Combustions of torrefaction-pretreated bamboo forest residues: Physicochemical properties, evolved gases, and kinetic mechanisms
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Unlike light torrefaction at 200 degrees C (B200), the mild (250 degrees C) and severe (300 degrees C) torrefaction pretreatments (B250 and B300) significantly increased the calorific value, reduced the oxygen content and improved the surface morphology for bamboo residues (BR). The main oxygen-removing carriers of BR during torrefaction were CO2 and carbonyl compounds. Their torrefaction delayed the start and burnout temperatures of the BR combustions, increased CO2 emission and decreased NH3 and NO emissions significantly. The torrefaction reduced their activation energy in zone II (200-350 degrees C) and led to a transition from a nucleation to a diffusion mechanism. All the combustions in zone III (350-500 degrees C) were best explained by a reaction order model whose order rose with the elevated torrefaction temperature. Overall, BR appeared to be more suitable for the torrefaction at 250-300 degrees C. Our results can provide practical insights into how to turn BR into efficient and clean bioenergy.