Optimal Design of Flexible & Reliable Process Systems

Summary & Conclusions - In design & operation of chemical process systems, two categories of uncertainty are important: 1) realization of continuous process parameters (product demands, feedstock qualities, reaction kinetics), and 2) discrete states (typically related to equipment availability). This paper presents a general framework for incorporating both types of uncertainty in process system design. A combined flexibility-reliability index (FRI) is introduced to measure the capability of a process system to cope simultaneously with 1) (stochastic) parameter variations, and 2) equipment failures, by explicitly accounting for process operational interactions & constraints. A design optimization procedure is then proposed for obtaining flexible, reliable process systems at minimum investment cost and maximum average profit; the potential inclusion of maintenance considerations is briefly discussed.