Hydrodynamic behavior of an internally circulating fluidized bed with tubular gas distributors

To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-corner (epsilon(sD)), solids circulation rate (G(s)) and gas bypassing fraction (from down-corner to riser)'DR, and from riser to down-corner yRD) were experimentally studied. The effects of gas velocities in the riser and in the down-comer (U-R and gamma(RD)), orifice diameter in the draft tube (dor), and draft tube height (H-R) were investigated. Experimental results showed that increase of gas velocities led to increase in G(s) and gamma(RD), and slight decrease in gamma(RD). Larger orifice diameter on the draft tube led to higher epsilon(sD), G(s) and gamma(DR), but had insignificant influence on gamma(RD). With increasing draft tube height, both G(s) and gamma(DR) first increased and then decreased, while gamma(RD) first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values. (C) 2013 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.