Inverse analysis of wood pyrolysis with long residence times in the temperature range 210-290 °C: Selection of multi-step kinetic models based on mass loss residues

The aim of this paper is to evaluate different types of kinetic models and to propose a set of kinetic parameters for simulating the heat treatment of woody biomass under temperatures representative of torrefaction conditions. The mass loss of three wood types, locust, spruce and eucalyptus, as well as their main components, cellulose, xylan, glucomannan and lignin, has been determined in a TGA at different isothermal temperatures between 210 and 290 °C for residence times of up to ten hours. These data were used to evaluate the kinetic parameters corresponding to various multi-step series reaction mechanisms proposed in the literature. A computational solution of the multi-step formulation was derived, which allows the exact conditions undergone by the sample to be used as input parameters. The inverse procedure takes into account simultaneously the different temperature levels for each species. A comprehensive table summarizes all results, among which the dimensionless residues, proposed as a guideline to choose the relevant mechanism complexity. Overall we find that 2-step series reaction models provide acceptable accuracy for reproducing the mass loss from lignocellulosic biomass and their constituents under torrefaction conditions.