Dry Granulator machine

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.

Blog Contents

1 Factors that affect the rate and size of granules produced by a dry granulators

2 Sub-classes of dry granulators

3. Slugging

4. Factors affecting slugging process 

5. Roller Compaction

6. Advantages of Roller Compactor

7. Pharmaceutical uses of Dry granulators

8. Advantages of Dry Granulators

9. Disadvantages of Dry Granulators

1. Factors that affect the rate and size of granules produced by a dry granulators

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

2. Sub-classes of dry granulators

Dry granulator sub-classes are primarily distinguished by the densification force application mechanism and they include;

1. Slugging

2. Roller compaction

3. Slugging

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.

4. Factors affecting slugging process 

Other disadvantages of slugging include;

Single batch processing

Frequent maintenance change over

Poor economic of scale

Low manufacturing throughput per hour

Excessive air and sound pollution

Increased use of storage containers

Increased need for manufacturing space.

Increased logistics

More energy and time is required to produce 1kg of slug than 1kg of roller compact.

Factors affecting slugging process 

Powder cohesiveness, density, and flow characteristics

Powder particle size distribution

Machine type

Feed hopper and feed frame

Die diameter

Compression speed

Slugging pressure

5. Roller Compaction

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.

Picture of the parts of a dry granulator

The roller compactor or chilsonator generally consists of three major units.

Feeding system: 

This unit conveys the powder to the compaction area between the rolls.

Compaction unit: 

This is where the powder is compacted between two counter-rotating rolls to a ribbon by applying a force.

Size-reduction unit: 

This is for milling the ribbons to the desired particle size.

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;

Fixed roller compactor: Roller compactor equipped with a fixed gap.

Variable gap roller compactor: A roller compactor with a floating gap.

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.

6. Advantages of Roller Compactor

Simplifies processing

Facilitates powder flow

Uses minimal energy to operate

Improves drug dosage weight control.

Requires less man-hours to operate

Reproduces consistent particle density

Produces good tablet and capsule disintegration

Eliminates aqueous and solvent granulation

Uses fewer raw materials

Eliminates water-induced degradants

Improves process circle time

Prevents particle segregation

Facilitates continuous manufacturing

Improves content uniformity

Does not require explosion-proof room or equipment

Produces a dry product that is process scalable.

Pharmaceutical uses of Dry granulators

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.

Advantages of Dry Granulators

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

7. Disadvantages of Dry Granulators

1. It does not permit uniform color distribution

2. Dry granulation process creates more dust

3. There is increased potential for cross-contamination

Thanks for reading - Dry Granulators
Naitik Patel
Industrial Guide

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