Granulometry

The technical term ‘granulometry’ comes from bulk solids technology and describes the properties of dispersed substances. The focus is on the flowability and description of the particle size distribution of a bulk material

The technical term ‘granulometry’, which comes from bulk solids technology, describes the properties of dispersed substances. The focus is on the analysis and description of the particle size distribution. This also includes characteristics such as particle shape, particle density and particle hardness. The moisture content of the bulk material is also of great importance – both the water content and liquid additives such as binders or solvents.

A key criterion for the process engineering design of silos and IBCs is flow behaviour. This can be determined using the Jenike shear device, which determines the so-called flow points. These provide information about whether a powder tends to compact or form bridges and how easily it can be emptied from a container.

Other important parameters are bulk density, tamped density and elasticity, which describe the volume behaviour. Fluidizability indicates whether a powder can be converted into a quasi-liquid state by adding air. This property is particularly relevant for dryers and pneumatic conveying systems. The tendency to agglomerate and pelletability are also decisive, for example in processing by die pressing or briquetting.

In addition, optical properties such as light absorption and reflection behaviour can be investigated. Chemical-physical characteristics such as hydrophobicity (water-repellent), hydrophilicity (water-attracting), hygroscopicity, porosity and specific surface area influence storage, dosing, reactivity and handling.

The interdisciplinary term ‘granulometry’ combines mechanical, physical and chemical properties to provide as complete a picture as possible of the behaviour of bulk materials. This data can often only be obtained through targeted laboratory analyses, but it is essential for the reliable design of process equipment and for the automation of modern powder factories.