| 1. |
- Andersson, Sven, 1968, et al.
(författare)
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High Temperature Corrosion and Dioxin Abatement Using Sulfur Recirculation in a Waste-to-Energy Plant
- 2019
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Ingår i: Detritus. - : Eurowaste SRL. - 2611-4127 .- 2611-4135. ; 5:Mars, s. 92-98
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur Recirculation is a novel technique for reducing the high temperature corrosion and dioxin formation in Waste-to-Energy plants by recirculating sulfur from the wet flue gas cleaning back to the boiler. This is achieved by separating SO2 from the flue gas in a wet scrubber downstream of a HCl scrubber. H2O2 dosed into the scrubber reacts with SO, in the gas and produces a 15-25 wt% H2SO4 solution, which is injected into the boiler producing SO2, thus creating a sulfur loop. The first permanent full-scale installation has been in operation in one of the two commercial full-scale Waste-to Energy boilers at Maabjerg Energy Center (MEC) in Denmark since October 2016. The recirculated sulfur increased the gas concentration of SO2 by a factor of 2-3 in the boiler, thereby enhancing the sulfation of corrosive alkali chlorides to non-corrosive alkali sulfates. The chlorine content of the superheater deposits decreased by 85%, and the superheater corrosion rate decreased by 40-90% during the first year of operation. The dioxin concentrations upstream of the dioxin removal system decreased by 75% and the dioxin emissions decreased by 72% with Sulfur Recirculation in operation. Furthermore, the sulfate containing effluent water was almost eliminated due to the increased sulfation of the ashes and deposits.
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| 2. |
- Eklund, Johan, 1991, et al.
(författare)
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High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications
- 2019
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 91:5-6, s. 729-747
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O 2 + H 2 O and O 2 + H 2 O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass- and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O 2 + H 2 O. Upon addition of KCl (O 2 + H 2 O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass- and waste-fired boiler.
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| 3. |
- Lindmark, Hampus, 1992, et al.
(författare)
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A material degradation study of novel FeCrAl alloys, stainless steels and nickel base alloy in fluidized bed heat exchangers of a waste-fired CFB boiler
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to evaluate the material degradation resistance of two newly developed FeCrAl alloys exposed within the loop seal region of an 85 MWth waste-fired CFB boiler in Sweden. In addition to the FeCrAl alloys, two commercial austenitic stainless steel and one nickel base (Ni-base) alloy were also studied. The samples were exposed for 6 and 12 months by clamping half-moon rings onto tubes of the installed superheater bundle, achieving a material temperature of 500–520 °C. The material degradation of the samples was assessed by evaluating material loss using an ultrasonic thickness gauge in combination with a scanning electron microscope (SEM). Microstructural analysis was carried out using SEM coupled with Energy-dispersive X-ray spectroscopy (EDX). Both FeCrAl alloys showed promising results achieving material losses in the same range as the investigated austenitic stainless steels and the Ni-base alloy. A thin inward-growing Cr/Al-rich and thick outward-growing Fe-rich oxide were present for the FeCrAl alloys, and an internal nitridation zone was formed in the material matrix close to the metal/oxide interphase. The material loss and extent of the corrosion attack for the austenitic stainless steels varied depending on the alloy composition. However, the corrosion attack remained similar, as all the austenitic steels suffered from internal and intergranular corrosion. For the Ni-base alloy, the attack was defined by an internal Cr-rich oxide formation with no intergranular corrosion. This study suggests that the novel FeCrAl alloys provide satisfying resistance towards corrosion and erosion of the fluidized bed heat exchangers in the loop seal region of a waste-fired boiler. In addition, the stainless steel SX and the Ni-base alloy Sanicro® 69 performed well. Furthermore, the results revealed that corrosion rather than erosion was the dominating degradation process of the investigated samples, as deposit formation was observed on most of the samples as well as corrosion product layers. Thus, the erosive aspect of the attack was expected to be minor.
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| 4. |
- Malede, Yohanes C., et al.
(författare)
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KCl-induced corrosion of Ni-based alloys containing 35–45 wt% Cr
- 2019
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Ingår i: Materials and Corrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 70:8, s. 1486-1506
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Tidskriftsartikel (refereegranskat)abstract
- Ni–(35–45)Cr–4Nb alloys containing different fractions of α-Cr were exposed to potassium chloride (KCl)-induced corrosion. The corrosion exposures were carried out for 168 hr at 600°C in a 15% (vol/vol) H2O (g) + 5% (vol/vol) O2 (g) + N2 (g; balance) atmosphere using KCl-free (reference) and predeposited KCl samples. To mimic the KCl deposition in real boilers, 24 hr exposures where KCl vapor condensed continuously onto samples were also performed. The corrosion attack of the studied materials increased significantly when KCl was present compared to the KCl-free samples. For the KCl exposures, the corrosion attack drastically increased when a significant α-Cr fraction was present. α-Cr was either selectively attacked or dissolved through solid-state diffusion and a layered build-up of the outer external scale of K2CrO4 and chromia could be observed. For the in situ condensed KCl exposure, severe corrosion was observed already within the 24 hr exposure, indicating a higher corrosion rate compared with when KCl was predeposited.
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| 5. |
- Olausson, Maria Dolores Paz, 1982, et al.
(författare)
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High temperature corrosion memory in a waste fired boiler – Influence of sulfur
- 2021
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 130, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- The selection of fuel for a Combined Heat and Power (CHP) plant can vary over time. By choosing less expensive fuels, operation costs are reduced, however, cheaper fuels generally increase corrosion maintenance costs. The corrosiveness of different fuels has been studied extensively while how the current corrosion attack is influenced by corrosion history, i.e. previous deposit build-up and oxide scale formation, is less studied. This phenomenon may be referred to as a “corrosion memory” effect (Paz et al., 2017). The present work investigates the influence of addition of sulfur to the fuel on the corrosion memory through air-cooled probes in the Waste-to Energy lines at Måbjerg Energy Center (MEC) in Denmark. The results show a corrosion memory effect, i.e. as initially corrosive environment may increase the subsequent corrosion rate and vice versa.
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| 6. |
- Phother Simon, Julien, 1991, et al.
(författare)
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Continuous KCl addition in high temperature exposures of 304 L – A way to mimic a boiler environment
- 2020
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 167
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Tidskriftsartikel (refereegranskat)abstract
- Alloys exposed in waste-fired boilers tend to exhibit higher corrosion rates and more signs of severe corrosion attack than in laboratory experiments simulating this type of environment. Thus, in order to better mimic the boiler environment, a laboratory setup with continuous deposition of KCl(s) on the samples has been performed. Areas with high amount of deposited KCl(s) reveal an accelerated corrosion attack characterized by thick oxide layers, void formation and steel grain boundary attack. Areas with less deposited KCl(s) exhibited the same morphology as presented earlier for 304 L samples exposed to small amount of KCl(s).
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| 7. |
- Phother Simon, Julien, 1991
(författare)
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High Temperature Corrosion Behavior in Biomass- and Waste-Fired Boilers - Insights into catastrophic corrosion and corrosion mitigation techniques
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon dioxide is contributing to the greenhouse effect and a significant part comes from the use of fossil fuels. Utilizing more renewable fuels is therefore a solution to decrease the net release of CO2 emissions to the atmosphere. This can be achieved by substituting fossil fuels, such as coal and oil, with renewable fuels, such as biomass and waste. However, the combustion of these renewable fuels releases corrosive species creating corrosion challenges for critical parts of the plants, resulting in lower electrical efficiency and higher maintenance costs. It is therefore necessary to understand and investigate the corrosion attack that occurs in this type of environment, in order to find sustainable solutions. High-temperature corrosion research can be divided into two steps: laboratory investigations focus on determining the role or influence of different parameters such as water vapor content or specific corrosive species, while field investigations are more oriented towards in-situ studies to test ideas developed within laboratory studies for mitigation of the corrosion attack. Both approaches are included within the scope of this thesis to broaden the knowledge about the accelerated corrosion of steels, as well as investigate different techniques of mitigation of high-temperature corrosion occurring in biomass- and waste-fired boilers. The laboratory investigations in this thesis focused on KCl-induced corrosion of steels at elevated temperatures (600 °C). A setup allowing a continuous supply of a corrosive species (KCl) during the whole exposure was developed. This generated a corrosive environment mimicking a boiler environment and a corrosion attack better resembling the attack observed in commercial boilers compared to previous methods. Within this setup, four commercial/steels/alloys were investigated and selected in such a way that they represent a broad range of material classes, but also to contain an increasing amount of nickel (from 0 wt.% to 62 wt.%). The results showed that the corrosion attack could be divided into two corrosion morphologies: general corrosion and steel grain boundary attack. Increasing the nickel content resulted in a decrease of the thickness of the general oxide scales. The corrosion attack of the steel grain boundary exhibited a different trend. The attack became more severe when nickel is part of the alloy’s composition. In order to improve the understanding of the corrosion attack in this type of environment, an in-depth study of intergranular corrosion (steel grain boundary attack) in a stainless steel (304L) using the state-of-the-art combination of 3D tomography and TEM was performed. The grain boundary corrosion attack was characterized in detail and revealed new insights of how this complex attack progresses. Very small amounts of Cl were observed in the corrosion front together with very large depletion zones. The design of a new material exhibiting outstanding corrosion resistance properties, excellent mechanical strength, and reasonable costs for application in biomass- and waste-fired boilers is both difficult and time-demanding. Another approach is to separate these properties using a base material (with good mechanical properties) with a corrosion resistant coating. In this work, a set of nickel-based coatings (NiCr, NiAl and NiCrAlY) were investigated in a KCl-rich environment for up to 168 hours. The results showed that the NiAl and NiCrAlY coatings performed well. However, it is necessary to perform a more advanced investigation, i.e. longer durations of exposure, to ascertain their reliability. Another way to mitigate the high-temperature corrosion experienced in boilers would be to alter the environment. Two studies of this alternative solution were investigated in this thesis. A potential new position for superheaters predicted via CFD (Computational Fluid Dynamics) calculations was studied and showed that it is possible to decrease the amount of corrosive species (chlorides) in the deposits. Within the similar scope of making the environment milder for the materials, another technical solution was investigated, the Sulfur Recirculation technique. In this setup, the corrosion history caused by a variation in fuel (corrosion memory effect) was studied and the results showed that the corrosion memory effect can influence positively (when exposed first in a mild environment) and negatively (when exposed first in a corrosive environment) the future corrosion behavior of a material.
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| 8. |
- Phother Simon, Julien, 1991, et al.
(författare)
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High-Temperature corrosion of P91/T91, 304L, Sanicro 28 and Inconel 625 exposed at 600 °C under continuous KCl deposition
- 2024
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Ingår i: Fuel. - 0016-2361. ; 357
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the corrosion attack after breakaway oxidation on four commercial alloys (T91/P91, 304L, Sanicro 28 and Inconel 625) in the presence of KCl(g)/KCl(s) at 600 °C. The study suggests that an increase in corrosion resistant alloying elements (mainly nickel and chromium) results in the decrease of the thickness of the general oxide scale and not equally deep alloy grain boundary attack for the austenitic alloys. The corrosion attack in the presence of KCl is suggested to proceed by chromate formation and chlorine-induced acceleration of the diffusion of ions through the scale.
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| 9. |
- Phother Simon, Julien, 1991
(författare)
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High Temperature Corrosion of Superheaters in Biomass - and Waste-Fired Boilers: Combat on two fronts
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon dioxide is a greenhouse gas contributing to the greenhouse effect and a significant contribution comes from the use of fossil fuels. Utilizing more renewable fuels is therefore a solution to decrease the net release of CO2 emissions to the atmosphere. This can be achieved by substituting fossil fuels, such as coal and oil, with renewable fuels, such as biomass and waste. However, the combustion of these renewable fuels releases corrosive species that deteriorate superheaters and other critical parts of the plants, resulting in lower electrical efficiency and higher maintenance costs. It is therefore necessary to understand and investigate the corrosion attack that occurs in this type of environment, in order to find sustainable material solutions. The aim of this thesis is to increase knowledge on accelerated corrosion in biomass- and waste-fired boilers and to develop solutions that mitigate the corrosion. In order to increase knowledge on accelerated corrosion in these environments, the corrosiveness of alkali salts (e.g NaCl or KCl) towards stainless steels has been investigated in several laboratory studies. However, a large discrepancy in corrosion attack has been observed between laboratory and field investigations. Therefore, a new setup was developed in laboratory in order to better mimic the boiler environment in a well-controlled manner. The present study involves two commercial stainless steels: 304L (18% Cr – 8% Ni type of alloy) and Sanicro 28 (higher chromium and nickel contents). The exposures were performed under continuous KCl deposition in an environment containing O2 and H2O at 600 °C for 24 hours. The results showed: - Continuous KCl deposition caused a corrosion attack similar to the attack observed in boilers. - Continuous KCl deposition accelerated the corrosion attack compared to pre-deposited KCl. - Regions with large amounts of deposited KCl experienced faster corrosion. - The alloy with higher chromium and nickel content exhibited an increased corrosion resistance in this environment. Increasing knowledge on corrosion mechanisms is important for the development of efficient ways of mitigating corrosion. It is possible to mitigate a corrosion attack in two ways: improving the materials or changing the surrounding environment of the materials. A solution to improving the materials is the utilization of coatings. Three different nickel-based coatings (NiCr, NiAl and NiCrAlY) HVAF (High Velocity Air Fuel)-sprayed onto a low-alloyed steel (16Mo3) were investigated. Their protectiveness was tested in two different environments for boiler purposes: A mildly corrosive environment (O2 + H2O) and a highly corrosive environment (O2 + H2O + KCl). The results showed that the NiCr coating did not remain protective since chlorides were detected within the coating and at the coating/substrate interface. In contrast, NiAl and NiCrAlY coatings performed well in both environments with minor oxidation. The other approach to mitigating corrosion is changing the surrounding environment of the materials. A field study investigated the potential of a new superheater position in a boiler, predicted with CFD (Computational Fluid Dynamics) calculations. The impact of different operational parameters of the boiler on the deposit composition and amount were tested. The results showed that it is possible to decrease the amount of corrosive species (chlorides) in the deposits by changing the settings of the boiler. Moreover, the corrosion attack of a fixed installation of several superheater materials was investigated after 8000 hours. The analysis focused on 347H (18% Cr – 8% Ni type of alloy) material and revealed a corrosion attack similar to the new setup with continuous KCl deposition in laboratory.
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| 10. |
- Phother Simon, Julien, 1991, et al.
(författare)
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The influence of a KCl-rich environment on the corrosion attack of 304 L: 3D FIB/SEM and TEM investigations
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the intergranular corrosion of a stainless steel (304 L) in the presence of KCl(g)/KCl(s) at 600 ◦C by using a FIB/SEM to perform 3D reconstruction/tomography of grain boundary attacks in combination with TEM. The investigation shows that the combination of the 3D FIB/TEM offers a great potential for the study of complex features, i.e. intergranular corrosion. The initiation and propagation of the grain boundary attack occurred very rapidly below an intact secondary protection. No large accumulations of metal chlorides were observed at the grain boundary regions. Instead, indications of very rapid alloy diffusion in grain boundary regions were observed.
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