Modeling and control of a mixed-flow rice dryer with emphasis on breakage quality

The rice kernel is modelled as a two water compartment system and as a whol e concerning heat and quality. The external transfers are governed by Fick and Fourier laws. The compartmental approach is mainly used to render the i nternal resistance in the most efficient way on the computer. Mass transfer coefficients were adjusted with the help of constant condition drying kine tics. A primary validation of the model was observed when compared to exper imental kinetics with transient phenomena. A secondary validation was done at the thick layer level. A simple PI controller with system linearization was designed and rested on the simulator. The latest results concern the si mulation of a large scale semi-industrial dryer for both steady and transie nt states. The controller was tested successfully on the simulator. Results have shown a robust behaviour for such a non-linear system. On the other h and, performance is highly dependant upon the dryer setpoint. Previous work on corn dryers has shown that improving this performance wasn't realistic for practical reasons (e.g. lack of knowledge about the zeros of the system ). The resulting model, in its two (steady and transient state) versions, i s available as a cross-platform software and also on internet. The validity range for the model is 15-80 Celsius, 0-100% HR and 0-1 mis. (C) 2001 Else vier Science Ltd. All rights reserved.