Cross-flow thin bed drying characteristics of maize (Zea mays) using continuous sample weight measurement

Abstract

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.