Conference Contribution

Modeling and Optimization of Grade Changes for Multistage Polyethylene Reactors

Per-Ola Larsson, Johan Åkesson, Staffan Haugwitz, Niklas Andersson


Grade changes in polyethylene reactors, i.e., changes of operating conditions, are performed on a regular basis to adapt to market demands. In this paper, a dynamic optimization procedure is presented built upon the Modelica language extended with Optimica constructs for formulation of optimization problems. A Modelica library for the Borstar R multistage
polyethylene reactors at Borealis AB, consisting of two slurry and one gas phase reactor, has been constructed. Using, a framework to translate dynamic optimization problems to NLP problems, optimal grade transitions between grades currently used at Borealis AB, can be calculated. Optimal inflows and grade key variables are shown.


optimization, reactor control, polymerization, chemical industry

In 18th IFAC World Congress, Milano, Italy, August 2011.

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