Plant-wide Control: Methodologies, Applications and Performance Assessment

Abstract

Plant-wide control (PWC) methodologies are important given the increasing degree of integration in chemical processes due to material recycle, energy integration and stringent product quality requirements. All these, though economically favourable, pose challenges to smooth plant operation making it difficult to design PWC systems with good dynamic performance. The present study addresses several important issues in PWC methodologies. PWC methodologies and applications are reviewed. Improvements to the restraining number procedure for control degrees of freedom are proposed. Steady-state and dynamic simulation models of the styrene process are developed. Three different PWC procedures are applied to develop alternative control structures whose performance is compared. A new economic performance measure based on production rate is proposed, and results from selected reactor-separator-recycle studies are applied to integrated processes to study their usefulness and develop guidelines for PWC. Finally, a new PWC methodology incorporating optimization besides heuristics and simulation is proposed.