Granulation is the process of creating granules. The powder morphology is modified through the use of either a liquid that causes particles to bind through capillary forces or dry compaction forces.
Importance of Granulation in Pharmaceutical Industry
The granulation process will result in one or more of the following powder properties:
- Enhanced flow;
- Increased compressibility;
- Alteration of physical appearance to more spherical, uniform, or larger particles; and/or
- Enhanced hydrophilic surface properties.
Types of Granulation in Pharmaceutical Manufacturing
There are several types of granulation in pharmaceutical industry:
- Dry Granulation
- Wet High-Shear Granulation
- Wet Low-Shear Granulation
- Low-Shear Tumble Granulation
- Extrusion Granulation
- Rotary Granulation
- Fluid Bed Granulation
- Spray Dry Granulation
Operating Principles of Granulation
Dry powder densification and/or agglomeration by direct physical compaction.
Wet High-Shear Granulation
Powder densification and/or agglomeration by the incorporation of a granulation fluid into the powder with high-power per-unit mass, through rotating high-shear forces.
Wet Low-Shear Granulation
Powder densification and/or agglomeration by the incorporation of a granulation fluid into the powder with low-power per-unit mass, through rotating low-shear forces.
Low-Shear Tumble Granulation
Powder densification and/or agglomeration by the incorporation of a granulation fluid into the powder with low power-per-unit mass, through rotation of the container vessel and/or intensifier bar.
Plasticization of solids or wetted mass of solids and granulation fluid with linear shear through a sized orifice using a pressure gradient.
Spheronisation, agglomeration, and/or densification of a wetted or non-wetted powder or extruded material. This is accomplished by centrifugal or rotational forces from a central rotating disk, rotating walls, or both. The process may include the incorporation and/or drying of a granulation fluid.
Fluid Bed Granulation
Powder densification and/or agglomeration with little or no shear by direct granulation fluid atomization and impingement on solids, while suspended by a controlled gas stream, with simultaneous drying.
Spray Dry Granulation
A pumpable granulating liquid containing solids (in solution or suspension) is atomized in a drying chamber and rapidly dried by a controlled gas stream, producing a dry powder.
Granulating Equipment Classification
- Dry Granulator: Slugging; Roller Compaction.
- Wet High-Shear Granulator: Vertical (Top or Bottom Driven); Horizontal (Side Driven).
- Wet Low-Shear Granulator: Planetary; Kneading; Screw.
- Low-Shear Tumble Granulator
- Extrusion Granulator: Radial or Basket; Axial; Ram; Roller, Gear, or Pelletizer.
- Rotary Granulator: Open; Closed.
- Fluid Bed Granulator
- Spray Dry Granulator
Selection of Granulation Process
Although there may be other reasons for selecting a granulation method/process (such as economics), the manufacturing dictates can be summarized as follows:
- If a material or mixture flow is good and is compressible, one can use direct compression.
- If a material or mixture is compressible (but exhibits poor flow), one can use dry granulation.
- If a material or mixture neither flows nor is compressible, one must use wet granulation.