Different Types of Spouted Bed

Because of high turbulence in the spout and the regularity of particle mixing, different types of spouted bed are highly appropriate to the placement of spray nozzles for the purpose of particle formulation, such as granulation or coating. Two examples in which liquid spraying occurs directly at the entrance of the gas jet, and which results in a concurrent, upward flow of the droplets and gas with frequent droplet-partide collisions, are shown in Fig. 4.3. The equipment shown in Fig. 4.3a is of the conical-cylindrical type, whereas the cylindrical device of Fig. 4.3b is named Wurster equipment, after its inventor (Wurster, 1959). The main feature of... 

The results of investigations of the maximal bed pressure drop with different types of spouted bed are summarized in Tab. 4.3. Therein... 

Reynolds numbers - as defined by Eq. 4.8 - that correspond to the lower limit of the stable operating regimes of Fig. 4.13 may be denoted by Re n,sf Correlations developed for RCjn.st are summarized in Tab. 4.5. However, it should be noted that Fig. 4.13 and Tab. 4.5 provide only coarse estimates for the stable operation ranges of different types of spouted bed. The reason for this is that even small variations in the apparatus geometry - especially variations in the construction of the gas entrance - can have a significant influence on the fluid dynamics of the spouted... 

Fig. 4.13 Working diagram forthe determination ofthe stable operation regionsof different types of spouted beds according to G czka (2009). Between A and B Conventional spouted beds (Mitev, 1979) Cto D Prismatic spouted bed with two parallel gas entrances...

Binder granulation can be achieved in different types of mixers ranging from rotating drums and pans to high shear mixers and fluidized and spouted beds. During the present analysis, the accent is put on fluid... 

However, in various coating and granulation experiments a change in the shape of the distribution is observed, for example a dispersion of the distribution. In Fig. 7.45 the results of five different coating experiments are shown, which were conducted in Wurster equipment, a conventional fluidized bed apparatus (FB) in top and bottom spray configuration, and a spouted bed apparatus (SB) in top and bottom spray configuration. Although identical initial conditions were used and the process conditions are comparable (see Tab. 7.6), different final distributions are achieved. This effect cannot be explained by the common model of Eq. 7.34, but it underlines the influence that different types of equipment with different flow patterns may have on the process result. 

An alternative approach is the development of different types of cell design, particularly those utilizing three-dimensional electrodes. This strategy is an attractive one for the treatment of dilute (say <2gdm ) metal-containing liquors, where the increased mass transport and electroactive area of the three-dimensional cathodes is very important in order to sustain a reasonably high current (and, hence, production rate of metal), e.g. cells with packed, spouting or fluidized beds of carbon or metal particles have been operated on a pilot plant and full plant scale. Such cells arc described in detail in Chapters 2 and 7. 

Fig. 10.7 Types of fluidized bed reactors [43], Reprinted with permission from the authors. The primary fluidized bed reactor types 1 bubbling fluidized bed, 2 turbulent fluidized bed, 3 circulating fluidized bed, 4 riser, 5 drowner, 6 cross-current fluid bed, 7 counter-current fluid, 8 spouted fluidized bed, 9 floating fluidized bed, 10 twin fluidized bed. The key issues leading to re-design of the conventional bubbling fluid bed A higher gas velocity, B counter-current contacting is beneficial, C incompatible differences in desired environment, D dusty environment, E large paiticles/low gas load...

A number of factors influence the selection of a dryer from the many different types available. These factors are dominated by the nature of the feed, whether it be granular solids, a paste, a slab, a film, a slurry, or a liquid. Other factors include the need for agitation, the type of heat source (convection, radiation, conduction, or microwave heating), and the degree to which the material must be dried. The most commonly employed continuous dryers include tunnel, belt, band, turbo-tray, rotary, steam-tube rotary, screw-conveyor, fluidized-bed, spouted-bed, pneumatic-conveyor, spray, and drum dryers. 

Figure 3.35. Differing situations in a fluid/solid reactor as a function of the velocity of the fluid phase, along with fluidization diagrams for the various reactor types. The pressure drop, Ap, increases in solid bed operations until the minimum velocity for fluidization is reached, t f. Above this velocity, fluidized bed conditions exist. In case of particles with diameters about 0.5 cm, the spouted bed can be operated in fluidized conditions above the minimum velocity of spouting A further increase in velocity finally leads to the elutriation of the solid phase.

Several processes, both physical and chemical, are nowadays carried out in various type of fluidised and spouted bed apparatuses. The phenomena of abrasion and grindability, associated with the contact of phases are estimated in different ways, depending on the process in which they take place [6]. Usually it, is treated as a factor lowering the efficiency of the processes running in fluidised and spouted beds. 

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