Spouted bed technique

Employing wood chips, Cowan s drying studies indicated that the volumetric heat-transfer coefficient obtainable in a spouted bed is at least twice that in a direct-heat rotaiy diyer. By using 20- to 30-mesh Ottawa sand, fluidized and spouted beds were compared. The volumetric coefficients in the fluid bed were 4 times those obtained in a spouted bed. Mathur dried wheat continuously in a 12-in-diameter spouted bed, followed by a 9-in-diameter spouted-bed cooler. A diy-ing rate of roughly 100 Ib/h of water was obtained by using 450 K inlet air. Six hundred pounds per hour of wheat was reduced from 16 to 26 percent to 4 percent moisture. Evaporation occurred also in the cooler by using sensible heat present in the wheat. The maximum diy-ing-bed temperature was 118°F, and the overall thermal efficiency of the system was roughly 65 percent. Some aspec ts of the spouted-bed technique are covered by patent (U.S. Patent 2,786,280). 

Spouted Beds The spouted-bed technique was developed primarily for solids which are too coarse to be handled in fluidized beds. Although their applications overlap, the methods of gas-solids mixing... 

Manurung, F., Studies in the spouted bed technique with particular reference to its application to low temperature coal carbonization. Ph.D. Thesis, University of New South Wales, Australia, 1964. 

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. 

The fust documented development of fertilizer granulation in suspended solids agglomerators was in the early 1960s using the spouted bed technique, and in 1970 Fisons Fertilizer Ltd, UK, introduced prilling , the granulation of fertilizers from a melt by solidification of droplets in a vertical cooling chamber. 

D.V. Vukovich, F.K. Zdanski, and H. Littman, Present status of the theory and application of spouted bed technique. International Congress on Chemical Engineering (CHISA), Prague, Czech Republic (1975). 

The geometric factors and the design requirements for stability have been delimited and the operational conditions of the jet spouted bed have been compared with those of the other gas-solid contact techniques [2,3]. 

Figure 2 shows examples of how the data from PEPT can be treated, in this case from a spouted bed. The simplest data output is a continuous trajectory, consisting of a large file of x, y, z, time values, plus optional continuously recorded user-defined parameters such as speed or blade position. Velocity values can be obtained from this data file, in practice by a multi-point weighted averaging technique, and time averaged velocity profiles can then be derived. It is also possible to obtain values of... 

Spouted-bed circulation rates obtained by Chatterjee are considerably higher than those reported for fluidized beds using a similar technique (Fig. 22). This comparison supports Chatterjee s view that spouting is a suitable operation for solids-blending processes. 

At the same time, the more traditional tabletting techniques in the pharmaceutical industry were improved and modernized which led to higher production capacities, better tablet qualities, as well as more variability in product shape and composition. Other agglomeration methods were also introduced such as fluidized and spouted beds, mixers of various kinds, etc. 

Drying of liquid and pasty materials on the surface of heated inert particles is one of the newer drying techniques. The inert material serves not only as a carrier for the liquid film but also as a heat transfer medium. The size of the inert particles may be from 20 to 40 times larger than that of the dispersed material dried, which allows for higher gas velocity and thus increased dryer productivity. Moreover, intensive motion of the inert particles (e.g., in fluid or spouted beds) results in good dispersion of the liquid feed, so coarse spray nozzles can be used. As compared to the standard spray dryer, the use of a fluid bed of inert particles to dry slurries results in 15- to 17-fold higher volumetric ev oration rates under identical thermal conditions. Table... 

Microwave drying was combined with spouted bed fluidization technique (MWSB) for the drying of frozen blueberries [42]. MWSB drying was characterized by a substantial reduction in drying time and an improved product quality compared to freeze-, tray-, and SB-dried samples. 

Jumah RY, Mujumdar AS, Raghavan GSV. A mathematical model for constant and intermittent batch drying of grains in a novel rotating jet spouted bed. In Turner I, Mujumdar AS, eds. Mathematical Modeling and Numerical Techniques in Drying Technology. New York Marcel Dekker, 1997, pp 337-380. 

Simons SJR, Seville JPK, Clift R, Gilboy WB, Hosseini-Ashrafi ME. Application of gamma-ray tomography to gas fluidized and spouted beds. In Beck MS, Campogrande E, Morris M, Williams M, Waterfall RC, eds. Tomographic Techniques for Process Design and Operation. Southampton Computational Mechanics Publications, 1993, pp. 227-238. 

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