Electrochemically Mediated Separation for Carbon Capture

Energy Procedia, Vol 4, pp 860-867, Feb (2011).

February 2011
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Electrochemically Mediated Separation for Carbon Capture

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Carbon capture technology has been proposed as an effective approach for the mitigation of anthropogenic CO2 emissions. Thermal-swing separation technologies based on wet chemical scrubbing show potential for facilitating CO2 capture at industrial-scale carbon emitters; however, the total operational and capital costs resulting from the high energy consumption are prohibitive for their implementation. Electrochemically mediated processes are proposed to be the next generation of CO2separation technology that can enable carbon capture to be a more viable option for carbon mitigation in the near future. This technology utilizes electrochemically active sorbents that undergo significant changes in their molecular affinity for CO2 molecules as they progress through an electrochemical cycle. This nearly isothermal separation process consumes electrical energy to facilitate effective CO2 capture and regeneration processes under more benign conditions of sorption and desorption than in traditional continuous wet-scrubber operations. This electrically driven separation process has the potential to significantly reduce the difficulty of retrofitting CO2 capture units to existing fossil fuel-fired power generators. The ease of installing an electrically driven separation system would also allow its application to other industrial carbon emitters. The design of such a system, however, requires careful consideration since it involves both heterogeneous electrochemical activation/deactivation of sorbents and homogeneous complexation of the activated sorbents with CO2 molecules. Optimization of the energy efficiency requires minimizing the irreversibility associated with these processes. In this study, we use a general exergy analysis to evaluate the minimum thermodynamic work based on the system design and the electrochemical parameters of quinodal redox-active molecules. Using this thermodynamic framework, our results suggest that the proposed technology could capture CO2 from a dilute post-combustion flue gas and regenerate CO2 at 1 bar with high efficiency, if a two-stage design is effectively implemented.

MITEI Authors

Howard Herzog Senior Research Engineer

MIT Energy Initiative

T. Alan Hatton Professor

Department of Chemical Engineering