The vision of an “hydrogen economy” with the use of hydrogen as an energy carrier will require increasing hydrogen production by more than an order of magnitude of the current production levels . Hydrogen can be produced from a variety of sources. Fossil fuels may be used to produce hydrogen by first converting their fuel value to gas phase by reaction with steam, oxygen or air (gasification/reforming) followed by hydrogen enrichment and separation through the use of fuel processors [2–4].
The choice of an hydrogen separation technology often depends on the hydrocarbon feedstock used and the resulting synthesis gas composition. PSA( pressure swing adsorption) has been the most commonly used technology for producing high-purity hydrogen as product from steam reforming processes. PSA is based on an adsorbent bed that captures the impurities in the syngas stream at high pressure and then releases the impurities at low pressure. For this purpose multiple beds are used simultaneously so that a continuous stream of hydrogen at purity up to 99.9% may be produced recovering up to the 95% of the hydrogen present in the reformer syngas .
Our work focuses on an hydrogen production system starting from natural gas for refilling stations. The overall process consists in an hydrogen production unit (reforming and WGS stage), a purification unit (PSA stage), and a compression and refrigeration unit with the recirculation of PSA exhausts in the burner. In our previous works a comparison between two clean-up methods (CO preferential oxidation, CO-PROX, and COselective methanation, CO-SMET) for a refilling station (not integrated system) and for an Auxiliary Power Unit (APU, FC integrated system) were investigated [6,7]. Now, the final purpose is to replace CO-PROX and CO-SMET units with a PSA unit to obtain pure hydrogen. Besides, we want investigate in the thermal conditions of the system varing the PSA hydrogen recovery level from 70% to 95% for different reforming pressure ranging from 5 to 30 bar. The PSA exhaust contains a noticeable part of the produced hydrogen, that can be sent to the integrated burner (I-BR) to sustain the reforming reaction. Passing from 70% to 95% of PSA hydrogen recovery level, there is a thermal neutral point (TNP) above that that the system is not self-sustained. In these configurations part of the total natural gas feed to the reforming is shifted to the I-BR to supply the reforming reaction. Whereas below the TNP not all the recirculated fuel is required from the I-BR. Therefore the remaining part of the fuel is send to another burner (BR) that produces waste gases to preheat the air required to the I-BR. The TNP moves in the range of hydrogen recovery with the refroming pressure variation.
Moreover, we are completing the simulations with an hydrogen compression and refrigeration stage (ammonia plant) in order to give a full overview of a refilling station from the production to the storage of the hydrogen. The sensitivity analysis of the reforming process as a fuction of the working pressure, coupled with an economical analysis of the different possible configurations will be presented in order to estabilish the best configuration in terms of reforming pressure and hydrogen recovery.
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 G. Ercolino, M.A. Ashraf, V. Specchia, S. Specchia. Performance evaluation and comparison of fuel processors integrated with PEM fuel cell based on steam or autothermal reforming and on CO preferential oxidation or selective methanation. Applied Energy 143 (2015) 138–153.
This work was funded by the Italian Ministry of Education, University and Research (MIUR, PRIN 2010–2011) within the project IFOAMS (“Intensification of catalytic processes for clean energy, low-emission transport and sustainable chemistry using open-cell FOAMS as novel advanced structured materials”, protocol no.2010XFT2BB).