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  • 1.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Geasyy, Abdel Hady El
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Nurni, Viswanathan
    Indian Institute of Technology (IIT).
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Kinetics and mathematical modeling of hydrogen reduction of NiO-WO 3 precursors in fluidized bed reactor2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 9, p. 1383-1391Article in journal (Refereed)
    Abstract [en]

    In the present work, Fluidized bed reduction of NiO-WO 3 precursors was investigated isothermally at temperatures 973-1 273 K. The reaction progress was monitored by analysis of H2O evolved during the reaction process using a gas chromatograph instrument. A theoretical model based on intrinsic chemical reaction rate constants and thermodynamic equilibria was developed to estimate the apparent reaction rate constant for the reduction reaction. In developing the model, the particles are considered to be in a completely mixed condition and gas flow is described as plug flow. The proposed model is also suitable for scale-up calculations. The interfacial chemical reaction model was found to fit the experimental results. The apparent activation energy values of the reduction process at different stages were calculated accordingly. The present investigation proved that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product.

  • 2.
    Ahmed, Hesham
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Persson, Amanda
    Swerea MEFOS AB.
    Sundqvist-Ökvist, Lena
    Swerea MEFOS AB, Luleå tekniska universitet, SSAB Tunnplåt AB, LKAB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Reduction Behaviour of Self-reducing Blends of In-plant Fines in Inert Atmosphere2015In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, no 10, p. 2082-2089Article in journal (Refereed)
    Abstract [en]

    Large amount of dust and sludge recovered during cleaning of iron and steel making process gases are annually put on landfill or intermediate storage. These by-products have high contents of iron (Fe) and carbon (C) that potentially could be utilized in the steel industry. However, due to the presence of impuritycompounds as well as the unsuitable physical properties, these by-products cannot be recycled directly. The main objective of the present study is to investigate the possibilities to recover the valuable components Fe and C in these by-products and thereby decrease the need of landfills at the steel plants as well as reduce the consumption of virgin materials, including fossil coal, and reduce CO2 emissions. A recycling route has been investigated by means of laboratory trials and FactSage thermodynamic modeling. Four different blends of BF and BOF dusts and sludges are prepared in predetermined ratios. Reduction behavior of each blend is studied using TG/DTA/QMS and in-situ high temperature X-ray diffraction. High temperature physical properties like softening, swelling and melting are also investigated by means of heatingmicroscope. The obtained results indicate the feasibility of both minimizing the impurity elements as well as recovering of valuable components.

  • 3.
    Ahmed, Hesham
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Central Metallurgical Research and Development Institute (CMRDI).
    Semberg, Pär
    Luossavaara-Kiirunavara Aktiebolag (LKAB), Luleå.
    Andersson, Charlotte
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effect of added olivine on iron ore agglomerate during induration2018In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, no 3, p. 446-452Article in journal (Refereed)
    Abstract [en]

    Olivine is used extensively in iron-pellet production as an additive in LKAB blast furnace pellets, in order to improve the high temperature properties of the finished product during reduction. As the contribution of olivine into the process depends on the available surface area, the present study was designed to find out the effect of olivine and its fineness on the oxidation-sintering and subsequent dissociation of olivine in iron ore agglomerates. Agglomerates were exposed to different experimental conditions to study the effect of olivine on the behavior of magnetite and hematite at high temperatures. Olivine particles were found to react significantly only above 1 000°C. Porosity of the final product was found to depend largely on olivine fineness. The finer the olivine the lower the porosity of the final product. It is found also that irrespective of the starting iron oxide the ratio between hematite and spinel phase was the same after heating in air. Olivine fineness affects significantly the rate of hematite dissociation, the finer the olivine the higher the dissociation rate. Upon cooling the weight lost due to the dissociation was again regained

  • 4.
    Andersson, Anton
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Ahmed, Hesham
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Rosenkranz, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Characterization and Upgrading of a Low Zinc-Containing and Fine Blast Furnace Sludge: A Multi-Objective Analysis2017In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 57, no 2, p. 262-271Article in journal (Refereed)
  • 5.
    Andersson, Anton
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Gullberg, Amanda
    Swerim AB.
    Kullerstedt, Adeline
    Swerim AB.
    Wedholm, Anita
    SSAB Merox .
    Wikström, Jenny
    LKAB.
    Ahmed, Hesham
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sundqvist Ökvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Recycling of Blast Furnace Sludge to the Blast Furnace via Cold-Bonded Briquettes: Evaluation of Feasibility and Influence on Operation2019In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460Article in journal (Refereed)
    Abstract [en]

    Ore-based steelmaking generates various residues including dusts, sludges, scales and slags. Recycling of these residues within the process or via other applications is essential for sustainable production of steel. In blast furnace (BF) ironmaking, the gas-cleaning equipment generally recovers the particles in the off-gas as dust and sludge. Traditionally, the dry dust is recycled via the sinter or, in the case of pellet-based BF operation, via cold-bonded briquettes and injection. As the BF sludge mainly consists of iron and carbon, this residue is of interest to recycle together with the BF dust. However, depending on how the BF is operated, these two residues are more or less the major outlet of zinc from the furnace. Thus, to limit the recycled load of zinc, both materials cannot be recycled without dezincing the sludge prior to recycling. Dezincing and recycling of the low-zinc fraction of BF sludge via sinter have been reported whereas recycling via cold-bonded briquettes has not been performed. In the present study, cold-bonded briquettes containing the low-zinc fraction of dezinced BF sludge were charged as basket samples to the LKAB Experimental Blast Furnace (EBF). The excavated basket samples from the quenched EBF suggested that additions of up to 20 wt.% of upgraded BF sludge was feasible in terms of reducibility and strength. Based on these results, BF sludge were added to cold-bonded briquettes and charged in industrial-scale trials. The trials indicated that the annual generation of BF sludge, after dezincing, could be recycled to the BF.

  • 6.
    Brämming, Mats
    et al.
    SSAB EMEA, Luleå.
    Millman, Stuart
    Tata Steel Research, D & T, Teesside Technology Centre, Middlesbrough.
    Overbosch, Aart
    Tata Steel Research, D & T, IJmuiden Technology Centre.
    Kapilashrami, Abha
    Tata Steel Research, D & T, IJmuiden Technology Centre.
    Malmberg, Donald
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    BOS vessel vibration measurement for foam level detection2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 1, p. 71-79Article in journal (Refereed)
    Abstract [en]

    In the BOS process liquid slag together with dispersed metal droplets, solid particles and process gases form an expanding foam. Certain process conditions may lead to excessive foam growth, forcing foam out through the vessel mouth, an event commonly known as 'slopping'. Slopping results in loss of valuable metal, equipment damage and lost production time. In the early 1980s a system for foam level and slopping control was installed at SSAB's steel plant in Lulea, a system based on the correlation between BOS vessel vibration in a narrow low frequency band and foam development. The technique, in this case with an accelerometer mounted on the trunnion bearing housing, soon showed its usefulness, for example when adapting existing lance patterns to a change in oxygen lance design from a 3-hole to a 4-hole nozzle. Estimating the actual foam height in the BOS vessel was of great importance in the recently completed RFCS funded research project "IMPHOS" (Improving Phosphorus Refining). Based on the earlier positive experiences, it was decided to further develop the vessel vibration measurement technique. Trials on an industrial size BOS vessel type LD/LBE have been carried out, this time with a tri-axial accelerometer mounted on the vessel trunnion. FFT spectrum analysis has been used in order to find the frequency band with best correlation to the foam level development. The results show that there is a correlation between vessel vibration and foam height that can be used for dynamic foam level and slopping control

  • 7. Chen, Xiang
    et al.
    Vuorinen, Esa
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    In-situ high temperature X-ray studies of austempering transformation in high silicon cast steel2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 8, p. 1220-1224Article in journal (Refereed)
    Abstract [en]

    The in-situ X-ray diffraction observations of the bainitic transformation of high silicon cast steel were performed using the high temperature X-ray diffraction technique. The volume fraction and carbon content of austenite depend on the transformation temperature. The experimental result has shown that the volume fraction of austenite ceases to a constant value which indicate that the transformation is almost finished after holding for about 1000 s. Asymmetry diffraction peaks are obtained for samples at the early stage of transformation due to a heterogeneous distribution of carbon in different regions of austenite and thus exists two types of austenite: low-carbon austenite (gamma(LC)) and the high-carbon austenite (gamma(HC)). The volume fraction of bulk austenite with low carbon decreases greatly at the early stage of transformation and then tends towards zero. The lattice parameter of both low-carbon and high-carbon austenite increases with the holding time due to the carbon partition from the supersaturated ferrite to the austenite. The experimental results supports that the bainite growth is by a diffusionless mechanism when austempering temperature is in the lower bainite transformation temperature range.

  • 8.
    Dwarapudi, Srinivas
    et al.
    Iron & Ferroalloy Research, Research and Development, Tata Steel, Jamshedpur.
    Tathavadkar, Vilas
    Iron & Ferroalloy Research, Research and Development, Tata Steel, Jamshedpur.
    Rao, B. Chenna
    Iron & Ferroalloy Research, Research and Development, Tata Steel, Jamshedpur.
    Kumar, TK Sandeep
    Iron & Ferroalloy Research, Research and Development, Tata Steel, Jamshedpur.
    Ghosh, Tamal K.
    MCJ Research, Research and Development, Tata Steel .
    Denys, Mark
    Research and Development and Scientific Services, Tata Steel.
    Development of cold bonded chromite pellets for ferrochrome production in submerged arc furnace2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 1, p. 9-17Article in journal (Refereed)
    Abstract [en]

    Pelletizing of Indian chromite ores is more challenging due to their high refractory nature. High Cr/Fe ratio and high MgO content in these ores demand high firing temperatures and longer firing cycles but often result in low strength fired pellets. Aim of this study was to develop cold bonded chromite pellets for smelting in submerged arc furnace (SAF) from chromite fines using suitable binder that induce less gangue into the pellets but cures quickly. Different binders were studied through laboratory pelletizing experiments for their suitability for cold bonding the pellets. As result, a composite binder comprising dextrin and bentonite, was found to be suitable and pellets made from the same were tested for their low and high temperature behavior. Electron and optical micro structural studies with image analysis were carried out to find out the type and amount of phases formed in the chromite pellets during high temperature reduction. High temperature reduction studies revealed that pellets were resistant to disintegration up to 1200°C. Pilot scale arc furnace trials were also carried out to compare the performance of cold bonded pellets (CBPs) with sintered chromite pellets and found that for a constant power input, smelting rate was faster for CBPs than sintered pellets. Loss of Cr to slag was reduced in case of cold bonded pellets usage.

  • 9.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simple model for prediction of temperatures in an L-shaped tundish: verification by continuous temperature measurements1998In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 38, no 7, p. 704-713Article in journal (Refereed)
    Abstract [en]

    A simple model concept developed for the SSAB steel plant was tested on data for another plant. That plant had an L-shaped tundish for billet casting. A special tanks in series model was developed for the steel flow in that tundish. The rest of the model could be used without change. It consists of simple equations for heat loss in ladle and tundish, as well as for the effect of thermal stratification and drainage flows in the ladle. The model was verified against existing data from continuous temperature measurements. The results show that the model approach developed for the steel plant of SSAB can also give good predictions with a different plant and tundish design. A simple mixing model could be used even for a complicated tundish configuration

  • 10.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Isaksson, Johan
    Chalmers University of Technology.
    Harvey, Simon
    Chalmers University of Technology.
    Nilsson, Leif
    SSAB EMEA, Luleå.
    Application of pinch analysis in an integrated steel plant in northern Sweden2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 7, p. 1202-1210Article in journal (Refereed)
    Abstract [en]

    The energy system in a modern integrated steel plant is a complicated network of units exchanging energy and matter with each other. System studies using process integration tools are important to avoid sub-optimization. At the steel plant in Luleå such studies have been carried out using a MILP-based mathematical programming tool (reMIND), mainly because of its inherent flexibility for handling combined flows and reactions of both matter and chemical, thermal and mechanical energy. There are, however, areas where the energy system is dominated by creation, transport and exchange of thermal energy, and where pinch analysis can be expected to be a valuable tool. For this reason a pinch targeting study was carried out for the plant site of the integrated steel plant in Luleå. The coke plant and the iron making/steelmaking plant were both studied with three ambition levels of possible improvements. The study confirmed that pinch analysis is a powerful tool for targeting energy savings in areas where thermal energy flows dominate the local energy system, e.g., the gas cleaning area at the coke plant. The study also indicated that a connection between the energy systems in the coke plant and the iron making/steelmaking would be valuable. This is not 100% feasible because of distance, but, a common steam net could add a degree of flexibility.

  • 11.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jonsson, Lage
    Swerea MEFOS AB.
    Jonsson, Pär
    Department of Metallurgy, Royal Institute of Technology, Stockholm.
    Jonsson, Kjell Olof
    SSAB Tunnplåt AB.
    Numerical prediction and experimental verification of thermal stratification during holding in pilot plant and production ladles1999In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, no 7, p. 715-721Article in journal (Refereed)
    Abstract [en]

    A 3-dimensional CFD-model has been developed to simulate the natural convection flow in ladles. Qualified measurements of temperature and velocities in 107 and 7 tonne ladles have been made to verify the model. The downward convection flow at the ladle wall has been studied using radioactive isotopes and the thermal stratification has been studied by means of continuous temperature measurements. The experimental techniques are complex and additional numerical simulations have been carried out to study the effect of the measurement technique on the measurement error. The result indicates that the measurements are of sufficient accuracy for the validation. The measurements are compared to predictions from the numerical model. The main conclusion is that the theoretical CFD model gives a very accurate estimation of the temperature distribution during holding

  • 12.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jonsson, Lage
    Swerea MEFOS AB.
    Jönsson, Pär G.
    Ovako Steel AB.
    Prediction of emptying flows in ladles and verification with data from trace element plant trials1997In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, no 11, p. 1081-1090Article in journal (Refereed)
    Abstract [en]

    A three-dimensional mathematical model of a casting ladle based on fundamental transport equations has been developed. The model may be used for predictions of both a standing ladle and a ladle from which steel is teemed into a tundish. An additional feature of the model is that it can predict concentration profiles of tracer elements which are added to the steel. The predicted concentration profiles during teeming are compared to experimental data from plant trials performed at SSAB and the agreement is found to be good. The model is used as a tool in the development of process control models.

  • 13.
    Grip, Carl-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lampinen, Hans-Olof
    SSAB Tunnplåt AB.
    Lundqvist, Magnus
    Luleå tekniska universitet.
    Videhult, Sebastian
    Kwaerner Turbin AB, Kristinehamn.
    Determination of thermal stratification and emptying flow in ladles by continuous temperature measurement and tracer addition1996In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 36, no Supplement, p. S211-S214Article in journal (Refereed)
    Abstract [en]

    If we want to control and predict the temperature of steel in the tundish we must know the thermal stratification in the ladle before and during casting, as well as the interaction with the steel flow through the nozzle. A group project, with participation of SSAB (Luleå and Oxelo̊sund), Luleå University and MEFOS, has been carried out to study these phenomenon. The stratification in the ladle was measured by thermo-couples penetrating into the melt at different levels. Such measurements were carried out before and during casting. To get information about the drainage flow, studies were made with tracer elements added at different points in the ladle. The response, defined as the tracer concentration in the outlet stream from the ladle, was measured by frequent sampling. Model work by numerical simulation and with tanks in series is discussed briefly

  • 14.
    Hilding, Tobias
    et al.
    Luleå tekniska universitet.
    Gupta, Sushil
    University of New South Wales.
    Sahajwalla, Veena
    University of New South Wales.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wikström, Jan-Olov
    Degradation behaviour of a high CSR coke in an experimental blast furnace: effect of carbon structure and alkali reactions2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 7, p. 1041-1050Article in journal (Refereed)
    Abstract [en]

    A high CSR coke was tested in the LKAB's Experimental Blast Furnace (EBF) at Luleå. The evolution of physical and chemical properties of the centre-line coke samples were analysed by Light Optical Microscopy (LOM), BET N2 absorption and SEM/XRF/XRD. Alkali distribution in the EBF cokes was examined by XRF/SEM and EDS. Thermo Gravimetric Analysis (TGA) was used to measure isothermal and non-isothermal CO2 reactivity of the cokes. The crystalline order of carbon and the concentration of alkalis were found to increase as the coke descended through thermal reserve zone to the cohesive zone of the EBF. The crystallite height (Lc) of EBF coke carbon displayed a linear correlation with the measured EBF temperatures demonstrating the strong effect of temperature on carbon structure of coke in the EBF. Alkali concentration of the coke was increased as it descended into the EBF, and was uniformly distributed throughout the coke matrix. The CO2 reactivity of lower zone cokes was found to increase when compared to the reactivity of the upper zones cokes, and was related to the catalytic effect of increased alkalis concentration. The deterioration of coke quality particularly coke strength and abrasion propensity were related to coke graphitisation, alkalization and reactivity. Coke graphitisation is shown to have a strong influence on the coke degradation behaviour in the EBF.

  • 15.
    Hooey, Lawrence
    et al.
    Oulun Yliopisto, Laboratory of Process Metallurgy, Oulu.
    Riesbeck, Johan
    Swerea MEFOS AB.
    Wikström, Jan-Olov
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Role of ferrous raw materials in the energy efficiency of integrated steelmaking2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 3, p. 596-604Article in journal (Refereed)
    Abstract [en]

    The role of ferrous raw materials and iron ore agglomeration in energy consumption of integrated steelmaking has been evaluated using a system-wide model. Four steelplant cases were defined: typical European steelplant with sinterplant; Nordic steelplant with sinterplant; European steelplant with sinter:pellet ratio of 50%, and Nordic steelplant charging pellets and a small amount of briquettes. Energy consumption in the mining system were estimated from published statistics at 150 MJ/t for lump ore and sinter fines, 650 MJ/t for pellets made from magnetite and 1 050 MJ/t for pellets made from hematite. An integrated steelplant model including all major unit operations was used to calculate overall system energy consumption from iron ore mining to hot rolled coil. Adjustments were made accounting for energy benefit of ground granulated blast furnace slag in cement production, energy required for cement production required for briquetting, and excess BF and BOF gas producing electricity in a 32% efficient power plant. The system-wide net adjusted energy in the first three steeplant cases showed marginal improvement with use of high grade sinter fines and decrease of pellet/sinter ratio to 50% compared to typical European case. Nordic steelplant charging pellets and briquettes had a reduction in system-wide energy of 5% to 8% for charging pellets from hematite or magnetite respectively compared to the typical European steelplant charging sinter and pellets made from hematite ore. Replacement of sinter with pellets was mainly responsible for the improvement with smaller contributions from magnetite ore in pelletizing.

  • 16.
    Hooey, Patrick Lawrence
    et al.
    Swerea MEFOS AB.
    Bodén, Axel
    Swerea MEFOS AB.
    Wang, Chuan
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jansson, Björn
    SSAB.
    Design and application of a spreadsheet-based model of the blast furnace factory2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 7, p. 924-930Article in journal (Refereed)
    Abstract [en]

    The development and application of a 1-dimensional static blast furnace model, "Masmod", written in a common spreadsheet environment, is described. The model includes blast furnace, hot stove, and burden models with recent additions of other operations including CO2 stripping and top gas recycle. Although blast furnace modelling has become increasingly sophisticated, a relatively simple and flexible model is shown to be useful for evaluating burden options, equipment and operational strategies, and process development. Furthermore the Masmod model has been integrated with global steel plant optimization models and Process Integration models for more complex system analysis and optimization.

  • 17.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS AB, Sweden.
    Sundqvist-Öqvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Process Metallurgy Department, Swerea MEFOS AB, Sweden.
    Åström, Elin
    LKAB R&D.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. LKAB R&D.
    Checchia, Paolo
    INFN Sezione di Padova, Padova, Italy.
    Bonomi, Germano
    Universita degli Studi di Brescia, Brescia, Italy.
    Calliari, I.
    Universita degli Studi di Padova, Padua, Italy.
    Calvini, Piero
    Universita degli Studi di Genova, Genoa, Italy.
    Donzella, Antonietta
    Universita degli Studi di Brescia, Department of Mechanical and Industrial Engineering, Brescia, Italy.
    Faraci, Eros
    Centro Sviluppo Materiali S.p.A., Roma, Italy.
    Gonella, Franco
    Istituto Nazionale Di Fisica Nucleare, Frascati, Frascati, Italy.
    Klinger, Joel
    Istituto Nazionale Di Fisica Nucleare, Frascati, Frascati, Italy.
    Pagano, Davide
    Universita degli Studi di Brescia, Brescia, Italy.
    Rigoni, Andrea
    Consorzio Rfx, Padua, Italy.
    Zanuttigh, Pietro
    Universita degli Studi di Padova, Padua, Italy.
    Ronchese, Paolo
    Universita degli Studi di Padova, Padua, Italy.
    Urbani, Michele
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Vanini, Sara
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Zenoni, Aldo
    Universita degli Studi di Brescia, Department of Mechanical and Industrial Engineering, Brescia, Italy.
    Zumerle, Gianni
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Exploring the capability of muon scattering tomography for imaging the components in the blast furnace2018In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

    Knowing the distribution of the materials in the blast furnace (BF) is believed to be of great interest for BF operation and process optimization. In this paper calibration samples (ferrous pellets and coke) and samples from LKAB’s experimental blast furnace (probe samples, excavation samples and core-drilling samples) were measured by the muon scattering tomography detector to explore the capability of using the muon scattering tomography to image the components in the blast furnace. The experimental results show that it is possible to use this technique to discriminate the ferrous pellets from the coke and it is also shown that the measured linear scattering densities (LSD) linearly correlate with the bulk densities of the measured materials. By applying the Stovall’s model a correlation among the LSD values, the bulk densities and the components of the materials in the probe samples and excavation samples was established. The theoretical analysis indicates that it is potential to use the present muon scattering tomography technique to image the components in various zones of the blast furnace.

  • 18.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS.
    Teng, Lidong
    Division of Materials Process Science, KTH-Royal Institute of Technology.
    Wang, Haijuan
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology .
    Sundqvist-Öqvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Seetharaman, Seshadri
    Division of Materials Process Science, KTH-Royal Institute of Technology .
    Carbothermic Reduction of Synthetic Chromite with/without the Addition of Iron Powder2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 12, p. 2147-2155Article in journal (Refereed)
    Abstract [en]

    Carbothermic reduction of chromite is an important industrial process for extracting chromium from the chromite. To have a better understanding of the effect of iron on the carbothermic reduction of chromite, the reduction of synthetic chromite (FeCr2O4) by graphite with/without the addition of iron powder was investigated in this paper by Thermogravimetric Analysis (TGA) in argon atmosphere. The fractional reduced samples were examined by SEM/EDS and XRD analysis, and the reduction process was thermodynamically and kinetically evaluated. The experimental results show that the iron powder addition enhances the reduction of FeCr2O4 and this effect increases when increased amounts of iron powder are added. This phenomenon is attributed to the in situ dissolution of chromium into the iron and mixed carbide (Cr,Fe)7C3, which can decrease the activity of the nascent chromium formed by the reduction of the FeCr2O4. The experimental results indicate that the reduction of FeCr2O4 with up to 80 wt.% iron powder addition is likely to be a single-step process and the kinetic analysis suggests that the reduction reaction is likely to be either (a) chemical reaction at the surface of FeCr2O4 or (b) diffusional dissolution of the product (FeCr2) into the iron/alloy particles or the mixed control of (a) and (b). 

  • 19. Larsson, Mikael
    et al.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Reduction of the specific energy use in an integrated steel plant: the effect of an optimisation model2003In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 43, no 10, p. 1664-1673Article in journal (Refereed)
    Abstract [en]

    Analysing the potential for improving the specific energy use in a steel mill can be difficult due to the interactions between the different subsystems. Changes in one unit can lead to several changes throughout the system. A process integration model taking into account the different interactions within the system is presented. The model is based on an optimising routine, making it a total analysis method for the steel plant system including the surroundings. The model is used to analyse the different possibilities for energy savings and practice changes within the system. The effect of optimising the total system versus separate optimisation of the different sub-processes is illustrated. The method development can serve as a benchmark for different steelmaking operations and constitute a basis for the continuous work involved in energy, material or economic analyses for the steel production system.

  • 20. Leimalm, Ulrika
    et al.
    Forsmo, Seija
    LKAB Research and Development.
    Dahlstedt, Anna
    LKAB Research and Development.
    Sundqvist-Ökvist, Lena
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Blast furnace pellet textures during reduction and correlation to strength2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 10, p. 1396-1405Article in journal (Refereed)
    Abstract [en]

    The blast furnace is the most common means of producing hot metal. As the amounts of reduction agents increases, which influence in-furnace conditions such as ascending gas properties, temperature profiles and the ore-to-coke ratio, new demands are put on the iron-bearing material in terms of both reducibility and mechanical strength. To investigate the possibilities to use the Pellet Multi Press (PMP) equipment for compression strength measurements of reduced pellets and to gain a deeper understanding of the correlation between pellet texture and strength, an initial study of pellets taken from the LKAB Experimental Blast Furnace (EBF) was conducted. Furthermore, the pellet pieces generated after compression tests were characterized using light optical microscopy. In order to correlate the texture of pellet pieces to the pellet texture prior to breakage, a characterization of the chronological pellet texture development during reduction in the EBF was performed. The original pellet texture remained in the beginning of reduction and differences receded through the EBF shaft as wustite and Feme, was formed. Occurrence of Feme, in the pellet texture increased the compression strength, while less reduced and less sintered textures showed the reverse effect. So far, the results from compression strength tests indicate that disintegration of pellets takes place at a reaction front, at the transition between different texture types of iron oxide or at the location of a visible surface crack.

  • 21. Leimalm, Ulrika
    et al.
    Lundgren, Maria
    Ökvist, Lena Sundqvist
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Off-gas dust in an experimental blast furnace: Part 1: Characterization of flue dust, sludge and shaft fines2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 11, p. 1560-1569Article in journal (Refereed)
    Abstract [en]

    In blast furnace (BF) ironmaking, efforts are made to decrease coke consumption, which can be done by increasing the pulverized coal injection rate (PCR). This will cause changes in in-furnace reduction conditions, burden distribution, demands on raw material strength, etc. In order to maintain stable operation, but also to obtain low amounts of material losses through the off-gas, it is important to understand fines generation and behaviour in the BF. Off-gas dust and shaft fines generated in the LKAB Experimental Blast Furnace (EBF) were sampled during operation with olivine pellets and mixtures of acid pellets and sinter as iron-bearing materials. Characterization using XRD, SEM and LOM was focused on fines from iron-bearing materials, coke and slag formers. The results showed that flue dust, mainly <0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions >0.075 mm and consisted mainly of coke particles from the shaft. Fe-containing particles, as Fe2O3 from the top of the shaft, formed the major part of flue dust fractions <0.063 mm. Particles from slag formers such as quartzite and limestone were observed in flue dust when slag formers were utilized in the feed. Sludge consisted mainly of chemically formed spherical particles <1 μm precipitated from the ascending gas as the temperature decreased.

  • 22. Leimalm, Ulrika
    et al.
    Ökvist, Lena Sundqvist
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of different PCI practice on the texture obtained during reduction of iron oxide pellets2008In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, no 12, p. 1686-1695Article in journal (Refereed)
    Abstract [en]

    In modern blast furnace ironmaking, producers continuously strive to reduce coke consumption by replacing coke with e.g., an increased amount of injected pulverized coal. A change in pulverized coal injection rate (PCR) and injection coal type will influence the in-furnace conditions and thus the reduction of iron oxides. In the present study, the reduction behaviour of olivine pellets and textures formed were investigated in the LKAB Experimental Blast Furnace (EBF) and in laboratory scale. In the EBF, effects of injection of an low-volatile (LV) and an high-volatile (HV) coal type at different PCR while two types of oxygen supply methods were employed were investigated. The choice of injection coal type was conclusive for the Femet texture formed during reduction, extent of Femet carburization and K distribution in the pellets. The amount of volatile matters in the coal type had a greater effect on the reduction properties than the PCR and oxygen supply method. Laboratory experiments simulating PCR, based on measurements in the EBF, showed that the initial reduction conditions, in terms of temperature level and reduction gas composition, determined the pellet texture up to a reduction degree of at least 60%. The tests carried out in the EBF showed that the pellets were well suited for blast furnace reduction under all the investigated process conditions. The laboratory tests supported this conclusion.

  • 23. Lundgren, Maria
    et al.
    Leimalm, Ulrika
    Hyllander, Gunilla
    LKAB.
    Ökvist, Lena Sundqvist
    Swerea MEFOS AB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Off-gas dust in an experimental blast furnace: Part 2: Relation to furnace conditions2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 11, p. 1570-1580Article in journal (Refereed)
    Abstract [en]

    In the blast furnace process, material losses are caused by particles that are blown out of the furnace by the off-gas. In order to reduce these losses, it is important to understand the correlations between furnace conditions and off-gas dust formation. Off-gas dust, as flue dust and sludge, were collected during shaft probe sampling in LKAB Experimental Blast Furnace (EBF). Process data was used to evaluate the relationship between off-gas dust amounts and furnace conditions. The graphitization degree (Lc value) of shaft coke and coke in flue dust was determined using XRD measurements. Solution loss in the shaft had a negligible effect on coke degradation and the coke particles which ended up in the flue dust were mainly derived from abrasion at low temperatures. The amount of alkali and SiO2 in sludge increased with higher PCR and flame temperature, which confirmed that submicron spherical particles in sludge originated from the high temperature area around the raceway. Theoretical critical particle diameters of materials, which could be blown out with the off-gas, were estimated. Flow conditions in the top of the shaft as well as and the properties of fine particles in terms of size and density are important when outflow of mechanical dust, such as flue dust, is concerned. Low off-gas temperatures, and thus lower off-gas velocities, are favourable for low flue dust amounts expelled from the blast furnace.

  • 24.
    Ma, Tang
    Luleå tekniska universitet.
    Injection of flux into the blast furnace via tuyeres for optimising slag formation1999In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, no 7, p. 697-704Article in journal (Refereed)
    Abstract [en]

    Based on discussion of the slag formation problems occurred during a commercial scale blast furnace test of 100% high Fe-content self-fluxed pellets, a proposal of replacing the charge of flux from the top by injection via tuyeres has been presented. It will optimise the slag formation process and provide a great potential of further increase productivity with smooth operation due to: 1) decrease bosh slag volume significantly; 2) obtain even and proper basicities of primary slag, bosh slag, tuyere slag and final slag formed along the height the blast furnace

  • 25.
    Mousa, E.A.
    et al.
    Process Integration Department, Swerea MEFOS.
    Ahmed, Hesham
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Wang, Chuan
    Process Integration Department, Swerea MEFOS.
    Novel approach towards biomass lignin utilization in ironmaking blast furnace2017In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 57, no 10, p. 1788-1796Article in journal (Refereed)
    Abstract [en]

    Growing concerns over fossil CO2 emissions has created a considerable interest in an efficient utilization of renewable biomass in steel industry. Biomass lignin can be used as binder and reducing agent in the blast furnace briquettes. The traditional briquettes consist of various iron oxide-containing residues and cement is used as binder to give the proper mechanical strength. In the present study, cement (C) has been partially and totally substituted with lignin (L) to produce briquettes containing 0-12 wt.% lignin (L/C: 0, 10, 25, 50 and 100%). The mechanical strength has been evaluated based on drop test and tumbler index measurement. The partial replacement of cement with lignin up to 25% (3.0 wt.% lignin in briquettes) was exhibited adequate briquettes strength for blast furnace application. At higher substitution rate (L/C: 50 and 100%), the briquettes strength was sharply decreased. The briquettes with proper mechanical strength (L/C: 0, 10 and 25%) were subjected to self-reduction under inert atmosphere using thermogravimetric technique (TGA). The reduction rate of briquettes increased when increasing the cement substitution with lignin. The reduction took place in two main steps at 500-800°C and 800-940°C. Combined effect of gas diffusion and interfacial reaction were the rate determining step at the first stage while carbon gasification was controlling the second step of reduction. Interrupted reduction tests have been conducted to evaluate the compression strength after reduction. For all briquettes, the increased reduction temperature and lignin content deteriorated the briquette's mechanical strength due to the effect of dehydration and lignin gasification.

  • 26.
    Nordgren, Samuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    LKAB, Technology and Business Development.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sandberg, Johan
    LKAB, Technology and Business Development.
    Effective Use of Available Heat for Maintaining a High Green Pellet Temperature2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 12, p. 2072-2079Article in journal (Refereed)
    Abstract [en]

    In iron ore pellet production, an increased green pellet temperature has a positive influence on the straight grate induration furnace. Previous studies show that this can lead to both higher production capacity of the induration furnace and also reduced specific oil consumption. The aim of this study is to apply the process integration concept to analyze how to maintain a high green pellet temperature by using the available heat more effectively. The heat is today used for the indoor climate and is delivered by electricity boilers and a waste heat recovery boiler that is installed next to the induration furnace, using hot gases from the furnace to heat water. This work will however assume that one can use the heat from the waste heat recovery boiler to preheat the material stream. By optimizing the cold section of the pelletizing plant, using process integration and the mathematical modeling approach in combination with the newly developed Optimal Solution Space Method, the results show that it is possible to increase the green pellet temperature and also reduce the energy cost by using the available energy in a more efficient way. It is also showing that by retrofitting the system so that the waste heat from the waste heat recovery boiler is used to preheat the material stream, this also leads to reduced energy cost and also increased production of iron ore pellet since the temperature of green pellet will be higher.

  • 27. Nurni, Viswanathan
    et al.
    ji, F.Z.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Sichen, Du U.
    Royal Institute of Technology, Division of Materials Process Science, Stockholm.
    Seetharaman, Seshadri
    Royal Institute of Technology, Division of Materials Process Science, Stockholm.
    Viscosity measurements on some fayalite slags2001In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 41, no 7, p. 722-727Article in journal (Refereed)
    Abstract [en]

    In the present study, viscosity measurements on Fe-O-Si slags have been carried out using rotating cylinder method. The slag samples for viscosity measurement were prepared by pre-melting appropriate stoichiometric amounts of Fe, Fe2O3 and SiO2 in an iron crucible under argon atmosphere, which ensured that Fe ions in the slag were predominantly in the valence state of +2. The viscosities of the pre-melted slag samples were measured in iron as well as nickel crucibles under argon atmosphere at different temperatures. The measured viscosity values obtained in the two kinds of crucibles were found to be in good agreement, indicating thereby that nickel crucibles can be successfully used for viscosity measurements. In order to investigate the effect of oxidation of Fe2+ to Fe3+, the binary FenO-SiO2 slag was kept in a nickel crucible under oxidising conditions using a CO/CO2 atmosphere and viscosity measurements were carr ied out dynamically as a function of time at 1 623 and 1 673 K. With time, Fe3+ concentration in the slag increased and hence the viscosity changed progressively. The rate controlling step for the oxidation reaction was considered to be the mass transfer of CO2 in the gas stream to the slag-gas interface. A simple kinetic analysis was used to predict the concentration of Fe3+ in the slag with time. The measured viscosity with time indicated that the viscosity remains almost the same during initial period of oxidation. The viscosity raises sharply when the Fe3+ concentration in the slag, calculated as F2O3 reached around 7 mass%.

  • 28. Nurni, Viswanathan
    et al.
    Srinivasan, Mandayam Nayachavadi
    Department of Mechanical Engineering, Indian Institute of Science, Bangalore.
    Lahiri, Ashok Kumar
    Department of Metallurgy, Indian Institute of Science, Bangalore.
    Process simulation of cupola1998In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 38, no 10, p. 1062-1068Article in journal (Refereed)
    Abstract [en]

    Cupola is a counter current shaft reactor for production of cast iron. The solid charge consisting of coke, pig iron, steel scrap and flux is fed from the top of the reactor and blast is blown radially through the tuyeres. One-dimensional (1 - D) models, wherein the governing equations are solved along the axial direction, have been reported in the literature. However, because of radial entry of blast through the tuyeres, incorporation of boundary conditions at the tuyere level poses a major difficulty in 1 - D models. In this paper, a pseudo 2 - D model for cupola has been proposed in which, the governing equations are employed in 2 - D at the tuyere level and 1 - D in the remaining portion. The solution of 2 - D equations at the tuyere level generates the appropriate boundary conditions for the remaining 1 - D portion above the tuyeres. In order to evaluate the performance of the pseudo 2 - D model, a 2 - D model was also developed. Further, the two models have been validated using reported experimental data. The study shows that the overall temperature and composition distributions obtained from the pseudo 2 - D model are quite comparable with that obtained from the 2 - D model. Also, the pseudo 2 - D model was found to be computationally faster compared to the 2 - D model. Hence, for practical design and operation exercise, pseudo 2 - D model can be effectively used

  • 29.
    Pan, Yuhua
    et al.
    Luleå tekniska universitet.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Numerical analysis on the similarity between steel ladles and hot-water models regarding natural convection phenomena2002In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 42, no 1, p. 53-62Article in journal (Refereed)
    Abstract [en]

    The similarity between steel ladles and hot-water models regarding natural convection phenomena has been systematically analysed through examination of the numerical solutions of turbulent Navier-Stokes partial differential equations governing the phenomena in question. The numerical solutions have been obtained by using a computational fluid dynamics (CFD) simulation method. Key similarity criteria for nonisothermal physical modelling of steel ladles with hot-water models have been derived. Accordingly, appropriate conditions fulfilling the above criteria, such as model size, water temperature, time scale factor and the scale factor of boundary heat loss fluxes, have been proposed and discussed. As a result, water models with geometry scales between 1/5 and 1/3 and using hot-water of temperature higher than 45 deg C are appropriate for simulating natural convection phenomena in steel ladles.

  • 30.
    Pan, Yuhua
    et al.
    Luleå tekniska universitet.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Physical and mathematical modelling of thermal stratification phenomena in steel ladles2002In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 42, no 6, p. 614-623Article in journal (Refereed)
    Abstract [en]

    A 1/4-scale hot-water model of industrial 107-tonne steel ladles was established in the laboratory. With this physical model, thermal stratification phenomena due to natural convection in steel ladles during the holding period before casting were investigated. By controlling the cooling intensity of the water model to correspond to the heat loss rate of steel ladles, which is governed by dimensionless numbers Fr and beta Delta T, temperature distributions in the water model can simulate those in the steel ladles. Consequently, the temperature profile in the hot-water bath in the model can be used to deduce the thermal stratification phenomena in liquid steel bath in the ladles. In addition, mathematical simulations on fluid flow and heat transfer both in the water model and in the prototype steel ladle were performed using a computational fluid dynamics (CFD) numerical method. The CFD model was validated against temperatures measured in the water model. Comparisons between mathematically simulated temperature profiles in the prototype steel ladle and those physically simulated by scaling-up the measured temperature profiles in the water model showed a good agreement. Therefore, it can be concluded that, as long as accurate heat loss information is known, it is feasible to use a 1/4-scale water model to non-isothermally simulate fluid flow and heat transfer in steel ladles during the holding period before casting.

  • 31.
    Pan, Yuhua
    et al.
    Luleå tekniska universitet.
    Guo, Diancai
    Department of Metallurgy, Anshan Institute of Iron and Steel Technology.
    Ma, Jianjun
    Department of Metallurgy, Anshan Institute of Iron and Steel Technology.
    Wang, Wenzhong
    The Third Steelworks of Anshan Iron and Steel Complex.
    Tang, Fuping
    The Third Steelworks of Anshan Iron and Steel Complex.
    Li, Chao
    The Third Steelworks of Anshan Iron and Steel Complex.
    Mixing time and fluid flow pattern of composition adjustment by sealed argon bubbling with ladles of large height/diameter ratio1994In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 34, no 10, p. 794-801Article in journal (Refereed)
    Abstract [en]

    Based on a prototype installation, the mixing time and the fluid flow pattern of CAS (Composition Adjustment by Sealed argon bubbling) were studied by a water model analog simulation. The decisive criterion for this simulation was formulated as a dimensionless number Qμ/(D2σ) which can satisfactorily keep the physical similarity between model and prototype. The critical bottom blowing gas flowrate due to the existence of a slag baffle was defined and used to evaluate the reliability of the simulation. It was found from the investigation that the fluid flow behaviour of CAS is significantly different from that of the conventional ladle bottom-blow stirring. Comments on the design and operation of CAS were proposed. The optimization of CAS was recommended to be conducting the operation with both eccentric bottom blowing and eccentric slag baffle positioning by using ladles of large height/diameter ratio

  • 32.
    Ryman, Christer
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Mikael
    Reduction of CO2 emissions from integrated steelmaking by optimised scrap strategies: application of process integration models on the BF-BOF system2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 12, p. 1752-1758Article in journal (Refereed)
    Abstract [en]

    In integrated steelmaking there are a number of means to reduce CO2 emissions. One approach is to increase the metallic Fe input to the production system. A common belief is that scrap works as a CO2 diluent when introduced in iron ore based steelmaking. It is not necessarily so. Scrap is a key supplementary charge material in oxygen steelmaking converters, but scrap can also be utilised in ironmaking where it will decrease the use of reducing agents and with that also the specific CO2 emissions. By the use of a process integration model which basically includes the primary processes of cokemaking, sintering, ironmaking and oxygen steelmaking the overall influence of scrap input on CO2 emissions is demonstrated and commented. The influence of hot metal silicon content is elucidated by calculations with different material and process constraints. The results show that at moderate scrap rates, the reduction of CO2 emissions is favoured by increased scrap additions to the oxygen converter. When the scrap additions to the converter balances the actual heat capacity of the bath, other means to achieve an increased scrap melting capacity can be taken into account. This include combinations of scrap addition to the blast furnace, increased silicon content in tapped hot metal, and/or addition of Ferro-silicon combined with further scrap additions to the oxygen converter. Different strategies for CO2 emission reduction have to be suggested depending on if the objective is to minimise the site (direct) emissions or the global (indirectdirect) emissions.

  • 33.
    Semberg, Pär
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Andersson, Charlotte
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interaction between iron oxides and olivine in magnetite pellets during reduction to Fe-met at temperatures of 1 000-1 300 degrees C2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 8, p. 1341-1349Article in journal (Refereed)
    Abstract [en]

    The addition of MgO to iron ore pellets is known to beneficially influences many high temperature reduction properties such as reducibility and swelling. When the pellet is metallized, MgO dissolved in the wustite concentrates in the unmetallized part, which is why MgO-levels much higher than the average concentration could be expected locally. In this work the impact of the elevated MgO-content on the reduction at 1 000-1 300 degrees C was studied by SEM-EDS. The MgO content in the pellet was also varied by additions of a), highly reactive olivine b) unreactive olivine c) combined addition of reactive olivine and fine quartzite and d) combined addition of unreactive olivine and fine quartzite. Two cases of metallization were observed 1) a gradual reduction front with only moderate magnesium levels and 2) a sharp reduction front with strongly elevated magnesium levels before the metal front. The samples with added quartzite reduced a little better at 1 100 degrees C, compared to those with only olivine, but apart from that, reduction was not affected much by the additives in the range 1 000-1 200 degrees C. The greatest difference in reduction degree appeared at 1 300 degrees C where a metal skin formed in most samples, hindering further reduction. At this temperature, the sample with addition of only reactive olivine had superior reducibility due to a porous morphology of the iron being mantained throughout the experiment.

  • 34.
    Semberg, Pär
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interaction between iron oxides and olivine in magnetite pellets during reduction to wustite at temperatures of 1 000-1 300 degrees C2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 3, p. 391-398Article in journal (Refereed)
    Abstract [en]

    In this study the magnesium diffusion behaviour was studied in pellets with fine and course olivine, with and without additional fine quartzite (<20 mu m) after isothermal reduction at 1 000-1 300 degrees C. It was found that, by using a fine olivine (<38 mu m) the whole magnesium content of the olivine was dissolved evenly in the wustite and in the slag, already at 1 000 degrees C, in agreement with the equilibrium tie-lines of the FeO-MgO-SiO2 phase diagram. This lead the liquid slag to precipitate into fayalitic olivine and the Al, Na, K, Ca, P-content to enrich in remaining inclusions in the olivine. This crystallization did not occur in the sample with only bentonite addition, or in the sample with unreactive olivine at these temperatures. However, with further addition of fine quartzite, the slag of the sample with coarse olivine also crystallized. In the samples reduced at 1 000-1 100 degrees C, magnesium gradients could be detected in the slag phase around coarse olivine particles until entering the interaction volume of an interfering particle at around similar to 600 mu m, or occasionally at distances of more than 1 mm. For the coarse olivine the main rise in magnesium occurs at 1 200 degrees C when the olivine particle cores begin to dissolve. The dissolution of all magnesium of the 2.5% olivine addition during oxidation lead to 6.5% Mg in the crystallized slag phase. The increase in melting point resulting from this compared to fayalite with no magnesium is similar to 50 degrees C, according to thermodynamic calculations. .

  • 35.
    Semberg, Pär
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Rutqvist, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Andersson, Charlotte
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interactions between iron oxides and the additives quartzite, calcite and olivine in magnetite based pellets2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 2, p. 173-180Article in journal (Refereed)
    Abstract [en]

    Magnetite-based pellets with large amounts of the additives olivine, calcite and quartzite were isothermally reduced in a tubular furnace to study and describe the reaction behaviour of the additive minerals in the pellets. The reduction was thermodynamically set to yield wustite at three different temperatures: 900, 1000 and 1150 degrees C. The mineralogical phases that had formed before and after reduction were studied by Scanning electron microscope and X-ray diffraction. The pellets with the different additives were different already before reduction due to different reaction behaviour during induration: The results showed that it was possible to identify the main reactions during reduction for pellets with all three additives. All but the very small quartzite particles remained unreactive in reducing atmosphere until they began to form a fayalitic melt at 1000 degrees C. The calcium ferrites of the pellets with calcite reacted to form a porous calciowustite already at 900 degrees C. In the pellets with olivine, the magnesium, which had constrained into magnesioferrite pockets after induration, redistributed into the entire iron oxide structure at 900 degrees C and also reacted with silica at 1000 degrees C. The olivine core which had not reacted during induration did not appear to react in reducing conditions at temperatures of 1150 degrees C and below. These reaction mechanisms have indicated a potential to reduce the required amounts of additives in the pellets.

  • 36.
    Singh, Maneesh
    et al.
    Luleå tekniska universitet.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of processing parameters on the swelling behaviour of cement-bonded briquettes2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 1, p. 59-68Article in journal (Refereed)
    Abstract [en]

    The use of cement-bonded agglomerates of iron-rich by-products generated in iron and steel plants as burden material for blast furnaces is becoming quite common. It has been observed that under certain conditions the briquettes containing pellet-fines show a tendency to swell catastrophically when reduced at 900-1000DGC using carbon monoxide as a reducing agent. This swelling is dependent upon a number of processing parameters, such as: composition of briquettes, particle size of raw material, amount of cement, composition of cement, and coke content. It is not dependent upon the size of agglomerate or hydration period. From the optical micrographs, it is apparent that the swelling may be attributed to the formation of small spheroidal iron particles that move apart, thereby causing swelling. This paper describes the effect of various processing parameters that cause the abnormal swelling in cement-bonded briquettes made of pellet-fines.

  • 37.
    Singh, Maneesh
    et al.
    Luleå tekniska universitet.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of reduction conditions on the swelling behaviour of cement-bonded briquettes2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 2, p. 294-303Article in journal (Refereed)
    Abstract [en]

    Cement-bonded agglomerates of by-products generated in iron and steel plants are commonly used as burden material for blast furnaces. It has been observed that under certain conditions the briquettes containing pellet-fines show a tendency to swell catastrophically when reduced at 900-1 000 deg C using carbon monoxide as reducing agent. This swelling is dependent upon a number of factors like: reducing temperature, reducing conditions and composition of reducing gas. The optical micrographs do not show the formation of iron whiskers as the cause of swelling; instead, the reduced iron particles seem to move apart, thereby causing swelling. This paper describes the effect of various parameters that cause the abnormal swelling of briquettes.

  • 38.
    Singh, Maneesh
    et al.
    Luleå tekniska universitet.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Swelling behaviour of cement-bonded briquettes-proposed model2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 3, p. 482-491Article in journal (Refereed)
    Abstract [en]

    The cement-bonded agglomeration process is an alternative to the traditional balling-sintering process for recycling iron-rich by-products generated in iron and steel plants back to the blast furnaces. It has been observed that, under certain conditions, the briquettes containing pellet-fines show a tendency to swell catastrophically when reduced. This swelling is dependent upon a number of factors like: reducing temperature, composition of briquettes, particle size of raw material, amount of cement and composition of reducing gas. The SEM and optical micrographs do not show the formation of iron whiskers as the cause of swelling; instead, the swelling is due to the movement of reduced iron particles away from each other. It has been proposed that the swelling takes place in three steps: (a) fragmentation of weak pellet-fines particles during reduction to wustite; (b) formation of liquid slag due to reaction between CaO, MgO, FeO, SiO2 and Al2O3; (c) generation of high gas pressure due to formation and subsequent oxidation of metastable iron carbide.

  • 39.
    Somani, Mahesh C.
    et al.
    Uleåborg universitet.
    Karjalainen, Pentti
    Uleåborg universitet.
    Eriksson, Magnus
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Dimensional changes and microstructural evolution in a B-bearing steel in the simulated forming and quenching process2001In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 41, no 4, p. 361-367Article in journal (Refereed)
    Abstract [en]

    To improve the modelling of the behaviour of steel profiles in the forming and quenching process, the influences of high-temperature plastic deformation and applied stress on the martensitic transformation were investigated in a B-bearing steel by dilatometric measurements and compression tests. The plastic deformation of austenite was found to enhance ferrite formation so significantly that the dilatation due to the low-temperature transformation decreases even at a cooling rate of 280°C/s. The presence of ferrite in the microstructure results in markedly lower hardness and flow stress than the completely martensitic microstructure. Possibilities to avoid ferrite formation have been discussed. Stress applied during the martensitic transformation increases diametric dilatation by as much as 200 % under axial compression, which seems to result from the preferred orientation of the martensite formed. However, subsequent to a hightemperature plastic deformation, the influence of applied stress remains much smaller.

  • 40.
    Su, Fenwei
    et al.
    SSAB Tunnplåt AB.
    Lampinen, Hans-Olof
    SSAB Tunnplåt AB.
    Robinson, Ryan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Recycling of sludge and dust to the BOF converter cold bonded pelletizing2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 4, p. 770-776Article in journal (Refereed)
    Abstract [en]

    With the aim to increase the recycling of fine sludge and dust disposed normally in landfill, cold bonded pelletizing of the sludge and dust using cement as binder was investigated in laboratory scale as well as in the pilot scale pelletizing plant. The influence of BF flue dust, BOF fine sludge and oily mill scale sludge on the cold strength, capacity and reduction degree of cold bond pellets was studied experimentally on the basis of a statistical procedure. With a coarser representative particle size, oily mill scale sludge has the greatest effect on the cold strength. BF flue dust has a negative effect for increasing both the cold strength and capacity for levels of over 25% of the mixture. The BOF fine sludge has the positive effect on cold strength, while its interaction with BF flue dust has the negative effect on reduction degree. The results of pelletizing tests in pilot scale show that the maximum cold strength (TTH 94%) and capacity (13-15 t/h) of products is obtained at the conditions given by the optimal mixture design and cure time. The industrial tests on charging cold bonded pellets as burden material in the BOF converter were described. The charging weight of cold bonded pellets varied from 0.5 to 2.5 tons. The results of industrial tests indicated that the converter process was not subject to any adverse disturbances due to the addition of 2.5 tons of cold bonded pellets.

  • 41.
    Zuo, Guangqing
    Luleå tekniska universitet.
    Softening and melting characteristics of self-fluxed pellets with and without the addition of BOF-slag to the pellet bed2000In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, no 12, p. 1195-1202Article in journal (Refereed)
    Abstract [en]

    When using 100% self-fluxed pellets in the blast furnace burden, top charged fluxes, especially the BOF-slag, may cause irregularities in operation. The major reason has been theoretically attributed to the problematic slag formation in the furnace. As the melting of pellets is the first step of the slag formation process, the softening and melting properties of LKAB's self-fluxed pellets with and without addition of fluxes are studied experimentally. The results show that the softening and melting properties of the two types of LKAB's self-fluxed pellets are quite suitable for blast furnace operation. Contrarily, the melting-down characteristics of BOF-slag are variable and harmful to the slag formation under a reducing atmosphere. Adding 5% BOF-slag to the self-fluxed pellets can considerably worsen the softening and melting properties of pellets. It can either increase the softening and melting temperature interval substantially or cause the precipitation of solid phases, mainly di-calcium silicates, in the slag. It is quite likely that the resulting slag will therefore become very viscous, even entirely blocking the melting down of the pellets up to a temperature 1 520°C.

  • 42.
    Ökvist, Lena Sundqvist
    et al.
    Luleå tekniska universitet.
    Cang, Danqiang
    SSAB Tunnplåt AB.
    Zong, Yanbing
    SSAB Tunnplåt AB.
    Bai, Hao
    University of Science and Technology, Beijing.
    The effect of BOF slag and BF flue dust on coal combustion efficiency2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 9, p. 1501-1510Article in journal (Refereed)
    Abstract [en]

    Injection into a BF of BOF slag to improve the slag formation and of BF flue dust to improve the recycling of in-plant fines has previously been tested. The effects on the PC combustion efficiency at different conditions, when these materials are co-injected with coal, have so far not been tested. Combustion efficiencies at varied temperature, O2 enrichment, amount of PC, amount of added BOF slag or BF flue dust and particle size of the added material are measured in a fixed bed and a blowpipe model. The established facts that an increased temperature and O2 enrichment or a decreased amount of coal increase the combustion efficiency are valid also when BOF slag or BF flue dust are added to the coal. By adjusting the combustion conditions, a decreased combustion efficiency can be counteracted, when a second material is co-injected with coal. The effect of BOF slag addition on coal combustion efficiency measured in the blowpipe model is in-significant, if a fine fraction is used. The combustion efficiency is higher in the fixed bed compared with that in the blowpipe model. The addition of BF flue dust increases the combustion efficiency in the fixed bed

1 - 42 of 42
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