A new hybrid membrane separation process for enhanced ethanol recovery: Process description and numerical studies

Abstract Ethanol is a biofuel, produced through the fermentation of sugars derived from biomass. Its usefulness as a fuel is limited by the energy intensive nature of the ethanol separation process. The ethanol recovery process is inefficient due to the dilute nature of the fermentation product and the presence of the ethanol−water azeotrope. This investigation presents a new hybrid separation process for energy efficient ethanol recovery. The new process is a hybrid of distillation and pervaporation. However, as opposed to most other hybrid processes, the distillation and pervaporation processes are combined into single unit. An overview of the proposed system was provided and differences to the conventional separation process were highlighted. A mathematical model was derived to explain the transport phenomena occurring in the hybrid process. The model was then used to compare the process to distillation. It was shown that the hybrid process is capable of breaking the ethanol-water azeotrope. It was also demonstrated that the pervaporation process, which is associated with both material and energy transfer, induces partial condensation of the vapor and thereby affects the efficiency of vapor−liquid contacting. Simulations were presented to show the impact of reflux ratio and pervaporation flux on the performance of the process.

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