Transport Disengaging Height and Elutriation Rate of a Vortexing Fluidized Bed.

Abstract

A systematic investigation on the transport disengaging height (TDH) in a vortexing fluidized bed (VFB) cold model was conducted in this study. The elutriated fine particles from a vortexing fluidized bed which has a diameter of 0.19 m was collected and measured by using a continuous receiving system. The experimental results indicate that the elutriation rate decreases significantly with the secondary air injection. The TDH increases with the primary air velocity and decreases with secondary air velocity and the static bed height. It is also found that the effect of the secondary air injection height on TDH can be neglected. Comparing experimental data in the vortexing fluidized bed (VFB) and the bubbling fluidized bed (BFB), the effect of the swirling flow on the transport disengaging height is not conspicuous. The freeboard of a vortexing fluidized bed can be divided into the free entrainment zone (FEZ) and the swirling effect zone (SEZ). The length of the swirling effect zone (SEZ) is the dominating factor for elutriation. A correlation is developed to estimate the TDH in the vortexing fluidized bed. The TDH is found to be a function of the primary air velocity, the ratio of the tangential air flow rate to the primary air flow rate, and the static bed height.