Kinetics of Parboiled Paddy under Microwave Drying

Abstract

Microwave drying provides high heating rate and rapid moisture removal. The objective of this research was to investigate the effect of bed thickness and power levels on drying kinetics and to assess the quality of parboiled paddy under microwave drying. Effect of process variables, namely microwave power (180, 360, 540 and 720 W) and bed thickness (1.5, 3, 4.5 and 6 cm) were studied on drying rate, moisture ratio, moisture diffusivity and activation energy. Drying time significantly decreased with increase in power while increased with increasing bed thickness. Drying rate curves revealed that drying occurred only in falling rate period. The drying data  were fitted with several established thin layer drying models. Moisture diffusivity increased with increase in power and decreased with increase in bed thickness. The highest diffusivity of 30.8×10-10 m2/s was found at 720 W and 1.5 cm thickness while the lowest diffusivity of 3.08×10-10 m2/s was observed at 180 W and 6 cm thickness. The highest value of activation energy was found to be 7.718 W/g for 1.5 cm bed thickness whereas the lowest was 2.58 W/g for 6 cm bed thickness.