2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 2: Dubois Intl. Symp. / Complex Metallic Systems
| Editors: | Kongoli F, Kobe S, Calin M, Dong C |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 130 pages |
| ISBN: | 978-1-987820-38-6 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Boiler Tube Failure Due to Flow Accelerated Corrosion in Kazeroon Power plant
Soha Mohajeri1;1SHARIF UNIVERSITY OF TECHNOLOGY, Tehran, Iran (Islamic Republic of Iran);
Type of Paper: Regular
Id Paper: 457
Topic: 36
Abstract:
The failure of Drum & Economizer tubes of a boiler in Kazeroon Power plant occurred in 2015. An analysis of the failure was made by chemical and metallographic examinations and SEM studies. According to inspections, there were numerous small pits in fractured sections and inside surfaces of the failed tubes resembled orange peel which is a representative of Flow Accelerated Corrosion (FAC). The water chemistry of the boiler was examined and investigations revealed that water treatment was performed by the All Volatile Treatment method in which dissolved oxygen had been removed by the addition of hydrazine as an oxygen scavenger, and the pH of feedwater was maintained between 9~10 with the addition of ammonia, leading to the formation of a magnetite layer. It was concluded that inappropriate feed water chemistry was the main cause of tubes failure, and the water chemistry regime must be changed by the Combined Water Treatment method. Thus, an oxidizing fluid was utilized and oxygen was maintained at a level of 150 to 300 ppb to stimulate the formation of a protective layer of hematite on top of the magnetite and prevent the occurrence of single-phase FAC. Simultaneously, the pH was adjusted in the range of 8.0 ~ 9.0 so that two phase-FAC could be avoided.