Wurster coating

Fig. 8. Schematic diagram of a Wurster coating chamber. Courtesy of the Coating Place.

Bottom Spray (Wurster) Coating Applications/Characteristics... 

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)...

Fig. 5.13 Sketch of the material processing section of a bottom spray fluidized bed coater (Wurster coating system) [B.71]...

Fig. 6.2-86 SEM photographs of particles that were coated with fluidized bed coaters a) coated with ethylcellulose in a top-spray fluid-bed processor, b) coated with ethylcellulose in a Wurster apparatus, c) vacuum top-spray coated (retard) pellet, cut open, d) Wurster coated (retard) pellet, cut open (courtesy Glatt, Binzen, Germany)...

Fluid bed coating One version of this coating is known as Wurster coating and was developed in the 1950s and 1960s. The Wurster coater relies upon a bottom-positioned nozzle spraying the wall material up into a fluidized bed of core particles. Another version sprays the wall material down into the core particles. 

Properly balanced fluidization is critical to successful Wurster coating. This fluidization includes critical aspects of the down-bed, up-bed, and expansion chamber regions. The dynamics of airflow and particle flow are complex and have been the subject of several studies. The critical elements include the following three points ... 

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