Conclusion and Outlook

The work described here demonstrates that, relative to traditional random packing, the separation efficiency of oxygen from air in an MCD column can be greatly enhanced by using a custom AMPH internal structure. This enhanced efficiency results from the porous liquid wicking structures present in the AMPH column itself, not to anything unique to air separation. Accordingly, this approach can reasonably be expected to improve efficiency in other types of distillation systems as well. This enhanced efficiency is an enabling technology for small scale air separations including the collection of xenon from the atmosphere.
AM allows internal structures to be constructed that are not available via traditional manufacturing techniques. Future work in distillation could continue to explore other structural changes to improve mass transfer. Further, the improvement observed here suggests that AM could be applied to other processes for similar improvement. For example, it is possible that the efficiency and/or selectivity of an adsorption process could be improved by controlling the microstructure of the adsorbent via AM. Similarly, AM could be used to create heat exchangers with internal flow structures that optimize heat transfer in ways not heretofore possible.
The principles that allow the AMPH MCD column to improve separation efficiency should scale up to larger distillation systems, but current direct metal laser sintering equipment constrains the maximum part size that can be fabricated. For example, the i3DMFGTM EOS® M400.4 platform used in this work is a 40x40x40 cm cube, so the part must fit within those dimensions. Also, in a distillation column the fluid entering the column must be properly distributed across its entire width. In columns with small widths—such as those tested in this work—this is straightforward and requires no special design, but with a larger device this would likely require a specialized header to distribute uniform liquid flow to the wicking structures.