Influence of extreme particle shape on powder flow properties and using a rising column test to identify nesting tendency

Reliable bulk solids flowability is essential for operation of any industrial material handling systems. For materials with extreme particle shapes e.g. highly elongated, fibrous, or plate-like particles such as in biomass and biowaste fuels, it often exhibits flow resistance governed by particle nesting and mechanical interlocking rather than cohesive strength. This effect frequently leads to operational issues in industry including storage blockages, and unreliable feeding or discharge. Conventional characterisations of powder flow properties have limitations to capture the nesting behaviour of the bulk solids directly. To address this limitation, a novel experimental method based on a rising column test is used to identify nesting tendency of the materials with extreme particle shapes. Five processed biomass materials with distinctly different particle morphologies were investigated using both conventional shear cell testing and the rising column method. The study examines the influence of extreme particle shape on bulk flow behaviour and evaluates the capability of the rising column test to capture interparticle nesting effects. The results demonstrate that particle shape has a dominant influence on flow behaviour when the particles fall in an extreme range of particle shapes. It shows that particle nesting significantly increases internal resistance and alters bulk stability, which are not reliably characterised clearly by the shear cell measurements. The findings offer a simple and robust approach for assessing nesting risks in materials with extreme particle shapes, providing a valuable tool for design and optimisation of bulk handling systems especially in biomass, bioenergy, and waste processing industries.