Application of the Capacity-Based Economic Approach to an Industrial-Scale Process

In a previous paper (Elliott, T. R.; Luyben, W. L. Ind. Eng. Chem. Res. 1995, 34 (11), 3907−3915) we outlined a generic methodology called the capacity-based economic approach that can be used to compare or screen preliminary plant designs by quantifying both steady-state economics and dynamic controllability. The method provides an analysis tool that explicitly considers variability in product quality. A simple reactor/stripper recycle system was used to demonstrate the method. A more complex ternary process with two recycle streams was studied in a subsequent paper (Elliott, T. R.; Luyben, W. L. Ind. Eng. Chem. Res. 1996, 35, 3470−3479). In this paper, we consider an even more complex process consisting of two reaction steps, three distillation columns, two recycle streams, and one purge/makeup stream. The essential contribution of this paper is to demonstrate that the capacity-based economic approach can be successfully applied to a large industrial-scale process. The system is described by approximately 750 ordinary differential equations and has 18 design and control degrees of freedom.