Development and evaluation of solar rotary dryer for powder drying

A forced circulation solar rotary dryer for drying wet Di-calcium phosphate (DCP) has been developed. Before drying wet DCP in rotary dryer, it was pre-dried in open sun with the help of hand operated shuffling device because rotary dryer cannot be used for DCP having moisture content more than 35% (w.b.). During pre-drying, the moisture content of DCP reduced from 53% to 34.7% (w.b.) in two drying days. The final drying was carried out in solar rotary dryer. The drying air at a flow rate of 0.022 m³/s and temperature of 60±1°C was supplied to the rotary drum. The moisture content of DCP was reduced from 34.7% to 9.3% (w.b.) in rotary dryer in two drying days. The reduction in moisture content of DCP was from 53% to 9.3% (w.b.) in four drying days when DCP was dried in two stages viz. pre-drying in open sun and final drying in rotary dryer. In comparison, in open sun drying, the moisture content of DCP reduced from 53% to 28.5% (w.b.) and 53% to 26.2% (w.b.) without shuffling and with manual shuffling respectively, in six drying days.