Simultaneous tuning of multiple control loops for an unstable crystallizer employing a robust design approach

In this paper, a parametrically robust design methodology [MM05] is applied to the problem of tuning all control loops of an oscillatory continuous crystallizer. The adopted approach guarantees an optimum performance of the process in the presence of parametric uncertainties. With the obtained controller tuning the startup time of the process is halved and disturbance attenuation is largely improved. Moreover, the closed-loop process can be operated at conditions, where the open-loop process is unstable. Consequently, the operating region is enlarged and process safety is increased.