A complete dynamic model for the thermal processing of bioproducts in batch units and its application to controller design

In this paper, we present the development and experimental validation of a dynamic model, based on first principles, for the thermal processing of bioproducts in steam retorts. The dynamic variability exhibited in the experiments is explained on the basis of nonlinear flow relations in the input and output streams and its coupling. The performance of the model in simulating several experimental situations proved its validity over a wide range of operating conditions. The utility of the model must be understood in the context of testing and designing efficient control structures. Two examples will illustrate this fact: first, the model is employed to tune PID-type controllers by IMC techniques to control pressure and temperature in the sterilization cycle. The performance of the control configuration will be discussed and their limitations analysed on the basis of the dynamic model. In the second example, the model will be employed to design multivariable nonlinear model-based controllers for the control of pressure and level during the cooling stage. Its performance and robustness will be tested on simulation.

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