Handling and transportation properties of rapeseed biomass as affected by particle size

Rapeseed by-products of seeds de-oiling, particularly expellers and post-extracted meal, are currently considered an important biomass that can be used as an alternative energy source, either in raw form or after conversion to biochar. Rapeseed biomass represents a difficult-to-handle cargo, mainly due to its sensitivity to mechanical, climatic, and biological impacts, as well as its dusty nature. This study aims to determine the physical properties of rapeseed meals and their fractions. Morphological and chemical features of six particle sets are investigated in order to explain the variation in their physical properties having importance in handling and transportation processes. The true density of fractions increases when the particle size decreases due to the diminishing quantitative share of seed coats. No correlation is observed between true and bulk densities, as the particle shape, surface sculpture, and adhesion affect the mutual particle arrangements. Along with a decrease in the particle size from 0.4 mm, a rapid decrease in the flowability is observed. The tendency of the finest dust (d < 0.075 mm) to form agglomerated complexes causes its lower bulk density, higher porosity, and higher angles of repose in comparison to coarse dust (0.075–0.4 mm). It is concluded that a relatively low tendency to free flowing of natural RSM is mainly caused by its wide-ranging particle size distribution and their geometry differentiation, which facilitate mutual particle interlockings. The known cases of blockages of silos, bins, hoppers, and transfer chutes may be mainly caused by the powder fractions (< 0.2 mm), with a much lower flowability than other particles.