Simulations of membrane separation were performed for two alternative processes for CO2 removal from an exhaust gas stream at a natural gas fired power plant. One process considered is an integrated membrane separation with pressurized gas (16.5 bar) rich in CO2 (10 Vol %), while the other alternative solution is a process for CO2 capture from tail-end flue gas where the content Of CO2 is low (4 vol %) and gas is released at 1 bar. A gas stream of 700 000 Nm(3)/h is considered for both cases. Flux data obtained for a fixed-site-carrier poly(vinylamine) membrane developed within the research group at NTNU were used. This membrane has moderate C02 flux but very high selectivity in favor Of CO2. A favorable process design with a single-stage unit without the extra need for compression, and also use of a sweep gas to meet the process specifications, was recommended for the pressurized gas. For the flue gas lean in C02, the driving forces are too low for separation unless both a compression of the feed gas (-> 4 bar) and a vacuum pump on the permeate side are used. Also, in this case a small fraction of the sweep gas on the permeate side is recommended.