Spatial distribution of Cr-bearing species on the corroded tube surface characterised by synchrotron X-ray fluorescence (SXRF) mapping and micro-XANES

exposure of tubes in oxy-firing flue gas

Iman Ja’baz, Song Zhou, Barbara Estchmann, David Paterson, Yoshihiko Ninomiya, Lian Zhang

Research output: Contribution to journalArticleResearchpeer-review

1 Citation (Scopus)

Abstract

Synchrotron X-ray fluorescence mapping and micro-XANES were employed to characterize the spatial distribution of individual elements and the speciation of Cr on the cross section of various tubes that were exposed to oxy-fuel flue gas at 650 °C, 1 bar for 50 h. The gas composition tested is close to the flue gas produced from oxy-firing of low-rank coal in pilot-scale tests. Multi-layered scales with an uneven distribution were observed for individual elements on both the top surface and spalled layer of carbon steel SS400. Oxidation is the major reaction causing the scaling of the tube, whereas the other reactions such as sulphidation and chlorination led to the buckling of tube surface. The use of Cr, even at a low concentration of 1.2 wt% in 12Cr1MoVG, is essential and can considerably reduce the tube corrosion rate, as well as minimize the difference between oxy-fuel and air-firing flue gases on the tube mass loss rate. The CO2 cycle with the involvement of oxidation (mainly of iron) and carburisation (of chromium) took place simultaneously for the Cr-bearing alloy, even under the coexistence of CO2 and a number of oxidizers in the flue gas tested here. The fast diffusion of CO2 and its derivatives facilitated a preferential occurrence of carburisation under the oxide scale. However, upon the closure of gas passage channels in the oxide scale of a high-Cr tube such as austenite SUS304, the reductants CO and carbon can flow back to tube top surface, causing the formation of carbide on the most outer scale that further fragments into fugitive pieces. Carburisation is also the major cause of corrosion of high-Cr tubes. In contrast, for a tube with medium Cr content, such as high-chrome T91 tube with 9 wt% Cr, it undergoes both oxidation and carburisation successively on the metal/oxide interface. The gas passage channels mostly remain open, and hence, the resultant carbide and carbon precipitate penetrated deep inside the tube.

Original languageEnglish
Pages (from-to)11791-11812
Number of pages22
JournalJournal of Materials Science
Volume53
Issue number16
DOIs
Publication statusPublished - 1 Aug 2018

Cite this

@article{42c0e081d1804cd3b6f0718b759aa575,
title = "Spatial distribution of Cr-bearing species on the corroded tube surface characterised by synchrotron X-ray fluorescence (SXRF) mapping and micro-XANES: exposure of tubes in oxy-firing flue gas",
abstract = "Synchrotron X-ray fluorescence mapping and micro-XANES were employed to characterize the spatial distribution of individual elements and the speciation of Cr on the cross section of various tubes that were exposed to oxy-fuel flue gas at 650 °C, 1 bar for 50 h. The gas composition tested is close to the flue gas produced from oxy-firing of low-rank coal in pilot-scale tests. Multi-layered scales with an uneven distribution were observed for individual elements on both the top surface and spalled layer of carbon steel SS400. Oxidation is the major reaction causing the scaling of the tube, whereas the other reactions such as sulphidation and chlorination led to the buckling of tube surface. The use of Cr, even at a low concentration of 1.2 wt{\%} in 12Cr1MoVG, is essential and can considerably reduce the tube corrosion rate, as well as minimize the difference between oxy-fuel and air-firing flue gases on the tube mass loss rate. The CO2 cycle with the involvement of oxidation (mainly of iron) and carburisation (of chromium) took place simultaneously for the Cr-bearing alloy, even under the coexistence of CO2 and a number of oxidizers in the flue gas tested here. The fast diffusion of CO2 and its derivatives facilitated a preferential occurrence of carburisation under the oxide scale. However, upon the closure of gas passage channels in the oxide scale of a high-Cr tube such as austenite SUS304, the reductants CO and carbon can flow back to tube top surface, causing the formation of carbide on the most outer scale that further fragments into fugitive pieces. Carburisation is also the major cause of corrosion of high-Cr tubes. In contrast, for a tube with medium Cr content, such as high-chrome T91 tube with 9 wt{\%} Cr, it undergoes both oxidation and carburisation successively on the metal/oxide interface. The gas passage channels mostly remain open, and hence, the resultant carbide and carbon precipitate penetrated deep inside the tube.",
author = "Iman Ja’baz and Song Zhou and Barbara Estchmann and David Paterson and Yoshihiko Ninomiya and Lian Zhang",
year = "2018",
month = "8",
day = "1",
doi = "10.1007/s10853-018-2446-6",
language = "English",
volume = "53",
pages = "11791--11812",
journal = "Journal of Materials Science",
issn = "0022-2461",
publisher = "Springer-Praxis",
number = "16",

}

Spatial distribution of Cr-bearing species on the corroded tube surface characterised by synchrotron X-ray fluorescence (SXRF) mapping and micro-XANES : exposure of tubes in oxy-firing flue gas. / Ja’baz, Iman; Zhou, Song; Estchmann, Barbara; Paterson, David; Ninomiya, Yoshihiko; Zhang, Lian.

In: Journal of Materials Science, Vol. 53, No. 16, 01.08.2018, p. 11791-11812.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Spatial distribution of Cr-bearing species on the corroded tube surface characterised by synchrotron X-ray fluorescence (SXRF) mapping and micro-XANES

T2 - exposure of tubes in oxy-firing flue gas

AU - Ja’baz, Iman

AU - Zhou, Song

AU - Estchmann, Barbara

AU - Paterson, David

AU - Ninomiya, Yoshihiko

AU - Zhang, Lian

PY - 2018/8/1

Y1 - 2018/8/1

N2 - Synchrotron X-ray fluorescence mapping and micro-XANES were employed to characterize the spatial distribution of individual elements and the speciation of Cr on the cross section of various tubes that were exposed to oxy-fuel flue gas at 650 °C, 1 bar for 50 h. The gas composition tested is close to the flue gas produced from oxy-firing of low-rank coal in pilot-scale tests. Multi-layered scales with an uneven distribution were observed for individual elements on both the top surface and spalled layer of carbon steel SS400. Oxidation is the major reaction causing the scaling of the tube, whereas the other reactions such as sulphidation and chlorination led to the buckling of tube surface. The use of Cr, even at a low concentration of 1.2 wt% in 12Cr1MoVG, is essential and can considerably reduce the tube corrosion rate, as well as minimize the difference between oxy-fuel and air-firing flue gases on the tube mass loss rate. The CO2 cycle with the involvement of oxidation (mainly of iron) and carburisation (of chromium) took place simultaneously for the Cr-bearing alloy, even under the coexistence of CO2 and a number of oxidizers in the flue gas tested here. The fast diffusion of CO2 and its derivatives facilitated a preferential occurrence of carburisation under the oxide scale. However, upon the closure of gas passage channels in the oxide scale of a high-Cr tube such as austenite SUS304, the reductants CO and carbon can flow back to tube top surface, causing the formation of carbide on the most outer scale that further fragments into fugitive pieces. Carburisation is also the major cause of corrosion of high-Cr tubes. In contrast, for a tube with medium Cr content, such as high-chrome T91 tube with 9 wt% Cr, it undergoes both oxidation and carburisation successively on the metal/oxide interface. The gas passage channels mostly remain open, and hence, the resultant carbide and carbon precipitate penetrated deep inside the tube.

AB - Synchrotron X-ray fluorescence mapping and micro-XANES were employed to characterize the spatial distribution of individual elements and the speciation of Cr on the cross section of various tubes that were exposed to oxy-fuel flue gas at 650 °C, 1 bar for 50 h. The gas composition tested is close to the flue gas produced from oxy-firing of low-rank coal in pilot-scale tests. Multi-layered scales with an uneven distribution were observed for individual elements on both the top surface and spalled layer of carbon steel SS400. Oxidation is the major reaction causing the scaling of the tube, whereas the other reactions such as sulphidation and chlorination led to the buckling of tube surface. The use of Cr, even at a low concentration of 1.2 wt% in 12Cr1MoVG, is essential and can considerably reduce the tube corrosion rate, as well as minimize the difference between oxy-fuel and air-firing flue gases on the tube mass loss rate. The CO2 cycle with the involvement of oxidation (mainly of iron) and carburisation (of chromium) took place simultaneously for the Cr-bearing alloy, even under the coexistence of CO2 and a number of oxidizers in the flue gas tested here. The fast diffusion of CO2 and its derivatives facilitated a preferential occurrence of carburisation under the oxide scale. However, upon the closure of gas passage channels in the oxide scale of a high-Cr tube such as austenite SUS304, the reductants CO and carbon can flow back to tube top surface, causing the formation of carbide on the most outer scale that further fragments into fugitive pieces. Carburisation is also the major cause of corrosion of high-Cr tubes. In contrast, for a tube with medium Cr content, such as high-chrome T91 tube with 9 wt% Cr, it undergoes both oxidation and carburisation successively on the metal/oxide interface. The gas passage channels mostly remain open, and hence, the resultant carbide and carbon precipitate penetrated deep inside the tube.

UR - http://www.scopus.com/inward/record.url?scp=85047212787&partnerID=8YFLogxK

U2 - 10.1007/s10853-018-2446-6

DO - 10.1007/s10853-018-2446-6

M3 - Article

VL - 53

SP - 11791

EP - 11812

JO - Journal of Materials Science

JF - Journal of Materials Science

SN - 0022-2461

IS - 16

ER -