Several troubleshooting cases involving operating issues with a de-propanizer de-butanizer twin tower process (Woods, 2006) were simulated in HYSYS and implemented on an industrial DCS system. The towers, equipment and instrumentation were modeled dynamically and connected to an industrial DCS system using the OPC protocol. A commercial multivariable controller was installed to determine the optimal operation and to expose the students to the modern manufacturing environment. An evaluation (test) and student satisfaction surveys were conducted following the class exercises.
Two DCS-based cases were provided as exercises to an Advanced Analysis class following application of similar paper-based "triad" troubleshooting exercises as described by Woods. The DCS-based troubleshooting cases included operating problems caused by (1) high overhead cooling water temperature, (2) a reflux block valve left partially closed following maintenance activities. The first DCS-based troubleshooting case was also used as the basis of a “DCS troubleshooting competition” held at the Southwest Region student AIChE conference at Lamar University, March 26-28, 2010.
A feed forward controller was configured and tuned for the de-propanizer tower without a multivariable controller. The feedforward controller was demonstrated in a Process Control II class where students made a disturbance move (10,000 lb/hr feed change) to observe the controller in action in real time. A performance comparison between the feedforward plus feedback controller and the feedback only controller was shown to the students. During the DCS demonstration, historical closed-loop tuning records were displayed to illustrate the online feedforward controller tuning procedure. Students were exposed to the feedforward tuning procedure and the effect of feedforward parameter changes on the controller performance.
Woods, D.R., Successful Trouble Shooting for Process Engineers, WILEY-VCH Verlag GmbH & Co., Weinheim (2006).
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