The kinetics of the pyrolysis of lignocellulosic materials was studied with a view of providing simple kinetic models for engineering purposes. Experimental data obtained by means of thermal analysis techniques suggest that the pyrolysis of fine particles (below 1 mm) can be considered to be controlled by pyrolysis kinetics. The rate of pyrolysis of one biomass type can be represented by the sum of the corresponding rates of the main biomass components (cellulose, lignin, hemicellulose). The kinetics of each of these components was simulated by a kinetic scheme capable of predicting the pyrolysis rate and the final weight-loss for a wide range of pyrolysis parameters including various heating conditions. On a étudié la cinétique de la pyrolyse de matériaux lignocellulosiques dans le but de fournir des modèles cinétiques simples à des fins d'ingénierie. Des données expérimentales obtenues par le biais de techniques d'analyse thermique permettent de croire que la pyrolyse de particules fines (au-dessous de 1 mm) peut ětre contrǒlée par la cinétique de pyrolyse. La vitesse de pyrolyse d'une biomasse donnée peut ětre représentée par la somme des vitesses correspondantes des composants de biomasse principaux (cellulose, lignine, hèmicellulose). La cinétique de chacun de ces composants a été simulée par un schéma cinétique capable de prédire la vitesse de pyrolyse et la perte de poids finale pour un large éventail de paramètres de pyrolyse, y compris de conditions variées de chauffe

The present work provides a rationally‐based model to describe the pyrolysis of a single solid particle of biomass. As the phenomena governing the pyrolysis of a biomass particle are both chemical (primary and secondary reactions) and physical (mainly heat transfer phenomena), the presented model couples heat transport with chemical kinetics. The thermal properties included in the model are considered to be linear functions of temperature and conversion, and have been estimated from literature data or by fitting the model with experimental data. The heat of reaction has been found to be represented by two values: one endothermic, which prevails at low conversions and the other exothermic, which prevails at high conversions. Pyrolysis phenomena have been simulated by a scheme consisting of two parallel reactions and a third reaction for the secondary interactions between charcoal and volatiles. The model predictions are in agreement with experimental data regarding temperature and mass‐loss histories of biomass particles over a wide range of pyrolysis conditions.

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A method for the direct determination of the cellulose and lignin content of biomass has been developed. The method assumes that negligible interactions exist between biomass macrocomponents and it is based on the analysis of thermogravimetric (TG) pyrolysis data. The TG-weighed sum method seems to be reliable and less time consuming than conventional methods for the determination of the cellulose and lignin content. Some limitations of the macrocomponent approach in the description of biomass pyrolysis are also discussed. In particular, hemicellulose pyrolysis data are analyzed. The use of xylans as substitute materials for hemicellulose have been critically examined. The results obtained point out that the widely practiced use of xylans as substitute compounds for the simplified description of hemicellulose pyrolysis can lead to significant errors. On a mis au point une méthode pour la détermination directe de la teneur de la biomasse en cellulose et en lignine. Cette méthode suppose l'existence d'interactions négligeables entre les macrocomposantes de biomasse et repose sur l'analyse de données de pyrolyse thermogravimétrique (TG). La méthode de la somme pondérée des TG semble être fiable et consommer moins de temps que les médiodes traditionnelles de détermination de la teneur en cellulose et en lignine. On décrit également certaines limites de la méthode des macrocomposants dans la description de la pyrolyse de la biomasse. En particulier, des données de pyrolyse d'hémicellulose sont analysées. L'utilisation de xylanes comme matériaux de substitution de l'hémicellulose a été étudiée de facon critique. Les résultats obtenus montrent que l'utilisation largement répandue de xylanes comme composés substituts pour la description simplifiée de la pyrolyse de l'hémicellulose peut entraîner des erreurs importantes