Modeling and control of rough rice drying in the spouted-bed
1991
Cho, Cho
In this study, the modeling of rough rice drying in a spouted-bed was investigated in order to control the drying operation in terms of the grain temperature. A spouted-bed dryer was designed and constructed by Paramalingam was used for carrying out the experiments, and its performance characteristics were evaluated. The grain temperature was considered most important variable and an attempt was made to control it using a simple thermostat controller to turn the air heater on and off depending upon the set grain temperature level. In first phase of experimentation, the drying experiments were carried out using inlet air heated to constant temperatures of 50, 60, 70, 80, and 90 deg C. The grain temperature and moisture content histories were determined. Empirical models for drying of rice in spouted-bed were developed in terms of fixed conditions of inlet air as well as bulk mean grain temperature. Both type of models estimated the spouted-bed drying of rice reasonably well. In second phase of study, it was shown that the thermostat operation enabled the control of grain temperature within reasonable limits. Drying experiments using grain temperatures of 40, 45, 50, and 55 deg C were conducted. It was possible to estimate the changes in moisture content of rice with the help of the developed models. It was observed that the head yield decreased abruptly after grain temperature reached a level of 40 deg C and above. This grain temperature limit was lower than the findings of conduction heating of rice most possibly due to the initial poor quality of rewetted rough rice.
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