CFD-DEM simulation of polydisperse gas-solid flow of Geldart A particles in bubbling micro-fluidized beds

Abstract

Polydisperse particles are ubiquitous, yet their unique roles are inadequately understood. In this study, CFD-DEM study on the fluidization of polydisperse particles in bubbling micro-fluidized beds was performed. The method was firstly validated by the experimentally measured bed expansion characteristics and voidage of emulsion phase. Detailed analysis of bed hydrodynamics was then performed. It was shown that (i) gas back-mixing is minimized in micro-fluidized beds due to the near plug gas flow; (ii) bubble pattern in micro and large fluidized beds is similar; (iii) particle size distribution (PSD) enhances fluidization quality in terms of higher bed expansion and higher voidage of emulsion phase, where ”fines” is the root cause; and (iv) significant axial segregation is only observed in the case of wide PSD, and microscale segregation analysis indicates that coarse particles are preferentially following the motion of bubbles. Present study not only offers insights into the role of PSD in gas fluidization, but also sheds light on the similarity and difference between micro and large fluidized beds.