Discussion on Water Condensation in Membrane Pores during CO₂ Absorption at High Temperature

• Main Authors: Zhe Phak Chan, Lin Li, Guodong Kang, Norfaizah Ab Manan, Yiming Cao, Tonghua Wang
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Membranes
• Subjects: capillary condensation; membrane contactor; CO₂ absorption; membrane wetting; high temperature
• Online Access: https://www.mdpi.com/2077-0375/10/12/407

Water condensation is a possible cause of membrane wetting in the operation of membrane contactors, especially under high-temperature conditions. In this study, water condensation in pores of polytetrafluoroethylene (PTFE) hollow fiber membranes was investigated during high-pressure CO₂ absorption around 70 °C. It was found that the liquid accumulation rate in the treated gas knock-out drum was constant during continuous operation for 24 h when all experimental conditions were fixed, indicating a stable degree of membrane wetting. However, as the operating parameters were changed, the equilibrium vapor pressure of water within membrane pores could change, which may result in a condensation-conducive environment. Water condensation in membrane pores was detected and proven indirectly through the increase in liquid accumulation rate in the treated gas knock-out drum. The Hagen–Poiseuille equation was used to correlate the liquid accumulation rate with the degree of membrane wetting. The degree of membrane wetting increased significantly from 1.8 × 10⁻¹⁵ m³ to 3.9 × 10⁻¹⁵ m³ when the feed gas flow rate was reduced from 1.45 kg/h to 0.40 kg/h in this study due to water condensation in membrane pores. The results of this study provide insights into potential operational limitations of membrane contactor for CO₂ absorption under high-temperature conditions.