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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Ahmed, Hesham, et al.
(författare)
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Effect of carbon concentration and carbon bonding type on the melting characteristics of hydrogen- reduced iron ore pellets
- 2022
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 21, s. 1760-1769
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Tidskriftsartikel (refereegranskat)abstract
- Decarbonization of the steel industry is one of the pathways towards a fossil-fuel-free environment. The steel industry is one of the top contributors to greenhouse gas emissions. Most of these emissions are directly linked to the use of a fossil-fuel-based reductant. Replacing the fossil-based reductant with green H2 enables the transition towards a fossil-free steel industry. The carbon-free iron produced will cause the refining and steelmaking operations to have a starting point far from today's operations. In addition to carbon being an alloying element in steel production, carbon addition controls the melting characteristics of the reduced iron. In the present study, the effect of carbon content and form (cementite/graphite) in hydrogen-reduced iron ore pellets on their melting characteristics was examined by means of a differential thermal analyser and optical dilatometer. Carburized samples with a carbon content 2 wt%, the molten fraction is higher in the case of carburized samples, which is indicated by the amount of absorbed melting heat.
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| 6. |
- Kumar, T K Sandeep, 1986-, et al.
(författare)
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Establishing a Novel Methodology to Correlate the Macroscopic and Microscopic Degree of Sintering inMagnetite Pellets during Induration
- 2018
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 89:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Kumar, T. K. Sandeep, et al.
(författare)
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Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer
- 2016
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 47:1, s. 309-319
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Kumar, T. K. Sandeep, et al.
(författare)
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Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer
- 2015
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 46:2, s. 635-643
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Kumar, T K Sandeep, 1986-, et al.
(författare)
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Experimental Characterization of Sintering Mechanism using Optical Dilatometer and Push Rod Dilatometer : A Comparative Study
- 2017
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Konferensbidrag (refereegranskat)abstract
- In Iron and Steel industries, sintering process is used in producing agglomerates either as iron ore sinter or as heat hardened iron ore pellets. It is also used extensively used in producing ceramic or metallic powder compacts as well as in additive manufacturing processes. The thermal excursion of the green powder compact determines the extent of sintering and its subsequent evolution of desired properties. Therefore, it is necessary to understand the sintering phenomena for a single green compact. Sintering phenomena of iron ore pellets – magnetite and hematite are investigated in this study using two types of dilatometers. Optical Dilatometer has been used to study in-situ intrinsic sintering kinetics of pellets experimentally at different temperatures, and compared with that of widely used Push Rod Dilatometer. Unlike optical dilatometer, push rod dilatometer uses a load to keep the rod in contact with the compact. Interestingly, it has been found that the intrinsic sintering characteristics changes with the load imposed. These findings can also be extended to other materials manufactured by sintering phenomenon. Understanding on sintering mechanisms of material compacts with and without load will help in evaluating kinetic parameters considering the conditions compact encounter in further applications, and design accordingly.
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| 10. |
- Kumar, T K Sandeep, 1986-, et al.
(författare)
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Investigating the Oxidation Phenomena of Magnetite Pellet
- 2017
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Konferensbidrag (refereegranskat)abstract
- Induration of magnetite pellet is a complex physico-chemical process involving oxidation, sintering and the heat transfer phenomena. Often, these phenomena happen simultaneously and influence each other in the induration furnace. It could be because of the highly exothermic nature of oxidation phenomena that can result in significant temperature gradients inside the pellet and sintering might begin much earlier that it is ideally supposed to. This could results in the formation of pellets with heterogeneous phases and crystallographic properties such as duplex structure, and results in the inferior quality of pellets across the bed. In order to predict the optimum thermal profile to achieve homogenous good quality pellets on consistent basis, it is necessary develop a model based on the kinetics of each of these phenomena. This will help to identify and optimize the responsible process parameters during induration accordingly. Subsequent to the investigation of sintering kinetics of magnetite pellets, the current study focuses on the oxidation phenomena. The reaction mechanisms for oxidation of magnetite pellets is dependent primarily on factors such as temperature and oxygen content in the oxidizing gas, etc. Isothermal oxidation of magnetite at pellet scale has been studied experimentally using Thermogravimetric Analyzer (TGA) by inserting the single pellet directly into the isothermal zone of the furnace. It has been found that the oxidation phenomena in the magnetite pellets is a multi-stage phenomena dominated by distinct mechanisms depending on varying extent of oxidation with respect to temperature and oxygen content.
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