Dynamic modeling and computer control of a retort for thermal processing

Abstract The process dynamics and evaluation of analog pneumatic control and digital control of a batch retort were studied. Sensor dynamics of the analog controller resulted in poor control for arbitrary set-point tracking of the retort temperature. The retort dynamics were determined to be nonlinear in terms of the process gain, and time constant for changes in the steam supply input. A model was developed to describe this behavior and a digital proportional-integral controller was designed from simulation studies. This controller, with an anti-windup feature, was an excellent controller for regulation of the retort temperature to within ± 0.1 °C. It was also shown that to maintain this level of control the controller parameters need to be scheduled according to steam supply conditions and processing set-point.

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