Effects of bio-additives on the physicochemical properties and mechanical behavior of canola hull fuel pellets

Agricultural residues can be converted to value-added products such as fuel pellets. Bio-based additives, including alkali lignin, glycerol and l-proline were used for binding formulation of canola hull fuel pellets. The binding formulation was optimized to produce pellet with the mechanical durability (by drop test) of 99%, relaxed density of 1,110 kg/m3, and energy density of 18,603 MJ/m3. l-proline showed the best performance in the enhancement of mechanical properties of pellet when compared with other two amino acids. Comparing with pure glycerol, use of crude glycerol decreased compression energy required for pelletization, but resultant pellet had lower tensile strength. SEM and light microscopy showed the effects of lacking moisture, lignin and l-proline in the formulation. Synchrotron-based computed tomography was used for 3D imaging of fuel pellets yielding estimated porosity values over a range of 1.3-5.7% for different fuel pellets. The effects of pelletization operating conditions were also investigated on the pellets.