Drying kinetics of tobacco strips at different air temperatures and relative humidities

Abstract

The effects of air temperature and relative humidity (RH) on the drying kinetics of two kinds of flue-cured tobacco strips (C3F and B3F) were studied using a thermogravimetric device in this work. The drying experiments were carried out with drying air temperatures of 60, 70, 80, and 90 °C and RH values of 0, 10, 20, 30, and 40% at a constant airflow. Taking the effect of RH into consideration, a modified Arrhenius-type equation of diffusivity was proposed. In addition, comparing five thin-layer drying models and five equilibrium moisture content models to describe the drying kinetics and the desorption isotherms of tobacco strips, high coefficients of determination (R2) and low reduced Chi-square (χ2) and residual sum of squares (RSS) values indicated that the Logarithmic model and the Modified Oswin model appeared to be the most suitable for predicting the moisture ratio and the moisture desorption relationship of tobacco strips. The effective moisture diffusion coefficient under different temperatures and RHs ranged from 1.68 × 10−11 to 6.81 × 10−11 m2 s−1 for C3F and from 1.62 × 10−11 to 6.68 × 10−11 m2 s−1 for B3F. A modified Arrhenius-type equation with an RH term was found to be effective for describing the drying behavior of two flue-cured tobacco strips, and the activation energy (Ea) values were 34.6 and 35.2 kJ mol−1 for C3F and B3F, respectively.