(570b) New Amine-Containing Facilitated Transport Membrane and Process for CO2 Capture from Flue Gas

Application of membrane for CO₂ capture from flue gas has been limited by the trade-off between CO₂ permeance and CO₂/N₂ selectivity for most polymeric membrane materials. To overcome this limitation, we have studied the facilitated transport membrane (FTM) possessing both high permeance and selectivity and designed a membrane process that can capitalize on high-selectivity offered by FTM. We have synthesized a new FTM containing polyvinylamine as fixed-site carrier and an aminoacid salt, 2-(1-piperazinyl)ethylamine sarcosinate, as mobile carrier. The membrane was used to fabricate 1.4-m² spiral-wound modules, which exhibited a CO₂ permeance of 1450 GPU and a CO₂/N₂ selectivity of 185 at 67°C with actual flue gas at the National Carbon Capture Center in Wilsonville, AL, USA. Furthermore, significant increase in CO₂ permeance has been achieved upon the bulk removal of CO₂ for the range of CO₂ partial pressure relevant to carbon capture from coal-derived flue gas. For instance, the CO₂ permeance increased from 1464 to 1918 GPU when the CO₂ partial pressure reduced from 74.1 to 3.9 kPa at 67°C. Such a carrier saturation phenomenon has been modeled and incorporated into a novel two-stage membrane process featuring partial retentate recycle. As the bulk CO₂ removal reduces the CO₂ partial pressure gradually in the membrane module, this feature mitigates the carrier saturation and results in an uprising CO₂ permeance upon the CO₂ removal. For the membrane performance at 67°C, an attractive capture cost of $41.75/tonne can be achieved for 90% CO₂ capture in addition to offering the reduced system footprint. 70% CO₂ partial capture can further reduce the cost to about $32/tonne.