Distributor region

Grekel et al. also discussed the effect of the region of vicinity of the distributor. This region is important, since there is some catalyst directly contacting the entering gas phase (cf. Section VIII). Designs for the distributor region are proposed in many patents. However, the effect of the distributor disappears within a few decimeters because of the violent turbulence within the dense phase. 

The foregoing observations can be interpreted in terms of the bubble behavior in fluidized beds. Werther and Molerus (1973) reported that very close to the distributor region, intensified bubble activity exists in an annular region near the wall. As bubbles detach and rise, they tend to move toward the center. If the bed is sufficiently deep, they will eventually merge at the center. Because the solids are carried upward in the wake of the bubbles, they basically move along the bubble tracks. Therefore, the solids would... 

The simplest gas distributor is a perforated pipe. Since the pipe creates a significant amount of flow irregularity in the distributor region, the packed material is usually placed a distance away from the gas inlet to ensure the gas flow becomes more uniformly distributed upon entering the packed region. The separation distance is... 

Both the distributor region (commonly called the grid zone ) and the freeboard region above the dense bed can also play major roles in determining overall reactor performance. These regions have been subjected to separate reactor models (as reviewed by Ho [45]). 

As indicated in Table 11, models that use a core annulus structure in combination with axial variation in hydrodynamic properties differ widely in then-assumptions. Some (e.g., Marmo et al., 1996) impose a separate region at the bottom to account for turbulent or bubbling fluidization in the bottom zone. Others insert one or more additional zones, e.g., to account for smoother transitions from the distributor region to a core-annular structure, or to account for exit effects. Some of the models from the literature featuring multiple zones are shown schematically in Fig. 35. 

Asif M, Kalogerakis N, Behie LA. Hydrodynamics of liquid fluidized beds including the distributor region. Chem Eng Sci 47 4155 166, 1992. 

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