A design procedure for advanced process controllers utilising first principles steady state and dynamic models as an alternative to empirical models identified from plant tests is presented.

The procedure is illustrated on the challenging control problem posed by the propylene/propane splitter at Scanraff refinery in Lysekil, Sweden. In this unit, a classical control design procedure based on plant step tests is not feasible. It is demonstrated that a workable control strategy that satisfied the control objectives for the splitter could be developed, without the need for any step tests on the live plant whatsoever.

This is a highly illustrative example of how dynamic simulation has progressed from an academic discipline to an industrial setting in which economic benefits can be justifiably claimed. In this case, HYSYS® from Aspentech was chosen as the steady state and dynamic simulation tool because of its acceptance within Scanraff, ability to quickly create a dynamic model and the integration of the Aspentech DMCplus® multivariable controller.