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. Geldart's 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.

Graphical AbstractMinimum pick-up velocity (Upu) of binary particle mixtures depends on particle diameter ratio and mass fraction of constituent particles. Variations in Upu with mass fraction also depend on whether the mixture belongs to pick-up zones I, II, or III. Monodisperse Upu correlation can accurately predict Upu of zone I binary mixtures.Figure optionsDownload as PowerPoint slideResearch Highlights
► Binary mixtures exhibit distinct entrainment from their monodisperse counterparts.
► Mixtures of Geldart's group B particles are entrained non-collectively.
► Mixtures of groups A and B particles are entrained as clouds of the mixture.
► Monodisperse correlation can only predict entrainments of group B particles.
► Packing efficiency influences entrainment process.