Conceptual design of sustainable extractive distillation processes combining preconcentration and extractive distillation functions for separating ternary multi-azeotropic mixture

• Special ternary multi-azeotropic mixture is purified using extractive distillation. • The proportion of one component in the ternary multi-azeotropic mixture is large. • Novel extractive distillation processes are proposed based on conventional schemes. • Preconcentration and extractive distillation functions are integrated. • Two cases are investigated to prove economic advantage of novel schemes. Azeotropic mixtures with a large content of one component are often encountered. Several energy-efficient three-column extractive distillation processes with integrated distillation column (TCED-IDC) are conceptually designed for separating ternary multi-azeotropic mixtures with a large content of one component on the basis of the corresponding four-column extractive distillation (FCED) processes. The energy consumption and economic advantages of the TCED-IDC processes which realize the integration of extractive distillation function and preconcentration function are demonstrated by two cases, methanol/acetonitrile/benzene ternary azeotrope with chlorobenzene as solvent (Case1) and methyl acetate/ethyl acetate/methanol ternary azeotrope with dimethyl sulfoxide as solvent (Case2). The economic savings resulting from the integration of preconcentration function and extractive distillation function depend heavily on feed compositions and azeotropic compositions. In terms of assumed feed compositions, the TCED-IDC process can achieve 27.61%/21.64% economic costs reduction in Case1 and 49.66%/1.73% economic costs reduction in Case2 compared to the TCED process and the FCED process.