Mathematical modeling of CO2 separation using different diameter hollow fiber membranes

• Published in: International journal of greenhouse gas control 2021-01, Vol.104, p.103204, Article 103204
• Main Authors: Ghobadi, Jalil, Ramirez, David, Khoramfar, Shooka, Kabir, M.M., Jerman, Robert, Saeed, Muhammad
• Format: Article
• Language: English
• Subjects: CO2/CH4separation; computational fluid dynamics; Membrane contactor; PTFE hollow fibers; two-dimensional mathematical model
• ISSN: 1750-5836; 1878-0148
• DOI: 10.1016/j.ijggc.2020.103204

•A 2-D model developed to simulate the transport of CO2 species from gas mixture.•The impact of hollow fibers geometry on the removal of CO2 is investigated.•Hollow fibers with smaller inner diameters showed a superior CO2 removal.•The impact of absorbent and gas velocity on the CO2 removal were investigated. This research presents a 2D mass-transfer simulation model using computational fluid dynamics (CFD) for separation of CO2 from a binary gas mixture of CO2/CH4 by means of polytetrafluoroethylene (PTFE) hollow fiber membrane contactor (HFMC). Governing equations with their corresponding boundary conditions are solved using COMSOL Multiphysics and the results are validated against reported experimental data. Convection and diffusion flux vectors and concentration gradient of CO2 species in the radial and axial directions of the HFMC are investigated. This study provides an opportunity to investigate the effects of gas and liquid cross flow velocities on the overall performance of membrane contacting system. The results demonstrate that increasing the liquid phase velocity improves the CO2 absorption performance of the membrane system, while increasing the gas mixture velocity deteriorates the CO2 separation of the system. The impact of hollow fiber geometry on the removal of CO2 is investigated and the results indicate that hollow fibers with smaller inner diameter provides higher effective mass-transfer area and therefore superior CO2 removal performance. Furthermore, the modeling predictions for the CO2 removal are in good agreement with the experimental data under various ratios of gas to liquid velocity. The PTFE hollow fiber membrane contacting system showed a great potential for separation of CO2 from gas mixtures.