Membrane processes single-stage separation

Some of the available membrane separation processes can already be applied on an industrial scale. Hence, inorganic ceramic membranes (zeolites and their derivatives, e.g. silico aluminophosphates), organic polymer membranes and facilitated transport membranes, which rely on a carrier molecule with high CO2 affinity to achieve selective CO2 transport (such as metallic ions or liquid amines), have been used in separating CO2 from flue gas in post-combustion. As single-stage separation with these membranes is still difficult, new membrane materials are being developed [1]. Typically, the initial separation of carbon dioxide accounfs for 60-80% of the total cost of CO2 sequestration [24,25]. 

As a general rule, gas separation by membranes is most attractive in applications where a product purity of 95% or lower is acceptable or the feed flow-rate is not too high. As the required purity approaches 100%, the membranes become less cost effective than other separation processes. This is particularly true with single-stage units. For more stringent applications, some traditional separation processes are preferred or required to integrate with the membrane system. 

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