| 1. |
- Cantatore, Valentina, 1986, et al.
(author)
-
Oxidation Driven Permeation of Iron Oxide Scales by Chloride from Experiment Guided First-Principles Modeling
- 2019
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:42, s. 25957-25966
-
Journal article (peer-reviewed)abstract
- In this comprehensive investigation, it is demonstrated how chloride ions may permeate a crack-free oxide scale, thus providing hitherto missing mechanistic insight as to the impacts of KCl(s) or HCl(g) exposures on the high-temperature corrosion of biomass- and waste-fired boilers. Guided by dedicated experimental analyses, mechanistic understanding is gained by means of density functional theory. Chloride ions, being accommodated in oxygen anion vacancies that are generated at the receding magnetite/alloy interface, are driven through the oxide scale by the oxidation process. Intermediate stabilities of quasi-homogeneous transient iron oxychloride species are found, employing potassium ferrite and goethite as complementary cation sinks for the KCl(s) and HCl(g) reactants, respectively. Spontaneous disproportionation of the supersaturated oxychlorides into two different types of chloride decorated magnetite grain boundaries is demonstrated. These motifs are proposed to explain loss of scale integrity as well as accelerated oxidation by offering short-circuiting transient pathways for ion diffusion.
|
|
| 2. |
- Davidsson, Kent, 1967, et al.
(author)
-
Potassium, chlorine, and sulfur in ash, particles, deposits, and corrosion during wood combustion in a circulating fluidized-bed boiler
- 2007
-
In: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 21:1, s. 71-81
-
Journal article (peer-reviewed)abstract
- The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry.
|
|
| 3. |
- Folkeson, Nicklas, 1981, et al.
(author)
-
Fireside corrosion of stainless and low alloyed steels in a waste-fired CFB boiler; The effect of adding sulphur to the fuel
- 2008
-
In: Materials Science Forum. ; 595-598, s. 289-297
-
Journal article (peer-reviewed)abstract
- Corrosion field tests have been carried out in the superheater region of a commercial waste-fired 75MW CFBC boiler using air cooled probes. Exposure time was 24 and 1000 hours. The effect of adding sulphur to the fuel on the corrosion of two high alloyed steels and a low alloyed steel was studied. The fuel consisted of 50% household waste and 50% industrial waste. The exposed samples were analyzed by ESEM/EDX and XRD. Metal loss was determined after 1000 hours. Both materials suffered significant corrosion in the absence of sulphur addition and the addition of sulphur to the fuel reduced corrosion significantly. The rapid corrosion of the high alloyed steel in the absence of sulphur addition is caused by the destruction of the chromium-containing protective oxide by formation of calcium chromate. Adding sulphur to the fuel inhibited chromate formation and increased the sulphate/chloride ratio in the deposit. Iron(II) chloride formed on the low alloyed steel regardless of whether sulphur was added or not.
|
|
| 4. |
- Hoseini Hooshyar, Hamed, 1986, et al.
(author)
-
The Effect of H-2 and H2O on the Oxidation of 304L-Stainless Steel at 600 A degrees C: General Behaviour (Part I)
- 2016
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 85:3-4, s. 321-342
-
Journal article (peer-reviewed)abstract
- The effect of p(H2O) and p(H-2) on the oxidation of 304L stainless steel at 600 A degrees C has been investigated in the present study. The samples were analysed by means of X-ray diffraction, Auger spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy. The results showed that at fixed p(H-2), the corrosion rate increased considerably with increasing p(H2O). At fixed p(H2O), the corrosion rate decreased slightly with increasing p(H-2). Duplex oxide scales formed during the exposure in all environments. The outer and inner layer consisted of Fe3O4 and (Fe, Cr)(3)O-4, respectively. The latter was mainly in the form of internal oxidation. The Cr-rich oxide formation was observed at the initial oxidation process before oxide breakdown. The Auger analysis also suggested the presence of Cr-rich oxide layer just after the breakaway oxidation. The results indicated that the rate-determining step in the corrosion attack is surface controlled or diffusion controlled through an oxide layer with fixed thickness over time.
|
|
| 5. |
|
|
| 6. |
- Jonsson, Torbjörn, 1970, et al.
(author)
-
High-Temperature Oxidation of FeCr(Ni) Alloys : The Behaviour After Breakaway
- 2017
-
In: Oxidation of Metals. - : Springer Nature. - 0030-770X .- 1573-4889. ; 87:3-4, s. 333-341
-
Journal article (peer-reviewed)abstract
- The oxidation of an austenitic FeCr(Ni) steel at 600 C in H2O ?KCl ? O2/H2 ? H2O ? Ar environments is studied up to 168 h. The oxidationbehaviour after ‘‘breakaway’’ is investigated by microstructural investigations, andthermodynamic calculations (Thermo-Calc) on the FeCr(Ni)–O system are used tointerpret the results. The characteristic ‘‘breakaway’’ scale morphology exhibits anoutward-growing iron oxide and a bottom layer consisting of inward-growing spineloxide and reaction zones containing Cr-rich oxide precipitates and Cr-depletedmetal. The equilibrium calculations show that a miscibility gap appears in the FeCrspinel oxide below 665 C influencing the microstructure of the inward-growingscale. Equilibrium calculations on the FeCrNi–O system show that Ni is notexpected to enter the spinel oxide in low oxygen activity conditions, in accordancewith observations
|
|
| 7. |
|
|
| 8. |
- Jonsson, Torbjörn, 1970, et al.
(author)
-
Oxidation After Breakdown of the Chromium-Rich Scale on Stainless Steels at High Temperature: Internal Oxidation
- 2016
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 85:5-6, s. 509-536
-
Journal article (peer-reviewed)abstract
- Breakaway oxidation of alloy 304L at 600 degrees C was studied in four environments (O-2 + H2O + KCl, O-2 + H2O + SO2 + KCl, H-2 + H2O + Ar, O-2 + K2CO3) for up to 168 h. The resulting scales were investigated by FIB/SEM, SEM/EDX, STEM/EELS, STEM/EDS and oxidation was elucidated by thermodynamic calculations (Thermo-Calc). The initial thin protective scale broke down in all cases. After breakaway, the scale consisted of two layers, i.e. an inward growing spinel/reaction zone and an outward growing iron-rich layer. The general features and microstructure of the scales after breakaway were similar in all environments and were explained in terms of: (1) Different diffusivities of Cr3+ and Fe2+ in the spinel oxide. (2) The appearance of a miscibility gap in the FeCr and FeCrNi spinel oxides. (3) The equilibrium composition of the spinel (at low pO(2) Ni is not present in the spinel).
|
|
| 9. |
|
|
| 10. |
- Jonsson, Torbjörn, 1970, et al.
(author)
-
The influence of KCl on the corrosion of an austenitic stainless steel (304L) in oxidizing humid conditions at 600 ºC: A microstructural study
- 2009
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 72:3, s. 213-239
-
Journal article (peer-reviewed)abstract
- The effect of KCl on the corrosion behavior of the austenitic stainless steel 304L was studied at 600 A degrees C in 5% O(2) + 40% H(2)O + N(2). The breakdown of the protective oxide was investigated. This was done through a detailed microstructural characterization of the oxide scales formed after 1, 24 and 168 h. The oxidized samples were investigated by SEM/EDX, FIB and STEM/EDX. The presence of KCl(s) causes a breakdown of most of the protective scale, even though it is not in direct contact with KCl(s) particles, starting after just 1 h exposure. A fast growing porous oxide formed in direct contact with (former) KCl(s) particles and an about 2 mu m thick scale covered most of the surface. Only some regions were covered by a thin scale. K(2)CrO(4) particles were randomly distributed all over the scale after 1 h exposure. The particles are situated above the oxide scale and are not in direct contact with the subjacent metal. The thin scale contains lower Cr levels than has been observed in corresponding scales formed in the absence of KCl. The breakdown of the protective scale is suggested to be caused primarily by the formation of K(2)CrO(4), depleting the protective oxide in chromium. In addition, chromia evaporation contributes to chromia depletion and breakdown of the protective scale. Very little or no transition metal chlorides were found after breakaway oxidation. Cl is suggested to play a minor role in the initial breakdown of the protective scale. The presence of KCl particles caused local rapid oxidation, which results in an outward growing Fe and Fe-Cr rich porous oxide.
|
|
