Energy- efficiency with enhanced process safety in propylene-propane separation via multi-objective optimization and redesign

Separation of propylene–propane mixtures requires substantial investment and energy consumption due to their similar molecular sizes and physical properties. Although many alternative processes have been investigated to replace distillation, none have demonstrated sufficient superiority over distillation columns in industrial practice. This study aimed to enhance both the energy efficiency and inherent process safety of an existing distillation unit without additional capital investment. A multi-objective optimization framework based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was applied to identify optimal trade-offs between energy consumption, operating revenue, and Comprehensive Inherent Safety Index (CISI). The TOPSIS method was then used to select the most balanced operating point from the Pareto-optimal solutions. The results showed that significant improvements could be achieved through minor and controllable operational adjustments, providing a practical and directly applicable optimization strategy. Furthermore, a redesigned process configuration was proposed to increase polymer-grade propylene production, driven by the growing market demand for high-value polypropylene. The proposed redesign achieved the product shift with minimal capital modification while maintaining feasible operation. Overall, the findings highlight a cost-effective and industrially relevant approach that quantitatively integrates safety with performance improvement in existing separation systems.