The Effect of Pellet Length on Mechanical Durability and Breakage Behaviour of Torrefied Biomass

The transportation, handling, and storage of biomass pellets are challenging due to pellet breakage and fines generation. The amount of fines generated during transportation and handling of biomass pellets is mostly measured in the laboratory using mechanical durability testers such as tumbling can method according to ISO 17831-1. This standard sets requirements on the amount of pellets, but not on the pellet length distribution (PLD) to be used for the mechanical durability measurements. This study aims to investigate the effect of PLD on the mechanical durability of biomass pellets. Two different types of torrefied biomass of Poplar and Mixed wood were used in this study. Samples were classified into three different groups of shorter than 15 mm, between 15 and 30 mm, and longer than 30 mm before durability test. In addition, a random PLD was considered as a reference case. The results show that the mechanical durability strongly depends on the PLD and increases from 83.6% to 96.4% for torrefied Poplar and from 92.7% to 98.5% for torrefied Mixed wood by increasing the PLD from shorter than 15 mm to longer than 30 mm. Therefore, it is highly recommended to consider the PLD of the pellet samples before durability tests.