CPFD Simulation of Hydrodynamic Characteristics of Multiple Particles Mixing in a Circulating Fluidized Bed

Computational particle fluid dynamics method is utilized to study the influence of polydisperse and monodisperse particle size distribution, fuel addition, and biomass mixing ratio on the gas-solid flow behavior in a pilot-scale circulating fluidized bed (CFB). Numerical results show that a polydisperse system with different particle sizes can enhance the fluidization quality and the uniformity of the particle volume fraction in comparison with a monodisperse system with uniform particle sizes. When fuel is present in the CFB, the disturbance at the circulation inlet is eliminated and the particle aggregation effect at the wall is reduced. Furthermore, the particle volume fraction, pressure, and particle velocity distributions change only slightly as the biomass increased from 0% to 20% or from 50% to 100% of the total fuel mass. However, as the biomass ratio increases from 20% to 50%, the pressure drop in the riser decreases and the back-mixing degree at the riser wall weakens.