Hydrodynamic Study of a Gas–liquid–solid Bubble Column Employing CFD–BPBM Method

Abstract

AbstractThe computational fluid dynamics – bubble population balance model (CFD–BPBM) was employed to predict the hydrodynamic characteristics of a gas–liquid–solid bubble column. A 3D time dependent numerical study was performed and the bubble size distributions at the conditions of different superficial gas velocity (0.089 m/s–0.22 m/s), solid volume fraction (0.03–0.30) and particle density (2500 kg/m3–4800 kg/m3) in the three–phase system were investigated, and the simulation results were compared with the experimental results. The bubble diameters ranging from 1 mm to 64 mm were divided into ten classes. The predicted pressure changing with the bed height had a good agreemeet with the experimental result. The bubble number density predicted decreased when the bubble size increased at each superficial gas velocity, and the bubble coalescence rate became greater than the breakup rate when Ugshifted from 0.089 m/s to 0.16 m/s. The bubble interaction was similar at 0.16 m/s and 0.22 m/s both at particle size dp= 75 μm and 150 μm. The bubble size corresponding to the maximum of the bubble volume fraction increased as Ugincreased. The particles can make the bubble break up and coalesce simultaneously when the solid volume fraction was larger than 0.20, and therefore the particles had a contribution to both of the bubble coalescence and breakup in the bubble coalescence regime (Ug= 0.16 m/s). The effect of the particle density was similar with that of the solid volume fraction. Increasing the particle density can enhance the breakup rate of the large bubbles.