To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer (É"sD), solids circulation rate (Gs) and gas bypassing fraction (from down-comer to riser γDR, and from riser to down-comer γRD) were experimentally studied. The effects of gas velocities in the riser and in the down-comer (UR and UD), 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 Gs and γDR, and slight decrease in γRD. Larger orifice diameter on the draft tube led to higher É"sD, Gs and γDR, but had insignificant influence on γRD. With increasing draft tube height, both Gs and γDR first increased and then decreased, while γRD first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values.
- Gas bypassing fraction
- Internally circulating fluidized bed
- Solids circulation rate
- Solids holdup