Torrefaction Kinetic Model of Lignocellulosic Materials Based on Fibers Thermal Decomposition Reactions

In these last years, in the context of thermochemical conversion processes, the mild thermal process known also as “torrefaction” has emerged as particularly strategic in view of enhancing the entire biomass chain exploitation value. In particular the kinetic studies of this process has become important in supporting the design procedure expected to widespread the industrial applications linked to torrefaction. The aim of this study consists in proposing a kinetic model for torrefaction of lignocellulosic materials based on a combination of the three independent reactions set up to describe the thermal degradation of each of the constituent fibers: hemicelluloses, cellulose and lignin. This approach is based on the hypothesis proposed by Shafizadeh and McGinnis that assumed that the three fibers, during thermal degradation, present the behaviour they have when they are treated separately. By utilizing the thermogravimetric data (TGA) of the single fibers, in this work it is demonstrated that it is possible to set up a kinetic model for the thermal degradation of different biomasses that presents an enhanced predictive character. Within the torrefaction temperature conditions, usually in the range of 475K – 590K, the maximum deviation error s is nearby 4% while AAD to 1%.