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Investigations and countermeasures for deactivation of hydrogen recombination catalyst at hamaoka units 4 and 5 / Toru Kawasaki in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 5 (Mai 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 5 (Mai 2011) . - 05 p. Titre : Investigations and countermeasures for deactivation of hydrogen recombination catalyst at hamaoka units 4 and 5 Type de document : texte imprimé Auteurs : Toru Kawasaki, Auteur ; Motohiro Aizawa, Auteur ; Hidehiro Iizuka, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Catalysts  Gas  turbines  Heat  treatment  Hydrogen  production  Organic  compounds  Sealing  materials  Silicon Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The hydrogen concentration in the outlets of off-gas recombiners increased at Hamaoka Units 4 and 5, and their reactors could not continue the startup operations. Therefore, we investigated why the recombination reactions were deactivated and we selected appropriate countermeasures for both plants. Two types of deactivation mechanisms were found from our investigations. The first cause was the decrease in the active surface area of alumina as support material due to dehydrative condensation. The other cause was the catalyst being poisoned by organic silicon compounds. Organic silicon was introduced from the organosilicon sealant used at the junctions of low-pressure turbines. We also found that a boehmite rich catalyst was deactivated more easily by organic silicon than gamma alumina because boehmite had numerous hydroxyl groups. Finally, we estimated that the deactivation of hydrogen recombination catalysts was caused by two combined factors; these were the characteristics of boehmite as the ingredient of catalysts support and the organic silicon poisoning the catalyst surface. As countermeasures, the boehmite was changed into more stable gamma alumina by adding heat treatment in a hydrogen atmosphere at 500°C for 1 h, and the source of organic silicon, organosilicon sealant, was removed. The improved catalysts were applied at Hamaoka Units 4 and 5. Moreover, the linseed oil that used to be used at the plants was applied again as sealant in the low-pressure turbine casing instead of organosilicon sealant. As a result of the application of these countermeasures, the reactors could be started without increasing the hydrogen concentration at these plants. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Investigations and countermeasures for deactivation of hydrogen recombination catalyst at hamaoka units 4 and 5 [texte imprimé] / Toru Kawasaki, Auteur ; Motohiro Aizawa, Auteur ; Hidehiro Iizuka, Auteur . - 2012 . - 05 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 5 (Mai 2011) . - 05 p. Mots-clés : Catalysts  Gas  turbines  Heat  treatment  Hydrogen  production  Organic  compounds  Sealing  materials  Silicon Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The hydrogen concentration in the outlets of off-gas recombiners increased at Hamaoka Units 4 and 5, and their reactors could not continue the startup operations. Therefore, we investigated why the recombination reactions were deactivated and we selected appropriate countermeasures for both plants. Two types of deactivation mechanisms were found from our investigations. The first cause was the decrease in the active surface area of alumina as support material due to dehydrative condensation. The other cause was the catalyst being poisoned by organic silicon compounds. Organic silicon was introduced from the organosilicon sealant used at the junctions of low-pressure turbines. We also found that a boehmite rich catalyst was deactivated more easily by organic silicon than gamma alumina because boehmite had numerous hydroxyl groups. Finally, we estimated that the deactivation of hydrogen recombination catalysts was caused by two combined factors; these were the characteristics of boehmite as the ingredient of catalysts support and the organic silicon poisoning the catalyst surface. As countermeasures, the boehmite was changed into more stable gamma alumina by adding heat treatment in a hydrogen atmosphere at 500°C for 1 h, and the source of organic silicon, organosilicon sealant, was removed. The improved catalysts were applied at Hamaoka Units 4 and 5. Moreover, the linseed oil that used to be used at the plants was applied again as sealant in the low-pressure turbine casing instead of organosilicon sealant. As a result of the application of these countermeasures, the reactors could be started without increasing the hydrogen concentration at these plants. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]