UBC Theses and Dissertations
Durability of wood pellets Oveisi-Fordiie, Ehsanollah
Durability is used for quantifying the quality of pellets by measuring the percentage of broken pellets. This work conducted durability measurement using different approaches, including Dural, Tumbler and drop test, and established relationship between them. In particular, 1) we developed a robust method that measures durability based on Dural. A series of experiments were conducted using eight different machine settings and four types of pellets. It was found that both pellet types and machine settings are statistically significant. The setting represented by 200 g sample, testing duration 15 s and rotational speed 1516 rpm was found to be the most appropriate for Dural. 2) We also conducted drop test for unveiling the effect of different factors on breakage of pellets, such as height, sample size, number of repeated drops, type of bedding and type of pellet. The relation between breakage and height was found to be linear. Harder surface had more impact on pellets. The percentage of dust increased significantly after each drop as the pellets tended to break more readily and the accumulation of fines was approximately 10% after five drops. An asymptote was observed for sample size greater than 1000 g. 3) Finally, we investigated correlations of durability measurement among Tumbler, Dural and drop test. When wood pellets were used, a strong correlation (R² = 0.76) was observed between the Tumbler-measured durability and the Dural-measured durability with a logarithmic curve. The correlation between the durability derived from the drop test versus the Dural tester was significantly stronger (R² = 0.81) than when it was compared to the Tumbler tester (R² = 0.63).
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