Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 12) Show all publications
Alipour, Y. & Henderson, P. (2015). Corrosion of furnace wall materials in waste-wood fired power plant. Corrosion Engineering, Science and Technology, 50(5), 355-363
Open this publication in new window or tab >>Corrosion of furnace wall materials in waste-wood fired power plant
2015 (English)In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 50, no 5, p. 355-363Article in journal (Refereed) Published
Abstract [en]

Corrosion tests were performed with four different materials exposed at the furnace wall in a power boiler burning recycled wood, with the aim of evaluating coatings to reduce the corrosion. The nickel base Alloy 625 and the iron-chromium-aluminium alloy Kanthal APMT had the lowest corrosion rates followed by the stainless steel 310S. The low alloy steel 16Mo3, from which the walls are constructed, had the highest rate. Different corrosion mechanisms were found to occur according to the alloy type. Thermodynamic modelling showed that chlorine gas exists at extremely low levels under the prevailing conditions and the hydrated form is thermodynamically favoured.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-170939 (URN)10.1179/1743278214Y.0000000228 (DOI)000356438000003 ()2-s2.0-84947433245 (Scopus ID)
Note

QC 20150714

Available from: 2015-07-14 Created: 2015-07-13 Last updated: 2017-12-04Bibliographically approved
Alipour, Y., Henderson, P. & Szakalos, P. (2015). Effect of temperature on corrosion of furnace walls in a waste wood fired boiler. Materials at High Temperature, 32(1-2), 188-196
Open this publication in new window or tab >>Effect of temperature on corrosion of furnace walls in a waste wood fired boiler
2015 (English)In: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 32, no 1-2, p. 188-196Article in journal (Refereed) Published
Abstract [en]

One way of reducing the furnace wall corrosion is to lower the temperature of the wall by reducing the boiler pressure. To test this, four coupons of 16Mo3 were exposed in the furnace wall of a waste wood fired boiler for 1075 h. The temperatures of the samples were individually controlled in the range 280-410 degrees C. The corrosion rates and corrosion mechanism were investigated. The deposits were analysed by XRD and SEM/EDS. The corrosion fronts were studied by focused ion beam milling (FIB)/EDS. The environment was modelled by Thermo-Calc. The amount of potassium and chlorine in the deposit decreased with decreasing temperature. The FIB sections showed a distinctive iron chloride layer at the corrosion front, with an outer layer of iron oxide. The corrosion rate decreased with decreasing metal temperature, but the boiler pressure needs to be reduced to a low level to achieve this, which is not beneficial for the electrical efficiency and therefore not a viable way of reducing corrosion.

Keywords
High temperature corrosion, Microscopy of cross-section corrosion, Biomass, Chlorine induced attack, Thermodynamic modelling, 16Mo3, Waterwalls
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-161149 (URN)10.1179/0960340914Z.000000000100 (DOI)000348713300025 ()2-s2.0-84942413073 (Scopus ID)
Note

QC 20150318

Available from: 2015-03-18 Created: 2015-03-09 Last updated: 2017-12-04Bibliographically approved
Alipour, Y. (2015). Furnace Wall Corrosion in a Wood-fired Boiler. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Furnace Wall Corrosion in a Wood-fired Boiler
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of renewable wood-based fuel has been increasing in the last few decades because it is said to be carbon neutral. However, wood-based fuel, and especially used wood (also known as recycled wood or waste wood), is more corrosive than virgin wood (forest fuel), because of higher amounts of chlorine and heavy metals. These elements increase the corrosion problems at the furnace walls where the oxygen level is low.

Corrosion mechanisms are usually investigated at the superheaters where the temperature of the material and the oxygen level is higher than at the furnace walls.  Much less work has been performed on furnace wall corrosion in wood or used wood fired boilers, which is the reason for this project.    Tests are also mostly performed under simplified conditions in laboratories, making the results easier to interpret.  In power plants the interpretation is more complicated. Difficulties in the study of corrosion processes are caused by several factors such as deposit composition, flue gas composition, boiler design, and combustion characteristics and so on. Therefore, the laboratory tests should be a complement to the field test ones. This doctoral project involved in-situ testing at the furnace wall of power boilers and may thus contribute to fill the gap.

The base material for furnace walls is a low alloy steel, usually 16Mo3, and the tubes may be coated or uncoated. Therefore tests were performed both on 16Mo3 and more highly alloyed materials suitable for protective coatings.

Different types of samples exposed in used-wood fired boilers were analysed by different techniques such as LOM (light optical microscopy), XRD (X-ray diffraction), SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), WDS (wavelength dispersive spectroscopy), FIB (focused ion beam) and GD-OES (glow discharge optical emission spectroscopy). The corrosion rate was measured. The environment was also thermodynamically modelled by TC (Thermo-Calc ®).

The results showed that 16Mo3 in the furnace wall region is attacked by HCl, leading to the formation of iron chloride and a simultaneous oxidation of the iron chloride. The iron chloride layer appeared to reach a steady state thickness.  

Long term exposures showed that A 625 (nickel chromium alloy) and Kanthal APMT (iron-chromium-aluminium alloy) had the lowest corrosion rate (about 25-30% of the rate for 16Mo3), closely followed by 310S (stainless steel), making these alloys suitable for coating materials. It was found that the different alloys were attacked by different species, although they were exposed in the boiler at the same time in the same place. The dominant corrosion process in the A 625 samples seemed to be by a potassium-lead combination, while lead did not attack the APMT samples. Potassium attacked the alumina layer in the APMT samples, leading to the formation of a low-protective aluminate and chlorine was found to attack the base material.  The results showed that stainless steels are attacked by both mechanisms (Cl- induced attack and K-Pb combination).

Decreasing the temperature of the furnace walls of a waste wood fired boiler could decrease the corrosion rate of 16Mo3. However, this low corrosion rate corresponds to a low final steam pressure of the power plant, which in not beneficial for the electrical efficiency.

The short term testing results showed that co-firing of sewage sludge with used wood can lead to a reduction in the deposition of K and Cl on the furnace wall during short term testing. This led to corrosion reduction of furnace wall materials and coatings. The alkali chlorides could react with the aluminosilicates in the sludge and be converted to alkali silicates. The chromia layer in A 625 and alumina in APMT were maintained with the addition of sludge. 

Abstract [sv]

Förnybara träbaserade bränslen har ökat i användning under de senaste decennierna, eftersom det är koldioxidneutrala. Emellertid är träbaserade bränslen, och i synnerhet använt trä (även känt som återvunnet trä, returträ eller träavfall), mer korrosivt än skogsbränsle, på grund av högre halter klor och tungmetaller. Dessa ökar korrosionsproblemen på eldstadsväggarna, särskilt på platser där syrehalten är låg.

Korrosionsmekanismer undersöks vanligtvis på överhettare dvs. på områden där materialets temperatur och syrenivån är högre än vid eldstadsväggarna. Färre arbeten har utförts på eldstadskorrosion i returträ pannor, vilket är motiveringen till detta projekt. Normalt sätt så görs endast i laboratorietester där resultaten är lättare att tolka. I kraftverk är tolkningen mer komplicerad. Undersökningar av korrosionsprocesser försvåras av flera faktorer såsom panndesign, förbränningsegenskaper, rökgassammansättning, beläggningskemi och så vidare. Därför bör laboratorietester kompletteras med fältförsök. Detta doktorandprojekt kan således bidra till att fylla denna brist.

Eldstadsväggarna är uppbyggda av flera rör som svetsas samman och de består vanligtvis av 16Mo3 stål. Rören kan vara belagda eller obelagda. Tester har därför genomförts på 16Mo3 samt på höglegerade material vilka är lämpliga som skyddande beläggningar.

Olika typer av prov som exponerats i förbränningspannor av returträ analyserades med olika tekniker såsom SEM (svepelektronmikroskopi), EDS (energidispersiv spektroskopi), WDS (våglängd dispersiv spektroskopi), FIB (fokuserad jonstråle) LOM (ljusoptisk mikroskopi), XRD (röntgendiffraktion), och GD-OES (glimurladdning med optisk emissionsspektroskopi). Miljön samt korrosionsprocesser har modellerats termodynamiskt med mjukvaran TC (Termo-Calc®).

Resultaten visade att 16Mo3 i eldstadsväggen angrips av väteklorid, vilket leder till bildning av järnklorid och en samtidig oxidation av järnkloriden. Järnkloridskiktet verkade nå ett stationärt tillstånd vad avser tjocklek.

Sex veckors prov visade att A 625 (nickelkromlegering) och Kanthal APMT (järnkromaluminiumlegering) hade den lägsta korrosionshastigheten (ca 25-30% av korrosionshastigheten för 16Mo3), följt av 310S (rostfritt stål). Vi har funnit att de olika legeringarna angrips genom olika mekanismer, även om de var exponerade i pannan samtidigt på samma plats. Den dominerande korrosionsmekanismen för legeringen A 625 verkar i huvudsak bero på kalium och bly, medan bly inte attackerar Kanthal APMT. Kalium angriper aluminiumoxidskiktet på Kanthal APMT, vilket leder till bildning av icke-skyddande aluminat medan klor i sin tur attackerar basmaterialet. Resultaten visar att rostfritt stål attackeras genom klor-inducerad korrosion samt kalium och bly i kombination.

Reducering av temperaturen kan minska korrosionshastigheten hos 16Mo3. Men denna lägre korrosionshastighet motsvarar ett lågt slutligt ångtryck hos kraftverket, vilket inte är fördelaktigt för elverkningsgraden.

De kortare exponeringarna visade att samtidig förbränning av avloppsslam med returträ kan leda till minskad avsättning av kalium och klor i form av alkaliklorider på eldstadsväggarna. Detta ledde till korrosionsminskning av alla studerade material. Dessa alkaliklorider skulle kunna reagera med aluminiumsilikaterna från slammet och omvandlas till alkalisilikater. Detta verkar minska den alkali-inducerade korrosionen på A 625, APMT och 310S. Den aluminiumoxid som bildades på APMT och det kromoxidskikt som bildades på A 625 upprätthölls med tillsats av slam.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. p. xx, 73
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:52
Keywords
High Temperature Corrosion, Used-wood Fired Boilers, Furnace Wall Corrosion, Cl-induced Corrosion, 16Mo3, Nickel-based Alloys, FeCrAl Alloys, Fuel Additive, Sewage Sludge, >Thermodynamics Modelling, Högtemperaturkorrosion, Returträ Förbränningspannor, Eldstad Korrosion, klor-inducerad korrosion, 16Mo3, Nickelbaslegeringar, FeCrAl-legeringar, Bränsletillsatser, Avloppsslam, Termodynamik Modellering
National Category
Corrosion Engineering
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-175427 (URN)978-91-7595-695-4 (ISBN)
Public defence
2015-11-27, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151015

Available from: 2015-10-15 Created: 2015-10-14 Last updated: 2015-10-29Bibliographically approved
Alipour, Y., Talus, A., Henderson, P. & Norling, R. (2015). The effect of co-firing sewage sludge with used wood on the corrosion of an FeCrAl alloy and a nickel-based alloy in the furnace region. Fuel processing technology, 138, 805-813
Open this publication in new window or tab >>The effect of co-firing sewage sludge with used wood on the corrosion of an FeCrAl alloy and a nickel-based alloy in the furnace region
2015 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 138, p. 805-813Article in journal (Refereed) Published
Abstract [en]

The effect of digested sewage sludge as a fuel additive to reduce corrosion of furnace walls has been studied. The nickel base alloy Alloy 625 and the iron-chromium-aluminium alloy Kanthal APMT™ were exposed for 14.25. h at the furnace wall in a power boiler burning 100% used (also known as waste or recycled) wood. The test was then repeated with the addition of sewage sludge to the waste wood. The samples were chemically analysed and thermodynamically modelled and the corrosion mechanisms were investigated. The results showed that the co-firing of sewage sludge with recycled wood leads to a reduction in the corrosion. Attack by a potassium-lead combination appeared to be the main corrosion mechanism in Alloy 625 during waste wood combustion, while attack by alkali chloride was found to be dominant in APMT alloy.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Alloy 625, High temperature corrosion, Kanthal APMT, Sewage sludge, Used wood, Waterwalls
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-175446 (URN)10.1016/j.fuproc.2015.07.014 (DOI)000362920200090 ()2-s2.0-84954196616 (Scopus ID)
Note

QC 20151015

Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2017-12-01Bibliographically approved
Alipour, Y., Henderson, P. & Szakalos, P. (2014). The effect of a nickel alloy coating on the corrosion of furnace wall tubes in a waste wood fired power plant. Materials and corrosion - Werkstoffe und Korrosion, 65(2), 217-225
Open this publication in new window or tab >>The effect of a nickel alloy coating on the corrosion of furnace wall tubes in a waste wood fired power plant
2014 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 65, no 2, p. 217-225Article in journal (Refereed) Published
Abstract [en]

The use of waste wood as a fuel in power plants is becoming more widespread in Europe, because it is a renewable energy source with a lower cost than forest fuel. However it is more corrosive than coal and corrosion problems have arisen in the furnace wall area of a low NOx heat and power boiler. The furnace walls are made of a low alloy steel which has been coated in some parts with a nickel alloy to reduce corrosion. In this work, furnace tubes coated with a nickel alloy were compared to the uncoated tubes of the low alloy steel 16Mo3 after 3 years of exposure in the boiler. The nickel alloy coating and uncoated material were also compared with more controlled testing on a corrosion probe lasting for about 6 weeks. The corrosion rates were measured and the samples were chemically analysed by SEM/EDS/WDS and XRD methods. The corrosive environment was also modelled with Thermo-Calc software. The corrosion rates measured from the probe and tube samples of 16Mo3 agreed well with each other, implying linear corrosion rates. The results also showed that the use of nickel alloy coatings changes the corrosion mechanism, which leads to a dramatic reduction in the corrosion rate. The results are discussed in terms of the corrosion mechanisms and thermodynamic stability of the corrosion products.

Place, publisher, year, edition, pages
Wiley: , 2014
Keywords
16Mo3, alloy 625, furnace wall, high temperature corrosion, nickel coating, waste wood
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-121180 (URN)10.1002/maco.201307118 (DOI)000331999600014 ()
Note

QC 20140404

Available from: 2013-04-22 Created: 2013-04-22 Last updated: 2017-12-06Bibliographically approved
Alipour, Y. & Henderson, P. (2014). The effect of co-firing of sewage sludge with waste wood on furnace wall corrosion. In: International Symposium On High-Temperature Oxidation And Corrosion Hakodate, Hokkaido Japan, 2014, 23-27 June: . Paper presented at ISHOC2014.
Open this publication in new window or tab >>The effect of co-firing of sewage sludge with waste wood on furnace wall corrosion
2014 (English)In: International Symposium On High-Temperature Oxidation And Corrosion Hakodate, Hokkaido Japan, 2014, 23-27 June, 2014Conference paper, Published paper (Refereed)
Keywords
High Temperature Corrosion, Waterwalls, Nickel alloy, CrAl alloy, Stainless Steels, biomass
National Category
Corrosion Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-145877 (URN)
Conference
ISHOC2014
Projects
KME 508: Furnace wall corrosion in biomass-fired boilers at higher steam temperatures and pressures
Funder
Swedish Energy Agency
Note

QC 20140604

Available from: 2014-06-02 Created: 2014-06-02 Last updated: 2014-11-24Bibliographically approved
Alipour, Y. (2013). High temperature corrosion in a biomass-fired power boiler: Reducing furnace wall corrosion in a waste wood-fired power plant with advanced steam data. (Licentiate dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>High temperature corrosion in a biomass-fired power boiler: Reducing furnace wall corrosion in a waste wood-fired power plant with advanced steam data
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The use of waste (or recycled) wood as a fuel in heat and power stations is becoming more widespread in Sweden (and Europe), because it is CO2 neutral with a lower cost than forest fuel. However, it is a heterogeneous fuel with a high amount of chlorine, alkali and heavy metals which causes more corrosion than fossil fuels or forest fuel.

A part of the boiler which is subjected to a high corrosion risk is the furnace wall (or waterwall) which is formed of tubes welded together. Waterwalls are made of ferritic low-alloyed steels, due to their low price, low stress corrosion cracking risk, high heat transfer properties and low thermal expansion. However, ferritic low alloy steels corrode quickly when burning waste wood in a low NOx environment (i.e. an environment with low oxygen levels to limit the formation of NOx). Apart from pure oxidation two important forms of corrosion mechanisms are thought to occur in waste environments: chlorine corrosion and alkali corrosion.

Although there is a great interest from plant owners to reduce the costs associated with furnace wall corrosion very little has been reported on wall corrosion in biomass boilers. Also corrosion mechanisms on furnace walls are usually investigated in laboratories, where interpretation of the results is easier. In power plants the interpretation is more complicated. Difficulties in the study of corrosion mechanisms are caused by several factors such as deposit composition, flue gas flow, boiler design, combustion characteristics and flue gas composition. Therefore, the corrosion varies from plant to plant and the laboratory experiments should be complemented with field tests. The present project may thus contribute to fill the power plant corrosion research gap.

In this work, different kinds of samples (wall deposits, test panel tubes and corrosion probes) from Vattenfall’s Heat and Power plant in Nyköping were analysed. Coated and uncoated samples with different alloys and different times of exposure were studied by scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), X-ray diffraction (XRD) and light optical microscopy (LOM). The corrosive environment was also simulated by Thermo-Calc software.

The results showed that a nickel alloy coating can dramatically reduce the corrosion rate. The corrosion rate of the low alloy steel tubes, steel 16Mo3, was linear and the oxide scale non-protective, but the corrosion rate of the nickel-based alloy was probably parabolic and the oxide much more protective. The nickel alloy and stainless steels showed good corrosion protection behavior in the boiler. This indicates that stainless steels could be a good (and less expensive) alternative to nickel-based alloys for protecting furnace walls.

The nickel alloy coated tubes (and probe samples) were attacked by a potassium-lead combination leading to the formation of non-protective potassium lead chromate. The low alloy steel tubes corroded by chloride attack. Stainless steels were attacked by a combination of chlorides and potassium-lead.

The Thermo-Calc modelling showed chlorine gas exists at extremely low levels (less than 0.1 ppm) at the tube surface; instead the hydrated form is thermodynamically favoured, i.e. gaseous hydrogen chloride. Consequently chlorine can attack low alloy steels by gaseous hydrogen chloride rather than chlorine gas as previously proposed. This is a smaller molecule than chlorine which could easily diffuse through a defect oxide of the type formed on the steel.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. p. 55
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:24
Keywords
High temperature corrosion, Waterwalls, Power plant corrosion, NOx reducing enviroments, Biomass, Waste wood, Thermodynamic calculation modelling, corrosion-resistance alloy, Furnace wall corrosion, Högtemperaturekorrosion, Eldstadsväggar, kraftverks korrosion, låg Nox mijöer, biomassa, returträ, Termodynamisk modellering, korrosionsbeständighet legering, eldstadskorrosion
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-121155 (URN)978-91-7501-741-9 (ISBN)
Presentation
2013-06-10, Rum 3, SP, Drottning Kristinas Väg 45, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130423

Available from: 2013-04-23 Created: 2013-04-21 Last updated: 2013-06-12Bibliographically approved
Alipour, Y. (2012). Reducing furnace wall corrosion by coating the furnace tubes in a waste wood fired boiler plant. In: : . Paper presented at Energy and Materials, Torremolinos, Spain, 20-22 June 2012.
Open this publication in new window or tab >>Reducing furnace wall corrosion by coating the furnace tubes in a waste wood fired boiler plant
2012 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-178173 (URN)
Conference
Energy and Materials, Torremolinos, Spain, 20-22 June 2012
Note

NV 20151208

Available from: 2015-12-07 Created: 2015-12-07 Last updated: 2015-12-08Bibliographically approved
Alipour, Y., Viklund, P. & Henderson, P. (2012). The analysis of furnace wall deposits in a low-NOx waste wood-fired bubbling fluidised bed boiler. VGB PowerTech Journal, 92(12), 96-100
Open this publication in new window or tab >>The analysis of furnace wall deposits in a low-NOx waste wood-fired bubbling fluidised bed boiler
2012 (English)In: VGB PowerTech Journal, ISSN 1435-3199, Vol. 92, no 12, p. 96-100Article in journal (Other academic) Published
Abstract [en]

Increasing use is being made of biomass as fuel for electricity production as the price of natural wood continues to rise. Therefore, more use is being made of waste wood (recycled wood). However, waste wood contains more chlorine, zinc and lead, which are believed to increase corrosion rates. Corrosion problems have occurred on the furnace walls of a fluidised bed boiler firing 100 % waste wood under low-NOx conditions. The deposits have been collected and analysed in order to understand the impact of the fuel.

Place, publisher, year, edition, pages
VGB Power Tech, 2012
Keywords
High Temperature Corrosion, Waterwalls, biomass, FBF boiler, corrosion
National Category
Corrosion Engineering Materials Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-108163 (URN)2-s2.0-84873677836 (Scopus ID)
Funder
StandUp
Note

QC 20130226

Available from: 2013-03-15 Created: 2012-12-19 Last updated: 2013-04-23Bibliographically approved
Alipour, Y., Davis, C., Szakalos, P. & Henderson, P. Corrosion of the low alloy steel 16Mo3 in the furnace region of used-wood fired boilers.
Open this publication in new window or tab >>Corrosion of the low alloy steel 16Mo3 in the furnace region of used-wood fired boilers
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-175447 (URN)
Note

QS 2015

Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2015-10-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0184-7601

Search in DiVA

Show all publications