Performance, Energy, and Product Quality Aspects of a Modified Pneumatic Dryer for Rapid Drying of High-Moisture Paddy

Abstract

The application of surface roughness on the drying column was combined with a multipass drying concept (first-pass and second-pass drying) to improve the performance and energy utilization of a conventional pneumatic dryer during rapid drying of high-moisture paddy. The surface roughness on the drying column was characterized by the ratio of the corrugated surface length (C) to the total length (L) of the column (i.e., C/L). The effects of drying temperature (120°C, 150°C, and 180°C) and C/L value (0, 0.5, and 1.0) on the dryer performance, energy utilization of the drying process, and rice milling quality were determined. The drying column with a higher C/L value had higher potential for improving the dryer performance and energy utilization of the drying process. For first-pass drying, a drying column with C/L values of 0.5 and 1.0 could reduce energy consumption by 14% to 17% and by 41% to 44%, respectively, compared with a column without a corrugated surface (C/L = 0). However, for second-pass drying, the drying system that used a drying column with a corrugated surface consumed more energy. The moisture content reduction of paddy could also be significantly increased after second-pass drying. For both first-pass and second-pass drying, a higher drying temperature and higher C/L value resulted in a lower head rice yield from the milled rice, while the effects of drying temperature and C/L value on the whiteness value of the milled rice were found to be insignificant.HighlightsCharacteristics of the drying column had more significant effects on the dryer performance and energy utilization than the drying temperature.A drying column with C/L = 1 (totally corrugated surface) showed significant potential for increasing the dryer performance and energy utilization of the drying process.A drying column with a higher C/L value may not be necessary for paddy with a small amount of surface moisture.Multipass drying of paddy using a pneumatic dryer is not suggested due to the significant reduction in head rice yield. Keywords: Drying column, Energy utilization, Milling quality, Multipass drying, Pneumatic dryer, Surface roughness.