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• An integration system with adaptive modification module for 1000 MW S-CO 2 Brayton cycle and coal-fired boiler is developed. • The effects of typical layout parameters on thermal-hydraulic performance are obtained. • A layout with the highest thermal-hydraulic performance is proposed. • Accurate engineering design of S-CO 2 coal-fired power plants can be realized based on the integration system. An integration system for 1000 MW S-CO 2 connected-top-bottom power cycle with overlap utilization and coal-fired boiler is developed. The adaptive modification module is introduced to eliminate the non-convergence for S-CO 2 superheater thermal calculation in the system iteration. Thermal-hydraulic performance in terms of thermal performance, cycle efficiency, heater configurations, heater areas and final parameter evenness are discussed. Firstly, the strong constraint effects of inlet and outlet parameters on superheater thermal calculation convergence are demonstrated and the adaptive modification module is established. Secondly, based on the detailed thermal-hydraulic analysis, different layouts are compared to identify the flow path way and the heat absorption of S-CO 2 flow in different heating processes. The midpoint between the two peaks of heat flux is recommended as the start point for the cold fluid placement in cooling wall arrangement. Finally, a new layout is proposed to obtain the highest overall thermal-hydraulic performance, with a net power efficiency up to 47.57% and a total heater area of 316426.18 m2. The design sequences for S-CO 2 coal-fired boiler heaters are recommended as well. [ABSTRACT FROM AUTHOR]

The Supercritical carbon dioxide (S–CO 2) Brayton cycle is considered as a promising alternative to traditional steam Rankine cycle due to its high efficiency and compactness. However, in coal-fired power system, the S–CO 2 temperature at cooling wall entrance is newly recognized quite high, leading to an over-temperature crisis. A coupled model of combustion and S–CO 2 heat transfer was established to predict cooling wall temperature of a 1000 MW S–CO 2 Brayton coal-fired boiler. Based on the module arrangement in S–CO 2 boiler, the "cold S–CO 2 -hot fire matching and cascaded temperature control" principle in 1D model was proposed to reduce the cooling wall temperature. Three methods were examined including the low-temperature fluid matching high heat flux burner region, the counterflow, and more cold fluid in circulation drained to match high heat flux zone. The results show that the optimal arrangement can significantly reduce the temperature in overheated region 12–44 °C and eliminate the local hot spot. In addition, the 3D model was developed to obtain the maximum wall temperature and the uneven temperature in the circumferential direction. The employment of spiral cooling wall could alleviate circumferential unevenness and reduce wall temperature. The present work can provide important guidance to design of S–CO 2 Brayton coal-fired power system. • A coupled model of combustion and S–CO 2 heat transfer was established to predict cooling wall temperature. • The "cold S–CO 2 -hot fire matching and cascaded temperature control" principle in 1D model was proposed. • The uneven temperature distribution in circumferential direction of cooling wall in 3D model was calculated. • The spiral tubes of cooling wall could effectively relieve uneven problem and reduce wall temperature. [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]