Applications

(Spray) Granulation 

Spray granulation refers to the drying of fluids which results in the simultaneous formation of granulate. In fluidised beds, this process is used to obtain compact and almost circular granulate with outstanding physical properties.

Nuclei are subdivided into two groups: inherent nuclei, which form due to abrasion and fracture, and foreign nuclei, which are produced through the drying process. Compared to agglomeration, the granulate created here is harder and thicker. The continuous fluidised bed spray granulation process is suitable for all applications which require a homogeneous, dust-free granulate with a high bulk density.

Advantages

• taste masking
• aesthetic appearance
• application of functional coating such as gastro-resistant layers as well as protective layers against moisture and oxidisation.

Basic principle

The granulation nuclei are suspended by the force of the heated air flow. This separates the particles out from one another, which makes it possible to wet the entire surface area of each individual granulation nucleus with the sprayed liquid.
The fluid comes into contact with the particle surface and begins to evaporate. As this happens, a solid layer begins to cover the granulation nucleus, forming a solid coating. The addition and solidification of further droplets adds layers to the granulate like an onion.

Parameters such as high solid content, grain size and residual moisture can be very precisely regulated inside the fluidised bed during spray granulation, which means a wide variety of materials can be processed to granulate. As the granulate is simultaneously dried and shaped, the process is also referred to as continuous fluidised bed spray granulation. The top or bottom spray method (i.e. with or without a Wurster draft tube) can be used in spray granulation.