Nonisothermal Effect on the Bed Performance

In the dilute phase the contact efficiency is rather high but the rate of heat transfer is low, and hence the temperature may not remain uniform in this region. Thus, the temperature effect on conversion and selectivity becomes important when a substantial part of the entire reaction occurs in the dilute phase. This chapter discusses salient features of the temperature effect on fluid bed reactions. 

Several types of internals have been proposed so far. Some studies are presented by Volkct al. (VI2) and Grekelet al. (G15), who studied several arrangements of tubular internals and baffle trays. Volk suggested vertical tubes to increase the contact efficiency. For fluidized beds with diameter of 5-198 inches, conversions for beds of the same equivalent diameter (cf. Section I,C) were found equal. A large heat-exchange surface in the fluid bed is necessary for non-isothermal reactions, so the use of vertical tubes is quite practical. 

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. 

Heat transfer between the bed and wall is important in considering temperature rise in the dilute phase (F16). This is discussed briefly in Section VI,G. 

The effect of the dilute phase on overall conversion of the reactant is straightforward. Conversion in the bed increases if the ccmtact efficiency increases due to suspended catalyst in the dilute phase. If temperature 

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