This talk will provide a detailed techno-economic analysis (TEA) of a staged hollow fiber membrane separation process, based on facilitated transport membranes, for the selective permeation of CO2 from atmospheric air, to produce a 5% CO2-enriched product stream. Direct air capture of CO2 is a proposed route of tackling the rising CO2 levels in the atmosphere, and membrane-based processes could provide a continuous and modular pathway to accomplish this objective. Our prior work has identified the optimum membrane properties to achieve a desirable region of operation using a process operability approach [1]. Furthermore, the membrane transport mechanism was set to a facilitated transport mechanism, which involves a CO2 binding coefficient with the amine carriers present and CO2 diffusion coefficient. A refined operability analysis was then performed on this specific membrane material connecting these intrinsic membrane material properties with the overall process outputs (cost, recovery, and CO2 purity) [2]. In this work, the AVEVA Process Simulation platform and its membrane model has been utilized for the design of a staged separation process based on the results from our prior work. The focus of the current work is to accurately determine the capital and operating costs associated with an optimal process design. The TEA analysis, shown in the presentation, will compare two scenarios – a base case which uses a general flux model and an optimized case which uses the facilitated transport model [3] and considers topological changes to the process design. These scenarios are outlined to connect the membrane material characteristics to the overall process efficiency in capturing and concentrating CO2, and to evaluate their impacts on the capital costs of the process. Our preliminary simulation results for a two-stage module design reveal that the permeate vacuuming and eventual compressing (from vacuum to atmospheric pressure) of the permeate, account for the highest energy consumption of the process, with the 1st stage bearing the highest cost. The 1st stage, in fact, concentrates the CO2 by ~50X, from 425 ppm (0.0425%) to ~2%, and utilizes the high-performance ionic liquid-based facilitated transport membrane. The subsequent stages use a traditional membrane material since further concentration does not require a sophisticated material. This study highlights the scope of using hollow fiber gas separation membranes as an alternative either as a standalone process or in hybrid form with other separation processes (adsorption/absorption), for CO2 direct air capture, offering cost and scalability advantages. By evaluating process efficiency and economics, it supports the development of viable membrane-based CO2 removal strategies.
References
1 - Gama, V; Dantas, B.; Sanyal, O.; Lima, F. V.; Process Operability Analysis of Membrane-based Direct Air Capture for Low-Purity CO2 Production. ACS Eng. Au, 2024, 4, 394-404, https://doi.org/10.1021/acsengineeringau.3c00069
2 - Gama, V; Roy, D.; Lima, F. V.; Sanyal, O.; Connecting Material Characteristics with System properties for Membrane-based Direct Air Capture (m-DAC) using Process Operability and Inverse Design Approaches. I&ECR, 2025, https://doi.org/10.1021/acs.iecr.4c04553
3 - Xu, H.; Pate, S. G.; O’Brien, C. P. Mathematical Modeling of CO₂ Facilitated Transport across Polyvinylamine Membranes with Direct Operando Observation of Amine Carrier Saturation. Chem. Eng. J. 2023, 460, 141728. https://doi.org/10.1016/j.cej.2023.141728
