Membrane technology for the intensification of gas separation processes- application to CO2 removal

Gas permeation processes have been initially seldom considered within a post-combustion carbon dioxide capture framework. In this presentation, the key performances (selectivity, permeability) of different membrane materials including recently reported results, are reviewed. The process design characteristics of a single stage membrane unit are studied and energy constraints are analysed as a function of operating conditions and membrane materials performances. The interest of multistage and hybrid systems will be illustrated.
Today, the best currently available technology is absorption in a chemical solvent (such as monoethanolamine, MEA) and is considered as a reference for post combustion capture. Over the past three decades, membrane contactors have been considered as an innovative alternative to conventional gas-liquid contactors such as packed columns. A technology commonly proposed is the use of hollow fibre membrane contactor (HFMC), developing sizeable interfacial areas, which could potentially lead to significant reduction in equipment volume. The estimation of the performance of this technology within the context of relevant industrial conditions, called for rigorous process models that could be applicable over a wide domain, covering both laboratory and industrial conditions. Transfer models of different complexities were studied and compared, i.e. 1D and 2D isothermal single-component, 1D and 2D adiabatic multi-component.
The gasification of carbonaceous fuels leads to a syngas at several tens of bars, mainly containing hydrogen and acid gases (CO2, H2S). The acid gases can be separated from the hydrogen by physical absorption in non-aqueous solvents. The purified hydrogen is then used as a decarbonized fuel. The reference gas-liquid contactor technology in acid gas absorption is the packed column. In this presentation, the potentialities of membrane contactors using physical solvent for both absorption and regeneration steps will be discussed. Theoretical argument as well as experiments show that dense membranes based on superpermeable and mechanically resistant polymers could offer promising performances, owing to their capacity to simultaneously prevent wetting effects, sustain a high transmembrane pressure and offer process intensification possibilities.