High-fidelity simulation of the 3-D full-loop gas-solid flow characteristics in the circulating fluidized bed

The full-loop gas-solid motions in a three-dimensional circulating fluidized bed are numerically modeled using the computational fluid dynamics combined with the discrete element method. The time-averaged flow characteristics and the particle-scale details related to solid motion are discussed. The results show that solid motion shows an 'S' rising path in the riser but a spirally falling behavior in the cyclone. Typical core-annulus flow structure and non-uniform distribution of solid holdup appear in the riser. The inside and outside swirling flows of gas motion as well as the fishtailing phenomenon are captured in the cyclone. The solid residence time in the riser shows an early-occurred peak with a long tail. In the riser, details related to solid motion at the particle-scale level are obtained. The sudden changes of these particle-scale details when increasing the superficial velocity may be considered to be a new criterion of identifying the flow regime change. (C) 2014 Elsevier Ltd. All rights reserved.