Kinetic model for torrefaction of wood chips in a pilot-scale continuous reactor

Lei Shang, Jesper Ahrenfeldt, Jens Kai Holm, Lars Stougaard Bach, Wolfgang Stelte, Ulrik Birk Henriksen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Torrefaction is a mild thermal treatment (200-300 °C) in an inert atmosphere, known to increase the energy density of biomass by evaporation of water and a proportion of the volatiles. In this work a "two-step reaction in series" model was used to describe the thermal degradation kinetics of pine wood. The kinetic parameters were determined using a thermogravimetric analyzer (TGA) and the mass loss during the initial heating period was taken into account when deriving the kinetic parameters. It was shown that the experimental results at different heating rates (10-50 °C min-1) are in good accordance with the model data. In an additional step a continuous, pilot scale reactor was built to produce torrefied wood chips in large quantities. The "two-step reaction in series" model was applied to predict the mass yield of the torrefaction reaction. Parameters used for the calculation were the temperature along the reactor and the biomass feeding rate in combination with the kinetic parameters obtained from the tests in the TGA. Together with results from a laboratory scale, batch torrefaction reactor that was used to determine the higher heating value (HHV) and mass loss (y) of the same material at different torrefaction temperatures, it was possible to predict the HHV of torrefied wood chips from the pilot reactor. The results from this study and the presented modeling approach can be used to predict the product quality from pilot scale torrefaction reactors based on small scale experiments and could be used to improve the homogeneity of torrefied products, which still is a problem for most operational torrefaction pilot plants today. © 2014 Elsevier B.V.
Original languageEnglish
JournalJournal of Analytical and Applied Pyrolysis
Volume108
Pages (from-to)109-116
ISSN0165-2370
DOIs
Publication statusPublished - 2014

Keywords

  • Chemical Engineering (all)
  • Chemistry (all)
  • Continuous reactor
  • Kinetics
  • TGA
  • Torrefaction
  • Wood chips, Modeling
  • Degradation
  • Enzyme kinetics
  • Forecasting
  • Kinetic parameters
  • Pilot plants
  • Continuous reactors
  • Pilot-scale reactors
  • Small-scale experiment
  • Thermal degradation kinetics
  • Thermogravimetric analyzers
  • Wood chip
  • Wood products
  • Chips
  • Forecasts
  • Pilot Plants
  • Wood Products

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