Proposal and performance analysis of a novel hydrogen and power cogeneration system with CO₂ capture based on coal supercritical water gasification

To establish a sustainable energy system, it is essential to achieve low-carbon and clean utilization of coal. In this study, a novel hydrogen and power cogeneration system with full CO₂ capture that based on coal supercritical water gasification (SCWG) is proposed. Hydrogen is separated from syngas produced by coal SCWG, and the remaining combustible gas is burned to generate power. Moreover, supercritical CO₂ cycle is integrated within the cogeneration system to recover the waste heat with high exergy efficiency. Thermodynamic performances, effects of key operation parameters and off-design performances under part-load conditions of the cogeneration system are analyzed. Under the design condition, the cogeneration system produces 20.26 mol kg⁻¹ hydrogen and generates 8746 kJ kg⁻¹ net power, achieving the high energy efficiency and exergy efficiency of 54.77 % and 52.54 %. The exergy efficiency of cogeneration system can be enhanced by optimizing the operation parameters, which is increased by 0.42 %, 4.03 % and 1.10 % with the optimal coal water slurry concentration (17.5 %), higher gasification temperature (750 °C) and higher gas turbine inlet parameters (1500 °C/3 MPa), respectively. The cogeneration system performance decreases with the power load, and the exergy efficiency decreases by 9.61 % when the system power load reduces from 100 % to 30 %.