Heat and Mass Transfer on the Microwave Drying of Rough Rice Grains: An Experimental Analysis

This work aims to experimentally study the drying of agricultural products using microwaves, with particular reference to grains. Microwave drying experiments were carried out with paddy rice grains in natura (BRSMG Conai variety) for three levels of incident microwave power per mass of fresh grain (6.27, 14.63 and 22.99 W/g). Results of grain drying and heating kinetics are presented and analyzed. It was verified that the ideal average moisture content for grain storage and marketing, 15% (d.b.), occurred at 20 min (6.27 W/g), 13 min (14.63 W/g) and 7 min (22.99 W/g), and that the equilibrium moisture content of the samples reached 4.4%, 2.7% and 1.9%, at 310, 180 and 110 min, for each of the three power levels studied, respectively. The drying with the highest absorbed power caused discoloration of the grains at the end of the drying process.