The fluidization behavior of nano and sub-micron powders belonging to group C of Geldart＇s classification was studied in a mechanically vibrated fluidized bed （vibro-fluidized bed） at room temperature. Pretreated a...The fluidization behavior of nano and sub-micron powders belonging to group C of Geldart＇s classification was studied in a mechanically vibrated fluidized bed （vibro-fluidized bed） at room temperature. Pretreated air was used as the fluidizing gas whereas SiO2. Al2O3, TiO2, ZrSi, BaSO4 were solid particles. Mechanical vibration amplitudes were 0.1, 0.25, 0.35, 0.45mm, while the frequencies were 5, 20, 30, 40 Hz to investigate the effects of frequency and amplitude of mechanical vibration on minimum fluidization velocity, bed pressure drop, bed expansion, and the agglomerate size and size distribution, A novel technique was employed to determine the apparent minimum fluidization velocity from pressure drop signals. Richardson-Zaki equation was employed as nano-particles showed fluid like behavior when fluidized. The average size of agglomerates formed on top of the bed was smaller than those at the bottom, Size distribution of agglomerates on top was also more uniform compared to those near the distributor. Larger agglomerates at the bottom of the bed formed a small fraction of the bed particles. Average size of submicron agglomerates decreased with increasing the frequency of vibration, however nano particles were less sensitive to change in vibration frequency. Mechanical vibration enhanced the quality of fluidization by reducing channeling and rat-holing phenomena caused by interparticle cohesive forces.展开更多
Measurement of bubble size and local average bubble rise velocity was carried out in a vertically sinusoidal vibre-fluidized bed. Glass beads of Geldart group B particles were fluidized at different gas velocities, wh...Measurement of bubble size and local average bubble rise velocity was carried out in a vertically sinusoidal vibre-fluidized bed. Glass beads of Geldart group B particles were fluidized at different gas velocities, while the bed was vibrated at different frequencies and amplitudes to study their effects on the bubble behavior. This is compared with the case of no vibration in a two-dimensional bed and it is concluded that with vibration the local average bubble size dbav, decreases significantly, especially at minimum bubbling velocity. The average bubble size increases slightly with increasing vibration frequency and amplitude. The local average bubble rise velocity is higher than that with no vibration, though with increasing vibration frequency and amplitude, it does not change significantly.展开更多
基金the financial support received from Ontario Research Fund for this study
文摘The fluidization behavior of nano and sub-micron powders belonging to group C of Geldart＇s classification was studied in a mechanically vibrated fluidized bed （vibro-fluidized bed） at room temperature. Pretreated air was used as the fluidizing gas whereas SiO2. Al2O3, TiO2, ZrSi, BaSO4 were solid particles. Mechanical vibration amplitudes were 0.1, 0.25, 0.35, 0.45mm, while the frequencies were 5, 20, 30, 40 Hz to investigate the effects of frequency and amplitude of mechanical vibration on minimum fluidization velocity, bed pressure drop, bed expansion, and the agglomerate size and size distribution, A novel technique was employed to determine the apparent minimum fluidization velocity from pressure drop signals. Richardson-Zaki equation was employed as nano-particles showed fluid like behavior when fluidized. The average size of agglomerates formed on top of the bed was smaller than those at the bottom, Size distribution of agglomerates on top was also more uniform compared to those near the distributor. Larger agglomerates at the bottom of the bed formed a small fraction of the bed particles. Average size of submicron agglomerates decreased with increasing the frequency of vibration, however nano particles were less sensitive to change in vibration frequency. Mechanical vibration enhanced the quality of fluidization by reducing channeling and rat-holing phenomena caused by interparticle cohesive forces.
文摘Measurement of bubble size and local average bubble rise velocity was carried out in a vertically sinusoidal vibre-fluidized bed. Glass beads of Geldart group B particles were fluidized at different gas velocities, while the bed was vibrated at different frequencies and amplitudes to study their effects on the bubble behavior. This is compared with the case of no vibration in a two-dimensional bed and it is concluded that with vibration the local average bubble size dbav, decreases significantly, especially at minimum bubbling velocity. The average bubble size increases slightly with increasing vibration frequency and amplitude. The local average bubble rise velocity is higher than that with no vibration, though with increasing vibration frequency and amplitude, it does not change significantly.
