Analyzing bulk solid properties for elongated particles of biomass and recyclable material

As single-use plastics and wasted biomass become more common, recycling processes are growing to an industrially large scale that can be characterized by the field of bulk solids. Many of these recyclable materials take the form of elongated particles, which have been frequently overlooked in favor of spherically-shaped particles in existing research on bulk solids. In order to develop a bulk solid model for elongated particles, the critical parameters of bulk density and compaction strength needed to be examined. These parameters can be used when designing hoppers and silos for industrial recycling processes. Polypropylene fibers and wood chips were selected to be the representative materials used in these experiments. Compression tests involving cyclic compaction were used to determine bulk density of the selected materials and measure variance with particle size. In order to measure strength, the selected materials were studied using failure tests in which pre-compressed material was stressed until yielding. Our results indicated that bulk density for elongated particles is positively correlated with increasing diameter, while length has no significant effect. Results from the failure tests indicated that compaction strength increases with pre-compression load and that strength may be highest with a critical diameter that varies by material.