Hydrodynamics Of Centrifugal Fluidized Beds And Thermal Analysis Of Drying Process

Centrifugal fluidization is a new technology for gas-solid contact. It has a high efficiency for heat-mass transfer, but presents complicated hydrodynamic and thermodynamic behaviors. To promote the understanding of these complex behaviors and the development of centrifugal fluidized bed (CFB), the paper investigated the bed expansion and particle entrainment, and analyzed the thermodynamic process in CFB dryer.Based on the basic hydrodynamic model of CFB established previously, an equation about voidage variation was developed, from which a model equation for bed expansion was obtained. The analyses of the influence of operation conditions on the bed expansion show that for a high rotational speed and thin bed layer, the bed expands slightly, while in the condition of low rotational speed and thick bed layer, the bed expansion becomes obvious as gas velocity increases. Consideration of these expansion behaviors in design of CFB structure is important.With respect to the difference between two types of pressure drop curves and the deviation of the pressure drop model from the second pressure drop curve, a new factor, that is, the particle entrainment, was introduced based on the analysis of the effecting factors on pressure drop. By considering the drag coefficient of particle group, a model for particle entrainment was developed. Compared to the experimental data, this model explains the variation tendency shown in the second type of pressure drop curve, and points out that it is the failure to consider the particle entrainment that results in the deviation of the pressure drop model from the experiment, indicating that a better hydrodynamic model must take the particle...