Author: Xiaoge Zhang (State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University) - Hydrogen is a pivotal clean energy for mitigating energy crises and environmental pollution. Coal supercritical water gasification (SCWG) technology can convert coal into hydrogen-rich gas cleanly and efficiently. As SCWG is endothermic, an auto-thermal SCWG hydrogen production system is proposed. Gasification products are oxidized exothermically in the supercritical water oxidation (SCWO) reactor, releasing heat to sustain gasification for energy self-sufficiency. To achieve industrialization and ensure safe operation, studying the dynamic behavior of the SCWG system is essential. This work develops efficient and accurate dynamic models for key components, enabling the construction of system-level dynamic model. For the SCWFB, a 1.5-dimensional dynamic model is developed to investigate the effect of varying operating conditions. The results show that the gasification reactor temperature and hydrogen yield exhibit positive correlations with increasing water-to-coal ratio. Higher temperature of supercritical water enhances gasification efficiency, but effectiveness decreases above 900 °C. For the SCWO reactor, a reactor network model is constructed based on the flow field. Open-loop dynamic responses reveal that the fluid temperature stabilizes within 2 min, while the wall temperature takes approximately 1.1 h. Oxygen mass flow rate significantly affects the reactor performance and can be used as a control variable. According to the modular modeling principle, the dynamic models are integrated to form a comprehensive auto-thermal SCWG system model. This model is used to analyze the cold-start and transient responses to step changes of key parameters. Results reveal that the staged injection strategy constrains maximum wall temperature below 700 °C while ensuring heat supply for gasification. The developed dynamic model accurately captures system dynamics, enabling the development of advanced control strategies and facilitating industrial application.
