THERMOGRAVIMETRIC BEHAVIOUR OF DIFFERENT BIOMASS FEEDSTOCKS AND THEIR PYROLYSIS KINETICS

摘要

In this study, biomass feedstocks; softwood pellet, straw pellet, torrefied wood chips and pyrolysis charrnwere investigated in terms of their thermal behaviorto obtain their kinetic parameters (Ea;A). Thermogravimetricrnanalysis (TGA) of the samples under N2 atmosphere were carried out at four different heating rates (2-15 ℃/min) atrn25-850 ℃. Coats&Redfern and Isoconversional Methods were chosen as the model-fitting and model free methods torncalculate pyrolysis kinetic parameters. Straw pellet has the highest ash content (5.85 wt%) and agglomeration indexrnof 1.27. It seemed to be more prone to agglomeration during thermochemical conversion. Its lowest ash fusionrntemperature (FT=1256 ℃) supported its agglomeration tendency as well. In the scope of kinetic analysis, the choicernon the starting and end points of decomposition stages was determinative in Coats&Redfern method, whereasrnIsoconversional method was evaluated to be independent from the choice of the stages. Calculated activation energiesrnand characterization studies indicated that both torrefied wood chips and softwood pellet were the samples whichrnmight be more reactive to thermochemical conversions and less prone to agglomeration. Although pyrolysis charrngave the lowest agglomeration index (0.37),its high decomposition temperature (>850 ℃) is the potential drawbackrnin front of its utilization via pyrolysis.