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Andersson, Charlotte
Publications (10 of 29) Show all publications
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: 2019-04-24Bibliographically 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
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
Kumar, T. S., Nurni, V., Ahmed, H., Andersson, C. & Björkman, B. (2017). Erratum to: Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer [Letter to the editor]. Metallurgical and materials transactions. B, process metallurgy and materials processing science, 48(1), 743-745
Open this publication in new window or tab >>Erratum to: Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer
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2017 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 1, p. 743-745Article in journal, Letter (Refereed) Published
Abstract [en]

Authors have used a new way for measuring bulk volume based on the image (pixel) analysis named as Light Table Imaging (LTI), and subsequently bulk densities and porosities. Authors lately found that there was a slight error in calibrating the scale (known distance) to pixel measurement and understand the need to communicate the error and subsequent corrections.  

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Metallurgical process, Manufacturing engineering
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-60524 (URN)10.1007/s11663-016-0843-2 (DOI)000392295500071 ()2-s2.0-84992365208 (Scopus ID)
Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2018-07-10Bibliographically approved
Kumar, T. S., Nurni, V., Ahmed, H., Andersson, C. & Björkman, B. (2017). Erratum to: Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer (ed.) [Letter to the editor]. Metallurgical and materials transactions. B, process metallurgy and materials processing science, 48(1), 746-748
Open this publication in new window or tab >>Erratum to: Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer
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2017 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 1, p. 746-748Article in journal, Letter (Refereed) Published
Abstract [en]

Authors have used a new way for measuring bulk volume based on the image (pixel) analysis named as Light Table Imaging (LTI), and subsequently bulk densities and porosities. Authors lately found that there was a slight error in calibrating the scale (known distance) to pixel measurement and understand the need to communicate the error and subsequent corrections.  

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Chemical engineering - Metallurgical process and manufacturing engineering
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-60075 (URN)10.1007/s11663-016-0844-1 (DOI)000392295500072 ()2-s2.0-84992723871 (Scopus ID)
Available from: 2016-11-01 Created: 2016-11-01 Last updated: 2018-09-28Bibliographically approved
Kumar, T. S., Nurni, V., Ahmed, H. M., Andersson, C. & Björkman, B. (2016). Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer (ed.). Metallurgical and materials transactions. B, process metallurgy and materials processing science, 47(1), 309-319
Open this publication in new window or tab >>Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer
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2016 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 1, p. 309-319Article in journal (Refereed) Published
Abstract [en]

During induration of magnetite pellets, oxidation of magnetite followed by sintering of the oxidized magnetite (hematite) is desirable. Sintering of magnetite which hampers the oxidation of magnetite is aimed to be kept as low as possible. In succession to our earlier study on sintering behavior of oxidized magnetite (hematite), this paper focusses on the sintering behavior of magnetite phase in isolation with an objective to estimate their kinetic parameters. The pellets prepared from the concentrate of LKAB’s mine, which majorly contains (>95 pct) magnetite, are used for the sintering studies. Optical Dilatometer is used to capture the sintering behavior of the magnetite pellet and determine their isothermal kinetics by deducing the three parameters, namely—activation energy (Q), pre-exponential factor (K′), and time exponent (n) with the help of power law and Arrhenius equation. It is interesting to find that the time exponent (n) is decreasing with the increase in sintering temperature. It is also interesting to note that the activation energy for sintering of magnetite pellet shows no single value. From the present investigation, two activation energies—477 kJ/mole [1173 K to 1373 K (900 °C to 1100 °C)] and 148 kJ/mole [1373 K to 1623 K (1100 °C to 1350 °C)]—were deduced for sintering of magnetite, suggesting two different mechanisms operating at lower and other at higher temperatures. The estimated kinetic parameters were used to predict the non-isothermal sintering behavior of magnetite using the sintering kinetic model. Predicted results were validated using experimental data.

Keywords
Chemical engineering - Metallurgical process and manufacturing engineering, Kemiteknik - Metallurgisk process- och produktionsteknik
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-14333 (URN)10.1007/s11663-015-0505-9 (DOI)000368692300031 ()2-s2.0-84958180660 (Scopus ID)db037374-5a60-4d9a-9d90-01338adc1d16 (Local ID)db037374-5a60-4d9a-9d90-01338adc1d16 (Archive number)db037374-5a60-4d9a-9d90-01338adc1d16 (OAI)
Note

Validerad; 2016; Nivå 2; 20151122 (kamsan)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-12-14Bibliographically approved
Kumar, T. S., Nurni, V., Ahmed, H., Andersson, C. & Björkman, B. (2016). Sintering Mechanism of Magnetite Pellets during Induration (ed.). In: (Ed.), : . Paper presented at International Conference on Process Development in Iron and Steelmaking : 13/06/2016 - 15/06/2016.
Open this publication in new window or tab >>Sintering Mechanism of Magnetite Pellets during Induration
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2016 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

In Europe, Sweden has the richest magnetite ore deposits. The mined magnetite ore is ground, beneficiated and pelletized to make the process sustainable and environment friendly. These pellets are subsequently processed in blast furnaces, and hence the optimum pellet quality is of utmost important. Magnetite green pellets are indurated (heat hardened) in either rotary kiln or straight grate induration furnace to attain the quality standards in terms of strength and other metallurgical properties. The quality of magnetite pellet is primarily determined by the physico-chemical changes the pellet undergoes as it makes excursion through the gaseous and thermal environment in the induration furnace. Among these physico-chemical processes, the oxidation of magnetite phase and the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital. Rates of these processes not only depend on the thermal and gaseous environment the pellet gets exposed in the induration reactor but are also interdependent on each other. Therefore, a systematic study has been done to understand these processes in isolation to the extent possible and quantify them seeking the physics.Optical Dilatometer was used in a novel way to design the experiments on single pellets, exposed to different thermal profiles, in order to quantify the sintering of oxidized magnetite and non-oxidized magnetite, independently. Power law (Kt^n) and Arrhenius (푙n(TK(1^n) = ln K' - Q/RT) equations quantifies sintering behavior by estimating three isothermal kinetic parameters, namely – activation energy (Q), pre-exponential factor (K’) and time exponent (n). The values of activation energy and time exponent derived suggests that sintering of oxidized magnetite (hematite) is a single dominant diffusion mechanism, whereas sintering of unoxidized magnetite might be a combination of two distinct mechanisms; one operating at lower temperatures and the other at higher temperatures. The isothermal sintering kinetic equation is also extended to predict the non-isothermal sintering, and validated with the laboratory experiments. This will be further useful in predicting the sintering state of pellets during induration in the plant scale operations.

National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-39755 (URN)e9e2c0d6-7bf6-4ae5-97b6-c5ac75daba41 (Local ID)e9e2c0d6-7bf6-4ae5-97b6-c5ac75daba41 (Archive number)e9e2c0d6-7bf6-4ae5-97b6-c5ac75daba41 (OAI)
Conference
International Conference on Process Development in Iron and Steelmaking : 13/06/2016 - 15/06/2016
Note

Godkänd; 2016; 20160616 (kamsan)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-05-28Bibliographically approved
Nellros, F., Thurley, M., Jonsson, H., Andersson, C. & Forsmo, S. (2015). Automated measurement of sintering degree in optical microscopy through image analysis of particle joins (ed.). Paper presented at . Pattern Recognition, 48(11), 3451-3465
Open this publication in new window or tab >>Automated measurement of sintering degree in optical microscopy through image analysis of particle joins
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2015 (English)In: Pattern Recognition, ISSN 0031-3203, E-ISSN 1873-5142, Vol. 48, no 11, p. 3451-3465Article in journal (Refereed) Published
Abstract [en]

In general terms, sintering describes the bonding of particles into a more coherent structure, where joins form between packed particles, usually as a result of heating. Characterization of sintering is an important topic in the fields of metallurgy, steel, iron ore pellets, ceramics, and snow for understanding material properties and material strength. Characterization using image analysis has been applied in a number of these fields but is either semi-automatic, requiring human interaction in the analysis, or based on statistical sampling and stereology to characterize the sample. This paper presents a novel fully automatic image analysis algorithm to analyze and determine the degree of sintering based on analysis of the particle joins and structure. Quantitative image analysis of the sintering degree is demonstrated for samples of iron ore pellets but could be readily applied to other packed particle materials. Microscope images of polished cross-sections of iron ore pellets have been imaged in their entirety and automated analysis of hundreds of images has been performed. Joins between particles have been identified based on morphological image processing and features have been calculated based on the geometric properties and curvature of these joins. The features have been analyzed and determined to hold discriminative power by displaying properties consistent with sintering theory and results from traditional pellet diameter measurements on the heated samples, and a statistical evaluation using the Welch t-test.

National Category
Signal Processing Computer Sciences
Research subject
Signal Processing; Dependable Communication and Computation Systems
Identifiers
urn:nbn:se:ltu:diva-12912 (URN)10.1016/j.patcog.2015.05.012 (DOI)000359028900015 ()2-s2.0-84937814900 (Scopus ID)c0f7d54d-414d-4f70-9a87-df78138249b5 (Local ID)c0f7d54d-414d-4f70-9a87-df78138249b5 (Archive number)c0f7d54d-414d-4f70-9a87-df78138249b5 (OAI)
Projects
HLRC PIA - Automated Image Analysis for Quantitative Characterisation of Iron Ore Pellet Structures
Note
Validerad; 2015; Nivå 2; 20130224 (frinel)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Kumar, T. S., Ahmed, H., Nurni, V., Andersson, C. & Magnusson, G. (2015). Effect of Heating Rates on the Sintering of Oxidized Magnetite Pellets during Induration (ed.). In: (Ed.), : . Paper presented at European Steel Technology and Application Days : METEC 16/06/2015 - 19/06/2015.
Open this publication in new window or tab >>Effect of Heating Rates on the Sintering of Oxidized Magnetite Pellets during Induration
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2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Magnetite pellet induration is a combination of complex physicochemical phenomena – oxidation, sintering and theheat transfer associated with them. Depending on the pellet properties and the environment it encounters duringthe induration, the oxidation and sintering course may vary and the mechanisms will interact. To be able to predict their course and control it, the kinetics of these phenomena needs to be understood. One approach is to determine the kinetics of the phenomena in isolation. The present investigation is aimed to predict and studying the sintering behavior of oxidized magnetite (hematite) pellets exposed to different heating rates. Experiments have been carefully performed at three different heating rates to capture the sintering behavior during induration using an optical dilatometer, and also used for validation.

National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-34576 (URN)8cf53bf5-9b3c-4fb4-affc-6b13c7793886 (Local ID)8cf53bf5-9b3c-4fb4-affc-6b13c7793886 (Archive number)8cf53bf5-9b3c-4fb4-affc-6b13c7793886 (OAI)
Conference
European Steel Technology and Application Days : METEC 16/06/2015 - 19/06/2015
Note

Godkänd; 2015; 20150617 (kamsan)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-28Bibliographically approved
Kumar, T. S., Nurni, V., Ahmed, H., Andersson, C. & Björkman, B. (2015). Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer (ed.). Metallurgical and materials transactions. B, process metallurgy and materials processing science, 46(2), 635-643
Open this publication in new window or tab >>Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer
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2015 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 2, p. 635-643Article in journal (Refereed) Published
Abstract [en]

The quality of magnetite pellet is primarily determined by the physico-chemical changes thepellet undergoes as it makes excursion through the gaseous and thermal environment in theinduration furnace. Among these physico-chemical processes, the oxidation of magnetite phaseand the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital.Rates of these processes not only depend on the thermal and gaseous environment the pellet getsexposed in the induration reactor but also interdependent on each other. Therefore, a systematicstudy should involve understanding these processes in isolation to the extent possible andquantify them seeking the physics. With this motivation, the present paper focusses on investigatingthe sintering kinetics of oxidized magnetite pellet. For the current investigation, sinteringexperiments were carried out on pellets containing more than 95 pct magnetiteconcentrate from LKAB’s mine, dried and oxidized to completion at sufficiently low temperatureto avoid sintering. The sintering behavior of this oxidized pellet is quantified throughshrinkage captured by Optical Dilatometer. The extent of sintering characterized by sinteringratio found to follow a power law with time i.e., Ktn. The rate constant K for sintering wasdetermined for different temperatures from isothermal experiments. The rate constant, K, varieswith temperature as lnTKð1=nÞ ¼ lnK0 QRT ; and the activation energy (Q) and reaction rateconstant (K¢) are estimated. Further, the sintering kinetic equation was also extended to a nonisothermalenvironment and validated using laboratory experiments.

Keywords
Chemical engineering - Metallurgical process and manufacturing engineering, Kemiteknik - Metallurgisk process- och produktionsteknik
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-7185 (URN)10.1007/s11663-014-0273-y (DOI)000351860300014 ()2-s2.0-84939991633 (Scopus ID)581fa362-ad77-437b-ab37-6fa66414b87d (Local ID)581fa362-ad77-437b-ab37-6fa66414b87d (Archive number)581fa362-ad77-437b-ab37-6fa66414b87d (OAI)
Note

Validerad; 2015; Nivå 2; 20141225 (kamsan)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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