Bed expansion and bubble wakes in three‐phase fluidization

Abstract

Abstract The expansion characteristics of gas‐liquid fluidized beds have been measured for beds of glass ballotini and sand with particle sizes ranging from 120 to 775 microns. This data has been used in conjunction with recent measurements of bubble properties to predict the proportion of wake associated with bubbles rising through the bed using a modification of the theory proposed by Ostergaard to explain the contraction observed when gas is introduced into a liquid fluidized bed. Three‐pase fluidization has also been observed by photography in a two‐dimensional bed and the results are in substantial agreement with the calculations based on expansion behavior and bubble properties. The bubble wakes in a three phase system consist not only of a stable portion carried with the bubbles but also of vortices shed by the bubbles. A simplified model has been used to demonstrate that these vortices may contribute significantly to the observed contraction.