Tangential-spray coating

Tangential Spray Coating Appl ications/Character is tics... 

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. 

The latest developed configuration in fluidised bed coating is the tangential-spray or rotary-spray set-up, depicted in Figure 16.6. Unlike the two previous configurations, the product container and expansion chamber are cylindrically shaped and the air distribution plate is replaced with a rotating disk with adjustable height. 

Fig. 4 Schematic of a fluidized bed coating apparatus (A) bottom spray with Wurster column insert (B) top spray technique (C) tangential spray technique. (From Ref...

With regard to coating processes, various fluidized-bed techniques and their modifications were evaluated for hot-melt coating.f ° The fluidized-bed techniques include the top, bottom, and the tangential spray or rotary fluidized-bed modes. The particles to be coated are suspended in a heated high-velocity air stream, and the molten wax is applied in the form of atomized liquid droplets. 

Substrates with poor fluidization characteristics such as larger particles and/or particles of higher density are difficult to coat with the top spray mode, and the bottom spray mode should be preferred. With the tangential spray process, the product temperatures have to be maintained lower than with the top spray technique in order to avoid adherence of the coated particles to the product container. The tangential spray... 

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... 

A tangential spray configuration is illustrated in Figure 7.7. The base of the coating chamber is a solid rotating plate. This plate may have various surface topographies to promote desired product characteristics. Process air enters the chamber at the periphery of the rotating plate. Plate rotation forces particles outward to the periphery where they encounter the process air and are lifted upward and inward. The air velocity at the entrance to the product chamber is controlled by... 

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. 

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). 

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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