Pelletization of torrefied sawdust and properties of torrefied pellets

Pelletization of torrefied sawdust from a fluidized bed reactor was investigated to quantify the energy consumption and pellet properties, including moisture adsorption, pellet density and Meyer hardness. Energy consumptions in compaction and extrusion for torrefied sawdust were significantly higher than those for untreated sawdust at the same compression temperature, while the moisture uptake rate of pellets decreased with increasing the severity of torrefaction. The densities of torrefied pellets were lower than the control pellet due to the loss of chemically bonded water and low-melting point compounds during torrefaction which act as a binding agent when softened at ∼100°C. The properties of pellets were affected by the removal of most low-melting or – softening point components.