Hydrogen Permeability Of A Palladium Membrane Module

The increased demand for pure hydrogen gas in recent years in many sectors, rangingfrom petroleum processing, materials treatment to renewable energy related applications, hasled to a revival of interest in economical hydrogen production technologies. Hydrogen energyis looked upon as a savior in combating the deterioration of the global environment, as meansof securing energythat is independent of the dwindling fossil fuel supplyand an approach to afuture lasting supply of energy resource. Most of the world's hydrogen is generated by steamreforming or partial oxidation of natural gas in parallel fixed bed reactors within hugetop-fired or side-fired furnaces, coupled with pressure swing adsorption (PSA) for hydrogenpurification. Hydrogen separation accounts for a large fraction of energy expenditure andcapital investment in the hydrogen production process. The most widely used technology forhydrogen purification is PSA. Palladium and its alloy membranes have attracted growinginterests for their capability to separate ultra-pure hydrogen from gaseous mixtures. They canalso be integrated with chemical reactors where chemical reaction and hydrogen separationoccur simultaneously to simplify the hydrogen production process. Various membranefabricated methods, performance and membrane reactors have been researched. This paperwas comprehensivelyinvestigated a new palladium membrane module performance.Membrane modules, consisting of membrane foil, porous stainless steel substrate, testframe and flange were assembled and tested in an electrically heated vessel. Instantaneoushydrogen permeation flux was measured. Influences of operation conditions on membraneperformance were examined. Microstructure and morphology of the membrane surfaces werecharacterized by scanning electron microscopy. For the conditions investigated, permeationfluxes of the membrane module increased with increasing the hydrogen pressure in the vesselside and increasing the membrane module temperature and decreasing the hydrogen exitpartial pressure by sweep gas. The permeation fluxes increased with decreasing membranethickness. However, the thickness was less than 10μm was not suitable for fabricated on the porous stainless steel. The permeation factor of the module increases with increasing thehydrogen pressure in the vessel side and decreasing the membrane module temperature. Withdecreasing the hydrogen exit partial pressure by sweep gas, the membrane module permeationflux increased, while the permeation factor decreased. It was observed that for operationtemperature higher than 755 K, 0.2?m grade porous 316L stainless steel material was notsuitable for being used as membrane module substrate and the surface of porous stainless steelwas changed. For temperature around 869 K -943 K, 0.5 ?m grade porous 316Lstainless steel material without any pretreatment can be used as membrane module substrate. Pretreatmentof the 0.5 ?m grade substrate helped to smooth membrane foil surface. However, it changedthe surface structure of the material and led to permeabilitydecrease.