DRYING OF CORN USING VARIABLE MICROWAVE-POWER WITH A SURFACE-WAVE APPLICATOR

Drying kinetics of seed corn was studied under constant and variable microwave power operating modes. The absorbed microwave power levels were 0.25 W/g, 0.50 W/g, and 0.75 W/g of wet grain. Heated air at 30-degrees-C was used to carry moisture from the grain bed. For constant microwave power operation, the total drying time was reduced from 5.0 hr to 3.5 hr and 2.25 hr, respectively, when the absorbed power was increased from 0.25 W/g to 0.50 W/g and 0.75 W/g. However, after about 2 hr the drying rates fell to approximately the same level regardless of the absorbed power. The outgoing air temperature, an indicator of the grain temperature, increased with the increase in absorbed power. The germination of the corn dried at 0.25 W/g was 94% while it dropped to 53% and 44% respectively for 0.50 W/g and 0.75 W/g absorbed power. Bulk density of the corn dried at 0.25 W/g power was 0.735 g/cc and it was reduced to 0.712 g/cc and 0.706 g/cc respectively for 0.50 W/g and 0.75 W/g absorbed microwave power. Variable microwave power operation with proper combinations of power level and duration reduced the energy loss through outgoing air. Corn quality was affected by both the magnitude and the period of microwave power application.