Drying kinetics of tobacco leaves and its thermodynamic properties

Abstract

Post harvest activities has the goal to prevent and minimize losses that occurs during commercialization of agricultural products, notability drying. The present work had the objective to determine the thermodynamic properties and evaluate the drying kinetics of tobacco leaves in different temperatures and air velocities of the drying air. Leaves were dried at air velocities of 0.5 and 1.0 m s-1 and temperatures of 40, 50, 60 and 70 oC. Five mathematical models usually used to represent the drying process of agricultural products were fitted to the experimental data. Results indicates that drying of tobacco leaves is dependent of velocity and temperature of the drying air, in which higher temperatures and air velocity leads to a lower time required to reach the equilibrium moisture content. The Modified Midilli model best represented the drying of tobacco leaves, according to statistical parameters. At a constant drying air velocity, enthalpy and entropy decreased along with increment of drying air temperature, whilst Gibbs free energy increases. Drying air velocity significantly impacts in the energy required for the process, in which increasing this parameter from 0.5 to 1.0 m s1, decreases the activation energy, from 63.65 to 55.22 kJ mol-1.