Hydrodynamics of a bubble-driven liquid-solid fluidized bed

A new fluidization system, the bubble-driven liquid-solid fluidized bed, adopting particles with a slightly higher density than the fluid, has been proposed. During the experiment process, air was introduced into the bottom of the column as driving force, and superficial gas velocity ranged from 0 to 28 mm/s and liquid was continuous phase but maintained at the stationary state. The variation of pressure drops in the bottom section near the gas distributor was measured to identify the demarcation of flow regimes and determine the loose velocity (U_loose) and initial fluidization velocity (U_in). It was found that U_loose and U_in both increase with the initial hydrostatic height but are independent of the initial liquid height. Moreover, solids holdup was analyzed using a photographic technique while gas holdup was calculated from the pressure drop variation and solids holdup. A non-uniform axial solids distribution exists for all gas velocities. Additionally, two fluidization mechanisms were proposed based on the experimental observations.