Pyrolysis of a Single Wooden Particle: a Numerical Model Calibrated Versus Intraparticle Gas Sampling Measurements

The aim of this work is to assess the thermal exchanges and the volatile distribution within a single wooden particle subjected to pyrolysis. A two dimensional axial­symmetric representation of the particle has been used, and the mass, momentum and energy conservation equations have been integrated by means of a finite­volume method. Wood has been considered as an isotropic porous medium. The thermal properties of the solid reagent medium (e.g., thermal conductivity and diffusivity of wood) have been measured through laser flash analysis (LFA). Boundary conditions have been set in accordance with the experimental tests used for the model calibration. The model has been in fact calibrated versus experimental data that have been obtained during pyrolysis tests under non­oxidant (340 cm3/min of Helium) controlled conditions, performed with spherical wooden particles of different sizes (19.0 mm and 31.8 mm diameter) in a tubular stainless steel reactor (internal diameter: 3.8 cm; length: 30.5 cm) inserted in an electrically heated furnace. The temperatures on the surface and in the center of the wooden sphere have been monitored during the process, confirming the behavior shown in other studies. In addition, an innovative intraparticle sampling methodology have been applied, in order to analyze through gas chromatography the evolved gas at the center of the particle. In particular, the detected components have been: CO2, CO, CH4, C2H6, C2H4 and H2. The proposed approach allowed a detailed characterization of the distribution of the evolved gas inside the particle, providing useful information for the assessment of the reaction happening inside it.
Proceedings of the 22nd European Biomass Conference and Exhibition, 23-26 June 2014, Hamburg, Germany, pp. 912-919