Economic plantwide control: Automated controlled variable selection for a reactor-separator-recycle process

A systematic plantwide control design procedure was proposed in [Skogestad, 2000]. The main goal of this procedure is, to design an optimal control structure for a complete chemical plant based on steady state plant economics, also known as economic plantwide control. In this work, we automated a key step of this procedure, which is the selection of controlled variables, based on quantitative local methods. We applied the economic plantwide control design procedure to a typical chemical plant process, which consists of a reactor, a separator and a recycle stream with purge. We evaluated the economic performance of the designed control structures for various disturbances and found that, although the automatic selection of the controlled variables was based on local methods, the control structures performed quite well, even for large disturbances.