Corrosion in the Flue Gas Cleaning System of a Biomass-Fired Power Plant
After only a few years operation, corrosion damage was observed in the flue gas cleaning system of a biomass power plant. The corrosion was on the lower part of the gas/gas heat exchanger fabricated from A242 weathering steel, where UNS S31600 bolts were used to attach sealing strips to the rotor. Thick iron oxides (up to 5 mm) had formed on the weathering steel, and these oxides also contained chlorine and sulfur. In this area of the heat exchanger, weathering steel has not had the optimal wet/dry cycles required to achieve a protective oxide. Due to the thick growing oxide on the rotor, the UNS S31600 bolts were under stress and this together with the presence of accumulated chlorine between the sealing strips and bolts resulted in stress corrosion cracking and rupture. In addition, Zn-K-Cl deposits were agglomerated in the duct after the DeNOx unit. Zn was also a constituent of corrosion products in various places in the ducts resulting in hygroscopic compounds. The presence of Zn in these cases was not from the fuel and is assumed to have originated from Zn containing primer (used to protect the plant during construction) reacting with flue gas constituents containing chlorine (KCl and HCl).
KeywordsCorrosion failure analysis Deposits Flue gas cleaning plant
The authors thank HOFOR for allowing the publication of this paper. Thanks also go to staff at DTU-Mekanik for help with analysis and discussions.
- 1.L. Lindau, B. Goldschmidt, Low temperature corrosion in bark fuelled small boilers, Värmeforsk Report M9-835 (2002 in swedish, 2008 in English)Google Scholar
- 2.M. Nordling, Korrosion hos luftförvärmare och ekonomisrar (Corrosion on air preheaters and economisers), Värmeforsk Report M08-815 Nr. 1235. May 2012 (in Swedish)Google Scholar
- 3.J.P. Jensen, L.D. Fenger, N. Henriksen, Cold-end corrosion in biomass and waste incineration plants. PowerPlant Chem. 2(8), 469–471 (2001)Google Scholar
- 4.T. Herzog, W. Müller, W. Spiegel, J. Brell, D. Molitor, D. Schneider, Corrosion caused by dewpoint and deliquescent salts in the boiler and flue gas cleaning, VGL: KG Thome-Kozmiensky og M. Beckmann: Energie aus Abfall Band 9 Neuruppin: TK Verlag 2012. p 429–460Google Scholar
- 5.M. Montgomery, L.V. Nielsen, M.B. Petersen, Utilization of on-line corrosion monitoring in the flue gas cleaning system, Proceedings NACE International Corrosion Conference 2015, p. 5550Google Scholar
- 6.M. Montgomery, L.V. Nielsen, M.B. Petersen, Assessment of corrosion in the flue gas cleaning system using on-line monitoring. VGB Powertech 10, 77–83 (2015)Google Scholar
- 9.W.M. Cox, Corrosion Management (Private Communication, Rugby, 2011)Google Scholar
- 10.D C Cook, An active coating and new protection technology for weathering steel structures in chloride containing environments, Proceedings NACE International Corrosion Conference 2007, p. 07360Google Scholar
- 11.T.S. Mintz, L. Caseres, D.S. Dunn, M. Bayssie, Atmospheric salt fog testing to evaluate chloride induced stress corrosion cracking of type 304, 304L, and 316 stainless steel, Proceedings NACE International Corrosion Conference 2010, p. 10232Google Scholar
- 12.N.D. Fairweather N. Platts, D.R. Tice, Stress corrosion cracking initiation of type 304 stainless steel in atmospheric environments containing chloride: influence of surface condition, relative humidity, temperature and thermal sensitization, Proceedings NACE International Corrosion Conference 2008, p. 08485Google Scholar
- 13.L. Yang, R.T. Pabalan, L. Browning, D.S. Dunn, Corrosion behavior of carbon steel and stainless steel materials under salt deposits in simulated dry repository environments, Material Research Society Symposium. Proceedings. Vol 757, 2003, II4.14.1Google Scholar
- 14.Thermo-Calc Software, Database SALT1. Accessed 22 Dec 2016Google Scholar