Novel sustainable design of pressure-swing distillation coupled with natural decanting and Organic Rankine Cycle for separating n-propanol/benzene/water mixture

The separation of ternary azeotropic mixtures is a common challenge in the chemical industry due to the unique properties of azeotropes. This phenomenon complicates the separation processes, as traditional distillation methods may not effectively separate the components. The present work introduces a novel pressure-swing distillation (NPSD) process integrated with natural decanting for the effective separation of an n-propanol/benzene/water mixture. By exploiting the liquid–liquid envelope characteristics of the mixture, phase separation prior to distillation significantly enhances the separation efficiency. The NPSD process was optimised using the NSGA-II, addressing economic, environmental, and energetic objectives. Key findings reveal that the implementation of decanting allows the NPSD process to operate without substantial pressure adjustments, thereby facilitating fine separation more efficiently than conventional pressure-swing distillation designs. The proposed NPSD process can achieve up to 25.76 % savings in TAC while reducing CO₂ emissions and improving energy efficiency. Furthermore, the integration of mechanical vapour recompression heat pump and Organic Rankine Cycle systems enhances energy saving, resulting in a TAC reduction of up to 31 % and a decrease in CO₂ emissions of up to 38 % compared to existing energy-efficient designs. These findings highlight the potential of the NPSD-MVR-ORC system for sustainable chemical separation processes.