Spouted beds solids flow pattern

The solids movement in a spouted bed is initiated by the interaction between the particles and the high-velocity gas jet, so that particle flow in the spout region shapes the entire solids-flow pattern. While a mutual dependence between the solids flow in the spout and in the annulus is inherent to a spouted bed, it is nevertheless convenient to discuss the flow in the spout and in the annulus separately. 

Fig. 17. Solids flow pattern in the annulus (Thorley et at, Tl). Column diameter, 24 in. air-inlet diameter, 4 in. cone angle, 60° bed depth expanded, 48 in. air flow, 210 cfm minimum spouting condition f vertical component of particle velocity (in./sec) horizontal component of particle velocity (in./sec) data in ovals give solids flow (Ib/sec) based on resultant particle velocity data in rectangles give solids flow (Ib/sec) based on particle velocity at column wall.

The speed with which intermixing of solids occurs in a spouted bed is obviously dependent on the solids flow pattern, but since intermixing is a bulk property of the bed, it is difficult to relate it quantitatively to the... 

He YL, Qin SZ, Lim CJ, Grace JR. Particle velocity profiles and solid flow patterns in spouted beds. Can J Chem Eng... 

The distribution of gas between spout and annulus is important in assessing the effectiveness of gas-solids contact. Qualitatively the flo v pattern in a spouted bed is obvious the gas jet flares out as it travels upward, causing the gas flow rate in the spout to decrease, and the flow rate in the annulus to increase, with increasing distance from the inlet orifice. Attempts to quantify this pattern and to relate it to the variables of the system have been made, both theoretically and experimentally. 

The spouted bed technique has become established as an alternative to fluidization for handling particulate solids that are too coarse and uniform in size for good fluidization. Although the areas of application of spouted beds overlap with those of fluidized beds, the flow mechanisms in the two processes are very different. Agitation of particles in a spouted bed is caused by a steady axial jet and, as compared with the more random and complex bubble-induced particle flow patterns in most fluidized beds, is regular as well as cyclic. 

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