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Shinya Kitamura - One of the best experts on this subject based on the ideXlab platform.

  • Celebrating the Megascale: Proceedings of the Extraction and Processing Division Symposium on Pyrometallurgy in Honor of David G.C. Robertson - Analysis of Steelmaking Reactions by Coupled Reaction Model
    Celebrating the Megascale, 2014
    Co-Authors: Shinya Kitamura
    Abstract:

    Kinetic modeling is very important to understand steelmaking reactions. The coupled reaction model proposed by Prof. D.G.C Robertson is the best suited program, and therefore, the author has applied it to the various steelmaking reactions, a few examples of which are discussed. Hot metal dephosphorization occurs under non-equilibrium conditions as it takes place between the Slag, which has a high oxygen potential, and the hot metal, which has a low oxygen potential. A process simulation model based on the coupled reaction model was constructed. This model considers the solid and Liquid Slag, Liquid metal phases, and the reaction between the solid and Liquid Slag, besides the reaction between the Liquid Slag and Liquid metal. Using this model, the ruling factor to increase the reaction efficiency of dephosphorization has been verified. In the secondary refining process, the values of inclusion composition calculated by the thermodynamic model, under the assumption of equilibrium with the metal composition, were found to be different from those observed in practice. A kinetic model, incorporating the reactions between Slag, metal, inclusion, and refractory has been postulated, and the composition change of inclusion during treatment has been analyzed.

  • Influence of Solid CaO and Liquid Slag on Hot Metal Desulfurization
    ISIJ International, 2012
    Co-Authors: Koichi Takahashi, Hiroyuki Shibata, Shinya Kitamura, Keita Utagawa, Naoki Kikuchi, Yasushi Kishimoto
    Abstract:

    Mechanical stirring is widely used for hot metal desulfurization in Japan. In this process, solid lime is added as flux and emulsified into molten iron using a vortex formed by the stirrer. However, in addition to the added solid lime, the Liquid top Slag on the ladle is emulsified and forms granules. To clarify the roles of the solid lime and Liquid Slag in hot metal desulfurization, the reaction rates of Slag, solid lime, and Slag with solid lime are determined and the interfacial layers are observed.The results are summarized as follows:(1) The desulfurization rate is very slow when a solid lime rod is immersed into hot metal without Slag. The reason for the slow desulfurization is the formation of an interfacial layer, which inhibits the mass transfer of sulfur.(2) Because sulfur is not detected inside the solid CaO, the mass transfer of sulfur from the Liquid Slag to the solid CaO does not occur. Therefore, it is believed that solid CaO does not play a direct role in the desulfurization reaction, and thus, the reaction is solely due to the Liquid Slag. A good relationship between the desulfurization rates and the sulfide capacity of the Liquid Slag is found.(3) When tricalcium aluminate forms at the interface, the desulfurization rate is increased by the immersion of a CaO rod. This is due to the supply of CaO to the Slag because this interfacial layer does not inhibit the mass transfer.

  • Importance of Kinetic Models in the Analysis of Steelmaking Reactions
    steel research international, 2010
    Co-Authors: Shinya Kitamura
    Abstract:

    In this paper, examples of the use of a kinetic model in the analysis of a steelmaking process will be discussed. In decarburization by BOF, the relation between C and O contents is different from that obtained by equilibrium calculations. By the use of kinetic models, it was clarified that the O content in the metal is controlled not only by the C content but also by the FeO activity in the Slag. In the vacuum degassing process, the partial pressure calculated on the basis of the relation between C and O contents is much higher than the operation pressure. The kinetic model which considers the circulation between the molten steel in the vacuum vessel and that in the ladle is well known; furthermore, various decarburization mechanisms were proposed. Hot metal dephosphorization occurs under non-equilibrium conditions because the oxygen potential of the Slag and that of the hot metal are different. Process analysis is performed by considering the reaction kinetics based on the coupled reaction model. Recently, a new reaction model has been proposed; this model considers the solid Slag, Liquid Slag, and Liquid metal phases and the reaction between the solid and Liquid Slag, in addition to the reaction between the Liquid Slag and Liquid metal.

  • simulation of steel refining process in converter
    Steel Research International, 2010
    Co-Authors: Farshid Pahlevani, Hiroyuki Shibata, Shinya Kitamura, Nobuhiro Maruoka
    Abstract:

    Steel refining is a complex phenomenon which depends on numerous variables, so, a kinetic approach is necessary for precise understanding of the refining process. In this study, based on a previously proposed model for hot metal dephosphorization, a new simulation model for the steel refining process in BOF is presented. In most cases, steelmaking Slag is saturated with dicalcium-silicate (C2S) and it is well known that C2S forms solid solution with tricalcium-phosphate (C3P) in a wide composition range and the partition ratio of phosphorus between C2S and Liquid Slag is large. On the other hand, C2S formed around the lime surface is known as a barrier to lime dissolution into Liquid Slag. In this simulation model not only the effect of solid phase in Slag is considered but also the effects of temperature dependence of variables as well as top and bottom blowing and scrap melting are taken into account. The calculation results are compared with industrial data and the good agreement between experimental and simulation results evidence the validity of this kinetic approach to steel refining process in BOF. Moreover, by using this model the influence of various parameters on the reaction efficiency is discussed.

  • mass transfer of p2o5 between Liquid Slag and solid solution of 2cao sio2 and 3cao p2o5
    Isij International, 2009
    Co-Authors: Shinya Kitamura, Hiroyuki Shibata, Shinya Saito, Keita Utagawa, D G C Robertson
    Abstract:

    Hot metal dephosphorization Slags in the BOF can be considered to be within the CaO–SiO2–FeO–P2O5 system, and are usually in the dicalcium silicate (C2S) saturated composition range. It is well known that C2S forms a pseudo-binary solid solution with tricalcium phosphate (C3P) over a wide composition range at the dephosphorization treatment temperature. To increase the reaction efficiency of dephosphorization, it is important to increase the mass transfer rate of P2O5 from the Liquid Slag to the solid solution.In order to clarify the mechanism of mass transfer of P2O5 between the solid solution and Liquid Slag, an artificially made C2S–C3P solid solution rod was dipped into the C2S–C3P saturated Slag and the interface was observed.When the activity of P2O5 in Liquid Slag was higher than that in solid solution, a reaction layer was formed at the interface, and its width increased with immersion time. A concentration gradient of P2O5 was observed in the solid solution.When the activity of P2O5 in Liquid Slag was lower than that in solid solution, no reaction layer was formed, and P2O5 did not transfer to the Liquid Slag. In this case, P2O5 in the solid solution was quite stable.The reason for these phenomena was discussed. The mass transfer of CaO and SiO2 must occur simultaneously with the mass transfer of P2O5 in order to maintain the pseudo-binary relation of the solid solution.

Haifeng Liu - One of the best experts on this subject based on the ideXlab platform.

  • Effects of the bubbles in Slag on Slag flow and heat transfer in the membrane wall entrained-flow gasifier
    Applied Thermal Engineering, 2017
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Dong Han, Haifeng Liu
    Abstract:

    Abstract The Slag from the industrial gasifier has porous structure, which has a non-ignorable influence on the characteristics of Slag layer. The Slag flow and heat transfer model were modified based on the effective thermal conductivity and viscosity, to predict the Slag characteristics for the effects of bubbles in Slag. The results show that bubbles inside Slag reduce the Slag thermal conductivity and viscosity. The modified model predicts the Liquid Slag velocity, Slag layer thickness and heat flux of Slag layer. The Liquid Slag flow velocity increases with the increase of bubbles inside Slag, while the thickness of Slag layer decreases. In addition, the increasing gas volume fraction of bubbles inside Slag decreases the heat flux of Slag layer. Two models are applied to calculate the bubbly Slag effective thermal conductivity. The Maxwell-Eucken thermal conductivity model is more accurate than geometric mean model from the result of Slag layer heat flux.

  • Modeling the Slag flow and heat transfer with the effect of fluid-solid Slag layer interface viscosity in an entrained flow gasifier
    Applied Thermal Engineering, 2017
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The characteristics of Slag flow and heat transfer in a gasifier are significant for controlling the operation conditions. Determination of the fluid-solid Slag layer interface is a crucial procedure in the studying of Slag flow and heat transfer characteristics. The varied absolute viscosities were used as the fluid-solid Slag layer interface viscosity to model the Slag layer properties in an entrained flow gasifier. The results showed that with the increase of fluid-solid Slag layer interface viscosity, the Liquid Slag layer thickness increased, while the solid Slag layer thickness and the Liquid Slag velocity decreased. Moreover, the Slag layer overall thickness had a slight decrease, while the Slag heat flux had a slight increase. In addition, the effects of the fluid-solid Slag layer interface viscosity on Slag layer characteristics with glassy Slag and plastic Slag were relatively higher than crystalline Slag. The smoother the viscosity-temperature profile, the higher the influences of the fluid-solid Slag layers interface viscosity. The critical viscosity could be approximate regarded as the fluid-solid Slag layer interface viscosity when the Slag type was crystalline Slag during the model derivation, and the fluid-solid interface viscosity can be defined as about 100 Pa s for plastic Slag and glassy Slag.

Evgueni Jak - One of the best experts on this subject based on the ideXlab platform.

  • Advances in Molten Slags, Fluxes, and Salts: Proceedings of the 10th International Conference on Molten Slags, Fluxes and Salts - Thermodynamic modelling of Liquid Slag-matte-metal equilibria applied to the simulation of the Peirce-Smith converter
    Advances in Molten Slags Fluxes and Salts: Proceedings of the 10th International Conference on Molten Slags Fluxes and Salts 2016, 2016
    Co-Authors: Denis Shishin, Taufiq Hidayat, Sergei A. Decterov, Evgueni Jak
    Abstract:

    Computer simulation plays an increasingly important role in improving the environmental and economic performance of pyrometallurgical extraction processes. The thermodynamic description of the chemical systems involved is at the core of such advanced simulation software. A thermodynamic database has been developed to describe the phase relations and chemical reactions in the Al—Ca—Cu—Fe—Mg—O—S—Si chemical system with support from the leading copper producers. The database contains model parameters for gas, Liquid Slag, Liquid matte and metal, spinel and numerous solid phases. Models based on the Modified Quasichemical Formalism were used for the Slag, matte and Liquid metal. The internal consistency of the database provides accurate and reliable predictions outside of the usual operating conditions. The development of the database was closely integrated with the experimental studies of this chemical system. The database works in the environment of FactSage software. The application of thermodynamic modelling is illustrated by the example of the Peirce-Smith converter.

  • The effect of a temperature gradient on the phase formation inside a magnesia-chromite refractory in contact with a non-ferrous PbO-SiO2-MgO Slag
    Journal of the European Ceramic Society, 2015
    Co-Authors: Lennart Scheunis, Mieke Campforts, Bart Blanpain, Annelies Malfliet, Ata Fallah-mehrjardi, Peter Tom Jones, Evgueni Jak
    Abstract:

    Abstract Furnace relinings represent a major operating cost in pyrometallurgy. External cooling is, therefore, often used to reduce the chemical wear by limiting the Slag infiltration depth, reducing the reaction kinetics and lowering the solubility of refractory components into the Liquid Slag. In this paper a new experimental setup is used to study the reaction between a synthetic PbO–SiO2 based Slag and a magnesia–chromite refractory under a temperature gradient. Forsterite (Mg2SiO4) is formed throughout the sample, removing SiO2 from the infiltrated Liquid Slag. The resulting change in Slag composition causes the Liquidus temperature and the viscosity of the Liquid to decrease partially countering the effect of the applied temperature gradient and resulting in the complete infiltration of the sample. The extent to which external cooling prolongs the lifetime of an industrial furnace thus depends on the Slag properties and how they are modified after reaction with the refractory.

  • Quasi-Chemical Viscosity Model for Fully Liquid Slag in the Al2O3-CaO-MgO-SiO2 System—Part I: Revision of the Model
    Metallurgical and Materials Transactions B, 2013
    Co-Authors: Masanori Suzuki, Evgueni Jak
    Abstract:

    A model has been developed that enables the viscosities of the fully Liquid Slag in the multi-component Al2O3-CaO-FeO-Fe2O3-MgO-Na2O-SiO2 system to be predicted within experimental uncertainties over a wide range of compositions and temperatures. The Eyring equation is used to express viscosity as a function of temperature and composition. The model links the activation and pre-exponential energy terms in the viscosity expression to the Slag internal structure through the concentrations of various Si0.5O, \( {\text{Me}}^{n + }_{2/n} {\text{O}} \) , and \( {\text{Me}}^{n + }_{ 1/n} {\text{Si}}_{0. 2 5} {\text{O}} \) viscous flow structural units (SUs). The concentrations of these SUs are derived from a quasi-chemical thermodynamic model of the Liquid Slag using the thermodynamic computer package FactSage. The model describes a number of Slag viscosity features including the charge compensation effect specific for the Al2O3-containing systems. The predictive capability of the model is enhanced by the physical aspects of the model parameters—the correlation with other physicochemical properties as well as experimental viscosity data is used to determine model parameters. The present series of two papers outlines (a) recent significant improvements introduced into the model formalism and (b) application of the model to the Al2O3-CaO-MgO-SiO2 system, review of experimental viscosity data, and optimization of the corresponding model parameters for this system.

Mats Brämming - One of the best experts on this subject based on the ideXlab platform.

Satadal Ghorai - One of the best experts on this subject based on the ideXlab platform.

  • Submerged Liquid Slag injection in steel melt: scaleup study using cold model and dimensional analysis
    Ironmaking & Steelmaking, 2004
    Co-Authors: Satadal Ghorai, Gour Gopal Roy, S. K. Roy
    Abstract:

    Submerged injection of solid flux powder is used in the steel industry to eliminate impurities in an economical way. The efficiency of such an injection process is limited by the fact that only a fraction of the injected particles penetrate into the Liquid melt, while the majority remain as bubble encapsulated solids, causing poor heat and mass transfer. Therefore, Liquid Slag injection can be considered a potential alternative technique in the refining of steel to improve the efficacy of mass transfer in such a process. In the present work, Liquid Slag injection in a steel melt has been simulated by means of laboratory scale cold model experiments in which, water, paraffin oil and benzoic acid have been used as low temperature analogues for Liquid steel, Slag and impurities, respectively. Through dimensional analysis it is observed that the modified Froude number can be considered as a criterion for scaling up such a process from a bench scale to a full scale system. A regression analysis has also been carried out to correlate the dimensionless mass transfer rate constant with the relevant dimensionless numbers, namely, dimensionless gas velocity, Froude number, aspect ratio and non-dimensional lance depth.

  • Physical Simulation of Impurity Removal through Submerged Liquid Slag Injection in Steel Melt
    ISIJ International, 2004
    Co-Authors: Satadal Ghorai, Gour Gopal Roy, S. K. Roy
    Abstract:

    With the increase in demand for quality steel having very stringent compositional control, the secondary steelmaking has become one of the significant developments in the steel making technology during the past few decades. Injection of powder with inert carrier gas is commonly practiced in industry to decrease the impurity contents of steel in a more economical way. Such high temperature metallurgical operations are mass transfer controlled and accordingly the design and operating parameters have significant roles to play. However, powder particles can only penetrate partially to the Liquid melt while most of the particles ascend through the melt as “particles inside the bubble” in the semi-solid state without contributing much to mass transfer. In this regard submerged Liquid Slag injection may be considered as a potential area of investigation. In the present study, simulation of the submerged Liquid Slag injection in steel melt has been carried out using a cold model in the laboratory. Relative contributions of the transitory to permanent contact reactions have been estimated from several experimental data in conjunction with the mathematical model proposed by Ohguchi and Robertson. The present results show that mass transfer rate increases with increase in gas flow rate, Liquid injection rate and lance depth. An empirical correlation for overall mass transfer rate constant as a function of gas flow rate, oil injection rate and lance depth has been developed. The present result also indicates that transitory contribution increases significantly with increase in gas flow rate.

  • STEEL REFINING THROUGH SUBMERGED Liquid Slag INJECTION: EFFECT OF PARTIAL INJECTION BY A COLD MODEL STUDY
    2004
    Co-Authors: Satadal Ghorai, Gour Gopal Roy
    Abstract:

    Injection of powder with inert carrier gas is commonly practiced in industry to decrease the impurity level of steels in a more efficient and inexpensive way. However, the advantages of submerged powder injection process are limited by the fact that powder particles can only penetrate partially into the Liquid melt, while most of the particles ascend through the melt as "particles inside the bubble" without contributing much to the mass transfer process. In this regard, submerged Liquid Slag injection is considered as a potential area of research. Simulation of the submerged Liquid Slag injection in steel melt has been carried out using a cold model in the laboratory. In such a study, water, paraffin oil and benzoic acid have been used as the low temperature analogous for steel melt, Slag and the transferable species, respectively. The effect of partial injection of oil on the efficacy of the mass transfer process has been investigated. The pertinent results have been analyzed by using the mathematical model of Ohguchi and Robertson after required modification. At higher volume fraction of oil, partial injection do not seem to be very effective, while at lower volume fraction, the partial injection process is proved to be quite effective in the transfer of benzoic acid from the aqueous phase to the oil phase.