Evaluation of the Performance of a Custom-Made Fluidized Bed Drying System

Abstract

Abstract. Laboratory and farm-scale fluidized bed dryers are not available to purchase. Additionally, a deliberation is presently continuing regarding the beneficial and damaging effects of drying grain in a fluidized bed. Therefore, the goal of this research was to develop and test a custom-made small-scale fluidized bed dryer, suitable for moderate farms and capable of drying small and large size grains from high moisture content to a safe storage moisture content. The customary fluidized bed dryer was developed and constructed in the Rice Research and Extension Center, Stuttgart, Arkansas. The fluidized bed dryer was used to dry wheat from an initial moisture content of 23.3% db. The effects of the aspect ratio (bed height to bed diameter ratio) of 2, 3, and 4 m/m, the furnace temperature of no heat, 100°C, 150°C, and 200°C and drying duration of 10, 20, 30, 40, 50, and 60 min on the wheat moisture content, drying rate, and dryer efficiency were investigated. The lowest wheat moisture content of 16.3% db was observed at the lowest aspect ratio of 2 m/m, the highest furnace temperature of 200°C, and the longest drying duration of 60 min. Conversely, the highest wheat moisture content of 19.0% db was observed at the highest aspect ratio of 4 m/m, and the no heat condition. The drying rate of 0.47%/min was observed at the lowest aspect ratio of 2 m/m and the furnace temperature of 200°C after 10 min. The maximum dryer efficiency of 63.2% was achieved at the aspect ratio of 4 m/m, the furnace temperature of 200°C. Two empirical models were developed to predict the moisture content of wheat and the dryer efficiency as affected by the aspect ratio, the furnace temperature and the drying duration with the adjusted coefficient of determination of 0.91 and 0.88, respectively. Although, the developed fluidized bed dryer is a lab-scale system, the experimental results provided an exceptional indication to scale up the drying system to dry grains. Keywords: Dryer efficiency, Drying rate, Fluidized bed, Moisture content, Wheat-drying.