Single-Column Partial Vapor Recompression Retrofit Design for Separation of 1,2-Propanediol and Ethylene Glycol Mixture

For the separation of the close-boiling 1,2-propanediol and ethylene glycol mixture, several process intensification (PI) schemes have been proposed for the two-column configurations. However, no PI technology has yet been investigated for the challenging single-column design operating at atmospheric pressure (SCD). The previously published improvements include the economically modified single-column design (MSCD) as well as high-pressure configurations with (HPDHI) and without (HPD) feed-preheating heat integration. Therefore, this study proposes a partial vapor recompression (SCD-PVR) configuration to intensify this separation using UniSim Design software. Economic and environmental performances were evaluated through total annualized cost (TAC) and CO2 emissions. When directly compared with the SCD, MSCD, HPD, and HPDHI schemes, the SCD-PVR achieved CO2 emission reductions of 67.9%, 68.6%, 61.2%, and 56.0%, respectively. Considering a 5-year payback period, SCD-PVR outperformed the SCD and MSCD schemes, decreasing TAC by 9.7% and 11.2%. For a 10-year payback period, the benefits became more significant, with TAC reductions of 31.4%, 32.7%, 17.2%, and 9.3% relative to SCD, MSCD, HPD, and HPDHI. These findings demonstrate that SCD-PVR provides a more energy-efficient, environmentally sustainable, and economically attractive alternative for retrofitting existing plants.