Pre-Combustion Fuel Decarbonization with Hydrogen Separation Membranes

Integration of Pd or Pd alloy membranes with reforming or WGS reactors, for pre-combustion fuel de-carbonization, is attractive for the reduction in CO2 emissions. Recovery of CO2 at high pressure and high purity (>90 mol%) as well as carbon conversions in excess of equilibrium limits may be achieved using various process schemes [1,2]. CRI/Criterion is in the process of commercializing Pd and Pd-alloy membranes on sintered porous metal supports. The scope of the CRI/Criterion effort includes the development of membranes for sale to third parties in addition to the support of the Shell process development efforts. Successful evaluations of CRI/Criterion H2 separation membranes in membrane steam reformers and as high temperature membrane separators have been performed by CRI/Criterion [3], and by third parties [4]. Figure 1 shows an extended trial of a CRI/Criterion Pd membrane (15cm L x 2.5cm OD) separating H2 from a gas blend (40.1% H2, 41.6% H2O, balance N2) at 430oC and DP of 29 Bar. The membrane had excellent selectivity and flux stability for over 4000 hrs. The hydrogen purity was greater than 99 mol% for the entire test. Figure 2 shows H2 output vs. CO partial pressure for a CRI Pd membrane. The feed had similar composition to the output from a WGS reactor. As CO feed was increased, a portion of the CO2 feed was subtracted to keep a constant gas velocity profile. These data show that the CRI/Criterion membrane had no CO inhibition at 430oC and process conditions relevant to many fuel decarbonization applications. CRI/Criterion has produced membranes of this type as large as 2"OD by 48"L, by welding two separate 24"L sections. These membranes can be produced with a hydrogen permeance in the range of 50-70 [Nm3/m2.h.bar0.5]. Both the hydrogen flux and the separation selectivity are stable at temperatures of 300-500oC and differential pressures of 26-42 Bar. H2 purity of >99% has been demonstrated for periods exceeding 4000 hrs in high temperature gas separations. [1] Matzakos, A.N.; Wellington, S.L.; Mikus, T.; Ward, J.M.. U.S. Patent 6,821,501 B2, Nov. 23, 2004. [2] Clomburg et al.. U.S. Patent Application, US 2008/0179569 A1. [3] Engwall, E.; Saukaitis, J.; Joshi, M.; Matzakos, A.; Del Paggio, A.. Membrane steam reforming for H2 production, AIChE National Meeting, November 2007. [4] Sanchez, J.M; Marono, M.; Barreiro, M.M.. Separation of CO2 and H2 using palladium membranes (for integration in power generation with CO2 capture). EUROMEMBRANE Conference 2009.