Study of silo discharge using different biomass materials

Standard methods used for determining flow properties of common granular solids are not always suitable for biomass materials [1]. Conventional shear testers have been developed for measuring frictional and cohesive properties of bulk solids with non-fibrous rigid and generally homogeneous particle shapes with particle top sizes below a few millimeters. Biomass materials tend to have particle size and shape distributions, and entanglement and stiffness properties that do not meet the requirements for obtaining a well-defined shear zone and steady state flow conditions necessary for shear testing. In this study, silo discharge properties for wide ranges of European biomass raw materials; both from forestry and agriculture, were analyzed by the use of an experimental test silo. Procedures for material processing of the various assortments, i.e. chipping, shredding, milling, and fractioning into sub-samples and the resulting properties, i.e. bulk density, compressibility, were described and analyzed. Particle size and shape analysis was performed by on-line measurement methods by the use of ScanChip® and Camsizer® technologies. The obtained data set, consisting of both descriptive information on material treatment methods and of particle and bulk characterization data is a unique basic asset for knowledge building regarding material preparation routes for favorable biomass bulk properties. Multivariate modelling, earlier proven useful in biomass particle feeding explanatory theory building [2], was applied to the obtained data set to determine correlations and predictive powers for biomass feedstock factors vs. silo discharge responses.