Can You Predict Powder Flow Behavior By Measuring Density?

A general observation is that many powders, which exhibit only a small amount of compressibility (perhaps 10% going from a loosely consolidated state to a consolidation pressure of 10 kPa), will discharge from gravity feed hoppers with relative ease. A fair question to ask is whether the density of a powder can be used to quantify or predict flowability.

Food industry powders, like confectionery sugan are good examples of powders that have low density when loosely consolidated, but can increase their density significantly when compacted. The tapped density test is an easy way to quantify the change in density. A cylinder full of powder is Tapped Dcnslty Test "tapped" a specific number of times, say 100 or 150, and the resulting volume is compared to the original. This ratio quantifies the degree of compaction. This gives a good idea of the density behavion but unfortunately cannot predict whether the powder will flow in gravity discharge from a storage vessel.