BUBBLE-SIZE CONTROL IN A 2-DIMENSIONAL FLUIDIZED-BED USING A MOVING DOUBLE-PLATE DISTRIBUTOR

Pulsating the flow in a fluidized bed by using a moving double plate d istributor (MDPD) lo control the bubble size and enhance the fluidizat ion characteristics is a new approach. In this novel design, a second plate Is placed under the existing distributor such that it can make a reciprocating motion generating pulses to the flow field. The frequen cy and amplitude of the pulsation can be adjusted to break up the larg e bubbles in the bed. The aim of this study is to investigate the effe ct of pulsation on the bubble size, bubble speed, bubble fraction and bed expansion in a fluidized bed. For this purpose, the bubbles were f ollowed two-dimensional fluidized bed with turnip seed and sand as the bed material for different pulsation frequencies and operating veloci ties. Bubble size, speed and bed expansion were measured for pulsed fl ow and compared with those of continuous flow. Image processing techni ques were utilized to measure the bubble fraction. Interesting bubble flow patterns were observed and a significant decrease in bubble size was achieved for the pulsed flow. (C) 1998 Elsevier Science S.A.