Drying kinetics of olive stone: A valuable source of biomass obtained in the olive oil extraction

Olive stone is a by-product of the olive grove especially suitable for thermal purpose in industrial, residential and home. To avoid maintenance problems in boilers and to increase the combustion efficiency, olive stone needs to be dried to moisture equilibrium, about 8% (wet basis). The thin layer drying kinetics was investigated in a drying tunnel. Isothermal drying tests were performed with different drying air temperatures: 100, 150, 200 and 250 °C for each sample thickness: 10, 20 and 30 mm. Drying curves were analyzed from the different mathematical models studied by the researchers to date. A new mathematical model is proposed in this work, Two Term Gaussian, which presents the best results of fit. The drying rate is calculated and analyzed. The effective diffusivity values range from 3.98·10−9 to 5.97·10−8 m2/s. Furthermore, the activation energies values were 14,208, 15,356 and 16,270 J/mol for each sample thickness: 10, 20 and 30 mm, respectively.