Inherent safety evaluation and optimization for the separating tetrahydrofuran/methanol/water ternary system

Abstract

The increasing scale of the chemical industry has attached growing importance to process safety. The distillation process is recognized as an energy-intensive process, therefore, the implementation of process intensification and optimization for energy-saving design necessitates an assessment of the inherent safety. In this work, we developed a comprehensive methodology including thermodynamic analysis, process intensification, optimization, and inherent safety evaluation for the tetrahydrofuran (THF)/methanol (MeOH)/water mixture separation. Firstly, the thermodynamic insights are employed to guide the distillation sequence design. Then, triple-column extractive distillation (TED), double-column reactive extractive distillation (DCRED), and reactive extractive dividing wall column (REDWC) are conceptually designed for the recovery of THF and MeOH from the mixture. A simultaneous optimization strategy based on the non-dominated sorting algorithm (NSGA-II) by taking total annual cost (TAC) and CO₂ emissions as objective functions to optimize the process parameters. The inherent process risk index (IPRI) is adopted to evaluate the processes’ safety. Results show that the TAC of the TED, DCRED, and REDWC processes are 1.78 × 10⁶ $/y, 1.25 × 10⁶ $/y, and 1.41 × 10⁶ $/y and the CO₂ emissions of the three are 1,449 kg/h, 1,130 kg/h, and 1,292 kg/h respectively. DCRED process is superior to the other two processes in term of economic and environmental benefits. The results of IPRI indicate that the REDWC process exhibits superior performance compared to the other two processes. This work provides a systematic method combining optimization and inherent safety evaluation for multi-azeotrope mixture separation.