Drying kinetics and effective water diffusivities in olive stone and olive-tree pruning

Abstract

Drying kinetics of olive stone and olive-tree pruning, two important biomasses from olive culture, was experimentally assessed at six different temperatures (from 343 K to 393 K) and four sample thicknesses (from 15 to 50 mm). Analysis of the drying curves revealed that Page's model was suitable for predicting the drying characteristics of both solid biofuels. From this analysis, two new mathematical equations to describe the dependence of moisture ratio with temperature and drying time were also proposed. The values of effective water diffusivity, calculated at the falling rate period by using Fick's second law of diffusion, increased when increasing drying temperature and sample thickness. Diffusivities for olivetree pruning (3.41 108 e 32.5 108 m2 /s) were almost twice higher than those for olive stone (1.87 108 e 16.4 108 m2 /s).