| 1. |
- Folkeson, Nicklas, 1981
(författare)
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Chlorine Induced Corrosion in Biomass and Waste Fired Boilers: Laboratory and Field Investigations
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The fireside corrosion in biomass and waste fired boilers is widely believed to arise from the presence of chlorine-containing compounds in the fuels. Although many researchers have studied the influence of such compounds on the high temperature corrosion of various steels, the mechanisms underlying chlorine-induced corrosion are still poorly understood. In this thesis, the chlorine induced corrosion of austenitic and ferritic steels is investigated through careful laboratory exposures, detailed microscopy experiments and field exposures in actual boilers.In the laboratory, the effect of adding 500 ppm HCl(g) to a dry atmosphere containing 5% O2 in N2, and to a wet atmosphere containing 40% H2O and 5% O2 in N2, on the oxidation of the austenitic alloy 310S at 500°C was investigated, and also the effect of 0.1 mg/cm2 KCl(s) on the oxidation of the ferritic steel Fe-2.25Cr-1Mo at 400 and 500°C in an atmosphere with 40% H2O and 5% O2 in N2. Polished steel coupons were isothermally exposed for up to 168 hours. After exposure, the samples were analyzed using SEM/EDX, AES, FIB and BIB cross sections, TEM, XRD, and IC. The Fe-2.25Cr-1Mo steel was also oxidized in the presence of KCl, in the specimen chamber of an ESEM, and imaged in situ to follow the evolution of the corrosion morphology in real time.Austenitic and ferritic steels were also exposed in both biomass and waste fired boilers, using air cooled corrosion probes. The field exposures were made to relate the corrosion mechanisms in the laboratory to the actual applications and to evaluate the effect of adding sulphur to the fuel as a measure to mitigate the corrosion.The laboratory investigation showed that the presence of chlorine-containing compounds caused a rapid increase in mass gain, the formation of transition metal chlorides and, after longer exposure times, poorly adherent and buckled oxide scales. The HCl(g) caused formation of transition metal chloride and accelerated corrosion mainly along steel grain boundaries and at slag inclusions in the steel surface of 310S. The KCl caused a significant acceleration of the oxidation of Fe-2.25Cr-1Mo at 400°C and after short exposure times at 500°C. A new mechanism for the chlorination of steel, based on the simultaneous oxidation of O2 and dissociation of adsorbed HCl or KCl at the scale surface and on diffusion of chloride ions along oxide grain boundaries towards the steel surface, is proposed.Transition metal chlorides and high concentrations of alkali chlorides were detected, and also chromate, on austenitic stainless steels, in the field exposures when no sulphur was added to the fuel. With sulphur added, the amount of alkali chloride was suppressed in the waste fired boiler and eliminated in the biomass fired boiler. The average corrosion rage was reduced by around 50% for all materials in the waste fired boiler. In the biomass fired boiler, the corrosion rate of the ferritic material was reduced by almost 50%, while the corrosion rates of the austenitic materials were reduced by more than 90% when sulphur was added.
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| 2. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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Fireside corrosion of stainless and low alloyed steels in a waste-fired CFB boiler; The effect of adding sulphur to the fuel
- 2008
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Ingår i: Materials Science Forum. ; 595-598, s. 289-297
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Tidskriftsartikel (refereegranskat)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.
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| 3. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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Initial stages of the HCl-induced high-temperature corrosion of alloy 310
- 2007
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Ingår i: Journal of the Electrochemical Society. - 1945-7111 .- 0013-4651. ; , s. 515-521
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Tidskriftsartikel (refereegranskat)abstract
- Polished 310 stainless steel coupons were exposed isothermally in a horizontal tube furnace at 500 C for 1-168 h. The exposure gas consisted of N-2 with 5% O-2 and 500 ppm HCl(g). The corroded samples were analyzed by X-ray diffraction, focused ion beam microanalysis, scanning electron microscopy with energy-dispersive X-ray analysis, and by Auger electron spectroscopy. Mass gain was recorded. As expected, HCl (g) is a corrosion accelerator, the dominating corrosion products being FeCl2, Fe2O3, and Cr2O3. A tentative mechanism for the initial stages of the HCl-induced corrosion of stainless steel is presented. (c) 2007 The Electrochemical Society.
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| 4. |
- Folkeson, Nicklas, 1981
(författare)
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Investigations of Chlorine-Induced High Temperature Corrosion of Steels
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The high corrosivity of the fireside environment in waste and biomass fired boilers is commonly attributed to the presence of chlorine-containing compounds. Chlorine-induced high temperature corrosion is not well understood, however. In this study, the effect of chlorine-containing compounds on corrosion is investigated by laboratory exposures and by field exposures in a commercial boiler. In the laboratory exposures polished austenitic stainless steel 310S coupons were exposed to 5% O2 in N2, with 500 ppm HCl at 500 °C for up to 168 hours. After exposure, the samples were investigated by SEM/EDX, FIB, AES and XRD. The corrosive nature of HCl was confirmed, with large amounts of FeCl2 forming in the corrosion scale. FeCl2 was not confined to the scale/metal interface but was present throughout the scale and at the scale/gas interface. Severe localised attack occurred in connection to slag inclusions in the steel surface. A new mechanism for chlorine-induced corrosion of stainless steel is proposed. The mechanism involves the simultaneous reduction of O2 and dissociation of HCl at the scale surface, and grain boundary diffusion of chloride ions and iron (II) ions through the scale, forming FeCl2.In the field exposures sample rings were mounted on air cooled probes and exposed in the 75 MW boiler in Händelö, Norrköping. The fuel was a mixture of 50% household waste and 50% industrial waste. Elemental sulphur was added to the fuel to investigate the effect of SO2 /SO3 on deposit composition and superheater corrosion. The austenitic stainless steels Sanicro 28 and 304L and the low alloyed steel 15Mo3 were exposed at 500 °C for 24 - 1000 hours. After exposure, the samples were investigated by SEM/EDX and XRD. The corrosion rate was determined after 1000 hours. Adding sulphur to the fuel reduced corrosion rate by about 50% for all three materials. In the absence of sulphur addition, large amounts of chromate formed on the stainless steels. This indicates that corrosion was initiated by chromate formation, rendering the oxide non-protective and leaving it susceptible to attack by chlorine containing compounds (e.g. HCl). The low alloyed material was unable to form a protective oxide, and formed large amounts of iron chloride. SO2 in the flue gas converts alkali chlorides and alkaline earth chlorides in the deposits into sulphates, which are considerably less corrosive towards the materials.
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| 5. |
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| 6. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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The influence of small amounts of KCl(s) on the high temperature corrosion of a Fe-2.25Cr-1Mo steel at 400 and 500 degrees C
- 2011
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Ingår i: Materials and Corrosion - Werkstoffe und Korrosion. - : Wiley. - 1521-4176 .- 0947-5117. ; 62:7, s. 606-615
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the oxidation behaviour of a low-alloyed steel (Fe-2.25Cr-1Mo) in the presence of small amounts of KCl(s) at 400 and 500 degrees C. Cleaned and polished sample coupons were exposed in a horizontal tube furnace with exposure times ranging from one hour to one week. The flue gas composition was 5% O(2) with 40% H(2)O in N(2), and 0.1mg KCl/cm(2) was deposited on the samples prior to exposure. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis were used to characterize the samples. Cross sections were prepared by means of focused ion beam (FIB) and broad ion beam (BIB). At 400 degrees C there was a modest mass gain in the absence of KCl. In the presence of KCl, mass gain is significantly increased and a rapid attack is evident already after short exposure times. At 500 degrees C, the mass gains in the absence of KCl were considerably higher than at 400 degrees C, especially after 168 hours of exposure. KCl had an effect at shorter exposure times, but after one week the samples exposed with and without KCl had mass gains of comparable magnitude.
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| 7. |
- Herstad-Svärd, S., et al.
(författare)
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Ramprogram – Åtgärder för samtidig minimering av alkalirelaterade driftproblem, Etapp 2
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of an increasing amount of biofuel and waste woods has resulted in certainenvironmental advantages, including decreased emissions of fossil CO2, SO2 andmetals. On the other hand, a number of chloride and alkali related operational problemshave occurred which are related to combustion of these fuels.Alkali related operational problems have been studied in a project consisting of twoparts. The overall scope has been to characterise the operational problems and to studymeasures to minimise them. The first part was reported in Värmeforsk report 997 wherethe results were summarised in a table of different measures. In part two, additionalmeasures have been included in the test plan and initial corrosion has been studiedlinked to the different measures. The tests have also in part two been carried out at the12 MW CFB boiler at Chalmers. The effect of the selected measures has beeninvestigated concerning both deposit formation and bed agglomeration, and at the sametime emissions and other operational conditions were characterised.The second part of the project has among other things focused on:• To investigate measures which decrease the content of alkali and chloride in thedeposits, and consequently decrease the risk for corrosion (by investigating theinitial corrosion). Focus was also on trying to explain favourable effects.• To investigate if it is possible to combine a rather low dosage of kaolin and injectionof ammonium sulphate. This was done in order to reduce both bed agglomerationand problems from deposits during combustion of fuels rich in chlorine.• To investigate if co-combustion with sewage sludge, de-inking sludge or peat withhigh ash content, could give similar advantages as conventional additives.• Investigate if ash from PFBC is possible to use as an alternative bed material.By comparing the different measures in part two, it could be concluded that cocombustionof sewage sludge gave the best overall effect. The judgement was based onthe effects concerning bed agglomeration, level of alkali chloride in the flue gas,deposits and initial corrosion. Simultaneous addition of kaolin and ammonia sulphatealso had a favourable impact both in the bed and on the alkali chlorides in the gas phase.Dosage of kaolin did not reduce the effect of injected ammonium sulphate. Cocombustionof peat could also be a very attractive alternative, but it is critical to select asuitable peat type. It is of special concern to avoid peat with a high content of calcium,since it can increase the level of alkali chlorides by reacting with available sulphur.Change of bed material to ash from PFBC can decrease problems with bedagglomeration, but there is a risk of increased deposit formation and corrosion. A boileroperated with high steam data should consequently combine the change of bed materialwith injection of ammonium sulphate or another source of sulphur.Co-combustion of de-inking sludge from pulp and paper production can reduceproblems with bed agglomeration. There is, however, an increased chance of corrosiondue to the high content of calcium. Injection of sulphates may improve the situationconcerning corrosion. The results also showed that low potassium chlorine content in the flue gas decreasesthe risk of corrosion. Increased amount of potassium chlorine content in the flue gaswill not necessary give a high amount of chlorine content in the deposits if there is sulphur in the system.Key words: agglomeration, deposits, corrosion, alkali, kaolin, ammonium sulphate,sludge
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| 8. |
- Hosseini, Vahid, 1987-, et al.
(författare)
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Fe and Cr phase separation in super and hyper duplex stainless steel plates and welds after very short aging times
- 2021
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Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- Fe and Cr phase separation in ferrite, causing 475°C-embrittlement, was studied after very short aging times in super duplex stainless steel (SDSS) and hyper duplex stainless steel (HDSS) plates and welds. Atom probe tomography showed that hot-rolled SDSS, experiencing significant metal working, had faster kinetics of phase separations compared to the SDSS and HDSS welds after 5 min aging at 475 °C. The surface of the 33-mm SDSS plate had faster Fe and Cr phase separation and larger toughness drop. A higher density of dislocations next to the austenite phase boundary in ferrite, detected by electron channeling contrast, can promote the phase separation at the surface of the plate with lower austenite spacing. The toughness dropped in HDSS welds after aging, but SDSS welds maintained their toughness. An inverse simulation method considering an initial sinusoidal nanometric Cr and Fe fluctuation showed that Ni increases the interdiffusion of Cr in the system, resulting a higher degree of phase separation in SDSS welds than the HDSS weld. Within the composition range of the studied SDSS and HDSS materials, the processing influences the Fe and Cr phase separation more than the variation in composition during short aging or typical fabrication times.
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| 9. |
- Hosseini, Vahid, 1987-, et al.
(författare)
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Influence of Fabrication Route and Copper Content on Nature and Kinetics of 475 °C- Embrittlement in Cu-Containing Super Duplex Stainless Steels
- 2023
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Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 4, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- The influence of hot-rolling, hot isostatic pressing (HIP), welding, as well as copper content on 475 °C-embrittlement is studied in super duplex stainless steels. The as-received samples are solution annealed and quenched. Then, to study the kinetics and nature of phase transformations during fabrication, the samples are aged for a very short duration of 5 min at 475 °C. Atom probe tomography results reveal that the processes involving more plastic deformation such as hot rolling and HIP accelerate chromium and iron phase separation and cause precipitation of copper-rich particles (CRPs) in ferrite, resulting in significant toughness loss. In contrast, the weld does not show a high level of chromium and iron phase separation or CRPs precipitation, preserving its toughness after the short aging. The experiment and the inverse interdiffusion calculations reveal that raising the copper content slow down chromium and iron phase separation but significantly increase the CRP number density and decrease the toughness of the HIPed material. Precipitation simulation of CPRs show that the model must be modified based on each processing condition. It is concluded that hot rolling and HIP accelerate 475 °C-embrittlement, which cannot be prevented by raising the copper content.
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| 10. |
- Hosseini, Vahid, 1987-, et al.
(författare)
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Precipitation kinetics of Cu-rich particles in super duplex stainless steels
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 3951-3964
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Tidskriftsartikel (refereegranskat)abstract
- Complex precipitation behavior of Cu-rich particles (CRPs) was investigated and simulated in continuously cooled and quench-aged super duplex stainless steel. Atom probe tomography (APT) and scanning electron microscopy showed that slow cooling resulted in nonuniform multimodal CRP precipitation and spinodal decomposition, while in the fast cooled and quench-aged conditions, more uniform precipitation of CRPs with no visible spinodal decomposition was found. Depletion of Cu, Ni, and Mn was observed in the ferrite next to the CRPs during growth, but not during dissolution. Some evidence of Ostwald ripening was seen after slow cooling, but in the quench-aged condition, particle coalescence was observed. Large CRPs disappeared next to a ferrite–austenite phase boundary after slow cooling when Cu was depleted due to the diffusion to austenite as also predicted by moving boundary Dictra simulation. Comparing Cu depleted areas next to CRPs analyzed by APT and moving boundary Dictra simulation of CRP–ferrite showed that the effective Cu diffusion coefficient during the early-stage precipitation was about 300 times higher than the Cu diffusion coefficient in ferrite at 475 °C. Using the effective diffusion coefficient and a size-dependent interfacial energy equation, CRP size distribution was successfully predicted by the Langer–Schwartz model implemented in Thermo-Calc Prisma. Applying a short aging time and continuous cooling increased the hardness and decreased the toughness values compared to the solution annealed condition. A nonuniform distribution of Cu in ferrite, the duplex structure, and partitioning of alloying elements among different phases are factors making CRP precipitation in duplex stainless steels complex.
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| 11. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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An ESEM in situ investigation of initial stages of the KCl induced high temperature corrosion of a Fe-2.25Cr-1Mo steel at 400 degrees C
- 2011
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 53:6, s. 2233-2246
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Tidskriftsartikel (refereegranskat)abstract
- The initial oxidation of a low-alloyed steel (Fe-2.25Cr-1Mo) in the presence of small amounts of KCl(s) have been investigated through ESEM in situ exposure and analysis at 400 degrees C. The samples were also characterized by XRD, SEM/EDX and FIB. The present study shows the corrosive nature of KCl towards the low alloyed steel. It is concluded that the initial KCl distribution is important and that a KCl/FeCl2 liquid phase film forms on large parts of the oxide surface in the presence of KCl. It is proposed that Cl increases the oxidation rate (by decorating oxide grain boundaries) and decreases the oxide scale adhesion. (C) 2011 Elsevier Ltd. All rights reserved.
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| 12. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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Microstructural Investigation of the HCl-Induced Corrosion of the Austenitic Alloy 310S (52Fe26Cr19Ni) at 500 °C
- 2014
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 81:5-6, s. 575-596
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the influence of 500 ppm HCl in a 5 %O2-95 %N2 atmosphere on the oxidation of the austenitic stainless steel AISI 310S at 500 °C. Laboratory exposures were made for one, 24, 72 and 168 h and the samples were analysed with XRD, SEM/EDX, FIB and TEM/EDX. When exposed in oxygen a thin and protective chromium-rich oxide scale forms. Addition of HCl causes significantly accelerated corrosion. Within the first hour of exposure, accumulations of FeCl2, CrCl2 and NiCl2 forms below the chromium-rich oxide, especially at steel grain boundaries. The chlorine-induced corrosion is suggested to occur through an electrochemical reaction, in which the dissociation of HCl to form chloride ions at the scale surface is coupled to the oxidation of the metal surface beneath the scale by an outwards electronic current and inwards diffusion of chloride ions along oxide grain boundaries
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| 13. |
- Pettersson, Jesper, 1978, et al.
(författare)
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The Effects of KCl, K2SO4 and K2CO3 on the High Temperature Corrosion of a 304-Type Austenitic Stainless Steel
- 2011
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 76:1-2, s. 93-109
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of 304-type (Fe18Cr10Ni) austenitic stainless steel was investigated at 500 and 600 degrees C in 5% O(2) + 40% H(2)O. Prior to exposure the samples were sprayed with KCl, K(2)CO(3) or K(2)SO(4), the amount of salt corresponding to 1.35 mu mol K(+)/cm(2). For reference, salt-free samples were exposed in 5% O(2) + 40% H(2)O and in 5% O(2) (N(2) was used as carrier gas). The oxidized samples were analyzed with SEM/EDX, XRD, IC and FIB. KCl and K(2)CO(3) strongly accelerate the corrosion of 304L while K(2)SO(4) has little influence on the corrosion rate and on the morphology of the corroded surface. KCl and K(2)CO(3) react with the chromium-rich oxide on the sample surface, forming K(2)CrO(4). The resulting chromium depletion of the protective oxide causes rapid oxidation and the formation of a thick duplex scale consisting of an outer hematite layer and a inner layer made up of FeCrNi spinel-type oxide. The differences in the corrosivity of the three salts are directly connected to their ability to form chromate on the surface and, hence, to the relative stability of the corresponding leaving groups (HCl, CO(2) and SO(3)).
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| 14. |
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| 15. |
- Pettersson, Jesper, 1978, et al.
(författare)
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The influence of sulphur additions on the corrosive environment in a waste-fired CFB boiler
- 2005
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 522-523, s. 563-570
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion/deposition field tests have been carried out in the superheater region of a commercial waste-fired 75MW CFBC boiler using air cooled probes. The influence of material temperature (450-500 degrees C), flue gas temperature, temperature variations (i.e. thermal cycling) and additives to the fuel (elemental sulphur and dolomite) on deposition and corrosion was studied. The results presented here mainly consider the influence of sulphur additions to the fuel. The fuel was a mixture of 50% household waste and 50% industrial waste. After exposure the samples were analyzed by ESEM/EDX, XRD, AAS, FIB and IC. With no additional sulphur, alkali chlorides made up a large part of the deposit/corrosion product layer and in some cases chromate (VI) was detected. It is suggested that the chromate (VI) has formed by reaction of the protective oxide with alkali chlorides in the deposit. Adding sulphur to the fuel changed the composition of the deposits, alkali chlorides being largely replaced by alkali sulphates. No chromates(VI) were detected in the sulphur-added runs. It is suggested that adding sulphur to the fuel may decrease fireside corrosion because it changes the composition of the deposit. Alkali sulphates are much less corrosive than alkali chlorides partly because they do not form chromate(VI).
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| 16. |
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