Torrefaction of biomass pellets is considered as a
useful pretreatment technology in order to convert them into a high
quality solid biofuel that is more suitable for pyrolysis, gasification,
combustion, and co-firing applications. In the course of torrefaction,
the temperature varies across the pellet, and therefore chemical
reactions proceed unevenly within the pellet. However, the
uniformity of the thermal distribution along the pellet is generally
assumed. The torrefaction process of a single cylindrical pellet is
modeled here, accounting for heat transfer coupled with chemical
kinetics. The drying sub-model was also introduced. The nonstationary
process of wood pellet decomposition is described by the
system of non-linear partial differential equations over the
temperature and mass. The model captures well the main features of
the experimental data.
 P. C. A. Bergman, A. R. Boersma, R. W. R Zwart, J. H. A. Kiel.
Torrefaction for biomass co-firing in existing coal-fired power stations.
“Biocoal”. Technical Report ECN-C-05-013. Petten, The Netherlands:
 J. J. Chew, V. Doshi. Recent advances in biomass pretreatment —
torrefaction fundamentals and technology. Renew SustEnerg Rev, 15
(2011), pp. 4212–4222.
 A. Uslu, A.P.C. Faaij, P.C.A. Bergman. Pre-treatment technologies, and
their effect on international bioenergy supply chain logistics. Technoeconomic
evaluation of torrefaction, fast pyrolysis and pelletisation.
Energy 33 (2008), pp. 1206–1223.
 P. C. A. Bergman Combined torrefaction and pelletisation: the TOP
process, Report No.: ECN-C-05-073, Energy Research Centre of the
Netherlands (ECN), Petten, The Netherlands, 2005, pp. 29.
 R B. Bates, A.F. Ghoniem. Modeling kinetics-transport interactions
during biomass torrefaction: The effects of temperature, particle size,
and moisture content. / Fuel 2014; 137: pp. 216–229.
 R B. Bates. Modeling the coupled effects of heat transfer,
thermochemistry, and kinetics during biomass torrefaction. MSc thesis,
Massachusetts institute of technology, 2010.
 M. J. C. Van der Shtelt. Chemistry and reaction kinetics of biowaste
torrefaction. PhD thesis, Eindhoven University of Technology; 2011.
 W-C. R. Chan, M. Kelbon, B. B. Krieger. Modelling and experimental
verification of physical and chemical processes during pyrolysis of a
large biomass particle. Fuel 1985;64: pp. 1505–1513.
 C. Di Blasi, S. Branc, Sparano, LaB Mantia. Drying characteristics of
wood cylinders for conditions pertinent to fixed-bed countercurrent
gasification. Biomass Bioenergy 2003;25: pp. 45–58.
 W. J. Parker Development of a model for the heat release rate of wood: a
status report. Gaithersburg, MD: US National Bureau of Standards;
 B. Krieger-Brockett, D. Glaister. Wood devolatilization – sensitivity to
feed properties and process variables. In: Bridgwater AV, Kuester JL,
editors. Res. Thermochem. Biomass Convers.. Netherlands: Springer;
1988. p. 127–42.
 S. Shrestha, Cramer S, White R. Time temperature profiles across a
lumber section exposed to pyrolytic temperatures. Fire Mater
 K. M. Bryden, K.W. Ragland, C. J. Rutland. Modeling thermally thick
pyrolysis of wood. Biomass Bioenergy 2002;22:41–53.
 M. G. Grønli A theoretical and experimental study of the thermal
degradation of biomass. PhD thesis, Norwegian University of Science
and Technology; 1996.
 J. C. Wurzenberger, S. Wallner, H. Raupenstrauch, J. G. Khinast.
Thermal conversion of biomass: comprehensive reactor and particle
modeling. AIChE J 2002;48: pp. 2398–2411.
 H. Lu, W. Robert, G. Peirce, B. Ripa, L. L. Baxter. Comprehensive
study of biomass particle combustion. Energy Fuels 2008; 22: pp. 2826–
 N. Ouelhazi, G. Arnaud, J.P. Fohr. A two-dimensional study of wood
plank drying. The effect of gaseous pressure below boiling point. Transp
Porous Media 1992; 7: pp. 39–61.
 S. S. Alves, J. L. Figueiredo. A model for pyrolysis of wet wood.
ChemEngSci 1989; 44: pp. 2861–2869.
 A. Galgano, C Di Blasi. Modeling the propagation of drying and
decomposition fronts in wood. Combust Flame 2004; 139: pp. 16–27.
 J. Porteiro, J. L. Míguez, E. Granada, J. C. Moran. Mathematical
modelling of the combustion of a single wood particle. Fuel Process
Technol 2006; 87: pp. 169–75.
 B. Peters, E. Schröder, C. Bruch, T. Nussbaumer. Measurements and
particle resolved modelling of heat-up and drying of a packed bed.
Biomass Bioenergy 2002; 23: pp. 291–306.
 R. Bilbao, J. F. Mastral, J. Ceamanos, M. E. Aldea. Modelling of the
pyrolysis of wet wood. J Anal Appl Pyrolysis 1996; 36: pp. 81–97.
 J. Saastamoinen, J-R. Richard. Simultaneous drying and pyrolysis of
solid fuel particles. Combust Flame 1996; 106: pp. 288–300.
 P. D. Aerts, K. W. Ragland. Pressurized downdraft combustion of
woodchips. Twenty-Third Symp Int Combust 1991; 23: pp. 1025–32.
 M. Bellais. Modelling of the pyrolysis of large wood particles. PhD
thesis, KTH Royal Institute of Technology; 2007.
 B. Peters, C. Bruch. A flexible and stable numerical method for
simulating the thermal decomposition of wood particles. Chemosphere
2001; 42: pp. 481–90.
 Е. Artiukhina, P. Grammelis, G. Sin. Biomass pellet torrefaction: 2D
model development, reliability assessment by sensitivity and uncertainty
analyses, to be published.
 H. A. Noves, J. I. S. Fernandez-Golfin. Practical evaluation and
operation of superheated steam drying process with different softwoods
and hardwoods. Eur J Wood Wood Prod 1994; 52: pp. 135–138.