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  • 1.
    Ge, Xinlei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jin, S.
    Zhang, M.
    Wang, X.
    Seetharaman, Surya
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    SYNTHESIS OF CHROMIUM AND FERROCHROMIUM ALLOY IN MOLTEN SALTS BY THE ELECTRO-REDUCTION METHOD2015In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 51, no 2, p. 185-191Article in journal (Refereed)
    Abstract [en]

    In this work, we successfully applied the Fray-Farthing-Chen Cambridge electro-reduction process on the preparation of chromium from chromium oxide, and for the first time, the synthesis of ferrochromium alloy from chromium oxide and iron oxide mixture and the chromite ore in molten calcium chloride. The present work systematically investigated the influences of sintered temperature of the solid precursor, electrochemical potential, electrolysis temperature and time on the products by using a set of advanced characterization techniques, including XRD and SEM/EDS analyses. In particular, our results show that this process is energy-friendly and technically-feasible for the direct extraction of ferrochromium alloy from chromite ore. Our findings thus provide useful insights for designing a novel green process to produce ferrochromium alloy from low-grade chromite ore or stainless steel slag.

  • 2.
    Guntoro, Pratama Istiadi
    et al.
    Aalto University, School of Chemical Engineering.
    Jokilaakso, Ari
    Aalto University, School of Chemical Engineering.
    Hellstén, Niko
    Aalto University, School of Chemical Engineering.
    Taskinen, Pekka
    Aalto University, School of Chemical Engineering.
    Copper matte - slag reaction sequences and separation processes in matte smelting2018In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 54, no 3, p. 301-311Article in journal (Refereed)
    Abstract [en]

    While particle combustion and chalcopyrite oxidation in suspension smelting is well understood, few studies are available regarding the melt-melt reactions and the separation between copper matte and slag in matte smelting. In the present work, experimental investigations in air and argon atmosphere were conducted using a mixture of synthetic slag and chalcopyrite concentrate. The sequential reaction and separation processes occurring in matte smelting are outlined. Possible limiting factors in the overall process are also proposed. The result of the present work forms an important foundation for future work in the kinetic rate formulation of molten phase reactions between copper matte and slag in matte smelting.

  • 3.
    Hu, X.
    et al.
    KTH.
    Wang, H.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Direct chromium alloying by chromite ore with the presence of metallic iron2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 207-215Article in journal (Refereed)
    Abstract [en]

    Direct chromium alloying by chromite ore in EAF operation is a promising process in stainless steel production, which has the advantage of resource-saving, energy-saving, and environment-friendly. In the present investigation, iron, carbon, and chromite ore mixture (Fe+C+FeCr2O4) were chosen as the precursor for direct chromium alloying. Thermogravimetric Analysis (TGA) experiments were carried out to investigate the effect of iron content on the reduction kinetics, and the results show that the presence of metallic iron in the precursor will increase the reduction rate of chromite. Up-scaling experiments (100 g and 500 g scale) have been carried out in the induction furnace to further test the effectiveness of using industrial chromite ore for direct chromium alloying. The induction furnace tests confirmed the necessity of adjusting composition of the slags to ensure high yield of chromium in the final products; and chromium yield can reach 90%.

  • 4.
    Hu, Xianfeng
    et al.
    Royal Institute of Technology (KTH), Stockholm.
    Wang, Haijuan
    Division of Materials Process Science, Royal Institute of Technology (KTH), Royal Institute of Technology.
    Teng, Lidong
    Department of Materials Science and Engineering, Royal Institute of Technology, Division of Materials Process Science, Royal Institute of Technology (KTH).
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology, Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Direct chromium alloying by chromite ore with the presence of metallic iron2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 207-215Article in journal (Refereed)
    Abstract [en]

    Direct chromium alloying by chromite ore in EAF operation is a promising process in stainless steel production, which has the advantage of resource-saving, energy-saving, and environment-friendly. In the present investigation, iron, carbon, and chromite ore mixture (Fe+C+FeCr2O4) were chosen as the precursor for direct chromium alloying. Thermogravimetric Analysis (TGA) experiments were carried out to investigate the effect of iron content on the reduction kinetics, and the results show that the presence of metallic iron in the precursor will increase the reduction rate of chromite. Up-scaling experiments (100 g and 500 g scale) have been carried out in the induction furnace to further test the effectiveness of using industrial chromite ore for direct chromium alloying. The induction furnace tests confirmed the necessity of adjusting composition of the slags to ensure high yield of chromium in the final products; and chromium yield can reach 90%.

  • 5. Shatokha, V.
    et al.
    Semykina, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Nakano, J.
    Sridhar, S.
    Seetharaman, Seetharaman
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A study on transformation of some transition metal oxides in molten steelmaking slag to magnetically susceptible compounds2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 169-174Article in journal (Refereed)
    Abstract [en]

    Sustainable development of steelmaking requires solving a number of environmental problems. Economically feasible and environmentally friendly recycling of slag wastes is of special concern. Research of the team representing National Metallurgical Academy of Ukraine, Royal Institute of Technology, Carnegie Mellon University and URS Corp revealed a possibility of the controlled phase transformations in the liquid silicate melts followed by formation of the magnetically susceptible compounds. This approach enables selective recovery of metal values from slag. In this paper, the results obtained and further research directions are discussed. A possibility to exploit physical properties of the transition metals, typical for the metallurgical slags (such as Fe, Mn, V and others), and corresponding specific properties of their compounds, such as non-stoichiometry, mixed valency, pseudomorphosis, thermodynamic stability etc, in production of value-added materials from slag wastes is discussed. The results of the studies of thermodynamics and kinetics of oxidation in slags followed by phase transformation with binary, ternary and complex oxides under various physicochemical conditions are discussed in the view of their application for production of the materials with predefined physical properties. Peculiarities of precipitation in slags with various basicities are analysed and demonstrate capacity of the proposed approach in the production of the material with a given structure and size - for example, nano-sized crystals with structure of spinel. The approaches towards industrial realization of the developed method are also discussed.

  • 6. Wang, H.
    et al.
    Nzott, M. M.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Decarburization of ferrochrome and high alloy steels with optimized gas and slag phases towards improved Cr retention2013In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 49, no 2, p. 175-181Article in journal (Refereed)
    Abstract [en]

    Chromium is a high value metal and the retention of the same during the refining of high carbon ferrochrome as well as high alloy steel has significant economic and environmental impacts. The loss of chromium during the decarburization is generally minimized using argon-oxygen mixtures thereby reducing the oxygen partial pressure (PO2) of the oxidant gas. In the current study, experiments were carried out in an induction furnace and CO2 was introduced with the view to partly reduce PO2 and partly as an oxidizer. During these experiments, the decarburization of molten Cr-alloy was conducted using pure O2, pure CO2 or O2+CO2 mixtures. The results demonstrated that the Cr loss can be minimized under CO2 introduction. The kinetic analysis showed that the mass transfer is effective due to the production of 2CO gas molecules from one CO2 molecule during the reaction which will improve the stirring of the bath. Besides, CO2 reacts with carbon in melt is an endothermic reaction, introduction of CO2 could be a cooler during the refining process, hence the temperature could be controlled by controlling the diluting gas amount, in this case, the over heat of bath refractory could be prevented and the lifetime of refractory could be extended.

  • 7. Wang, H.
    et al.
    Yu, H.
    Teng, L.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Evaluation on material and heat balance of EAF processes with introduction of CO22016In: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 52, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The advantages of using CO2 for the decarburization of high alloy steels have been recognized from environmental and economic view points. The present paper presents the heat and materials balances in the decarburization process with the introduction of CO2 as a diluting gas in Electric Arc Furnace (EAF) process for steel production. The aim is to optimize the amount of CO2 and the materials requirements, which includes the addition of scrap, hot metal and coolant. These estimations are also important to control the bath temperature, thereby prolong the lifetime of the refractory lining of the furnace. The present calculations enable an optimization of the CO2:O-2 ratio and materials input in the decarburization of carbon steel melts. Another important extension of the work is the possibility to enhance the addition of hot metal during steel making process. The present results show that addition of up to 20% hot metal is likely to the energy loss due to the introduction of 50% CO2 for a 110 tons EAF resulting in the saving of electric energy.

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