ISIJ International
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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559

ISIJ International Vol. 32 (1992), No. 6

  • Theoretical Study on an Oxygen Blast Furnace Using Mathematical Simulation Model

    pp. 701-708

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    DOI:10.2355/isijinternational.32.701

    Theoretical Study was made on the reasonable use of oxygen in the blast furnace to achieve both high productivity and low fuel rate with one dimensional blast furnace mathematical simulation model and following results were obtained.
    (1) There exist an optimum oxygen concentration and an optimum flame temperature and the increase of the oxygen concentration straightly results in the increases of fuel rate.
    (2) By the combined injection of pulverized coal with the increase of oxygen concentration to control the flame temperature at an optimum value of about 2100°C, both high productivity and low fuel rate can be achieved.
    x

    Readers Who Read This Article Also Read

    1. Experimental Study on an Oxygen Blast Furnace Process Using a Small Test Plant ISIJ International Vol.32(1992), No.6
    2. Fundamental Study on Combustion of Pulverized Coal Injected into Coke Bed at High Rate ISIJ International Vol.32(1992), No.6
    3. Mechanisms of Hanging Caused by Dust in a Shaft Furnace ISIJ International Vol.31(1991), No.9
  • Experimental Study on an Oxygen Blast Furnace Process Using a Small Test Plant

    pp. 709-715

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    DOI:10.2355/isijinternational.32.709

    Experimental as well as theoretical studies were made on the oxygen blast furnace characterized by the combined injection of pulverized coal and following results were obtained.
    (1) In the test plant with a production capacity of 15 t/d, 1.2 kg of pulverized coal per 1 Nm3 of oxygen in blast was injected without any trouble and such an operation result as the coal rate of 407 kg/t, the coke rate of 258 kg/t and the productivity of 7.35 t/d/m3 was achieved.
    (2) By using one dimensional blast furnace mathematical simulation model, it was predicted that the pulverized coal rate of 375 kg/t, the coke rate of 180 kg/t and the productivity of 3.3 t/d/m3 can be achieved in a commercial blast furnace.
    x

    Readers Who Read This Article Also Read

    1. Mechanisms of Hanging Caused by Dust in a Shaft Furnace ISIJ International Vol.31(1991), No.9
    2. Prediction of a Blast Furnace Burden Distribution Variable ISIJ International Vol.36(1996), No.9
    3. Theoretical Study on an Oxygen Blast Furnace Using Mathematical Simulation Model ISIJ International Vol.32(1992), No.6
  • Maximum Injection Rate of Pulverized Coal into Blast Furnace through Tuyeres with Consideration of Unburnt Char

    pp. 716-724

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    DOI:10.2355/isijinternational.32.716

    Experiments concerning the combustion and consumption of pulverized coal (PC) with high volatile matter content were conducted using an experimental apparatus capable of simulating the heat transfer and reactions in the lower part of the blast furnace.
    First, the calculating method of PC combustion efficiency in the raceway was proposed and the effects of blast conditions on the efficiency were investigated.
    Secondly, the calculating method of PC consumption efficiency at the apparatus top was proposed and the effects of blast conditions on the efficiency were investigated.
    Thirdly, the unburnt char volume accumulating in the apparatus was measured and the limited char volume not causing the permeability deterioration in the apparatus was found.
    As a result of these analyses, the following conclusion was obtained concerning the maximum PC injection rate:
    Under the conditions of blast temperature of 1300°C, blast humidity of 5 g/Nm3 and oxygen enrichment of 2%, the limit PC injection rate is over 245 g/Nm3 (240 kg/t-pig) in the actual blast furnace that prevents the discharge of char from the furnace top and does not cause the permeability deterioration even when char accumulates in the furnace.
    x

    Readers Who Read This Article Also Read

    1. Mechanisms of Hanging Caused by Dust in a Shaft Furnace ISIJ International Vol.31(1991), No.9
    2. Prediction of a Blast Furnace Burden Distribution Variable ISIJ International Vol.36(1996), No.9
    3. Suppression of the Formation of Large Pores in the Assimilated Parts of Sinter Produced Using Pisolitic Ores ISIJ International Vol.36(1996), No.11
  • Fundamental Study on Combustion of Pulverized Coal Injected into Coke Bed at High Rate

    pp. 725-732

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    DOI:10.2355/isijinternational.32.725

    In view of rebuilding coke ovens and flexible operation of blast furnace, it is one of the most important topics in ironmaking process to establish the stable operation of blast furnace at high pulverized coal injection.
    Especially, the clarification of the internal behavior of pulverized coal in blast furnace such as combustion behavior in the raceway and consumption or accumulation of unburnt char in the furnace is indispensable.
    This paper is concerned with the research on the effect of coal injection rate, coal types and coal size on the internal state of blast furnace, with use of a coke-packed hot model furnace and mathematical models which cosist of the combustion mathematical model in the raceway and gas and solid two phase mathematical model in the packed bed.
    (1) The combustibility of coal at the tuyere level decreased with increase of coal injection rate or decrease of volatile matter in coal. However, the combustibility of coal measured at 700 mm above the tuyere level is over 95%.
    (2) This phenomenon is explained by the two phase gas and solid mathematical model considering the rate of the solution loss reaction of unburnt char.
    (3) In case of coarse coal size of –3 mm, the combustibility of coal at 700 mm above tuyere level decreased as well as that at the tuyere level.
    x

    Readers Who Read This Article Also Read

    1. Experimental Study on an Oxygen Blast Furnace Process Using a Small Test Plant ISIJ International Vol.32(1992), No.6
    2. Simulation of the Blast Furnace Process by a Mathematical Model ISIJ International Vol.32(1992), No.4
    3. Theoretical Study on an Oxygen Blast Furnace Using Mathematical Simulation Model ISIJ International Vol.32(1992), No.6
  • Bench Scale Test of a New Ironmaking Process with Mixture of Iron Ore Concentrate and Pulverized Coal

    pp. 733-740

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    DOI:10.2355/isijinternational.32.733

    A new metallurgical reactor called the LB Furnace is currently being developed at McMaster University. A series of experiments on ironmaking was conducted successfully in a laboratory bench scale furnace. Sponge iron and hot metal were produced with desired properties by using mixture of iron ore concentrate and pulverized coal. Compositions of hot metal (except carbon) and slag produced are similar to those of the blast furnace products. The carbon content of the hot metal can be effectively controlled in the range of 0.3 to 4.0%. Sponge iron can be produced with different degrees of metallization, up to 99%. The unique design of the reduction unit of the LB Furnace has achieved its goals: (1) the direct use of iron ore concentrate and pulverized coal, (2) the intensive reduction reactions (15 kg Fe/hr throughput in a 8.3 cm reduction tube of 75 cm long, or 88 tonne Fe/d/m3 of the reduction tube inner volume), and (3) the complete combustion of the gaseous reduction products in one single reactor for high energy efficiency.
    x

    Readers Who Read This Article Also Read

    1. Mechanisms of Hanging Caused by Dust in a Shaft Furnace ISIJ International Vol.31(1991), No.9
    2. Prediction of a Blast Furnace Burden Distribution Variable ISIJ International Vol.36(1996), No.9
    3. Suppression of the Formation of Large Pores in the Assimilated Parts of Sinter Produced Using Pisolitic Ores ISIJ International Vol.36(1996), No.11
  • Influence of Slag Composition and Temperature on Slag Foaming

    pp. 741-746

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    DOI:10.2355/isijinternational.32.741

    The slag foaming behavior caused by the reaction between FeO containing slag and hot metal was investigated for the CaO-SiO2-Al2O3-P2O5-TiO2-MnO-MgO-CaF2 system. The peak of slag foaming height was observed when (CaO)/(SiO2) was around 1.2 and the peak value of (CaO)/(SiO2) became slightly large with the increase in temperature and the CaF2 mixing ratio. In the high (CaO)/(SiO2) region, the slag foaming height increased with the increase in temperature and the CaF2 mixing ratio.
    Under this experimental condition, the inverse proportional relationship between the slag viscosity and the slag foaming height was found but no significant influence of P2O5 was observed. In the solid and liquid coexisting region, slag foaming height increased with the increase in liquid fraction.
  • Bubble Characteristics in the Buoyancy Region of a Vertical Bubbling Jet

    pp. 747-754

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    DOI:10.2355/isijinternational.32.747

    The flow field in a vertical bubbling jet in a cylindrical vessel with bottom blowing can be divided into four regions. They are named the momentum, transition, buoyancy and surface regions in order of increasing distance from the nozzle exit. In a previous paper, bubble behavior characterized by gas holdup, bubble frequency, bubble rising velocity and so on was clarified for the momentum region in which the inertia force of injected gas played an important role. In the present study, bubble behavior in the buoyancy region in which the buoyancy force of bubbles governed the flow was investigated by means of two kinds of electro-resistivity porbes, a high-speed video camera, and a laser Doppler velocimeter. The bubble behavior was not affected by the nozzle diameter and the bath diameter. Therefore, correlations for gas holdup, bubble frequency and bubble rising velocity were proposed as functions of gas flow rate.
  • Solubility of NbC in a Ni-16Cr-8Fe Alloy

    pp. 755-763

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    DOI:10.2355/isijinternational.32.755

    The solubility of niobium carbide NbC in the nickel-rich phase of the Ni-16Cr-8Fe system, which is a base system of commercial Inconel alloy 600, was experimentally determined at a temperature range between 1273 and 1473 K. A ternary Ni-16Cr-8Fe alloy was prepared from three elemental metals. Thirteen Ni-16Cr-8Fe-Nb quaternary alloys with niobium concentrations between 0 and 6.0 mass% were prepared from the Ni-16Cr-8Fe alloy and pure niobium. The Ni-16Cr-8Fe-Nb alloys were carburized by a sealed capsule method at equilibrating temperatures of 1273, 1373 and 1473 K for various times between 3.1×105 and 7.8×105 sec. Carbon activity in each capsule was determined from the carbon concentration of the pure iron sealed in the capsule together with the alloys.
    Only niobium carbide NbCx was observed as a second phase in the equilibrated alloys under the present experimental conditions. The carbon concentration x of NbCx was lower than that of the stoichiometric carbide NbC and was estimated to be x=0.81 from the experimentally determined solubility of NbCx in the nickel-rich phase. The solubility was described as a solubility product and its temperature dependence was evaluated as (mass% Nb)(mass% C)0.81=exp{7.5-(14000/T)} or YNb(YC)0.81=exp{0.053-(14000/T)}, where the concentration parameters of niobium and carbon, YNb and YC, are related to the mole fractions, XNb and XC, by the equations YNb/(1-XC) and YC=XC/(1-XC). The present results were compared with those for commercial Inconel alloy 600.
  • Influence of Deformation on Stability of TiC Precipitates in α-Fe

    pp. 764-770

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    DOI:10.2355/isijinternational.32.764

    To investigate the influence of deformation on the stability of TiC precipitates in the α-Fe region, the temperature of precipitation treatment and the strain rate of deformation prior to final soaking at 773 K were changed with an Fe-0.05mass%Ti-0.002mass%C alloy. Precipitation treatment at 973 K for a short time generated very fine TiC particles (average radius: 2 nm) which were presumed to be coherent or semi-coherent because of a strong strain contrast in TEM images. Deformation with a high strain rate (1226 s-1) just after precipitation treatment of 973 K for a short time resulted in a distinct increase in the solute C content, suggesting that some of the coherent TiC precipitates had dissolved. The elastic interaction between the coherent TiC particles and a high density of dislocation induced by the high strain rate deformation is considered to be the most conceivable explanation of several mechanisms including the temperature increase due to deformation and binding between dislocations and C at grain boundaries. Based on the micromechanics of an anisotropic and inhomogeneous system, the interaction energy was calculated from a simple case consisting of an isolated coherent TiC particle and a straight-edge dislocation. The calculation of the change in total free energy supported the possibility of TiC dissolution due to the elastic interaction between coherent TiC precipitates and a high density of dislocations induced by the high strain rate deformation.
  • Influence of Macro/Microstructure on the Toughness of 'All Weld' Multipass Submerged Arc Welded C-Mn Steel Deposits

    pp. 771-778

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    DOI:10.2355/isijinternational.32.771

    'All weld' deposited rectangular blocks of C-Mn steel were prepared by the multipass submerged arc process, using different welding currents (500-750 A) and speeds (40-60 cm/min). A filler wire of 4 mm diameter and a basic agglomerated flux were employed. Varying the welding parameters influenced the macrostructure comprising coaxial dendrites and reheat refined regions whose amounts were determined by quantitative metallography. The influence of dendrite content, on the toughness as influenced by temperature and orientation of the specimens (LT, TS and SL) was assesed both in the as welded and in the heat treated (873 K) conditions.
    An increase in the area fraction of dendrites beyond about 37% adversely affected the toughness which was found to be lowest in the LT direction. A post weld heat treatment carried out at 873 K improved the overall toughness due to spheroidization of cementite, especially within the refined equiaxed regions, resulting from 'reheating' during multipass deposition.
  • Precipitation Kinetics of Microalloying Additions during Hot-rolling of HSLA Steels

    pp. 779-785

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    DOI:10.2355/isijinternational.32.779

    The control of the precipitation of microalloying elements (Nb-Ti-V) during hot-rolling processes is of prime importance for the development of HSLA steels, ensuring reproducibility and homogeneity of the mechanical properties.
    In the present work, the effects of processing parameters and steel chemistry on the precipitation kinetic during hot-rolling, are quantified using SED method (selective electrolytic dissolution). Anisothermal and isothermal precipitation kinetic in austenite during rolling and in ferrite are compared and discussed. In ferrite, during or after transformation, an important distinction is made between coherent and incoherent precipitated forms. The coherent precipitation kinetic, which appears to be very fast in ferrite at high temperature, is studied by hardness measurements. It is shown that cooling rates higher than 20°C s-1 are needed to avoid coherent precipitation on the runout table of a finishing mill.

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