Emerson Process Management’s advanced process control specialists have developed an Adaptive Model Predictive Controller (AMPC) that is optimizing production and improving profitability at SABIC Innovative Plastics’ Bergen op Zoom facility in The Netherlands, according to the companies. With a certain part of the process having long dead-times varying between six hours and 24 hours, standard advanced process control techniques were not effective.
SABIC Innovative Plastics, a manufacturer of plastics, produces a range of products including Lexan (a polycarbonate alternative) and Noryl (polyphenylene oxide) at its Bergen op Zoom plant. Historically, when setting up a specific set of batch processes, the runtime was calculated based on downstream demand, the available (interim) storage capacity, and the efficiency of the various processing facilities. Overcompensation either way meant that production progress tended to be either too fast or too slow, with less than optimal yields.
“We are constantly looking for improvement opportunities,” says Rein de Jonge, Global Advanced Manufacturing Systems Leader at SABIC. “We have known for some time that one of our processes presented a control challenge which was not easy to solve. We approached a number of automation suppliers and Emerson came up with what we believed to be the simplest and most elegant proposal.”
To address this problem, Emerson developed a physical model of the complete facility and implemented control methods based on the Smith Predictor -- a model-based control tool that can handle the dead-time phenomena of simple processes. The dynamic model was based on mass balance, integrating the variable dead-times of the SABIC process. Given the variable dead-time, traditional model correction control tools also proved insufficient and were replaced with adaptive Lambda tuning, thus obtaining the Adaptive Model Predictive Controller (AMPC).
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SABIC Americas Inc. is a CP 50 company. To view the SABIC profile, visit: http://www.chemicalprocessing.com/cp50/2008/sabic.html.
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