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  • 1. Abhale, P.B.
    et al.
    Guha, M
    Nurni, Viswanathan
    Ballal, N.B.
    Prediction of gas flow through layered burden prolies in blast furnace2006Konferensbidrag (Refereegranskat)
  • 2. Abhale, P.B.
    et al.
    Guha, M.
    Ramna, M.V.
    Nurni, Viswanathan
    Ballal, N.B.
    Prediction of cohesive zone in a blast furnace using wall pressure tap data: modelling appproach2008Konferensbidrag (Refereegranskat)
  • 3. Abhale, P.B.
    et al.
    Guna, M.
    Ramna, R.V.
    Nurni, Viswanathan
    Investigation of computational aspects in simulation of gas flow in blast furnace2009Konferensbidrag (Refereegranskat)
  • 4. Abhale, P.B.
    et al.
    Nurni, Viswanathan
    Ballal, N.B.
    Blast furnace modelling2005Konferensbidrag (Refereegranskat)
  • 5.
    Abhale, P.B.
    et al.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Nurni, Viswanathan
    Ballal, N.B.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Efficient simulation of gas flow in blast furnace2009Ingår i: Computers, Materials & Continua, ISSN 1546-2218, Vol. 10, nr 2, s. 195-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simulation of gas flow in a multilayered non-isothermal packed bed is useful for blast furnace operators in deciding appropriate charging strategy. While using an anisotropic form of Ergun equation to simulate gas flow through such systems, a new solution methodology for non-isothermal gas with varying density flowing through a layered burden has been proposed. This involves handling non-linearity due to gas density variation with pressure and temperature by solving for the square of pressure instead of pressure directly and handling the non-linearity due to vertical bar nu vertical bar term in the Ergun equation by solving linearized form of Ergun equation and updating vertical bar nu vertical bar iteratively. The proposed scheme is capable of predicting the effect of layer structure on gas flow with economy in number of grid points as well as computation time

  • 6. Abhale, P.B.
    et al.
    Nurni, Viswanathan
    Ballal, N.B.
    Efficient simulation of gas flow in blast furnace2008Konferensbidrag (Refereegranskat)
  • 7. Abhale, P.B.
    et al.
    Yadav, V.K.
    Nurni, Viswanathan
    Ballal, N.B.
    Investigation of mal-distribution in blast furnace aerodynamics using a three dimensional simulation model2010Konferensbidrag (Refereegranskat)
  • 8.
    Abhale, Prakash Bansi
    et al.
    Global R and D, ArcelorMittal, Kolkatta.
    Yadav, Vishal Kumar
    Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit, Leuven.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ballal, Bharath Nidambur
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Efficient computation of gas flow in blast furnace in 3-D2012Ingår i: 6th Int. Congress on the Science and Technology of Ironmaking 2012, ICSTI 2012: Including Proceedings from the 42nd Ironmaking and Raw Materials Seminar, and the 13th Brazilian Symp. on Iron Ore, 2012, Vol. 1, s. 722-732Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blast furnace continues to occupy prominent place among iron making technologies as it accounts for more than 90% of the hot metal produced in the world. In India, as a part of initiative from Ministry of Steel, efforts are being made to develop offline as well as online models with an aim to improve blast furnace performance. As a part of this effort, offline comprehensive models simulating the internal state of an operating blast furnace are being developed. Such comprehensive models involve systematic integration of various sub-models for gas flow, solid flow, reaction kinetics, enthalpy balance etc. Unlike in many other systems, these sub-processes are highly interlinked in blast furnace and hence call for large number of iteration among the sub-models which ultimately results in significant computation time. Our efforts in integration of these sub-models have indicated that the gas flow is one of the important bottle necks in achieving faster computation. This has led to a development of new and efficient computation scheme to simulate the gas flow in 2-D [1]. This new scheme provided efficient way of handling complex burden profile in a blast furnace. This paper presents the extension of this 2-D gas flow model to 3-D. Further, the 3-D model has been used to investigate the asymmetry in gas flow which can arise from blanking the tuyeres, asymmetric fusion or cohesive zone or formation scabs or scaffolds in the furnace behavior

  • 9.
    Adhikar, Subhra
    et al.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Powai.
    Nurni, Viswanathan
    Dusane, Rajiv Onkar
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Powai.
    Thermodynamic analysis of gas phase chemistry in hot wire chemical vapor deposition of a-Si:H and μc-Si:H2006Ingår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 362, nr 9-20 Spec Iss., s. 928-932Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gas phase reactions amongst filament-generated radicals play a crucial role in growth and properties of films deposited by hot wire chemical vapor deposition (HWCVD) technology. Gas phase species of interest are SiH4, H2, Si, H, SiH3, SiH2 and SiH. Partial pressures of these species for different sets of deposition conditions have been determined from the standard Gibbs free energy data. Equilibrium concentrations of the film forming precursors have been determined. The effect of the various process parameters on the equilibrium concentration of the precursors has been studied. H, Si and SiH are found to be the dominant species in gas phase above a filament temperature of 2300 K. However SiH3 and SiH2 concentration peaks are between 1900 and 2300 K, of the filament temperature

  • 10.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Geasyy, Abdel Hady El
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Nurni, Viswanathan
    Indian Institute of Technology (IIT).
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH, Department of Metallurgy, Royal Institute of Technology, Stockholm, Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Kinetics and mathematical modeling of hydrogen reduction of NiO-WO 3 precursors in fluidized bed reactor2011Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, s. 1383-1391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 11.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Composite pellets: a potential raw material for iron-making2014Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, nr 3, s. 293-306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coke constitutes the major portion of iron-making cost and its production causes severe environmental concerns. In addition, lower energy consumption, lower CO2 emission and waste recycling are driving the Iron and steel making industry to develop “coke free, zero waste or green processes”. In the present article, an overview of possible ways to recognize a reasonable improvement in iron and steel making industry is summarized. The present discussion is focusing on the following approaches: 1. Replacing expensive coke with relatively less expensive alternate fuels having carbon as well as significant amount of hydrogen such as coal, waste plastic and biomass materials.2. Producing agglomerates from cheaper raw materials (secondary resources) as well as improving their performance in BF.3.Making the process towards higher carbon utilization by shifting the wustite equilibrium towards lower CO/CO2 ratio by using high reactive coke or catalytic activated one.4.Recycling the unused CO in the top gas by removing CO2 from the gas stream.Much attention has been paid to carbon composite agglomerates (CCA) as a promising raw material for future iron making. Production, mechanical and chemical suitability, reduction behavior, etc. are being elaborated. In addition, other possible ways to utilize CCA in alternate iron-making process has been explored.

  • 12.
    Ahmed, Hesham
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Isothermal reduction kinetics of self-reducing mixtures2017Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, nr 1, s. 66-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Isothermal reduction of haematite carbon mixtures was investigated at temperatures 750–1100°C under inert atmosphere. Mass loss curves proved the stepwise reduction of haematite to metallic iron. The non-linear feature of haematite to magnetite reduction kinetics was observed and an activation energy of 209 kJ mol−1 was calculated. Irrespective of carbon-bearing material type, reduction rate of magnetite was linear. Activation energy values were calculated to be 293–418 kJ mol−1. Significant increase in the reduction kinetics in the last step (Wustite reduction) was observed and explained by the catalytic effect of freshly formed metallic iron. During the initial stages of wustite reduction, the activation energy values were calculated to be in the range of 251–335 kJ mol−1 for all carbon-bearing materials.

  • 13.
    Ahmed, Hesham
    et al.
    Royal Institute of Technology (KTH), Stockholm.
    Nurni, Viswanathan
    Indian Institute of Technology, Bombay.
    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.
    Dynamic thermal diffusivity measurements: A tool for studying gas-solid reactions2011Ingår i: Diffusion in Solids and Liquids VI: selected, peer reviewed papers from the 6th International Conference on Diffusion in Solids and Liquids : mass transfer, heat transfer, microstructure & properties, nanodiffusion and nanostructured materials : DSL-2010, 5-7 July 2010, Paris, France / [ed] Andreas Öchsner; Graeme E. Murch ; João M.P.Q. Delgado, Durnten-Zurich: Trans Tech Publications Inc., 2011, Vol. 312-315, s. 217-222Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the present work, the thermal diffusivity measurements of uniaxially cold pressed NiWO4 has been carried out. The measurements were performed isothermally at temperatures between 973 and 1273 K under H 2 gas using the laser flash technique. The experimental thermal diffusivity values were found to increase with the reduction progress as well as with increasing temperature. The calculated activation energy was found to be higher than that for chemically controlled reaction. The difference has been attributed to factors like agglomeration of the product as well as sintering of the precursor along with the chemical reaction. In order to sort out the sintering effect on the thermal diffusivity values, complementary experiments have been done on pressed NiWO 4 and Ni-W, produced by the reduction of NiWO 4 at 1123K, under Argon gas. The porosity change and its effect on thermal diffusivity values have been studied.

  • 14.
    Ballal, N.B.
    et al.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Nurni, Viswanathan
    Abhale, P.B.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Blast furnace modeling: gaps and challenges2009Ingår i: International Conference on Advances in the Theory of Ironmaking and Steelmaking (ATIS 2009): December 09 - 11, 2009 / [ed] Govind S Gupta, New Dehli: Allied Publishers Ltd , 2009, s. 162-171Konferensbidrag (Refereegranskat)
  • 15. Bedarkar, S.S.
    et al.
    Nurni, Viswanathan
    Ballal, N.B.
    Experinvestigation of heat transfer in a packed bed of iron ore particles2007Konferensbidrag (Refereegranskat)
  • 16.
    Beskow, Kristina
    et al.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Nurni, Viswanathan
    Jonsson, Lage T.I.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Sichen, Du U.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle2001Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 32, nr 2, s. 319-328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the deoxidation of liquid steel with aluminum wire injection in a gas-stirred ladle was studied by mathematical modeling using a computational fluid dynamics (CFD) approach. This was complemented by an industrial trial study conducted at Uddeholm Tooling AB (Hagfors, Sweden). The results of the industrial trials were found to be in accordance with the results of the model calculation. In order to study the aspect of nucleation of alumina, emphasis was given to the initial period of deoxidation, when aluminum wire was injected into the bath. The concentration distributions of aluminum and oxygen were calculated both by considering and not considering the chemical reaction. Both calculations revealed that the driving force for the nucleation of Al2O3 was very high in the region near the upper surface of the bath and close to the wire injection. The estimated nucleation rate in the vicinity of the aluminum wire injection point was much higher than the recommended value for spontaneously homogeneous nucleation, 103 nuclei/(cm3/s). The results of the model calculation also showed that the alumina nuclei generated at the vicinity of the wire injection point are transported to other regions by the flow.

  • 17.
    Beskow, Kristina
    et al.
    Kungliga tekniska högskolan, KTH.
    Nurni, Viswanathan
    Sicken, Du
    Study of the deoxidation of steel with aluminium wire injection in a gas ladle1999Rapport (Övrigt vetenskapligt)
  • 18.
    Bustnes, J.A.
    et al.
    LKAB, Research & Development, 983 81 Malmberget.
    Nurni, Viswanathan
    Sichen, Du U.
    LKAB, Research & Development, 983 81 Malmberget.
    Seetharaman, Seshadri
    Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Investigation on reduction of CoAI2O4 by hydrogen gas using TGA2000Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 31, nr 3, s. 540-542Artikel i tidskrift (Refereegranskat)
  • 19.
    Bustnes, J.A.
    et al.
    Department of Metallurgy, Royal Institute of Technology, Stockholm.
    Nurni, Viswanathan
    Sicken, Du
    Department of Metallurgy, Royal Institute of Technology, Stockholm.
    Seetharaman, Seshadri
    Department of Metallurgy, Royal Institute of Technology, Stockholm.
    Investigation of the reduction of ZnWO4 by hydrogen gas2000Ingår i: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 91, nr 6, s. 500-503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reduction of zinc tungstate by hydrogen gas was studied using a thermogravimetric method in the temperature range 823 to 1073 K. The experiments were carried out isothermally. A new W to Zn binary phase was found in the samples reduced at 873 K. This discovery is in disagreement with the earlier information on Zn-W phase equilibria that Zn and W do not form alloys. The favorable kinetic conditions would be of help for the formation of this phase. On the other hand, this phase was not observed in the sample reduced at 1073 K. The evaporation of zinc during the reduction was found to play an important role. The apparent activation energy for the reduction of ZnWO4 by hydrogen was evaluated to be 90 kJ/mole using the initial reaction rates

  • 20.
    Chaudhury, Asim
    et al.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Khatirkar, Rajesh K
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Nurni, Viswanathan
    Singal, Vivek
    Corporate R and D and Quality, Crompton Greaves Ltd., Kanjur (East), Mumbai.
    Ingle, A.
    Corporate R and D and Quality, Crompton Greaves Ltd., Kanjur (East), Mumbai.
    Joshi, Shrikant V.
    Corporate R and D and Quality, Crompton Greaves Ltd., Kanjur (East), Mumbai.
    Samajdar, Indradev D.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Low silicon non-grain-oriented electrical steel: Linking magnetic properties with metallurgical factors2007Ingår i: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 313, nr 1, s. 21-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Commercial supply, from several steel manufacturers, of low-silicon non-grain-oriented electrical steel was monitored over a span of several years. A total of 51 samples were selected-selected from many hundreds on the basis of large differences in magnetic properties, but absence of significant variations in chemistry (other than differences in silicon percentage). The selected samples were analyzed for crystallographic texture and for grain size. The data were carefully analyzed to bring out the effects of metallurgical variables, namely silicon %, grain size and crystallographic texture, on the magnetic properties using explicit functional relationships as well as artificial neural network (ANN). Among the explicit relationships, power law relationship appears to offer a best fit between magnetic properties and the metallurgical factors. ANN approach to the relationship, however, brought out predicted values with least error

  • 21.
    Jakobsson, Anders
    et al.
    Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Nurni, Viswanathan
    Sichen, Du U.
    Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Seetharaman, Seshadri
    Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Interfacial phenomena in some slag-metal reactions2000Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 31, nr 5, s. 973-980Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the change of the interfacial tension at the slag-metal interface for sulfur transfer between molten iron, slag, and gas phases was monitored by X-ray sessile drop method in dynamic mode in the temperature range of 1830 to 1891 K. The experiments were carried out with pure iron samples immersed partly or fully in the slag phase. The slag consisted of 30 wt pct CaO, 50 wt pct Al2O3, and 20 wt pct SiO2 (alumina saturated at the experimental temperatures) with additions of FeO. Metal and slag samples contained in alumina crucibles were exposed to a CO-CO2-SO2-Ar gas mixture with defined oxygen and sulfur partial pressures, and the change of the shape of the metal drop was determined as a function of time. The equipment and the technique were calibrated by measurements of the surface tensions of the pure Cu, Ni, and Fe containing two different amounts of dissolved oxygen. A theoretical model was developed to determine the sulfur content of the metal as a function of time on the basis of sulfur diffusion in the slag and metal phases as well as surface tension-induced flow on the metal drop surface. Attempts were made to compute the interfacial tensions on the basis of force balance.

  • 22.
    Jayaram, Vikram
    et al.
    Department of Metallurgy, Indian Institute of Science, Bangalore.
    Nurni, Viswanathan
    Abinandanan, Thennathur Appandairajan
    Department of Metallurgy, Indian Institute of Science, Bangalore.
    Dislocation pile-up model for the yield stress of a composite1999Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 47, nr 5, s. 1635-1643Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A numerical model to simulate yielding in a composite is developed for the transmission of slip across a dissimilar interface through the formation of co-planar dislocation arrays in both phases. A pile-up of dislocations in the soft phase is assumed to nucleate dislocations in the hard phase in which movement is dictated by lattice friction stress. The polycrystalline composite yield stress is calculated by determining the equilibrium positions of the dislocation arrays as a function of the length scales, elastic constants and Burgers vectors in the two phases, with particular reference to melt oxidized Al-Al2O3, in which homophase boundaries are absent, and to the commercially important system Co-WC. The hardness values predicted from this model are in good agreement with experimentally measured values in the above systems. The implications of these results for the design of hard composite microstructures are elucidated.

  • 23.
    Kiamehr, Saeed
    et al.
    Royal Institute of Technology (KTH).
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Seetharaman, Seshadri
    Division of Materials Process Science, KTH-Royal Institute of Technology .
    Changes in Effective Thermal Conductivity During the Carbothermic Reduction of Magnetite Using Graphite2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 3, s. 1502-1513Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of the effective thermal diffusivity changes of systems undergoing reactions where heat transfer plays an important role in the reaction kinetics is essential for process understanding and control. Carbothermic reduction process of magnetite containing composites is a typical example of such systems. The reduction process in this case is highly endothermic and hence, the overall rate of the reaction is greatly influenced by the heat transfer through composite compact. Using Laser-Flash method, the change of effective thermal diffusivity of magnetite-graphite composite pellet was monitored in the dynamic mode over a pre-defined thermal cycle (heating at the rate of 7 K/min to 1423 K (1150 °C), holding the sample for 270 minutes at this temperature and then cooling it down to the room temperature at the same rate as heating). These measurements were supplemented by Thermogravimetric Analysis under comparable experimental conditions as well as quenching tests of the samples in order to combine the impact of various factors such as sample dilatations and changes in apparent density on the progress of the reaction. The present results show that monitoring thermal diffusivity changes during the course of reduction would be a very useful tool in a total understanding of the underlying physicochemical phenomena. At the end, effort is made to estimate the apparent thermal conductivity values based on the measured thermal diffusivity and dilatations.

  • 24.
    Kumar, T K Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Dahlin, Anders
    LKAB.
    Nurni, Viswanathan
    Indian Institute of Technology Bombay .
    Investigating the Oxidation Phenomena of Magnetite Pellet2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Induration of magnetite pellet is a complex physico-chemical process involving oxidation, sintering and the heat transfer phenomena. Often, these phenomena happen simultaneously and influence each other in the induration furnace. It could be because of the highly exothermic nature of oxidation phenomena that can result in significant temperature gradients inside the pellet and sintering might begin much earlier that it is ideally supposed to. This could results in the formation of pellets with heterogeneous phases and crystallographic properties such as duplex structure, and results in the inferior quality of pellets across the bed. In order to predict the optimum thermal profile to achieve homogenous good quality pellets on consistent basis, it is necessary develop a model based on the kinetics of each of these phenomena. This will help to identify and optimize the responsible process parameters during induration accordingly. Subsequent to the investigation of sintering kinetics of magnetite pellets, the current study focuses on the oxidation phenomena. The reaction mechanisms for oxidation of magnetite pellets is dependent primarily on factors such as temperature and oxygen content in the oxidizing gas, etc. Isothermal oxidation of magnetite at pellet scale has been studied experimentally using Thermogravimetric Analyzer (TGA) by inserting the single pellet directly into the isothermal zone of the furnace. It has been found that the oxidation phenomena in the magnetite pellets is a multi-stage phenomena dominated by distinct mechanisms depending on varying extent of oxidation with respect to temperature and oxygen content.

  • 25.
    Kumar, T K Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Indian Institute of Technology Bombay (IITB).
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Central Metallurgical Research& Development Institute (CMRDI).
    Andersson, C.
    Luossavaara -Kiirunavara Aktiebolag (LKAB).
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Investigating the Physico-Chemical Mechanisms during Induration of Magnetite Pellets2016Konferensbidrag (Övrigt vetenskapligt)
  • 26.
    Kumar, T K Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Simonsson, Martin
    Ductus Preeye AB.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Indian Institute of Technology Bombay .
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    El-Geassy, Abdel-Hady A.
    Department of Minerals Technology and Processing, Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Establishing a Novel Methodology to Correlate the Macroscopic and Microscopic Degree of Sintering inMagnetite Pellets during Induration2018Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 89, nr 3, artikel-id 1700366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quality of product pellets is a result of the physico-chemical phenomenainvolved in the induration process. Sintering is the primary phenomenon,and its degree or extent contributes substantially to the evolution of themetallurgical and mechanical properties of a pellet. During the induration ofmagnetite pellets, sintering proceeds through the oxidized and non-oxidizedmagnetite phases. Sintering of these phases has been previously studied ona single pellet at the macroscopic scale using an optical dilatometer. Adeeper understanding requires corroboration of these studies throughcharacterization at the microscopic scale. In the present work, the observationsrecorded at the microscopic scale are quantified using image processingtechniques to correlate them to the macroscopic measurements. Distancetransformation, which is an image processing principle, is adapted in a novelway to digitize the microstructures and to determine the degree of sinteringin a pellet quantitatively. This methodology has potential applications as ageneric tool to follow the sintering phenomenon and process kinetics at anystage during induration.

  • 27.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Indian Institute of Technology, Bombay.
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget.
    Magnusson, Gustaf
    LKAB, Research & Development, 983 81 Malmberget.
    Effect of Heating Rates on the Sintering of Oxidized Magnetite Pellets during Induration2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Magnetite pellet induration is a combination of complex physicochemical phenomena – oxidation, sintering and theheat transfer associated with them. Depending on the pellet properties and the environment it encounters duringthe induration, the oxidation and sintering course may vary and the mechanisms will interact. To be able to predict their course and control it, the kinetics of these phenomena needs to be understood. One approach is to determine the kinetics of the phenomena in isolation. The present investigation is aimed to predict and studying the sintering behavior of oxidized magnetite (hematite) pellets exposed to different heating rates. Experiments have been carefully performed at three different heating rates to capture the sintering behavior during induration using an optical dilatometer, and also used for validation.

  • 28.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Magnusson, Gustaf
    LKAB Research and Development.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    LKAB Research and Development.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Optical Dilatometer: A New way to Understand and Quantify Sintering Kinetics of Iron Ore Pellets2014Konferensbidrag (Refereegranskat)
  • 29.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Indian Institute of Technology Bombay.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Central Metallurgical Research& Development Institute (CMRDI).
    Andersson, Charlotte
    LKAB, Research & Development.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Erratum to: Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 1, s. 743-745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Authors have used a new way for measuring bulk volume based on the image (pixel) analysis named as Light Table Imaging (LTI), and subsequently bulk densities and porosities. Authors lately found that there was a slight error in calibrating the scale (known distance) to pixel measurement and understand the need to communicate the error and subsequent corrections.  

  • 30.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Indian Institute of Technology Bombay.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    LKAB, Research & Development.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Erratum to: Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 1, s. 746-748Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Authors have used a new way for measuring bulk volume based on the image (pixel) analysis named as Light Table Imaging (LTI), and subsequently bulk densities and porosities. Authors lately found that there was a slight error in calibrating the scale (known distance) to pixel measurement and understand the need to communicate the error and subsequent corrections.  

  • 31.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer2015Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, nr 2, s. 635-643Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quality of magnetite pellet is primarily determined by the physico-chemical changes thepellet undergoes as it makes excursion through the gaseous and thermal environment in theinduration furnace. Among these physico-chemical processes, the oxidation of magnetite phaseand the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital.Rates of these processes not only depend on the thermal and gaseous environment the pellet getsexposed in the induration reactor but also interdependent on each other. Therefore, a systematicstudy should involve understanding these processes in isolation to the extent possible andquantify them seeking the physics. With this motivation, the present paper focusses on investigatingthe sintering kinetics of oxidized magnetite pellet. For the current investigation, sinteringexperiments were carried out on pellets containing more than 95 pct magnetiteconcentrate from LKAB’s mine, dried and oxidized to completion at sufficiently low temperatureto avoid sintering. The sintering behavior of this oxidized pellet is quantified throughshrinkage captured by Optical Dilatometer. The extent of sintering characterized by sinteringratio found to follow a power law with time i.e., Ktn. The rate constant K for sintering wasdetermined for different temperatures from isothermal experiments. The rate constant, K, varieswith temperature as lnTKð1=nÞ ¼ lnK0 QRT ; and the activation energy (Q) and reaction rateconstant (K¢) are estimated. Further, the sintering kinetic equation was also extended to a nonisothermalenvironment and validated using laboratory experiments.

  • 32.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Indian Institute of Technology Bombay.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Central Metallurgical Research& Development Institute (CMRDI), Cairo, Egypt.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Luossavaara-Kiirunavara Aktiebolag (LKAB), Gallivare, Sweden.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sintering Mechanism of Magnetite Pellets during Induration2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In Europe, Sweden has the richest magnetite ore deposits. The mined magnetite ore is ground, beneficiated and pelletized to make the process sustainable and environment friendly. These pellets are subsequently processed in blast furnaces, and hence the optimum pellet quality is of utmost important. Magnetite green pellets are indurated (heat hardened) in either rotary kiln or straight grate induration furnace to attain the quality standards in terms of strength and other metallurgical properties. The quality of magnetite pellet is primarily determined by the physico-chemical changes the pellet undergoes as it makes excursion through the gaseous and thermal environment in the induration furnace. Among these physico-chemical processes, the oxidation of magnetite phase and the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital. Rates of these processes not only depend on the thermal and gaseous environment the pellet gets exposed in the induration reactor but are also interdependent on each other. Therefore, a systematic study has been done to understand these processes in isolation to the extent possible and quantify them seeking the physics.Optical Dilatometer was used in a novel way to design the experiments on single pellets, exposed to different thermal profiles, in order to quantify the sintering of oxidized magnetite and non-oxidized magnetite, independently. Power law (Kt^n) and Arrhenius (푙n(TK(1^n) = ln K' - Q/RT) equations quantifies sintering behavior by estimating three isothermal kinetic parameters, namely – activation energy (Q), pre-exponential factor (K’) and time exponent (n). The values of activation energy and time exponent derived suggests that sintering of oxidized magnetite (hematite) is a single dominant diffusion mechanism, whereas sintering of unoxidized magnetite might be a combination of two distinct mechanisms; one operating at lower temperatures and the other at higher temperatures. The isothermal sintering kinetic equation is also extended to predict the non-isothermal sintering, and validated with the laboratory experiments. This will be further useful in predicting the sintering state of pellets during induration in the plant scale operations.

  • 33.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Studying the Sintering Behavior of Oxidized Magnetite Pellet During Induration2015Ingår i: AISTech 2015: Proceedings of the Iron & Steel Technology Conference : 4-7 May 2015, Cleveland, Ohio, U.S.A / [ed] Ronald E Ashburn, Warrendale, PA: Association for Iron & Steel Technology , 2015, s. 611-618Konferensbidrag (Refereegranskat)
    Abstract [en]

    Pelletization is by far the leading agglomeration technique practiced in Sweden and also across the world for magnetite fines. Magnetite pelletization provides an added advantage in terms of energy generated from exothermic nature of magnetite oxidation. Swedish steel industries pioneered in operating their blast furnaces with cent percent pellets. This makes it necessary to understand the entire process of pelletization, where green pellets are strengthened through heat hardening process known as induration for subsequent use in iron making units such as blast furnace and direct reduced iron processes.

  • 34.
    Kumar, TK Sandeep
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Department of Metallurgical Engineering & Materials ScienceIndian Institute of Technology Bombay (IITB).
    Ahmed, Hesham M.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Central Metallurgical Research & Development Institute (CMRDI).
    Andersson, Charlotte
    LKAB, Research & Development, 983 81 Malmberget.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer2016Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, nr 1, s. 309-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During induration of magnetite pellets, oxidation of magnetite followed by sintering of the oxidized magnetite (hematite) is desirable. Sintering of magnetite which hampers the oxidation of magnetite is aimed to be kept as low as possible. In succession to our earlier study on sintering behavior of oxidized magnetite (hematite), this paper focusses on the sintering behavior of magnetite phase in isolation with an objective to estimate their kinetic parameters. The pellets prepared from the concentrate of LKAB’s mine, which majorly contains (>95 pct) magnetite, are used for the sintering studies. Optical Dilatometer is used to capture the sintering behavior of the magnetite pellet and determine their isothermal kinetics by deducing the three parameters, namely—activation energy (Q), pre-exponential factor (K′), and time exponent (n) with the help of power law and Arrhenius equation. It is interesting to find that the time exponent (n) is decreasing with the increase in sintering temperature. It is also interesting to note that the activation energy for sintering of magnetite pellet shows no single value. From the present investigation, two activation energies—477 kJ/mole [1173 K to 1373 K (900 °C to 1100 °C)] and 148 kJ/mole [1373 K to 1623 K (1100 °C to 1350 °C)]—were deduced for sintering of magnetite, suggesting two different mechanisms operating at lower and other at higher temperatures. The estimated kinetic parameters were used to predict the non-isothermal sintering behavior of magnetite using the sintering kinetic model. Predicted results were validated using experimental data.

  • 35.
    Mahmood, Luckman
    et al.
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Evaluating the chemical diffusion coefficient of sulfur in slag by metal analysis2012Ingår i: Model Concept and Experiments: 9th International Conference on Molten Slags, Fluxes and Salts, Bejing 27-30 may 2012, 2012Konferensbidrag (Refereegranskat)
  • 36.
    Muhmood, Luckman
    et al.
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Concepts and measurement of velocities and viscosities at the slag-metal Interface2012Ingår i: Model Concept and Experiments: 9th International Conference on Molten Slags, Fluxes and Salts, Bejing 27-30 May 2012, 2012Konferensbidrag (Refereegranskat)
  • 37.
    Muhmood, Luckman
    et al.
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Nurni, Viswanathan
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Studies of dynamic mass transfer at the slag–metal interface: Interfacial velocity measurements2012Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, nr 7, s. 875-883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamics of oxygen transport along the slag – metal interface of pure iron and alumina-saturated CaO – Al2O3– SiO2slag was studied using high-temperature X-ray image analysis. The oscillations of the metal drop occurring due to the interfacial movement of oxygen atoms driven by Marangoni forces were studied in detail. The change in interfacial area during the oscillations was measured using a digitizing software and MATLAB. It was observed that the interfacial velocity as a function of oxygen exhibits insignificant variation with temperature. Further, the values obtained for the interfacial velocity using oxygen concentration difference at the interface were slightly lower in comparison to those using sulfur. The possible reason for this lower velocity could be that, although oxygen is a smaller atom compared to that of sulfur, the energy barrier at the free iron surface is higher for oxygen, thus hindering its motion along the interface

  • 38.
    Muhmood, Luckman
    et al.
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Nurni, Viswanathan
    Iwase, Masanori
    Thermochemistry Group, Department of Energy Science and Technology, Kyoto University.
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Evaluating the diffusion coefficient of sulfur in low-silica CaO-SiO 2-Al 2O 3 slag2011Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 2, s. 274-280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chemical diffusion coefficient of sulfur in the ternary slag of composition 51.5 pct CaO-9.6 pct SiO 2-38.9 pct Al 2O 3 slag was measured at 1680 K, 1700 K, and 1723 K (1403 °C, 1427 °C, and 1450 °C) using the experimental method proposed earlier by the authors. The P S2 and P O2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS. The density of the slag was obtained from earlier experiments. Initially, the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration curve for sulfur obtained from the program was in good fit with the experimental results. The diffusion coefficient of sulfur in 51.5 pct CaO-9.6 pct SiO 2-38.9 pct Al 2O 3 slag was estimated to be in the range 3.98 to 4.14 × 10 -6cm 2/s for the temperature range 1680 K to 1723 K (1403 °C to 1450 °C), which is in good agreement with the results available in literature

  • 39.
    Muhmood, Luckman
    et al.
    Aditya Birla Science and Technology Company Ltd, Navi Mumbai.
    Nurni, Viswanathan
    Seetharaman, Seshadri
    Department of Materials Science and Engineering, Division of Materials Process Science, Royal Institute of Technology.
    A new approach for the diffusion coefficient evaluation of sulfur in CaO-SiO 2-Al 2O 3 slag2011Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Vol. 312-315, s. 626-634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO- 9.6% SiO 2- 38.9% Al 2O 3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The P S2 and P O2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO- 9.6% SiO 2- 38.9% Al 2O 3 slag at 1723 K was estimated as 4.14×10 -6 cm 2/sec

  • 40.
    Muhmood, Luckman
    et al.
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    Nurni, Viswanathan
    Seetharaman, Seshadri
    Division of Materials Process Science, Department of Materials Science and Engineering, Royal Institute of Technology.
    A proposal for a novel method to measure the diffusivity of species in slag2011Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 2, s. 393-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate of reactions involved in steel-refining operations largely depend on the transport of species through the slag or metal phase at steel refining temperatures; the intrinsic reaction rates are expected to be high. Therefore, the study of diffusivity of species in slag is of great importance. The present work proposes a new methodology, in which experiments can be designed to determine the diffusivity of species in liquid slag. In this article, a mathematical description for the methodology is formulated and subsequently solved using numerical methods. This exercise will help in identifying appropriate bounds for experimental parameters for a desired accuracy. The proposed methodology is generic for any species in the liquid slag phase. However, diffusion of sulfur through slag has been illustrated as a case study. The order of magnitude for the diffusion coefficient for sulfur was taken from the classic works of Saito and Kawai, the sulfide capacity and sulfur partition ratio were retrieved from the works of Taniguchi et al., and the slag density was retrieved from earlier experimental results of the present authors. The slag density was obtained from earlier experimental results from the present group. The Henrian activity coefficients were retrieved from literature. Subsequent to the present work, the design of experiments and measurements carried out using the proposed methodology and the results obtained are presented as the second article on this subject.

  • 41.
    Muhmood, Luckman
    et al.
    Department of Materials Science and Engineering, Division of Materials Process Science, Royal Institute of Technology.
    Nurni, Viswanathan
    Seetharaman, Seshadri
    Department of Materials Science and Engineering, Division of Materials Process Science, Royal Institute of Technology.
    Some investigations into the dynamic mass transfer at the slag-metal interface using sulfur: Concept of interfacial velocity2011Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 3, s. 460-470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the current work, dynamic studies of mass transfer of sulfur from the gas phase to the metal phase of pure iron through CaO-SiO2-Al 2O3-FeO quaternary slag were carried out. X-ray videos were taken that were later processed to identify the oscillation of the metal drop occurring during the mass transfer. It was observed that the metal drop had hybrid oscillations. Each of these oscillations could be identified as composed of a symmetric and an asymmetric element, which was attributed to the changes in the shape of the droplet. The latter (asymmetric part) could be identified by the deviation of the left and right contact angles from the stable configuration. The symmetric oscillations were traced to the surface movement of sulfur at the interface, which created an instantaneous area change at the slag-metal interface. This area change was due to the combined effect of Marangoni flow and interface dilatation. The velocity of sulfur at the interface was calculated from the area change and had a maximum order of magnitude as 10-4 m/s. It was also observed that the interfacial velocity increased with increase in temperature

  • 42.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Activity: Oxidation kinetics of Fe-Cr and Fe-V liquid alloys under controlled oxygen pressures2010Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 43. Nurni, Viswanathan
    Application of simulation techniques in improve process performance: a few case studies2004Konferensbidrag (Refereegranskat)
  • 44. Nurni, Viswanathan
    Modelling of heat transfer during Al wire injection into a steel ladle2005Konferensbidrag (Refereegranskat)
  • 45. Nurni, Viswanathan
    Understanding gas phase chemistry in HWCVD of a Si: H2005Konferensbidrag (Refereegranskat)
  • 46. Nurni, Viswanathan
    et al.
    Adhikari, Subhra
    Dusane, R.O.
    Computational studies of the HWCVD deposition process during amorphous and nanocrystalline silicon films2006Konferensbidrag (Refereegranskat)
  • 47.
    Nurni, Viswanathan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ballal, Bharath
    Indian Institute of Technology, Bombay.
    Model for reduction of iron oxide pellet with a C-O-H-N gas mixture considering water gas shift equilibrium in the gas while it diffuses through the product layer2013Ingår i: Journal of Chemistry and Chemical Engineering, ISSN 1934-7375, E-ISSN 1934-7383, nr 7, s. 666-670Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In metallurgical processes, more and more usage of hydrocarbons is encouraged to bring down the carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This may be owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1,000 K, generally so for many reduction processes, the homogeneous gas reaction rates are expected to be high enough that local equilibrium in the gas phase can be assumed. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.

  • 48.
    Nurni, Viswanathan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ballal, Bharath Nidambur
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Rate Phenomena in Process Metallurgy2013Ingår i: Treatise on Process Metallurgy, Elsevier, 2013, s. 658-815Kapitel i bok, del av antologi (Refereegranskat)
  • 49.
    Nurni, Viswanathan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ballal, Bharath Nidambur
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    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.
    Mass Diffusion in Process Metallurgy2015Ingår i: Diffusion Phenomena in Engineering Materials, Trans Tech Publications Inc., 2015, s. 140-157Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Diffusion phenomena are of great importance in materials processing wherein atomic,molecular or ionic species are distributed within a phase or among different phases. Though thephenomenological equation describing the diffusion phenomena including the bulk flow arising outof diffusion in fluid and the phenomena of Kirkendall shift in substitutional solids are the same,these processes are often treated independently. Some discussion on this aspect is presented in thetheoretical aspects of diffusion. Owing to the complexity of atomic interactions, prediction ofdiffusion coefficients in condensed systems from first principles may not be that reliable;Experimental determination of diffusion coefficients is essential. In the second section, some novelexperimental techniques developed recently to measure diffusion coefficients in the solid state aswell as liquid systems including those in slags are described. In the last section, two case studieson application of diffusion phenomena in process metallurgy are presented emphasizing theimportance of these in metallurgical processing.

  • 50.
    Nurni, Viswanathan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ballal, N Bharath
    Department of Metallurgical Engineering, Indian Institute of Technology, Bombay.
    Model for reduction of iron oxide pellet with a C-O-H-N gas mixture considering water gas shift equilibrium in the gas while it diffuses through the product layer2012Ingår i: XXVI International Mineral Processing Congress: IMPC 2012, New Delhi, India, September 24-28, 2012 : conference proceedings, New Delhi: The Indian Institute of Metals , 2012, Vol. 2, s. 3921-3928Konferensbidrag (Refereegranskat)
    Abstract [en]

    In metallurgical processes, a higher usage of hydrocarbons is encouraged to bring down carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This is perhaps owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1000K, which is generally so for many reduction processes, the homogeneous gas reaction rates are expected to be so high that one can assume local equilibrium in the gas phase. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using a shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.

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