Characterization of wood powder properties

Abstract

Powder flowability underlies reliable solids handling, influencing dosing accuracy and production stability. Wood powders are usually cohesive and susceptible to flow problems like bridging because of their irregular, fibrous particles that are hygroscopic and heterogeneous. Two lignocellulosic powders were tested: spruce (softwood) and poplar (hardwood). Their particle size distribution, particle shape, and density were measured experimentally. Crucially, the interparticle parameters that govern powder bulk behavior, which are the cohesion energy density (CED), rolling friction coefficient (μᵣ), and sliding friction coefficient (μₛ), are not directly measurable at the scale and morphological complexity of fibrous wood particles. Therefore, using the Discrete Element Method (DEM), (μₛ,μᵣ, CED) were identified as effective DEM parameters by inverse calibration against rotating drum tests. A novel calibration workflow was developed to compare DEM simulations with real rotating drum experiment indicators, which can be used for unconfined, dynamic flow. These indicators correspond to newly discovered macroscopic flow descriptors that are processed from the powder bed: average projected area Area¯, its fluctuation σArea, and the average surface profile irregularity r²¯. Wood particles were modeled as multi-sphere clumps with different sizes to balance realism and computational cost. The calibrated parameters were: spruce—μ_s=0.10, μ_r=0.367, CED=130 kJ/m³; poplar—μ_s=0.10, μ_r=0.772, CED=100 kJ/m³. Following a comprehensive results analysis, increasing CED and friction parameters deteriorates powder unconfined flowability by promoting agglomeration and particle interlocking. The resulting calibrated DEM inputs provide a baseline for predicting and improving the handling of wood powders in hoppers, feeders, and conveying screws.