51313-02318-Corrosion in Supercritical Water with Different Dissolved Oxygen Content

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Product Number: 51313-02318-SG

ISBN: 02318 2013 CP

Author: Nai-qiang Zhang

Publication Date: 2013

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The corrosion of the ferritic ferritic-mantensitic and austenitic steels including T24 P92 Super304H TP347HFG HR3C were investigated in supercritical water at the temperature of 550 and 600? under the pressure of 25MPa. To probe the influence of dissolved oxygen content on corrosion the dissolved oxygen contents were controlled at 0 100 300 and 2000 ppb respectively. The exposing time was 200 400 600 800 and 1000 h. The surface morphologies and composition were observed using SEM and EDS. The cross-sectional structure and element distribution of the oxide scale were analyzed.
The results indicated dissolved oxygen has an obvious effect on weight gain and exfoliation of oxide scale. Furthermore the influence on exposure to supercritical water was different from high temperature water. The possible explanations for the influence were given. The influences of Cr concentration temperature and water molecule were also investigated. The growth and exfoliation mechanism of oxide scale was changed when the water molecule was present comparing to dry air.
Based on the different effects of dissolved oxygen on corrosion of tubes in different operating conditions a new treatment method of feed water which was appropriate for ultra supercritical power plant was proposed. The method can avoid flow-accelerated corrosion in high and low pressure heaters and decrease corrosion of boiler tubes effectively at the same time.