Protective Properties Analysis of Oxide Skin by WOT in Supercritical Unit

Abstract:

This paper studied the different formation mechanism and the corrosion protection mechanism of oxide skin in the conditions of WOT and OT in the supercritical units. The WOT tube and OT tube of the high temperature superheater were detected by visual macro inspection, their microscopic structures were analyzed by electron microscopy and their elemental compositions were detected by EDS. The authors put forward steam oxidation mechanism of WOT and peroxide-chromium evaporation mechanism of OT. The test results were analyzed by chemical thermodynamics and chemical kinetics. The experiment and analysis proved that: the oxide skin of WOT’s tube retained the alloying elements and the design of protective structures, but the oxide skin of OT’s tube lost the alloying elements and it had not good protective properties. The studies had shown that: in compared of the WOT and OT, the WOT had a good corrosion protection and a significant advantage of preventing abnormal rapid growth of oxide skin, so WOT was the best choice for feed-water treatment.

• Periodical: Advanced Materials Research (Volumes 616-618)
• Pages: 1725-1731
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.616-618.1725
• Online since: December 2012
• Authors: Wu Bin Qiu, Shan Shan Zhang, Chang Ming Li, Li Na Zhu, Dang Qiang Hao
• Keywords: Formation Mechanism, Oxide Skin, Supercritical Units, Weak Oxidizing Treatment

References

[1] Changming Li, Wubin Qiu, Wenlong Wu etc. Supercritical unit weak oxidizing water treatment research using the newest progress [J]. The report couplet additionally ultra supercritical units exchange. 2011. Shanghai(In Chinese)

[2] R. B. Dooley. Cycle chemistry guidelines for fossil plants: Phosphate continuum and caustic treatment [M]. EPRI, 2004.07

[3] R. B. Dooley. Program on technology innovation: oxide growth and exfoliation on alloys exposed to steam [M]. EPRI, 2007.07

[4] Changming Li, Wenlong Wu, Dangqiang HAO ect. AVT(O)+PT combination manner and its application on 350MW drum boiler units [J]. Chinese Electrical Engineering Society Annual Meeting, Zhengzhou, 2006.12(In Chinese)

[5] Dangqiang Hao, Changmig LI, Wubin QIU. Experience of feedwater oxidizing treatment on 200 MW fossil generating unit [J]. Electric power. 2004,37:22-24(In Chinese)

[6] Changming LI, Wenlong WU, Qunfeng HE. Research and application of the water supply weak oxidizing treatment of WOT[J]. 2009 Power Plant Chemistry Annual Meeting, WU Han, 2009.10(In Chinese)

[7] Henan Electric Power Research Institute. Identifying information of the feed-water by weak oxidizing treatment of 600MW's Supercritical unit [M]. 2011.5(In Chinese)

[8] Ian G. Wright, R. Barry Dooley. Morphologies of oxide growth and exfoliation in superheater and reheater tubing of steam boilers[J]. Materials at High Temperatures, 2011, 28(1): 40-57.

DOI: 10.3184/096034011x12982937656387

[9] S.R. Paterson, R. Moser, and T.R. Rettig, pp.8-8.5 in Proc. EPRI-VGB Int. Conf. on Interaction of Iron-Based Materials with Water and Steam, R. B. Dooley and A. Bursik, Eds., Heidelberg, Germany, June 3–5, 1992. EPRI, Palo Alto, CA: 1992. TR-102101.

[10] Hongyu Cao. Application of feed-water oxygenated treatment in 600 MW unit in Chaozhou power plant[J]. Guangdong Electric Power, 2011,24(3). (In Chinese)

[11] I. G. Wright, R. B. Dooley. A review of the oxidation behaviour of structural alloys in steam[J]. International Materials Reviews, 2010, 55(3): 129-167.

DOI: 10.1179/095066010x12646898728165