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Modelling internal nitridation in an alumina-forming austenitic stainless steel
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Swerea KIMAB.ORCID iD: 0000-0002-0861-7342
Swerea KIMAB AB.
Swerea KIMAB AB.
2016 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2016.
Keyword [en]
alumina forming austenitic stainless steel, high temperature corrosion, internal nitridation, kinetic modelling, thermodynamic modelling
National Category
Metallurgy and Metallic Materials
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-186316DOI: 10.1002/maco.201508771ScopusID: 2-s2.0-84962641292OAI: oai:DiVA.org:kth-186316DiVA: diva2:926827
Note

QS 20160510

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2016-05-10Bibliographically approved
In thesis
1. High temperature corrosion in biomass-fired energy applications: Alloying effects and test environment comparisons
Open this publication in new window or tab >>High temperature corrosion in biomass-fired energy applications: Alloying effects and test environment comparisons
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To reduce the greenhouse effect, the use of renewable fuel has to be increased. As renewable fuel has different characteristics compared to fossil fuel regarding content of trace metals, alkali, chlorine and sulphur, the corrosion characteristics in high temperature energy processes have to be evaluated. This thesis concerns high temperature corrosion in the superheater region of a boiler and the syngas cooler area of a gasifier.

For the superheater region, laboratory exposures were performed. The methods included a salt dip exposure, where samples were dipped in an equimolar solution of ZnCl2 and KCl, and two salt bed exposures with different chlorine concentrations, 10 and 20 wt%. Ranking of the materials showed that a Ni content above 10 wt% and Cr above 20 wt% reduced corrosion rates in the salt dip and in the 10% Cl salt bed exposure. For exposure in the 20% Cl bed, even higher alloying was needed. An alumina forming austenitic steel showed future potential in sulphidising-chlorinating environments.

For the gasifier region, the effect of HCl in a simulated gasifier atmosphere was studied and also samples exposed in the syngas section of a biomass gasifier were investigated. Metal loss was low for all exposures and it was observed that chlorine had minor influence. For the plant exposed samples, a difference compared to that reported for coal gasifiers was the absence of FeS for the lowest alloyed steel. Instead, a deposit with pronounced content of Zn, Ca, S and O was present on the surface. Zinc was suggested to mitigate corrosion.

Thermodynamic modelling was used to explain phases present and to predict the nitridation behaviour of an alumina forming austenitic steel. Equilibrium and kinetic modelling of the nitridation showed good coherence with the observed microstructures. However, the kinetic modelling resulted in larger nitridation depths than observed experimentally which was attributed to the presence of a thin oxide layer on the surface of the samples.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xvi, 71 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:17
Keyword
High temperature corrosion, biomass, waste, superheater corrosion, austenitic steel, biomass gasification, alumina-forming austenitic stainless steel, thermodynamic modelling, kinetic modelling
National Category
Metallurgy and Metallic Materials Inorganic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-186318 (URN)978-91-7595-935-1 (ISBN)
Public defence
2016-06-03, F3, Lindstedtsv.26, KTH-Campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Note

QC 20160510

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2016-09-26Bibliographically approved

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