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Björkman, Bo
Publications (10 of 180) Show all publications
Brämming, M., Engström, F., Samuelsson, C. & Björkman, B. (2019). Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process. Steel Research International, 90(2), Article ID 1800269.
Open this publication in new window or tab >>Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process
2019 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 90, no 2, article id 1800269Article in journal (Refereed) Published
Abstract [en]

In the Basic Oxygen Steelmaking (BOS) process, a heterogeneous emulsion‐solid mix will form, consisting of an emulsion of liquid slag and metal droplets, in which 2nd phase particles of undissolved fluxes and solid in‐blow precipitates are suspended. When the carbon in the metal droplets reacts with iron oxide, small bubbles of CO gas are formed. If the upward movement of these bubbles is obstructed by the physical properties of the emulsion‐solid mix, foaming will occur. Certain process conditions may lead to an excessive foam growth, in the worst case forcing foam out of the vessel. This undesired process event is known as “slopping”. Extensive studies during recent decades have shown that emulsion characteristics strongly connected to foaming are: viscosity, surface tension, and density. The extent of foaming is also dependent on bubble size; foaming increasing with smaller bubble size. However, investigations into the influence of the mineralogy and morphology of the emulsion‐solid mix on foaming in basic oxygen steelmaking are scarce. In this work, samples from trials in a 6‐tonne pilot plant BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology at different stages of the oxygen blow. The study confirms the importance of tight process control in order to minimize the emulsion‐solid mix apparent viscosity and, hence, the foam height, but this without over‐oxidizing the liquid slag phase, which would result in increased gas generation within the slag‐metal emulsion.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
sic oxygen steelmaking (BOS), emulsion characterization, foaming, LD process, mineralogy, morphology, slopping
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-72759 (URN)10.1002/srin.201800269 (DOI)000458361600016 ()2-s2.0-85058014454 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-06 (johcin) 

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-03-08Bibliographically approved
Kumar, T. S., Viswanathan, N. N., Ahmed, H., Dahlin, A., Andersson, C. & Björkman, B. (2019). Developing the Oxidation Kinetic Model for Magnetite Pellet. Metallurgical and materials transactions. B, process metallurgy and materials processing science, 50(1), 162-172
Open this publication in new window or tab >>Developing the Oxidation Kinetic Model for Magnetite Pellet
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2019 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 50, no 1, p. 162-172Article in journal (Refereed) Published
Abstract [en]

Oxidation is a vital phenomenon for magnetite pellets in their excursion through the furnace during induration. One of the pre-requisites for magnetite pellets to achieve homogeneously structured good quality pellets is to have complete oxidation before sintering begins. Partially oxidized magnetite pellets, upon sintering, might result in inhomogeneous structured pellets which could be detrimental to pellet quality. It is necessary to understand the mechanisms responsible for magnetite oxidation, and hence, it is intended in this study to investigate experimentally as well as develop a mathematical model based on oxidation kinetics. Oxidation of pellets is largely influenced by the oxidation kinetics of particles and hence should be studied at particle as well as at pellet scale. The principles of the Grain Model have been adopted to develop the Oxidation Model at pellet scale, whereas the particles’ oxidation follows the Avrami Kinetic Model. Isothermal oxidation experiments performed Thermogravimetric Analyzer showed that oxidation rate of magnetite at pellet scale contained two peaks. They were complemented well by oxidation rates predicted from the model. Further, the pellet was investigated microstructurally at pellet and particle scale to substantiate the findings from the experiments and the model. The oxidation model developed is used to predict the progression of oxidation in the magnetite pellet with respect to the reaction time at three different temperatures (873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C)) and at four levels of oxygen (0.21, 0.30, 0.60, and 1.00 atm) in the oxidizing gas.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Pellet Oxidation Model, Magnetite Pellet, Induration, Grain model
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-71433 (URN)10.1007/s11663-018-1423-4 (DOI)000456070300017 ()2-s2.0-85055995152 (Scopus ID)
Projects
Investigations on the Physico-Chemical Phenomena during Induration of a Magnetite Pellet
Note

Validerad;2019;Nivå 2;2019-02-11 (inah)

Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2019-02-11Bibliographically approved
El-Tawil, A., Ahmed, H., Sundqvist Ökvist, L. & Björkman, B. (2019). Devolatilization Kinetics of Different Types of Bio-Coals Using Thermogravimetric Analysis. Metals, 9(2), Article ID 168.
Open this publication in new window or tab >>Devolatilization Kinetics of Different Types of Bio-Coals Using Thermogravimetric Analysis
2019 (English)In: Metals, E-ISSN 2075-4701, Vol. 9, no 2, article id 168Article in journal (Refereed) Published
Abstract [en]

The interest of the steel industry in utilizing bio-coal (pre-treated biomass) as CO2-neutral carbon in iron-making is increasing due to the need to reduce fossil CO2 emission. In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the current study aims at investigating the thermal devolatilization of different bio-coals. A thermogravimetric analyzer (TGA) equipped with a quadrupole mass spectrometer (QMS) was used to monitor the weight loss and off-gases during non-isothermal tests with bio-coals having different contents of volatile matter. The samples were heated in an inert atmosphere to 1200 °C at three different heating rates: 5, 10, and 15 °C/min. H2, CO, and hydrocarbons that may contribute to the reduction of iron oxide if contained in the self-reducing composite were detected by QMS. To explore the devolatilization behavior for different materials, the thermogravimetric data were evaluated by using the Kissinger– Akahira–Sonuse (KAS) iso-conversional model. The activation energy was determined as a function of the conversion degree. Bio-coals with both low and high volatile content could produce reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates and hot metal quality in the sustained blast furnace process. However, bio-coals containing significant amounts of CaO and K2O enhanced the devolatilization and released the volatiles at lower temperature. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
devolatilization, torrefied biomass, bio-coal, volatile matter, iso-conversional method
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-73181 (URN)10.3390/met9020168 (DOI)2-s2.0-85062329541 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-13 (johcin)

Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-03-13Bibliographically approved
Kumar, T. S., Nurni, V., Ahmed, H., Andersson, C., Dahlin, A. & Björkman, B. (2019). Investigation of Magnetite Oxidation Kinetics at the Particle Scale. Metallurgical and materials transactions. B, process metallurgy and materials processing science, 50(1), 150-161
Open this publication in new window or tab >>Investigation of Magnetite Oxidation Kinetics at the Particle Scale
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2019 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 50, no 1, p. 150-161Article in journal (Refereed) Published
Abstract [en]

The induration of magnetite pellets is a complex physico-chemical process that involves oxidation, sintering, and heat transfer. The thermal- and gas-composition profile that is experienced by the pellet in an induration reactor could result in the formation of a homogenous or heterogeneous pellet structure, which could affect the pellet quality. The oxidation kinetics of magnetite pellets from sintering studies have been studied at two levels, namely, the pellet scale and at the particle scale, and the findings of the latter are presented here. The rate of oxidation of the magnetite concentrate depends primarily on temperature, oxygen content in the oxidizing gas, and particle size. These factors are investigated in this study. It was found that the oxidation of the magnetite concentrate is comprised of two distinct stages, a primary stage with high rates followed by a secondary stage where rates decrease significantly. The isothermal oxidation behavior as analyzed by the Avrami kinetic model was found to fit better than the shrinking-core model. The partially oxidized particles were examined microstructurally to supplement the experimental and model results. The Avrami kinetic model for isothermal oxidation was extended to non-isothermal profiles using the superposition principle, and the model was validated experimentally.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Oxidation Kinetics, Shrinking Core Mechanism, Avrami Mechanism, Magnetite particle oxidation
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-71839 (URN)10.1007/s11663-018-1459-5 (DOI)000456070300016 ()2-s2.0-85057526513 (Scopus ID)
Projects
Investigations on the Physico-Chemical Phenomena during Induration of a Magnetite Pellet
Note

Validerad;2019;Nivå 2;2019-02-01 (johcin) 

Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2019-02-01Bibliographically approved
Lennartsson, A., Engström, F., Björkman, B. & Samuelsson, C. (2019). Understanding the bottom buildup in an electric copper smelting furnace by thermodynamic calculations. Canadian metallurgical quarterly, 58(1), 89-95
Open this publication in new window or tab >>Understanding the bottom buildup in an electric copper smelting furnace by thermodynamic calculations
2019 (English)In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 58, no 1, p. 89-95Article in journal (Refereed) Published
Abstract [en]

Thermodynamic calculations were used to investigate the liquidus temperature of the slag and the possible influence on the buildup formation in an electric copper smelting furnace. The impact of parameters such as Fe/SiO2 ratio, partial pressure of oxygen and the content of the oxides ZnO, Al2O3 and Cr2O3 in the slag were investigated with respect to the liquidus temperature of the slag. Results show that the chromium content in the slag has the greatest impact on the liquidus temperature and on the formation of solid particles. The characterization of the buildup done earlier showed that spinel phases were among the dominating phases. This is supported by the thermodynamic calculations in the present paper, where the chromite solid solution was found to be the primary precipitation phase.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2019
Keywords
Copper smelting, FactSage, Buildup, Thermodynamic calculation, Spinel, Pyrometallurgy, Electric furnace
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-70765 (URN)10.1080/00084433.2018.1518804 (DOI)000452743200008 ()2-s2.0-85053228724 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-30 (inah)

Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2019-01-30Bibliographically approved
Andersson, A., Gullberg, A., Kullerstedt, A., Sandberg, E., Andersson, M., Ahmed, H., . . . Björkman, B. (2018). A Holistic and Experimentally-Based View on Recycling of Off-Gas Dust within the Integrated Steel Plant. Metals, 8(10), Article ID 760.
Open this publication in new window or tab >>A Holistic and Experimentally-Based View on Recycling of Off-Gas Dust within the Integrated Steel Plant
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2018 (English)In: Metals, ISSN 2075-4701, Vol. 8, no 10, article id 760Article in journal (Refereed) Published
Abstract [en]

Ore-based ironmaking generates a variety of residues, including slags and fines such as dust and sludges. Recycling of these residues within the integrated steel plant or in other applications is essential from a raw-material efficiency perspective. The main recycling route of off-gas dust is to the blast furnace (BF) via sinter, cold-bonded briquettes and tuyere injection. However, solely relying on the BF for recycling implicates that certain residues cannot be recycled in order to avoid build-up of unwanted elements, such as zinc. By introducing a holistic view on recycling where recycling via other process routes, such as the desulfurization (deS) station and the basic oxygen furnace (BOF), landfilling can be avoided. In the present study, process integration analyses were utilized to determine the most efficient recycling routes for off-gas dust that are currently not recycled within the integrated steel plants of Sweden. The feasibility of recycling was studied in experiments conducted in laboratory, pilot, and full-scale trials in the BF, deS station, and BOF. The process integration analyses suggested that recycling to the BF should be maximized before considering the deS station and BOF. The experiments indicated that the amount of residue that are not recycled could be minimized.

Place, publisher, year, edition, pages
Basel: MDPI, 2018
Keywords
Recycling, Cold-bonded briquettes, Blast furnace, Desulfurization, Basic oxygen furnace, Dust, Sludge, Fines
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-71130 (URN)10.3390/met8100760 (DOI)000448658700024 ()2-s2.0-85054764975 (Scopus ID)
Funder
Swedish Energy Agency
Note

Validerad;2018;Nivå 2;2018-10-19 (marisr)

Available from: 2018-10-08 Created: 2018-10-08 Last updated: 2018-11-23Bibliographically approved
Kumar, T. K., Simonsson, M., Nurni, V., Ahmed, H., Andersson, C., El-Geassy, A.-H. A. & Björkman, B. (2018). Establishing a Novel Methodology to Correlate the Macroscopic and Microscopic Degree of Sintering inMagnetite Pellets during Induration. Steel Research International, 89(3), Article ID 1700366.
Open this publication in new window or tab >>Establishing a Novel Methodology to Correlate the Macroscopic and Microscopic Degree of Sintering inMagnetite Pellets during Induration
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2018 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 89, no 3, article id 1700366Article in journal (Refereed) Published
Abstract [en]

The quality of product pellets is a result of the physico-chemical phenomenainvolved in the induration process. Sintering is the primary phenomenon,and its degree or extent contributes substantially to the evolution of themetallurgical and mechanical properties of a pellet. During the induration ofmagnetite pellets, sintering proceeds through the oxidized and non-oxidizedmagnetite phases. Sintering of these phases has been previously studied ona single pellet at the macroscopic scale using an optical dilatometer. Adeeper understanding requires corroboration of these studies throughcharacterization at the microscopic scale. In the present work, the observationsrecorded at the microscopic scale are quantified using image processingtechniques to correlate them to the macroscopic measurements. Distancetransformation, which is an image processing principle, is adapted in a novelway to digitize the microstructures and to determine the degree of sinteringin a pellet quantitatively. This methodology has potential applications as ageneric tool to follow the sintering phenomenon and process kinetics at anystage during induration.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
Distance Transform, Induration, Optical Microstructures, Oxidized and Non-oxidized Magnetite Pellets, Sintering Degree
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-66590 (URN)10.1002/srin.201700366 (DOI)000426525900012 ()2-s2.0-85042594552 (Scopus ID)
Projects
Modeling of Physico-Chemical phenomena during Induration of Magnetite Pellet
Note

Validerad;2018;Nivå 2;2018-02-02 (andbra)

Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2018-05-16Bibliographically approved
El-Sadek, M., Ahmed, M., El-Barawy, K., Morsi, M., El-Didamony, H. & Björkman, B. (2018). Non-isothermal carbothermic reduction kinetics of mechanically activated ilmenite containing self-reducing mixtures. Journal of thermal analysis and calorimetry (Print), 131(3), 2457-2465
Open this publication in new window or tab >>Non-isothermal carbothermic reduction kinetics of mechanically activated ilmenite containing self-reducing mixtures
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2018 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 131, no 3, p. 2457-2465Article in journal (Refereed) Published
Abstract [en]

Effect of mechanical activation on carbothermic reduction kinetics and mechanism of ilmenite concentrate containing self-reducing mixture has been investigated using a combination of thermogravimetry and X-ray diffraction. Thermogravimetric comparative study of mechanically activated and non-activated ilmenite concentrate containing self-reducing mixtures with C/O molar ratio of 1.5 was conducted non-isothermally. The samples were heated up to 1573 K at three different heating rates (10, 15, and 20 K min−1) under controlled atmosphere. The reduction mechanism of mechanically activated mixture was followed by X-ray diffraction analysis of arrested samples at different reduction extents. In addition, reaction kinetics was further investigated and corresponding kinetic parameters were estimated using isoconversional (model-free) and model-fitting (Coats–Redfern) methods.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-66100 (URN)10.1007/s10973-017-6743-0 (DOI)000425965400041 ()
Note

Validerad;2018;Nivå 2;2018-02-23 (andbra)

Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2018-03-15Bibliographically approved
Andersson, A., Andersson, M., Mousa, E., Kullerstedt, A., Ahmed, H., Björkman, B. & Sundqvist Ökvist, L. (2018). The Potential of Recycling the High-Zinc Fraction of Upgraded BF Sludge to the Desulfurization Plant and Basic Oxygen Furnace. Paper presented at 8th International Congress on Science and Technology in Ironmaking — 8th ICSTI 2018, September 25 to 27 2018, Vienna.. Metals, 8(12), Article ID 1057.
Open this publication in new window or tab >>The Potential of Recycling the High-Zinc Fraction of Upgraded BF Sludge to the Desulfurization Plant and Basic Oxygen Furnace
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2018 (English)In: Metals, ISSN 2075-4701, Vol. 8, no 12, article id 1057Article in journal (Refereed) Published
Abstract [en]

In ore-based steelmaking, blast furnace (BF) dust is generally recycled to the BF via the sinter or cold-bonded briquettes and injection. In order to recycle the BF sludge to the BF, the sludge has to be upgraded, removing zinc. The literature reports cases of recycling the low-zinc fraction of upgraded BF sludge to the BF. However, research towards recycling of the high-zinc fraction of BF sludge within the ore-based steel plant is limited. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded briquettes and pellets. Each type of agglomerate was individually subjected to technical-scale smelting reduction experiments aiming to study the feasibility of recycling in-plant residues to the hot metal (HM) desulfurization (deS) plant. The endothermic reactions within the briquettes decreased the heating and reduction rate leaving the briquettes unreduced and unmelted. The pellets were completely reduced within eight minutes of contact with HM but still showed melt-in problems. Cold-bonded briquettes, without BF sludge, were charged in industrial-scale trials to study the recycling potential to the HM deS plant and basic oxygen furnace (BOF). The trials illustrated a potential for the complete recycling of the high-zinc fraction of BF sludge. However, further studies were identified to be required to verify these results.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
recycling, blast furnace sludge, smelting reduction, desulfurization, basic oxygen furnace, cold-bonded briquettes, cold-bonded pellets, low-sulfur binders
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-72426 (URN)10.3390/met8121057 (DOI)000455072100081 ()2-s2.0-85058575555 (Scopus ID)
Conference
8th International Congress on Science and Technology in Ironmaking — 8th ICSTI 2018, September 25 to 27 2018, Vienna.
Note

Konferensartikel i tidskrift.

Available from: 2019-01-02 Created: 2019-01-02 Last updated: 2019-02-12Bibliographically approved
Xue, P., Yang, Q., Liu, G., Han, F. L., Liang, J., Engström, F. & Björkman, B. (2017). Air Quenching of Steel slag to Enhance its Hydraulic Activity for Recycling the Slag as Meterials in Cement and Concrete Applications. Paper presented at 2016 International Conference on Material Science and Engineering Technology, ICMSET 2016, Phuket, Thailand, 14-16 October 2016. Key Engineering Materials, 737, 488-493
Open this publication in new window or tab >>Air Quenching of Steel slag to Enhance its Hydraulic Activity for Recycling the Slag as Meterials in Cement and Concrete Applications
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2017 (English)In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 737, p. 488-493Article in journal (Refereed) Published
Abstract [en]

A steel slag has been treated by air granulation, in order to enhance cementitious properties of the slag. Two samples with sizes ranged 1.68-2.38mm and 212-297μm and coded as Slag A and Slag B, respectively, were chosen from the granulated slag for investigations. A sample of the original steel slag was also studied. XRD analyses indicated the formations of α-C2S, β-C2S, C2F, C2MS2, f-MgO and α-C2S, C2F, f-MgO in Slag A and Slag B, respectively. The phases in the two slag samples were quite different from the phases found in steel slag. The SEM results show a reduction of C2S sizes from 10-20μm for the steel slag to nano-scales by air quenching for Slag B. This treatment of air quenching has increased the cumulative heat of hydration to 105.35J/g measured for Slag B, almost two times greater than that of the steel slag. The study results demonstrate a high potential for utilizations of the steel slag in cement and concrete applications after the slag treatment by air quenching. The treatment may thus lead to an environmental friendly and cost-effective recycling for the steel slag. This can also contribute to the sustainable developments in the steel and cement/concrete industries.

Place, publisher, year, edition, pages
Trans Tech Publications, 2017
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-63511 (URN)10.4028/www.scientific.net/KEM.737.488 (DOI)2-s2.0-85027060966 (Scopus ID)
Conference
2016 International Conference on Material Science and Engineering Technology, ICMSET 2016, Phuket, Thailand, 14-16 October 2016
Note

Konferensartikel i tidskrift

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-11-28Bibliographically approved
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