Optimisation of Grade Transitions in an Industrial Gas-Phase Olefin Polymerization Fluidized Bed Reactor Via NCO Tracking
| Authors: | Chatzidoukas Christos, Aristotle University of Thessaloniki & Chemical Process Engineering Research Institute, Thessaloniki, Greece
Kiparissides Costas, Aristotle University of Thessaloniki & Chemical Process Engineering Research Institute, Thessaloniki, Greece
Srinivasan Bala, École Polytechnique Fédérale de Lausanne, Switzerland
Bonvin Dominique, École Polytechnique Fédérale de Lausanne, Switzerland |
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| Topic: | 6.1 Chemical Process Control |
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| Session: | Knowledge Driven Batch Processes |
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| Keywords: | Adaptation technique, on-line optimal control, optimality conditions, polymerization, polyolefin production, grade transition |
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Abstract
Gas-phase olefin polymerization fluidized-bed reactors are complex processes that are characterized by large time constants and slow transitions. Optimal grade changes can be computed off-line on the basis of a detailed process model and applied to the process in an open-loop mode. However, the presence of uncertainties makes this approach clearly non-optimal. Fortunately, measurements can be used to improve the situation; this can be done either explicitly via process model refinement and repeated optimisation, or implicitly via direct input adjustment. This work considers the optimisation of grade-transition changes by enforcing on-line the necessary conditions of optimality (NCO tracking) using available measurements. The key steps are the generation of an adjustable model of the optimal solution and its adaptation using appropriate measurements/estimates of the controlled variables.
