Laser-Based Spectroscopy Diagnosis and Detailed Numerical Models to Gain Understanding on the Slow Pyrolysis Behavior of Thermally Thick Wood Particles

Abstract

The slow pyrolysis behaviour of thermally thick wood particles is investigated at 5, 10 and 20 °C/min, combining an advanced single-particle experimental approach with a detailed numerical model. Infrared laser absorption spectroscopy (IRLAS) and laser-induced fluorescence spectroscopy (LIF) are used to characterize on-line and in-situ the evolution of the following volatile products in the close vicinity of the pyrolysing particle: CO₂, CO, CH₄, H₂O, CH₂O and fluorescence-emitting species with excitation wavelengths of 266 and 355 nm, such as polycyclic aromatic hydrocarbons (PAH). The numerical particle model is coupled with a detailed pyrolysis kinetic scheme, being able to predict with good accuracy mass loss, temperature evolution and online release of species such as H₂O and CO. Model predictions are in some cases even better than for the medium heating rate conditions for which the model was initially tested, showing its wide applicability. Furthermore, the model can be improved including PAH release, for which experimental data is presented, and the delayed release of CH₄, which is not correctly described by the model at low heating rates.