Modelagem com difusividade efetiva variável via analogia da lei de Fick para a secagem de sementes de Jacaranda mimosifolia em camada delgada

Abstract

Jacaranda mimosifolia seeds have been studied for different applications due to the composition of their extracts. In addition to having noble wood with high commercial value, it has potential applications in anti-inflammatory remedies, skin treatments and inhibition of cancer cells. Considering this, the objective of this work was to determine the physical characteristics of the seeds and the porous medium formed by them, to determine the desorption isotherms, and to analyze the drying kinetics of Jacaranda mimosifolia seeds in a thin layer. The desorption isotherms were determined by static-gravimetric method and adjusted using the GAB model for temperatures of 20°C, 30°C and 40°C. The modeling of the drying process was performed by an analytical solution of the analogy of the Second Fick's Law, considering humidity effective diffusivity constant. For variable diffusivity, a partial and sequential adjustment technique of the classic analytical solution was proposed. Thin layer drying kinetics were conducted at temperatures of 40°C and 50°C. From the results obtained from the physical characterization, it was possible to determine relevant properties of the seed and bed, also verify that the particle has similar shape and sizes, and forms beds of high porosity. From the adjustment obtained for the desorption isotherms, it was possible to determine the model’s parameters with R2≥0.99 and conclude that, the seed has an unconventional behavior. Regarding drying, the adjustments with constant parameter showed R²≥0.983 and χ²≤1.60x10-3, while with variable parameter R²≥0.998 and χ²≤1.40x10-4, demonstrating the improvement obtained in the randomness of the residues. The proposed sequential adjustment method showed good results, detailing diffusive mass transfer mechanisms and showing promise for application in process control and product quality, in addition to projecting and dimensioning dryers.