Dry granulators are machines used for dry granulation. Dry granulation is a type of granulation process in which granules are formed without using liquid solution. Formation of dry granules requires dry powder densification and for agglomeration.
1. Roller speed
2. Feed rate
3. Roll design
4. Difference in shape and size of screws
5. Powder cohesiveness, density and flow characteristics
6. Particles size
7. Machine type
8. Die diameter
9. Feed hopper and feed frame
10. Tooling features
11. Compression speed.
12. Slugging pressure
Dry granulator sub-classes are primarily distinguished by the densification force application mechanism and they include;
2. Roller compaction
In slugging, a large tablet (slug) is produced in a heavy-duty tableting press. This mechanism of dry granulation leads to variation in the weight of one slug to another. This variation is as a result of the poor flow rate of powders with small particle size which in turn causes large fluctuation in the forces applied onto the individual slugs which bring about differences of the slug’s mechanical strength. The mechanism of dry granulation is hardly used because the properties of the granules obtained by milling of the slugs cannot be controlled well either.
Other disadvantages of slugging include;
Roller compactors commonly referred to as chilsonator is a dry granulating equipment that produces a sheet of powder material by squeezing powder between two rollers. The roller compactor consists of two driver rollers running in opposite directions from the inside to the outside. The rollers are made of stainless steel and are equipped with teeth to produce a powerful grinding action by forcing the material against a series of breaking combs.
The roller compactor or chilsonator generally consists of three major units.
Fines produced during granulation are very low (max 25%) and can be reduced to 15% by careful adjustment of the process.
Roller compactors can be classified into;
Classifications still possess the three major units of a roller compactor. But they differ in the way in which the gap between the rolls is realized.
1. Dry granulators are used when the drug does not compress well after wet granulation.
2. Dry granulator is the best choice for moisture sensitive drugs like Aspirin, vitamins.
3. It is used in granulating thermolabile drugs.
1. It requires minimal floor space
2. The machine is easy to clean after use
3. The roller compactor is suitable for hard continuous operation as well as batch production
4. Dry granulators eliminate the addition of moisture and heat
5. Mechanical strength of the product is uniform
6. Low running cost/low operating cost and highly efficient process
7. It eliminates the need for binding solution
1. It does not permit uniform color distribution
2. Dry granulation process creates more dust
3. There is increased potential for cross-contamination