The effect of mechanical vibration on gas fluidization of a fine aeratable powder

Fluidization behaviour of a fine aeratable FCC powder assisted by mechanical vibration was studied in a 85 mm i.d. transparent column. The investigated parameters of vibration were the peak acceleration value (a/g = 0.5, 1 and 2) and the frequency (between 7 and 200 Hz). The most significant variations obtained by changing these parameters regard the voidage of the fixed bed, the effects of aeration on bed expansion and fluidization, the maximum bed expansion and the onset of bubbling conditions. The typical fluidization curve in presence of mechanical vibration is characterized with the introduction of key fluidization velocities: a minimum bed expansion velocity, a minimum velocity for fluid dynamic suspension, the minimum bubbling velocity and a minimum velocity for stable bubbling. The possibility to apply the Ergun equation under gas fluidization assisted by vibration was also verified. Differential pressure drops at different heights inside the bed were used to investigate on the effects of vibrations on the gas fluidized bed. Changes of differential pressure drop along the bed were interpreted in the light of some internal bed structure.