Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

Which separation scenarios are advantageous for membranes or distillations?

“…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 …”

“…Among above‐ambient distillations, as compared to the heat pump, the use of a hot utility is more common. This is partly because a distillation column is versatile to use heat in that it can utilize heat generated by another process unit in the plant and because the rejected condenser heat can be used elsewhere in the plant 22 . Therefore, it is not possible to easily conclude whether a heat pump or a hot utility should be used to run a distillation column.…”

“…On the other hand, as discussed in our recent publication, 22 assessing energy consumption of a distillation column is not straightforward due to multiple reasons. First, energy consumption of distillation needs to be often assessed in the context of its interaction with other unit operations in the plant.…”

“…First, energy consumption of distillation needs to be often assessed in the context of its interaction with other unit operations in the plant. 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 .…”

Continuous extraction and concentration of secreted metabolites from engineered microbes using membrane technology

“…However, note that the energy efficiency of the applied separation process heavily depends on the initial composition of the downstream. 21 The implementation of a continuous separation module also allows recovery of the process solvents that can then be recycled without the need of additional steps. Continuous liquid–liquid separation can be considered a low-cost, low-energy alternative to conventional separation techniques.…”