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reduction kinetics of MgO-doped calcium ferrites under CO-N2 atmosphere

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Journal of Iron and Steel Research International 2019年第12期26卷 1265-1272页

作者： Tian-xiong Wang Cheng-yi Ding Xue-wei Lv Sen-wei Xuan Gang Li Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials Chongqing UniversityChongqing 400044China School of Materials Science and Engineering Chongqing UniversityChongqing 400044China

The effect of magnesia on calcium ferrite(***2O3)reduction by CO was examined by isothermal *** of calcium ferrite added with 0,2,4,and 8 wt.%magnesia(abbreviated as CF,CF2M,CF4M,and CF8M)were *** composition was analyzed by X-ray diffraction,and the results indicated that CF2M and CF4M are reduced to lower reduction degree and with lower apparent activation energy than CF;and CF8M with more ***2O3 is reduced to a lower degree and with more difficulty compared with *** rate analysis revealed that CF,CF2M,CF4M,and CF8M reductions are all typical two-step reactions with the order of CF→CWF(***2O3)→*** apparent reduction activation energies of CF,CF2M,CF4M,and CF8M are 46.89,37.30,17.30,and 29.20 kJ/mol,*** analysis depicted that CF2M,CF4M,and CF8M reductions are all described by 2D Avrami–Erofeev(A–E)equation(A2)in the whole process,while CF reduction is first expressed by A2 and then by 3D A–E equation(A3).Different from shrinking core model,a new kinetic model for powdery samples reduction was proposed to illustrate the relationship among reduction rates,reduction routes,and model functions.

关键词： Calcium ferrite Magnesia reduction kinetics reduction model

reduction kinetics of SrFeO_(3−δ)/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial oxidation of methane

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Frontiers of Chemical Science and Engineering 2022年第12期16卷 1726-1734页

作者： Xinhe Wang Liuqing Yang Xiaolin Ji Yunfei Gao Fanxing Li Junshe Zhang Jinjia Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Institute of Clean Coal Technology East China University of Science and TechnologyShanghai 200237China Department of Chemical and Biomolecular Engineering North Carolina State UniversityRaleighNC 27695USA

Chemical looping reforming of methane is a novel and effective approach to convert methane to syngas,in which oxygen transfer is achieved by a redox *** lots of efforts have been made to develop high-performance redox materials,a few studies have focused on the redox *** this work,the kinetics of SrFeO_(3−δ)–CaO∙MnO nanocomposite reduction by methane was investigated both on a thermo-gravimetric analyzer and in a packed-bed *** the methane reduction,combustion occurs before the partial oxidation and there exists a transition between *** weight loss due to combustion increases,but the transition region becomes less inconspicuous as the reduction temperature *** weight loss associated with the partial oxidation is much larger than that with *** rate of weight loss related to the partial oxidation is well fitted by the Avrami–Erofeyev equation with n=3(A3 model)with an activation energy of 59.8 kJ∙mol^(‒1).The rate law for the partial oxidation includes a solid conversion term whose expression is given by the A3 model and a methane pressure-dependent term represented by a power *** partial oxidation is half order with respect to methane *** proposed rate law could well predict the reduction kinetics;thus,it may be used to design and/or analyze a chemical looping reforming reactor.

关键词： chemical looping reforming SrFeO_(3−δ) CaO·MnO nanocomposite reduction kinetics Avrami–Erofeyev model pressure-dependent term

reduction kinetics of Fine Iron Ore Powder in Mixtures of H_2-N_2 and H_2-H_2O-N_2 of Fluidized Bed

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Journal of Iron and Steel Research International 2015年第5期22卷 391-395页

作者： Jian-ming PANG Pei-min GUO Pei ZHAO Center of Efficient Utilization of Resources by Low-temperature Metallurgy China Iron and Steel Research Institute Group

reduction kinetics of fine iron ore powder in different gas mixtures were investigated in high-temperature fluidized bed at a scale of kilograms. Influence of processing parameters, such as particle size, gas flow velocity, height of charge, temperature, compositions of gas mixture, and percentage of inert components, on reduction ki- netics was experimentally determined under the condition of fluidization. The equations for calculating instantaneous and average oxidation rates were deduced. It was found that an increasing H2 O percentage in the gas mixture could obviously decrease the reduction rate because the equilibrium partial pressure of H2 decreased with increasing content of Hz O in the gas mixture and then the driving force of reduction reaction was reduced. When the H2 content was high, .the apparent reaction rate was so rapid when the average size of iron ore fines was less than 1 mm that the re- action temperature can be as low as 750 ℃ ; when the average size of iron ore fines was more than 1 mm, a high re- action temperature of 800 ℃ was required. In addition, it was also found that the content of H2O should be less than 10% for efficient reduction.

关键词： hydrogen fluidized bed fine iron ore powder reduction kinetics

Influence of Size of Hematite Powder on Its reduction kinetics by H_2 at Low Temperature

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Journal of Iron and Steel Research International 2009年第5期16卷 7-11页

作者： PANG Jian-ming GUO Pei-min ZHAO Pei CAO Chao-zhen ZHANG Dian-wei The State Key Laboratory for Advanced Iron and Steel Processes and Materials Central Iron and Steel Research Institute Beijing 100081 China

The reduction kinetics and mechanisms of hematite ore with various particle sizes with hydrogen at low temperature were studied using the thermogravimetric analysis. At the same temperature, after the particle size of powder decreases from 107. 5μm to 2. 0 μm, the surface area of the powder and the contact area between the powder and gas increase, which makes the reduction process of hematite accelerate by about 8 times, and the apparent activation energy of the reduction reaction drops to 36.9 kJ/mol from 78. 3 kJ/mol because the activity of ore powder is improved by refining gradually. With the same reaction rate, the reaction temperature of 6.5 μm powder decreases by about 80 ℃ compared with that of 107. 5 μm powder. Thinner diffusion layer can also accelerate the reaction owing to powder refining. The higher the temperature, the greater is the peak of the reduction rate; at the same temperature, the greater the particle size, the smaller is the peak value of the reduction rate; both inner diffusion and interface chemical reaction play an important role in the whole reaction process.

关键词： iron oxide low temperature reduction kinetics thermogravimetric analysis (TGA), reduction mechanism

Isothermal reduction kinetics of zinc calcine under carbon monoxide

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Transactions of Nonferrous Metals Society of China 2020年第8期30卷 2274-2282页

作者： Yu-jie CHEN Yun-yan WANG Ning PENG Yan-jie LIANG Bing PENG Institute of Environmental Science and Engineering School of Metallurgy and EnvironmentCentral South UniversityChangsha 410083China Chinese National Engineering Research Center for Control&Treatment of Heavy Metal Pollution Changsha 410083China School of Materials Science and Engineering Central South UniversityChangsha 410083China

The reduction kinetics of zinc calcine under a CO atmosphere was evaluated by isothermal reductive roasting in a temperature range of 600-800℃.The extent of reaction of zinc calcine was measured using thermogravimetry(TG),and the decomposition mechanism of zinc ferrite in zinc calcine was analyzed based on variations in the soluble zinc and ferrous *** results indicate that the reaction was controlled by the nucleation of the products,with an apparent activation energy of 65.28 k J/*** partial pressure of CO affected the reaction rate more strongly than the CO intensity(defined as PCO/(PCO+PCO2)).The generation rate of zinc oxide was higher than that of ferrous oxide;therefore,the nucleation of ferrous oxide is the rate-determining step of the reaction.

关键词： reduction kinetics zinc calcine zinc ferrite carbon monoxide

Non-isothermal reduction kinetics of Fe_2O_3-NiO composites for formation of Fe-Ni alloy using carbon monoxide

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Transactions of Nonferrous Metals Society of China 2014年第11期24卷 3710-3715页

作者：李博魏永刚王华昆明理工大学省部共建复杂有色金属资源清洁利用国家重点实验室昆明650093

The non-isothermal reduction kinetics and mechanism of Fe2O3-NiO composites with different Fe2O3-NiO compacts using carbon monoxide as reductant were investigated. The results show that the reduction degree increases rapidly with increasing the content of NiO, and the presence of NiO also improves the reduction rate of iron oxides. It is found that NiO is preferentially reduced at the beginning of the reactions, and then the metallic Ni acts as a catalyst promoting the reduction rate of iron oxides. It is also observed that the increase of the Ni O content enhances the formation of awaruite(FeNi3) but decreases the percentage of kamacite(Fe,Ni) and taenite(Fe,Ni). The particle size of the materials tends to be uniform during the reduction process due to the presence of metallic nickel, metallic iron and the formation of Fe-Ni alloy. The concentration of CO in the product gas is greater than that of CO2 at the beginning of the reaction and then slows down. The fastest reduction rate of Fe2O3-NiO composites with CO appears at 400-500 °C, and nucleation growth model can be used to elucidate the reduction mechanism. Nucleation growth process is found to be the rate controlling step when the temperature is lower than 1000 °C.

关键词： reduction kinetics Fe2O3 NiO Fe-Ni alloy carbon monoxide

Solid-state reduction kinetics and mechanism of pre-oxidized vanadium-titanium magnetite concentrate

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Transactions of Nonferrous Metals Society of China 2014年第10期24卷 3372-3377页

作者：刘水石郭宇峰邱冠周姜涛陈凤中南大学资源加工与生物工程学院长沙410083

The solid-state reduction kinetics of pre-oxidized vanadium-titanium magnetite concentrate was studied. The phase and microstructure of the reduction product were characterized by XRD, SEM and EDS methods, based on which the mechanism of the solid-state reduction was investigated. The results showed that using coal as reductant at 950-1100 °C, the solid-state reduction of the pre-oxidized vanadium-titanium magnetite concentrate was controlled by interface chemical reaction and the apparent activation energy was 67.719 k J/mol. The mineral phase transformation during the reduction process can be described as follows： pre-oxidized vanadium-titanium magnetite concentrate → ulvospinel → ilmenite → Fe Ti2O5 →（FenTi1-n）Ti2O5. M3O5-type（M can be Fe, Ti, Mg, Mn, etc） solid solutions would be formed during the reduction process of the pre-oxidized vanadium-titanium magnetite concentrate at 1050 °C for 60 min. The poor reducibility of iron in M3O5 solid solutions is the main reason to limit the reduction property of pre-oxidized vanadium-titanium magnetite concentrate.

关键词： vanadium-titanium magnetite solid-state reduction reduction kinetics reduction process

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

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International Journal of Minerals,Metallurgy and Materials 2015年第10期22卷 1025-1032页

作者： Ru-fei Wei Da-qiang Cang Ling-ling Zhang Yuan-yuan Bai School of Metallurgical and Ecological Engineering University of Science and Technology Beijing State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing School of Civil and Environmental Engineering University of Science and Technology Beijing Key Laboratory of Electromagnetic Processing of Materials of the Ministry of Education Northeastern University

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction（XRD）, and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional（model-free） methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→Fe O, and Fe O→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2content in the Fe2O3→Fe3O4stage but is substantially greater than the CO2 contents in the Fe3O4→Fe O and Fe O→Fe stages, where gasification starts at approximately 1205 K. The activation energy（E） of the three stages are 126–309 k J/mol, 628 k J/mol, and 648 k J/mol, respectively. The restrictive step of the total reduction is Fe O→Fe. If the rate of the total reduction is to be improved, the rate of the Fe O→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.

关键词： iron oxides direct reduction reduction kinetics re

kinetics OF reduction IRON OXIDE IN CaO-SiO_2-Al_2O_3-Fe_tO SLAGS WITH CARBON SATURATED IN MOLTEN IRON

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Acta Metallurgica Sinica(English Letters) 1997年第6期10卷 515-522页

作者： X.M. Yang D.B. Huang L. T. Kong T.J. Yang Y.S. Xie and D. G. Wang(Institute of Chemical Metallurgy, Chinese Academy of Sciences, Beijing 100080, China)(University of Science and Technology Beijing, Beijing 100083, China) Inst of Chemical Metallurgy Chinese Acad of Sciences Beijing China

The rate of reducing Fet O in CaO-SiO2-Al2O3-Fet O slags with carbon saturated in molten iron has been determined in a graphite crucible in the temperature range of 1673-1773K. The effects of temperature, slag basicity and FetO content on the reduction rate have also been discussed. Test results show that the reduction rate increases with increasing temperature or FEtO concentration in slags, and the reduction rate has a parabolic relation with the simple basicity or optical basicity of slag, the maximum reduction rate being observed at around CaO/SiO2=1.5 of molten slags. The reduction reaction order is 1. 73 or 1.80, and the reduction activation energy is 299.9 or 295.9 kJ/mol in regard to Fet O weight content or Fet O activity calculated by using regular solution model, respectively. The reduction rate of CaO-SiO2-Al2 O3-Fet O slags with carbon saturated in molten iron is in the range of 0.32-3.48 mol-O/cm2·s.

关键词： CaO-SiO_2-Al_2O_3-Fe_tO slags reduction kinetics molten iron,Fe_tO activity