Kinetics and mathematical modeling of drying of parboiled paddy in a packed bed dryer

Abstract

Drying characteristics of 2 types of parboiled paddy (“Nadu” & “Samba”) was investigated in a packed bed dryer. Drying experiments for both paddy types were carried out at three different hot air temperatures 35oC, 45oC and 55oC by keeping constants hot air flow velocity and bed height as 5.8 m/s and 15 cm respectively. Moisture content was measured at different time intervals. Experimental results were fitted to three thin layer drying models; Midilli et. al., Weibull et. al. and Page. Statistical indicator; Root mean square error (RMSE) showed Midilli et. al., Weibull et. al. models give better fit to the experimental values. The absence of the constant drying rate period in drying curves show the drying of parboiled paddy lies totally in the falling rate period where the drying rate is controlled by the moisture diffusion. Maximum drying rates were observed for both paddies. Effective moisture diffusivity values were calculated for different temperatures. The Activation energy of “Nadu” and “Samba” are calculated based on the Arrhenius equation are 33389.024 J/mol and 16776 J/mol respectively.