Wurster Insert

Initial process development and ultimate process optimization were conducted as described by Vesey and Porter (14). Basically, the study was performed in a Glatt GPCG-3 unit fitted with a Wurster insert. The process variables that were evaluated are as shown in Table 13. 

In contrast to the coating pans, small particles such as beads, pellets, granules, and powders are generally coated using the fluidized bed or air suspension method, which utilizes a carrier gas to keep the cores in motion. The high air current makes this technique more efficient at water removal. The bottom spray technique is one of the most common fluidized bed application methods and a schematic of this process is shown in Fig. 4A. A perforated distribution base plate allows sufficient air into the product container to force the particles up into a cylindrical or slightly conical coating chamber, known as a Wurster insert. These inserts have been recently improved to keep... 

Spraying. The coating or aggregative solution can be sprayed from the top (top spray, Figure 8a) or bottom (bottom spray or Wurster when a tube is inserted in the reactor, Figure 8b) or in the particle bed itself. 

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...

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