Abstract
Given the necessity of developing jatropha cultivation equipment, this work adjusted different mathematical models to experimental data obtained from the drying of jatropha seeds submitted to different drying conditions and selected the best model to describe the drying process. The experiment was carried out at the Federal Institute of Goiás - Rio Verde Campus. Seeds with initial moisture content of approximately 0.50 (kg water/kg dry matter) were dried in a forced air-ventilated oven, at temperatures of 45, 60, 75, 90 and 105°C to moisture content of 0.10 ± 0.005 (kg water/kg dry matter). The experimental data were adjusted to 11 mathematical models to represent the drying process of agricultural products. The models were compared using the coefficient of determination, chi-square test, relative mean error, estimated mean error and residual distribution. It was found that the increase in the air temperature caused a reduction in the drying time of seeds. The models Midilli and Two Terms were suitable to represent the drying process of Jatropha seeds and between them the use of the Midili model is recommended due to its greater simplicity.
Highlights
The growing world’s concern over environmental problems, along with the search for renewable energy sources has placed biodiesel in the spotlight of interest
The relative mean error, estimate of the standard deviation and the chi-square test for each model were calculated according to the following expressions: where: Y: Value observed in the experiment; Y : Value calculated by the model; n: Number of experimental observations; ÷2: Chi-square; SE: Standard deviation of the estimate P: Mean relative error; FD: Degrees of freedom of the model
It was found that the time needed for the jatropha seeds to reach the moisture content of 0.10 ± 0.005was 7.11, 3.90, 2,60; 1.79 and 1.26 h for the drying temperatures of 45, 60, 75, 90 and 105°C, respectively (Table 2)
Summary
The growing world’s concern over environmental problems, along with the search for renewable energy sources has placed biodiesel in the spotlight of interest. Reduction of seed moisture content is a complex process involving both heat and mass transfer, which can significantly modify product quality and physical properties depending on the method and conditions of drying (Resende et al, 2008). It is, essential to better understand this process to obtain efficient drying from the technical and economic standpoint. There are no indicatives for the phenomena of energy and water transportation inside the seeds These models consider that the drying process takes place only during the decreasing rate (Resende et al, 2009). Considering the advantages of biodiesel production and the importance of the drying process, this work adjusted different mathematical models to experimental data of drying jatropha seeds under different air conditions and selected the model that best represents the process
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