Study on Bin Circulating Drying

This study intends to simulate hopper bins with circulating elevators using layer-drying, logarithmic and non-equilibrium models. With the temporary bin, as used for cooling proposes, the system capacity can be enhanced by employing a two-stage drying. The hopper bin not only plays a role for the temporary storage of wet paddy, but can act as a slow dryer, thus increasing system capacity. Experiments were performed in labs and at the drying center of the Wo-Jei Farmers’ Association in 2004. The two-stage drying was undergone in a successful manner and, according to the results, the bin had a drying rate of 1% per day, which dried paddy of 25% down to 19% within 6 days under a hot air temperature of 50C.
In this study, four MATLAB programs has been developed and validated, namely, NTUDRY1, NTUDRY2, NTUDRY3 and NTUDRY4, which can simulate the stationary dryer, layer dryer, circulating and two-stage drying systems, respectively. With these, conclusions are drawn on the lab results: (a)The logarithmic model is fast and easy to predict the dry-zone in depth, so the circulating rate in a circulating bin can be determined, preventing power loss during operation. (b)The non-equilibrium model and layer drying method are helpful to solve the required airflow at different depths and predict the total drying time. (3) The airflow rate is decisive to the total drying time and plays a role to keep the uniformity of rice drying during the circulating process.