(82a) Influence of Thermal Treatment Temperature On Wood Structures

Utilization of biomass as a co-feed supplement with coal in various coal-fired/gasification energy conversion processes is typically thought to require size reduction of the biomass. It is difficult to reduce/pulverize biomass without pretreatment because biomasses are fibrous and compressible. Torrefaction is identified as a promising thermal pretreatment process. After torrefaction, biomass becomes brittle and friable and its grindability is improved. Biomass grindability relates to the mechanical properties of biomass, which is in turn related to cell wall structure and the thickness of the cell walls. The cell wall composition of biomass consists of cellulose, hemicelluloses and lignin. During thermal treatment such as torrefaction, hemicellulose is the most reactive of the three components and is preferentially decomposed. Thermal treatment causes chemical changes that can alter the structure of biomass and the treatment temperature used is probably the most important factor. The objectives of this study are to investigate the impacts of thermal treatment temperature on the hardwood microstructure using SEM and to understand the mechanism of how torrefaction can improve the grindability of wood biomass. Four pieces of hardwood cut from axial and radial systems will consecutively be treated at 200, 250, 300, 350, 450 and 600oC for 0.5 hr. After each thermal treatment the wood samples will be examined using SEM, and the sample cell wall compositions will be analyzed using TGA. The cell wall structure models reported in the literature will be used to elucidate the mechanism of the wood structure change and its component decomposition caused by thermal treatment at different temperatures.