The morphological, flow and failure characteristics of fractionated natural bulk material. Evaluation of flowability of fractionated powdered liquorice using a specially designed flowmeter. The particle morphology was assessed by computer image analysis and the failure properties by shear cell testing.

摘要

With the technological development in biologically orientatedudindustries more and more natural products in powdered form are beingudhandled and processed.udThree differently comminuted liquorice rhizome products wereudclassified into 23 narrow size fractions to investigate the particleudand bulk characteristics of the material, and to study the influenceudof particle shape on powder flowability.udThe morphology of the fibrous particulate was investigated byudusing a Quantimet 720 Image Analyser. The perimeter (P), projectedudarea (A), breadth (B), length (L), horizontal and vertical projectedudlengths (PudVudand Pi) and the horizontal and vertical Feret diametersud(FV FH) were measured from which four dimensionless shape factorsudwere evaluated, [P2/47rA, PHxPV/A, L/B, FV/FH]. The surface texture ofudthe particles was measured by fractal analysis.udThe influence of particle shape and size on the mean flow rate,udcoefficient of flow variation and flow uniformity were measured usinguda specially designed inclined tube flowmeter.udThe failure properties of powdered liquorice when sheared underudknown normal compressive stresses were measured and from a series ofudyield loci the unconfined yield strength, major consolidation stressudand effective angle of internal friction were obtained. The effectsudof particle shape and size on the angle of internal friction, walludfriction, bulk and packed densities were. investigated and theudexperimental correlations expressed in terms of mathematicaludequations. These relationships, together with the failure functionudplots, indicate that comminuted liquorice powder behaves as a "simple"udpowder.