[Objective] To elucidate the multi-field coupling mechanisms of gas-solid hydrodynamics, heat transfer, and chemical reactions within an industrial-scale biomass circulating fluidized bed (CFB) gasifier, and to investigate the intensification mechanisms of oxygen-enriched gasification. This study aims to provide a theoretical foundation for engineering scale-up and operational optimization of biomass clean conversion. 

[Methods] A full-scale 3D CFD numerical model was established based on the QFD-6-S industrial gasifier. The gas-phase turbulence was modeled using the standard k-ε model, while the fluidization of quartz sand bed material was simulated via the Eulerian-Eulerian two-fluid model. The complex thermochemical conversion processes of biomass, including drying, pyrolysis, combustion, and gasification, were modeled using the discrete phase model (DPM) in a Lagrangian framework. A key methodological highlight of this work is the precise characterization of non-spherical biomass particles. Recognizing that biomass particles naturally exhibit non-spherical geometries, we derived four distinct drag coefficient correlations for spherical, cylindrical, blocky, and ellipsoidal shapes based on Direct Numerical Simulation (DNS) results. These correlations were subsequently incorporated into the CFD solver through User-Defined Functions (UDFs), significantly improving the accuracy of the gas-solid interactions. Furthermore, thermogravimetric analysis (TGA) was conducted to obtain intrinsic kinetic parameters. The numerical predictions were rigorously validated against experimental data from a laboratory-scale CFB gasifier. 

[Results] The validation results demonstrated that the maximum relative deviation between the simulated gasification efficiency and the experimental data was less than 2.5%. In terms of performance comparison, three operating conditions were comparatively analyzed. Pure rice husk air gasification achieved an efficiency of 72.5%. When blending 75% rice husks with 25% pine wood under air conditions, the efficiency decreased to 66.8% due to the high volatile matter content (75.66%) of pine wood, which led to concentrated oxygen depletion in the dense-phase zone. In contrast, 40% oxygen-enriched gasification yielded the best performance, boosting the gasification efficiency to 76.6%. 

[Conclusion] Based on the above findings, the study reveals the synergistic strengthening mechanisms of 40% oxygen-enriched gasification: it eliminates the heat absorption and dilution effects of N₂, elevates the overall furnace temperature by approximately 80℃, and establishes a positive feedback loop of "enhanced combustion → temperature rise → promoted endothermic reduction reactions" (such as C+CO₂→2CO and C+H₂O→CO+H₂). Furthermore, the results strongly demonstrate that for industrial CFB simulations, the correction for non-spherical particle drag (where ellipsoidal and blocky particles exhibit substantially higher drag coefficients than spherical ones) is indispensable for accurately predicting particle trajectories, residence time distributions, and consequently, the degree of conversion. These findings offer a robust theoretical and data-driven foundation for the industrial-scale application of oxygen-enriched co-gasification of agricultural and forestry solid wastes, and provide critical insights for optimizing reactor design and mitigating alkali-induced slagging.