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Optimum Operation Parameters of the Combination of a Mixed-flow Dryer and Continuous In-bin Aeration for Paddy Under Malaysian Conditions
Dissertation Abstract:
The design of a mechanical paddy dryer or any improvement of the dryer can be successfully done by incorporating all significant variables concerned in its operation through an optimization model. All constraints should satisfy local requirements and suitabilities.
This study determined the optimum parameters for the operation of a mixed-flow paddy dryer followed by continuous in-bin aeration. The aeration was provided to enhance the mixed-flow dryer operation. The optimization study was done by incorporating the working parameters of each operation in two separate empirical nonlinear optimization models. The two models were associated in such a way that the optimum results of the mixed-flow drying were the inputs to the aeration stage, and vice versa.
A computer simulat ion program was used to obtain all pertinent information for each operation before developing the optimization model. The mixed-flow dry ing simulation program was modified to enable it to simulate paddy drying under local conditions so that it can be used to evaluate the performance of an existing mixed-flow dryer. The simulated results of this program agreed reasonably well with the actual tests conducted on the dryer.
The optimum result showed th at only two passes of the dryer operation and one period of the in-bin aeration were required to dry fresh wet paddy from a moisture conte nt of 30.50 to about 16.00 percent dry basis. Different optimum drying air temperature and airflow rate were obtai ned from each drying pass. The val ues of 70.48°C and 10.00 kg/m2 min, respectively, were the optimum drying ai r temperature and airflow rate of the fi rst drying pass. For the second pass, the optimum drying a ir temperature was 77.05°C and ai rflow rate was 5 kg/m2 min. An optimum aeration period of 32.31 hours with airflow rate of 0.77 m3/mt min was required following the first drying pass. Grain germination of 94.71 percent and dry matter loss of 0.6 percent were the optimum grain quality criteria obtained from the study. An average specific energy requirement of 5.13 MJ/kg of water removed at the net grain output capacity of 6.88 mt/hr were recorded for th e optimum conditions.
Compared with the status of current operation, the optimum result obtained showed some potential toward improving the existing mixed-flow paddy drying and eventually, the d ryi ng capacity of the rice complex.