(125e) Performances and Stability of Pilot Scale Composite Pd and Pd-Au Membranes in Actual Coal Derived SynGas

It has been known for some time that composite palladium and palladium/alloy membrane separators and reactors are suited for the development of technologies for pre-combustion CO₂ sequestration and economical power generation and hydrogen production. However, most work in this area reported in the literature has been done in laboratories for proof-of-concept. The objective of the present work was to investigate the performance of Pd and Pd/Au membranes with a slip-steam from an actual coal gasifier. This presentation will discuss the testing results from National Carbon Capture Center supported by US DOE/NETL Engineering Design of Advanced H₂ – CO₂ Membrane Separations Program.

Composite Pd and Pd/Au porous stainless steel membranes with long-term chemical, thermal and mechanical stability at high temperatures and pressures with high hydrogen fluxes and high separation selectivity were prepared by WPI’s unique patented technologies. Three membranes having an area of more than 200 cm² (2.54 cm OD, 25.4 cm L) were tested at National Carbon Capture Center (NCCC) in Wilsonville, Alabama. The Syngas (H₂: 33%, N₂: 46%, CO: 7%, CO₂:7%, H₂O: 7%) was fed at a flow rate of 10 lbs/hr., at 120 to 160 psig, and 450°C. The H₂S concentration was reduced to lower than 1 ppm using two ZnO fixed-bed adsorbers. All three membranes showed an initial high hydrogen flux sufficient to meet the DOE Phase I target of 2 lbs/day under our current DOE Program. Two membranes showed a hydrogen flux decline down to 40% of the initial flux after 20 hours of exposure to the syngas stream but maintained stable at the lower flux for over 200 hours. The third membrane had a lower initial hydrogen flux and showed no initial decline and remained stable for over 150 hours. The hydrogen purity as high as 99.89% was obtained and stable for over 220 hours. It should be emphasized that such results were not available in the literature and represented a breakthrough in the application of large-scale composite Pd membranes using a slip-stream from an actual coal gasifier.

Composite Pd membranes prepared by the same method as those tested in NCCC were characterized in our laboratory. SEM analysis showed a uniform and smooth Pd layer with thickness in agreement with thickness determined by the gravimetric method.