Thermodynamic analysis of the series system for the supercritical water gasification of coal-water slurry.

Supercritical water gasification (SCWG) is a potential clean technology for utilizing solid fuel or waste without producing gaseous pollution. Efficient energy integration and recovery strategies play an essential role in the endothermal gasification process. Previous approaches have only focused on the heat source or heat transfer with very little attention to the utilization of the abundant supercritical water in the product gas. This paper proposes an innovative series design for heat integration in the SCWG system while taking the gasification process into account. Notably, the first-stage oxidized hot fluid containing abundant water is directly utilized as the gasification agent for the second-stage gasification reactor. The thermodynamic analysis shows that the cold gas and exergy efficiency in the two-stage series system is 17.4% and 15.0% higher than in the previous single-stage gasification reactor. The sensitivity analysis illustrates that increasing series stages and feedstock concentration while decreasing oxidation proportion and the agent-slurry ratio can improve the overall system efficiency by decreasing the demand for oxygen, power consumption, and heat transfer rate. The series design should offer an innovative and practical approach for the heat supply in the industrial SCWG plant. • Series design for supercritical water gasification of coal-water slurry was simulated. • The optimized cold gas and exergy efficiency is improved by 17.4% and 15.0%. • The Sankey diagram shows that the series design reduces reaction and heat recovery exergy loss. • Higher series stages facilitate methane production, less oxygen demand, and higher efficiency. • The critical parameters were studied by sensitivity analysis for optimization. [ABSTRACT FROM AUTHOR]