Fluidized Bed Drying of Large Particles

Abstract

Batch drying of red spring wheat in a fluidized bed was performed. Effects of bed height, gas velocity, initial moisture content and air temperature on drying rate were investigated. Wheat was conditioned to simulate high moisture contents just after harvest. Heated air was the medium for moisture removal with thermocouples located along the height of the freeboard recording bed temperatures. Samples were removed at regular intervals during drying and their moisture contents determined. It was found that the rate of moisture removal was controlled by the internal rate of diffusion and hence slugging had no effect on the drying rate. The temperature distribution within the bed was uniform due to the high degree of mixing that occurs as wall slugs are formed with wheat. At lower bed temperatures the rate of drying slowed considerably. Drying times were considerably shorter than other drying apparatus.