The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform

Masaaki Naito - One of the best experts on this subject based on the ideXlab platform.

  • gaseous reduction behavior of iron ore sinter and kinetic analysis in consideration of calcium ferrite reaction process
    2015-Sustainable Industrial Processing Summit, 2015
    Co-Authors: Tateo Usui, Masaaki Naito, Munekazu Ohmi, Hirotoshi Kawabata, Yasuhiro Nakamuro, Masahiro Nishi, Paulo Santos Assis
    Abstract:

    Rates of gaseous reduction of commercial sinter with CO-CO2-N2 or H2-H2O-N2 gas mixture were measured under single particle and fixed bed situation at a constant temperature. By these data analyses using the unreacted-core shrinking (UCS) models for one and three interface(s), rate parameters; namely chemical reaction rate constants and intra-particle effective diffusivities in the models were evaluated. Fixed bed packed with the sinter was also reduced under rising temperature conditions with stepwise gas concentration change, which was roughly simulated as in a blast furnace. The reduction rate was analyzed by using UCS model for three interfaces with the pre-determined rate parameter values; the comparison between the experimental reduction curve and the computed one showed rough agreement but not so precise and this discrepancy was considered by the existence of quaternary calcium ferrite (abbreviated by CF), which is reported the complex crystalline mineral produced from Fe2O3, CaO, SiO2 and Al2O3. In all the previous analyses for reduction reaction of iron oxides in a blast furnace, sinter was treated as pure iron oxides (hematite and magnetite); the existence of CF was disregarded. Afterward, final fractional reduction of sinter in hematite to magnetite stage was found out to be about 70 % at lower reduction temperatures, which was caused by the irreducibility of CF in this region and verified with XRD analysis. By changing reduction temperature and reducing gas composition, we determined the border line between CF (= 'Fe2O3') and 'Fe3O4'. Equilibrium relations for 'Fe3O4' / 'FeO' and 'FeO' / 'Fe' were reported by Prof. Maeda, et al, where 'Fe2O3', 'Fe3O4', 'FeO' and 'Fe' designate hematite, magnetite, wustite and iron stages of CF, respectively. Reduction steps for CF can be written as: CF (= 'Fe2O3') a†’ 'Fe3O4' a†’ 'FeO' a†’ 'Fe', which are much the same as those for pure iron oxides. However, a reported variation of gas composition with temperature measured in a blast furnace shows that the gas composition in the Thermal Reserve Zone is only a little higher than the wustite/iron equilibrium, the reduction potential of which is less than 'FeO' / 'Fe' equilibrium and hence 'FeO' cannot be reduced to 'Fe'. Therefore, gaseous reduction model for sinter has been developed in consideration of CF reaction process; UCS model for six interfaces has been proposed to take into account reaction processes of CF as well as pure iron oxides. Trial comparison of the calculated reduction curve with our previously reported experimental data mentioned above under simulated blast furnace conditions has shown rather reasonable agreement. The present model will play an important role in analyzing the reduction rate of sinter, in which CF is existing or even intentionally increasing to suppress the bad effect of SiO2.

  • enhancement of low temperature gasification and reduction by using iron coke in laboratory scale tests
    Isij International, 2011
    Co-Authors: Kenichi Higuchi, Seiji Nomura, Kazuya Kunitomo, Hirokazu Yokoyama, Masaaki Naito
    Abstract:

    Iron-coke having various amount of M.Fe were produced in laboratory scale and the influence of M.Fe content in Iron-coke on reaction behavior under the condition simulating blast furnace has been investigated. Cold strength of Iron-coke products was decreased with an increase of mixing ratio of iron ore mostly due to a prevention of dilatation of coal particles by iron ore, resulting in weak bonding of coal particles. Nevertheless formed Iron-coke with iron ore in the fraction up to 30% would have enough strength for use in blast furnace as nut coke. Both CRI and JIS-reactivity were enhanced by increasing ratio of mixed iron ore, confirming the catalysis effect of M.Fe. The temperature at which carbon consumption started was lowered with an increase of T.Fe in coke. Formed Iron-coke containing 43% of T.Fe started reaction consuming its carbon at lower temperature than conventional coke by 150°C. Furthermore, consumed carbon ratio was improved by M.Fe installation to coke due to increasing gasification. Process evaluation with using Iron-coke in blast furnace was performed by BIS test. It was revealed that using formed Iron-coke having 43% of T.Fe for blast furnace resulted in an increase of shaft efficiency by 6.8%. It was found that to lower the reducing agent rate in blast furnace by decreasing the temperature of Thermal Reserve Zone, lowering the beginning temperature of coke reaction was effective. Usage of Iron-coke having M.Fe catalyst within coke matrix is one of the methods.

  • reaction behavior of formed iron coke and its effect on decreasing Thermal Reserve Zone temperature in blast furnace
    Isij International, 2010
    Co-Authors: Seiji Nomura, Kenichi Higuchi, Kazuya Kunitomo, Masaaki Naito
    Abstract:

    Usage of highly reactive coke in order to decrease the Thermal Reserve Zone temperature in blast furnaces is promising to increase reaction efficiency in blast furnaces and to decrease the reducing agent rate. We focused on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. When the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the Thermal Reserve Zone temperature (900°C), which causes a decrease in the Thermal Reserve Zone temperature, while conventional coke barely reacts and is protected from degradation. It was also confirmed that the catalytic activity of Fe and that of K is independent of each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease the Thermal Reserve Zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

  • reaction behavior of formed iron coke and its effect of decreasing Thermal Reserve Zone temperature in blast furnace
    Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2009
    Co-Authors: Seiji Nomura, Kenichi Higuchi, Kazuya Kunitomo, Masaaki Naito
    Abstract:

    Usage of highly reactive coke in order to decrease Thermal Reserve Zone temperature in blast furnace is considered promising to increase reaction efficiency in blast furnace and to decrease reducing agent rate. We focused attention on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. It was shown that when the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the Thermal Reserve Zone temperature (900°C), which causes a decrease in Thermal Reserve Zone temperature, while conventional coke reacts little and is protected from degradation. It was also confirmed that catalytic activity of Fe and that of K is independent each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease Thermal Reserve Zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

  • improvement in blast furnace reaction efficiency through the use of highly reactive calcium rich coke
    Isij International, 2005
    Co-Authors: Seiji Nomura, Hiroyuki Ayukawa, Hisatsugu Kitaguchi, Toshihide Tahara, Shinroku Matsuzaki, Masaaki Naito, Satoshi Koizumi, Yoshikuni Ogata, Takeshi Nakayama, Tetsuya Abe
    Abstract:

    A method to produce coke in ‘lump’ form with high strength and reactivity through the addition of a catalyst was investigated in order to improve blast furnace reaction efficiency. The addition of Ca compounds to coal before carbonization was found to considerably increase the reactivity of the coke at a low temperature range in the Thermal Reserve Zone of a blast furnace. Furthermore it was proved that strong, highly reactive ‘lump’ form coke could be produced by adding a Ca-rich non-caking coal and adjusting the coal blend composition. Based on this fundamental study, the Ca-rich coke was successfully produced in coke ovens on a commercial scale, both at Kimitsu and Muroran works. The use of the Ca-rich coke in the Muroran No. 2 blast furnace was found to cause a decrease in the reducing agent rate by 10 kg/t-p. This technology, producing coke of high reactivity and strength through catalyst addition, is promising as a means of improving the reaction efficiency of a blast furnace.

Tatsuro Ariyama - One of the best experts on this subject based on the ideXlab platform.

  • improvement of reactivity of carbon iron ore composite with biomass char for blast furnace
    Isij International, 2009
    Co-Authors: Shigeru Ueda, Kazunari Yanagiya, Kentaro Watanabe, Ryo Inoue, Tatsuro Ariyama
    Abstract:

    Enhancement of reactivity of the burden in the blast furnace can decrease the reducing agent of blast furnace. Besides high reactivity coke, the carbon iron ore composite is considered to be a typical high reactivity burden that can control the Thermal Reserve Zone temperature. Since the reactivity of biomass char is much higher than that of coke, the use of carbon iron ore composite with biomass char will be favorable for decreasing the reducing agent. In the present study the reaction and reducing behavior of the carbon iron ore composite with biomass char were investigated. The gasification rate of biomass char was measured in CO2 atmosphere, and the reaction rate equation of that was derived. The microscopic structure change of biomass during carbonization was experimentally analyzed. According to the experimental results, the reduction of the composite begins at about 550°C in an inert gas atmosphere, and it is much lower than the composite with coke. Analysis of the reaction of carbon iron ore composite was carried out with the reaction model of the carbon iron ore composite based on a lumped system, in which the reaction rate of biomass char and iron ore were installed. The reaction model shows that the biomass char can improve the reduction behavior of the carbon iron ore composite especially in the lower temperature region. Moreover, the influence of gas atmosphere and the optimum structure of the composite were investigated by the model calculation to estimate the optimum condition of the composite in the blast furnace.

  • reaction model and reduction behavior of carbon iron ore composite in blast furnace
    Isij International, 2009
    Co-Authors: Shigeru Ueda, Kazunari Yanagiya, Kentaro Watanabe, Taichi Murakami, Ryo Inoue, Tatsuro Ariyama
    Abstract:

    Decreasing the carbon dioxide emission from steel industries is an important issue. It is considered that due to the high reactivity of carbon iron ore composite, it can control the Thermal Reserve Zone temperature and decrease the consumption of reducing agents in blast furnace. In the present study, a reaction model of the carbon iron ore composite based on a lumped system is proposed to analyze the reduction behavior in the blast furnace. This model is composed of several reaction steps between carbon, iron ore, and gas phase. The carbon solution loss reaction rate of the small particles of reducing agents is determined by the thermogravimetric method. It is found that the gasification of reducing agents is the rate-determining step in the reduction of the carbon iron ore composite. Accordingly, the particle size and reactivity of reducing agents such as coke have an influence on the reduction rate of the carbon iron ore composite. The influence of the gas composition in the atmosphere around the composite on the reduction is analyzed by using the reaction model. Moreover, the reduction behavior of the carbon iron ore composite in the blast furnace is quantitatively examined by comparison of reduction degree and gas composition change in order to investigate the reduction mechanism of reducing agents.

  • design of innovative blast furnace for minimizing co2 emission based on optimization of solid fuel injection and top gas recycling
    Isij International, 2004
    Co-Authors: Ryota Murai, Michitaka Sato, Tatsuro Ariyama
    Abstract:

    The concept of innovative ironmaking process for aiming at energy half consumption has been proposed based on the basic experiments and mathematical calculations. For innovative ironmaking process, intensive combustion technology around raceway was examined by hot model experiments and three-dimensional mathematical simulation so as to utilize solid fuel such as plastics effectively. As results, it became clear that simultaneous injection of pulverized coal/plastics or pulverized coal/gas fuels is favorable to improve combustion efficiency remarkably. Decrease in Thermal Reserve Zone temperature and top gas recycling besides plastics injection are found to be effective for lowering coke rate. In this process, productivity can be also improved owing to relaxation of flooding condition in the lower part of blast furnace. Productivity of 3.5 and more, that is determined by fluidization condition at top, can be expected in this innovative ironmaking process. Totally, it is evaluated that amount of carbon emission would be reduced by eighty-six percent provided sequestration of carbon dioxide is implemented. Finally, integrated ironmaking process with co-generating oxygen production process was proposed.

Seiji Nomura - One of the best experts on this subject based on the ideXlab platform.

  • enhancement of low temperature gasification and reduction by using iron coke in laboratory scale tests
    Isij International, 2011
    Co-Authors: Kenichi Higuchi, Seiji Nomura, Kazuya Kunitomo, Hirokazu Yokoyama, Masaaki Naito
    Abstract:

    Iron-coke having various amount of M.Fe were produced in laboratory scale and the influence of M.Fe content in Iron-coke on reaction behavior under the condition simulating blast furnace has been investigated. Cold strength of Iron-coke products was decreased with an increase of mixing ratio of iron ore mostly due to a prevention of dilatation of coal particles by iron ore, resulting in weak bonding of coal particles. Nevertheless formed Iron-coke with iron ore in the fraction up to 30% would have enough strength for use in blast furnace as nut coke. Both CRI and JIS-reactivity were enhanced by increasing ratio of mixed iron ore, confirming the catalysis effect of M.Fe. The temperature at which carbon consumption started was lowered with an increase of T.Fe in coke. Formed Iron-coke containing 43% of T.Fe started reaction consuming its carbon at lower temperature than conventional coke by 150°C. Furthermore, consumed carbon ratio was improved by M.Fe installation to coke due to increasing gasification. Process evaluation with using Iron-coke in blast furnace was performed by BIS test. It was revealed that using formed Iron-coke having 43% of T.Fe for blast furnace resulted in an increase of shaft efficiency by 6.8%. It was found that to lower the reducing agent rate in blast furnace by decreasing the temperature of Thermal Reserve Zone, lowering the beginning temperature of coke reaction was effective. Usage of Iron-coke having M.Fe catalyst within coke matrix is one of the methods.

  • reaction behavior of formed iron coke and its effect on decreasing Thermal Reserve Zone temperature in blast furnace
    Isij International, 2010
    Co-Authors: Seiji Nomura, Kenichi Higuchi, Kazuya Kunitomo, Masaaki Naito
    Abstract:

    Usage of highly reactive coke in order to decrease the Thermal Reserve Zone temperature in blast furnaces is promising to increase reaction efficiency in blast furnaces and to decrease the reducing agent rate. We focused on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. When the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the Thermal Reserve Zone temperature (900°C), which causes a decrease in the Thermal Reserve Zone temperature, while conventional coke barely reacts and is protected from degradation. It was also confirmed that the catalytic activity of Fe and that of K is independent of each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease the Thermal Reserve Zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

  • reaction behavior of formed iron coke and its effect of decreasing Thermal Reserve Zone temperature in blast furnace
    Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2009
    Co-Authors: Seiji Nomura, Kenichi Higuchi, Kazuya Kunitomo, Masaaki Naito
    Abstract:

    Usage of highly reactive coke in order to decrease Thermal Reserve Zone temperature in blast furnace is considered promising to increase reaction efficiency in blast furnace and to decrease reducing agent rate. We focused attention on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. It was shown that when the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the Thermal Reserve Zone temperature (900°C), which causes a decrease in Thermal Reserve Zone temperature, while conventional coke reacts little and is protected from degradation. It was also confirmed that catalytic activity of Fe and that of K is independent each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease Thermal Reserve Zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

  • improvement in blast furnace reaction efficiency through the use of highly reactive calcium rich coke
    Isij International, 2005
    Co-Authors: Seiji Nomura, Hiroyuki Ayukawa, Hisatsugu Kitaguchi, Toshihide Tahara, Shinroku Matsuzaki, Masaaki Naito, Satoshi Koizumi, Yoshikuni Ogata, Takeshi Nakayama, Tetsuya Abe
    Abstract:

    A method to produce coke in ‘lump’ form with high strength and reactivity through the addition of a catalyst was investigated in order to improve blast furnace reaction efficiency. The addition of Ca compounds to coal before carbonization was found to considerably increase the reactivity of the coke at a low temperature range in the Thermal Reserve Zone of a blast furnace. Furthermore it was proved that strong, highly reactive ‘lump’ form coke could be produced by adding a Ca-rich non-caking coal and adjusting the coal blend composition. Based on this fundamental study, the Ca-rich coke was successfully produced in coke ovens on a commercial scale, both at Kimitsu and Muroran works. The use of the Ca-rich coke in the Muroran No. 2 blast furnace was found to cause a decrease in the reducing agent rate by 10 kg/t-p. This technology, producing coke of high reactivity and strength through catalyst addition, is promising as a means of improving the reaction efficiency of a blast furnace.

Wikström Jan-olov - One of the best experts on this subject based on the ideXlab platform.

  • Degradation behaviour of a high CSR coke in an experimental blast furnace : effect of carbon structure and alkali reactions
    2005
    Co-Authors: Hilding Tobias, Bo Bjorkman, Gupta Sushil, Sahajwalla Veena, Wikström Jan-olov
    Abstract:

    A high CSR coke was tested in the LKAB's Experimental Blast Furnace (EBF) at Luleå. The evolution of physical and chemical properties of the centre-line coke samples were analysed by Light Optical Microscopy (LOM), BET N2 absorption and SEM/XRF/XRD. Alkali distribution in the EBF cokes was examined by XRF/SEM and EDS. Thermo Gravimetric Analysis (TGA) was used to measure isoThermal and non-isoThermal CO2 reactivity of the cokes. The crystalline order of carbon and the concentration of alkalis were found to increase as the coke descended through Thermal Reserve Zone to the cohesive Zone of the EBF. The crystallite height (Lc) of EBF coke carbon displayed a linear correlation with the measured EBF temperatures demonstrating the strong effect of temperature on carbon structure of coke in the EBF. Alkali concentration of the coke was increased as it descended into the EBF, and was uniformly distributed throughout the coke matrix. The CO2 reactivity of lower Zone cokes was found to increase when compared to the reactivity of the upper Zones cokes, and was related to the catalytic effect of increased alkalis concentration. The deterioration of coke quality particularly coke strength and abrasion propensity were related to coke graphitisation, alkalization and reactivity. Coke graphitisation is shown to have a strong influence on the coke degradation behaviour in the EBF.Validerad; 2005; 20061210 (ysko

  • Degradation Behaviour of a High CSR Coke in an ExperimentalBlast Furnace: Effect of Carbon Structure and Alkali Reactions
    'Iron and Steel Institute of Japan', 2005
    Co-Authors: Hilding Tobias, Bo Bjorkman, Gupta Sushil, Sahajwalla Veena, Wikström Jan-olov
    Abstract:

    A high CSR coke was tested in the LKAB's Experimental Blast Furnace (EBF) at Luleå. The evolution of physical and chemical properties of the centre-line coke samples were analysed by Light Optical Microscopy (LOM), BET N2 absorption and SEM/XRF/XRD. Alkali distribution in the EBF cokes was examined by XRF/SEM and EDS. Thermo Gravimetric Analysis (TGA) was used to measure isoThermal and non-isoThermal CO2 reactivity of the cokes. The crystalline order of carbon and the concentration of alkalis were found to increase as the coke descended through Thermal Reserve Zone to the cohesive Zone of the EBF. The crystallite height (Lc) of EBF coke carbon displayed a linear correlation with the measured EBF temperatures demonstrating the strong effect of temperature on carbon structure of coke in the EBF. Alkali concentration of the coke was increased as it descended into the EBF, and was uniformly distributed throughout the coke matrix. The CO2 reactivity of lower Zone cokes was found to increase when compared to the reactivity of the upper Zones cokes, and was related to the catalytic effect of increased alkalis concentration. The deterioration of coke quality particularly coke strength and abrasion propensity were related to coke graphitisation, alkalization and reactivity. Coke graphitisation is shown to have a strong influence on the coke degradation behaviour in the EBF.Validerad; 2005; 20061210 (ysko)

Shigeru Ueda - One of the best experts on this subject based on the ideXlab platform.

  • improvement of reactivity of carbon iron ore composite with biomass char for blast furnace
    Isij International, 2009
    Co-Authors: Shigeru Ueda, Kazunari Yanagiya, Kentaro Watanabe, Ryo Inoue, Tatsuro Ariyama
    Abstract:

    Enhancement of reactivity of the burden in the blast furnace can decrease the reducing agent of blast furnace. Besides high reactivity coke, the carbon iron ore composite is considered to be a typical high reactivity burden that can control the Thermal Reserve Zone temperature. Since the reactivity of biomass char is much higher than that of coke, the use of carbon iron ore composite with biomass char will be favorable for decreasing the reducing agent. In the present study the reaction and reducing behavior of the carbon iron ore composite with biomass char were investigated. The gasification rate of biomass char was measured in CO2 atmosphere, and the reaction rate equation of that was derived. The microscopic structure change of biomass during carbonization was experimentally analyzed. According to the experimental results, the reduction of the composite begins at about 550°C in an inert gas atmosphere, and it is much lower than the composite with coke. Analysis of the reaction of carbon iron ore composite was carried out with the reaction model of the carbon iron ore composite based on a lumped system, in which the reaction rate of biomass char and iron ore were installed. The reaction model shows that the biomass char can improve the reduction behavior of the carbon iron ore composite especially in the lower temperature region. Moreover, the influence of gas atmosphere and the optimum structure of the composite were investigated by the model calculation to estimate the optimum condition of the composite in the blast furnace.

  • reaction model and reduction behavior of carbon iron ore composite in blast furnace
    Isij International, 2009
    Co-Authors: Shigeru Ueda, Kazunari Yanagiya, Kentaro Watanabe, Taichi Murakami, Ryo Inoue, Tatsuro Ariyama
    Abstract:

    Decreasing the carbon dioxide emission from steel industries is an important issue. It is considered that due to the high reactivity of carbon iron ore composite, it can control the Thermal Reserve Zone temperature and decrease the consumption of reducing agents in blast furnace. In the present study, a reaction model of the carbon iron ore composite based on a lumped system is proposed to analyze the reduction behavior in the blast furnace. This model is composed of several reaction steps between carbon, iron ore, and gas phase. The carbon solution loss reaction rate of the small particles of reducing agents is determined by the thermogravimetric method. It is found that the gasification of reducing agents is the rate-determining step in the reduction of the carbon iron ore composite. Accordingly, the particle size and reactivity of reducing agents such as coke have an influence on the reduction rate of the carbon iron ore composite. The influence of the gas composition in the atmosphere around the composite on the reduction is analyzed by using the reaction model. Moreover, the reduction behavior of the carbon iron ore composite in the blast furnace is quantitatively examined by comparison of reduction degree and gas composition change in order to investigate the reduction mechanism of reducing agents.