Rheology of cohesive powders in a pilot scale planetary blender

Léonard Legoix (1) , Cendrine Gatumel (1) , Mathieu Milhé (1) , Henri Berthiaux (1)

1 RAPSODEE - Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement

Powder agitation experiments in a bladed planetary mixer have been performed with the objective of establishing correlations based on dimensionless numbers. Powders of different kind have been studied: free flowing (semolina) and cohesive (lactose, talc and milled sand). Mixtures of free flowing and cohesive powders have also, been studied to get a more complete range of powders of different properties. It has been observed that the gyration motion plays an important role in the power consumption of cohesive powders. The relation between a modified power number(N-pM=P/rho(b)u(ch)(3)d(s)(2)) and a modified Froude number (Fr-M = u(ch)(2)/gd(s)) used in several previous publications is adapted and shown to depend on powder cohesion. These dimensionless numbers are built on the basis of a characteristic speed an, a characteristic length d(s), the bulk density rho(b) and the power consumption A. The filling ratio f is also taken in account. For a free flowing powder, of cohesion smaller than 0.3 kPa, N-pM= a(f)center dot F-rM(-1) while for a more cohesive powder, of cohesion higher than 0.6 kPa the correlation N-pM= 6 center dot F-rM(b(f)) is more appropriate. For both equations, a and b are powder-dependent parameters. Their linear dependency on the filling ratio of the blender has been established.

Mots clés: Froude number; Powder mixing; Rheology of mixtures; Power number

Domaines: Sciences de l'ingénieur [physics]

Léonard Legoix, Cendrine Gatumel, Mathieu Milhé, Henri Berthiaux. Rheology of cohesive powders in a pilot scale planetary blender. Powder Technology, 2017, 305, p. 609-619. ⟨10.1016/j.powtec.2016.09.021⟩. ⟨hal-01619258⟩