Power plant post-combustion carbon dioxide capture: An opportunity for membranes

Carbon dioxide capture from power plant flue gas and subsequent sequestration is expected to play a key role in mitigating global climate change. Conventional amine technologies being considered for separating CO₂ from flue gas are costly, energy intensive, and if implemented, would result in large increases in the cost of producing electricity. Membranes offer potential as an energy-efficient, low-cost CO₂ capture option. Recently, working with the U.S. Department of Energy (DOE), we have developed membranes with CO₂ permeances of greater than 1000gpu and a CO₂/N₂ selectivity of 50 at 30°C. This permeance is ten times higher than commercial CO₂ membranes and the selectivity is among the highest reported for non-facilitated transport materials. These membranes, in combination with a novel process design that uses incoming combustion air as a sweep gas to generate driving force, could meet DOE CO₂ capture cost targets. Under these conditions, improving membrane permeance is more important than increasing selectivity to further reduce the cost of CO₂ capture from flue gas. Membrane cost and reliability issues will be key to the eventual competitiveness of this technology for flue gas treatment.