Spouted beds pressure drop across

The mechanism by which a bed of particulate solids transforms to the spouted state is best explained by following the changes that occur in the pressure drop across the bed, with varying rate of gas flow (Fig. 4). 

With further increases in gas flow, the cavity elongates to an internal spout (Fig. ob). The arch of compacted material stUl exists above the internal spout, so that the pressure drop across the bed rises further until it reaches a maximum value (Fig. 4, point B). 

This explanation for the existence of a peak pressure drop is supported by experimental results obtained by Manurung (M7), who measured pressure drops separately across the upper cylindrical part and the lower conical part of the bed contained in a conical-cylindrical column as a function of both increasing and decreasing air flow. It is seen in Fig. 9 that the pressure drop across the upper part of the bed, up to the point at which the spout breaks through, corresponds to that in a packed bed and remains the same irrespective of whether the flow is increasing or decreasing. A peak well before the onset of spouting occurs only in the curve for the lower... 

In the spouted state, the pressure drop across the bed arises out of two parallel resistances, namely that of the spout, in which dilute phase transport of particles is occurring, and that of the annulus, which is a downward-... 

Figure 51.15 presents the relationship between Re and the Reynolds number for the settling velocity of grain R yas well as various operating zones of spouted beds. To estimate the pressure drop across a spouted bed, one can use the approximate formula ... 

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