Production of Hydrogen from Lpg
2.5.1. Processing Steps of Hydrogen Production from LPG
Conventional process for producing hydrogen from light hydrocarbons involves the following process steps:
• Feed preparation • Sulfur removal • Steam reforming • CO shift conversion • Autothermal reforming • Process gas cooling • Synthesis gas purification (PSA pressure swing absorption) [5]
2.5.1.1. Sulfur Removal LPG feed first passes through an ambient temperature sulfur adsorption vessel. The proprietary adsorbent in this vessel has been specifically designed to remove sulfur species native to LPG feeds as well as those sulfur compounds that are added as odorants for leak detection. The sulfur adsorbent has been proven effective in removing compounds ranging from H2S and mercaptans to thiophenes. Since sulfur is known to affect the performance of all reforming catalysts, removing the sulfur prior to entering the reforming section ensures the highest level of reforming catalyst performance and maximum catalyst life. [5]
2.5.1.2. Autothermal Reforming During the reforming step, LPG feed is converted into a hydrogen rich product stream. At the entrance of the reforming catalyst bed, the feed, air and steam are mixed in proportions that are chosen to maximize hydrogen production from the given feedstock. The conversion takes place over a bi-functional catalyst that promotes both partial oxidation and steam reforming reactions in the same catalyst bed. This results in a direct transfer of heat within the catalyst bed and efficient production of hydrogen. The direct transfer of heat also means the process is responsive to changes in hydrogen demand requirements. [5]
3. Hydrogen Purification Hydrogen purification is performed via the use of Pressure Swing Adsorption (PSA) technology. The PSA technology employed by HyRadix combines novel process hardware technology with proprietary adsorbents to attain a very high recovery of the product
Conventional process for producing hydrogen from light hydrocarbons involves the following process steps:
• Feed preparation • Sulfur removal • Steam reforming • CO shift conversion • Autothermal reforming • Process gas cooling • Synthesis gas purification (PSA pressure swing absorption) [5]
2.5.1.1. Sulfur Removal LPG feed first passes through an ambient temperature sulfur adsorption vessel. The proprietary adsorbent in this vessel has been specifically designed to remove sulfur species native to LPG feeds as well as those sulfur compounds that are added as odorants for leak detection. The sulfur adsorbent has been proven effective in removing compounds ranging from H2S and mercaptans to thiophenes. Since sulfur is known to affect the performance of all reforming catalysts, removing the sulfur prior to entering the reforming section ensures the highest level of reforming catalyst performance and maximum catalyst life. [5]
2.5.1.2. Autothermal Reforming During the reforming step, LPG feed is converted into a hydrogen rich product stream. At the entrance of the reforming catalyst bed, the feed, air and steam are mixed in proportions that are chosen to maximize hydrogen production from the given feedstock. The conversion takes place over a bi-functional catalyst that promotes both partial oxidation and steam reforming reactions in the same catalyst bed. This results in a direct transfer of heat within the catalyst bed and efficient production of hydrogen. The direct transfer of heat also means the process is responsive to changes in hydrogen demand requirements. [5]
3. Hydrogen Purification Hydrogen purification is performed via the use of Pressure Swing Adsorption (PSA) technology. The PSA technology employed by HyRadix combines novel process hardware technology with proprietary adsorbents to attain a very high recovery of the product
References: 2. Peters, M. S., K. D. Timmerhaus and R. E. West, Plant Design and Economics for Chemical Engineers, McGraw-Hill Professional, 2003. 3. Kimya Muhendisi, HydrogenProduction http://www.kimyamuhendisi.com/index.php?option=com_docman&task=doc_download&gid=170&Itemid=28, 2006. 4. Sinnot, R.K., ‘Chemical Engineering Design’, Elsevier, 4th Ed., 2005. 5. Unitel Technologies, Hydrogen Production, http://www.uniteltech.com/html/projects_clients.html, 2007. 6. Zittel, W., ‘Hydrogen Energy in the Sector’, Handling, Storage and Transport, http://www.hyweb.de/Knowledge/w-i-energiew-eng.html, 1996 7 8. Aksoylu, A.E., Baltacıoğlu, F.S., Gülyüz, B., and Önsan, Z.İ, ‘Low Temperature CO oxidation Kinetics over Activated Carbon Supported Pt-SnOx Catalyst’, Turk J. Chem, Vol.31, 2007. 9. Araya, P., Guerrero, S., Robertson, J. and Gracia, F.J., ‘Methane combustion over Pd-SiO2 catalysts with different degrees of hydrophobicity’, 2003. 10. Mukherjee, S., Hatalis, M.K., and Kothare M.V., ‘Water Gas Shift Reaction in a glass microreactor’, Catalysts Today, Vol.120, pp. 107-120, 2007 11 12. Gökaliler, F., Çaglayan, B.S., Önsan, Z.İ., and Aksoylu, A.E., ‘Hydrogen Production by autothermal reforming of LPG for PEM fuel cell applications’, Hydrogen Energy, 2008. 13. Chemical Engineering Beta, ‘Plant Cost Index’, 2008 http://www.che.com/pci/ APPENDIX A