simple and effective way to solve residual heat problem. [ABSTRACT FROM AUTHOR]

• New combined S-CO 2 power cycles for coal-fired power plants were proposed. • A numerical model of S-CO 2 cycle for coal-fired power plants was implemented. • Parametric analysis and exergy analysis of the proposed cycles are carried out. • Net cycle efficiency and specific power are improved by the new cycles. Supercritical CO 2 (S-CO 2) power cycle has been proven to be an efficient way to improve the efficiency of the coal-fired power plants. In this paper, new combined S-CO 2 power cycles for coal-fired power plants were proposed to improve the performances of S-CO 2 power cycle. A numerical model of S-CO 2 cycle for coal-fired power plants was implemented. The effects of the key operating parameters on the performance of the new combined S-CO 2 power cycles are numerically investigated and exergy destruction in each component is analysed. As a result, it can be found that the net cycle efficiency and specific power are improved by the new combined cycles, meanwhile the flue gas temperature is reduced. In contrast to the reference cycle, the net cycle efficiency and specific power of the combined Brayton cycle can be increased by 1.6% and 14.9 kJ/kg, respectively. Furthermore, the cycle exergy efficiency can be improved by 2.34%. As a result, a new insight is introduced for the development of S-CO 2 Brayton cycles for coal-fired power plants. [ABSTRACT FROM AUTHOR]