Scale hydrogen transport membranes

Edlund DJ. Engineering scale-up for hydrogen transport membranes. In SammeUs AF, Mundschau MV, editors. Weinheim, Germany Wiley-VCH 2006. pp. 139-64. 

I 5 Engineering Scale-upfbr Hydrogen Transport Membranes... 

This book provides an extensive overview of current thinking on applications, materials issues, and scale-up considerations related to dense oxygen and hydrogen transport membranes. For a broad outlook, international contributions have been obtained from researchers in academia, industry and national laboratories. Readers new to the field should find ample information on membrane fundamentals. Advanced researchers should find many previously unpublished concepts and research results to help forward their work. Readers will be aided by the large number of references to the membrane literature and especially by the extensive references to the patent literature, which reflect the potential commercial applications of membranes. 

Evenson C., Scale-up of hydrogen transport membranes for IGCC and Euture Gen plants, Proc. of DOE Men/, Washington (USA), May 9-13,2011... 

Concurrently with the work on carbon dioxide and hydrogen sulfide at General Electric, Steigelmann and Hughes [27] and others at Standard Oil were developing facilitated transport membranes for olefin separations. The principal target was the separation of ethylene/ethane and propylene/propane mixtures. Both separations are performed on a massive scale by distillation, but the relative volatilities of the olefins and paraffins are so small that large columns with up to 200 trays are required. In the facilitated transport process, concentrated aqueous silver salt solutions, held in microporous cellulose acetate flat sheets or hollow fibers, were used as the carrier. 

In bench-scale tests, using hoUow-fiber membrane as support and a carrier concentration of 2 M the ethylene permeance was 4.6 X 10 barrer/cm with an ethylene partial pressure of 65 psia, while the selectivity C2H4/C2H6 was about 240. Same tests were carried out for separation of propylene from propane. The selectivity obtained was greater than 100 but this result was confirmed only at bench scale. In fact, in the large pilot system, the selectivity and flux dechned over some weeks due to loss of solvent and carrier and to the necessity of remove hydrogen from the feed gas to prevent reduction of Ag f carrier. Despite the result, this remains the first study on the use of facilitated transport membrane for gas separations on a pilot scale. 

Klmura et al. (J 2) reported progress toward applying facilitated transport membranes to industrial scale separations. They measured carbon dioxide and hydrogen sulfide permeabilities at industrially significant operating conditions (6.90 x io kPa COj, 363 03 K). Under these conditions, the authors determined that carbon dioxide transport is influenced by both diffusion and reaction rates. 

Polymer electrolyte fuel cell (PEFC) is considered as one of the most promising power sources for futurist s hydrogen economy. As shown in Fig. 1, operation of a Nation-based PEFC is dictated by transport processes and electrochemical reactions at cat-alyst/polymer electrolyte interfaces and transport processes in the polymer electrolyte membrane (PEM), in the catalyst layers consisting of precious metal (Pt or Ru) catalysts on porous carbon support and polymer electrolyte clusters, in gas diffusion layers (GDLs), and in flow channels. Specifically, oxidants, fuel, and reaction products flow in channels of millimeter scale and diffuse in GDL with a structure of micrometer scale. Nation, a sulfonic acid tetrafluorethy-lene copolymer and the most commonly used polymer electrolyte, consists of nanoscale hydrophobic domains and proton conducting hydrophilic domains with a scale of 2-5 nm. The diffusivities of the reactants (02, H2, and methanol) and reaction products (water and C02) in Nation and proton conductivity of Nation strongly depend on the nanostructures and their responses to the presence of water. Polymer electrolyte clusters in the catalyst layers also play a critical... 

Sjardin, M., Damen, K.J. and Faaij, A.P.C. (2006) Techno-economic prospects of small-scale membrane reactors in a future hydrogen-fuelled transportation sector. Energy, 31 (14), 2187-2219. 

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