Three-dimensional numerical study on flow dynamics characteristics in supercritical water fluidized bed with consideration of real particle size distribution by computational particle fluid dynamics method

Supercritical water fluidized bed is a promising reactor which can realize the efficient and clean gasification of coal to produce hydrogen. As the high pressure and temperature inside supercritical water fluidized bed, the study of the detail flow behaviors needs the help of numerical method. Considering the limitation of the two-fluid method and discrete element method, the computational particle fluid dynamics method was applied to this work. When particle size distribution was taken into consideration, the simulated results showed that the transformation from fixed bed regime to fluidized bed regime is a gradual process. With the increase in superficial fluid velocity, particles in small diameter migrate to the top of the bed and there exits layering phenomenon in the bed. Besides, though the particles are categorized as Geldart B group, the minimum fluidization velocity is not equal to the minimum bubbling fluidization velocity and there is a complicated bed expansion process after incipient fluidization. The bed expansion process is also influenced by the particle size distribution.