Design of Maize cob Dryer

Abstract

Drying is the most important unit operation in post-harvest handling of maize. Maize cobs are harvested at around 35% (w.b.) moisture content and shelling operation is performed at around 17% moisture content (w.b.). Shelled maize is further dried and traded at around 13% moisture content (w.b.). In humid climate, drying of cobs is prolonged which favors fungus growth and also severely affects the starch quality. Currently, Indian farmers practice sun drying method to dry corn cobs to optimum moisture content for shelling which has several disadvantages as it depended on weather conditions, time consuming, unhygienic etc. Further, due to high humidity in the coastal region and during monsoon or post monsoon season, drying of maize becomes a serious issue. At present there are no dryers available for drying of maize cobs, further, adoptability of grain dryers for the purpose is hindered by the physical and flow properties of maize cobs. The design of the proposed dryer includes the design of the dehumidification system with selection of efficient liquid desiccant for lowering the humidity of the drying air, thereby enabling drying at low temperature resulting in development of low thermal stress in maize kernels. The theoretical capacity of the dryer was calculated at 1.0 ton per batch considering the bulk density of cob to be 3 approx. 300 kg/m . Now, considering the initial moisture content of cob to be 35% and final moisture content of 17%, an air flow rate of 250 kg/min will be required to dry the cobs in 5 hours at drying air temperature of 45ÚC and 40% RH.