Pyrolysis behaviors of woody biomass torrefied at temperatures below 300°C

Torrefaction is the thermal treatment techniques performed at relatively low temperature (< 300 °C) in an inert atmosphere, which aims to improve the fuel energy density and the fuel grindability. In this study, woody biomass (Leucaena leucocephala) was torrefied at various temperatures and holding times and the pyrolysis behaviors of the torrefied wood was examined in detail by using TG-MS technique. It was found that the carbon content and the calorific value of the torrefied leucaena increased significantly when increase the temperature and holding time during the torrefaction. From the TG-MS analysis, the pyrolysis behaviors of the torrefied leucaena were significantly different from that of the raw leucaena. The char yield at 800 °C for the torrefied leucaena was increased when increasing the holding time during the torrefaction. On the other hand, the tar yield during the pyrolysis decreased significantly with the increase in the holding time during the torrefaction. Through the results from the TG-MS analysis, it was concluded that the structure of leucaena was changed by the torrefaction at temperature below 275 oC and the cross-linking reactions occurred during the pyrolysis resulting in increase in char yields and decrease in tar yields. It was also suggested that the longer the holding time during the torrefaction, the more the cross-linking reactions proceed during the pyrolysis. The results obtained from the study provide the basic information for the pyrolyser and/or gasifier design by using torrefied biomass as a fuel.