Separation of propylene oxide-methanol-water mixture via enhanced extractive distillation: Design and control

Abstract

The ternary azeotropic mixture of propylene oxide-methanol-water generally occurs in the direct oxidation of hydrogen peroxide and needs to be separated effectively. This paper explores two energy-efficient configurations with water as solvent, namely extractive dividing-wall column (EDWC) and side-stream extractive distillation (SSED), in terms of the potential economic advantages compared to conventional extractive distillation (CED) and the dynamic control. Several steady-state designs with the minimum total annual cost (TAC) by using a sequential iterative optimization method are achieved and compared. Regarding the controllability, four control structures for the SSED are developed and examined via introducing the feed flow and composition disturbances as well as one control structure for the EDWC. Similar to the EDWC, the SSED can be well controllable via an optimal control structure relying on only temperature measurements.