Effect of torrefaction on thermal behavior and fuel properties of Eucalyptus grandis macro-particulates

Considered as a carbon-neutral fuel from a climate change perspective and the most common renewable resource, biomass needs an energetic conversion process to replace more conventional energy sources. Torrefaction is a thermal modification process used to improve biomass as solid fuel. In this study, macro-particles of Eucalyptus grandis were investigated under an oxidizing atmosphere (10% O-2). The aim was to evaluate the effect of the temperature (230, 250, 270 and 290 degrees C) and heating rates (3, 5 and 7 degrees C min(-1)) on 3 x 3 x 3 cm samples by the assessment of the dynamic solid yield and its derivative curve, proximate analysis as well as energy content. The solid yield decreases with increasing temperature showing a linear relationship (R-2 = 0.97) for light and mild torrefaction and more aggressive behavior for severe torrefaction (280 and 290 degrees C) with degradation varying from 6.7 to 34.8% and a higher heating value enhancement varying from 3.4% (230 degrees C) to 24.3% (290 degrees C). The approach followed allows a characterization of biomass samples, thermal behaviors dynamics as well as the torrefied final product showing the impact of temperature, heating rate and residence time.