Analysis of wood pellet degradation characteristics based on single particle impact tests

• Published in: Powder technology 2021-01, Vol.378, p.704-715
• Main Authors: Jägers, J., Spatz, P., Wirtz, S., Scherer, V.
• Format: Article
• Language: English
• Subjects: Breakage function; Breakage probability; Fragmentation characteristics; Stereoscopic particle tracking; Various impact conditions; Wood pellet degradation
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2020.10.017

The knowledge of size reduction of wood pellets during pneumatic conveying is important to achieve failure-free system operation and to set-up adequate quality assurance processes. In the present study, experiments are performed with a single particle impact test facility. A stereoscopic high-speed camera set allows 3D-particle tracking and visual analysis of the particles' degradation properties. Based on the data obtained, empirical correlations for the statistical description of the pellets' breakage behaviour are presented depending on particle length, impact velocity and collision angle. These relationships are expressed mathematically by two key functions: the so-called selection function (breakage probability) and the breakage function (fragment size distribution). As expected, higher impact velocities lead to more damage, especially at normal collisions (90°) due to the maximum change of momentum. Furthermore, smaller particles tend to be more breakage resistant as they contain less impurities and cracks. Finally, an outlook on the influence of pellet quality and target material on the particles' degradation behaviour is given. Here, pellets with higher durability tend to break at higher impact loads and into larger fragments. In addition, a softer target material (e.g. HDPE) causes less particle breakage than e.g. steel. [Display omitted] •Design of impact test facility for cylindrical particles•Development of empirical prediction model of wood pellet breakage behaviour•Selection and breakage function for cylindrical biomass particles•Degradation characteristics of cylindrical wood pellets•Analysis of influence of pellet quality and target material on degradation behaviour