Effect of feedstock and process variables on biomass pellet formation phenomena
University of New Brunswick
Densification and springback behaviour of pellets were analysed from selected feedstock and process parameters. Springback due to elastic recovery in fibrous materials after the densification process considerably increases the overall dimensions of the densified biomass due to expansion that happens during decompacting and the ejection stage. A multiple linear regression analysis to predict the length of pellets under compression in the die was carried out and excellent correlation was obtained. Springback characteristics based on axial changes after the compaction process were analyzed and parameters providing lowest expansion were identified. Biomass compact under compressive load was analysed mathematically by a finite difference method. The model explained the effect of frictional forces and compact geometry on stress and density distributions. Axial and diametrical compression tests helped identify parameters providing maximum pellet strength and scanning electron microscopy of fractured pellets helped analyze the bonding mechanisms.