With the technological development in biologically orientated\ud industries more and more natural products in powdered form are being\ud handled and processed.\ud Three differently comminuted liquorice rhizome products were\ud classified into 23 narrow size fractions to investigate the particle\ud and bulk characteristics of the material, and to study the influence\ud of particle shape on powder flowability.\ud The morphology of the fibrous particulate was investigated by\ud using a Quantimet 720 Image Analyser. The perimeter (P), projected\ud area (A), breadth (B), length (L), horizontal and vertical projected\ud lengths (P\ud V\ud and Pi) and the horizontal and vertical Feret diameters\ud (FV FH) were measured from which four dimensionless shape factors\ud were evaluated, [P2/47rA, PHxPV/A, L/B, FV/FH]. The surface texture of\ud the particles was measured by fractal analysis.\ud The influence of particle shape and size on the mean flow rate,\ud coefficient of flow variation and flow uniformity were measured using\ud a specially designed inclined tube flowmeter.\ud The failure properties of powdered liquorice when sheared under\ud known normal compressive stresses were measured and from a series of\ud yield loci the unconfined yield strength, major consolidation stress\ud and effective angle of internal friction were obtained. The effects\ud of particle shape and size on the angle of internal friction, wall\ud friction, bulk and packed densities were. investigated and the\ud experimental correlations expressed in terms of mathematical\ud equations. These relationships, together with the failure function\ud plots, indicate that comminuted liquorice powder behaves as a "simple"\ud powder.Darou-Pakhsh Pharmaceutical\ud Compan
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