There are only so many unit operations known to chemical engineers, so it seems safe to say that every conceivable pair of them has been considered and, where appropriate, tested out in lab or plant. Some pairs exhibit such useful synergies that the combination becomes a unit operation in its own right, and it acquires a name of its own; witness evaporation + condensation = distillation.

My work experience in the field of solvent recycling led me to question the combination of evaporation and gas absorption. In the years from 2000 and 2008 I led a team that successfully applied a variation of this combination to a pervaporation  demonstration plant. Then, through the start-up technology company Drystill I participated in the creation and development of a device called a SAM that combines the two unit processes into a single package with internal heat integration. Drystill has applied for international patent protection on this device and is in the process of testing a prototype in collaboration with Fielding Chemical Technologies Inc. of Mississauga, Canada (check the “commercialization” tab for more details).

I have searched the literature for references to current and previous attempts to combine evaporation and absorption. So far I have come up almost empty-handed. Yet this combination can provide low temperature distillations with half the energy used by current industrial practice. Has something been overlooked? As a community of professionals serving the world’s chemical engineering needs, we ought to talk.

To facilitate discussion, I have given combination of evaporation and gas absorption a name: “Pass-through distillation” and created this web site to serve as a clearing house for information on the topic. It is intended for the benefit of engineers and scientists in academia and industry world-wide.

If this field of enquiry ultimately generates wealth, some of it may rub off on Drystill and I will openly accept my share. In the meantime my activities relative to this web site will be directed toward shedding light on a topic that may benefit our planet.

Ian McGregor P. Eng.


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