The characteristics of particle flow in the overflow and underflow standpipe of fluidized beds

Characteristics of particle flow in the standpipes of a 10 cm I.D. x 120 cm high fluidized bed were investigated. The standpipes used in this experime nt were vertical overflow and vertical underflow standpipes. Sand particles and polyethylene powders were employed as the bed materials. The effects o f standpipe diameter, gas velocity and particle properties on the solid now rate were determined. The experimental results showed that the flow behavi ors of solids through the overflow and underflow standpipes are different w ith variations of operating conditions. For both standpipes, the mass flow rate of solids was strongly dependent on the standpipe diameter. For the ov erflow standpipe, the increase of gas velocity increased the solids flow ra te. But for the underflow standpipe it decreased the solid flow rate. From the measured pressure drops, solid fractions in the standpipes were determi ned by the momentum balance. The obtained experimental data of solids mass flow rate were well correlated with the pertinent dimensionless groups for underflow as well as overflow standpipes.