Study on the quality of oat hull fuel pellets using bio-additives

Fuel pellets made from compressed biomass represent an important product for energy sector as they are used as a fuel for power generation and for residential heating appliances such as boilers and furnaces. As an available agricultural residues in Saskatchewan, Canada, oat hull was considered as a feedstock for the fuel pellets. In this study, the effect of bio-additives, such as lignin and amino acids, on the quality of the oat hull pellets was investigated using single pelleting unit. The oat hull feedstock was characterized using different methods including FI-IR, XRD, TGA, solid state NMR, and Raman spectroscopy. Proline was found to be the best amino acids to be used as an additive with lignin. Results have shown that pellets with lignin content ≥15% and proline content ≥5% had the highest density, durability, and hardness. In addition, ash content and HHV of the pellets increased with increasing lignin content. Increasing die temperature and compression force enhanced the quality of the pellets, whereas compression time did not have a significant effect. Even though microwave torrefaction increased the hydrophobicity and HHV of the pellets, it negatively impacted the density, durability, and hardness of the pellets. Computed tomography (CT) analysis was performed in the Canadian Light Source Inc. to visualize the internal structure of the pellets. CT analysis showed that the porosity of the pellets increased with decrease in additives content, pelletization temperature, and compression force. Microwave torrefied pellets showed higher porosity compared to that of untreated pellets.