Relationship between Pellet Strength and Chemical Composition of Torrefied Cellulose
Yuto NODA, Shiho IKEDA, Takuya YOSHIDA, Yoshimitsu UEMURA, Hiroshi NONAKA
Torrefaction of wood chips improves crushability, making it easier to apply to coal co-firing power generation. On the other hand, after torrefaction, the interaction between the coarsely ground particles is weak and pelletization is difficult. In this study, commercial cellulose powder was torrefied at 250-280 °C for 30 or 60 minutes in a small carbonization furnace in order to clarify the effect of torrefaction temperature and time on cellulose, which is the main component of wood. Subsequently, 0.2 g of the torrefied sample was pelletized by compression molding, and the relationship between the composition of the torrefied cellulose and the pellet strength was examined. Sugar composition analysis based on two-step sulfuric acid hydrolysis revealed that the amount of acid-insoluble components increased with the progress of torrefaction, and the corresponding pellet strength decreased significantly. It was also clarified that there is a strong correlation between the remaining amount of cellulose in the sample and the strength of the pellets. It was suggested that cellulose contributes to the bonding between the coarsely ground particles, and it was presumed that moderate torrefaction conditions of about 250 °C with little denaturation of cellulose would not adversely affect pelletization.