Document Type: Research Paper
Singapore Membrane Technology Centre
Johnson Matthey Technology Centre, UK
Nanyang Technology University Singapore
Gas-liquid membrane contactor (GLMC) is a promising alternative gas-contacting configuration for effective CO2 removal. The physicochemical properties of membranes may synergistically affect GLMC performances, especially on long-term operations. In this work, commercial polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes were applied to explore the effects of their physicochemical properties on long-term CO2 absorption performances in a bench-scale GLMC rig. PP membranes with pore size of 19 nm, thickness of 0.046 mm, and porosity of 58% achieved high CO2 fluxes when feeding pure CO2 (5.4 and 24.4 × 10-3 mol/m2·s using absorbents of water and 1M monoethanolamine (MEA), respectively), while PVDF membranes with pore size of 24 nm, thickness of 0.343 mm, and porosity of 84% presented a good CO2 separation performance from the simulated biogas using 1M MEA (6.8 × 10-3 mol/m2·s and 99.9% CH4 recovery). When using water as absorbent, the coupled phenomena of membrane wetting and fouling restricted CO2 transport and resulted in continuous flux loss during the long-term operation. When using MEA as absorbent, PP and PVDF membranes suffered dramatic flux declines. A series of membrane characterizations demonstrated that the morphology, pore size, hydrophobicity, and stability of selected commercial membranes were greatly affected by MEA attack during long-term operations. Therefore, selection criterion of microporous membranes for high-efficiency and long-term stable CO2 absorption was proposed. It is hoped that this study can shed light on improving membrane fabrication processes or applying novel membrane surface modifications in future studies to facilitate practical applications of the GLMC technology.