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Research Papers: Nuclear Power

Investigations and Countermeasures for Deactivation of Hydrogen Recombination Catalyst at Hamaoka Units 4 and 5

[+] Author and Article Information
Toru Kawasaki1

Hitachi Works, Hitachi-GE Nuclear Energy, Ltd., 1-1 Saiwai-cho 3-chome, Hitachi, Ibaraki 317-0073, Japantoru.kawasaki.jf@hitachi.com

Motohiro Aizawa

Hitachi Works, Hitachi-GE Nuclear Energy, Ltd., 1-1 Saiwai-cho 3-chome, Hitachi, Ibaraki 317-0073, Japan

Hidehiro Iizuka

 Hitachi, Ltd., 7-2-1 Omika, Hitachi, Ibaraki 319-1221, Japan

Koji Yamada, Mitsuo Kujimoto

 Chubu Electric Power Co., Inc., 1, Toshin-cho, Higashi-ku, Nagoya 461-8680, Japan

1

Corresponding author.

J. Eng. Gas Turbines Power 133(5), 052918 (Dec 28, 2010) (5 pages) doi:10.1115/1.4002892 History: Received August 24, 2010; Revised September 21, 2010; Published December 28, 2010; Online December 28, 2010

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.

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Copyright © 2011 by American Society of Mechanical Engineers
Topics: Catalysts , Hydrogen
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References

Figures

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Figure 1

Configuration of off-gas treatment system around recombiner (Hamaoka Unit 5)

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Figure 2

XRD spectra of catalysts

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Figure 3

Weight loss behavior of catalyst with DTG

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Figure 4

Dependence of dechlorination time dependency on weight loss with DTG

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Figure 5

Correlation between specific surface areas and chemical sorption

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Figure 6

Volatilized components from silicone sealant

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Figure 7

Schematic of recombination test apparatus

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Figure 8

Results of deactivation test with 156 mm diameter scale catalyst

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Figure 9

Assumed mechanism for the deactivation: (a) ring opening, (b) polymerization, and (c) deactivation

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Figure 10

XRD spectrum of improved catalyst

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Figure 11

Correlation between specific surface areas and CO chemical sorption for improved catalysts

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Figure 12

Influence of organosilicon sealant on effectiveness of improved catalyst compared with that of conventional catalysts

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