Effects of binary particle size distribution on minimum pick-up velocity in pneumatic conveying

Minimum pick-up velocities (Upu) for entrainments of particle mixtures having binary particle size distributions (PSD) are measured in a horizontal pneumatic-conveying line using the weight-loss method. Geldartʹs groups A, B, and C glass beads having diameters of 400, 170, 40, and 5 μm are used. Variations in Upu as a function of particle mass fraction (m) are examined. The capability of empirical correlations of monodisperse Upu in predicting Upu of binary mixtures is investigated. For group B particle mixtures (i.e. 400 & 170 μm), the particles are entrained separately resulting in linear Upu variations with m, which is accurately predicted by the monodisperse Upu correlation. For mixtures involving group A and B particles (i.e. 170 & 40, 400 & 40 μm), the two particles are collectively entrained resulting in Upu that vary non-linearly with m and that cannot be predicted by the correlation. For mixtures involving group B and C particles (i.e. 400 & 5, 170 & 5 μm), Upu are comparable to that of the monodisperse group B particles, therefore they are accurately predicted by the correlation. The significant impacts of binary PSD on Upu found presently indicates that PSD effects on particle entrainment process warrants further investigations.