Author: Pietro Brazzale
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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In the framework of the SFR (Sodium-cooled Fast Reactors), the management of tritium contamination in sodium circuits and the control of its release in atmosphere is fundamental. In order to capture and recover the tritium, it is necessary to maintain a certain amount of hydrogen dissolved in the liquid sodium stream. The hydrogen injection by permeation through nickel dense membranes has been proposed to provide a continuous hydrogen intake to liquid sodium stream, thus allowing the desired hydrogen concentration to be reached. Similar nickel-based membranes have been developed in the past for SFR (i.e. hydrogen-meters), but a lack of knowledge and applications is found for what concerns the hydrogen injection by permeation. In this study, an original permeator prototype has been designed and an experimental activity at pilot-scale has been carried out on an experimental sodium loop, under different operating conditions (temperature: 375°C-450°C; hydrogen supply partial pressures: 5 kPa-28 kPa). A dedicated measurement system, based on the gas chromatography on the retentate side, coupled to the hydrogen detection inside sodium (through a dedicated hydrogen-meter using mass spectrometry), has provided an accurate estimation of the hydrogen permeation flowrate. Tests are carried out for both a gas-vacuum and a gas-sodium configuration: in both cases, the global hydrogen permeation flowrate depends linearly on the square root of the hydrogen partial pressure in the feed side up to 20 kPa, thus demonstrating that the process in this range is limited by the hydrogen diffusion inside the nickel membrane. In particular, the presence of sodium in the permeate side does not affect significantly the whole mass transfer process. The results, compared to the permeation theoretical laws, provide an experimental permeability coefficient, specific to the prototype geometry and configuration. Comparison to values from the literature results for small nickel samples, showed that some metal-lattice phenomenon, probably linked to the membranes deformation by cold-working, could affect the hydrogen permeation in this study. In fact, slightly higher permeation coefficient with a lower activation energy is found here if compared to the literature. Finally, the experimental process has been successfully validated, thus demonstrating the feasibility of this application at the pilot-scale. An analytical 1D model has been set up with a multi-physics approach, in order to assess the radial hydrogen mass transfer in steady conditions over three physical domains, including gas, nickel and liquid sodium. It includes benchmark literature correlations for the convective mass transfer inside gas and sodium phase in tubular geometry, the Sieverts law for the H-Ni and H-Na equilibrium, coupled to the Richardson's law for the hydrogen permeation through the nickel membrane, assumed to be diffusion-limited. CFD simulations, performed in a 2D axial-symmetric geometry with the software Comsol Multiphysics, have provided a better comprehension of the transport phenomena taking place and have confirmed the results of the straightforward 1D model under certain conditions, specific to the experimental prototype. Finally, the experimental results have shown a good agreement with the 1D model and CFD simulations in the whole temperature interval and up to a hydrogen partial pressure of 20 kPa. By resuming all the elements provided by this study, both at the experimental and numerical stage, a single equation law has been defined to describe the prototype performance and to enhance the industrial scale-up design activity.
Author: Joseph Llewellyn McGhee
Publisher:
ISBN:
Category : Osmosis
Languages : en
Pages : 36
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Author: Mehrooz Zamanzadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Hemant B. Gala
Publisher:
ISBN:
Category : Hydrogen
Languages : en
Pages : 186
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Author: McGhee Joseph Llewellyn
Publisher: Wentworth Press
ISBN: 9780526626298
Category : History
Languages : en
Pages : 28
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This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.
Author: F. Waelbroeck
Publisher:
ISBN:
Category : Kirkendall effect
Languages : en
Pages : 214
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The objectives of the project were to build pilot scale hydrogen separation systems for use in a gasification product stream. This device would demonstrate fabrication and manufacturing techniques for producing commercially ready facilities. The design was a 2 lb/day hydrogen device which included composite hydrogen separation membranes, a water gas shift monolith catalyst, and stainless steel structural components. Synkera Technologies was to prepare hydrogen separation membranes with metallic rims, and to adjust the alloy composition in their membranes to a palladium-gold composition which is sulfur resistant. Chart was to confirm their brazing technology for bonding the metallic rims of the composite membranes to their structural components and design and build the 2 lbs/day device incorporating membranes and catalysts. WRI prepared the catalysts and completed the testing of the membranes and devices on coal derived syngas. The reactor incorporated eighteen 2'' by 7'' composite palladium alloy membranes. These membranes were assembled with three stacks of three paired membranes. Initial vacuum testing and visual inspection indicated that some membranes were cracked, either in transportation or in testing. During replacement of the failed membranes, while pulling a vacuum on the back side of the membranes, folds were formed in the flexible composite membranes. In some instances these folds led to cracks, primarily at the interface between the alumina and the aluminum rim. The design of the 2 lb/day device was compromised by the lack of any membrane isolation. A leak in any membrane failed the entire device. A large number of tests were undertaken to bring the full 2 lb per day hydrogen capacity on line, but no single test lasted more than 48 hours. Subsequent tests to replace the mechanical seals with brazing have been promising, but the technology remains promising but not proven.
Author: Yang Cao
Publisher:
ISBN:
Category :
Languages : en
Pages : 328
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"The effects of Ni, Pd and Pd77Ag23 alloy membrane microstructures on hydrogen permeation have been investigated using the electrochemical permeation method. Deformation, annealing and electrodeposition have been used to modify the membrane microstructure." --
Author: Abdulkadir Altunoglu
Publisher:
ISBN:
Category : Gases
Languages : en
Pages : 0
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and hydrogen permeability. Electrochemical hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.
