Definition^1 :

Gas mixtures can be effectively separated by synthetic membranes made from polymers such as polyamide or cellulose acetate, or from ceramic materials.

While polymeric membranes are economical and technologically useful, they are bounded by their performance, known as the Robeson limit (permeability must be sacrificed for selectivity and vice versa). This limit affects polymeric membrane use for CO2 separation from flue gas streams, since mass transport becomes limiting and CO2 separation becomes very expensive due to low permeabilities. Membrane materials have expanded into the realm of silica, zeolites, metal-organic frameworks, and perovskites due to their strong thermal and chemical resistance as well as high tunability (ability to be modified and functionalized), leading to increased permeability and selectivity. Membranes can be used for separating gas mixtures where they act as a permeable barrier through which different compounds move across at different rates or not move at all. The membranes can be nanoporous, polymer, etc. and the gas molecules penetrate according to their size, diffusivity, or solubility.

Fundamentals of CO2 membranes^2

Calculation :

An average CO2 concentration in flue gases is calculated (Flue_gas_capture model) for the global energy mix, then the capture technology price is recalculated taking into account this variations.

^1: Membrane gas separation, Wikipedia, https://en.wikipedia.org/wiki/Membrane_gas_separation ^2: Passive CO2 Separation Membranes for Hot Flue Gases, https://www.netl.doe.gov/sites/default/files/2018-12/M-Merrill-Luna-Passive-Separation-Membranes_Aug%202018.pdf ^3: A sequential approach for the economic evaluation of new CO2 capture technologies for power plants, https://www.sciencedirect.com/science/article/pii/S1750583618307461?via%3Dihub