Fundamental Study on Production of "Hyper Wood Pellet" - (2) Effect of Torrefaction Condition of Japanese Wood Chips on Grinding and Pelletizing Properties

Abstract

To upgrade conventional wood pellets, Japanese softwood and hardwood chips were torrefied at around 200 – 350oC, and pelletized. The characteristics of torrefied material/pellets such as their calorific value, grinding energy, pelletizing energy and elemental composition, were also evaluated in this study. The calorific value, which increased with rising torrefaction temperature, exceeded 25MJ/kg (representing an increase of nearly 40% compared to the untreated state) for torrefaction at around 350oC. The grinding energy decreased with increasing torrefaction temperature, and the reduction effect was larger for Japanese oak hardwood chips. The pelletarization energy for the torrefied material tended to be slightly smaller than in the untreated case. Elemental analysis revealed that a decrease in the atomic ratio of H/C and O/C was observed for torrefied pellets.