Abstract
Membrane technology can be used for both post combustion carbon dioxide capture and acidic gas sweetening and dehydration of natural gas. These processes are especially suited for polymeric membranes with polyether functionality, because of the high affinity of this species for both H2O and CO2. Here, both crosslinked polyethylene glycol diacrylate and a polyether-polyamide block copolymer (PEBAX 2533©) are studied for their ability to separate CO2 from CH4 and N2 under single and mixed gas conditions, for both dry and wet feeds, as well as when 500 ppm H2S is present. The solubility of gases within these polymers is shown to be better correlated with the Lennard Jones well depth than with critical temperature. Under dry mixed gas conditions, CO2 permeability is reduced compared to the single gas measurement because of competitive sorption from CH4 or N2. However, selectivity for CO2 is retained in both polymers. The presence of water in the feed is observed to swell the PEG membrane resulting in a significant increase in CO2 permeability relative to the dry gas scenario. Importantly, the selectivity is again retained under wet feed gas conditions. The presence of H2S is observed to only slightly reduce CO2 permeability through both membranes.
Highlights
Post combustion carbon dioxide capture requires the removal of carbon dioxide from flue gas streams saturated with water
Membranes consisting of cross-linked polyethylene glycol (PEG) and PEBAX 2533 where studied for cast in 1-butanol and Barrer (CO2) and H2 O
Single gas measurements indicated that both membranes were selective for CO2 against CH4 and
Summary
Post combustion carbon dioxide capture requires the removal of carbon dioxide from flue gas streams saturated with water. There is the potential to combine both natural gas sweetening and dehydration in a single membrane process, care would be required to ensure pressure conditions are suitable to avoid both methane and carbon dioxide hydrates; and to avoid corrosion in the permeate stream piping. The use of cross linking, or the incorporation of polyamide blocks within the structure, as commercialised through the PEBAX© series of block copolymers, reduces the overall crystallinity, with values of 14% to 51% reported for PEBAX systems [17] In this investigation, the performance of cross-linked PEG and PEBAX 2533 in single and mixed gas feeds of CO2 and water are reported. The effect of competitive sorption on the permeability of CO2 , water, N2 , CH4 and H2 S is studied, to identify the potential of these two polymeric membranes for post combustion carbon capture and for simultaneous removal of both acid gases and water from natural gas
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