Investigation of one-column and pressure-swing distillation of ethanol-water mixture

Absztrakt

In this study, the separation of ethanol-water mixture was investigated using the Unisim Design® simulation software with the NRTL activity coefficient model. Two different constructions were investigated: a single high-pressure distillation column (traditional process) and a pressure-swing distillation (PSD) system.  It is a relatively difficult separation procedure, because the components make a non-ideal, azeotropic mixture. With the one-column, traditional system the maximum reachable ethanol concentration in the product is equal with the azeotropic value. With the pressure-swing distillation (PSD) system higher ethanol concentration could be achievable in the product, however it has disadvantages (for example the higher costs). During this study the reachable bottom product ethanol concentration is 93 mole%. Some sensitivity analysis was made: the increasing pressure in the second column improves the ethanol mass flow and reduces energy demand in heat exchangers. These results show that pressure-swing distillation is a more efficient alternative technique for ethanol purification over the azeotropic composition in the viewpoint of energy demand in the condensers and reboilers and in the viewpoint of ethanol mass flow in the product.