Synthesis and Optimization of Reaction-Separation-Recycle Systems with Complex Distillation Sequences

In this work, a novel synthesis superstructure for reaction-separation-recycle systems with complex distillation sequences is proposed. In the superstructure, complete interconnections among reactor modules, as well as necessary connections between reactor network and distillation sequence, are considered. State Task Network representation is used to describe the interconnections among distillation columns, so that all possible single-column sequences including sloppy separation ones are generated conveniently. Based on this, component distribution in distillation columns through Underwood equations is introduced to provide products with enough purity and multiple component mixtures as feedback to the reactor network to achieve the optimal composition distribution in the total flowsheet. Furthermore, to correctly estimate the number of theoretical stages of sloppy separation, the Hengstebeck-Underwood-Gilliland correlation method is employed, replacing the conventional Fenske-Underwood-Gilliland method in the distillation column design submodel. Finally, three literature examples are performed to demonstrate the feasibility and validity of the proposed methodology.