Axial mixing of solids in turbulent fluidized beds

Abstract

Axial mixing of solids in a fluidized bed of glass beads (0.362 mm) in the slugging and turbulent flow regimes was studied in a Plexiglas column (inside diameter, 0.1 m; height, 3.0 m). The effective axial dispersion coefficient of the solid phase in the bed was determined from the axial transport of heat at steady state. The effective axial dispersion coefficient of the solid phase is almost constant in the slugging flow regime, and increases with an increase in gas velocity in the turbulent flow regime. The mixing of solids in the bed is assumed to be described by mixing tanks in series connected by perfectly mixed and plug flows. The fraction of perfectly mixed flow in the bed remains almost constant in the slugging flow regime, and increases with an increase in gas velocity in the turbulent flow regime. The effects of column size and properties of the solid particles on the effective axial dispersion coefficient of the coarse particles in the bed were determined. The effective axial dispersion dataof the solids, in terms of the Peclet number, were correlated with the Archimedes number.