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  • 1.
    Chen, Yuhong
    et al.
    School of Material Science and Engineering, Beifang University for Nationalities Yinchuan, Ningxia.
    Jiang, Liang
    School of Material Science and Engineering, Beifang University for Nationalities Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Fenglan, Han
    School of Material Science and Engineering, Beifang University for Nationalities Yinchuan, Ningxia.
    Identification of Fe-containing phase in oxidation process of BOF slag2017In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 726, p. 564-568Article in journal (Refereed)
    Abstract [en]

    In this paper, the Fe-containing phases in BOF slag were identified before and after oxidized with atmospheric air. XRD and SEM with EDS results showed that The element Fe existed in slag in the form of calcium ferrite, wustite solid solution and hematite. Mg solid solute in wustite. After oxidized, magnetite became the major mineral phase in slag and Mg+ replace the Fe2+ of magnetite crystal to form spinel

  • 2. 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.

  • 3.
    Han, Fenglan
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Wu, Laner
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Guo, Shengwei
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Du, Chun
    College of Chemical Engineering, Beifang University of Nationalities Wenchangbeilu, Yinchuan.
    Fluoride evaporation during thermal treatment of waste slag from Mg production using pidgeon process2012In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 581-582, p. 1044-1049Article in journal (Refereed)
    Abstract [en]

    Fluoride evaporation from Mg slag samples was investigated. F content in the original slag sample from an Mg factory was 1.65%, which decreases to 0.98-1.54% in the samples heated at 1000-1400°C for 3 hours. The values of F evaporation from the test samples were 6.7-40.6%. The fluorides may evaporate in the atmosphere, causing air pollution. Some suggestions were presented based on study results obtained to minimize fluoride emissions and improve environmental performances of the Mg production by using Pidgeon process

  • 4.
    Han, Fenglan
    et al.
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Laner
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Du, Chun
    College of Chemical Engineering, Beifang University of Nationalities Wenchangbeilu, Yinchuan.
    Innovative utilization of a borate additive in magnesium production to decrease environmental impact of fluorides from pidgeon process2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 690-693, p. 378-389Article in journal (Refereed)
    Abstract [en]

    The present authors have utilized, for the first time, H3BO3 as an additive in pilot scale experiments of Mg production using Pidgeon process. The results from the experiments revealed positive effects of H3BO3 on both quantity and quality of the Mg metal crowns. Besides acting as a catalyzer for MgO reduction, H3BO3 stabilized also β-Ca2SiO4 in the Mg slag. Based on these results, H3BO3 may be adopted as an innovative additive replacing fluorite in the Mg production, to enhance sustainability and environmental soundness for the Pidgeon process in China.

  • 5.
    Han, Fenglan
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Laner
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Guo, Shengwei
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Treatments of magnesium slag to recycle waste from Pidgeon process2012In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, p. 1657-1667Article in journal (Refereed)
    Abstract [en]

    Magnesium slag powder from a local magnesium plant was treated to improve the volume stability for its application as building materials. The slag was mixed with borates, pressed into briquettes, and then sintered at high temperature. SEM studies show that at the higher temperature Ca 2SiO4 polymorphs were stabilized by Na and B ions in the added borates. The free MgO content in the slag was also decreased by the sintering treatment. The slag powder, after mixing with 0.4-0.6% of borates and sintered at 1200°C in 5-6 hours, has become volume stable aggregates. It is then possible to use the treated slag in constructions, saving valuable natural resources and decreasing the global warming impact from magnesium production via Pidgeon process

  • 6.
    Han, Fenglan
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Laner
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Guo, Shengwei
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Jiang, Yong
    School of Material Science and Engineering, Beifang University of Nationalities, Yinchuan.
    Environmental performance of fluorite used to catalyze MgO reduction in pidgeon process2012In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 577, p. 31-38Article in journal (Refereed)
    Abstract [en]

    Environmental performances of fluorite used as catalyzer for chemical reaction between MgO and Si were investigated by performing pilot scale experiments of Mg production. F amounts of 0.012-0.116 kg were added in the charged briquettes and Mg slag generated from the chemical reaction in most of the tests weighted 4.26-4.96 kg with F contents ranging 0.21-2.52%. Based on high recoveries of F, 83-100%, in the slag after the reaction, it is estimated that there are little or no F compounds leaving the retorts during the pilot tests. However, high amount of F, 72.9 mg/kg, was leached out from an Mg slag sample obtained from an Mg plant, making it necessary to decrease amount of fluorite used as catalyzer for the reaction or to improve operation conditions, thus, enhancing rate for chemical reaction between MgO and Si in Pidgeon process

  • 7.
    Han, F.L.
    et al.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Wu, L.N.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Du, C.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Fluorine vaporization and leaching from Mg slag treated at high temperature2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 726-731, p. 2898-2907Article in journal (Refereed)
    Abstract [en]

    Pidgeon process is used by more than 300 plants in China to produce magnesium (Mg) metal. Fluorite, ranging 2-3%, is often mixed in raw materials to catalyze the Mg production. The Mg slag from the production then contains F of several mass percent. When the Mg slag is used in construction or treated for recycling, possible F pollutions are of concerns. The present study used slag samples containing F of 0.98-2.15% from an Mg factory in northwest China. Both treatments at 1000-1400°C and leaching tests before and after the treatments were conducted for the slag samples. The study results show influences of the treatments on mineral compositions of the samples, which controlled F contents in both the slag samples and leachates. The results are reported and discussed. Some suggestions are also presented to minimize fluorine pollutions and to improve environmental performances of the Pidgeon process

  • 8.
    Hu, Xianfeng
    et al.
    Luleå tekniska universitet.
    Sundqvist-Ökvist, Lena
    Swerea MEFOS AB, Luleå tekniska universitet, SSAB Tunnplåt AB, LKAB.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Thermogravimetric study on carbothermic reduction of chromite ore under non-isothermal conditions2015In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 42, no 6, p. 409-416Article in journal (Refereed)
    Abstract [en]

    In this paper, the reduction of chromite ore by coke was investigated by means of thermogravimetric analysis under non-isothermal conditions (from room temperature to 1823 K). The fractional reduced samples were examined by SEM/EDS and X-ray diffraction analyses. The experimental results showed that the reduction of iron in the chromite ore started before that of chromium in the ore, and the reduction of chromium and iron in the ore overlapped to some degree. Chromium iron carbide was found to be the transient phase during the reduction, and a chromium gradient was found in the fractional reduced sample at temperature higher than 1623 K. A four-stage reduction process was proposed: one stage involving the reduction of iron in the chromite ore and three stages involving the reduction of chromium in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore were considered. The difficulty in the reduction of the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of the component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes further reduction very difficult.

  • 9.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS.
    Sundqvist-Öqvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Eriksson, Johan
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Combined Chromium Reduction and Alloying of Steel2016In: Scanmet V, 2016Conference paper (Refereed)
  • 10.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS AB.
    Sundqvist-Öqvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Process Metallurgy Department, Swerea MEFOS AB.
    Eriksson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Direct alloying steel with chromium by briquettes made from chromite ore, mill scale, and petroleum coke2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 5, article id 1600247Article in journal (Refereed)
    Abstract [en]

    In this work, the effectiveness of using briquettes made from chromite ore, mill scale, and petroleum coke for direct chromium alloying is tested by induction furnace trials carried out in three different scales. The experimental results show that steel scrap can be alloyed with chromium by the chromite ore in the briquettes and the Cr yield from the chromite ore increases with the increase in mill scale addition to the briquettes: the more mill scale is added to the briquettes, the lower the mass ratio of Cr to (Cr+Fe) would be, leading to a higher Cr yield from the chromite ore. Specifically, the maximum Cr yield from the chromite ore is 99.9% when the mass ratio of Cr to (Cr+Fe) in the briquettes is 0.05, and being 93.0% when the ratio is 0.10. However, when the ratio of Cr to (Cr+Fe) in the briquettes reaches 0.20, the maximum Cr yield is only 67.1%. The reduction of chromite ore under the present experimental conditions is promoted by a solid-state reduction mechanism

  • 11.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS.
    Teng, Lidong
    Division of Materials Process Science, KTH-Royal Institute of Technology.
    Wang, Haijuan
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology .
    Sundqvist-Öqvist, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Seetharaman, Seshadri
    Division of Materials Process Science, KTH-Royal Institute of Technology .
    Carbothermic Reduction of Synthetic Chromite with/without the Addition of Iron Powder2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 12, p. 2147-2155Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Hu, Xianfeng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Process Metallurgy Department, Swerea MEFOS AB, Luleå, Sweden.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sundqvist-Ökvist, Lena
    Swerea MEFOS AB, Luleå tekniska universitet, SSAB Tunnplåt AB, LKAB.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Thermal Analysis Study on the Carbothermic Reduction of Chromite Ore with the Addition of Mill Scale2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 5, p. 562-570Article in journal (Refereed)
    Abstract [en]

    This paper presents a fundamental study on the carbothermic reduction of chromite ore with the addition of mill scale, which forms the basis for designing an alloying precursor, “chromite ore + mill scale + carbon,” for direct chromium alloying. The reduction of chromite ore by petroleum coke with or without the addition of mill scale is investigated by Thermogravimetric Analysis (TGA) under non-isothermal conditions (from room temperature to 1823 K) in the argon atmosphere; the fractional reduced samples were characterized by SEM/EDS and XRD analyses. The experimental results show that the mill scale in the alloying mixture is reduced to high active iron first and disseminated around the chromite ore particles; the reduction of chromite ore is enhanced with the addition of mill scale especially at temperatures higher than 1623 K, and the enhancing effect increased with increasing mill scale addition. The enhancing effect is attributed to the presence of molten Fe–C alloy in the vicinity of chromite ore, which can decrease the thermodynamic activity of chromium by having chromium in situ dissolve into the melt.

  • 13.
    Jia, Qi
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Guo, Lijie
    Beijing General Research Institute of Mining and Metallurgy.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Xue, Peng
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Liu, Guiqun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Jiang, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. jiang.liang@ltu.se .
    Effects of fine content, binder type and porosity on mechanical properties of cemented paste backfill with co-deposition of tailings sand and smelter slag2016In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 21, no 20, p. 6971-6988Article in journal (Refereed)
    Abstract [en]

    Mine backfilling is a process where the underground voids resulted from mining are filled with waste materials. The potential of co-depositing iron sand produced from smelting process with tailings sand was investigated in the present study. Different amounts of iron sand were mixed with the tailings sand to prepare cemented paste backfill (CPB) samples. Two types of binders were used. Uniaxial compression tests were performed for the CPB samples after 28 days of curing. The porosities of the samplers after curing were calculated to correlate the porosity with the uniaxial compression strength, UCS. Results from uniaxial compression tests showed that the amount of iron sand and the type of the binder influences the UCS, as well as content values of fines and porosity. These results demonstrated the possibility for a part of Fe-sand to be deposited together with the tailings sand to increase UCS values for the CPB samples, which will be beneficial for both mining operation and environmental protection.

  • 14.
    Jiang, L.
    et al.
    School of Material Science and Engineering, North Minzu University, Yinchuan, China.
    Bao, Y.
    China Building Material Academy, Key State Laboratory of Green Building Materials, Beijing, China.
    Chen, Y.
    School of Material Science and Engineering, North Minzu University, Yinchuan, China.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Xue, T.
    School of Material Science and Engineering, North Minzu University, Yinchuan, China.
    Liu, G.
    School of Material Science and Engineering, North Minzu University, Yinchuan, China.
    Han, F.
    School of Material Science and Engineering, North Minzu University, Yinchuan, China.
    Kinetics of the Oxidation Modification Process of CaO-SiO2-FeO-MgO Slag: [CaO-SiO2-FeO-MgO体系钢渣的氧化改质动力学研究]2018In: Cailiao Daobao/Materials Review, ISSN 1005-023X, Vol. 32, no 2, p. 650-656, 671Article in journal (Refereed)
    Abstract [en]

    An investigation of mineralogical phases in industrial slag transferred from non-magnetic to magnetic substances was carried out in this study, aiming at extraction of superfluous wustite and stabilization of free lime and free periclase. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to investigate the mineralogy and phase distribution. Wet magnetic separation was conducted to determine the recovery rate of iron. The thermodynamic and kine-tic calculations for the oxidation of steel slag in a CaO-SiO2-FeO-MgO system were also performed, and the results were compared with a CaO-SiO2-FeO system. XRD analysis and SEM-EDS observation confirmed the conversion from non-magnetic wustite to magnetite spinel (magnetite/magnesioferrite) after oxidation. Magnetic separation experiment indicated that the optimal oxidation temperature is 1 100℃, which coincided well with the thermodynamic calculations. The addition of periclase had a significant influence on the formation of spinel and leaded to the presence of spinel under a partial pressure of oxygen range log10(PO2)=4.3 (correspon-ding to air). The oxidation process of steel slag could be divided into three steps: initial incubation, chemical reaction and diffusion. 

  • 15.
    Jiang, Liang
    et al.
    China Building Material Academy, Key State Laboratory of Green Building Materials, Beijing; School of Material Science and Engineering, Beifang University for Nationalities Yinchuan, Ningxia.
    Bao, Yanping
    China Building Material Academy, Key State Laboratory of Green Building Materials, Beijing.
    Hu, Xianfeng
    Process Metallurgy Department, Swerea MEFOS AB.
    Chen, Yi
    School of Material Science and Engineering, Beifang University of Nationalities.
    Liu, Guiqun
    School of Material Science and Engineering, Beifang University of Nationalities.
    Han, Feng Lan
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    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.
    Wu, Jing
    School of Material Science and Engineering, Beifang University of Nationalities.
    Experimental investigation on BOF slag oxidation in air2019In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 46, no 8, p. 747-754Article in journal (Refereed)
    Abstract [en]

    Basic oxygen furnace (BOF) slag contains a significant amount of iron-containing species, which is considered to be iron resources and therefore need to be recovered. In this work, the oxidation behaviour of BOF slag under air (at selected oxidation temperatures and holding time) was investigated to explore the potential of transforming non-magnetic wustite in the BOF slag into magnetic spinel, which may subsequently be recovered by magnetic separation. The experimental results show that the iron-containing spices in the BOF slag can be oxidised into magnetic spinel phases in the investigated temperature range of 1000–1150°C and thereafter be recovered by magnetic separation. The formation of these phases is closely related to the oxidation temperatures and holding time: a higher oxidation temperature and longer holding time lead to a larger amount of formed magnetic species; however, the amount of formed magnetic species decreases at elevated temperature (>1050°C) and with extended holding time (>40 min).

  • 16.
    Jiang, Liang
    et al.
    School of Material Science and Engineering, North Minzu University, Yinchuan, 750021, China;Key State Laboratory of Green Building Materials, China Building Material Academy, Beijing, 100024, China.
    Bao, Yiwang
    Key State Laboratory of Green Building Materials, China Building Material Academy, Beijing, 100024, China.
    Chen, Yuhong
    School of Material Science and Engineering, North Minzu University, Yinchuan, 750021, China.
    Liu, Guiqun
    School of Material Science and Engineering, North Minzu University, Yinchuan, 750021, China.
    Zhang, Xiaoli
    School of Material Science and Engineering, North Minzu University, Yinchuan, 750021, China.
    Han, Fenglan
    School of Material Science and Engineering, North Minzu University, Yinchuan, 750021, China.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Structural Characteristics and Hydration Kinetics of Oxidized Steel Slag in a CaO-FeO-SiO2-MgO System2019In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 38, no 1, p. 290-300Article in journal (Refereed)
    Abstract [en]

    Although steel slag exhibits cementitious properties, the addition of steel slag in cement is still limited due to both the presence of excess iron oxides and instability of free lime and periclase. This paper proposes a method for oxidizing molten slag in air, aiming at extraction of superfluous wustite and stabilization of free lime and periclase. Mineralogical characteristics of raw slag and modified products were examined using X-ray diffraction (XRD), scanning electron microscopy equipped with backscattered electron imaging (SEM-BEI), energy dispersive spectrometry (EDS) and thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC). Thermodynamic calculations were performed to aid to discuss the experimental results. The results indicate that non-magnetic wustite and periclase are transformed into magnetic spinel (magnetite/magnesioferrite) after oxidation. Temperature has a significant effect on the formation of spinel. The mass fraction of free lime decreases from 3.54 wt.% to 0.96 wt.% as a result of the conversion from free lime to calcium ferrite.

  • 17.
    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.

  • 18.
    Li, Jian-Li
    et al.
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Xu, An-Jun
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    he, Dong-feng
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tian, Nai-Yuan
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system2013In: International Journal of Minerals, Metallurgy and Materials, ISSN 1674-4799, E-ISSN 1869-103X, Vol. 20, no 3, p. 253-258Article in journal (Refereed)
    Abstract [en]

    Synthetic slag samples of the CaO-SiO2-MgO-Al2O3-Cr2O3 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250 degrees C with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.

  • 19.
    Liu, G.Q.
    et al.
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Zhang, X.L.
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Qu, D.R.
    SINOPEC Research Institute of Safety Engineering.
    Zheng, Y.G.
    State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences.
    Jiang, S.L.
    State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences.
    Jiang, X.
    SINOPEC Research Institute of Safety Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Han, F.L.
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Naphthenic acid corrosion characteristic and corrosion product film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum gas oil2016In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 51, no 6, p. 445-454Article in journal (Refereed)
    Abstract [en]

    Although naphthenic acid corrosion (NAC) has been studied for many years, the mechanism of NAC is not fully understood. The objective of this paper is to study high-temperature NAC in secondary vacuum gas oil of an industrial crude oil vacuum distillation tower. A high-temperature autoclave was applied to conduct high-temperature corrosion test to investigate NAC behaviour of carbon steel and Cr5Mo low alloy steel at different sulphur contents and total acid numbers (TAN). The result shows that the corrosion rate of carbon steel and low alloy steel is high at low TAN and high TAN while it keeps at a low value at medium TAN. Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr7S8 film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN which are strange and different from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward.

  • 20.
    Lui, Gui Qun
    et al.
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Liang, Jiang
    School of Material Science and Engineering, Beifang University for Nationalities Yinchuan, Ningxia.
    Xue, Peng
    Department of Ferrous Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing.
    Zhang, Xiao Li
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Han, Feng Lan
    School of Materials Science & Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Sintering characteristics of BCSAF cement clinker with added wastes from production of manganese and magnesium metals2017In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 29, no 6, p. 227-235Article in journal (Refereed)
    Abstract [en]

    The production of belite-calcium sulfoaluminate-ferrite (BCSAF) cement with the addition of industrial wastes as feedstock has been studied for many years. The preparation of clinkers is essential in cement production, in which all raw materials react with each other to generate key phases in cement under some specified conditions. The objective of this study was to investigate the sintering characteristics of BCSAF cement clinkers. Four BCSAF clinkers with different compositions were examined. High-temperature microscopy, quantitative x-ray powder diffraction analysis and scanning electron microscopy were used to analyse sintering features and phase composition. The results show that the use of wastes from the production of manganese and magnesium metals, which were added to the raw materials to make clinker pellets, can significantly reduce the firing temperature of BCSAF clinker. The firing temperatures of clinkers with added wastes were below 1300°C, much lower than the temperature used for conventional Portland cement (1450°C). The ferrite phase was always found to inter-grow with the C4A3S¯">C 4 A 3 S ¯  C4A3S¯ phase or C2AS phase, just like the interstitial phase. The ferrite phase acted as a solid solution during cement sintering. A small quantity of iron oxide can make the clinker more porous, leading to energy savings in subsequent grinding processes.

  • 21.
    Ma, Ping
    et al.
    Luleå University of Technology.
    Lindblom, Bo
    Luleå University of Technology.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Experimental studies on treatment and recycling of stainless steel residues using the smelting reduction furnace method2005In: Sustainable developments in metals processing: proceedings of the John Floyd International Symposium, Melbourne, Vic., July 3-6, 2005 / [ed] Madhu Nilmani; William John Rankin, Melbourne: The Australian Institute of Mining and Metallurgy , 2005, p. 223-235Conference paper (Refereed)
  • 22. Menad, Nourreddine
    et al.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Thermal reduction of EAF dusts by using BF dusts as a reducing agent2005In: Proceedings of the REWAS '04: Global Symposium on Recycling, Waste Treatment and Clean Technology held in Madrid, Spain, September 26 - 29, 2004 : [also served as the TMS 2004 Fall Extraction and Process Metallurgy Meeting], Minerals, Metals & Materials Society, 2005, p. 2751-2760Conference paper (Refereed)
    Abstract [en]

    The investigation of the thermal reduction of Electric Arc Furnace Dust (EAFD) by Blast Furnace Dust (BFD) was carried out using simultaneous thermogravimetric analysis (STA) coupled with Quadrupole Mass Spectroscopy (QMS). Chemical and mineralogical analyses were also employed. EAF Dust, which mainly consists of higher zinc compounds as Zincite (ZnO) and Franklinite (ZnFe2O4), is produced in electric arc furnaces (EAF). Blast furnace dust (BFD) with a carbon-iron rich, flue by-product released in the iron-making process was used as a reductant agent. Both raw materials were examined individually in different controlled atmospheres of Ar, air and CO 2 between 20° and 1400°C. Different parameters such as effect of reaction atmosphere, temperature and quantity of the reductant agent were explored. The products of reaction were examined by x-ray diffraction (XRD) as well as the gaseous substances evolved in the reactions. The results indicated that, at 1300°C in Ar atmosphere, a complete reduction of oxide compounds contained in both samples is achieved with a 33 % reductant mixture

  • 23.
    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.

  • 24.
    Mostaghel, Sina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Recycling of cathode ray tube in metallurgical processes: Influence on environmental properties of the slag2011In: Global Journal of Environmental Science and Technology, ISSN 2248-9630, Vol. 1, no Artikelnr: 19Article in journal (Refereed)
    Abstract [en]

    A potential recycling rout for the end-of-life cathode ray tubes (CRT) is its application as a fluxing material in lead and copper smelting processes. Therefore, a thorough study on possible effects of the additional CRT on products and by-products of the metallurgical operation is required. In this paper, influences of CRT addition on mineralogy and leaching behaviour of a fayalite-type slag from a Swedish copper producer are investigated. Mixtures of slag/CRT, in different fractions, were prepared and re-melted in a Tamman furnace. Materials characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and standard leaching tests were done for all samples. Results depict that the main crystalline phase of the slag does not change due to CRT addition. By 10 wt-% CRT addition, leachability of major elements decreases; whereas, that of some minor elements increases. With 35 wt-% CRT addition, leaching of some environmentally detrimental elements make the material unacceptable for construction purposes according to the regulations.

  • 25.
    Sandström, Åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Qixing
    Menad, Nourreddine
    Lindblom, B
    EAF dust processing with a combination of hydro- and pyrometallurgical techniques2003In: EPD Congress 2003: proceedings of sessions and symposia sponsored by the Extraction and Processing Division (EPD) of TMS (The Minerals, Metals & Materials Society) held during the 2003 TMS annual meeting in San Diego, California, March 2 - 6, 2003 / [ed] Mark E. Schlesinger, Minerals, Metals & Materials Society, 2003, Vol. Warrendale, Pa, p. 377-388Conference paper (Refereed)
    Abstract [en]

    An EAF dust sample generated in a scrap based steel mill was treated by a combination of hydro- and pyrometallurgical techniques. The EAF dust contained mainly ferritic spinels forming solid solution phases according to the general chemical formula (MnxZnyFe1-x-y)Fe2O4 and other oxide phases such as ZnO, CaO and Ca2Fe2O5. The EAF dust was first treated by hydrochloric acid leaching at pH = 3 which dissolved 63% of the zinc. The pyrometallurgical treatment of the leaching residue was studied using an induction heating system to simulate some important operations of EAF smelting of the residue in combination with steelmaking. The leaching residue was mixed with carbon powder to obtain a mixture with 52.1% ZnFe2O4 and 17.8% carbon. The mixture, scrap, and slag former were charged together in a crucible and heated to attain a melt temperature around 1650DGC. The effects of different amounts of mixture on the zinc balance and iron recovery were examined. Based on the test results, suggestions are made for the EAF recycling procedure of the leaching residue.

  • 26. 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)
  • 27. 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.

  • 28.
    Wang, Feng
    et al.
    Central Iron and Steel Research Institute, Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Xu, Anjun
    University of Science and Technology, Beijing.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of Mn oxides on chemical state and leaching of chromium in EAF slag2013In: Metalugia International, ISSN 1582-2214, Vol. 18, no 8Article in journal (Refereed)
    Abstract [en]

    In order to study the influences of Mn oxides on Cr in Electronic Arc Furnace (EAF) slag produced in a stainless steelmaking plant. To simulate EAF slags, two synthetic slags (slag A and slag B) were prepared through melting the two groups of reagent-grade compounds, respectively. The phase composition of samples was characterized by means of XRD. In addition, the slags with different particle size and some mixture were leached following Europe standard procedure. There was only one main compound MgCr2O4 found in spinel phase in slag A. While there were two compounds MgCr2O4 and Mn2AlO4 co-existed in spinel phase in slag B, in which Mn and Cr occupy the octahehral sites. For leaching tests, the influence of different factors, such as slag types, slag particles size, mixed manganese oxides, were studied in detail. The leaching result shows that MnO2 melted in slag is the most important factor for improving Cr leaching. But Mn oxides mixed in Mn-free slag have a little influence on Cr leaching.

  • 29.
    Wu, Laner
    et al.
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Han, Fenglan
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Guo, Shengwei
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Fluoride emissions from Pidgeon process for magnesium production2012Conference paper (Refereed)
    Abstract [en]

    Primary magnesium is nowadays produced in China via Pidgeon process. An important reaction in the process is silicothermic reduction of MgO from dolime near 1200ºC under pressure of 2-10 Pa to generate Mg vapor. Fluorite, ranging 2-3% (mass fraction), is usually mixed with the raw materials to catalyze the reaction. Under the process conditions, CaF2 in the fluorite may form some fluorides to vaporize, thus polluting air. The fluorides remaining in the solid process waste, the Mg slag, may be dissolved to cause water pollution.In the present study, experiments were performed by using retorts of pilot scale in a maffle furnace to simulate the Pidgeon process for primary Mg production. The test materials, briquettes of 5.6-10 kg made of dolime, ferrosilicon and fluorite, were charged in the retorts and heated under conditions similar to the industry operation. Fluoride minerals in the Mg slag from the simulation experiments were identified by XRD and SEM-EDS techniques. Quantities of some F-containing phases formed in the process under equilibrium condition were calculated by FactSage 6.2 thermodynamic package. Fluoride distributions were determined to establish an F-balance among the input and output materials. Besides, slag samples from a magnesium plant were also characterized, including leaching test according to EN 12457-2.Based on these results, fluoride impacts on the environment were evaluated and discussed. Suggestions were also presented to minimize the environmental impacts from primary Mg production using the Pidgeon process.

  • 30.
    Wu, Laner
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Han, FengLan
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Du, Chun
    School of Chemical Engineering, Beifang University of Nationalities, Yinchuan.
    Dusting control of magnesium slag produced by Pidgeon process2013In: Powders and grains 2013: proceedings of the 7th International Conference on Micromechanics of Granular Media : Sydney, Australia: 8-12 July 2013 / [ed] Aibing Yu, Melville, NY: American Institute of Physics (AIP), 2013, p. 1282-1285Conference paper (Refereed)
    Abstract [en]

    Magnesium production by Pidgeon process has been developed very fast in China since 1990's. The waste slag from magnesium production has attracted broad attention because the huge amounts of the slag. For each ton of magnesium produced, there will be 6-8 tons of the slag generated. A big part of the Mg slag exists as fine dust with particle size of D95 < 0.1mm, which may pollute air, soil and water surrounding the Mg industry. The fine particles are generated by phase transformations of dicalcium silicate C2S (2CaOṡSiO 2) during the slag cooling. There is a volume expansion of more than 10% with the transformation of β-C2S to γ-C2S phase, causing a disintegration or dusting of the Mg slag. In the present study, several chemical stabilizers were used to treat the dusting Mg slag at 1200°C, including borates, phosphates and rare earth oxides, in order to obtain volume stable slag aggregates for environmental protection and recycling of the Mg slag. The volume expanding rates of the samples were measured. XRD and SEM studies were carried out to confirm effects of the stabilizers. The results show that all of the stabilizers were effective for the stabilization of Mg slag. Some differences between the stabilizers were also described and discussed

  • 31.
    Wu, L.N.
    et al.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Han, F.L.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Du, C.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Xu, A.J.
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing.
    Li, J.L.
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing.
    Fluorine vaporization and leaching from Mg slag treated at different conditions2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 753-755, p. 88-94Article in journal (Refereed)
    Abstract [en]

    Both treatments and leaching tests of an Mg slag sample containing F of 2.15% from an Mg factory in northwest China were conducted in the present study, focusing on problems of F pollutions. By treating at 1000-1200°C in a muffle furnace, F leaching was decreased to a minimum level of 0.49-2.85 mg/l from the Mg slag with an original F leaching of 13.9 mg/l. The F leaching values increased to 4.83-95.5 mg/l, while treating the slag samples in a vacuum furnace. The treatments of Mg slag may thus be carried out in oxidizing atmosphere and under 1200°C to minimize fluorine pollutions and to improve environmental performances of the Pidgeon process.

  • 32.
    Xu, An.Jun
    et al.
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gustafsson, Börje
    Uddeholms AB, System Control & Raw Materials.
    Wang, Feng
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Li, Jian-li
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of EAF dust by smelting in the electric arc furnace and its influences on the EAF operation and dust generation2010In: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 17, no Suppl. 2, p. 132-141Article in journal (Refereed)
    Abstract [en]

    The 2(nd) campaign for recycling electric arc furnace dust (EAFD) has been carried out at Uddeholms AB (early as Uddeholm Tooling AB). Studies examining the effects of EAFD smelting on parameters related to EAF products, energy consumption and EAFD generation have been performed jointly by Uddeholms AB and MiMeR, Minerals and Metals Recycling Research Center, at Lulea University of Technology. 114 tonnes of EAFD were smelted in 121 EAF heats during the campaign. Dust samples were taken isokinetically from the exhaust gas system during the charger processing. Data of Zn contents in the dust samples were combined with other results to examine the influence of EAF operating conditions and EAFD recycling on Zn evaporation. Via EAFD recycling, Zn content in dust increased from 21.5% to 29.7% and the quantity of dust decreased by more than 40%. There were hardly any negative impact noted during the campaign on the furnace energy consumption and properties of steel and slag tapped from the EAF, while the recycled EAFD was amounted to around 2% of the steel weight

  • 33.
    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.

  • 34.
    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
    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. School of Materials Science and Engineering, Beifang University of Nationalities, Yinchuan, Ningxia.
    Formation of MgFe2O4 and recycling of iron from modified BOF slag by magnetic separation2017In: Kang T'Ieh / Iron and Steel, ISSN 0449-749X, Vol. 52, no 7, p. 104-110Article in journal (Refereed)
    Abstract [en]

    Recycling of iron oxide from BOF slagshas always been a difficult issue in metallurgy. The core of this study was transforming the iron oxide into ferromagnetic phase MgFe2O4 by modifying industrial BOF slag appropriately first, and then recycling the iron resources by magnetic separation. The effect of basicity and calcination temperature on the formation of MgFe2O4 in synthetic BOF slags was investigated first, and then the industrial BOF slag was modified. Various experiments and analyses such as XRD, SEM-EDS, Factsage thermodynamic simulation and chemical analyses were conducted.The results show that the optimal basicity was 2, and the optimal calcination temperatures were 1 250 and 1 300℃. Moreover, MgFe2O4 was formed in modified BOF slag by mixing the industrial BOF slag with 6% SiO2 first, and then cooling the modified BOF slag from 1 400 to 1 270℃ at a rate of 1℃/min. After magnetic separation, the total Fe content in magnetic slag increased by 15.80%, to 37.00%, compared with that in the industrial BOF slag. This is better than the direct magnetic separation of iron oxide without any treatment

  • 35.
    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.

  • 36.
    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.

  • 37.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Erosion of refractory by gas injection1990Licentiate thesis, comprehensive summary (Other academic)
  • 38.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The mechanical wear of tuyere refractory and stirring plugs in BOF steelmaking1996Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Water modelling investigations of pressure change at tuyere tip or back attack and wear of H3B03 disks, as well as high temperature modelling wear tests of BOF refractory using single- or double-tuyere and Ar or N2 gas, have been carried out to study mechanisms for mechanical wear of the refractory for BOF stirring tuyeres and plugs. A new nominal Mach number, M*', was defined and adopted as the criterion for correlating test data. Both the back attack frequency and the Wr, wear rate of H3B03 disks, increase with M*' at M*'<1, reach the maximum near M*'=1 and start to decrease after M*'>1. The wear rate, Wr, of MgO-C bricks tested using steel at 1550°C depends strongly on tuyere characters and increases with M*' until M*'=l, similar to the trends for the back attack and disk Wr. Another brick wear parameter, the radius of deep wear area, RDA, displays a behaviour similar to that of the Wr. The estimated refractory wear rate, Wr*, at M*'<_1 can be related to mM*', the defined nominal momentum rate from tuyere gas injection. The RDA measured from single-tuyere tests can be used to estimate influences of tuyere interaction on the refractory wear rate. When the DTC, the distance between tuyeres for a double-tuyere test, is less than twice the RDA, values of Wr are increased. The refractory wear rate will no be influenced with DTC>2RDA. Tuyere gas flowrate can also be reduced to diminish the interaction. Equations are derived, based on proposed bubble expansion wear mechanism, to compute values of estimated RDA, as well as RSA (Radius of Shear wear Area), at M*'<_1 which can be used to eliminate detrimental effects of tuyere interaction and for the plug design. The M*' values for tuyeres should be either less than 0.5 or greater than 1.5 and values of mM*' should be low to reduce the refractory wear for the stirring tuyeres and plugs in BOF steelmaking. A smaller tuyere inner diameter sets the maximum wear parameters to a lower level and can be chosen to decrease the wear, without decreasing the gas flowrate.

  • 39.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Effects of bubble expansion on wear of refractory for BOF stirring plugs embedding tuyeres1997In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 68, no 3, p. 107-114Article in journal (Refereed)
    Abstract [en]

    Single tuyere wear tests of MgO-C and burnt magnesia bricks were performed to study relations between tuyere characteristics and refractory wear parameters, with emphasis on the wear zone geometry. Either Ar or N2 was used as injected gas and the test temperature for liquid metal was 1400, 1550 and 1700 °C. A bubble expansion wear mechanism was proposed for the mechanical wear of tuyere refractory by comparison of bubble radii and the wear zone geometry of refractory bricks and H3BO3 disks. Equations are derived to predict the deep and shear wear zone radii and the refractory wear rate at values of the nominal Mach number up to one. These equations can be used for an optimum design of single- and multiple-tuyere plugs for combined blowing BOF, as well as for optimization of gas stirring operation to reduce the wear of MgO-C refractory around the tuyere and for the plugs.

  • 40. Yang, Qixing
    et al.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The wear of converter stirring plugs and the tuyere gas injection: a study by high temperature modelling1995In: Scaninject VII: 7th International Conference on Refining Processes, Luleå, Sweden, June 7-8, 1995, MEFOS , 1995, Vol. II, p. 257-282Conference paper (Refereed)
    Abstract [en]

    To obtain more information on wear mechanisms of stirring plugs for oxygen converters, the present authors carried out wear tests of MgO-C bricks at 1550 deg C for approx6 h. Tubular tuyeres were used to inject argon gas into liquid metal contained in crucibles. The wear examinations show that mechanical stresses aided by thermal and chemcial stresses are mainly responsible for the brick wear which result in two wear patterns on brick surfaces: the deep wear or back-attack wear and the shear wear. A new criterion, M exp *' , is defined by the ratio of the injected gas mass flowrate, m, to the critical flowrate, m exp * . The M exp *' better characterises the properties of gas-liuqid systems and relates the high wear of the bricks directly to condition changes for gas injection at/near tuyere outlet. The brick wear rates, W sub r , were shown to increase with M exp *' up to a M exp *' value near to one and become constant or decreasing as the M exp *' -values are further increased. Based on results from the present study, tuyeres with i.d. < =2 mm should be operated with M exp *' -values ranging from 0.15-0.45 in order to reduce the wear of plug refractory and to achieve optimum plug operations

  • 41.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    The wear of converter stirring plugs and the tuyere gas injection: a study by high-temperature modelling1995In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 24, no 5-6, p. 242-254Article in journal (Refereed)
    Abstract [en]

    To obtain more information on wear mechanisms of stirring plugs for oxygen converters, the present authors carried out wear tests of MgO-C bricks at 1550°C for about 6 h. Tubular tuyeres were used to inject Ar gas into liquid metal contained in crucibles. The wear examinations show that mechanical stresses aided by thermal and chemical stresses are mainly responsible for the brick wear which result in two wear patterns on brick surfaces: the deep wear or back-attack wear and the shear wear. A new criterion, M* prime , is defined by the ratio of the injected gas mass flowrate, m, to the critical flowrate, m*. The M* prime better characterises the properties of gas-liquid systems and relates the high wear of the bricks directly to condition changes for gas injection at/near tuyere outlet. The brick wear rates, Wr, were shown to increase with M* prime up to a M* prime value near to unity, and become constant or decreasing as the M* prime -values are further increased. Based on results from the present study, tuyeres with i.d. <=2 mm should be operated with M* prime -values ranging from 0.15 to 0.45 in order to reduce the wear of plug refractory and to achieve optimum plug operations

  • 42. Yang, Qixing
    et al.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Carlsson, Göran
    Wear of MgO-C refractory for the BOF stirring plug with multiple tuyeres and the tuyere interaction1996In: 79th Steelmaking Conference proceedings: Pittsburgh meeting, March 24 - 27, 1996, Pittsburgh, Pa: Iron and Steel Society , 1996, p. 439-450Conference paper (Refereed)
    Abstract [en]

    Wearing effects of tuyere interaction on MgO-C refractory for the BOF stirring plug with multiple tuyeres have been studied by performing single-tuyere and double-tuyere wear tests using molten steel of 1550 °C and Ar gas. Two tuyeres were set in the refractory with different distance between their centres for the double-tuyere wear tests to simulate service conditions for the multiple-tuyere plugs. The results show that the wear is severe with a tuyere distance of 12 mm and 10 Nl/min Ar flowrate for each tuyere due to an overlap of the high wear zone around the tuyeres. The wear is reduced to the level of wear for the single tuyere when the tuyere distance is increased to 24 mm or more. With a tuyere distance less than 50 mm, an overlap of the shear zone for the tuyeres occurs giving an elliptic shear wear zone around tuyeres. With a distance of 50 mm for the tuyeres, the interaction effects on the refractory wear disappear. Based on test results and the bubble expansion wear mechanism, methods for estimating, reducing and eliminating mechanical wearing effects of tuyere interaction are discussed and suggested

  • 43. 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.

  • 44.
    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.

  • 45.
    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

  • 46.
    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.

  • 47.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Engström, Fredrik
    Tossavainen, Mia
    He, Mingzhao
    Wang, Zheng
    Luleå tekniska universitet.
    AOD slag treatments to recover metal and to prevent slag dusting2005In: 7th Nordic-Japan Symposium on Science and Technology of Process Metallurgy, 2005, p. 14-Conference paper (Refereed)
  • 48.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gustafsson, Börge
    Uddeholm Tooling AB.
    Upgrading of EAF dust by smelting in the electric arc furnace at Uddeholm Tooling AB2002In: TMS Fall 2002 Extraction and Processing Division Meeting on Recycling and Waste Treatment in Mineral and Metal Processing: Technical and Economic Aspects / [ed] Bo Björkman; Caisa Samuelsson; Jan-Olov Wikström, Luleå: MEFOS , 2002, Vol. 2, p. 231-240Conference paper (Refereed)
  • 49.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gustafsson, Börje
    Uddeholm Tooling, Hagfors.
    Studies on dust recycling in the electric arc furnace at Uddeholm Tooling AB2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 3, p. 147-156Article in journal (Refereed)
    Abstract [en]

    The electric arc furnace (EAF) generates dust containing about 21% Zn during primary steelmaking at Uddeholm Tooling AB. Research work on upgrading of the dust has been carried out jointly by Uddeholm Tooling AB and MiMeR, Minerals and Metals Recycling Research Centre, at Luleå University of Technology. The work included laboratory studies and plant trials. The laboratory studies, with 6 dust smelting tests at temperatures around 1650°C, demonstrated that the smelting had no negative effects on qualities of the steel and slag. It was also shown that both carbon and silicon could be used to reduce the oxides in the dust, leading to high metal recoveries. Based on the study results, plant trials were performed at Uddeholm Tooling AB. The trials consisted of 100 EAF heats, recycling dust at a rate of 925 kg/heat. No negative impact has been found on the furnace products and production. The Zn content of the obtained dust increased by 11% and the weight of the generated dust decreased by 42%. The material costs for the dust recycling during the trials were rather low, $0.4 (4-5 SEK)/tonne steel. Some of the test results are interpreted by virtue of mass and energy balances of the dust smelting calculated using the computer software "Chemsage." By utilizing results from the tests and calculations, the energy consumption for dust smelting was estimated.

  • 50.
    Yang, Qixing
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gustavsson, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effects of gas jet instability on refractory wear: a study by high-speed photography1992In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 21, no 1, p. 15-26Article in journal (Refereed)
    Abstract [en]

    To study influences of gas jet instability on tuyere refractory wear, gas injection was performed in an air-water system with a tuyere of 2 mm inner diameter. High-speed photography was used, with a framing rate of 8000 pictures per second, to film the tip region of a free and a half free tuyere. Characteristics of the cavity formed as a result of the jet instability were measured from the films, and the results were used in equations of bubble dynamics to calculate the pressure generated by the cavity motion. The film sequences show that as a result of the distortion of the gas-liquid interface, a throat in the gas jet is formed about 1.5D (tuyere i.d.) downstream of the tuyere tip. Radially moving gas starts to form an expanding cavity. The radius of the throat increases as it is pushed forward by the cavity expansion. With its radius reaching the maximum, the cavity stops growing. When the cavity collapses, bubble swarms are generated in the region near the tuyere. The cavity expands to 2D-4D (tuyere i.d.) within 1-15 ms. The maximum velocity of the expansion is about 10 m/s and acceleration ranges from 20 to 80 m/s2. The pressure calculated by using the cavity expansion data is in good agreement with the pressure measured at back-attack, which is around one half of the absolute pressure for the gas injection. This implies that the back-attack and cavity expansion are the same phenomenon. Passing the transition point of flow regimes the pressure increases very slowly as the injection rate increases. Occassionally, the cavity does not collapse immediately and it contracts after reaching the maximum radius. The cavity contraction generally takes longer than the expansion, with a velocity of about 2 m/s. The pressure reduction from the contraction is less than 0.1 bar which can not cause the formation of vapour bubbles in the liquid. By the cavity expansion, a liquid flow is set up which deforms and disintegrates gas bubbles nearby. At the moment of disintegration, liquid penetrates the concave side of the deformed bubble. The liquid flow may lead to an impact pressure of 30-90 bar in water and 210-630 bar in liquid steel. This pressure may cause refractory erosion with a pattern similar to that previously observed on H3BO3 disk surface. Besides the pitting erosion of the tuyere refractory, the influences of the jet instability on other factors of the refractory wear are also discussed.

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