Mitigated carrier saturation of facilitated transport membranes for decarbonizing dilute CO2 sources: An experimental and techno-economic study

The CO2/N2 separation performances of facilitated transport membranes (FTMs) containing aminoacid salts as mobile carriers were characterized under dilute feed gases with 0.05–20% CO2. At a reduced CO2 partial pressure, the carrier saturation in the FTMs was mitigated, which enhanced both the CO2 permeance and CO2/N2 selectivity. The best FTM containing 2-(1-piperazinyl)ethylamine sarcosinate exhibited an uprising CO2 permeance from 1968 to 3822 GPU and an improved CO2/N2 selectivity from 249 to 472 with reducing CO2 content from 1% to 0.1%. The feasibility of this FTM is exemplified by designing a two-stage enriching membrane cascade to further remove 90% of the CO2 in a residual coal flue gas containing 1.75% CO2. Techno-economic analysis indicates a low capture cost of $83.8/tonne. The marginal costs beyond 90% capture are also evaluated for a variety of residual flue gases, indicating that the FTM-based capture from the coal or cement plant residual flue gas is more cost effective than direct air capture.