Mathematical modelling of the drying kinetics of Jatropha curcas L. seeds

Abstract

Jatropha (Jatropha curcas L) seed contains non-edible oil, which is suitable for biodiesel production. The present research focused on the mathematical modelling of the drying kinetics of Jatropha seeds at a storage moisture content. The non-pretreated seeds (whole seeds) and pretreated seeds (crushed seeds) were dried at five different air temperatures (313, 323, 333, 343 and 353 K) in a standard heating furnace. The moisture loss from the seeds was systematically recorded, converted to moisture ratio, and fitted to four semi-theoretical drying mathematical models: Lewis, Henderson and Pabis, Page and Avhad and Marchetti models. The fitness of the models were compared using the coefficient of determination (R2), chi-square test (X2), root mean square error (RMSE), mean bias error (MBE), and mean absolute error (MAE). It was found that an increase in the air temperature caused a reduction in the drying time of both the whole and crushed seeds. From the tested models, the Avhad and Marchetti model showed the best fitting to the experimental data with R2 varied from 0.9914 to 0.9969 and 0.9908 to 0.9917 for all tested temperatures for the whole seeds and crushed sees of Jatropha, respectively. The Avhad and Marchetti mode showed superior fit to the experimental data at the drying temperature of 313 K with R2 of 0.9969 for the whole seed, and at 333 K in case of crushed seeds for which the R2 value was 0.9917. The activation energy values of 33.53 and 32.885 KJ mol−1were obtained for the whole and crushed seeds, respectively when the best-fitted model was used.