| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 87 === Three sets of tapered beds with apex angle θ’s of 2.5 , 5 and 10°were used for the experiment . All beds were made of transparent Plexiglas. The glass beads with mean diameter 0.771mm were used as fluidized particles.
Experimental results showed that there were four operating regimes in a liquid-solid tapered fluidized bed. They are fixed bed, transition bed, homogeneous fluidiza-
tion bed and transport bed. The transition bed started as the bottom layer particle appeared relative movement. It came to an end of the transition regime as the upper layer particle appeared relative movement, and this velocity was chosen as the minimum fluidization velocity, which increased as the increase of loaded particle for the tapered fluidized bed.
The pressure drop-velocity diagram of the tapered fluidized bed shows that pressure drop increased with the increase of fluid velocity at the fixed bed regimes, and reached a maximum value before sharply decreased. The pressure drop decreased as the increase of the velocity at the homogeneous fluidized bed regime.
The voidage of tapered fluidized beds decreased as apex angle increase, this suppressed bed expansion and promoted mixing between different phases.
The larger the apex angle was, the higher the vessel dispersion number would be. The high vessel dispersion number means the hight extent of axial dispersion, hence more mixing in the direction of flow in a tapered fluidized bed.
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