Gas–Solid Reduction Behavior of In‐flight Fine Hematite Ore Particles by Hydrogen

Xing, Liyong; Zou, Zongshu; Shao, Lei; Zou, Jiaqi

doi:10.1002/srin.201800311

Cited by 20 publications

(6 citation statements)

References 33 publications

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“…With the gradual depletion of high-quality lump iron ore resources around the world, the efficient use of fine ore resources obtained after mineral processing has received wide attention in the iron-making industry [1][2][3][4]. Getting rid of the process of sintering and agglomeration, the direct reduction process using iron ore fines directly has many advantages such as high efficiency, energy saving, and environmental protection.…”

Section: Introductionmentioning

confidence: 99%

Nucleation and Growth of Iron Whiskers during Gaseous Reduction of Hematite Iron Ore Fines

Guo

Zhong

Bao

et al. 2019

Metals

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A high-temperature confocal scanning laser microscope and an online reduction–water quenching experiment system were used to systematically study the generation of iron whiskers during the reduction of hematite ore particles with CO/CO2 gas. The "blooming" phenomenon of the surface during the reduction of iron ore particles was found in this experiment. The orientation of the grain on the longitudinal section of an iron whisker was measured to be uniform by applying the electron back-scattered diffraction technique, which proved that the iron whiskers are most likely to exist in single crystal form. According to the in-situ online experimental video, the average diffusion flux of iron atoms when the layered iron completely covers the surface of the ore particle is about 0.0072 mol/(m2·s). While the iron atom diffusion flux at the root of the iron whisker during the pre-growth process is much larger than the flux when the layered iron is produced, which are defined to be 0.081 mol/(m2·s), 0.045 mol/(m2·s), 0.013 mol/(m2· s), and 0.0046 mol/(m2·s), respectively during the four stages of the growth of an iron whisker. The quantitative relationship between the chemical driving force and the whisker growth is established as Δ G θ + R T ln p CO 2 p CO + 2 n 0.056 r ρ E s T = 0 .

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Section: Introductionmentioning

confidence: 99%

Nucleation and Growth of Iron Whiskers during Gaseous Reduction of Hematite Iron Ore Fines

Guo

Zhong

Bao

et al. 2019

Metals

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“…On the basis of thermodynamics, since water vapor is the substance produced by the reduction reaction, the large amount of water vapor will cause Delta G of the reaction to increase, and the tendency of the forward reaction to decrease. In terms of kinetics, since the viscosity of water vapor at the same temperature is greater than that of hydrogen, this will cause the gas diffusion coefficient of the gas reactant to decrease, making gas mass transfer difficult [27][28].…”

Section: Effect Of Water On the Reaction Ratementioning

confidence: 99%

Effect of water vapor on the reduction kinetics of hematite powder by hydrogen-water vapor in different stages

Mao

Fan

et al. 2023

J min metall B Metall

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The powder of hematite sample was isothermally reduced with hydrogen-water vapor gas mixture at 1023K-1273K. The results indicated that the overall reduction process of hematite could be separated into three stages (Fe2O3-Fe3O4-FeO-Fe) to respectively study. At 1023K, the average reaction rate dropped by 53.6% in the stage 1 when the water vapor content of gas reactant rose from 0% to 50%, and it decreased by about 77.2% in the stage 2. However, in the stage 3, when the water vapor content only increased from 0% to 20%, it decreased by about 78.1%. Besides, the average reaction rate had a roughly negative linear relationship with the water vapor content, and the results further shown that the effect of water vapor on the reduction reaction increased with increasing reaction temperature at all stages of the reduction reaction. The microstructure of reduction products showed that it still had some holes, which the channel for hydrogen diffusion was not seriously blocked. In order to further clarify the influence of water vapor in the reduction stage, different models were considered, and the range of apparent activation energy of different stages obtained by model fitting was about 20-70 kJ/mol, which also confirmed the absence of solid-state diffusion phenomenon.

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“…Nowadays, the gas–solid reduction technique is widely applied in ironmaking processes, in order to produce directly reduced iron (DRI) or so-called sponge iron for special steel production [ 29 , 30 , 31 , 32 , 33 ]. In this process, iron oxide (Fe 2 O 3 ) is directly reduced with H 2 and/or CO to metallic iron, via intermediate reaction products (magnetite and/or wűstite) at relatively low temperatures.…”

Section: Introductionmentioning

confidence: 99%

A Novel Hydro-Thermal Synthesis of Nano-Structured Molybdenum-Iron Intermetallic Alloys at Relatively Low Temperatures

2023

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Nano-structured Mo/Fe intermetallics were synthesized from precursors that contained 72/28% and 30/70% molar ratios of Mo/Fe, which were given as precursors A and B, respectively. These precursors were prepared from the co-precipitation of aqueous hot solutions of ammonium heptamolybdate tetrahydrate (AHM) and ferrous oxalate. The dry precipitates were thermally treated using TG-DSC to follow up their behavior during roasting, in an Ar atmosphere of up to 700 °C (10° K/min). The TG profile showed that 32.5% and 55.5% weight losses were measured from the thermal treatment of precursors A and B, respectively. The DSC heat flow profile showed the presence of endothermic peaks at 196.9 and 392.5–400 °C during the thermal decomposition of the AHM and ferrous oxalate, respectively. The exothermic peak that was detected at 427.5 °C was due to the production of nano-sized iron molybdate [Fe2(MoO4)3]. An XRD phase analysis indicated that iron molybdate was the only phase that was identified in precursor A, while iron molybdate and Fe2O3 were produced in precursor B. Compacts were made from the pressing of the nano-sized precursors, which were roasted at 500 °C for 3 h. The roasted compacts were isothermally reduced in H2 at 600–850 °C using microbalance, and the O2 weight loss that resulted from the reduction reactions was continuously recorded as a function of time. The influence of the reduction temperature and precursor composition on the reduction behavior of the precursors was studied and discussed. The partially and completely reduced compacts were examined with X-ray powder diffraction (XRD), a reflected light microscope (RLM), and a scanning electron microscope (SEM-EDS). Depending on the precursor composition, the reduction reactions of the [Fe2(MoO4)3] and Fe2O3 proceeded through the formation of intermediate lower oxides, prior to the production of the MO/Fe intermetallic alloys. Based on the intermediate phases that were identified and characterized at the early, intermediate, and final reduction degrees, chemical reaction equations were given to follow up the formation of the MoFe and MoFe3 intermetallic alloys. The mechanism of the reduction reactions was predicted from the apparent activation energy values (Ea) that were computed at the different reduction degrees. Moreover, mathematical formulations that were derived from the gas–solid reaction model were applied to confirm the reduction mechanisms, which were greatly dependent on the precursor composition and reduction temperature. However, it can be reported that nano-structured MoFe and MoFe3 intermetallic alloys can be successfully fabricated via a gas–solid reaction technique at lower temperatures.

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Gas–Solid Reduction Behavior of In‐flight Fine Hematite Ore Particles by Hydrogen

Cited by 20 publications

References 33 publications

Nucleation and Growth of Iron Whiskers during Gaseous Reduction of Hematite Iron Ore Fines

Nucleation and Growth of Iron Whiskers during Gaseous Reduction of Hematite Iron Ore Fines

Effect of water vapor on the reduction kinetics of hematite powder by hydrogen-water vapor in different stages

A Novel Hydro-Thermal Synthesis of Nano-Structured Molybdenum-Iron Intermetallic Alloys at Relatively Low Temperatures

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