Experimental and Numerical Analysis of a Pd–Ag Membrane Unit for Hydrogen Isotope Recovery in a Solid Blanket

Abstract

The interest of the fusion community in Pd–Ag membranes has grown in the last decades due to the high value of hydrogen permeability and the possibility of continuous operation, making it a promising technology when a gaseous stream of hydrogen isotopes must be recovered and separated from other impurities. This is the case of the Tritium Conditioning System (TCS) of the European fusion power plant demonstrator, called DEMO. This paper presents an experimental and numerical activity aimed at (i) assessing the Pd–Ag permeator performance under TCS-relevant conditions, (ii) validating a numerical tool for scale-up purposes, and (iii) carrying out a preliminary design of a TCS based on Pd–Ag membranes. Experiments were performed by feeding the membrane with a He–H2 gas mixture in a specific feed flow rate ranging from 85.4 to 427.2 mol h−1 m−2. A satisfactory agreement between experiments and simulations was obtained over a wide range of compositions, showing a root mean squared relative error of 2.3%. The experiments also recognized the Pd–Ag permeator as a promising technology for the DEMO TCS under the identified conditions. The scale-up procedure ended with a preliminary sizing of the system, relying on multi-tube permeators with an overall number ranging between 150 and 80 membranes in lengths of 500 and 1000 mm each.

On the Scalability of a Membrane Unit for Ultrapure Hydrogen Separation

“…The single-tube frame allows precise control of the feed and permeate flow rate, and three pressure transducers ensure pressure monitoring on the lumen and shell sides. The membrane is directly heated by the Joule effect, and its temperature is monitored at three points with thermocouples installed on the membrane's outside wall, thus providing a detailed temperature profile (refer to the work of Narcisi et al [23] for further details).…”

“…The possibility of exploiting Pd-based membranes for the aforementioned tasks was extensively investigated at the ENEA Frascati laboratories. Several experiments were conducted on a single-tube Pd-Ag permeator to test this technology for the purification of hydrogen streams [23,24] and the recovery of hydrogen isotopes from water through water gas shift and isotope swamping reactions [25,26]. The test section consists of the unsupported membrane, which is 500 mm long and characterized by a diameter of 10 mm and a thickness of around 100 µm.…”