(201c) Effect of Fluidizing Gas Humidity on Bubble Behaviors in a Gas-Solid Fluidized Bed under Vibrated Conditions

Effect of the fluidizing gas humidity on bubble behaviors was examined in a two-dimensional fluidized bed under vibrated conditions. Vertical and horizontal vibrations were subjected to the fluidized bed. The humidity of fluidizing gas was controlled between 40 to 90 %. The frequency and the amplitude of vibration were set 14.8 - 29.8 Hz and 1.5 - 6.0 mm, respectively. Particle used in this study were spherical glass beads and their mean diameters were 43, 89 and 198ìm which belonged to the Geldart group A or B categories. As the humidity of fluidizing gas increased, the bubble rising velocity increased, while the bubble diameter became smaller. On the other hand, the aspect ratio of rising bubble became higher as the gas humidity increased. From this, the increment tendency of bubble rising velocity with the gas humidity is interrelated with the change of bubble shape in the humiditified conditions. When the horizontal vibration was added to the bed, the effect of gas humidity on the bubble behavior was not significant, which indicated that the horizontal vibration prevented the bubbles from elongating. On the other hand, for vertical vibration, the bubbles were elongated at the lower gas humidity than that for non-vibrated condition. From this, the vibration direction had a significant influence on the bubble behavior under humiditified condition.