Fluid tangential spray

As with pan coating, the key to successfully scaling up the fluid bed process involves the design of a completely optimized laboratory-scale process on which key decisions can be based. As discussed earlier, Turkoglu and Sakr [8] have provided an appropriately relevant example of how such an optimized fluid bed process (in this case, a tangential-spray process) may be designed. 

Figure 372. Schematic representations of the product handling sections of three fluidized bed coaters. (a) Top spray, (b) tangential spray (rotary fluid bed coater), (c) bottom spray (Wurster coating system)...

Wurster (bottom spray) fluid bed coating Spouted bed coating Top spray granulation Tangential spray (rotary) granulation... 

Top spray. In the top spray system, the coating material is sprayed downward on to the fluid bed such that as the solid or porous particles move to the coating region, they become encapsulated. Top spray fluid-bed coaters produce higher yields of encapsulated particles than either bottom or tangential sprays. 

FIGURE 47.8 Schematics of a fluid-bed coaler (a) top spray, (b) bottom spray, and (c) tangential spray. 

With the high demand for encapsulated materials in the global market, fluid-bed coaters have become more popular. They are used for encapsulating solid or porous particles with optimal heat exchange [105]. The Hquid coating is sprayed onto the particles and the rapid evaporation helps in the formation of an outer layer on the particles. The thickness and formulations of the coating can be obtained as desired. Different types of fluid-bed coaters include top spray, bottom spray, and tangential spray (Fig. 1.16). 

The conditions necessary for equality of particle size distribution were determined under ambient conditions. The nozzles used in the investigation can be classified as swirl-spray pressure nozzles. They accommodate a swirl insert which imparts a tangential velocity to the exiting fluid and results in a conical spray pattern. These nozzles were sufficiently different from conventional swirl nozzles (see Putnam et al., Ref. 6) to require an experimental study of particle size distribution. 

Typical fluid bed processors are illustrated in Fig. 1. Fig. lA is a simple fluid bed, usually with a conical shape at the bottom of the chamber, leading to inducing spouted particle flow more or less depending on the angle of the conical chamber. The spray is supplied from the top toward the fluidized bed in agglomeration and into the bed in a tangential direction in coating. Elutriated particles from the fluid bed are... 

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