Effect of torrefaction on the physicochemical properties of eucalyptus derived biofuels: estimation of kinetic parameters and optimizing torrefaction using response surface methodology (RSM)

Abstract

Torrefaction of eucalyptus has been carried out in a tubular quartz reactor at different temperatures and residence time under the nitrogen atmosphere. Based on statistical analysis, temperature and residence time both have negative and positive effects on solid yield and HHV, respectively. The temperature had a more severe impact on physicochemical properties as compared to residence time. Based on maximum HHV, the optimum condition has been obtained near 280 °C and 60 min of residence time. Both O/C and H/C ratios have decreased with increasing temperature. There has been an increase of 37.1 and 12.9% in HHV and energy density, respectively, for TEC-280-60 as compared to REC. The decrease in value of CCI and HR with severity resulted in lesser compactability and better flowability, respectively. There have been 433.3% increase and 76.2% decrease in fuel ratio and combustibility index, respectively, for TEC-280-60 as compared to REC. Torrefied biomass, as compared to raw biomass, showed better solid fuel properties for co-combustion with coal. Kinetic parameters revealed that overall activation energy decreased from 179.1 to 81.7 kJ/mol for TEC-280-40 as compared to REC. There has been a decrease in thermal stability of lignin with an increase in severity. © 2020 Elsevier Ltd