Distillation Columns with Multiple Phase Divisions: How They Improve Thermodynamic Efficiency and Decrease Energy Consumption

Distillation efficiency can be improved by columns with multiple phase divisions, also known as parastillation (vapor division) and metastillation (liquid division). Although, previous studies demonstrate that these configurations improve separation efficiency, little is known about the mechanisms that cause this improvement. These mechanisms are elucidated through exergetic and driving force analyses. Methanol-ethanol and multicomponent hydrated bioethanol purifications were investigated. Thermodynamic efficiency and exergy losses are improved when the number of phase divisions is increased. In methanol-ethanol distillation, the increase of the number of phase divisions from one to eight decreases both the operational costs and CO2 emissions by 34% and increases thermodynamic efficiency by 23%. Considering a more feasible number of phase divisions, from the construction point of view, four divisions improve operational costs by 31%, over one division. In the production of hydrated bioethanol, four-vapor divisions lead to a reduction in energy consumption by 18% when compared with conventional distillation. This study shows that it is possible to reduce operating costs to a value close to the theoretical minimum, without a significant increase in capital costs. This observation contrasts with the conventional process, in which the reduction in operating costs necessarily leads to higher distillation columns and capital costs.