Design and Control of a Hybrid Extraction–Distillation System for the Separation of Pyridine and Water

Abstract

An improved separation method is proposed for the separation of pyridine and water as compared to previous separation designs. By using n-propyl format or diisopropyl ether (DIPE) as solvent, a hybrid extraction–distillation system can be designed for this separation task. Because the main extraction column does not require steam, significant savings in the operating cost and also the total annual cost can be realized as compared to the previous designs based on heterogeneous azeotropic distillation. Considering the density differences in each stage of the extraction column and in the decanter, DIPE is a more practically favorable solvent for reaching equilibrium in each stage for liquid–liquid separation. Dynamic control of this hybrid extraction–distillation system is also investigated. It is found that a trade-off between optimal steady-state design and dynamic controllability needs to be made in order to properly reject feed flow rate and feed composition disturbances.