Fluidization of Geldart D type particles in a shallow vibrated gas-fluidized bed

Abstract

The fluidization behavior of a binary mixture of Geldart D type particles in a shallow vibrated gas-fluidized bed (VFB) was systematically studied by using a high-speed dynamic camera. This study drew a comparison between the fluidization of a VFB and a conventional gas-fluidized bed (CFB). The results show that the characteristic air velocities in a VFB, such as the minimum fluidization velocity, the minimum bubbling velocity and the minimum slugging velocity, have considerable reductions in comparison with that in a CFB. It is indicated that the vibration significantly changes the gas-solid two-phase flow structure and improves the dispersion uniformity of air flow in the bed. The air pressure waves, as the main transmission mode of vibration energy, can improve the air-solid contact efficiency and organize the excess fluidizing air to form periodic slugs. In a VFB of Geldart D type particles, there are four distinct fluidization regimes: static bed, bubbling fluidization, slugging fluidization and turbulent fluidization. The results show that a good performance of density segregation in a VFB of Geldart D type particles happens in the stage of gentle slugging.