Change search
Refine search result
1 - 16 of 16
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Jonsson, Carrie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deposit formation in a grate-kiln plant for iron-ore pellet production: Part 1: Characterization of process gas particles2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6159-6170Article in journal (Refereed)
    Abstract [en]

    Slag formation in the grate-kiln process is a major problem for iron-ore pellet producers. It is therefore important to understand the slag formation mechanism in the grate-kiln production plant. This study initiated the investigation by in situ sampling and identifying particles in the flue gas from a full-scale 40 MW grate-kiln production plant for iron-ore pelletizing. Particles were sampled from two cases of combustion with pulverized coal and heavy fuel oil. The sampling location was at the transfer chute that was situated between the traveling grate and the rotary kiln. The particle-sampling system was set up with a water-cooled particle probe equipped with nitrogen gas dilution, cyclone, and low-pressure impactor. Sub-micrometer and fine particles were size-segregated in the impactor, while coarse particles (>6 μm) were separated with a cyclone before the impactor. Characterization of these particles was carried out with environmental scanning electron microscopy (ESEM), and the morphology of sub-micrometer particles was studied with transmission electron microscopy (TEM). The results showed that particles in the flue gas consisted principally of fragments from iron-ore pellets and secondarily of ashes from pulverized coal and heavy fuel oil combustions. Three categories of particle modes were identified: (1) sub-micrometer mode, (2) first fragmentation mode, and (3) second fragmentation mode. The sub-micrometer mode consisted of vaporized and condensed species; relatively high concentrations of Na and K were observed for both combustion cases, with higher concentrations of Cl and S from heavy fuel oil combustion but higher concentrations of Si and Fe and minor P, Ca, and Al from coal combustion. The first fragmentation mode consisted of both iron-ore pellet fines and fly ash particles; a significant increment of Fe (>65 wt %) was observed, with higher concentrations of Ca and Si during heavy fuel oil combustion but higher concentrations of Si and Al during coal combustion. The second fragmentation mode consisted almost entirely of coarse iron-ore pellet fines, predominantly of Fe (90 wt %). The particles in the flue gas were dominantly iron-ore fines because the second fragmentation mode contributed >96 wt % of the total mass of collected particles.

  • 2.
    Jonsson, Carrie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Comparison of particle and deposit formation between a full-scale grate-kiln plant (40 MW) and a pilot-scale pulverised coal-fired furnace (400 kW)2013Conference paper (Refereed)
    Abstract [en]

    The iron ore pelletizing industry utilizes the grate-kilnprocess to dry and sinter the pellets into finished product.The grate-kiln process has a known deposit formation issuethat needs to be further understood. Combustion ofpulverised coal in the rotary kiln generates fly ash particles;in addition to that, particles generated from disintegratediron ore pellets are also entrained in the process gas stream.The combined effect of both sources of particles cantherefore contribute to the deposit formation in the process.In this work, particle- and deposit formation were studiedboth from a full-scale grate-kiln plant (40 MW) and from apilot-scale pulverised coal fired furnace (400 kW). Particleswere collected with a water-cooled probe with nitrogen gasas dilution medium at the tip of the probe. The particleswere separated simultaneously with a pre-cyclone and a 13stages low-pressure impactor during samplings. Depositswere collected with a refractory plate which was attachedat the tip of a water-cooled probe, exposed to the hightemperature (>1100 °C) process gas stream. Particles anddeposits were characterized with an environmentalscanning electron microscope and a scanning electronmicroscope that equipped with energy dispersivespectroscopy detector. A comparison of particle and depositcharacteristics between the grate-kiln plant and the pilotscale pulverised coal fired furnace is presented in this paper,with focus on the potential influence of disintegrated ironore pellets on the particle- and deposit formation process.

  • 3.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Eriksson, Kjell
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Modelling of refractory brick furniture in rotary-kiln using finite element approach2014In: 11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) / [ed] Eugenio Oñate; Xavier Oliver; Antonio Huerta, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2014, Vol. 2, p. 1199-1210Conference paper (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 4.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Degradation mechanisms in refractory lining materials of rotary kilns for iron ore pellet production2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Iron is one of the most important resources in the lithosphere; 90% of all metal ores extracted are based on iron. Many steps are included in the extraction of iron from ore, with extraction processes varying among different producers. Iron ore pellets are a prepared burden material for ironmaking in the blast furnace or by direct reduction. Such pellets can be sintered in a grate-kiln furnace system, in which the kiln is usually lined with mullite-containing bricks. These bricks degrade by various mechanisms, and need to be replaced regularly, which causes expensive production stops. Materials deposit in chunks on the lining in the kiln. These deposits comprise ~95% hematite with oxides of alkali metals, alkaline earth metals and others, which originate mainly from pellets that have disintegrated, but also from fly-ash from the burner fuel used to heat the kiln.This study investigated the interaction of deposit materials with refractory lining bricks in kilns during the sintering process in iron ore pellet production. Results are obtained from laboratory scale experiments, and from samples collected from industrial kilns, both in-situ and during production stops. Refractory/deposit compatibility tests were performed in a laboratory furnace at various temperatures, for different holding times, and in a number of atmospheres. Deposit materials collected from three commercial lining bricks in production kilns were analysed in both powder and solid forms. Deliberate additions of alkali species (carbonates of potassium and sodium) were made in order to evaluate their influence on degradation mechanisms.Analysis using scanning electron microscopy, QEMSCAN (quantitative evaluation of minerals by scanning electron microscopy), x-ray diffraction, differential scanning calorimetry, thermogravimetry and in-situ mass spectrometry confirmed that alkali additions in the deposit materials dissolve mullite in the liner bricks, which accelerates degradation. Phases such as nepheline (Na2O·Al2O3·2SiO2), kalsilite (K2O·Al2O3·2SiO2), leucite (K2O·Al2O3·4SiO2) and potassium β-alumina (K2O·11Al2O3) were formed. Moreover, it was observed that potassium penetrates deeper into the lining material, and in larger amounts, than sodium, both on the laboratory scale and in industrial furnaces. Formations of alkalicontaining phases such as the feldspathoid minerals kalsilite and nepheline are coupled with an expansion in the lining material, observed by dilatometry, which causes structural spalling that appears as cracks in some of the refractory/deposit compatibility tests. Grains of hematite with sizes between 50-100 μm remain on the original surface of the brick, whereas micrometer-scale hematite migrates through capillary infiltration (in pores, brick joints and cracks) and diffusion, and appears in finer grains deeper in the lining material. The degradation mechanisms of the bricks in an iron ore pellet producing kiln are shown to involve these chemical reactions in combination with thermomechanical stresses. Recommendations are given regarding the choice of materials, the design of refractory liners in the kilns to extend the time between production stops necessary for repair.

    Download full text (pdf)
    FULLTEXT01
  • 5.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Degradation of mullite based materials by alkali containing slags2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Iron is one of the most important resources that can be found in the lithosphere; 90 % of all metal ores extracted are iron ore. Many steps are included in the extraction from iron ore to metallic iron, where the processes vary between different producers. Iron ore pellets, are a prepared burden material for ironmaking in the blast furnace. Such pellets are commonly sintered in a grate-kiln furnace system, where the kiln usually is insulated with mullite containing bricks. Different mechanisms wear these bricks and they need to be replaced regularly and this causes production stops. The slag present in the kiln consists of ~95 % hematite, alkali-, alkaline earth- and other oxides, mainly from pellets that have disintegrated and adheres in chunks on the bricks. This study is focusing on the interaction between refractories and slags that occurs in kilns during the sintering process in the iron ore pellet production. Results are shown from lab scale experiments, and from samples collected in industrial furnaces, commonly called rotary kilns. Slag/brick compatibility tests were performed in a laboratory furnace at various temperatures, holding times and atmospheres. Slag collected from a production kiln and three commercial bricks, in powder or solid form, were used. Deliberate additions of alkali species were included in order to evaluate their influence. XRD, DSC, TG and in-situ mass spectrometry confirm that addition of alkali dissolves the mullite in the bricks, and forms the phase nepheline (Na2O•Al2O3•2SiO2), which disintegrate to an amorphous phase at elevated temperature. QEMSCAN were used to view mineralogical mappings of different chemical phases by field image scans. It was found that when alkali penetrates the surface of the brick, besides formation of nepheline, phases as kalsilite (K2O•Al2O3•2SiO2), leucite (K2O•Al2O3•4SiO2) and potassium â-alumina (K2O•11Al2O3) are formed. Also seen is that potassium penetrates deeper, and in larger amounts than sodium in the lining material. Formations of alkali containing phases as the feldspathoid minerals kalsilite and nepheline are coupled to an expansion in the lining material, observed by dilatometry, causing structural spalling observed as cracks in some of the slag/brick compatibility tests. Grains of hematite with sizes between 50- 100 ìm stay on the original surface of the brick, while micrometer sized hematite migrates through the dissolved brick by capillary infiltration and diffusion, and nucleates in needle formations deeper in the lining material. We propose a wear mechanism of the bricks in an iron ore pellet producing kiln that involves these chemical reactions in combination with erosion by the continuously flowing slag.

    Download full text (pdf)
    FULLTEXT01
  • 6.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    High temperature reactions between insulating bricks and iron ore slag in rotary kilns2007In: European School of Materials Science and Engineering, fourth research conference: preceedings of the fourth meeting of the European School of Materials Sciencie and Engineering / [ed] M. Anglada, Barcelona: CPDA-ETSEIB , 2007, p. 69-78Conference paper (Refereed)
    Abstract [en]

    During iron ore pellet production the ore is first ground to a powder and then sintered in a kiln at ~1250ºC. The company LKAB uses a kiln that is ~ 40 m long and ~ 6.5 m in diameter, insulated with Al2O3- and SiO2- containing bricks. The bricks wear and after some time need to be replaced, which is costly and time consuming. This ongoing project aims at understanding the wear mechanisms of these bricks. The technological problem is rather complex; both oxidizing and reducing atmospheres are locally present, as are various alkali species, the thermomechanical load varies, and slag degrades the bricks. The slag consists of ~95% hematite from pellets that have disintegrated and stick to the bricks. Slag/brick compatibility tests were performed in a laboratory furnace at various temperatures, holding times and atmospheres. Slag collected from a production kiln and three commercial bricks, in powder or solid form, were used. Deliberate additions of alkali species in the form of CaO, K2CO3 and Na2CO3 were included in some of the tests. DSC, TG and in-situ mass spectrometry showed an endothermic reaction, together with mass loss and release of oxygen. Analysis and characterization by microscopy and XRD revealed microstructural changes. It is clear from these observations that the slag degrades the refractories by a combination of capillary infiltration and diffusion/chemical reaction. The depth of slag penetration is more affected by increased temperature than increased time. Moreover, the bricks with higher Al2O3 content are more resistant in the presence of alkali species.

  • 7.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ion, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindblom, B.
    LKAB.
    Lab scale study of the depletion of mullite/corundum-based refractories trough reaction with scaffold materials2011In: IOP Conference Series: Materials Science and Engineering: Symposium 16, 2011 (222001-222031) Innovation in Refractories and Traditional Ceramics, IOP Publishing Ltd , 2011, Vol. 18, article id 222004Conference paper (Refereed)
    Abstract [en]

    To investigate the mechanisms underlying the depletion of mullite/corundum-based refractory bricks used in rotary kilns for iron ore pellet production, the reaction mechanisms between scaffold material and refractory bricks have been studied on the laboratory-scale. Alkali additions were used to enhance the reaction rates between the materials. The morphological changes and active chemical reactions at the refractory/scaffold material interface in the samples were characterized using scanning electron microscopy (SEM), thermal analysis (TA) and X-ray diffraction (XRD). No reaction products of alkali and hematite (Fe2O3) were detected; however, alkali dissolves the mullite in the bricks. Phases such as nepheline (Na2OAl2O32SiO2), kalsilite (K2OAl2O32SiO2), leucite (K2OAl2O34SiO2) and potassium β-alumina (K2O11Al2O3) were formed as a consequence of reactions between alkali and the bricks.

  • 8.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nordin, L-O
    LKAB Research and Development, Metlab.
    Odén, Magnus
    Linköping University, Division of Nanostructured Materials.
    Study of the degradation process of refractory bricks in rotary kilns2008In: Global roadmap for ceramics & ICC2 proceedings: 2nd International Congress on Ceramics ; June 29 - July 4, 2008, Verona, Italy / [ed] Alida Bellosi, Faenza: Institute of Science and Technology for Ceramics , 2008Conference paper (Refereed)
    Abstract [en]

    Iron ore pellets are commonly sintered in a kiln insulated with bricks, which wear and need to be replaced regularly. It is desirable to increase the lifetime of those bricks. Slag/brick compatibility tests have been performed in a laboratory furnace. Slag collected from a production kiln, three commercial bricks and additions of alkali were used. Alkali dissolves the mullite in the bricks, and form the phases nepheline and kalsilite. Characterization of the microstructure showed that the degradation of the bricks was enhanced by increased temperature and amount of alkali. The slag penetration depth is more affected by increased temperature than increased dwell time.

  • 9. Stjernberg, Jesper
    et al.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Odén, Magnus
    Linköpings universitet.
    Nordin, Lars-Olof
    LKAB.
    Degradation of refractory bricks used as thermal insulation in rotary kilns for iron ore pellet production: degradation of refractory bricks used as thermal insulation in rotary kilns2009In: International Journal of Applied Ceramic Technology, ISSN 1546-542X, Vol. 6, no 6, p. 717-726Article in journal (Refereed)
    Abstract [en]

    Degradation of bricks in an iron ore pellet producing kiln has been investigated. Lab-scale tests of brick/slag interaction performed under different temperatures, atmospheres, and alkali additions show that addition of alkali dissolves the mullite in the brick and leads to formation of the phase nepheline (Na2O·Al2O3·2SiO2). At a high temperature, the grain boundary where nepheline is formed disintegrates due to volume expansion. At increased temperature, the nepheline transforms to an amorphous phase. Thus, a wear mechanism is proposed in the kiln using these bricks that involves these chemical reactions in combination with erosion by the continuously flowing slag.

  • 10.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ion, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nordin, Lars-Olof
    LKAB.
    Lindblom, Bo
    LKAB.
    Odén, Magnus
    Linköping University, Division of Nanostructured Materials.
    Extended studies of degradation mechanisms in the refractory lining of a rotary kiln for iron ore pellet production2012In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 32, no 8, p. 1519-1528Article in journal (Refereed)
    Abstract [en]

    Changes, over a period of 8 years, in the chemical composition and morphology of deposit and lining materials in a production rotary kiln for iron ore pellet manufacture are described. The following have been studied: two types of refractory brick used as lining material; deposited chunk materials from the lining; the interaction zones between deposits and linings. Morphological changes at the deposit/lining interface, and the active chemical reactions, are established. Larger hematite grains in the deposit material (5–50 μm) primarily remain at the original deposit/lining interface. The remainder penetrates fissures, voids and brick joints, forms a laminar structure with corundum from the bricks, and migrates in grains in the lining material. Potassium penetrates more deeply into the bricks than hematite, resulting in the formation of kalsilite, leucite and potassium β-alumina, which contribute to degradation of the lining.

  • 11.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Isaksson, Ola
    LKAB.
    Ion, John
    The grate-kiln induration machine: history, advantages, and drawbacks, and outline for the future2015In: The Journal of The Southern African Institute of Mining and Metallurgy, ISSN 2411-9717, Vol. 115, no 2, p. 137-144Article in journal (Refereed)
    Abstract [en]

    Iron ore pellets are a preferred feedstock for ironmaking. One method used for pelletizing is the grate-kiln process, first established in 1960. During the past decade, the establishment of new grate-kiln plants has increased rapidly, especially in China, and new constructors of pellet plants have started to operate in the market. It is well known that the grate-kiln method yields a superior and more consistent pellet quality compared with the straight-grate process. However, certain issues exist with the grate-kiln plant, which are discussed here, together with proposed practical solutions.

    Download full text (pdf)
    fulltext
  • 12.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jonsson, Carrie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deposit formation in a grate-kiln plant for iron-ore pellet production: Part 2: Characterization of deposits2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6171-6184Article in journal (Refereed)
    Abstract [en]

    Buildup of deposit material in chunks on refractory linings caused by combustion of various fuels is a well-known problem. This study characterizes the short-term deposits on refractory material in a grate–kiln process, carried out through in situ measurements using a water-cooled probe with a part of a refractory brick mounted in its end. Sampling was carried out during combustion of both oil and coal. A significant difference in deposition rates was observed; deposition during oil firing was negligible compared to coal firing. The deposits are mainly hematite particles embedded in bonding phase, mainly comprising Si, Al, Fe, Ca, and O. Moreover, it was found that the prevailing flue-gas direction determines the formation of the deposits on the probe and that inertial impaction controls the deposition rate. However, this rate can also be affected by the amount of air-borne particles present in the kiln.

  • 13.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindblom, B.
    LKAB.
    Wikström, J.
    LKAB.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Odén, Magnus
    Microstructural characterization of alkali metal mediated high temperature reactions in mullite based refractories2010In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 36, no 2, p. 733-740Article in journal (Refereed)
    Abstract [en]

    Two types of refractory bricks were used in reaction tests with slag from a production kiln for iron ore pellet production. Electron microscopy was used to characterize morphological changes at the slag/brick interface and active chemical reactions. Phases such as kalsilite, nepheline and potassium β-alumina form, in a layered structure, as a consequence of alkali metals migration in the brick. Larger hematite grains (50-100 μm) in the slag remain at the original slag/brick interface, while smaller grains dissolve and move through the partly dissolved brick bulk, and forms micrometer sized needle shaped crystals deeper in the lining material. Thermodynamic simulations predict the formation of a solid solution between hematite and corundum which is also observed in the reaction zone after extended time periods.

  • 14.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Nordin, Lars-Olof
    LKAB Research and Development, Metlab.
    Ion, John
    Malmö högskola.
    Evaluation of refractory castables and coatings used in the pre-heat zone of a grate-kiln for iron ore pellet production2015In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 42, no 4, p. 274-281Article in journal (Refereed)
    Abstract [en]

    Iron ore pellets are a prepared burden material for ironmaking that are commonly sintered in a grate kiln furnace system. Deposited material can adhere in chunks to localised regions of the lining of such furnaces, causing lining depletion. Such deposits consist mainly of iron oxides, but alkali, alkaline earth and other oxides formed from disintegrated pellets and fly ash may also be present. In order to investigate methods of preventing such formations, tests have been performed using several different castables and coatings. Samples of liner castables with and without coatings, installed in an industrial furnace, were collected after 6 and 24 months in production use, and characterised using scanning electron microscopy to identify the materials, characterise morphological changes at the deposit-coating-lining interface, and to determine the active chemical reactions. An Al2O3 based coating applied to one of the fields was found to be in good condition after 6 months in use, but no traces of the coating were observed after 24 months in use. A carbon phosphate based coating was not intact after 6 months in use; it was probably burned-up as a result of the oxidising atmosphere. Hematite grains from the deposit material remained at the original deposit-lining interface, while calcium migrated further into the lining.

  • 15.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. LKAB.
    Olivas-Ogaz, M.A.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ion, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindblom, B.
    LKAB.
    Laboratory scale study of the degradation of mullite/corundum refractories by reaction with alkali-doped deposit materials2013In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 39, no 1, p. 791-800Article in journal (Refereed)
    Abstract [en]

    Refractory bricks based on mullite and corundum, commonly used in rotary kilns for iron ore pellet production, and depositmaterial from an iron ore pellet production kiln, were used in laboratoryscale tests to investigate refractory/depositreactions and the infiltration of deposit components into the refractory bricks. The materials tested were in both monolithic form and in the form of powder. Alkali metal carbonates (containing sodium and potassium) were used as corrosive agents, to increase reaction kinetics. The morphological changes and active chemical reactions at the refractory/deposit interface in the samples were characterized by scanning electron microscopy. X-ray diffraction showed that alkali metals react with the mullite in the bricks, this being more pronounced in the case of sodium than potassium. Phases such as nepheline (Na2O·Al2O3·2SiO2), kalsilite and kaliophilite (both K2O·Al2O3·2SiO2), and leucite (K2O·Al2O3·4SiO2) were formed as a consequence of reactions between alkali metals and the refractory bricks. The formation of these phases causes volume expansions of between 20% and 25% in the brick materials, which accelerate degradation.

  • 16.
    Wiinikka, Henrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Weiland, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pettersson, Esbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Öhrman, Olov
    Carlsson, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Characterisation of submicron particles produced during oxygen blown entrained flow gasification of biomass2014In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 161, no 7, p. 1923-1934Article in journal (Refereed)
    Abstract [en]

    In this paper submicron particles sampled after the quench during 200 kW, 2 bar(a) pressurised, oxygen blown gasification of three biomass fuels, pure stem wood of pine and spruce, bark from spruce and a bark mixture, have been characterised with respect to particle size distribution with a low pressure cascade impactor. The particles were also characterised for morphology and elemental composition by a combination of scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and high resolution transmission electron microscopy/energy dispersive spectroscopy/selected area electron diffraction pattern (HRTEM/EDS/SAED) techniques. The resulting particle concentration in the syngas after the quench varied between 46 and 289 mg/Nm3 consisting of both carbon and easily volatile ash forming element significantly depending on the fuel ash content. Several different types of particles could be identified from classic soot particles to pure metallic zinc particles depending on the individual particle relation of carbon and ash forming elements. The results also indicate that ash forming elements and especially zinc interacts in the soot formation process creating a particle with shape and microstructure significantly different from a classical soot particle.

1 - 16 of 16
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf