Effect of Metal Additions to the Reduction of Iron Oxide Composite Pellets with Hydrogen at Moderate Temperatures
TL;DR: In this paper, the hydrogen reduction behavior of iron oxide composite pellets containing Ni, Fe, and Mn was compared with iron oxide and Al2O3 containing reference composite pellets to determine the effect of metallic species on the kinetics of IR reduction.
Abstract: The hydrogen reduction behavior of iron oxide composite pellets containing Ni, Fe, and Mn from 973 K to 1173 K was compared with iron oxide and Al2O3 containing reference composite pellets to determine the effect of metallic species on the kinetics of iron oxide reduction. The Mn and Ni containing pellets showed slightly faster initial reduction rates compared to the Fe and Al2O3 containing pellets. The effect of the metal phases was found to be more significant at lower temperatures when chemical reaction at the interface is a slower and more controlling factor. From the SEM of partially reduced pellets, a wide intermediate region between an O rich unreacted core and an Fe rich outer shell was observed. Although an initially short topochemical receding interface controlled region exists, the mixed control between the topochemical receding interface and pore diffusion was prevalent. For Fe2O3/Mn composite pellets, the thermodynamic stability of the MnO is higher and Mn can act as a reductant for iron oxide. Thus, the overall metallization of the Fe2O3/Mn composite pellets decreased compared to the other Fe2O3/metal composite pellets. From the temperature dependence of the iron-oxide/metal composite pellets, the apparent activation energy was calculated to be approximately between 15 to 20 kJ/mol, which is typical of a mixed control reduction mechanism of gas diffusion and interface reaction.
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TL;DR: In this paper, both isothermal and non-isothermal reduction experiments of Panzhihua ilmenite powders by pure hydrogen were carried out using a thermo-gravimetric (TG) analyzer.
40 citations
TL;DR: In this article, a new kinetic model has been developed for reduction of metal oxides with hydrogen under both isothermal and non-isothermal conditions, which is in the analytic form of expressing the reduction extent as an explicit function of time, temperature, radius of the particle, and hydrogen partial pressure.
Abstract: In this paper, a new kinetic model has been developed for reduction of metal oxides with hydrogen under both isothermal and non-isothermal conditions. This model describes the kinetics of single reductive reaction and double reductive reactions by considering the diffusion and chemical reaction controlling mechanisms. In particular, the model is in the analytic form of expressing the reduction extent as an explicit function of time, temperature, radius of the particle, and hydrogen partial pressure, which is convenient for using and theoretical analysis. The reduction kinetics of nickel oxide, natural ilmenite, and Fe2MoO4 agree well with the theoretical results by the present model.
35 citations
30 Jan 2017-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the reduction kinetics of Brazilian hematite by CO are investigated in a Micro Fluidized Bed Reaction Analyzer (MFBRA) using an analyzing method based on Johnson-Mehl-Avrami (JMA) model at temperatures of 973 K (700 K), 1023 K (750 K), and 1123 K (850 K).
Abstract: The reduction kinetics of Brazilian hematite by CO is investigated in a Micro Fluidized Bed Reaction Analyzer (MFBRA) using an analyzing method based on Johnson-Mehl-Avrami (JMA) model at temperatures of 973 K (700 °C), 1023 K (750 °C), 1073 K (800 °C), and 1123 K (850 °C). The solid products at different reduction stages are evaluated by SEM/EDS and XRD technologies. Results indicate that the reduction process is better to be discussed in terms of a parallel reaction model that consists of the reactions of hematite to wustite and wustite to iron, rather than a stepwise route. Meanwhile, the controlling mechanism of the reduction process is found to vary with temperature and the degree of conversion. The overall process is controlled by the gas–solid reaction occurring at the iron/wustite interface in the initial stages, and then is limited by the nucleation of wustite, and finally shifts to diffusion control. Moreover, the reactions of hematite to wustite and wustite to iron take place simultaneously but with different time dependences, and the apparent activation energies of hematite to wustite and wustite to iron are determined as 83.61 and 80.40 KJ/mol, respectively.
19 citations
TL;DR: In this paper, the reduction kinetics of Hongge vanadium titanomagnetite (HVTM)-oxidized pellet with simulated gas compositions of dry pulverized coal gasification (DPCG), water-coal slurry gasification, Midrex, and HYL-III are investigated.
Abstract: The reduction kinetics of Hongge vanadium titanomagnetite (HVTM)-oxidized pellet with simulated gas compositions of dry pulverized coal gasification (DPCG), water-coal slurry gasification (WCSG), Midrex, and HYL-III is investigated in the current study. The experiments are carried out at temperatures ranging from 900 to 1050 °C, simulating the reduction zone in gas-based shaft furnace direct reduction processes. The reduction degree is the highest when reduced with the gas composition of HYL-III while the lowest when reduced with DPCG. The reduction degree, as well as the reaction rate constant and effective diffusion coefficient, is found to decrease in the order of HYL-III > Midrex > WCSG > DPCG. The reduction process is controlled by interfacial chemical reaction at initial stage and by both interfacial chemical reaction and internal diffusion at later stage. The scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) are used to estimate the reduction mechanism of HVTM-oxidized pellet with different gas compositions. This study aims to obtain scientific direction for reactor design and operational parameter determination of gas-based shaft furnace, as well as provide both theoretical and technical basis for the comprehensive utilization of HVTM.
15 citations
TL;DR: In this paper, the authors summarize the fundamentals of reduction kinetics of iron ore-coal composite pellet and the effect of various process parameters such as compositions, particle size, pellet geometry, ambient atmosphere and its partial pressure, heating conditions, and compaction pressure on it.
Abstract: The use of iron ore–coal composite pellet as a raw material for iron making is an ongoing area of research. Investigations on composite pellet reduction have reported some interesting phenomena, and experimental and modeling results, in which consistent and inconsistent conclusions have been presented in the literature. The aim of this review is to summarize the fundamentals of reduction kinetics of iron ore–coal composite pellet and the effect of various process parameters such as compositions, particle size, pellet geometry, ambient atmosphere and its partial pressure, heating conditions, and compaction pressure, etc., on it. The industrial application of composite pellet is also discussed. This article will be useful for the researchers carrying out experimental as well as modeling work related to the iron oxide–carbon composite pellet reduction.
8 citations
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28,685 citations
TL;DR: In this article, the authors review the current knowledge about the relationship between the micro-structure of cold rolled intercritically annealed low-alloy TRIP-aided sheet steels and their mechanical properties from a materials engineering point of view.
Abstract: The purpose of the present contribution is to review the current knowledge about the relationship between the micro-structure of cold rolled intercritically annealed low alloy TRIP-aided sheet steels and their mechanical properties from a materials engineering point of view. The focus is on their production in existing industrial lines and on their application in the manufacture of passenger cars with a body-in-white which offers an improved passive safety. The review aims to make clear that although low alloy TRIP-aided sheet steel is by now starting to be an established structural material in BIW manufacturing, there is still room for the further optimization of the composition and the processing. In addition, there are still a number of problems related to their physical metallurgy that require a better fundamental understanding.
753 citations
01 Mar 1977-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the rate of reduction of Fe2O3 and FeO by coconut charcoal, coal char and coke, in an inert atmosphere within the temperature range 900 to 1200°C was investigated.
Abstract: The rate of reduction of Fe2O3 and FeO by coconut charcoal, coal char and coke, in an inert atmosphere within the temperature range 900 to 1200°C was investigated. The effects of pressure, particle size, and the amount of carbon were determined. The results indicate that the reaction takes place by means of the gaseous intermediates CO and CO2, and that the overall rate is controlled by the oxidation of the carbon by CO2. The rates of reduction of FeO and Fe2O3 by CO are relatively fast, and the CO2/CO ratio for the oxidation of carbon is determined by their equilibria. The reduction of Fe2O3 by carbon is accomplished in two stages, with FeO forming first. The reduction of Fe2O3 to FeO is faster than that of FeO to Fe because its CO2/CO equilibrium ratio is higher and hence the rate of oxidation of carbon is faster. A direct comparison was made between the rate constants for the reduction of FeO by carbon and those for the oxidation of carbon in the appropriate CO2-CO gas mixtures, and they are in good agreement. Apparently the iron formed by the reduction does not significantly catalyze the oxidation of carbon; whereas for the reduction of NiO by carbon, the Ni formed does catalyze the oxidation of carbon.
195 citations
TL;DR: In this paper, the reduction of WO 3 by H 2 to a blue form proceeds readily above 400°C and the acceleration by water is ascribed to a marked increase in the rate of diffusion of the reducing species.
168 citations
TL;DR: In this article, the hydrogen reduction of pure α-Fe 2 O 3 doped with foreign metal oxides employing a sensitive micro-gravimetric technique was carried out by a consecutive two-step mechanism via Fe 3 O 4, the overall rate being controlled by the topochemical reduction of Fe 3 o 4 while that of doped oxides and hematite ore takes place by a different mechanism involving the mixed ferrite formed.
119 citations