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Dry granulation is a binder-free, solvent-free granulation method. No water, no binder and no drying process required
The process: Homogenized powder enters the hopper, conveyed by screw feeder to twin counter-rotating rollers. Powders are compacted into solid ribbons, then milled and sieved into target granules.
It is the ideal process for moisture-sensitive and heat-labile APIs, as it avoids degradation caused by liquid addition and drying in wet granulation.
Note: Dry granulation has prerequisites. Good powder flowability, compactability and proper moisture control are essential for stable production.
Key Parameters
- Roller Pressure: The most critical factor. 20–70 bar is the common working range. Too low pressure creates loose ribbons and excessive fines; too high pressure results in over-hard granules that hurt downstream tableting.
- Roller Speed: Determines compaction residence time. Faster speed improves throughput yet reduces ribbon density.
-Roller Gap: Controls ribbon thickness, normally 0.5–2 mm. It works together with feeding speed under closed-loop control for consistent ribbon quality.
- Volumetric Compression Ratio: Recommended 0.91–1.31, to match feed rate and roller conveying speed.
Common Production Issues
1 Roller Sticking
Main triggers: excessive moisture (>3%), over-high pressure or poor roller surface finish. Keep moisture below 2%, reduce pressure and cool rollers properly. Magnesium stearate can be added as an anti-sticking agent.
2. Excessive Fines & Low Yield
Usually from insufficient roller pressure or over-aggressive milling. Adjust pressure, feeding speed, milling speed and sieve mesh together.
3. Over-hard Granules
Caused by over compaction or too-low powder moisture. Hard granules lead to high tablet press load, die wear and unstable capsule filling weight. Moisture control needs trial confirmation.
Our Dry Granulator
Our GMP-compliant dry granulators support lab, pilot and mass production scale-up. With water-cooled rollers and closed-loop parameter control, they suit APIs, herbal extracts and nutraceutical powders.
We can integrate the machine with tablet presses, capsule fillers and packaging lines.
Contact our engineers for material testing and machine consultation.
