Hydrogen is one of the most important chem. products and it is used in a wide variety of industrial fields including chem., petrochem., metallurgic and energy applications. Hydrogen demand in all of these fields is continuously growing. At present, hydrogen is mainly produced from fossil fuels via processes such as steam reforming, partial oxidn. and gasification. All of these processes lead to the prodn. of an H2-contg. gas stream (synthesis gas) from which hydrogen has to be sepd. Thin-film palladium membranes are one of the most promising technologies for the sepn. of hydrogen from synthesis gas. It involves some advantages over traditional sepn. methods like pressure swing adsorption (PSA), and over other membrane materials (polymeric, porous or dense ceramic), among which are 100% sepn. efficiency, high permeability and operating conditions compatible with upstream fuel conversion processes. In this work, palladium films were deposited above stainless steel porous supports using the electroless plating (ELP) technique. Two different geometries (disk sheet and tubes) were chosen for the supports, which both have a 0.1 m filter grade. Surface morphol. and cross-section were obsd. through SEM. For each membrane, film thickness was estd. both by wt. gain and by cross-section observation with SEM. A good agreement was found between the two values. The evolution of film thickness and morphol. for increasing ELP cycle no. was studied, as well as the influence of a previous phase of thermal oxidn. of the metallic substrate. Membranes were tested in an appropriate set up for nitrogen tightness in order to individuate local defects. The results showed that after only 4 cycles of deposition a uniform dense film of palladium with a thickness of about 10 m is obtained, but even after 6 cycles a small no. of defects still subsist, probably due to support of local morphol. discontinuities. Finally, the detailed design of a permeability testing unit is reported, including the fluid dynamic, thermal and mech. dimensioning, the selection of materials and equipment, and some safety considerations. The sketches of the two permeation cells (for the two different membrane geometries) are also reported.
Preparation of thin film Pd membranes for H2 separation from synthesis gas and detailed design of a permeability testing unit
PETARCA, LUIGI
2010-01-01
Abstract
Hydrogen is one of the most important chem. products and it is used in a wide variety of industrial fields including chem., petrochem., metallurgic and energy applications. Hydrogen demand in all of these fields is continuously growing. At present, hydrogen is mainly produced from fossil fuels via processes such as steam reforming, partial oxidn. and gasification. All of these processes lead to the prodn. of an H2-contg. gas stream (synthesis gas) from which hydrogen has to be sepd. Thin-film palladium membranes are one of the most promising technologies for the sepn. of hydrogen from synthesis gas. It involves some advantages over traditional sepn. methods like pressure swing adsorption (PSA), and over other membrane materials (polymeric, porous or dense ceramic), among which are 100% sepn. efficiency, high permeability and operating conditions compatible with upstream fuel conversion processes. In this work, palladium films were deposited above stainless steel porous supports using the electroless plating (ELP) technique. Two different geometries (disk sheet and tubes) were chosen for the supports, which both have a 0.1 m filter grade. Surface morphol. and cross-section were obsd. through SEM. For each membrane, film thickness was estd. both by wt. gain and by cross-section observation with SEM. A good agreement was found between the two values. The evolution of film thickness and morphol. for increasing ELP cycle no. was studied, as well as the influence of a previous phase of thermal oxidn. of the metallic substrate. Membranes were tested in an appropriate set up for nitrogen tightness in order to individuate local defects. The results showed that after only 4 cycles of deposition a uniform dense film of palladium with a thickness of about 10 m is obtained, but even after 6 cycles a small no. of defects still subsist, probably due to support of local morphol. discontinuities. Finally, the detailed design of a permeability testing unit is reported, including the fluid dynamic, thermal and mech. dimensioning, the selection of materials and equipment, and some safety considerations. The sketches of the two permeation cells (for the two different membrane geometries) are also reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
