Poplar wood torrefaction: Kinetics, thermochemistry and implications

Abstract

The kinetic and thermochemical models for poplar wood torrefaction were developed in the present work. The torrefaction kinetic model satisfactorily fitted the experimental thermogravimetric analysis (TGA) data of poplar wood torrefaction and provided a coherent description of the evolution of torrefaction volatile and solid products in terms of a set of identifiable chemical components and elemental compositions. The torrefaction thermochemical model described the thermochemical performance of poplar wood torrefaction processes. The results from the kinetic and thermochemical models for poplar wood torrefaction showed that (1) high temperature increases the evolution rate of torrefaction products, and favors the formation of torrefaction volatiles; (2) the heating rate has a slight effect on evolution for torrefaction process; (3) the mass and energy yields of torrefaction products are significantly influenced by both torrefaction temperature and residence time; (4) the heat of torrefaction reaction is mostly endothermic with a relatively small amount (less than 10% of the raw material energy content); (5) for the overall torrefaction processes, the sensible and latent energy of torrefaction products accounts for 5–18% of the total energy input and the remaining energy input transfers into the energy contents of torrefaction products. This work provides a theoretical guidance for future evaluation and optimization of woody biomass torrefaction systems/processes, and thereafter for the industrial application of woody biomass thermochemical conversion.