A strategy for MINLP synthesis of flexible and operable processes

This paper presents a sequential two-stage strategy for the stochastic synthesis of chemical processes in which flexibility and ability to adjust manipulated variables are taken into account. In the first stage, the optimal flexible structure and optimal oversizing of the process units are determined in order to assure feasibility of design for a fixed degree of flexibility. The feasibility is assured by simultaneous consideration of critical vertices while the expected value of the objective function is approximated by the optimization at the base point. The latter is determined by a simple set-up procedure based on the calculations of the objective function’s conditional expectations for uncertain parameters. In the second stage, the structural alternatives are included in the mathematical model in order to introduce additional degrees of freedom for efficient control. This strategy is illustrated by two examples for heat exchanger network synthesis and can also be applied to other process subsystems.