Maize (Zea mays L.) is one of the most important nutritious grains which have high moisture content during harvest. Moisture content of 24-25% (db) at the harvest has to be reduced below 14% (db) to prevent its deterioration during storage. Drying process is generally performed by forced convection by heating ambient air and blowing it over grains to be dried. The aim of heating the air at certain temperature is to reduce the relative humidity of the air, which has a positive effect on the drying potential. In this study, drying behaviour of thin layer of maize for different drying air temperatures (40, 50, 60 and 70°C) and different air flow rates (20, 30 and 40) studied. The result shows that drying temperature has significant influence on a drying rate. With the increase in drying temperature drying rate increased. The moisture ratio reduced sharply up to 25 minutes of drying time, after that it decreased with drying time but at slower rate. In the beginning of the drying process, moisture transfer took place at faster rate than later. The effect of air flow rate on moisture content was found to be negligible except at the phase of drying. The analysis also illustrated that the drying of maize grains occurred during the falling rate period and no constant rate period was observed in this study. The drying rate constant was found to increase with increas in air temperature and was maximum for a combination of 700C air temperature and 40 air flow rate.

Harvested grain mass contains various impurities that need to be removed before further processing. A solar powered screen cleaner was designed, fabricated and tested for separating impurities from soybean, lentil and chickpea grains. The machine consists of frame, feeding chute, screen cradle, discharge outlets, and drive unit. The angle of tilt of the sieve was varied between 3 and 8° while the hanger angle was maintained at 5°. Operating parameters such as screen cradle angle, oscillation and feed rate were optimized and the optimum performance was achieved at a screen cradle angle of 50, screen oscillation of 3.6 Hz, and feed rate of 150 kg/h.The slope of the sieve unit, cradle speed and stroke length could be adjusted easily. The developed unit was evaluated with 5 kg sample consisting of 80%, 85%, and 90% pure hand-cleaned grains mixed with 20%,15% and 10% impurities (chaff, stem, other crop seeds, weed seeds, clods, stones, etc.). The cleaning efficiency for whole chickpea, soybean and lentil was found to be 88.27%, 87.14% and 84.3%, respectively, and the losses observed was 2.12%, 1.25% and 1.73%, respectively. Overall machine efficiency was observed to be 83%.This machine assures good quality grain at affordable energycost to small and marginal farmers in rural India.