Economic and environmental comparison of bioethanol dehydration processes via simulation: reactive distillation, reactor-separator process and azeotropic distillation

The bioethanol produced using fermentation is obtained at a very low concentration. To be used as fuel in gasoline blends, a higher than 99% weight purity is required. Therefore, highly demanding energy separation and purification processes are used. Given this fact, this work presents, via simulation, an economic and environmental comparison of alternative methods for ethanol dehydration based on ethylene oxide/propylene oxide hydration and azeotropic distillation with benzene and cyclohexane. These reactive methods consist of conventional reaction separation processes and intensified processes such as reactive distillation (RD), both coupled with organic Rankine cycles, offering an additional value-added product (ethylene glycol or propylene glycol), electric power generation and the capacity to reduce the global process steps in anhydrous ethanol production. The results indicate that reactive dehydration, specifically the reactor-separator process using propylene oxide at a low ethanol concentration (dilution effect of the fermenter output), is the best economic and environmental option among all the processes studied for anhydrous ethanol production. Likewise, reactive dehydration yields a higher net profit, ethanol yield and ethanol purity and lower CO2 emissions than azeotropic distillation. [GRAPHICS] .