Simultaneous Optimization of Heat-Integrated Extractive Distillation with a Recycle Feed Using Pseudo Transient Continuation Models

This paper proposes a heat-integrated extractive distillation with a recycle feed (HIEDRF), including a extractive distillation column (EDC), solvent recovery column (SRC), and concentrator. Heat integration was easily achieved by coupling the SRC condenser and EDC reboiler. However, optimizing the complex HIEDRF is challenging, because the associated variables in both distillation and heat integration systems must be considered simultaneously. To solve this multivariable optimization problem, we developed a new pseudo transient continuation (PTC) model. Based on a mixed steady-state-time relaxation optimization algorithm, the associated PTC model was solved using Aspen Custom Modeler. Two case studies, acetone/methanol and methanol/toluene, were investigated. For the acetone/methanol system, the HIEDRF reduced energy consumption by around 27% and total annualized cost by around 16% with respect to both the conventional extractive distillation system and extractive distillation with a recycle feed. For the methanol/toluene system, the reductions were around 21% and 10%, respectively.