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Sphericity of apatite particles determined by gas permeability through packed beds

Minerals & Metallurgical Processing , 2009, Vol. 26, No. 2, pp. 105-108

Souza Pinto, T.C.; Lima, O.A.; Leal Filho, L.S.


Because shape is an assessment of the three-dimensional form of a particle, it may be described in terms of sphericity (Ψ), which is a measure of how closely a particle approaches a spherical configuration. In this study, Darcy’s law and the Kozeny-Carman model for fluid flow through porous media were applied to packed beds to determine the sphericity (Ψ) of apatite particles. The beds were composed of glass spheres or particles of apatite (igneous from Brazil and sedimentary from the United States) of three classes of size (Class 1: -297 +210 µm; Class 2: -210 +149 µm; Class 3: -149 +105 µm). Glass spheres were used to validate the model because of its known sphericity (Ψ = 1.00). Apatite particles, either igneous or sedimentary, showed very close values for particle sphericity (Ψ ≈ 0.6). Observations on particle images conducted by scanning electron microscopy illustrated that igneous (Ψ = 0.623) and sedimentary (Ψ = 0.644) particles of apatite of Class 2 predominantly exhibit elongated shape. The close value of particle sphericity (Ψ ≈ 0.6) showed by either igneous or sedimentary apatite may be justified by the similarity in particle shape.