THERMAL-POWER-PLANT CONDENSER-TUBE CORROSION ANALYSIS

Jakov Batelić; Vedrana Špada; Marko Kršulja; Sanja Martinez

doi:10.17222/mit.2023.747

Jakov Batelić HEP Production 52234 Plomin luka, Plomin luka 50, Sector for Thermal Power Plants, Plomin Power Plant Operation, Croatia
Vedrana Špada Istrian Polytechnic, METRIS Materials Research Centre of the Region of Istria, Zagrebačka 30, 52100 Pula, Croatia
Marko Kršulja University Juraj Dobrila of Pula, Faculty of Engineering, Zagrebačka 30, 52100 Pula, Croatia
Sanja Martinez University of Zagreb, Faculty of Chemical Engineering and Technology, Department of Electrochemistry, Marulićev trg 19, 10 000 Zagreb, Croatia

DOI: https://doi.org/10.17222/mit.2023.747

Keywords: corrosion, pitting, thermal power plant, condenser

Abstract

The thermal-power-plant condenser tubes, conducting cooling seawater, experienced frequent leakages, prompting the hereby presented failure analysis. Visual inspection of the corroded/ruptured tube segments revealed that localized corrosion may be linked to seawater sediments and thick layers of corrosion products at the tube water side. Sediments were found along the tube bottom and thick corrosion products were found adjacent to the point of contact between the baffle plates and the exterior tube walls. Underdeposit corrosion, accelerated due to sulphate-reducing bacteria, was diagnosed based on the excess sulphur found at the pit bottom using EDX, the FT-IR spectrum indicating the presence of biofilm and SEM determining the featuring corrosion products based on the biofilm. It was proposed that the corrosion initiating deposits were linked to the condenser shutdown and startup periods. Results showed that pitting corrosion occurred under the influence of biofilm microorganisms tolerant to copper. The main goal of this research was achieved by defining a systematic procedure for avoiding a shutdown of the thermal power plant.

References

1. VGB-R 106e Guideline, Tubes for Condensers and other Heat Exchangers for the Operation of Steam Turbine Plants Copper Alloys, VGB PowerTech e.V, 3rd Edition, 2010
2. T. S. Rao, S. Bera, Protective layer dissolution by chlorine and corrosion of aluminum brass condenser tubes of a nuclear power plant, Engineering Failure Analysis Vol. 123, 2021, 105307, https://doi.org/10.1016/j.engfailanal.2021.105307
3. T. S. Rao, K. V. Nair, Microbiologically influenced stress corrosion cracking failure of admiralty brass condenser tubes in a nuclear power plant cooled by freshwater, Corrosion Science Vol. 40, Issue 11, 01.11.1998, pp. 1821-1836, https://doi.org/10.1016/S0010-938X(98)00079-1
4. M. L. Carvalhoa, J. Domabc, M. Sztylerb; I. Beech, P. Cristiania, The study of marine corrosion of copper alloys in chlorinated condenser cooling circuits: The role of microbiological components; Bioelectrochemistry, Volume 97, June 2014, pp. 2-6, https://doi.org/10.1016/j.bioelechem.2013.12.005
5. N. X. Xiao, F. W. Wei, M. G. Jun, B. S. Qi & S. Zang, Failure analysis of the condenser brass tube in 150 MW thermal power units, Engineering Failure Analysis, Vol. 33, 2013, Pages 75-82, https://doi.org/10.1016/j.engfailanal.2013.04.026
6. Microhardness test - HRN EN ISO 6507-1: 2018, https://repozitorij.hzn.hr/norm/HRN+EN+ISO+6507-1%3A2018.
7. M. L. Carvalho. Corrosion of copper alloys in natural seawater: effects of hydrodynamics and pH, PhD Thesis, Université Pierre et Marie Curie - Paris VI, 2014.
8. T. Liptakovaa, J. Broncekb, M. Loviseka, J. Lagoa, Tribological and corrosion properties of Al-brass, Materials Today: Proceedings 4 (2017) 5867–5871
9. HRN EN ISO 12451 for CuZn20Al2As alloy, https://repozitorij.hzn.hr/norm/HRN+EN+12451%3A2013.
10. E. Stålnacke, E. Claesson, C. Obitz, M. Lilja, J. Odqvist, J. Hagström & O. Rod (2020) Corrosion–microstructure interrelations in new low-lead and lead-free brass alloys, Materials Science and Technology, 36:8, 917-924, DOI: 10.1080/02670836.2018.1489619
11. Z. Zhang, R. Cai, W. Zhang, Y. Fu, N. Jiao, A Novel Exopolysaccharide with Metal Adsorption Capacity Produced by a Marine Bacterium Alteromonas sp. JL2810. Mar Drugs. 2017;15 (6):175. doi: 10.3390/md15060175. PMID: 28604644; PMCID: PMC5484125.
12. W. Moore (2017) Power station condensers their design and failure modes, Materials at High Temperatures, 34:5-6, 407-414, DOI: 10.1080/09603409.2017.1370191
13. Q. Mahmood, P. Zheng, J. Cai, H. Yousaf, H. M. Jaffar, W. Dong-lei, H. & Bao-Ian, Sources of sulfide in waste streams and current biotechnologies for its removal. J. Zhejiang Univ. - Sci. A 8, 1126–1140 (2007). https://doi.org/10.1631/jzus.2007.A1126
14. X. Hu, J. Liu, H. Liu, G. Zhuang & L. Xun, Sulfur metabolism by marine heterotrophic bacteria involved in sulfur cycling in the ocean. Sci. China Earth Sci. 61, 1369–1378 (2018). https://doi.org/10.1007/s11430-017-9234-x
15. C. D. S. Tuck, C. A. Powell, & J. Nuttall, (2016), Corrosion of Copper and Its Alloys. Reference Module in Materials Science and Materials Engineering. doi:10.1016/b978-0-12-803581-8.01634-9
16. W. Faes, S. Lecompte, Z. Y. Ahmed, J. Van Bael, R. Salenbien, K. Verbeken and M. De Paepe, Corrosion and corrosion prevention in heat exchangers, Corrosion Reviews, Vol. 37, Issue 2, Pages 131–155, eISSN 2191-0316, ISSN 0334