Investigation of Hydrodynamics, Kinetics, Energetic and Exergetic Aspects of Fluidized Bed Drying of Rough Rice

Abstract

Abstract The hydrodynamics, kinetics as well as energy and exergy analyses of fluidized bed drying of rough rice under various experimental conditions were investigated. Drying experiments were conducted at drying air temperatures of 55, 60, and 70°C, superficial fluidization velocities of 2.3, 2.5, and 2.8 m/s, solid holdups of 0.66 and 1.32 kg, and rough rice initial moisture content of 0.25 d.b. Various popular drying models were used to fit the drying data. It was found that the fluidized bed hydrodynamics of the rough rice was uniform and stable. The drying rate was found to increase with increase in drying air temperature and superficial fluidization velocity, while decreased with increase in solid holdup. Statistical analyses showed that the Midilli et al. model was the best model in describing fluidized bed drying characteristics of the rough rice. The results showed that the values of energy efficiency were higher than the corresponding values of exergy efficiency during the entire drying process. Furthermore, at initial stage of drying, the energy and exergy efficiencies were higher than those at the end of drying. It was also found that both the energy and the exergy efficiencies increased with increasing drying air temperature and solid holdup, whereas decreased with the increase in superficial fluidization velocity.