Medal membranes

Removal of carbon dioxide is the only membrane-based natural gas separation process currently practiced on a large scale—more than 200 plants have been installed, some very large. Most were installed by Grace (now Kvaerner-GMS), Separex (UOP) and Cynara and all use cellulose acetate membranes in hollow fiber or spiral-wound module form. More recently, hollow fiber polyaramide (Medal) membranes have been introduced because of their higher selectivity. 

Figure 7.4 Air Liquide/Medal membrane unit replacement of amine scrubbing towers (used with permission).

The syngas in the C02 Absorber overhead stream is water-washed and fed to a MEDAL membrane unit. The membrane feed gas is sent to a coalescing filter to remove liquids and is preheated before is enters the permeator. In the permeator, syngas is separated into a hydrogen-rich permeate and the syngas product. The operation of the membrane unit is very simple. The driving force for separation is the difference in partial pressure between the hydrogen in the feed gas and that of the permeate. 

Medal Membrane Separation System brochure, Du Pont-Air Liquide, 1989. 

Air Products and Chemicals Inc. incorporated Separex in 1988. Air Liquide and DuPont created a dedicated joint venture, i.e. Medal (MEmbrane Dupont Air Liquide), in 1989 which became a fully owned subsidiary of Air Liquide the following year." ... 

A Medal membrane unit was operated at the end of the 1990s to process... 

Air Liquide, MEDAL Hydrogen Membrane, available at http //www.medal.airliquide.com/en/ membranes/hydrogen/index.asp (accessed July 2007). 

W. G. Grot, Discovery and Development ofNafion Pefluorinated Membranes, The Castner Medal Lecture, 3rd London International Clilorine Symposium, June, 1985. 

New materials with improved CO2/CH4 separation selectivity and membrane stability under realistic NG conditions have been developed however, even after three decades of development, only three membrane material types have been commercialized cellulose acetate-based Separex (Honeywell s UOP), Cynara (Cameron) membranes, polyimide-based membranes from Medal (Air Liquide) and Ube, and per-fluoropolymer-based Z-top membranes from Membrane Technology and Research, Inc. (MTR). The key reasons for the selection of the desired polymer for commercialization are the cost of material, ease of fabrication into commercially viable form, effect of impurities on membrane performance, and gas selectivity under realistic feed conditions. 

Medal, T.N., Rosenkilde, M.M., and Schwartz, T.W. (1998) Selective recognition of the membrane-bound CX3C chemokine, fractalkine, by the human cytomegalovirus-encoded broad-spectrum receptor US28. FEBS Letters, 441, 209-214. 

Fraile-Ramos, A., Pelchen-Matthews, A., Medal, T.N., Browne, H., Schwartz, T.W., and Marsh, M. (2002) Localization of HCMV UL33 and US27 in endocytic compartments and viral membranes. Traffic (Copenhagen, Denmark), 3, 218-232. 

W.G. Grot, Discovery and Development of Nafion Perfluorinated Membranes The SCI. Castner Medal Lecture. In K. Wall (ed.). Modem Chlor-Alkali Technology, Ellis Horwood Ltd, Chichester, Vol. 3, (1986), p. 122. 

In 1996 Medal launched a new generation of hollow-fiber permeation membranes, based on polyimides. ... 

Air Liquide, with the MEDAL polyimide and high selectivity polyaramide membranes. 

So far, many attempts have been made to develop the polyimide gas separation membranes. At present, the polyimide membranes are commercialized by several manufacturers Medal (Air Liquide), IMS (Praxair), and UBE Industries Ltd (Baker, 2002). 

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