The bubble size and rise velocity of bubble-induced three-phase inverse fluidized bed (BIFB)

The bubble size and rise velocity were investigated in detail using a new telecentric photographic probe in a pilot-scale bubble-induced three-phase inverse fluidized bed (BIFB). By the influence of the bubble flow behavior, the particle bed goes through four different flow regimes with increasing gas velocity in BIFB. An obvious normal bubble size distribution caused by bubble coalescence and breakup was observed. A parameter of "size span" was proposed to describe the distribution width of bubble size. The average bubble size increases with the axial distance from the column bottom and with the gas velocity until reaching a relatively stable size. The radial distributions of the average bubble size are almost uniform but experience a decreasing trend near the column wall. The bubble rise velocity increases with the bubble size and the gas velocity. An empirical equation was established to predict successfully the bubble rise velocity in BIFB.