Granulator Process Overview
A spray granulator allows a liquid solution to be rapidly dried over an active ingredient. This newly encapsulated particle structure is harder and denser, yielding particle properties that are desirable in many applications. The newly formed particle can be sprayed again and again creating larger and larger spherical pellets that form in successive onion like layers.
Most spray granulators spray a liquid solution over a hot fluidized bed of active material. This process works by suspending and tumbling the particles in a high velocity gas flow while applying the coating as a fine mist. Both liquid and solid powder coatings may be applied in this type of process.
Some of the desirable product properties of granulator processing are:
- narrow grain size distribution
- dust-free granules
- spherical pellets
- free flowing properties
- good dosing properties for pharmaceuticals
- good dispersion
- good solubility
- compact structure
- less hygroscopic
- low bulk density
- less abrasive
In a spray granulator, the particles are conveyed through the inner partition into the expansion chamber by the hot fluidizing air. Gravity overcomes the force of the fluidized air and the particles fall back into the outer partition. The pneumatic atomizing nozzle in the bottom center of the chamber introduces the coating solution. This nozzle sprays upward providing successive applications of coating to the product.
