Optimal design and performance enhancement of heteroazeotropic and pressure-swing coupling distillation for downstream isopropanol separation

The isopropanol stream obtained by direct hydration of propylene is mainly the diisopropyl ether-isopropanol-water ternary mixture with a low concentration and multiple azeotropes that leads to high energy usage for downstream isopropanol processing. For this, a new three-column heteroazeotropic and pressure-swing coupling distillation process (TCHPSD) is proposed and further intensified by employing dividing-wall column (DWC) and vapor recompression (VRC) technologies, resulting in two energy-efficient processes (TCHPSD-DWC, TCHPSD-DWC-VRC). Rigorous simulations and a dual-staged sequential iterative method are used in the design and optimization of processes. The results show that the TCHPSD-DWC-VRC process achieves a significant reduction in total annual costs (12.0%) and energy consumptions (63.8%) in comparison with the TCHPSD process. Furthermore, thermodynamic and environmental evaluations based on exergy efficiency, pinch analysis and CO2 emissions display that this double-effect intensified process is industrially sustainable, especially for industrial sites without access to cheap heat sources.