Powder material rheology under belt transportation

Particulate solids flow on plane moving media, by translation (conveyor belts, chain carriers, slopes), or vibration (conveyors) is realized by mono or multi-layer feed. When it is necessary to realize high solid flows, or, on the contrary, it is not necessary to discriminate the solids at the end of the transporting, the particles are fed in bulk, in order to realize several particulate solids layers on the conveyor belt. The distribution of particles in the different layers, and the shapes assumed by the core is influenced by: i) the feeding condition, ii) the shape of each particle, iii) the surface characteristics of the particle, iv) the feed composition (mono or multi-phase), v) the size class distribution of the feed, vi) the characteristics of the transport carrier, vii) the transport length (time). As a consequence the shape of the heap changes, evolving from the feed to the carrier up to the discharge at the destination site. It has been observed as, maintaining constant the parameters previously described at point 1, 6 and 7 (feeding conditions and carrier characteristics) and for a specific transport time, the characteristics of the heap formed by the transported particles and, more specifically its profile, projected on a plane perpendicular to the transport direction, are influenced by the size class distribution and by physical and chemical attributes of the transported particles. With reference to the heap profile, as previously described, two main characteristics have been identified: a) profile structure, that is the monotonous curve overlaying the heap outline; b) profile texture, that is the structure of the variation of the heap outline depending by the position of the single particles at the border of the heap, this last characteristics has not to be confused with c) profile “distortions”, that is the noise affecting the signal representative of the heap outline.