Experimental Demonstration of Advanced Palladium Membrane Separators for Central High Purity Hydrogen Production
The overall objectives for this project were to: (1) confirm the high stability and resistance of a PdCu trimetallic alloy to carbon and carbide formation and, in addition, resistance to sulfur, halides, and ammonia; (2) develop a sulfur, halide, and ammonia resistant alloy membrane with a projected hydrogen permeance of 25 m{sup 3}m{sup -2}atm{sup -0.5}h{sup -1} at 400 C and capable of operating at pressures of 12.1 MPa ({approx}120 atm, 1750 psia); and (3) construct and experimentally validate the performance of 0.1 kg/day H{sup 2} PdCu trimetallic alloy membrane separators at feed pressures of 2 MPa (290 psia) in the presence of H{sub 2}S, NH{sub 3}, and HCl. This project successfully increased the technology readiness level of palladium-based metallic membranes for hydrogen separation from coal-biomass gasifier exhaust or similar hydrogen-containing gas streams. The reversible tolerance of palladium-copper (PdCu) alloys was demonstrated for H{sub 2}S concentrations varying from 20 ppmv up to 487 ppmv and NH{sub 3} concentrations up to 9 ppmv. In addition, atomistic modeling validated the resistance of PdCu alloys to carbon formation, irreversible sulfur corrosion, and chlorine attack. The experimental program highlighted two key issues which must be addressed as part of future experimental programs: (1) tube defects and (2) non-membrane materials of construction. Four out of five FCC PdCu separators developed leaks during the course of the experimental program because {approx}10% of the alloy tubes contained a single defect that resulted in a thin, weak point in the tube walls. These defects limited operation of the existing tubes to less than 220 psig. For commercial applications of a PdCu alloy hydrogen separator under high sulfur concentrations, it was determined that stainless steel 316 is not suitable for housing or supporting the device. Testing with sulfur concentrations of 487 {+-} 4 ppmv resulted in severe corrosion of the stainless steel components of the separators. The project identified an experimental methodology for quantifying the impact of gas contaminants on PdCu alloy membrane performance as well as an atomistic modeling approach to screen metal alloys for their resistance to irreversible sulfur corrosion. Initial mathematical descriptions of the effect of species such as CO and H{sub 2}S were developed, but require further experimental work to refine. At the end of the project, an improvement to the experimental approach for acquiring the necessary data for the permeability model was demonstrated in preliminary tests on an enhanced PdCu separator. All of the key DOE 2010 technical targets were met or exceeded except for the hydrogen flux. The highest flux observed for the project, 125 ft{sup 3}ft{sup -2}h{sup -1}, was obtained on a single tube separator with the aforementioned enhanced PdCu separator with a hydrogen feed pressure of 185 psig at 500 C.
- Research Organization:
- United Technologies Corporation, Farmington, CT (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-07NT43055
- OSTI ID:
- 1000469
- Country of Publication:
- United States
- Language:
- English
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