Conventional Models for Bubbling Bed Reactors

These developments led to a novel type of reactor models, the hydrodynamic models, in which the bed behavior was based on the characteristics of the rising bubbles. Several models of this kind were derived for the industrial relevant fine particle suspensions in which the rising bubbles are surrounded by very thin clouds of circulating gas. Various combinations of assumptions have been used to represent the phase interaction phenomena in this region [81]  

A few of the early bubbling bed modeling approaches are assessed in the subsequent sub-sections. Reliable engineering models, at this simple level of complexity, can only be derived based on appropriate empirical information characterizing the important bed properties. The theory and typical param-eterizations used to determine the relevant behavior of the gas and solids in the bubble, cloud, emulsion and wake regions are outlined. 

Increasing the gas flow just passing the point of minimum fluidization conditions the onset of particle fluidization will occur when the drag forces acting on the particles due to the upward moving gas are balanced by the weight of the solid particles [30]. 

The cross sectional average global pressure drop over a fluidized bed op -erated at minimum fluidization conditions is normally calculated by an extrapolation of the Ergun [42] equation (6.13) for fixed packed beds, the flow regime that is prevailing until the minimum fluidization flow rate has been reached, as described in chap 6  

The superficial gas velocity at minimum fluidization conditions is then found by combining the two relations for the pressure drop  

The weight of the cross sectional averaged bed at minimum fluidization is  

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