Fuel pellet breakage in pneumatic transport and durability tests

Wood pellets for biofuel utilization are fragile and produce fines and dust when handled. Impact resistances of pellets were obtained by using tumbling box tester, ligno tester and rotary impact tester. The samples were sieved after each of the ten consecutive runs to generate a breakage vector of particle size classes: 0-1.00, 1.00-2.36, 2.36-3.15, 3.15-4.75 and > 4.75 mm. Similarly, a full-scale pneumatic blow wood pellets degradation experiment was conducted.The pellets were blown at different delivery pressures from 0.3 to 1 bars. The breakage patterns disclosed two independent mechanisms when analysed by multivariate modelling: surface breakage by the tumbling box and volume breakage by the rotary impact tester. The combination of these testers can describe the full outcome space for the pneumatic tests and it is possible to predict generation of fines and dust during pneumatic loading of wood pellets from a silo. The most severe damages corresponded to more than 10 times 500 revolutions in a tumbling box and 8 consecutive impacts at almost 20 m/s in the rotary tester. Furthermore, these results provided insights into pellet breakage mechanisms, evaluation of pneumatic pipe designs and construction of bench testing devices that purify the effect of surface vesus volume breakage. (C) 2020 Elsevier Ltd. All rights reserved.