Drying kinetics and mathematical modelling of Arundo donax L. canes, a potential renewable fuel

Abstract

Arundo donax L. is an energy crop with the potential use as a renewable fuel. This study focused on the drying process of the canes in field and laboratory conditions to determine the effect of the harvest conditioning on the kinetics parameters of whole and slashed canes. The lab drying test was conducted in a thin layer dryer at temperatures between 30 and 80 °C and a 0.5 m·s<sup>–1</sup> air velocity. The whole and slashed canes showed faster water evaporation rates as the temperature increased, but the slashed canes achieved a lower final moisture content in a shorter time. The effective diffusion coefficient varied between 3.67 × 10<sup>–12</sup> and 1.28 × 10<sup>–11</sup> m<sup>2</sup>·s<sup>–1</sup> and showed a significant effect of the temperature, but not between samples; its temperature dependence was determined by the Arrhenius equation giving activation energies of 24.4 and 20.2 kJ·mol<sup>–1</sup> for the whole and slashed canes respectively, not significantly different. The modelling of the experimental drying data to six thin layer drying models achieved good performance (R<sup>2</sup> > 95.9%), although the Logarithmic model showed the best fit for both samples (R<sup>2</sup> > 99.4%). In addition, a temperature dependent equation for the drying constant was included in the Logarithmic model for the whole and slashed canes which predicted with good performance (R<sup>2</sup> > 97%) the moisture loss. The developed tools constitute an adequate model for the simulation of the drying process of Arundo donax L. that could be useful for the design of various equipment and systems.