The distillation is one of the most energy-intensive unit operations in the chemical and pharmaceutical processes. As to the separation of azeotropic mixtures, energy consumption is even more critical. Extractive distillation is an important technique to separate binary or multiple azeotropes. It is important for the extractive distillation processes to achieve the energy consumption reducing. In recent years, partially thermally coupled distillation columns have been applied in extractive distillation to decrease the energy consumption. In this paper, the mixture of tetrahydrofuran, ethanol and water is separated by conventional extractive distillation and partially thermally coupled extractive distillation. The economics of steady state design for the conventional extractive distillation and partially thermally coupled extractive distillation process are explored by calculating total annual costs (TAC). The result showed that more than 16.3 % energy savings and 6.3 % TAC savings can be achieved by the partially thermally coupled extractive distillation process when compared with the conventional extractive distillation process. Partially thermally coupled extractive distillation is an effective way to achieve energy-saving and gain the economic for the separation of ternary azeotropic mixtures.
