Performance comparison of falling film distillation process configurations for energy-saving ethanol-water separation

Energy-saving distillation columns are currently of significant research interest for ethanol-water separation. The coupling of a falling film distillation column with a biphasic thermosyphon apparatus for ethanol-water separation can yield remarkable energy and space savings. In the pursuit of maturing the thermally efficient falling film distillation column technology for ethanol-water separation, knowledge gaps persist regarding the comparative analysis between two available falling-film distillation configurations: a single-tube and a multi-tube type. In this study, a comparative investigation of the steady-state performance of two distinct pilot-scale falling-film distillation configurations, namely a single-tube and a multi-tube type, both thermally integrated with a biphasic thermosiphon, was conducted to achieve ethanol enrichment from an aqueous stream. Pilot-scale tests were conducted to investigate the impact of operating conditions (feed temperature, feed mass flow rate, and temperature of the steam chamber) on ethanol enrichment, distillate flow rate, and energy consumption. Simultaneously, two potential thermal energy transfer arrangements were examined from the steam chamber to the distillation tubes (isothermal and non-isothermal). The single-tube type configuration was found to be more effective in enhancing ethanol enrichment, while the multi-tube type configuration exhibited higher ethanol recovery and lower energy requirements. An energy consumption savings of up to 78.5 % compared to traditional tray distillation technology was achieved using industrially relevant operating conditions, showing the potential for real-world application of thermally efficient falling-film distillation technology in ethanol-water separation. This study successfully confirmed the promising potential of thermally efficient falling-film distillation technology for ethanol-water separation and generated new practical knowledge to support large-scale industrial applications.