How to Improve Flowability of Powders

Flowability refers to the ability of a powder to flow out of a bin or hopper and through chutes or pipes. This depends on several factors such as the size and shape of the powder particles. Smaller particles tend to stick together and have poor flowability. Friction between the powder particles and the hopper walls also impairs flowability. Besides, external factors such as the smoothness of the hopper surface and the angle at which the hopper is inclined play an important role in determining how well a powder flows.

Instructions

1. Convert finer particles into larger aggregates, or pieces, by the process of wet agglomeration. Add a binding agent such as starch, microcrystalline cellulose or povidone to make particles stick together to form uniform-sized, spherical granules. This granulated mix flows better than a fine, non-granulated powder.

2. Add a lubricant or glidant material such as colloidal silica or magnesium stearate to the powder. These materials reduce the friction between the powder and the walls of the hopper, leading to better flow.

3. Coat the hopper walls with anonsticking, coating material. This reduces the friction between the powder particles and the hopper walls, improving flowability.

4. Carry out test runs by setting the hopper's inclines at different angles. Study the powder flow at each angle to find out the inclination at which the powder flows best. Repeat this for every different powder blend because different powders have different flow characteristics.

5. Design a new hopper if none of these measures improve powder flowability. Make the hopper walls steep to reduce cohesion and friction. Keep the outlet hole big to allow sufficient space for the powder to flow out smoothly.

6. Reduce the time you store powders between different stages of an operation. When powder particles remain in contact for long, bonds between particles undergo changes because of chemical reactions and this alters the powder's flowability.

References

• International Journal of Pharmaceutics; Use of a Static Eliminator to Improve Powder Flow; Kalyana C. Pingali et al.; March 2009
• Jenike and Johanson Inc.; On Powder Flowability; James K. Prescott and Roger A. Barnum
• Freeman Technology: Powder Behaviour and the Nature of Powders
• American Pharmaceutical Review; Effect of Particle Size Distribution and Flow Property of Powder Blend on Tablet Weight Variation; Allan Fan et al.
• Feeco International; Consider Wet Agglomeration To Improve Powder Flow; Greg J. Mehos and Chris M. Kozicki
• PharmPro; How to Select the Right Pharmaceutical Tablet Hopper for Your Manufacturing Operation; Pete Connors