Abstract:
The reaction kinetics of solid fuel is a critical aspect of energy
production because its energy component is determined during the process.
The overall fuel quality is also evaluated to account for a defined energy need.
In this study, a two-step first-order reaction mechanism was used to model the
rapid mass loss of pine sawdust (PSD) during torrefaction using a
thermogravimetric analyzer (Q600 SDT). The kinetic analysis was carried
in a MATLAB environment using MATLAB R2020b software. Five
temperature regimes including 220, 240, 260, 280, and 300 °C and a
retention time of 2 h were used to study the mechanism of the solid fuel
reaction. Similarly, a combined demarcation time (i.e., estimating the time
that demarcates the first stage and the second stage) and iteration technique
was used to determine the actual kinetic parameters describing the fuel’s mass
loss during the torrefaction process. The fuel’s kinetic parameters were
estimated, while the developed kinetic model for the process was validated
using the experimental data. The solid and gas distributions of the components in the reaction mechanism were also reported. The
first stage of the degradation process was characterized by the rapid mass loss evident at the start of the torrefaction process. In
contrast, the second stage was characterized by the slower mass loss phase, which follows the first stage. The activation energies for
the first and second stages were 10.29 and 141.28 kJ/mol, respectively, to form the solids. The developed model was reliable in
predicting the mass loss of the PSD. The biochar produced from the torrefaction process contained high amounts of the
intermediate product that may benefit energy production. However, the final biochar formed at the end of the process increased with
the increase in torrefaction severity (i.e., increase in temperature and time).