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  • 1. Adolfsson, Daniel
    et al.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Robinson, Ryan
    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.
    Cementitious phases in ladle slag2011In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, no 4, p. 398-403Article in journal (Refereed)
    Abstract [en]

    Ladle slag is an internal by-product generated within the steelmaking industry during the refining of steel. The realisation of beneficial inherent properties of ladle slag as a binder supplement or substitute material is believed to be advantageous with respect to both economy and environment for steelmakers. For this reason, the current study has focused on highlighting the properties of ladle slag that are pertinent to the formation of calcium aluminate hydrates. Three fractions of ladle slag, two of which were based on different slag formers, have been characterised using XRF, XRD and calorimetric analysis. Commonly known hydraulic minerals such as mayenite, tricalcium aluminate and dicalcium silicate were detected during analysis. An important aspect in the utilisation of ladle slag is the slag handling methodology. Therefore, this study also highlights and discusses the need to reconsider slag handling procedures concerning unnecessary exposure to weathering and the possible need for further processing of the slag in order to better employ the inherent hydraulic properties of this material.

  • 2.
    Adolfsson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Robinson, Ryan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of mineralogy on the hydraulic properties of ladle slag2011In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 41, no 8, p. 865-871Article in journal (Refereed)
    Abstract [en]

    The present study is aimed at investigating the hydraulic characteristics of ladle furnace slag (LFS), under the pretence of using LFS as a cement substitute in certain applications. Furthermore, LFS has been considered as a possible activator in a blend containing 50% LFS, and 50% ground granulated blast furnace slag (GGBFS). Phases detected in LFS were quantified using Rietveld analysis. Calorimetric studies were performed at 20, 25 and 30 °C in order to calculate the apparent activation energy of hydration and thereby to suggest a kinetic model for the tested compositions within this temperature interval. In addition, compressive strength tests were performed on mortar prisms made with LFS, and LFS/GGBFS which had hydrated for 2, 7 and 28 days. Both compositions reached acceptable early strengths, (e.g. LFS, 33.1 MPa, and LFS/GGBFS, 17.9 MPa, after 2 days), but after 28 days hydration the blend was superior to neat LFS. Related apparent activation energies were determined using an Avrami–Erofeev model and gave Ea = 58 kJ/mol for neat LFS and Ea = 63 kJ/mol for the blend. The results imply that LFS or a LFS/GGBFS blend can be favourably used as supplement in binder applications such as binder in by-product metallurgical briquettes, which are used as recycle to the blast furnace or basic oxygen furnace depending on the specific briquette composition.

  • 3.
    Albertsson, Galina Jelkina
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Teng, Lidong
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Effect of the Heat Treatment on the Chromium Partition in Cr-Containing Industrial and Synthetic Slags2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 10, p. 1418-1431Article in journal (Refereed)
    Abstract [en]

    In the present work, the effects of the slag composition and heat-treatment conditions on the phase relationships in a number of Cr-containing industrial and synthetic slags were investigated with a view to control the precipitation of Cr-spinel in the slag phase. Gas/slag equilibrium technique was used for the chromium partition and the phase relationship study. The phase relationships in synthetic slags and industrial EAF slags supplied by Swedish steelmaking plants have been investigated experimentally in the temperature range of 1473–1873 K. The slags were re-melted, slow-cooled to, and soaked at targeted temperatures in controlled atmosphere. Two different heat-treatment sequences were used in the present experiments. The oxygen partial pressure () was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using X-ray diffractometry (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer (WDS). Chromium partition was found to depend on the heat-treatment temperature

  • 4.
    Albertsson, Galina Jelkina
    et al.
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Teng, Lidong
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Seetharaman, Seshadri
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Effect of the heat treatment on the chromium partition in CaO-MgO-SiO2-Cr2O3 synthetic slags2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 6, p. 1586-1597Article in journal (Refereed)
    Abstract [en]

    Mg-spinel phase is known to be important for control of Cr leaching from Cr-containing slags. The objective of the present study is to get an understanding of the phase relationships in the CaO-MgO-SiO2-Cr2O3 system with a view to control the precipitation of Cr-spinel in the slag phase. The equilibrium phases in CaO-MgO-SiO2-Cr2O3 slag system in the range of 1673 K to 1873 K (1400 °C to 1600 °C) have been investigated experimentally and compared with the results from thermodynamic calculations. The slag compositions close to the industrial slag systems were chosen. The Cr2O3 and MgO contents in the slag were fixed to be 6 and 8 wt pct, respectively. The basicity (CaO/SiO2) of the slag was varied in the range of 1.0 to 2.0. The slags were synthesized at a pre-determined oxygen partial pressure (10-4) or air (2.13 × 104 Pa) at a temperature above the liquidus temperature. The samples were then soaked at targeted temperatures for 24 hours in controlled atmosphere in order to achieve the equilibrium state before quenching in water. Four different heat-treatment regimes (defined as Ia, Ib, II.a and II.b) in Section II-D) were used in the present experiments. The lower oxygen partial pressure was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction techniques. The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer. The experimental results obtained are compared with the calculation results from Factsage software. The size of spinel crystals increased drastically after slow-cooling from 1873 K (1600 °C) followed by annealing at 1673 K (1400 °C) for 24 hours (heating regimes II) compared to samples being quenched directly after soaking at 1873 K (1600 °C) (heating regime I.a). It was found that the amount of foreign elements in the spinel phase, and other phases decreased after soaking at oxygen partial pressure of 10-4 Pa resulting in phases with less defects and foreign oxide contents compared to those treated in air. The size of spinel crystals was found to be larger in samples with lower basicity

  • 5. Andersson, Charlotte
    et al.
    Björkman, Bo
    Engström, Fredrik
    Mostaghel, Sina
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The need for fundamental measurements for a sustainable extraction of metals2010Conference paper (Refereed)
  • 6.
    Andersson, Charlotte
    et al.
    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.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mostaghel, Sina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The need for fundamental measurements for a sustainable extraction of metals2011In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 120, no 2, p. 199-204Article in journal (Refereed)
    Abstract [en]

    The increased need for efficient material processing and efficient utilisation of more complex raw materials and the need for recycling or reusing byproduct and waste streams, are all increased challenges in material processing. To cope with these challenges, there is a need for new basic physical and thermodynamic data. The present paper gives four examples, as well as preliminary data, of areas where increased knowledge of fundamental parameters will increase the possibility for a sustainable extraction of metals. The examples include measurement of solubility of pure individual slag minerals, determination of distribution of leachable elements between different mineralogical phases in slag, influence of alumina on liquidus temperature of a copper slag and thermal diffusivity measurements in magnetite based iron ore pellets, all important in different ways to increase the sustainability of the respective materials involved

  • 7. Andersson, Urban
    et al.
    Engström, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustavsson, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Karlsson, Rolf
    Vattenfall Research & Development.
    The Turbine-99 workshops - conclusions and recommendations2004In: 22nd IAHR Symposium on Hydraulic Machinery and Systems, Stockholm, Sweden, June 29 - July 2, 2004, Stockholm: IAHR , 2004Conference paper (Other academic)
  • 8.
    Brämming, Mats
    et al.
    Swerim AB, Luleå, Sweden.
    Engström, Fredrik
    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 of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process2019In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 90, no 2, article id 1800269Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    Durinck, D.
    et al.
    Katholieke University of Leuven.
    Engström, Fredrik
    Arnout, S.
    Katholieke University of Leuven.
    Heulens, J.
    Katholieke University of Leuven.
    Jones, P.T.
    Katholieke University of Leuven.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Blanpain, B.
    Katholieke University of Leuven.
    Wollants, P.
    Katholieke University of Leuven.
    Hot stage processing of metallurgical slags2008In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 52, no 10, p. 1121-1131Article in journal (Refereed)
    Abstract [en]

    Slags are an indispensable tool for the pyrometallurgical industry to extract and purify metals at competitive prices. Large volumes are produced annually, leading to important economical and ecological issues regarding their afterlife. To maximise the recycling potential, slag processing has become an integral part of the valorisation chain. However, processing is often directed solely towards the cooled slag. In this article, the authors present an overview of the scientific studies dedicated to the hot stage of slag processing, i.e. from the moment of slag/metal separation to complete cooling at the slag yard. Using in-depth case studies on C2S driven slag disintegration and chromium leaching, it is shown that the functional properties of the cooled slag can be significantly enhanced by small or large scale additions to the high temperature slag and/or variations in the cooling path, even without interfering with the metallurgical process. The technology to implement such hot stage processing steps in an industrial environment is currently available. No innovative technological solutions are required. Rather, advances in hot stage slag processing seem to rely primarily on further unravelling the relationships between process, structure and properties. This knowledge is required to identify the critical process parameters for quality control. Moreover, it could even allow to consciously alter slag compositions and cooling paths to tailor the slag to a certain application.

  • 10.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Materialförändringar i ljusbågsugnsslagger ur ett tidsperspektiv2007Conference paper (Other academic)
  • 11.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mineralogical influence of different cooling conditions on leaching behaviour of steelmaking slags2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Swedish steelmaking industry produces large amounts of by-products. In 2006, the total amount of slag produced reached approximately 1 375 000 metric tons, of which 30% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction due to it's similarities with ordinary ballast stone. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties: Volume expansion, Disintegration, Leaching of metals By controlling and modifying process parameters during slag handling in liquid state, the physical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major objectives of this work have been to investigate how different cooling methods and cooling rates influence the properties of slag products. Four types of steel slags, Ladle slag, BOF (Basic Oxygen Furnace) slag and two different EAF (Electric Arc Furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. Experiments were conducted in laboratory scale using an induction furnace. Analysis techniques used in this investigation include: thermodynamic calculations using FactSageTM, X-ray diffraction analyses (XRD), scanning electron microscope (SEM) and a standard leaching test (prEN 12457-2/3). The experimental results show that disintegrating ladle slag is volume stabilized by water granulation resulting in a product consisting of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed only 17%, 1% and 1% glass, respectively. The leaching tests showed that water granulation did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals. Variations in crystal size as well as phase composition and distribution were observed in the different materials as a result of different cooling methods. The magnesium content of the wustite-type solid solution (Fe,Mg,Mn)O in BOF slag increased when rapid cooling was used. The reactivity factor, á, was calculated for the BOF and EAF slag 1. A majority of the elements of interests in the slags became more reactive when cooled rapidly. The reactivity for silica in BOF and EAF slag 1 was increased by ~4700% and ~1200%, respectively, and for chromium by ~5300% and ~1500%.

  • 12.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mineralogical influence on leaching behaviour of steelmaking slags: a laboratory investigation2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Swedish steelmaking industry produces large amounts of by-products. In 2008, the total amount of slag produced reached approximately 1,300,000 metric tons, of which 20% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction, since it has similar or better qualities than ordinary ballast stone, which makes it a competitive construction material. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties:Volume expansion Disintegration Leaching of metalsBy controlling and modifying process parameters during slag handling in liquid state, the physical and chemical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major goal of this work has been to investigate how different treatment methods including hot stage processing, cooling rates, ageing time and chemical composition influence the final properties of the slag. Analysis techniques used in this investigation include: thermodynamic calculations using FactsageTM, X-ray diffraction analyses (XRD), scanning electron microscopy (SEM), leaching tests (EN12457-2/3) and thermo-gravimetric analyses (TG).The results from this study show that it is possible to control/change the properties of the final product by additions to the liquid slag, thereby changing the chemical composition, as well as by varying the rate and method of cooling. The mineralogical composition, the size of the crystals and the composition of some solid solutions are affected by the cooling rate. The solubility of elements such as chromium and molybdenum varies, probably due to their presence in different minerals. The reactivity of the investigated slag samples increases as the cooling rate increases.When steel slags are aged, the leaching properties of the materials are changed. The total leachability and the pH decrease for all the investigated samples. All elements except magnesium decrease in leachability. As the slags are aged CaCO3 is formed on the slag surfaces. The degree of carbonation differs between different slags, due to the presence of different calcium-rich minerals in the slag. In order to form CaCO3, the calcium-containing mineral must be dissolved. This means that the solubility of the calcium-containing mineral will affect the outcome of the carbonation. The rate of dissolution for six typical slag minerals was investigated in order to distinguish the difference in solubility between the different minerals. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags and the potential future pH values obtained under acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered slow. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed.

  • 13.
    Engström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Adolfsson, Daniel
    SSAB EMEA, Luleå.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A study of the solubility of pure slag minerals2013In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 41, p. 46-52Article in journal (Refereed)
    Abstract [en]

    Large amounts of oxidic by-product are annually produced by the steel industry worldwide. By far the largest in volume is slag, generated from different stages of steel production. In order to avoid landfilling, steelmakers usually try to process the slag into useful resources that can be used externally. However, leaching of different metals can sometimes be a problem. Since steel slags are a mixture of numerous types of minerals, the solubility of each mineral will affect the outcome of the leachability. The aim of this study was to investigate how six common slag minerals behave during dissolution. Mayenite (Ca12Al14O33), merwinite (Ca3MgSi2O8), akermanite (Ca2MgSi2O7), gehlenite (Ca2Al2SiO7), γ-dicalcium silicate (γ-Ca2SiO4) and tricalcium aluminate (Ca3Al2O6) were synthesized and their dissolution was evaluated through titration using HNO3 at constant pH. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags, and one pH value, representing acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH values, which are normal in the case of steelmaking slags. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered low. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed.

  • 14. Engström, Fredrik
    et al.
    Adolfsson, Daniel
    Yang, Qixing
    Samuelsson, Caisa
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Crystallization behaviour of some steelmaking slags2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 5, p. 362-371Article in journal (Refereed)
    Abstract [en]

    The present study was aimed at highlighting the final properties of two different steelmaking slags which undergo different cooling rates. The experiments were conducted in laboratory scale using an induction furnace. One of the slags originates from an electric arc furnace (EAF) (high-alloyed) and the second slag from a basic oxygen furnace (BOF). The treatment of the slag included re-melting along with different cooling rates. The material collected from the tests was characterized through X-ray diffraction, scanning electron microscopy as well as thermodynamic calculations which were compared with experimental results, for confirmation. The results indicate that both the EAF and BOF slags show increased reactivity with water, as well as a decrease in crystal size when rapid cooling is applied. The wüstite-type solid solution (Mg,Fe,Mn)O varies in composition depending on the cooling conditions. Metastable Ca3SiO5 was found in the rapidly- cooled BOF slag.

  • 15.
    Engström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lidström-Larsson, Margareta
    Samuelsson, Caisa
    Björkman, Bo
    Ageing investigation of steel slags from EAF (Electric Arc Furnace) processes2008In: REWAS 2008: Global Symposium on Recycling, Waste Treatment and Clean Technology / [ed] B Mishra; C Ludwig; S Das, Minerals, Metals & Materials Society, 2008, p. 353-358Conference paper (Refereed)
    Abstract [en]

    Large amounts of by-products are generated by the Swedish steel industry each year. The EAF-process generates about 400 000 ton of slag, from which 80% is deposit. An alternative to deposit is to use slag as road construction material. However, metal content in the slag can be a problem, due to the leaching. The aim of this work was to investigate how stable these materials are when ageing and kept outside. Five different EAF-slags from domestic steel plants were used in this study. The materials were characterised after 0, 6, 12, 18 and 24 month to evaluate the ageing process. Scanning electron microscope (SEM), x-ray diffraction pattern (XRD) and a standard test for leaching were used. The changes in behaviour differ between the five materials. The total leachability decreases with time for all samples. CaCO3 is formed on slag surfaces as CaO reacts with moister and CO2 in the air.

  • 16.
    Engström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Lidström-Larsson, Margareta
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Robinson, Ryan
    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.
    Leaching Behavior of Aged Steel Slags2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 4, p. 607-615Article in journal (Refereed)
    Abstract [en]

    Large amounts of slag are generated by the Swedish Steel Industry each year. The Electric Arc Furnace process generates about 200 000 ton of slag per annum, from which approximately 40% is deposited. An alternative to deposit is to use slag as road construction material. However, leaching of metals from the slag can be a reason to limit slag use in road construction. The aim of this work was to investigate how stable these materials are when aged, in an environment open to seasonable weather conditions, with respect to leaching and mineralogy. Three different EAF-slags from domestic steel plants were used in this study. The materials were characterized after 0, 6, 12, 18, and 24 months to evaluate the ageing process. The analytical techniques that were used to evaluate the effect of ageing are scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and a standard test for leaching. The changes in ageing behavior differ between the three materials. The conductivity and the pH decreases with time for all samples. The leaching of calcium, chromium as well as aluminum decreases with time while the leaching of magnesium increases. CaCO3 was formed on slag surfaces as CaO reacts with moisture and CO2 from the air.

  • 17.
    Engström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pontikes, Yiannis
    Centre for High Temperature Process and Sustainable Materials Management, Department of Metallurgy and Materials Engineering, Katholieke University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Heverlee (Leuven), Belgium.
    Geysen, Daneel
    Centre for High Temperature Process and Sustainable Materials Management, Department of Metallurgy and Materials Engineering, Katholieke University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Heverlee (Leuven), Belgium.
    Jones, Peter Tom
    Centre for High Temperature Process and Sustainable Materials Management, Department of Metallurgy and Materials Engineering, Katholieke University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Heverlee (Leuven), Belgium.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Blanpain, Bart
    Centre for High Temperature Process and Sustainable Materials Management, Department of Metallurgy and Materials Engineering, Katholieke University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Heverlee (Leuven), Belgium.
    Review: Hot stage engineering to improve slag valorisation options2011In: Proceedings of the second international Slag Valorisation Symposium: : the transition to sustainable materials management : 18-20 April 2011, Leuven, Belgium / [ed] Peter Tom Jones, Leuven: Katholieke Universitat , 2011, p. 230-251Conference paper (Refereed)
    Abstract [en]

    A number of studies are briefly reviewed dealing with hot stage processing of slags, i.e. additions during the molten state and variations of the cooling path, and the influence on the microstructure and properties of solidified slags. Emphasis is placed on research and developments in the last five years, although other works that created the thinking framework for several of the current practices are also mentioned. The additions include: a) quartz sand with concurrent oxygen injection for the minimisation of free CaO and MgO, b) various materials for the modification of the composition of liquid blast furnace slag after tapping, c) borates and boron wastes and their distribution in both synthetic and industrial stainless steel slags, d) phosphates in stainless steel slags and their distribution in BOF slags e) waste glass and fly ash for the stabilisation of stainless steel slags, f) K2CO3 for the production of potassium silicate fertiliser from steelmaking slag and g) bauxite, Al2O3 containing residues and aluminium metal that enhance the Cr recovery and minimise leaching in EAF slags. In terms of cooling, the effect of cooling rate on the final mineralogy, as a way to stabilise stainless steel slags and to control free lime formation in BOF slags, is presented. A more in-depth discussion regarding leaching performance, which has been identified as a key issue in slag valorisation, is also taking place. Although it is acknowledged that many research questions are still open and that both technical and economical barriers exist, it is strongly believed that a conscious hot stage processing step can both increase slag utilisation rates and make higher value applications achievable.

  • 18.
    Engström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mineralogical influence of different cooling conditions on leaching behavior of steelmaking slags2009Conference paper (Other academic)
  • 19.
    Feng, Yan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Kero, Jakob
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Yang, Qixing
    Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
    Chen, Qisong
    School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Engström, Fredrik
    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.
    Qi, Chongchong
    School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 5, article id 772Article in journal (Refereed)
    Abstract [en]

    Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m²/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m²/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).

  • 20.
    Feng, Yan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. School of Resource and Safety Engineering, Central South University, Changsha, China.
    Yang, Qixing
    Energy School, Xi'an University of Science and Technology, Xi'an, 710054, China.
    Chen, Qiusong
    School of Resource and Safety Engineering, Central South University, Changsha, China.
    Kero, Jakob
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Andersson, Anton
    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.
    Engström, Fredrik
    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.
    Characterization and evaluation of the pozzolanic activity of granulated copper slag modified with CaO2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 232, p. 1112-1120Article in journal (Refereed)
    Abstract [en]

    GCS, granulated copper slag, is currently utilized in cement and concrete with a low rate, due mainly to its low pozzolanic activity. The present study was thus performed by first mixing the GCS with CaO, and then melting and water-granulating the GCS-CaO mixtures, as to enhance the reactivity of GCS. Blended cements were formulated by replacing 30 wt. % of the cement, PC, with the modified GCS. The addition of CaO in GCS increased the release rates of heat from the early-age hydration of the blended cement pastes. The pastes with CSC20, the GCS of the highest CaO content (19.5%), acquired higher compressive strengths than those for the PC and other PC-GCS pastes at both 28 and 90 days of curing. The GCS richer in CaO consumed more calcium hydroxide for the formation of calcium silicate hydrates, with SEM micrographs showing a microstructure of more gel phases and less pores in PC-GCS paste. These results indicate that the modification by addition of CaO is an effective way to achieve a high reactivity for the GCS. It may then be possible to utilize the modified GCS as a high-quality supplementary cementitious material to enhance the sustainability for both copper and cement industries.

  • 21. Gahan, Chandra Sekhar
    et al.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Comparative assesment of Industrial oxidic by-products as neutralising agents in biooxidation and their influence on gold recovery in subsequent cyanidation2011In: Proceedings of the XI International Seminar onMineral Processing Technology (MPT-2010) / [ed] R. Ringh; A. Das; P.K. Banerjee; K.K. Bhattacharyya; N.G. Goswami, 2011, p. 1293-1302Conference paper (Refereed)
    Abstract [en]

    The neutralisation cost in bioleaching operations is one of the biggest operation costs and therefore the aim of the present study has been to replace the generally used lime/limestone with industrial oxidic by-products. A comparative study on the potential use of some selected industrial by-products as neutralising agents during biooxidation and their influence on subsequent gold recovery was carried out with reference to a commercial grade Ca(OH)2. The by-products used comprised of an electric arc furnace slag (EAF slag), and a slag from ladle refining (Ladle slag) both from scrap based steel production, an EAF dust and a lime sludge from paper and pulp industry (Mesa lime). Continuous biooxidation of a refractory gold concentrate was performed in single stage reactor at a retention time of 56 h with a mixed mesophilic culture. Biooxidation results as well as gold recoveries were good for all by-products investigated and similar to the results obtained with the slaked lime reference. However, cyanide consumption was elevated in the experiments with steel slags and the EAF dust partly because of a higher content of S° in the bioresidues in these experiments. It is however expected, that in a bioleaching operation with several reactors in series, that sulphur oxidation would be more complete, thereby possibly decreasing cyanide consumption.

  • 22.
    Gahan, Chandra Sekhar
    et al.
    SRM Research Institute, SRM University, Chennai.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Evaluation of oxidic by-products as neutralizing agents in biooxidation of a refractory gold concentrate and their influence on gold extraction through cyanidation2013In: Research Journal of Recent Sciences, E-ISSN 2277-2502, Vol. 2(10), p. 41-47Article in journal (Refereed)
    Abstract [en]

    The neutralization cost in bioleaching operations is one of the biggest operation costs and therefore the aim of the present study has been to replace the generally used lime/limestone with industrial oxidic by-products. A comparative study on the potential use of some selected industrial by-products as neutralizing agents during biooxidation and their influence on subsequent gold recovery was carried out with reference to a commercial grade Ca(OH)2. The by-products used comprised of an electric arc furnace slag (EAF slag), and a slag from ladle refining (Ladle slag) both from scrap based steel production, an EAF dust and a lime sludge from paper and pulp industry (Mesa lime). Continuous biooxidation of a refractory gold concentrate was performed in single stage reactor at a retention time of 56 h with a mixed mesophilic culture. Biooxidation results as well as gold recoveries were good for all by-products investigated and similar to the results obtained with the slaked lime reference. However, cyanide consumption was elevated in the experiments with steel slags and the EAF dust partly because of a higher content of S in the bioresidues in these experiments. It is however expected, that in a bioleaching operation with several reactors in series, that sulfur oxidation would be more complete, thereby possibly decreasing cyanide consumption.

  • 23. Gahan, Chandra Sekhar
    et al.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Engström, Fredrik
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Utilisation of steel slags as neutralising agents in biooxidation of a refractory gold concentrate and their influence on the subsequent cyanidation2011In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 55, no 5, p. 541-547Article in journal (Refereed)
    Abstract [en]

    A study on the possibilities to utilise steel slag as neutralising agent in biooxidation of a refractory gold concentrate has been done with reference to commercial grade slaked lime. The idea has been to reduce the operating costs for neutralisation in the biooxidation plant, which is known to be the second largest operating cost. Other benefits would be savings in cost for landfilling of slag, possibilities to recycle elements present in the slag and savings of virgin limestone deposits. The slags used were an EAF slag and a slag from ladle refining; both originating from Swedish scrap based steel-making. Continuous biooxidation of the refractory gold concentrate was conducted in a single-stage 5 L reactor at a retention time of 56 h. The neutralisation capacity was determined by comparing the amount needed, per ton of feed concentrate added, to maintain the desired pH of 1.5 during steady state operation. Slaked lime had the highest neutralisation capacity with 110 kg/ton feed followed by ladle slag and EAF slag with values of 152 and 267 kg/ton feed, respectively. Sulphide mineral oxidation was similar and high in all cases although the ladle slag results were slightly better. Gold recoveries after cyanide leaching on the residues obtained were also similar and were in the range of 86–89%. However, the cyanide consumption expressed as kilogram cyanide per ton of concentrate fed to biooxidation, was double in the case of ladle slag and three times as much for the EAF slag compared to the slaked lime experiment. The increased cyanide consumption could not be explained only by the increased amount of elemental sulphur obtained in the slag experiments. The elemental sulphur formed had different reactivities as seen from the thiocyanate formation and cyanide losses due to thiocyanate formation were 16%, 32% and 40% for EAF slag, slaked lime and ladle slag, respectively. It is concluded that the ladle slag could be a possible replacement for limestone if they are mixed in proper proportions so that the microbial carbon dioxide demand is met whereas the EAF slag is less suitable due to the very fine reaction products obtained which gave operational problems with filtration and washing. To come further, experiments with the normal multi-stage biooxidation set-up with total retention time of 120 h should be performed which would increase the sulphur oxidation and eventually also reduce the cyanide consumption.

  • 24.
    Jiang, Liang
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China.
    Bao, Yiwang
    China Building Material Academy, Key State Laboratory of Green Building Materials, Beijing 100024, China.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. School of Material Science and Engineering, Beifang University of Nationalities.
    Chen, Yuhong
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China.
    Liu, Guiqun
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China.
    Han, Fenglan
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China.
    Wei, Jie
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Deng, Jiangyuan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Formation of Spinel Phases in Oxidized BOF Slag under Different Cooling Conditions2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 11, article id 1700066Article in journal (Refereed)
    Abstract [en]

    To enhance utilization of wastes generated from steelmaking, a BOF slag sample from Ning Steel group in China is treated by oxidizing at 1500 °C for 30 min and then cooled by different methods. The treated samples are characterized, in combination with calculations using FactSage 6.4. XRD results show that iron oxides in BOF slag are converted largely by the oxidation to spinel phases, Fe3O4 and MgFe2O4, which also eliminates free CaO and MgO. EDS analyses show Fe element existing in di-calcium silicate and glass phase, which are Fe3+ ions formed by oxidation. An incorporation of Fe3+ ions into crystal structures has stabilized high temperature polymorph of C2S, β-C2S, and α’-C2S, in the treated slag samples. Fe3+ ions may also act as a network former to facilitate glass formation. This may make it possible for the glass and α’-C2S phase to complement each other, leading to a higher hydraulicity, while the BOF slag, after the spinel separation, is blended in cements. Some suggestions are proposed, based on the present and early studies, to enhance hydraulicity for the BOF slag, as well as grain sizes of spinel phases, which may result in economic and environmental benefits for steel and cement industries.

  • 25.
    Khoshkhoo, Mohammad
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Dopson, Mark
    Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    New insights into the influence of redox potential on chalcopyrite leaching behaviour2017In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 100, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Chalcopyrite (CuFeS2) is the most economically important and most refractory copper mineral when treated in conventional sulphate media leaching systems. In this study, the effect of solution redox potential on leaching of a pure and a pyritic chalcopyrite concentrate was investigated using concentrates with fresh and aged surfaces. In experiments using concentrates with fresh surfaces, the response to redox potential depended on the presence of pyrite: fresh pyritic concentrate leached more effectively at low redox potential (in agreement with reductive leaching mechanisms), while the leaching efficiencies from fresh pure concentrate were similar at high and low redox potentials. The data suggested that the reductive leaching mechanism does not necessarily result in higher and faster recoveries in the absence of the galvanic interaction induced by the presence of pyrite. It was also found that exposure of chalcopyrite to atmospheric oxidation prior to leaching (ageing) had an effect on leaching behaviour in response to redox potential: copper recoveries in leaching of aged concentrates were higher at high redox potentials. This behaviour was attributed to the presence of iron–oxyhydroxides on the surface of aged concentrates. Based on the data from this investigation and previous surface studies, it is proposed that iron–oxyhydroxides play an important role in triggering the hindered dissolution of chalcopyrite.

  • 26.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Characterisation of buildup in an electric furnace for smelting copper concentrate2015In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 54, no 4, p. 477-484Article in journal (Refereed)
    Abstract [en]

    The results from a characterization of buildup in an electric smelting furnace for treating copper-rich feed material at the Boliden Rönnskär smelter in Sweden are presented. The aim of the work was to obtain better knowledge about the mechanisms behind the formation of the buildup. Samples from the buildup were taken during the rebuilding of the furnace. The samples were characterized using chemical and mineralogical techniques. The buildup consists mainly of different phases such as spinel, matte, olivine and metalloids and has a complex and varying mineralogy, which indicates that the buildup is not formed under equilibrium conditions.

  • 27.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Development of a model for copper converting2013In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 52, no 4, p. 422-429Article in journal (Refereed)
    Abstract [en]

    Building on previous work reported in the literature, a dynamic model of the operation of the Peirce-Smith Converter has been developed to describe the distribution of the major elements present. The fundamental principle of the model was a thermodynamic calculation. The situation of non-equilibrium conditions was considered by dividing the converter into different zones linked by predefined flow parameters. The model was verified against actual converter plant data, with the simulated results for the major elements being in good agreement with the plant data. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect.

  • 28.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Minor elements in copper converting2013Conference paper (Other academic)
  • 29.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Modelling of a Cu-making converter: a necessary tool for improved recycling2014Conference paper (Other academic)
    Abstract [en]

    Process simulation is an important tool for understanding the impact of process parameters on the product quality and for the purpose of process optimisation. In the present work a dynamic, non-equilibrium model based on thermodynamics over the Peirce-Smith converter has been developed. The non-equilibrium conditions have been simulated by introducing individual but linked segments. The purpose of using segments was to consider different reaction zones which yield different conditions within the converter. The model was validated using plant data and showed good agreement for the major elements

  • 30.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Thermodynamic process modelling of black copper addition to a Peirce-Smith converter: effect on the distribution of antimony and bismuth2014In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 123, no 3, p. 157-164Article in journal (Refereed)
    Abstract [en]

    The effect of adding black copper, originating from treating waste electrical and electronic equipment (WEEE), to a Peirce-Smith converter has been investigated by using a thermodynamic process model. The model was formulated, by the authors, in an earlier publication and expanded, in the present work, to include the minor elements antimony and bismuth. The results show that the model describes the distribution of Bi well, whereas the distribution of Sb is not described as well and should only be used for trends. Addition of black copper lowers the removal of Bi and Sb compared to a converter cycle without addition. To maintain a good removal of Bi and Sb, black copper should be added as early as possible during a converter cycle.

  • 31.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Understanding the bottom buildup in an electric copper smelting furnace by thermodynamic calculations2019In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 58, no 1, p. 89-95Article in journal (Refereed)
    Abstract [en]

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

  • 32.
    Lennartsson, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Pettersson, Joachim
    Boliden Mineral AB, Skelleftehamn, Sweden.
    Large-Scale WEEE Recycling Integrated in an Ore-Based Cu-Extraction System2018In: Journal of Sustainable Metallurgy, ISSN 2199-3823, Vol. 4, no 2, p. 222-232Article in journal (Refereed)
    Abstract [en]

    At Boliden’s Rönnskär smelter, WEEE is smelted in a Kaldo process and the black copper, together or without the slag, is charged to the PS converter. This process route has proven to be a viable way to obtain a high WEEE smelting capacity in an originally ore-based process system. Experience shows that the slag in the PS converter is usually not fully liquid, and the amount of solids present in the slag increases due to introduction of slag and black copper from WEEE smelting. The effect of increased content of Al2O3 and Cr in the slag on the liquidus temperature has been calculated using FactSage both for the converter slag and for the slag in the electric smelting furnace. The potential of changed slag chemistry is discussed. The consequences of the applied praxis on the removal of Antimony in the converter have been modeled using SimuSage.

  • 33.
    Mostaghel, Sina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Stability of spinels in a high basicity EAF slag2011In: Ferrous Slag-Resource Development for an Environmentally Sustainable World: Proceedings of the 6th European Slag Conference, 20-22 October 2010, Madrid, Spain, 2011, Vol. 5, p. 147-156Conference paper (Refereed)
    Abstract [en]

    Due to environmental regulations, steel producers in Europe, are obliged to reduce the amount of landfilled material, which is mainly slag. By fulfilling technical and environmental criteria, slag can be used in civil engineering applications. One of the most important environmental considerations is the leaching behaviour of the slag, especially with respect to chromium. A considerable research effort has been devoted to decrease the leaching of chromium from the slags by forming stable spinel phases. Most of the existing work focused on spinel forming agents. In this paper, influences of three different already formed spinels, in three different amounts, on an EAF slag from a low alloyed steel production are investigated. After re-melting and solidification, mineralogical properties of the samples were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Only one of the additives resulted in formation of distinguishable chromium rich spinels, which could immobilize chromium. The results are discussed by comparison with stable phases at equilibrium based on thermodynamic calculations.

  • 34.
    Mostaghel, Sina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The effects of cooling rate on leaching behavior of some ferrous and non-ferrous slag systems2012In: Model Concept and Experiments: 9th International Conference on Molten Slags, Fluxes and Salts, Bejing 27-30 May 2012, 2012Conference paper (Refereed)
    Abstract [en]

    It has been proven that pyrometallurgical slags can be given favorable physico-mechanical characteristics which make them suitable for use in civil engineering applications providing fulfillment of various technical and environmental criteria, of which slag leaching behavior is one of the main concerns. Numerous investigations have been carried out over the last several decades to clarify the influence of cooling rate on microstructure and properties of the slag systems; however, there is controversy in the literature as to the effect of rapid cooling, e.g. water granulation, on release of potentially toxic elements. In the current work, a ladle slag, a basic oxygen furnace (BOF) slag, two different electric arc furnace (EAF) slags, from low-alloyed and high-alloyed steel production, and three different “fayalite-type” slags, from zinc-copper smelting processes with different Fe/SiO2 ratios, are investigated. Semi-rapidly solidified (in crucible system) and water granulated samples for each composition were prepared. The solidified materials were characterized using commonly applied characterization techniques. The experimental work is compared with thermodynamic calculations using the FactSageTM thermodynamic package. Standard European leaching tests were carried out for all samples to investigate the slag leaching behaviors. Results show that rapid solidification and generated amorphous structure do not necessarily immobilize environmentally concerned elements in the glassy network. Instead, due to several factors, a higher reactivity is observed and trace elements dissolve more readily in the aqueous solution. The main reasons behind such a behavior including higher contents of metastable phases, different surface structures, oxidation and increased amount of grain boundaries are thoroughly discussed.

  • 35.
    Rodushkin, Ilya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Baxter, Douglas
    Engström, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Inorganic constituents of nuts and seeds2011In: Nuts and Seeds in Health and Disease Prevention, Elsevier, 2011, p. 65-72Chapter in book (Refereed)
    Abstract [en]

    This chapter presents data on the inorganic components of hazelnuts, walnuts, almonds, pecans, cashews, Brazil nuts, pistachios, pine nuts, peanuts, coconuts, pumpkin seeds, and sunflower seeds. Based on average consumption data for nuts and seeds, their nutritional significance and toxicological relevance in dietary intake are discussed.

  • 36.
    Sar, Suchandra
    et al.
    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.
    Sparrman, Tobias
    Umeå University.
    Engström, Fredrik
    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.
    Characterization of Double Leached Waelz Oxide for Identification of Fluoirde Mineral2019In: Metals, ISSN 2075-4701, Vol. 9, no 3, article id 361Article in journal (Refereed)
    Abstract [en]

    Double leached Waelz oxide (DLWO), with 76% zinc, is a secondary zinc containing raw materials obtained by the treatment of electric arc furnace dust. The content of fluoride in DLWO is still too high for direct leaching, as fluoride has a detrimental effect on electrowinning for zinc production. Knowledge of the characteristics of DLWO, and especially on how a fluoride mineral might exist, can contribute to further improvement of the selective leaching for the removal of fluoride. In this study, DLWO was characterized using analytical techniques, such as inductively coupled plasma-optical emission spectroscopy (ICP-OES), 19F liquid-state nuclear magnetic resonance (19F LS NMR), X-ray powder diffraction analysis (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and 19F solid-state nuclear magnetic resonance (19F SS NMR). This study showed that DLWO mainly consisted of zincite (ZnO), cerussite (PbCO3) and a spinel containing zinc, iron and manganese. The fluoride mineral identified was calcium fluoride (CaF2). In SEM analysis, fluorine was found in larger grains together with calcium and oxygen, which was possibly calcium carbonate.

  • 37.
    Strandkvist, Ida
    et al.
    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.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Chromium leaching from low-alloy EAF slag: Influence of ageing and FeO content2013Conference paper (Refereed)
    Abstract [en]

    Slag produced as a by-product from steelmaking is not utilized to the extent that could be possible. In Sweden and Europe, too much steelmaking slag is still deposited in landfills. Of the slag that is re-used, most is used in road construction, whereas the amount used in other more high-value applications is very low. The main technical reasons for the limited re-use of steelmaking slags are usually: slag disintegration, slag expansion and leaching from the slag, of which the latter is the most difficult to control. This paper discusses the relationships between the mineralogy of steelmaking slag and factors such as leaching of chromium and ageing of the slag. Examples from laboratory experiments and full-scale trials to modify the slag are given.

  • 38.
    Strandkvist, Ida
    et al.
    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.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Synthesis and dissolution of slag minerals: A study of β-dicalcium silicate, pseudowollastonite and monticellite2015In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 54, no 4, p. 446-454Article in journal (Refereed)
    Abstract [en]

    Leaching of slag must be limited when slag is used in other areas than landfill. As slag is composed of different minerals, the properties of slag, inter alia the dissolution, depend on these minerals. If the leaching properties of each mineral are known, counter measurements can be taken to prevent the leaching of unwanted elements. In this study, the dissolution of three common slag minerals will be examined. The three minerals; boron-stabilised β-dicalcium silicate, pseudowollastonite and monticellite were synthesised. The dissolution was measured by setting pH to 4, 7 or 10 and adding 0.05 g mineral in the size range 20-38 μm, and the HNO3 consumption required 3 to maintain the pH level was recorded during 40 h. As expected, the dissolution increases for all minerals when pH decreases. The boron- stabilised β-dical cium silicate was the only mineral fully dissolved at all pH levels, while pseudowollastonite and monticellite only dissolved completely at pH 4.

  • 39.
    Strandkvist, Ida
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Andersson, Anton
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Influence of basicity on chromium leaching of low alloy EAF slag2017Conference paper (Refereed)
    Abstract [en]

    Due to excellent properties as a construction material slag is rising in popularity as a resource. However, some properties prevent usage, one of those is leaching of chromium. The leaching of slag is governed by the solubility of theminerals. By eliminating soluble minerals that contain chromium the chromiumleaching should decrease. In some low alloy EAF slag, brownmillerite, has beensuspected to leach chromium. By increasing the basicity of slag the formation of brownmillerite should be avoided. Low alloy EAF slag with basicity of 2.7 was altered by remelting the slag with SiO2 additions. The mineralogical composition was identified using SEM EDS and XRD. Slag samples were treated inan autoclave to simulate ageing. The autoclave treatment was successful as theremelted slag without modification leached with the same magnitude as the naturallyaged reference sample. At basicity 2.7, the investigated slag had the highest leaching of chromium, at average 2 mg/kg. The chromium leaching decreased to 0.2 mg/kg at basicity 2.4. The decrease of chromium leaching was connected to the decrease of brownmillerite. Lower basicity did not eliminate leaching ofchromium as merwinite, another mineral able to contain chromium, was formed instead of brownmillerite.

  • 40.
    Strandkvist, Ida
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pålsson, Kjell
    Ovako Hofors.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The influence of iron oxide on the chromium leachability of EAF slag: a full-scale study at Ovako Hofors2012In: Scanmet IV: 4th International Conference on Process Development in Iron and Steelmaking, Luleå: MEFOS , 2012, Vol. 2, p. 329-338Conference paper (Refereed)
    Abstract [en]

    Ovako Hofors has adopted a zero-waste vision. The purpose of this vision is to identify application areas for all residues as alternatives to deposition. In terms of tonnage, the largest residue from the steel production at Ovako in Hofors is the slag from the electric arc furnace, EAF. The properties of EAF slag make it an excellent construction material, for instance, as an aggregate in asphalt. The leaching of chromium must be controlled if the slag is to be used as construction material in an environmentally friendly way. Ovako Hofors is actively working to keep the leaching of chromium at a low level. Progress has been made earlier by introducing dolomite in the slag forming agents. Phases capable of stabilising chromium are spinels and solid solution of MgO. The aim of this work is to investigate if it is possible to completely prevent leaching of chromium by stabilising the solid solution of MgO by increasing the FeO content.All the experiments were performed in the EAF at Ovako Hofors. Three different methods to raise the FeO content in the slag were tried and evaluated. Slag produced earlier was used as reference samples. From each test, three different slag samples were collected and analysed. To evaluate the results SEM, XRD, leaching and chemical analyses were conducted.A new oxygen burner increased the iron oxide content, while the other two methods did not show any additional increase. Leaching of chromium could only be detected in a few of the slag samples. Although this makes correlations harder to see, it indicates that a higher FeO content may affect the leaching in a positive way. It was discovered that the leaching of chromium does not depend on the chromium content in the slag, thereby proving the hypothesis that chromium can be bound in stable phases to prevent it from leaching.

  • 41.
    Strandkvist, Ida
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effect of FeO/MgO Ratio on Dissolution and Leaching of Magnesiowüstite2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 6, article id e201600322Article in journal (Refereed)
    Abstract [en]

    If slag is to be used as construction material, the leaching of some elements, such as chromium must be limited. The leaching of slag depends on the leaching properties of the minerals in the slag. However, the leaching/dissolution properties of individual slag minerals are usually not studied. One common slag mineral that can contribute to the leaching of chromium is magnesiowüstite. The object of this study is to determine whether magnesiowüstite can be modified to avoid chromium leaching. Magnesiowüstite samples with different FeO/MgO ratios with and without chromium content are manufactured. The dissolution is evaluated at pH 7 and 10 using the magnesiowüstite samples without chromium, at size fraction 20–38 μm, by measuring the acid consumption required to maintain constant pH level. The magnesiowüstite samples with chromium content are leached at pH 10; the leachate is analyzed for chromium. The results are unanimous, with increasing FeO content the dissolution of magnesiowüstite and leaching of chromium decrease. At pH 10 the magnesiowüstite, with ≥60 wt% FeO show no sign of dissolution and no chromium leaching could be detected with ≥70 wt% FeO. The results prove that the FeO content can stabilize magnesiowüstite and, thereby, prevent chromium leaching

  • 42. Tossavainen, Mia
    et al.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Menad, Nourreddine
    Yang, Qixing
    Stability of modified steel slags2005In: EUROSLAG: Slags - providing solutions for global construction and other markets. Proceedings, 2005Conference paper (Refereed)
  • 43. Tossavainen, Mia
    et al.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Qixing
    Menad, Nourreddine
    Lidström-Larsson, Margareta
    Björkman, Bo
    Characteristics of steel slag under different cooling conditions2007In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 27, no 10, p. 1335-1344Article in journal (Refereed)
    Abstract [en]

    Four types of steel slags, a ladle slag, a BOF (basic oxygen furnace) slag and two different EAF (electric arc furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. The aim of this work was to investigate the effect of different cooling conditions on the properties of glassy slags with respect to their leaching and volume stability. Optical microscopy, X-ray diffraction, scanning electron microscope and a standard test leaching (prEN 12457-2/3) have been used for the investigation. The results show that the disintegrated ladle slag was made volume stable by water granulation, which consisted of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed 17%, 1% and 1% glass, respectively. The leaching test showed that the glass-containing matrix did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals and their different distributions.

  • 44.
    Xue, Peng
    et al.
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    He, Dongfeng
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Xu, Anjun
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Gu, Zongxi
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Modification of industrial BOF slag: Formation of MgFe2O4 and recycling of iron2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 712, p. 640-648Article in journal (Refereed)
    Abstract [en]

    Efficient recycling of iron oxide from industrial BOF (basic oxygen furnace) slags has always been an issue in metallurgy. In this study, a new method was developed for the efficient recycling of iron oxide: It was transformed into magnesioferrite spinel (MgFe2O4) by mixing the industrial BOF slag with 6.00% SiO2 first, and then the modified slag got cooled down from 1400 °C to 1270 °C at a rate of 1 °C/min. Finally, the Fe resources were recycled by magnetic separation. Various experiments and analyses such as XRD, SEM–EDS analyses, Factsage thermodynamic simulation, magnetization characterization, dry magnetic separation, and chemical analysis were carried out. The results show that the obtained MgFe2O4 has a high melting point (1716.76 °C in theory) and ferromagnetism (specific magnetic susceptibility of (8.03–206.84) × 10−5 m3/kg). Therefore, it could be separated from the weakly magnetic industrial BOF slag (specific magnetic susceptibility of (0.024–0.136) × 10−5 m3/kg). Furthermore, this new method could be applied to different BOF slags. The yield of MgFe2O4 increased to above 80% when the content of Fe2O3 was in the range 25.81–46.90%. After the modification and magnetic separation, the total Fe content increased by 15.80%, from 21.20% in the industrial BOF slag to 37.00% in the magnetic slag. This is better than the direct magnetic separation of iron oxide without any treatment. The magnetic slag could be reused as either a sintering or slag splashing material. The nonmagnetic slag can be used to produce high value-added building materials. Hence, this new method can be used to recycle the iron oxide from industrial BOF slags, achieving the sustainable development of the iron and steel industry.

  • 45.
    Xue, Peng
    et al.
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing , Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Xu, Anjun
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    He, Dongfeng
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing , Metallurgical and Ecological Engineering School, University of Science and Technology, Beijing, State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Liu, Guiqun
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Engström, Fredrik
    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.
    Research on the sintering process and characteristics of belite sulphoaluminate cement produced by BOF slag2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 122, p. 567-576Article in journal (Refereed)
    Abstract [en]

    The sintering process of belite sulphoaluminate cement (CSA1) clinker is still not clear to date. Besides, there are few reports concerning producing CSA by recycled BOF slag. Therefore, the sintering process of CSA was investigated from this perspective and the results can be a reference for BOF slag disposal. Four kinds of CSA clinkers with different additions of BOF slag were sintered at 1300 °C for 30 min. The sintering process was traced by heating microscope and the characteristics were analyzed by XRD, SEM-EDS and TAM Air. The results showed that the sintering degree of CSA clinker could be predicted by analyzing its sintering process. Furthermore, BOF slag could improve the melting state of CSA clinkers due to its composition containing iron oxide, manganese oxide and magnesium oxide. However, expansion was detected when the temperature reached 420 °C, which was arose by combined factors, namely volatilization of CO2 decomposed from MgCO3 and the thermal expansion of raw materials itself. The rational ratios of C2S, C4A3View the MathML sourceS¯, C4AF in CSA clinker with 14% BOF slag as raw material stood at 50%, 30%, 20% and its early hydration behavior was better than that of ordinary Portland cement (OPC) at the initial 16 h.

  • 46.
    Xue, Peng
    et al.
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Liu, Guiqun
    School of Materials Science and Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Han, Feng Lan
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Liang, Jiang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    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.
    Air Quenching of Steel slag to Enhance its Hydraulic Activity for Recycling the Slag as Meterials in Cement and Concrete Applications2017In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 737, p. 488-493Article in journal (Refereed)
    Abstract [en]

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

  • 47. Yang, Qixing
    et al.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Adolfsson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modification study of a steel slag to prevent the slag disintegration after metal recovery and to enhance slag utilization2009In: Molten 2009: proceedings of the VIII International Conference on Molten Slags, Fluxes & Salts, 18-21 January 2009, Santiago, Chile / [ed] Mario Sanchez; Roberto Parra; Gabriel Riveros; Carlos Diaz, Concepción, Chile: GECAMIN, 2009, p. 33-41Conference paper (Refereed)
    Abstract [en]

    A slag sample was produced during laboratory reduction tests of a steel slag for metal recovery. The reduction of the metal oxides changed slag basicity (CaO/SiO2) to about 1.6 and led to the formation of g-phase of dicalcium silicate, g-Ca2SiO4, which resulted in disintegration of the slag sample. A modification study of the slag sample after reduction was performed. The study aimed at acquiring data and fundamental information for choosing environmentally friendly and cost effective methods for preventing slag disintegration in order to increase slag utilization. Effects of some additives, containing SiO2 or P2O5, on the formation of the g-Ca2SiO4 were examined via slag melting tests. The slag was also modified by fast cooling, via air granulation using a laboratory granulation system. In these modification tests, a laboratory induction furnace was used to melt the samples at approximately 1700°C. Samples obtained before and after the modification tests were characterized. The study results showed that g-Ca2SiO4 and fines did not appear by adding MCP-F or a product from iron ore processing to increase P2O5 content in the reduced slag from a very low level, 0.07%, to around 0.3% or higher. A sand addition of 5.12% in the reduced slag could decrease slag CaO/SiO2 value to 1.34, which prevented Ca2SiO4 formation and slag disintegration. The reduced slag was cooled quickly via air granulation, which prevented formations of g-Ca2SiO4 in slag granules. Based on results from the melting tests and other literature, fundamental aspects regarding slag modification and treatment are discussed, along with utilization of the slag after the oxide reduction and modification.

  • 48.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Li, Jianli
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Xu, Anjun
    USTB Beijing.
    Dissolution behavior of fluorine in AOD slag from the production of stainless steel after treatment for volume stabilization2012In: Scanmet IV: 4th International Conference on Process Development in Iron and Steelmaking, Luleå: MEFOS , 2012, Vol. 2, p. 517-526Conference paper (Refereed)
    Abstract [en]

    The slag tapped from AOD (Argon Oxygen Decarburization) converter disintegrates, sometimes, during cooling. Slag fines from the disintegration are difficult to handle and to use as materials for construction purposes. In our early research work, AOD slag samples were modified by agents containing B or P elements. Different slag cooling procedures were also used, including cooling inside crucibles after re-melting and granulation by water and gas. By the modification, the slag samples gained the volume stability and mechanical properties required for its utilization as construction materials.Different types of stainless steel slag from Outokumpu Stainless Company have been used to manufacture environmentally sound and ce-marked construction products. Fluorine leaching from some of the AOD slag samples were investigated. In some other steelmaking processes, such as hot metal pretreatment, secondary steel refining and the production of high alloyed steels, fluorite can be charged as a slag forming agent, with some F and CaF2 existing in the slag. When these slags are reused as road construction or landfill materials, a potential fluorine contamination to the ground water may occur.The present research work is carried out regarding both the volume stability and F-immobilization for AOD slag samples. The studied slag samples consist of new ones from plant gas granulation tests and some old ones from our early studies. Compositions and cooling conditions are selected as main parameters for slag tests using laboratory equipment. Samples from the plant and laboratory slag tests are characterized by XRD, SEM and leaching with EN12457-2/3. Formations of mineral phases for F-immobilization in the slag samples are also predict using FACTSAGE program.Results from the present study indicate that the chemical composition and cooling condition for a slag are the two important parameters to control F leaching. These two parameters should be considered together in an optimum way to treat the slag for fluorine immobilization.It may be possible, based on the results obtained, to develop some environmental friendly and cost effective methods for the stainless steel industry to treat the AOD slag. Some slag products with high volume stability and minimum F-dissolution may thus be obtained to use as construction materials for saving valuable natural resources.

  • 49.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Haase, Björn
    Wedholm, Anita
    Stabilization of EAF slag for use as construction material2008In: REWAS 2008: Global Symposium on Recycling, Waste Treatment / [ed] B. Mishra; C. Ludwig; C. Das, Minerals, Metals & Materials Society, 2008, p. 49-54Conference paper (Refereed)
    Abstract [en]

    MiMeR, the Minerals and Metals Recycling Research Centre at Lulea University of Technology, Sweden, started industry-related research work to stabilize an EAF slag from Hoganas AB with of CaO/SiO2 values near to 3.2. The intention was to determine the suitability of the EAF slag as construction material after stabilization. Some of the stabilizers effective for preventing disintegration of AOD slag were examined in laboratory tests for stabilization of the EAF slag. The EAF slag samples were mixed together with stabilizers for melting at 1600{o}C and then cooling in a crucible system. With a laboratory granulation system, the liquid EAF slag was cooled rapidly using air. Samples from the tests were characterized by different techniques, including XRD and SEM. Some of the results from the work may be useful for preventing slag disintegration and, thus, enhancing utilization of the EAF slag as construction material, thereby saving valuable natural resources

  • 50.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Tossavainen, Mia
    Adolfsson, Daniel
    Treatments of AOD Slag to enhance recycling and resource conservation2005In: Securing the future: international conference on mining and the environment, metals and energy recovery : proceedings, Stockholm: SweMin , 2005Conference paper (Refereed)
    Abstract [en]

    Laboratory treatment tests of AOD slag from stainless steelmaking have been performed by MiMeR. An induction furnace was used for slag reduction tests. The reduced slag was either water granulated or cooled in an Al2O3 crucible. Metal droplets, suitable for recycling as metallic materials in the steelmaking, were recovered after the slag granulation. Characterizations of slag samples from the tests show considerable influences of the treatments on physical and mineralogical properties of the slag. Some other possible methods for treatments and utilization of the slag were also discussed.

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Output format
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  • asciidoc
  • rtf