Effect analysis of feed structure and operation parameters on gasification reaction in the supercritical water fluidized bed via CFD-DEM method

The supercritical water fluidized bed is a reactor that can be used for hydrogen production by biomass gasification. In this paper, a coupled flow-heat-reaction model of a supercritical water fluidized bed is constructed based on the computational fluid dynamics (CFD)- discrete element method (DEM) method. The feed structure is optimized in terms of the feed angle and inlet distribution. The results indicate that the B-type structure (45° downward injection) performs best under single-inlet conditions, while the G-type (45° downward symmetry injection) is optimal for symmetric double inlets, and the N-type (with a spacing of 2d) improves multi-inlet distribution and bed uniformity. Additionally, the kinetics of glucose gasification reactions are analyzed to identify the optimal feed structure based on gasification performance, focusing on the effects of wall temperature and flow ratio on the temperature and reaction fields within the fluidized bed. Compared to the initial structure, the B-type, G-type, and N-type structures are better to improving hydrogen production and gasification efficiency. Moreover, higher wall temperatures and lower flow ratios of supercritical water to glucose benefits to enhancing hydrogen yield and gasification efficiency. This study contributes to advancing hydrogen production technology by biomass gasification in supercritical water.