ASABE Technical Library - Abstract

Abstract. There is a critical need to determine conditions that ensure successful natural or slightly-heated air, in-bin drying of rough rice with the least impact on quality. The objective of this study was to determine natural or slightly-heated air, in-bin drying strategies that minimize rice quality changes. In-bin drying of rough rice was simulated for Arkansas conditions and locations, using a twenty-year weather data (1995 to 2014), and different fan control strategies. The fan control strategies comprised of running the drying fan continuously, only at night, only at day, and at set windows of natural air equilibrium moisture content (EMC-controlled natural air) and EMC window with supplemental heating option (EMC-controlled SAVH). Drying simulations were performed at air flowrates of 0.55, 1.10, 1.65, and 2.20 m³ min-t^-1, drying-start dates of August 15^th, September 15^th and October 15^th, and rough rice initial moisture content of 16% to 22%. Drying duration, dry matter loss, overdrying rate, and fan run time were determined. For each of the fan control strategy, rough rice at the highest IMC of 22% required the longest drying duration, and vice versa for IMC at 16%. Using EMC-controlled SAVH strategy resulted in the shortest drying durations. The controlled strategies generally minimized the range of maximum and minimum MCs of rough rice inside the bins. The greater air flowrates were associated with higher overdrying rate and lower dry matter losses. At air flowrate of 0.56 m³min-t^-1, all of the studied fan control strategies resulted in average dry matter losses exceeding 0.5%. As the air flowrate increased, the required fan running time for drying rough rice also reduced. Running the fan only at night required the longest fan running time. EMC-controlled natural air or the EMC-controlled SAVH drying required nearly the same fan run time, but the latter shortened drying duration calendar-wise. The study provided useful information which guide rice producers to minimize deterioration of rice quality during on-farm, in-bin drying.