Design and development of a conduction drier for accelerated drying of peanuts

Abstract

A rotary conduction drier using sand as the heating medium was designed and developed for accelerated drying of high moisture peanuts. The performance characteristics of the drier were evaluated in terms of peanut quality and drying time. Drying characteristics of peanuts at different drying conditions were also studied. The effect of varying the operating conditions was investigated to determine the optimum operating conditions of the system and these were compared to conventional (sun) and convection (oven) drying methods. Results revealed that quality indexes of peanuts, i.e. % breakage, % shiriveled and flavor were greatly dependent on the operating conditions of the drier. The optimum quality indexes were obtained at a drying temperature of 70°C, a feed rate of 7 kg/min and a rotational speed of 8 rpm. Drying characteristics of peanuts in the drier followed an exponential model. The drying time required to reduce moisture content to 10% wet basis for safe storage was significantly shorter in the developed unit than in conventional and convection drying methods. On the other hand, the quality indexes of peanuts dried in the experimental drier were comparable with conventional and convection drying methods at lower temperatures, although lower quality indexes were observed at higher temperatures. The results indicated that kernel temperature during conduction drying should not exceed 40°C in order to produce good quality dried peanuts.