2 Stage Hybrid Membrane Process for CO2 Capture from Flue Gas in Power Plants
A 2-stage enriching cascade membrane process for capturing CO2 from flue gas in a power plant without air sweep
Post-combustion carbon capture (PCC) provides an option to mitigate CO2 emissions from large stationary sources, followed by compression, transport, and geological sequestration; the captured CO2 may be used for enhanced oil recovery. Because of the system compactness and energy efficiency, CO2-selective membranes have been suggested to be a promising candidate for PCC. Typically, a stripping cascade is not suitable for separation requiring high product purity and recovery simultaneously. An enriching cascade is capable of achieving at least 90% CO2 recovery with 95% purity, but the capture cost and energy penalty are unfavorable. The air-sweep process, however, utilizes the combustion air as a “free” driving force, thereby resulting in a reduced capture cost.
Researchers at The Ohio State University, led by WS Winston Ho, have developed a 2-stage enriching cascade membrane process for capturing CO2 from flue gas in a power plant. In the process, the flue gas flows to the first enriching membrane stage using a membrane with high CO2 permeance and low CO2/N2 selectivity. The CO2-enriched permeate gas then flows to the second enriching membrane stage employing another membrane with high CO2/N2 selectivity but modest CO2 permeance. This stand-alone hybrid membrane process shows a comparable capture cost to the state of the art membrane processes using power plant combustion air as membrane sweep gas. More importantly, the risk of affecting the power plant efficiency caused by air sweep is eliminated.