Upgraded wood pellets (Hyper wood pellets) were produced and evaluated by torrefaction of wood pellets. In this study, conventional wood pellets were initially prepared and subsequently torrefied on a laboratory and then larger scale. During the laboratory scale production, a few kilograms of pellets from wooden parts of Japanese cedar (Cryptomeria japonica) and Japanese oak (Konara, Quercus serrata) trees were heat treated in an inert gas oven. For the Japanese cedar, the calorific values were improved by heat treatment up to 260°C. By heat treatment at 240°C, the upgrade ratio of HHV was nearly 30% and the energy yield was 97%. For the Japanese oak, the calorific values were improved by heat treatment up to 320°C. By heat treatment at 280°C, the upgrade ratio of HHV exceeded 30% and the energy yield was 84%. On a larger scale, a conventional charcoal oven was modified for Hyper wood pellet production, meaning Hyper wood pellet with 25 MJ of calorific value were produced during heat treatment at 350°C.
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