Application of the thermally coupled extractive distillation for recycling octafluoropropane based on thermoeconomic analysis

• Introducing extractive distillation process for C 3 F 6 /C 3 F 8 /c-C 4 F 8 mixture separation. • Proposing partially thermally coupled improvement for C 3 F 8 refinement. • The operation and structure variables are optimized through bypass efficiency model. • The partially thermally coupled process can save energy and equipment costs. Octafluoropropane (C 3 F 8 ), hexafluoropropylene (C 3 F 6 ), and octafluorocyclobutane (c-C 4 F 8 ) are being widely used as etching/cleaning gases in microelectronic or semiconductor manufacturing process. These high-purity perfluorocarbons (PFCs) are becoming increasingly important as modern industry develops. In this work, a thermally coupled extractive distillation (TCED) process for separating the mixture of C 3 F 6 /C 3 F 8 /c-C 4 F 8 is proposed and compared to the traditional extractive distillation (ED) process. Two kinds of entrainers, toluene and N, N-dimethylformamide (DMF), are selected. These processes are optimized by minimizing the total annual cost (TAC) and restricting the product purity and recovery. The results show that toluene is more suitable to be used as the entrainer for thermally coupled improvement than DMF, and the TAC of the TCED is 5.9 % smaller than that of the ED process.