Physical and Flow Properties of Southern Pine Biomass, Bituminous Coal, Plastics Waste, and Blends

Highlights Quantification of the physical and flow properties of southern pine biomass, bituminous coal, and mixed plastics waste. The densities (bulk, particle, tap) were influenced by the particle size and material characteristics. The flowability depends on the wall type, surface roughness, and the material's physical properties. ABSTRACT. Handling of bulk solid materials is primarily influenced by their physical properties, including bulk density, particle density, and particle size. These characteristics are crucial for designing effective handling systems. This paper experimentally quantifies physical properties (density, size, and porosity) and flow properties (flow index, angles of internal and wall friction, cohesion, and adhesion) of southern pine, coal, and plastics, and their blends. Impact of the blend ratio on the physical properties was also investigated. Results showed that polystyrene (PS Styrofoam) exhibited the lowest bulk and tap densities and the highest porosity, while coal displayed the highest bulk and tap densities and lowest porosity. Hausner ratio ranged from 1.1 to 2.4 and tended to decrease as particle size decreased for all samples. Additionally, samples including pine, high-density polyethylene (HDPE), and polystyrene (PS Styrofoam) were classified as cohesive (flow indexes <4), whereas polypropylene (PP) and polyvinyl chloride (PVC) showed easy-flowing characteristics (flow indexes >4). Coal exhibited the highest angle of wall friction on stainless steel (14.5°) and galvanized steel (23.1°), while low-density polyethylene (LDPE) had the highest wall friction angle (17.2°) on TIVAR 88 surface. Bulk and particle densities decreased with increasing plastic content but increased with higher coal content. Porosity followed the opposite trend, decreasing with coal and increasing with plastic. The predictive model developed for bulk and particle densities aligned closely with experimental data, with relative errors of 1.4% for particle density and 12.4% for bulk density. These findings are critical for equipment design in bulk solids handling. Keywords: Adhesion, Biomass, Cohesion, Density, Flow index, Flowability.