Effect of Bed Thickness on the Drying Rate of Paddy Rice in an Up-flow Fixed Bed Dryer

Abstract

Rice has played its important role as the world’s major source of food for human and animals. In order to sustain the food supply, many efforts have been conducted to increase the production of paddy rice per acre. The management of highly moist paddy rice during the harvesting period for preserving the paddy rice quality, increase in yield and reduce postharvest losses is greatly challenging. Drying process is one of the postharvest technologies for preserving the quality and extending the storage time of paddy rice. Moisture is removed to retard the development of a favorable environment for growth of molds and insects that lead to cause spoilage. In this paper, an experimental work and development of a simple mathematical model in a fixed bed drying of highly moist paddy rice have been conducted. Effect of bed thickness (6 cm to 12 cm) on the paddy rice drying rate was investigated by flowing drying air at 5.5 m/s with 37.45 % relative humidity at 40°C for 10 to 130 minutes. Drying of paddy rice using 8 cm bed thickness for 60 minutes was found to be the best drying condition to obtain acceptable moisture content of paddy rice for safe storage. The proposed non-equilibrium has shown its suitability for predicting the moisture content of paddy rice with variation of height of a fixed bed under unsteady state conditions. The drying rate constant was found to be a logarithmic function of bed thickness.