Microstructural Changes and Kinetics of Reduction of Hematite to Magnetite in CO/CO2 Gas Atmospheres

Chen, Jiang; Zhang, Ruihan; Simmonds, Tegan; Hayes, Peter C.

doi:10.1007/s11663-019-01659-0

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…Microwave irradiation proves to be the most effective way to improve both the initial reduction rate and that exhibited during the primary iron crystal precipitation phase. Jiang Chen [25] found that the formation of porous iron by CO reduction is rel to CO partial pressure and reduction temperature. However, under the experimental ditions of the present study, the reduced iron is a dense punctate.…”

Section: Microkineticsmentioning

confidence: 99%

“…However, under the experimental ditions of the present study, the reduced iron is a dense punctate. The morphology of crystals may be essentially controlled by the ratio of diffusion rate to reaction rate [19 Jiang Chen [25] found that the formation of porous iron by CO reduction is related to CO partial pressure and reduction temperature. However, under the experimental conditions of the present study, the reduced iron is a dense punctate.…”

Section: Microkineticsmentioning

confidence: 99%

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Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

Zhou,

Ai,

Hong

et al. 2023

Processes

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To investigate the effect of microwave irradiation on the rate of magnetite reduction while increasing the gas phase diffusion rate limit, the microstructure and kinetics of CO reduction of magnetite powder were studied. The investigation was conducted through microwave irradiation and conventional heating at 900~1100 °C. Under the two heating methods, the iron crystal is selectively reduced and gradually expanded along the direction normal to the length of the ore powder, forming a strip of iron crystal that penetrates the powder and expands outward across the width. The microwave field can effectively improve the sintering of minerals. The changes in Avrami exponents m and k in the reduction process were determined by combining the Johnson–Mehl–Avrami (JMA) model with the lnln method. The microwave field did not change the limiting step. Microwave irradiation proves to be the most effective means to enhance both the initial reduction rate and the rate during the primary iron crystal precipitation phase. The morphology of the iron crystal takes on a dense punctate shape, influenced by the rate of diffusion control.

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Section: Microkineticsmentioning

confidence: 99%

Section: Microkineticsmentioning

confidence: 99%

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

Zhou,

Ai,

Hong

et al. 2023

Processes

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show abstract

“…In order to calculate the conversion of the reduction reaction, chemical analysis was adopted to determine the FeO content of reduction products. The detailed detection process was in accordance with our previous study [23]. X-ray diffraction detection (PW3040, Philips Co., The Netherlands) was used to characterize the phase transformation of the reduction products.…”

Section: Sample Characterizationmentioning

confidence: 99%

“…Reduction kinetics have been considered one of the most efficient ways to evaluate the reduction process, and it is very meaningful for the application of reduction kinetics to analyze the reduction behavior of the mineral and thereby to understand and optimize the reduction process. In this study, thirty common reduction kinetic models (Table 2) were used to fit and determine the most probable reduction mechanism model of hematite under different conditions [23].…”

Section: Influence Of Naoh Content On the Reduction Kinetics Of Hematitementioning

confidence: 99%

Effects of NaOH Content on the Reduction Kinetics of Hematite by Using Suspension Magnetization Roasting Technology

Yuan

Wang

et al. 2022

Minerals

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Red mud is a potential iron resource that needs to be urgently exploited and utilized. However, due to the properties of high alkalinity, fine particle size and complex mineral composition, the utilization of red mud is difficult. Focusing on red mud’s prominent feature of high alkalinity, this paper studies the influence of NaOH content on the reduction kinetics of hematite, which is the main component of red mud. The results show that the conversion degree of hematite was strongly inhibited by NaOH, and the magnetization and specific magnetic susceptibility of reduction products was significantly decreased with the increase in NaOH content. Meanwhile, the results of the calculation of kinetics parameters demonstrate that the addition of NaOH did not affect the control step of the reduction of hematite, while it dramatically decreased the reduction rate of hematite. Moreover, thermodynamic analysis and SEM-EDS detection were conducted to uncover the inhibited mechanism of NaOH on the reduction of hematite, which indicated that sodium ferrite could be produced spontaneously under the experimental conditions and that it is hard for it to be further reduced by CO. Furthermore, the produced sodium ferrite formed a dense film, which covered the surface of the hematite particles, inhibiting the diffusion of CO and thereby hindering the reduction of the interior hematite.

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“…After the magnetization roasting process, the original hematite particles became porous after reduction to magnetite, and fresh magnetite nuclei formed preferentially at the edges of the original hematite particles [29]. Using high-resolution scanning electron microscopy, Chen et al [30] found that microstructures of cellular porous and dendritic porous magnetite formed by hematite reduction. Strezov et al [31], using laser light scattering apparatus, found that some cracks initiated on the surface of goethite particles with crack propagation from the surface down to 20% of the particle diameter.…”

Section: Introductionmentioning

confidence: 99%

The Efficient Improvement of Original Magnetite in Iron Ore Reduction Reaction in Magnetization Roasting Process and Mechanism Analysis by In Situ and Continuous Image Capture

et al. 2021

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Magnetization roasting followed by magnetic separation is considered an effective method for recovering iron minerals. As hematite and magnetite are the main concomitant constituents in iron ores, the separation index after the magnetization roasting will be more optimized than with only hematite. In this research, the mechanism of the original magnetite improving iron ore reduction during the magnetization roasting process was explored using ore fines and lump ore samples. Under optimum roasting conditions, the iron grade increased from 62.17% to 65.22%, and iron recovery increased from 84.02% to 92.02% after separation, when Fe in the original magnetite content increased from 0.31% to 8.09%, although the Fe masses in each sample were equal. For lump ores with magnetite and hematite intergrowth, the method of in situ and continuous image capture for microcrack generation and the evolution of the magnetization roasting process was innovatively examined with a laser scanning confocal microscope (LSCM) with confocal technology and 3D morphologic technology for the first time. The naturally uneven areas, protogenetic pore edges, and magnetite and hematite edges provided active sites for reduction reactions. The microcracks gradually evolved from the lump ore surface and the edges of magnetite and hematite, which had a direct connection with the efficient improvement in ore reduction.

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Microstructural Changes and Kinetics of Reduction of Hematite to Magnetite in CO/CO2 Gas Atmospheres

Cited by 12 publications

References 15 publications

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

Effects of NaOH Content on the Reduction Kinetics of Hematite by Using Suspension Magnetization Roasting Technology

The Efficient Improvement of Original Magnetite in Iron Ore Reduction Reaction in Magnetization Roasting Process and Mechanism Analysis by In Situ and Continuous Image Capture

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