(516b) New Highly CO2-Selective Amine-Based Membranes for Carbon Capture

Ho, W. S. W., The Ohio State University
Han, Y., The Ohio State University
Salim, W., The Ohio State University
Chen, K., The Ohio State University
CO2 capture from flue gas in coal- and/or natural gas-fired power plants and from <1% CO2 concentration sources, e.g., the residual flue gas after the primary CO2 capture system and coal-mine gas streams, requires a high CO2/N2 selectivity of 140 along with a very high CO2 permeance of about 700 GPU (1 GPU = 10-6 cm3 (STP)/(cm2 · s · cmHg)) or higher in order to use a stand-alone membrane process. For the CO2 capture, we have synthesized new amine-containing membranes, showing a high CO2/N2 selectivity of >140 and a high CO2 permeance of >1000 GPU. The membrane was scaled up to 14 inches in width using continuous roll-to-roll fabrication. Aided by a material balance equation, three variables, namely the coating-knife gap setting, web speed, and coating solution concentration, were identified as the critical factors to control the membrane selective layer thickness. This resulted in the membrane with a selective layer of <200 nm. The scale-up membrane was fabricated into spiral-wound membrane modules for testing with simulated flue gas containing about 20% CO2, 77% N2, 3% O2 and 1 – 3 ppm. Both the scale-up membrane and the membrane modules exhibited similar results as the flat-sheet membrane tested in the lab. The membrane module has been scaled up to a size of more than 10,000 cm2 membrane area. The module showed stable CO2 permeance and CO2/N2 selectivity results for 1,700 hours. Techno-economic analysis has shown that the post-combustion capture process using the membrane is promising for meeting DOE’s capture cost target set for 2025. For carbon capture from <1% CO2 concentration sources, we have elucidated the carrier saturation phenomenon. With reducing the CO2 concentration in the feed gas, both CO2 permeance and CO2/N2 selectivity increased. These were mainly due to more available free amine carriers for CO2 molecular transport at lower CO2 concentration conditions.