2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 10: Battery, Recycling, Environmental, Mining
| Editors: | Kongoli F, Kumar V, Aifantis K, Pagnanelli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 220 pages |
| ISBN: | 978-1-987820-54-6 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Development of an optimized process for recovery and reuse of spent membranes for hydrogen separation
Francesca Pagnanelli1; Emma Palo2; Emanuela Moscardini3; Ludovica Baldassari4; Annarita Salladini5; Gaetano Iaquaniello6; Luigi Toro7;1SAPIENZA UNIVERSITY OF ROME, Rome, Italy; 2KT - KINETICS TECHNOLOGY S.P.A., Roma, Italy; 3UNIVERSITA , Roma, Italy; 4ECO RECYCLING, SPIN OFF SPIENZA UNIVERSITY, Civita Castellana, Italy; 5PROCESSI INNOVATIVI S.R.L., Roma, Italy; 6KT - KINETICS TECHNOLOGY S.P.A., Rome, Italy; 7SAPIENZA UNIVERSITY, Rome, Italy;
Type of Paper: Regular
Id Paper: 333
Topic: 7
Abstract:
The research into new technologies for the production of hydrogen was motivated by the growth in hydrogen’s demand. The production of hydrogen with membrane reactors is one of the most promising areas. Membrane reactors have a remarkable capacity to separate hydrogen through the semipermeable membrane, meanwhile it is produced. This mechanism allows shifting the chemical equilibrium towards reaction products in order to obtain higher conversions of the hydrocarbon feedstock, at lower temperatures, thereby increasing the energy efficiency of the conversion process.
The purpose of this work is to identify an optimized process for the recovery of the end-of-life membranes based on palladium and silver and prepared from substrates of stainless steel (since this particular configuration seems to be the most promising in terms of hydrogen recovery, purity and for a potential scale-up). In fact, these membranes have a prohibitive cost (up to 10,000 €/m2) that doesn’t allow them to be industrially employed. A potential recovery and recycling process of the main elements constituting the membrane can potentially contribute to a significant reduction in their unit production cost.
A hydrometallurgical process was then optimized in order to achieve the following main objectives: maximizing the dissolution of the damaged selective layer that is composed of precious metals (Pd-Ag) and keeping the metallic support intact, which will be retrieved and used for a new selective layer deposition.
An experimental campaign on laboratory scale was performed to test different leaching agents, reagents concentration and operating conditions (time and temperature of leaching) in order to define the optimal process conditions.
In particular, thiosulfate, thiourea and hydrochloric acid were tested for leaching but the best dissolution was achieved with nitric acid in an oxidizing environment. By this way, it was possible to obtain yields of palladium and silver dissolution of 42.6% and 72.5%, respectively, along with the simultaneous dissolution of the barrier of TiN (89.8%). After leaching tests the solid residues of membranes were analyzed by a Scanning Electron Microscope (SEM) to confirm the integrity of the metallic supports.
On the base of laboratory results a micropilot scale reactor was constructed allowing the external leaching of integer tubular membranes by pumping a thermostated solution with optimized composition. On the base of this microscale results and a fluido-dynamic analysis the scale up of the leaching reactor was performed (25 L).
A preliminary economic evaluation confirmed that such type of process could help to reduce of 50% the cost of the membrane per m2.