Solid−Liquid Circulating Multistage Fluidized Bed: Hydrodynamic Study

Abstract

The solid-liquid circulating multistage fluidized bed (SLCMFB) was constructed with the principal components being the riser column and the multistage column. The riser column was made up of 50 mm i.d. and 2 m long glass pipe while the multistage column was made up of seven glass stages of 100 mm i.d. and 100 mm length. The ion-exchange resin was used as solid phase and water as fluidizing medium. The flow characteristics of SLCMFB were investigated for 0.365, 0.605, and 0.725 mm particle sizes (dry basis). The voidage in the riser and multistage column was measured using γ-ray tomography (GRT). In the riser column, the voidage was found to be maximum at the center and minimum near the wall. However, in the multistage column, voidage was found to be uniform over cross section of the column. The solid particle velocity was measured using ultrasonic velocity profiler (UVP) in the riser column. The particle velocity profiles show similar trend as the voidage, confirming the existence of the radial non-uniformity in the riser column. Further, the non-uniformity was analyzed using the drift flux model (DFM) and the effect of particle size and superficial liquid velocity on the non-uniformity was also investigated.