Bulk Density
Bulk density describes the ratio between a bulk material's mass and the volume it occupies in the poured (or freely settled) state.
What determines bulk density?
The voids between individual particles are taken into account. Bulk density is usually given in kilograms per cubic meter (kg/m³) or grams per liter (g/l).
It is an important property of bulk materials like powders, granules, or pellets, and plays a significant role in the design of feeding and conveying processes. Unlike a material's particle density, bulk density is not a constant quantity. It can change depending on compaction, vibrations, or changes in humidity, among other factors.
What is the significance of bulk density for feeding?
Bulk density determines the mass of a bulk material that is dispensed for a given volume. This is particularly relevant in volumetric feeding: In this process, a defined amount of material is dispensed based on its volume. If the bulk density changes, the fed mass may also change even though the fed volume remains constant.
In gravimetric feeding, on the other hand, the discharged mass is measured and the feeding rate adjusted accordingly. This makes it possible to account for fluctuations in bulk density and achieve a high degree of feeding accuracy.
Why is bulk density important for equipment design?
Bulk density is an important parameter for selecting and sizing feeding equipment. In combination with the required feed rate, it influences the hopper's size and the feeder's design.
Also, bulk density is related to other material properties like particle size, particle shape, and flowability. To ensure reliable feeding processes, none of these characteristics should be considered in isolation.