Combustion Behaviors, Kinetics, and Thermodynamics of Naturally Decomposed and Torrefied Northern Red Oak ( Quercus rubra ) Forest Logging Residue

Torrefaction and combustion have been applied to naturally decomposed red oak logging residues. The results indicated that four-year natural decomposition would lower the energy density of red oak from 20.14 to 18.85 MJ/kg. Torrefaction reduced the O/C and H/C ratios but improved the energy yield values. Two combustion stages were observed for all samples, and no hemicellulose derivative thermogravimetric peak appeared for torrefied samples. The differential scanning calorimetry exothermic heat flow increased after torrefaction. In addition, the Kissinger–Akahira–Sunose average activation energy of untorrefied samples decreased in the first stage (from 157.77 to 149.52 KJ/mol), while it increased in the second stage (from 131.32 to 181.83 KJ/mol). The ∆ H , ∆ G , and ∆ S values of all samples decreased in the first stage, while they increased when the conversion rate was greater than 0.5 for torrefied samples. These findings can aid in a better understanding of the fuel performance of torrefied and untorrefied naturally decomposed red oak logging residues.