Three-phase fluidized beds characterization

Little is known about the fluid wall heat transfer in the case of gas -liquid flow in a fixed-bed reactor. Some research on this subject, however, has been carried out for the specific case of cocurrent downflow over a fixed-bed reactor. This is summarized in Chap. 6. Some work on the slurry-wall heat-transfer rate for a three-phase fluidized bed has also been reported. The heat-transfer rate is characterized by the convective heat-transfer coefficient between the slurry and the reactor wall. Some correlations for the heat-transfer coefficient in a three-phase slurry reactor are discussed in Chap. 9. 

Reese J, Fan LS. Particle image velocimetry application for the characterization of the flow structure in three phase fluidized beds. In Chaouki J, Larachi F, Dudukovic M, eds. Non-Invasive Monitoring of Multiphase Flows. New York Elsevier Science, 1997. 

Flow behavior of cocurrent upward gas-liquid flow to a bed of particles is characterized by a complex interaction among gas, liquid, and solid phases. A typical flow regime map for three-phase fluidized beds is shown in Fig. 12 (Zhang et al., 1997). Seven different flow regimes are identified in this map, which vary with gas and liquid velocities. The regime map is operating... 

Chen RC, Fan L-S (1992) Particle image velocimetry for characterizing the flow structure in three-dimensional gas-liquid-solid fluidized beds. Chem Eng Sci 47(13/14) 3615-3622 Chen RC, Reese J, Fan L-S (1994) Flow structure of a three-dimensional bubble column and three-phase fluidized bed. AIChE J 40(7) 1093-1104... 

In the preceding chapters we first considered the primary forces acting on a fluidized particle in a bed in equilibrium, and then the elastic forces between particles that come into play under non-equilibrium conditions. These two effects provide closure for the particle bed model, formulated in terms of the particle-and fluid-phase conservation equations for mass and momentum. Up to now, applications have focused on the stability of the state of homogeneous particle suspension, in particular for gas-fluidized systems for which the condition that particle density is much greater than fluid density enables the particle-phase equations to be decoupled and treated independently. The analysis has involved solely the linearized forms of these equations, and has led to a stability criterion that broadly characterizes fluidized systems according to three manifestations of the fluidized state always stable - the usual case for liquids always unstable - the usual case for gases and transitional behaviour - involving a switch, at a critical fluid flux, from the stable to the unstable condition. This characterization has... 

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