Experimental and numerical analysis of wood thermodegradation

Torrefaction is a thermal treatment step in a temperature range of 210-240 A degrees C, which aims to improve the dimensional stability and durability of wood. The mass loss kinetics for torrefaction of wood samples was studied using equipment specially conceived to measure mass losses during thermal treatment. Laboratory experiments were performed under nitrogen for heating rates of 0.1, 0.25, 1, and 2 A degrees C min(-1). A mathematical model for the kinetics of the thermodegradation process was used and validated. Measurements of temperature distribution and anhydrous mass loss were performed on dry sample of poplar wood during torrefaction in an inert atmosphere for different temperatures. The mathematical formulation describing the simultaneous heat and mass transfers requires coupled nonlinear partial differential equations. These unsteady-state mathematical model equations were solved numerically by the commercial package FEMLAB for the temperature under different treatment conditions. A detailed discussion of the computational model and the solution algorithm is given below. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.