(758a) Electrochemical Redox Flow Devices for the Electrically Driven Scrubbing of Acid Gases

The concept, thermodynamic
analysis, and preliminary experimental results are presented for an
electrochemical redox flow system capable of scrubbing acid gases from either
dilute streams (such as air) to more concentrated industrial flue gases.  The
ability to electrically scrub acid gas offers significant advantages over
existing thermal and pressure swing techniques.  Thermal scrubbing is an
ineffective strategy when not coupled with a Rankine cycle due to the narrow
temperature range and resulting poor Carnot efficiency.  Pressure swing
systems, in contrast, are able to operate through electrical energy, but suffer
from the inability to separate gas sorbates from dilute streams due to the weak
binding enthalpies inherent to physical sorption processes.

An electrochemical scrubbing
process offers the possibility of a truly ?drop-in? solution for powerplants
that requires no reconfiguration of their internal turbine systems. 
Additionally, electrochemical scrubbers can be installed anywhere with access
to electricity in order to supply new markets for CO₂ such as
photosynthetic biofuels or electrofuels that will have large CO₂
demands but may not want to be located near an existing powerplant.

The system consists of an
electrochemical flow cell (which closely resembles a redox flow battery) in
tandem with a traditional gas absorber unit. A theoretical framework for
evaluating redox-responsive sorbents for redox flow separations based on their
kinetic and thermodynamic properties is presented.  Experimental results of the
sorbents have been analyzed with this framework to demonstrate the feasibility
of the electrochemical redox flow scrubbing process.