(374i) Carbon Capture from Residual Emissions Enabled By Facilitated Transport Membranes

Although carbon capture and storage (CCS) from large stationary sources is a leading strategy to reduce the carbon emissions, a carbon-neutral scenario in the energy sector cannot be achieved by the current CCS technologies since 90% CO₂ recovery is commonly assumed in the design. By taking coal-derived flue gas as an example, a 90% recovery through a primary capture system results in a residual flue gas containing 1–2% CO₂. If not captured, the residual emissions must be mitigated via direct air capture (DAC), which is usually hampered by a substantial cost. The focus of this presentation is to address the membrane carbon capture from dilute, yet stationary sources in order to achieve an overall >90% CO₂ recovery and thereby alleviate burdens upon DAC. To this end, the CO₂/N₂ separation performances of facilitated transport membranes (FTMs) containing aminoacid salts as mobile carriers were characterized with a CO₂ concentration of 0.05–20%. 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 DAC.