Experimental analysis of low-temperature grain drying performance of vertical packed clay and clay-additives composite desiccant beds

A laboratory model of a forced circulation desiccant based green pea drying system operating in an open-loop is constructed and tested. The green pea drying process is divided into two stages involving dehumidification by the desiccant bed and green peas drying by dehumidified process air. Removal of moisture from the process air has been achieved by vertical packed composite desiccant beds. The composite desiccant used are heat treated clay with CaCl2 being impregnated and clay with additives like horse dung and sawdust, again being heated, treated and later impregnated with CaCl2. The green peas were dried for a process time of one hour. The drying was quite sharp during the initial process time of 500 s and from then onwards proceeded at a constant rate. For the identical bed masses, The performance of heat treated clay-additives based beds in moisture reduction and enhancement in enthalpy of process air is higher. The experimental study reveals the average heat content of air entering the dryer is 1.46, 2.46 and 2.38 kJ for heat-treated clay-CaCl2, clay-horse dung-CaCl2 and clay-sawdust-CaCl2 composite desiccant beds of 700 g mass.