PYROLYSIS KINETICS OF LIGNOCELLULOSIC MATERIALS

Pyrolysis kinetics of almond and hazelnut shells and beech wood were c arried out using a thermogravimetric technique. Experiments were repea ted for different final pyrolysis temperatures ranging from 300 to 850 -degrees-C. Approximately 90% of the pyrolysis reactions were complete d up to 450-degrees-C. The initial values of the activation energy of pyrolysis reaction were found to be around 22 kcal/mol for shells of a lmond and hazelnut. On the other hand, initial activation energy of be ech wood pyrolysis was found as 29.4 kcal/mol. Results indicated that a first-order decomposition in terms of volatile content of the reacta nt showed good agreement with the data only at the initial stages of t he reaction. The reaction rate constant was found to decrease with rea ction extent due to the changes in the chemical and physical structure of the solid. Among several models proposed, a model which predicted an increase of activation energy with reaction extent gave the best ag reement with the experimental data.