Coating of Particles and Particulates

Coating or encapsulation of particles, granules, or particulates can be carried out by a number of unit operations. Some of the operations used for mixing or dry powders can be equally applied for coating. Equipment that can be used for the purpose of mixing powders/coating particulates includes 

Diagram of the bottom-spray (Wurster) fluidized-bed coater. 

Coating thickness is sometimes difficult to measure conveniently due to the fine size of some powders and to the unevenness of the surface of some granular materials. A reasonably estimate of the coating thickness for spherical microcapsules can be calculated using the following expression (Dewettinck, 1977)  

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