Compression

During compaction, the volume of a material is reduced and its density is increased. For bulk materials, compaction occurs through mechanical pressure, vibration, or its own weight. This reduces the voids between the particles. The bulk density increases and the porosity decreases.

Compaction influences the flow behavior, storage stability, and discharge properties. Highly compacted powders can exhibit bridging or clumping. In contrast, slightly compacted bulk materials remain free-flowing. In silos, mixers, and conveying systems, compaction behavior is therefore an important design parameter.

Compaction can be described via the change in density:

ρ = m / V

• ρ is the density of the bulk material (kg/m³)
• m is the mass of the material (kg)
• V is the volume (m³)

With increasing compaction, the volume decreases for the same mass. The density increases accordingly.

In process engineering, compaction is used intentionally, for example during pressing, pan grinding, granulation, or tableting. In other cases, however, compaction must be avoided to maintain flowability, granulometry, and dosing capability.