CFD simulation of air-blown coal gasification in a fluidized bed reactor with continuous feedstock

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Air-blown gasification in a lab-scale bubbling fluidized gasifier reactor with continuous coal feedstock is numerically investigated by employing the reactive multiphase particle-in-cell (MP-PIC) approach in which the gas and solid motions are respectively tracked in the Eulerian and Lagrangian frameworks. After comparing the numerical predictions with experimental measurements, the particle-scale thermochemical properties of coal particles together with the effects of operating parameters are comprehensively explored. The results show that the lateral and vertical segregation in the gasifier remarkably affects the thermochemical distributions of coal particles (i.e., temperature, heat transfer coefficient, constituents, residence time, slip velocity, and particle Reynolds number). Close to coal inlet, coal particles have a small temperature, large heat transfer coefficient, and high content of moisture and volatile. Spatial distribution of slip velocity is similar to that of particle Reynolds number. Enlarging the air flow rate strengthens the coal gasification due to the decreased mass and the promotion of char conversion in the gasifier. The residence time distribution of coal particles in the reactor presents an “early peak with a long tail” feature. The air flow rate and gasification temperature exert an obvious impact on the carbon content in the exiting coal particles. The increase of gasification temperature and air flow rate obviously promote the carbon conversion efficiency. The numerical results regarding the thermochemical behaviors of coal gasification in the bubbling fluidized gasifier reactor shed light on the design and optimization of this kind of reactor.