Characterisation of Powder and Bulk Material

Powder Characterisation

Characterisation of Powder and Bulk Material

A Multivariate approach using Dynamic, Shear and Bulk Property Measurements
Powders should not be thought of as having ‘good’ or ‘bad’ flow properties. The key to achieving efficient processing is to ensure that plant and processing equipment are compatible with the characteristics of the powders being used. However, such a requirement demands a thorough understanding of the nature and behaviour of the materials themselves in order to have the information to feed into process design and development from the outset. This begs the question of how best this can be achieved.
(ed. WoMaMarcel - 29/7/2013)
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It is extraordinary that while powders and bulk materials are used extensively throughout so many industries, they are so poorly understood compared to fluids and solids. Powders comprise a combination of phases which makes them difficult materials to characterise. A powder is an assembly of solid particles; the interstitial gas between the particles (usually air); and the moisture (from the atmosphere or from upstream processing) present on the surface, in particle pores or loosely bound to the molecules. The interaction of these phases contributes to the changeability of powders, and as a consequence the processing and handling of powders is certainly not straightforward or easily predictable. Adherence of cohesive materials to containing surfaces, excessive aeration of powders in pneumatic flow systems, bridging of powders in hoppers, electrostatic charging of materials during handling and consolidation during transport or storage are all familiar problems. Powders are complex and the characterisation of flow properties is an important requirement. Powders should not be thought of as having ‘good’ or ‘bad’ flow properties. A free flowing powder may present serious problems by fluidising too readily, whereas a cohesive powder may be processed consistently if the conditions are suitable. In our experience, the key to achieving efficient processing is to ensure that plant and processing equipment are compatible with the characteristics of the powders being used. However, such a requirement demands a thorough understanding of the nature and behaviour of the materials themselves in order to have the information to feed into process design and development from the outset. This begs the question of how best this can be achieved.
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