Modelling the flow structure of upward-flowing gas-solids suspensions

Abstract

A simple sampling probe is developed and tested and found to be successful in measuring radial solids flux profiles in the riser of a cold model circulating fluidized bed. Radial profiles measured at different axial positions and different conditions of gas velocity and imposed solids flux are presented. These profiles have a parabolic form and exhibit a strong downward solids flow near to the riser wall. A core-annulus flow model is proposed for the refluxing dilute-phase transport regime found typically in the circulating fluidized beds, riser reactors, vertical pneumatic conveying and the freeboards of bubbling fluidized beds. The predictions of the model are tested against the experimental results presented here and compared with the findings of other workers. Agreement between predictions and experiment is encouraging.