Comparison of Thermal Properties and Kinetics of Selected Waste Wood Samples in Two Different Atmospheres

Abstract

Knowledge of the kinetics and thermal decomposition properties of woods are of great importance. Successful design and control of technologies for the pyrolysis and combustion of lignocellulosic raw materials require a good understanding of the kinetics of the thermochemical processes. In this chapter, thermal properties and kinetic constants of selected waste wood samples (pine, medium-density fiberboard, and plywood) are examined in two different atmospheres, nitrogen and air, by thermogravimetric analysis. Samples were sieved to 3 mm and a heating rate of 10 °C/min was used. In nitrogen atmosphere, two peaks were observed for all samples due to moisture and volatile content of the samples. However, in air atmosphere three peaks were observed owing to removal of moisture, active oxidation of volatile matter, and char combustion. Activation energies of the samples in air atmosphere were higher than in the nitrogen atmosphere. Consequently, it can be said that all samples were more thermally stable in an air atmosphere than in a nitrogen atmosphere. Furthermore, a diffusion-controlled reaction starting on the exterior of spherical particles was found to be the main mechanism for all waste wood samples.