Modeling and Optimization of Grade Changes for Multistage Polyethylene Reactors

Publication type: 
Conference paper
Per-Ola Larsson, Johan Ã…kesson, Staffan Haugwitz, Niklas Andersson
Proc. of 18th World Congress of the International Federation of Automatic Control (IFAC)
<p>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.</p>