Dry Granulation Process

The dry granulation process is used to form granules without using a liquid solution because the product to be granulated may be sensitive to moisture and heat. Forming granules without moisture requires compacting and densifying the powders. Dry granulation can be conducted on a tablet press using slugging tooling or on a roller compactor commonly referred to as a When a tablet press is used for dry granulation, the powders may not possess enough natural flow to feed the product uniformly into the die cavity.

The dry granulation process is used to form granules without using a liquid solution because the product to be granulated may be sensitive to moisture and heat. Forming granules without moisture requires compacting and densifying the powders.

Slugging operation

Sluggers 

The dry powders can be compressed using a conventional tablet machine or, more usually, a large heavy-duty rotary press can be used. This process is often known as ‘slugging’, the compact made in the process (typically 25 mm diameter by about 10–15 mm thick) being termed a ‘slug’. A hammer mill is suitable for breaking the compacts.

Roller compactors

Roller compaction is an alternative gentler method, the powder mix being squeezed between two rollers to form a compressed sheet. The sheet normally is weak and brittle and breaks immediately into flakes. These flakes need gentler treatment to break them into granules. This can further be milled into desired particle size.

To determine Endpoint of granulation

Granulation is rather Art than science. There are following ways to determine the granulation end point. 

To make a ball of granules in the fist by applying little pressure. The resultant ball should not be too hard or soft. It should break after applying little pressure. The remains after breaking off the ball should be granules and not fines.

To measure the amperage.

To measure the torque.

Problems in Granulation

Under granulated batch: This batch will have more percentage of fines. This will result in flow problem.

This batch may have capping, chipping, ejection and hardness problem.

Over Granulated batch may have an uneven distribution of fines, hardness and compressibility problem.

This batch may have uneven color distribution, DT and dissolution problem.