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Tetsu-to-Hagané Vol. 95 (2009), No. 3

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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575
Publisher: The Iron and Steel Institute of Japan

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Tetsu-to-Hagané Vol. 95 (2009), No. 3

Preface to the Special Issue “Innovative Development of Refining Processes in Steelmaking by Multi Phase Fluxes”

Fumitaka Tsukihashi

pp. 187-187

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Preface to the Special Issue “Innovative Development of Refining Processes in Steelmaking by Multi Phase Fluxes”

Characteristics of Quick Lime by Various Calcining Methods

Nobuyuki Ishiwata, Hiroyasu Ito

pp. 188-198

Abstract

The fact has been known that lime is one of the most important materials as flux in steelmaking. The last decade, the average supply of lime for flux is up to 5.5 million tons/year. Fluorspar is convenient material for making flux as dropping of melting point of slag, a number of steel making plants didn't pay attention to the standards of lime but for chemical compound and reactivity. But nowadays, because the solution of fluorine in soil is becoming serious, and the use of fluorspar has been restricted as flux. So, the characteristic of lime, such as surface area and microstructure are drawing the attention for making slag.
In this paper, it is reviewed that improving of characteristics of quick lime by various calcination methods.

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Characteristics of Quick Lime by Various Calcining Methods

Estimation of Oxygen Potential at Slag/Metal Interface and Effect of Initial Slag Condition on Hot Metal Dephosphorization

Ken-ichiro Miyamoto, Ken-ichiro Naito, Itsuro Kitagawa, Michitaka Matsuo

pp. 199-206

Abstract

Hot metal dephosphorization experiments at the small size scale furnace were performed for the purpose of estimating the interfacial oxygen potential of dephosphorization reaction between slag and metal, and investigating the influence of initial slag condition on dephosphorization behavior and the formation of solid phase.
The results are summarized as follows;
(1) Interfacial oxygen potential was estimated from phosphorous distribution ratio and slag composition at the turning point from dephosphorization to re-phosphorization. It exists between oxygen potential of slag bulk and oxygen potential of metal bulk at every slag composition. Furthermore, as slag basicity becomes low, interfacial oxygen potential increases and tends to approach the oxygen potential of slag bulk.
(2) In the case of initial lump-sum addition of iron oxide to slag, it was possible to increase the reaction rate of dephosphorization and decrease the final [%P] value. By means of enhancing (FeO) content in slag composition, slag can be controlled to have low melting point and dephosphorization between liquid phase of slag and metal proceeds efficiently. This slag control at the early stage of dephosphorization makes it possible to crystallize C2S phase from liquid phase efficiently and concentrate phosphorous in C2S phase at the late stage. On the other hand, in the case of divided addition of iron oxide, the stagnation of dephosphorization was observed. In this case, C2S phase was crystallized at the early stage while dephosphorization between liquid phase and metal didn't proceed sufficiently. Therefore, crystallization of C2S phase at the early stage retard the transport of phosphorous to C2S phase at the late stage.

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Estimation of Oxygen Potential at Slag/Metal Interface and Effect of Initial Slag Condition on Hot Metal Dephosphorization

Kinetics Behavior of Iron Oxide Formation under the Condition of Oxygen Top Blowing for Dephosphorization of Hot Metal in the Basic Oxygen Furnace

Akitoshi Matsui, Seiji Nabeshima, Hidetoshi Matsuno, Naoki Kikuchi, Yasuo Kishimoto

pp. 207-216

Abstract

The effects of hot metal temperature, oxygen gas flow rate from a top lance and argon gas flow rate from an injection lance on iron oxide formation and dephosphorization rates in hot metal were investigated with 3 kg- and 200 kg-scale furnaces. The results were summarized as follows.
1) Iron oxide formation rate increased with lower hot metal temperature, higher oxygen gas flow rate and lower argon gas flow rate.
2) A kinetic model was developed to estimate the iron oxide formation on hot metal, and a mathematical model for hot metal dephosphorization has been made based on the aforementioned model of iron oxide formation and the coupled reaction model.
3) Dephosphorization and the formation rate of iron oxide in 200 kg-scale tests agreed well with those were obtained by the mathematical model.
4) Oxygen activity at slag/metal interface obtained by the mathematical model agreed with the equilibrium oxygen activity with FeO in slag.
5) In the early stage of dephosphorization, the gas flow rate of the bottom blowing need to be lower in order to enhance the iron oxide formation. In the late stage of dephosphorization, that needs to be higher in order to enhance the mass transfer of phosphorus in hot metal.
6) Industrial hot metal dephosphorization tests were carried out with a 350 t-scale top and bottom converter. The conditions of top blowing oxygen and bottom blowing nitrogen have been improved by adopting the mathematical model in order to increase the iron oxide content in slag. It has been possible to increase dephosphorization efficiency without fluor spar at lower hot metal temperature (below 1300°C) by improving the blowing conditions.

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Kinetics Behavior of Iron Oxide Formation under the Condition of Oxygen Top Blowing for Dephosphorization of Hot Metal in the Basic Oxygen Furnace

Phase Relation of CaO–Al2O3–FetO–P2O5 Slag and Phosphorus Distribution between This Slag and Liquid Iron

Kei Watanabe, Takahiro Miki, Yasushi Sasaki, Mitsutaka Hino

pp. 217-221

Abstract

Amount of steelmaking slag emission is increasing due to strong demand for high quality steel. Development of slag and process that can remove impurity at high efficiency is required to decrease slag discharge volume. Phosphorus is a typical impurity in steel and it can be removed by slag with high CaO and FetO activity. CaO–FetO–P2O5 system has two liquid phase region that has CaO and FetO high activity. It was confirmed that CaO–MgO–FetO–P2O5 two liquid phase slag can remove phosphorus at high efficient in the previous work. The phase relation and ability of phosphorus removal by CaO–Al2O3–FetO–P2O5 system was investigated in the present work.

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Phase Relation of CaO–Al2O3–FetO–P2O5 Slag and Phosphorus Distribution between This Slag and Liquid Iron

Thermochemistry of Heterogeneous CaO–P2O5–SiO2–FexO and CaO–P2O5–CaF2–FexO Slags

Masakatsu Hasegawa, Masanori Iwase

pp. 222-228

Abstract

In steelmaking processes, because of environmental requirements and health considerations, there is a strong incentive to reduce slag volume. The key to meet this requirement is the better understanding of phosphorus removal, which relies on the knowledge of the thermodynamic properties of slags and fluxes used for dephosphorization. In this study, the liquidus compositions of the four-phase assemblages in the quaternary systems of CaO–P2O5–SiO2–FexO and CaO–P2O5–CaF2–FexO were determined by employing electron probe microanalysis. Measurements were also made on the FexO activities by employing an electrochemical technique involving stabilized zirconia electrolyte.

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Thermochemistry of Heterogeneous CaO–P2O5–SiO2–FexO and CaO–P2O5–CaF2–FexO Slags

Distribution of P2O5 between Solid Dicalcium Silicate and Liquid Phases in CaO–SiO2–Fe2O3 System

Ken-ichi Shimauchi, Shin-ya Kitamura, Hiroyuki Shibata

pp. 229-235

Abstract

In most cases, the slag used in hot metal dephosphorization exists in a solid–liquid coexisting state, containing dicalcium silicate as the solid phase. It is known that dicalcium silicate (C2S) and tricalcium phosphate (C3P) form a solid solution with a wide range of composition. A large distribution ratio of P2O5 between a solid solution and liquid slag phases has also been reported. To clarify the maximum concentration of P2O5 in this solid solution phase, the measurement of the distribution ratio of P2O5 in slag containing a high concentration of P2O5 is performed in this research, and the influence of MgO and MnO on the distribution ratio is investigated. CaO–SiO2–Fe2O3 slag containing a maximum of 18% P2O5 is melted at 1873K and cooled to 1673K at a cooling rate of 10K/min. During cooling, the solid solution of dicalcium silicate and tricalcium phosphate precipitates from the liquid slag. A good relation is found between the distribution ratio of P2O5 and (T.Fe); this relation is independent of slag composition and P2O5 content. The concentration of P2O5 in the solid solution is strongly influenced by the mixing ratio of P2O5 and the slag composition. It is clarified that if the slag composition is controlled adequately, the concentration of P2O5 in the C2S–C3P solid solution can be increased up to 100% of C3P. The change in the distribution ratio with the addition of MgO and MnO is not large.

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Distribution of P2O5 between Solid Dicalcium Silicate and Liquid Phases in CaO–SiO2–Fe2O3 System

The Model Experiment on the Formation of 2CaO·SiO2–3CaO·P2O5 Phase in the Dephosphorization Slag

Masayuki Kami, Masahiro Terasawa, Atsushi Matsumoto, Kimihisa Ito

pp. 236-240

Abstract

The formation of the Ca2SiO4–Ca3P2O8 phase in a hot metal dephosphorization slag was investigated. The reaction of a P2O5-containing slag with a solid porous CaO was observed at 1673K by using a hot thermo-couple method. A CaO–FeO layer was formed near the interface, and next to it a solid solution of Ca2SiO4–Ca3P2O8 containing FeO was observed. The results could be explained in terms of the model proposed by Hamano et al. The Fe–P–Si alloy was reacted with dicalcium ferrite at 1673K, and the samples were analyzed by XMA. The phosphorus concentrated phases were observed near the slag–metal interface. Their compositions could be approximated as 2(CaO+FeO)·SiO2–3(CaO+FeO)·2O5 and their FeO concentration decreased as the progress of the reaction.

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The Model Experiment on the Formation of 2CaO·SiO2–3CaO·P2O5 Phase in the Dephosphorization Slag

Phosphorous Partition in Dephosphorization Slag Occurring with Crystallization at Initial Stage of Solidification

Khanh Son Pham, Yoshiaki Kashiwaya

pp. 241-250

Abstract

Basicity and the amount of FetO were investigated for their effects on the crystallization behavior of the simulated dephosphorizing slags. Twelve kinds of slags were prepared (C/S=1.0–2.5, FetO=10–20%, P2O5=5%). In the present experiment, the Hot Thermocouple Technique was used to melt and quench the samples. After quenching, the microstructure of the slag and the distributions of elements were examined by SEM and EDS analysis.
The diameter of the crystal which precipitated in the sample increased with increasing basicity (C/S) and decreasing FetO content. In addition, glassy regions were observed in the two samples whose FetO content was 20% and whose basicity was 1.0 or 1.5. The samples (10% FetO, 5% P2O5), whose basicity was 1.0 (sample-1) precipitated as a monocalcium silicate (CaO·SiO2); the sample (10% FetO, 5% P2O5) whose basicity was 1.5 (sample-4) precipitated as a dicalcium silicate (2CaO·SiO2). In higher FetO (15–20%) slags, the crystals of the solid solution between 3CaO·P2O5 and 2CaO·SiO2 ((C3P–C2S)ss) were observed. When the amount of CaO increased from C/S=1.5 to C/S=2.5, 2CaO·SiO2 appeared with phosphorous content, but phosphorous was not found in CaO·SiO2.

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Phosphorous Partition in Dephosphorization Slag Occurring with Crystallization at Initial Stage of Solidification

Growing Process of Crystal Precipitated in the Dephosphorization Slag and Phosphorous Partition between Crystal and Liquid

Yoshiaki Kashiwaya, Khanh Son Pham

pp. 251-257

Abstract

To reduce the amount of steelmaking slag and the free CaO, it is necessary to increase the reaction efficiency of CaO. Several investigations have been carried out to clarify the reaction of solid CaO in a molten slag. The process of dissolving CaO is quite complicated, because the melting point changes in accordance with the CaO content.
In the previous study, using the Hot Thermocouple Technique (HTT), the twelve kinds of artificial dephosphorization (de-P) slag have been melted and quenched. The effects of basicity and FetO content on the crystallization behavior of the de-P slag have been investigated at the initial stage of solidification.
In the present study, the growing process of the precipitated crystal until 10000 s was investigated and the change of the phosphorous distribution between the crystal and the liquid in slag was clarified. The growth of a crystal can be expressed by Johnson–Mehl type equation, while the number of crystal decreases through a coalescence of each crystal and the equation of half-life for atomic disintegration was applied to the coalescence of crystals in the initial stage of crystal growth process. Total volume of the precipitated crystal increased within the initial stage of crystal growth, on the other hand, the total volume of crystal was a constant within the later stage of crystal growth.
The Lp (5(P2O5)cry/(P2O5)liq) was obtained at different temperatures (1550°C and 1350°C). The maximum value of Lp at 1550°C was 6.5 to 9.5 in the time range from 5 s to 15 s, while the equilibrium value was 2.0 to 2.2. On the other hand, at 1350°C, the maximum Lp was 4.0 to 4.5 around 5 s and the equilibrium value was 2.6 to 3.0 which is higher than that at 1550°C.

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Growing Process of Crystal Precipitated in the Dephosphorization Slag and Phosphorous Partition between Crystal and Liquid

Microscopic Formation Mechanisms of P2O5-containing Phase at the Interface between Solid CaO and Molten Slag

Reita Saito, Hiroyuki Matsuura, Kenji Nakase, Xiao Yang, Fumitaka Tsukihashi

pp. 258-267

Abstract

It is quite important to reveal the microscopic reaction mechanisms and the role of the solid and liquid phases in the solid CaO coexisting flux in the hot metal dephosphorization process. In the present study, solid CaO piece and FeOx–CaO–SiO2–P2O5 slag with various FeOx and P2O5 contents, and CaO/SiO2 ratios of the slag were reacted at 1573 and 1673K. The interface between solid CaO and molten slag was observed and analyzed by SEM/EDS. Microscopic reaction mechanisms between solid CaO and molten slag was discussed with changing reaction times, slag compositions and temperatures. The CaO–FeOx phase adjacent to solid CaO, and the CaO–SiO2 or CaO–SiO2–P2O5 solid phase coexisting with the FeOx–CaO–SiO2 liquid slag next to the CaO–FeOx phase were observed for all slag compositions, temperatures and reaction times. Phosphorus was condensed as 2CaO·SiO2–3CaO·P2O5 phase more easily in the case of higher CaO/SiO2 ratio and higher FeOx content in slag. There was a linear relationship between P2O5 content in 2CaO·SiO2–3CaO·P2O5 phase and the distance from CaO–FeOx phase to 2CaO·SiO2–3CaO·P2O5 phase. The P2O5 content increased from CaO–FeOx boundary toward bulk slag, and P2O5 content in the condensed phase near the CaO–FeOx phase increased with increasing reaction time. This P2O5 concentration gradient tended to diminish. These results suggest that the condensation of phosphorus as 2CaO·SiO2–3CaO·P2O5 phase was controlled by P2O5 diffusion from bulk slag to reaction interface, not by absorption of P2O5 into 2CaO·SiO2 particle.

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Microscopic Formation Mechanisms of P2O5-containing Phase at the Interface between Solid CaO and Molten Slag

Formation Behavior of Phosphorous Compounds at the Interface between Solid 2CaO·SiO2 and FeOx–CaO–SiO2–P2O5 Slag at 1673K

Xiao Yang, Hiroyuki Matsuura, Fumitaka Tsukihashi

pp. 268-274

Abstract

The role of 2CaO·SiO2 phase on the formation of P2O5 condensed phase should be clarified to elucidate the microscopic dephosphorization mechanisms and to improve the hot metal dephosphorization efficiency by using CaO-based FeOx–CaO–SiO2–P2O5 multi phase flux. In the present study, solid 2CaO·SiO2 piece was reacted with molten FeOx–CaO–SiO2–P2O5 slag for 1 to 60 s at 1673K, and the reaction interface between solid 2CaO·SiO2 and molten FeOx–CaO–SiO2–P2O5 slag was observed and analyzed by SEM and EDS.
The dissolution of 2CaO·SiO2 into the molten slag and the penetration of molten slag into solid 2CaO·SiO2 simultaneously occurred. The 2CaO·SiO2–3CaO·P2O5 was formed from solid 2CaO·SiO2 and P2O5 in the slag. On the other hand, during the penetration of slag, the P2O5 in the slag reacted with 2CaO·SiO2 to form 2CaO·SiO2–3CaO·P2O5 phase. The P2O5 content of 2CaO·SiO2–3CaO·P2O5 phase existing in solid 2CaO·SiO2 region was lower than that observed at the 2CaO·SiO2 saturated liquid phase region because of the lower P2O5 content of penetrating slag than that of 2CaO·SiO2 saturated liquid slag. The 2CaO·SiO2 saturated liquid slag region and the region where P2O5 condensed phase was observed at the interface expanded with time.

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Formation Behavior of Phosphorous Compounds at the Interface between Solid 2CaO·SiO2 and FeOx–CaO–SiO2–P2O5 Slag at 1673K

Trial on the Application of Capillary Phenomenon of Solid CaO to Desulfurization of Liquid Fe

Toshihiro Tanaka, Yumi Ogiso, Mituru Ueda, Joonho Lee

pp. 275-281

Abstract

In order to carry out the de-sulfurization of liquid Fe, solid CaO is usually used as a flux, but some of solid CaO particles are not melted into molten slag, and all CaO are not always used for the refining. We have investigated how to use the solid CaO directly and efficiently for the above refining processes. Solid CaO particles have small capillary tubes from their surface to inside. When a molten slag is wetted with solid CaO, the molten slag containing some impurities such as CaS and P2O5 is expected to penetrate into those capillary tubes. Although chemical reactions in solid phase are generally believed to be very slow due to slow diffusion in solid phase, those impurities are absorbed in solid CaO rapidly by capillary force and they are removed from molten steels. We named this refining process as Capillary Refining. In the present paper, we have tried to apply capillary refining to de-sulfurization of liquid Fe and carbon-saturated liquid Fe by using molten CaO–Al2O3 and CaO–SiO2–MgO–Al2O3 slags.

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Trial on the Application of Capillary Phenomenon of Solid CaO to Desulfurization of Liquid Fe

Viscosity Evaluation of CaO–SiO2–R2O (R=Li, Na and K) Based Multi-phase Fluxes

Noritaka Saito, Shinji Yoshimura, Shinichiro Haruki, Yoshinori Yamaoka, Sohei Sukenaga, Kunihiko Nakashima

pp. 282-288

Abstract

Viscosity of CaO–SiO2–R2O system at elevated temperature has been systematically evaluated with a rotating-crucible viscometer over the wide range of temperature, which includes the region of solid–liquid coexistence, so called “multi-phase”. It was found that the viscosities of CaO–SiO2–R2O melts increased with temperature decrease, and were described with Arrehnius type temperature dependence between 20–100°C range of temperature below the liquidus. The rheological characterization of CaO–SiO2–R2O melts had a transition from Newtonian to non-Newtonian fluid at a given temperature, which was classified as Bingham fluid according to the relationship between the shear rate and the shear stress calculated based on the experimental condition and the viscosity data. It was unveiled that the crystallization behavior controlled the changes in the Bingham yield stress τB of CaO–SiO2–K2O multi-phase fluxes with temperature decrease. The gradual increase of τB was attributed to the crystallization of the super-cooled melt with the dispersed fine grains. The devitrification with the course dentritic crystals caused the steep increase of τB.

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Viscosity Evaluation of CaO–SiO2–R2O (R=Li, Na and K) Based Multi-phase Fluxes

Thermal Conductivity Measurements and Prediction for Molten Silicate Slags with Dispersing CaO Phases

Masahiro Susa, Naohiko Tsuchida, Rie Endo, Yoshinao Kobayashi

pp. 289-296

Abstract

The present work has aimed to confirm experimentally the applicability of the following prediction equation for thermal conductivity to molten silicate slags with dispersing CaO phase:

[Equation]

where λeff is the effective thermal conductivity of the whole system, λ0 and λ1 are the thermal conductivities of the matrix and dispersing phases, respectively, and f0 is the volume fraction of the matrix phase. The above equation was conventionally proposed to predict thermal conductivities for two-phase systems with dispersing phases such as composite materials, and thus it was required to investigate its applicability to liquid samples with dispersing solid phases. First, thermal conductivity measurements were made at room temperature on silicone oil having polyethylene dispersion and gel and paraffin having alumina dispersion as well as the single phases of the constituent substances. Likewise, thermal conductivities were also measured on molten CaO–3mass%SiO2–37mass%Al2O3 slags having CaO dispersion at 1743K. These measurements have confirmed that the prediction equation applies to the two-phase systems with dispersing phases used in the present work. Thus, it is likely that thermal conductivities of molten silicate slags with dispersing CaO phase can be predicted from the equation using the thermal conductivities of CaO and molten slags and the volume fraction of CaO at a given temperature as long as no percolation of CaO occurs.

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Thermal Conductivity Measurements and Prediction for Molten Silicate Slags with Dispersing CaO Phases

The Estimation of Structural Properties for the CaO–SiO2–CaCl2 Melts by Molecular Dynamics Simulations

Kentaro Asakura, Kimihisa Ito

pp. 297-299

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The Estimation of Structural Properties for the CaO–SiO2–CaCl2 Melts by Molecular Dynamics Simulations

Magnetic Separation of Phosphorus Enriched Phase from Multiphase Dephosphorization Slag

Hironari Kubo, Kazuyo Matsubae-Yokoyama, Tetsuya Nagasaka

pp. 300-305

Abstract

The authors have found that phosphorus exhibits remarkable segregation in the exhausted actual hot metal pretreatment slag (dephosphorization slag) and it exists as 3CaO·P2O5–2CaO·SiO2 solid solution together with FeO–CaO–SiO2 matrix. Since their magnetic properties are significantly different, it is possible to separate them with the aid of superconducting strong magnetic field. In order to investigate effects of magnetic field strength, particle size of slag and so on, the experiment of the magnetic separation has been carried out by using simulated dephosphorization slag (18.1FetO–45.9CaO–20.3SiO2–6.6 P2O5–2.5MnO–5.5MgO in mass%) and super conducting magnet with 0.5 to 2.5 T. At stronger magnetic field, the quality of the recovered slag becomes better due to smaller contamination of FetO matrix phase while its quantity becomes worse and the amount of recovered slag is smaller. However, the quantity of the recovered slag can be improved by repeating the magnetic separation procedure. In the present experiment, about 65% of phosphorus enriched slag can be recovered with less than 10% of FetO matrix phase contamination at the condition of 0.5 T, particle size of smaller than 35 mm and water/slag ratio of 32 with single procedure. P2O5 content in the recovered slag is very close to that in the phosphorus enriched phase in the initial slag and FetO content is markedly decreased with magnetic separation.

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Magnetic Separation of Phosphorus Enriched Phase from Multiphase Dephosphorization Slag

Recycling Effect of Residual Slag after Magnetic Separation for Phosphorus Recovery from Hot Metal Dephosphorization Slag

Kazuyo Matsubae-Yokoyama, Hironari Kubo, Tetsuya Nagasaka

pp. 306-312

Abstract

The authors have found in their previous work that phosphorus exhibits remarkable segregations in the industrial hot metal pretreatment slag and it exists as Ca3P2O8–Ca2SiO4 solid solution together with FeO–CaO–SiO2–MnO–MgO matrix. Since their magnetic property of each phase is significantly different, it is possible to separate each phase with the aid of superconducting strong magnetic field. By applying strong magnetic field of 0.5 to 2.5 T to the crushed slag, more than 60% of phosphorus concentrated phase in the slag has been recovered. If the most of phosphorus can be removed from the slag, the residual slag is basically FeO–CaO–SiO2–MnO–MgO with less P2O5 and thus it may be recycled to iron and steelmaking processes such as the sintering, hot-metal desiliconization, and hot-metal dephosphorization processes. In the present work, the recycling effect of the residual slag to the dephosphorization process is simulated based on the mass balance calculation. The significant reduction of total slag generation and CaO input has been demonstrated by the mathematical model considering phosphorus recovery and recycling of residual slag as a dephosphorization agent. It has also been indicated by the Waste Input–Output model that the phosphorus recovery from dephosphorization slag and the recycling of residual slag to hot metal dephosphorization process have great environmental and economical benefits.

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Recycling Effect of Residual Slag after Magnetic Separation for Phosphorus Recovery from Hot Metal Dephosphorization Slag

Analysis of Dephosphorization Reaction Using a Simulation Model of Hot Metal Dephosphorization by Multiphase Slag

Shin-ya Kitamura, Ken-ichiro Miyamoto, Hiroyuki Shibata, Nobuhiro Maruoka, Michitaka Matsuo

pp. 313-320

Abstract

In most cases, the slag used in hot metal dephosphorization is saturated with dicalcium silicate, and the partition ratio of phosphorus between dicalcium silicate and liquid slag is high. These results indicate the important role of solid dicalcium silicate in dephosphorization. In order to understand reaction kinetics and obtain an optimum treatment method, it is very important to know the influence of the solid phases in the slag. In this study, a new reaction model for hot metal dephosphorization is applied to the experimental results; this model considers the effects of dicalcium silicate and the dissolution rate of lime. By the calculation results, the influence of various factors on the reaction efficiency is discussed.
The calculated results are in almost good agreement with the experimental results obtained by various slag compositions and by various methods of flux and oxide additions to hot metal. By the calculation, in order to perform the dephosphorization reaction efficiently, we clarify the existence of the optimum basicity that considers the precipitation behavior of the solid phase in slag. Also, the optimum condition between the stirring energy and the supplying rate of flux and oxide was found.

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Analysis of Dephosphorization Reaction Using a Simulation Model of Hot Metal Dephosphorization by Multiphase Slag

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