Water vapor effects on CO₂ separation of amine-containing facilitated transport membranes (AFTMs) module: mathematical modeling using tanks-in-series approach

Amine-containing facilitated transport membranes (AFTMs) are emerging membranes and have great potential for CO₂ capture. AFTMs are particularly suitable for humid flue gases, as water vapor enhances the facilitated transportation of CO₂. However, there is a lack of mathematical models available to evaluate the impact of water vapor on CO₂ separation performance for large-scale membrane modules. Therefore, developing a mathematical model considering the water vapor effects is of great importance to guide the large-scale applications of AFTMs for CO₂ capture. In this study, a mathematical model using tanks-in-series approach for CO₂ capture through AFTMs is proposed. In this model, the tanks-in-series approach can reflect the variable (water vapor-dependent) gas permeance along the membrane module. Modeling results showed the necessity of considering the effect of water vapor content decline along the module. In addition, both increasing temperature and pressure primarily lead to a faster decline of relative humidity (RH) along the membrane module, resulting in an increase of CO₂ recovery but a decrease of CO₂ product purity. For a gas stream with relatively low water vapor content (<2% in this study), different H₂O permeance has a minor effect on separation performance. Moreover, permeate gas with higher water vapor content as well as higher RH is considered more suitable for further treatment of second stage membrane separation. In conclusion, the proposed model provides insights for comprehensive parameter analysis of membrane CO₂ capture simulation and could support the development of large-scale AFTMs separation applications, particularly for systems design and more accurate performance estimation. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.