CHAPTER 14 Design Considerations for Postcombustion CO 2 Capture With Membranes Simona Liguori, Jennifer Wilcox Colorado School of Mines, Golden, CO, United States 1. Introduction The design of low-energy intensive, low-cost, and efficient CO 2 capture unit is of extreme importance for the development of carbon capture and storage (CCS) technologies at industrial scale (Davidson and Metz, 2005). This mainly holds for the postcombustion, where the carbon dioxide is diluted in nitrogen with a volume fraction typically between 4% (i.e., gas turbine) and 15% (coal-fired power plant) and the flue gases to be treated are at atmospheric pressure conditions (Table 14.1). These two specificities address a great engineering challenge, especially in terms of the energy requirement of the separation process (Steeneveldt et al., 2006; Herzog, 2001; Wilcox, 2012). Several capture technologies are being developed and evaluated for CO 2 capture applications such as absorption, adsorption, cryogenic processes, membranes, and chemical looping (Figueroa et al., 2008). The identification of the most efficient process is subject to controversial debates. The ideal CO 2 capture process should show (1) high selectivity of CO 2 with respect to the other gases, to reach a concentration above 95%; (2) minimal energy requirement; (3) minimal environmental impact, which can be evaluated from the waste produced by the CO 2 capture unit and water footprint; (4) minimal overall cost. By considering these characteristics, the absorption into a chemical solvent (such as amine solution) is currently considered as the best available and most mature technology (Steeneveldt et al., 2006). Amine solvents have been used for decades for natural gas treatment. However, the two main drawbacks of the amine absorption process correspond to a high-energy requirement (Steeneveldt et al., 2006) and waste production. Specifically, almost 4 GJ/t of thermal energy, corresponding to 50% of the steam leaving the intermediate pressure steam turbine module that has to be employed for solvent regeneration, and the degradation of the solvent lead to additional material costs, high disposal costs, and additional environmental pollution. New solvents or alternative separation processes that would not exhibit these disadvantages are explored. In particular, Current Trends and Future Developments on (Bio-) Membranes. https://doi.org/10.1016/B978-0-12-813645-4.00014-3 Copyright © 2018 Elsevier Inc. All rights reserved. 385