EFFECTS OF DRAFT TUBE HEIGHT ON SOLID CIRCULATION RATE AND PARTICLE RESIDENCE TIME IN A RCFB

Recirculating fluidized bed (RCFB) is a modified form of spouted/spout -fluid bed obtained by inserting a draft tube at the centre to contain the spout. But, with this central riser tube its design and operation s are entirely different from that of the conventional spouted/spout-f luid beds. RCFBs are used for a wide range of operations and processes . Solid circulation rate is perhaps the most important factor in predi cting the performance of a RCFB. It can be controlled by adjusting a n umber of design and operational parameters. Experiments have been carr ied out on a semicircular transparent RCFB to study the effects of dra ft tube height on solid circulation rate and particle residence time f or long draft tubes when the downcomer bed level is below the draft tu be top. It has been observed that height of the draft tube affects bot h solid circulation rate and particle residence time of a RCFB. The da ta collected may be useful in the selection of appropriate height for the draft tube of a RCFB.