Pros and cons

Advantage of Freeze Granulation compared with Spray Drying

  • The granule density can be controlled (solid content of the slip)
  • No cavities (voids) in the granules
  • No migration of small particles and/or binder gives a high degree of granule homogeneity
  • Nanopowders can be granulated and dried into a powder and then re-dispersed to nanopowders again avoiding agglomeration (aggregates) of nanoparticles, which is not possible with other granulation methods like spray drying
  • Low temperature granulation and drying of pharmaceuticals, drugs, biomaterials and fine chemicals
  • A mild drying procedure minimises oxidation of non-oxides and metals
  • Lower granule density and evenly distributed pressing aids gives softer granules and ensure that all granules are broken during compaction
  • Low waste of material (high yield)
  • Not only large quantities but also very small experimental batches 50–100 ml slip) can easily be processed
  • The equipment is easy to clean (allows the use of latex as binder)
  • Possibility of recycling organic solvents

Disadvantages of Freeze Granulation compared with Spray Drying

  • Two process steps: spray freezing and freeze drying
  • Limitation in the choice of solvent, based on the freezing properties – a freezing point between –20 and +10 °C is recommended (water and cyclohexane)
  • Lower tap density of the granules requires a larger fill volume (higher pressing die)
  • Large-scale equipment with a capacity beyond 100 kg granules per day needs to be further developed

pros and cons with freeze granulation