Non-oxidative torrefaction of biomass to enhance its fuel properties

Abstract

Torrefaction upgrades the biomass as an energy source enhancing its poorest characteristics. Non-oxidative torrefaction of six biomass samples (pine, eucalyptus, chestnut, holm oak, olive tree pruning and vine shoot) was conducted in a tube furnace reactor within the range 200–300 °C and proximate, ultimate and heating value analysis as well as wettability studies were carried out to characterize the torrefied samples and find the optimal temperature of the process. In addition, Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was performed and chemical-kinetics parameters of torrefaction were obtained at optimal temperature. At optimal torrefaction temperature, moisture was reduced up to 2.5% and H/C and O/C atomic ratios up to 1.3 and 0.6, respectively. Contact angle measurements show an increase in hydrophobic behaviour. Lignin was affected by torrefaction since decomposition products from guaiacyl (G) and syringyl (S) units were released during Py-GCMS experiments. The global reaction order was 2.2 and kinetic constant values were in the range 2.17·10−5 to 4.83·10−5 s−1.