Evaluation of Membrane-Based Post-Combustion Separation of CO2 On Power Plant Output

Evaluation of membrane-based post-combustion separation of CO2 on power plant output

Joseph A. Swisher and Abhoyjit S. Bhown

Electric Power Research Institute, Palo Alto, California

Carbon capture, utilization, and storage (CCUS) is an important set of technologies to reduce the carbon dioxide (CO₂) emissions resulting from firing fossil fuels to produce electricity. Due to the large volumes of gas involved, and in the case of post-combustion carbon capture, the low driving force for separation, carbon capture on the scale of a typical fossil fuel-fired power plant is projected to require large capital investment and reduce overall plant efficiency. One benchmark process for CO₂ removal is scrubbing with a solution of monoethanolamine (MEA) which has been estimated to reduce the output of a coal-fired power plant by 30%.¹ Several other gas separation technologies with the promise to reduce the penalty to plant efficiency have been investigated, including advanced solvents, solid sorbents, and CO₂ perm-selective membranes. Membrane-based gas separation processes for post-combustion carbon capture have several potential advantages, including modular scale-up, using no consumable reagents, and not requiring extraction of steam from the plant's power cycle. Proper evaluation of a given membrane technology requires coupling models of membrane performance to models of the rest of the power plant.^2,3,4 In this work, we have developed models of membrane modules from fundamental mass and energy balances. We developed models for all potential flow regimes, co-, counter-, and cross-current, both with and without sweep streams. These models were used to perform parametric studies of separation efficiency under different assumptions about existing and potential membrane properties. These membrane models were linked to a model of a power plant in a process simulator to study the effect of membrane properties and process configurations on the total area required for 90% capture of CO₂ and the attendant effect on net power output.

References

1.      Ramezan, M.; Skone, T. J.; Nsakala, N. Y.; Liljedahl, G. N. Carbon Dioxide Capture from Existing Coal-Fired Power Plants; DOE/NETL-401/110907; NETL: Pittsburgh, PA, 2007.  

2.      Merkel, T. C.; Lin, H.; Wei, X.; Baker, R. Power plant post-combustion carbon dioxide capture: an opportunity for membranes. J. Membr. Sci. 2010, 359, 126-139.

3.      Ramasubramanian, K.; Verweij, H.; Winston Ho, W. S. Membrane processes for carbon capture from coal-fired power plant flue gas: A modeling and cost study. J. Membr. Sci. 2012, 421–422, 299–310.

4.      Merkel, T. C. et al. Selective exhaust gas recycle with membranes for CO2 capture from natural gas combined cycle power plants. Ind. Eng. Chem. Res. 2012, 52, 1150-1159.