Solid particle

Solid particles are solid, discrete bodies that are characterized by their shape, size, density, and surface properties. They can be naturally occurring or technically produced, for example as crystals, granules, powders, or agglomerates. In bulk solids technology, many solid particles together form a particle collective that is handled as powder, granules, or pellets.

Important characteristic quantities of a solid particle include its size, shape, true density and bulk density, as well as surface roughness and surface chemistry. Particle size is often described by an equivalent diameter, for example the diameter of a sphere with the same volume as the actual particle. In practice, particle size distributions are often specified, for example as d10, d50, or d90. These indicate the diameter below which 10%, 50%, and 90% of the particles, respectively, lie.

d_(eq) = (6 · V_P)/π¹^/³

• d_(eq): equivalent spherical diameter
• V_P: particle volume

The true particle density (ρ_P) and the bulk density (ρ_(bulk)) can be defined in terms of mass and volume:

ρ_P = m_P / V_P

ρ_(bulk) = m_(bulk) / V_(bulk)

• m_P is the mass of a particle
• V_P is the volume of a particle
• m_bulk is the mass of a bulk solids sample
• V_bulk is the total volume of the bulk solids sample (including voids).

Solid particles behave differently depending on size, shape, and interactions—from the “powdery” flow of very fine particles to free-flowing granules and dimensionally stable pellets. For mixing processes, transport, storage, agglomeration, drying, or coating, understanding the particle properties is crucial. They influence flowability, tendency to segregate, dust formation, attrition, mixability, and the cleanability of equipment.

In amixon® mixers, the particles are moved gently yet effectively. This makes homogenization with minimal attrition possible. Knowledge of the particle properties is therefore an essential starting point for designing the mixer.