4. Segregation

Segregation is one of the main problems associated with heterogeneous populations of particles with different sizes, shapes, densities or surface properties. Segregation can occur during silo filling and unloading. For example, when a mixture of particles is discharged into a silo, the largest (or densest) particles with the greatest inertia tend to flow down the slope of the embankment formed. Conversely, fine particles are more easily stopped by the heap and are located in the center of the silo. This spontaneous segregation leads to a distribution, in the form of strata, of the two populations of fine and coarse particles known as Christmas trees.