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Aug 1, 2012

Spray Granulation for Compact Granules from Fluids - An Application of Fluid Bed Technology or Spouted Bed Technology

Spray granulation is the drying of liquid while simultaneously building particle size. Seeds for the granulation can be charged (external seeds). Alternatively the seeds are formed within the processing chamber by abrasion (internal seeds). Compared to agglomerates these granules are harder and denser. The spray granulation process was developed in the early 1980s at what is now Glatt Ingenieurtechnik. Since that time Glatt is one of the leading vendors within this technology.

For small quantities the process can be run in batch mode.  The undersized particles of the previous batch are screened off and used as starting material. Continuous processes are more efficient since they can be run with a constant bed height in the processing chamber. According to the process the entire fluid bed is mixed and the product is discharged through a central discharge pipe (AGT-process), or a plug flow is created in the GFG – Glatt Fluid Bed Granulator. Using the GFG, drying and cooling of the granules can be accomplished in the same equipment as in the agglomeration process.
If solids are added to the spray granulation process they are integrated into the onion structured granules. Adding more and more powder shifts the spray granulation process towards agglomeration. It is also possible to form small granules from the liquid raw material which are agglomerated to larger particles in the same processing chamber. Ideal agglomerates and ideal spray granulates are the two extremes of a continuous scale. By changing the process parameters both processes occur simultaneously and form different structures. Since agglomerates have a smaller bulk density than spray granulates the bulk density of the granules is adjustable.