Comparing corn drying in fluidized bed dryer and convective tray dryer

Abstract

In this study, the thin layer drying characteristics of corn were experimentally investigated in a fluidized bed dryer and a convective tray dryer. Corn with an initial moisture content of 25 % dry basis was used in the experiments. Experiments were performed at three different drying temperatures: 55, 65, and 75 °C. In each experiment one layer of corn was inserted into the dryer and then drying was performed for 90 min. The drying air velocities were set to 0.45 m/s for the convective tray dryer and 2.5 m/s for the fluidized bed dryer. Single exponential and Page models were fitted onto the measured drying data. Effective diffusivities were calculated using Fick’s first law. The equilibrium moisture contents were evaluated using the Guggenheim-Andersen-de Boer model. From the experiments it was observed that drying rates in the fluidized bed dryer were considerably higher than drying rates in the convective tray dryer. Effective diffusion coefficients obtained in the fluidized bed dryer were approximately 70 % higher than those in the convective tray dryer. This increase is mainly attributed to the homogeneous mixing motions in the fluidized bed dryer, which enhances heat and mass transfer between the corn and the drying air. In addition, the temperature dependence of the effective diffusion coefficients was described by an Arrhenius-type relationship.