Experimental and numerical multi-scale study of spruce wood degradation under inert atmosphere

The aim of the present work was to study the thermal degradation of spruce wood throughout a multiscale approach. First, thermogravimetric experiments under inert atmosphere with argon were performed with spruce samples reduced into powder. Three heating rates varying between 10 and 30 degrees C.min(-1) were imposed to study the thermal degradation. A reactional mechanism consisting of three steps was defined and the associated kinetic parameters were determined by least-squares minimization using the Levenberg-Marquardt algorithm. The results showed efficient predictions in agreement with experimental data of mass and mass loss rate whatever the heating rate. At material scale, experiments were performed in an atmosphere controlled chamber placed in front of a cone calorimeter in vertical configuration. Spruce samples were exposed to three heat fluxes (38, 49 and 59 kW m(-2)) under inert atmosphere obtained with a constant flowrate of argon. Mass loss and in-depth temperature measured using twelve embedded thin wire thermocouples were recorded. At this scale, the thermal degradation was modeled using a one-dimensional pyrolysis model with GPYRO. The predicted in-depth temperatures are in good agreement despite differences explained by a possible overestimation of thermal properties such as thermal conductivity and heat capacity of char. The predictions showed similar mass loss and charring rates beside the experiments.