Energy-efficient separation design of diisopropylether/isopropanol/water system having three distillation regions and liquid-liquid envelope

This work mainly focus on providing an energy-efficient design scheme for the separation of ternary mixture containing diisopropyl ether, isopropanol and water. The residue curve maps of this mixture is very complex, including: three binary azeotropes, one ternary azeotrope, three distillation regions and liquid–liquid envelope. With the preference of not adding foreign component into this separation, a new energy-efficient design flowsheet is proposed in this paper making use of natural liquid–liquid separation in a decanter together with varying operating pressure to expand the operating distillation region for the respective column. This design flowsheet can further be heat-integrated to combine a condenser of one column with partial heat input of a reboiler of another column and also add a feed-effluent heat exchanger to preheat the feed of one column. By comparing the economic performance of the proposed design flowsheet with that of a design flowsheet published in a recent paper, significant savings in total annual cost of 42.9% and in annual operating cost of 48.1% can be realized by our proposed design flowsheet.