Strona 2_redak - Instytut Agrofizyki im. Bohdana Dobrzańskiego ...

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Fig. 3.17. Model of shear band
formation according to Iwashita
and Oda [72]
4. CLASSIFICATION OF GRANULAR MATERIALS
The concept of granular material covers a very broad class of materials, beginning
with farmaceuticals, cement and aspiration dust – through agricultural products, like
e.g. cereal grain – food products, like flour, sugar, powder milk – to mineral raw
materials, like e.g. gravel, stones and coal. For a variety of technological operations
highly important is the wide array of such physical properties as bulk density,
granulation, friction coefficient, hardness, moisture, explosiveness, sorptive and
thermal properties. This creates the need for a coherent classification of such
materials, to avoid the risk of errors and misunderstandings resulting from the
omission of some material characteristic important for a given process. The
properties of granular materials vary within a very broad range, depending on the
origin of a material, the processes of production and processing applied, and on
external factors and conditions. At present, two systems of classification of granular
materials are most commonly used – CEMA and ISO [71]. The CEMA classifycation
comprises bulk density, grain size, flowability, abrasiveness, and a number
of other mixed characteristics. The ISO classification [71] is rather abbreviated – it
comprises particle form, flowability, and several characteristics related to material
transport and handling.
The popular division of granular materials according to the mean grain size
D includes the following classes [169]:
dusty (e.g. aspiration dusts, fertilizer lime) D ≤ 0.05mm,
powder (e.g. flour, fine meal) 0.05 < D ≤ 0.5 mm,
granular (e.g. cereal grain) 0.5 < D ≤ 10 mm,
nodular (e.g. gravel, wood chips) 10 < D ≤ 50 mm,
lumpy (e.g. coal) 50 < D ≤ 300 mm,
massive (e.g. unsorted stones) D > 300 mm.