Parameter Selection in the Parameter Estimation of Grade Transitions in a Polyethylene Plant

Niklas Andersson, Per-Ola Larsson, Johan Åkesson, Niclas Carlsson, Staffan Skålén, Bernt Nilsson


A polyethylene plant at Borealis AB is modelled in the Modelica language and considered for parameter estimations at grade transitions. Parameters have been estimated for both the steady-state and the dynamic case using the platform, which offers tools for steady-state parameter estimation and supports simulation with parameter sensitivies. The model contains 31 candidate parameters, giving a huge amount of possible parameter combinations. The best parameter sets have been chosen using a parameter-selection algorithm that identified parameter sets with poor numerical properties. The parameter-selection algorithm reduces the number of parameter sets that is necessary to explore. The steady-state differs from the dynamic case with respect to parameter selection. Validations of the parameter estimations in the dynamic case show a significant reduction in an objective value used to evaluate the quality of the solution from that of the nominal reference, where the nominal parameter values are used.

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Studies in Engineering and Technology   ISSN 2330-2038 (Print)   ISSN 2330-2046 (Online)

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