Comparative advantages analysis of oxidative torrefaction for solid biofuel production and property upgrading.

[Display omitted] • Oxidative torrefaction is more efficient for upgrading biochar. • The maximum relative mass loss of oxidatively torrefied biochar is much higher. • The relative elemental C content of oxidatively torrefied biochar is higher. • Increasing temperature gradually decreases biochar's carbide carbon proportion. • Strong linear distributions between TSI versus elemental C and O exhibit. This study performs the comparative advantage analysis of oxidative torrefaction of corn stalks to investigate the advantages of oxidative torrefaction for biochar fuel property upgrading. The obtained results indicate that oxidative torrefaction is more efficient in realizing mass loss and energy density improvement, as well as elemental carbon accumulation and surface functional groups removal, and thus leads to a better fuel property. The maximum values of relative mass loss, higher heating value, enhancement factor, and energy yield are 3.00, 1.10, 1.03, and 0.87, respectively. The relative elemental carbon, hydrogen, and oxygen content ranges are 1.30–3.10, 1.50–3.30, and 2.00–6.80, respectively. In addition, an excellent linear distribution is obtained between the comprehensive pyrolysis index and torrefaction severity index, with elemental carbon and oxygen component variation stemming from pyrolysis performance correlating to the elemental component and valance. [ABSTRACT FROM AUTHOR]