Eulerian-Lagrangian simulation of the full-loop gas-solid hydrodynamics in a pilot-scale circulating fluidized bed

Abstract

The full-loop gas-solid hydrodynamics in a pilot-scale circulating fluidized bed (CFB) is numerically investigated by using multi-phase particle-in-cell (MP-PIC) method. In this method, fluid motion is resolved under Eulerian framework while particle motion is tackled under Lagrangian framework. The numerical results agree well with experimental data, demonstrating the reasonability of the MP-PIC method in simulating dense gas-solid systems. The main features of gas-solid flows in the full-loop CFB are qualitatively predicted, with a typical core-annulus flow structure in the riser. A large pressure gradient of gas phase in the bottom region and top region of riser reflects the turbulent and chaotic gas-solid flows in these two regions. Enlarging superficial gas velocity leads to a more non-symmetrical pattern of axial gas velocity, indicating the enhanced influence of recycle structure on gas-sold uniformity under the higher superficial gas velocity. The solid residence time (SRT) distribution in the riser exhibits a feature of early peak and a long tail, which can be well fitted by a lognormal probability distribution function. Enlarging superficial gas velocity gives rise to a decreased mean value and narrower distribution of the solid residence time in the riser, reflecting the depressed solid back-mixing intensity in this condition.