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This work presents a design of 1000 MW S–CO 2 coal-fired power system, containing not only a new methodology of S–CO 2 power system modeling, but also the specific directions for engineering design. The coupling between computational fluid dynamic simulations at boiler scale and the mathematical modeling of the thermal cycle facilitates a high reliability of the comprehensive design. Our analysis helps identify key questions and then delivers specific directions for engineering design, especially for the pressure drop penalty in tail flue and thermal-hydraulic performance of cooling wall. The proposed flue split method coupled with parallel utilization method can not only effectively reduce the pressure drop penalty but also simplify the system heater configuration. Moreover, the thermal performance of S–CO 2 cooling wall is improved by using the flue gas recirculation and cooling wall arrangement optimization. The optimized position and proportion of flue gas extraction are further obtained. Comprehensively, the proposed design of S–CO 2 coal-fired power system enhances the system net efficiency up to 51.00%, with an efficient utilization of residual heat and cooling wall temperature below 700 °C. • A multiscale modelling platform is proposed for S–CO 2 coal-fired power system. • An improved system is obtained with system net efficiency up to 51.00% and cooling wall temperature all below 700 °C. • Flue split method and parallel utilization are developed for efficient recovery of tail flue heat. • Flue gas recirculation and cooling wall optimization are used to improve thermal safety of S–CO 2 cooling wall. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (S–CO 2) coal-fired power systems have been widely investigated due to its high efficiency and compactness. These power systems can range between 50 and 1000 MW and thus the corresponding boilers actually operate under dramatically different conditions. It is necessary to investigate the inherent relationship among different capacity S–CO 2 boilers, which not only bring new theoretical understandings but also help improve practical designs. In this work, a unified model is proposed to investigate both thermal-hydraulic and thermodynamic performance. Furthermore, it is applied to evaluate the relationship between power capacity and boiler configuration. It is shown that small capacity furnaces suffer from overheating in the furnace wall and the optimized cooling wall is suggested to tackle this issue. Moreover, it is found that high pressure drop in the cooling wall of large capacity furnaces results in significant penalty on the cycle efficiency. For the popular 1000 MW boiler, an optimized configuration is suggested by moving the second reheating into the horizontal flue of boiler, achieving a lower pressure drop and an improved cycle efficiency from 35.4% to 50.09%. Finally, three recommendations for the capacity-dependent configurations are presented. • A unified model for different capacity S–CO2 coal-fired boilers is established. • Overheating of cooling wall in boilers of small capacity is illustrated and an optimization is proposed. • Pressure drop penalty worsens in cooling wall of large capacity furnaces and results in a cycle efficiency reduction. • Three recommendations for the capacity-dependent configurations are demonstrated. [ABSTRACT FROM AUTHOR]