Corrosion of evaporator tubes in low emission steam boilers

• Autorzy: Topolska S. , Łabanowski J.
• Języki publikacji: EN

Abstrakty

EN

Purpose: of this paper is to reveal the mechanisms of corrosion processes of outer surfaces of low-emission steam boiler evaporator tubes. Examinations were performed to find the reasons of different corrosion susceptibility of tubes situated at combustion chamber on various levels. Design/methodology/approach: Examinations were conducted on several segments of Ø 57 x 5.0 mm evaporator tubes made of 16M (16Mo3) steel grade. Segments were taken from level of 10 meters and 18 meters from the chamber bottom of low-emission coal fired steam boiler after two years operation. Microstructure degradation of base material was estimated. Metallographic evaluation of scale morphology, its micro sites chemical composition analysis and distribution of elements on cross sections have been performed. Findings: Eexaminations of evaporator tubes indicated that reduction of wall thickness was considerable at the segments taken from level of 10 m, when at level of 18 m this reduction was small. The morphology of scales consisted of external layer which was porous and weakly connected to the tube surface, and internal layer, which was dense and adherent to the base metal. In these two layers the bands reach in sulfur were detected. The sulfide corrosion seems to be the main degradation mechanism of the tube surface at the level of 10 m. Research limitations/implications: Corrosion of the water wall tubes in low-emission steam boilers is a result of reaction of steel tube surface with the aggressive substoichiometric environment contains sulfur. The chemical composition of flue gases changes along the water wall. The exact compound of flue gases has not been determined in this study. Practical implications: Prevention of water wall tubes corrosion can be achieved by changing in operation conditions or replacement of tube materials. The first mentioned action is limited to accurate burner's adjustment or introduces a flow of additional air along the walls and create air curtain between reducing environment and tubes surface. These efforts often are insufficient. The replacement of more corrosion resistant material on Cr rich steel or Cr-Ni steel is possible but other problems appear connected with high costs of installation and low heat transfer coefficients of such materials. Knowing the mechanisms of corrosion allows adjusting combustion process at low emission steam boilers. Originality/value: Information available in literature does not clearly indicate what mechanism of corrosion is dominant at different parts of combustion chamber. The current study shows which corrosion mechanisms are the most dangerous for evaporator tubes.

Słowa kluczowe

EN

corrosion; steam boiler; gas

PL

korozja; kocioł parowy; spaliny

• Wydawca: International OCSCO World Press
• Czasopismo: Archives of Materials Science and Engineering
• Rocznik: 2010
• Tom: Vol. 42, nr 2
• Strony: 85--92
• Opis fizyczny: Bibliogr. 15 poz.

Twórcy

autor

Topolska S.

autor

Łabanowski J.

• Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland,

Bibliografia

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