Torrefaction of Short Rotation Coppice of Poplar under Oxidative and Non-Oxidative Atmospheres

Abstract

Torrefaction improves some of the poorest characteristics of biomass such as hygroscopicity, low energy density, or poor grindability which may cause some problems during its handling, storage and combustion. The aim of this work is to apply the torrefaction process to a Short Rotation Coppice of Poplar (SRCP) and characterize the new fuel. Therefore, both non-oxidative and oxidative torrefaction of SRCP were conducted in a tube furnace reactor within the range 200–240 °C and the torrefied biomass was fully characterize, i.e., proximate, ultimate, compositional and heating value analysis as well as wettability studies. In addition, Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) was performed at optimal torrefaction temperature. Torrefaction kinetics were obtained using a thermogravimetric analyzer at optimal torrefaction temperature. Minimum mass and energy yields were found to be respectively 85.0% and 87.4% for oxidative torrefaction and 87.5% and 94.1% for non-oxidative option. Moisture was reduced from 6.97% to 4.8% and 4.4% for oxidative and non-oxidative torrefaction, respectively. Wettability studies carried out show an increase in hydrophobic behavior. Lignin was affected by torrefaction since decomposition products from guaiacyl (G) and syringyl (S) units were released during Py-GC/MS experiments. The reaction orders were 1.92 and 1.82 for oxidative and non-oxidative torrefaction, respectively and kinetic constant values were 5.99·× 10−5 and 2.98·× 10−5 s−1.