Torrefaction of Larix Kaempferi C. and Liriodendron Tulipifera L. Cubes: Impact of Reaction Temperature on Microscopic Structure, Moisture Absorptivity, and the Durability of Pellets Fabricated with the Cubes

Abstract

Larch (LAR) and yellow poplar (YP) cubes were torrefied at 180, 220 and 260 ℃ for 50 min to determine the alterations in their structural and hydrophobic properties. Through microscopic observations, several cracks and crevices were found on the radial- and tangential-sectioned areas of the 260 ℃-torrefying YP cubes. On the tangential-sectioned areas, horizontal resin canal for LAR and ray cells for YP were darker than vertical cells. Moisture absorptivity (MA) measured for investigating the hydrophobicity of the torrefied LAR and YP cubes decreased with the increase of torrefaction temperature. However, no obvious differences were observed between the colors of the surface and internal parts or between the internal parts of the cubes visually at each torrefaction temperature. In addition, MA of the LAR and YP cubes was not significantly influenced by the depth of the cubes. Accordingly, it can be concluded that the carbonization level of the LAR or YP cubes is affected more by torrefaction temperature th...