Experimental Study of Bubble Behavior in a Two-Dimensional Gas-Solid Tapered Fluidized Bed

The hydrodynamics of tapered fluidized beds is significantly different from the columnar beds due to the variation of the cross-sectional area along the height. The hydrodynamic behavior in tapered beds was studied experimentally using an image analysis method. The peripheral unfluidized region was quantified through the overlapping of binary images. Further, the effect of the taper angle and air velocity on the bubble size, shape, fraction, and rise velocity, along with the bed expansion ratio and the unfluidized region, was investigated. A new method is proposed to obtain expanded bed height from an image. The time-averaged bed expansion ratio and bubble fraction increase with the air velocity and decrease with the taper angle, while a reverse trend is observed for the mean unfluidized area fraction. Correlations are proposed for predicting the bubble fraction, bed expansion ratio, and unfluidized area fraction. An operating regime map is also proposed based on the unfluidized region.