Methods to assess numerous distillation schemes for binary mixtures

Which separation scenarios are advantageous for membranes or distillations?

“…As we will see later, our results for other separations reveal that the membrane process is usually more energy attractive than the corresponding distillation only when the feed is highly enriched in the more volatile/permeable component and the recovery in the purified product stream of this component is modest. This result is also consistent with the previous findings that when a feed stream is highly enriched in one of the components, the thermodynamic efficiency of a conventional binary distillation tends to be low 11,12 . On the other hand, we recently studied the separation of 50/50 mixture of p‐xylene/o‐xylene, which is not enriched in any one component, to recover 99% p‐xylene at a purity of 99.5 mol% and found that power consumed by a six‐stage membrane cascade was nearly three times that of a heat pumped distillation even when the permselectivity of the membrane was assigned a hypothetically high value of 10,000 22 …”

“…Many recent studies have portrayed distillation as being inherently energy‐intensive when compared to other separation processes such as membranes 5–9 . Furthermore, there seems to be a general misconception about the efficiency and maturity of the distillation processes 10,11 . Past studies have identified the operating conditions under which a distillation process is either energy efficient or inefficient 12–14 .…”

“…As discussed by Chavez Velasco et al, 22 the origin of the heat source for the reboiler and the destination of the heat sink from the condenser play an important role in the assessment of energy efficiency. Second, there are numerous strategies to manage the heat needed in a binary distillation, and one must carefully evaluate the entire space of options to truly identify the most energy‐efficient approach 10,11,23 . Third, distillation columns operate on the basis of heat supplied in their reboilers, while membranes operate using work energy through pumps and compressors.…”

Thermodynamic efficiency of membrane‐assisted distillation processes

“…While these assumptions would result in infinitely large condenser and reboiler areas due to the vanishing temperature driving force, any increase in the hot utility temperature or decrease in the cold utility temperature would induce additional external exergy losses in the heat exchangers, which would diminish the thermodynamic efficiency of the separation processes. 26 For the sake of the current study, we focus on the comparison of the (internal) efficiency of the considered separation processes, deliberately selecting this rather optimistic assumption for the utility temperatures, pointing out that the subsequently reported results are reflective of this decision. However, practical (external) efficiencies of the processes will be lower accounting for exergy losses in the heat exchangers due to increased hot utility temperatures and decreased cold utility temperatures.…”

“…The first approach was further extended by Agrawal and Fidkowski 23 to investigate ternary distillation configurations, including basic sequences as well as thermally coupled column configurations for the separation of ideal mixtures. Further studies have dealt with energy‐ and heat‐integrated distillation systems, respectively 24–26 . Similar to Agrawal and Herron, 21 Blahušiak et al 27 investigated the influence of the feed composition for binary separations in order to derive recommendations for improving the thermodynamic efficiency of distillation‐based separations.…”