Separation of a ternary mixture with multiple azeotropes via pressure-swing distillation

BACKGROUND The ternary mixture of tetrahydrofuran (THF), ethanol and water contains multiple azeotropes with the sensitivity to pressure variation. The pressure-swing distillation (PSD) is a promising method to achieve the system's separation objective since it avoids many potential problems caused by adding a third component. RESULT A variety of separation sequences were synthesized on the ternary diagram, including the sequences of WLEMTH, WLTH E-M, THEMWL, THWLEM, EMTHWL and EMWLTH. The optimal design parameters of these sequences were obtained based on the minimum total annual cost (TAC) by using the sequential iterative global optimization algorithm. Furthermore, six kinds of heat integration that improve energy efficiency were implemented for the optimal alternative of EMTHWL. CONCLUSION The results show that the EMTHWL configuration has the lowest TAC, saving 37.84% of the economic cost compared to the THEMWL which has the highest TAC. The partial heat integration among three columns can achieve almost the same reductions in energy requirements and carbon dioxide emissions (44.9%) as the full heat integration among three columns (45.4%). In addition, it is predictable that the partially heat-integrated alternative compared to other fully heat-integrated schemes has less undesirable side effects in the aspect of dynamic control. (c) 2019 Society of Chemical Industry