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Isothermal reduction of titanomagnetite concentrates containing coal

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International Journal of Minerals,Metallurgy and Materials 2014年第2期21卷 131-137页

作者： Tu Hu xue-wei lü Chen-guang Bai Gui-bao Qiu College of Materials Science and Engineering Chongqing University Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology

The isothermal reduction of the Panzhihua titanomagnetite concentrates （PTC） briquette containing coal under argon atmosphere was investigated by thermogravimetry in an electric resistance furnace within the temperature range of 1250-1350°C. The samples reduced in argon at 1350°C for different time were examined by X-ray diffraction （XRD） analysis. Model-fitting and model-free methods were used to evaluate the apparent activation energy of the reduction reaction. It is found that the reduction rate is very fast at the early stage, and then, at a later stage, the reduction rate becomes slow and decreases gradually to the end of the reduction. It is also observed that the reduction of PTC by coal depends greatly on the temperature. At high temperatures, the reduction degree reaches high values faster and the final value achieved is higher than at low temperatures. The final phase composition of the reduced PTC-coal briquette consists in iron and fer-rous-pseudobrookite （FeTi2O5）, while Fe2.75Ti0.25O4, Fe2.5Ti0.5O4, Fe2.25Ti0.75O4, ilmenite （FeTiO3） and wustite （FeO） are intermediate products. The reaction rate is controlled by the phase boundary reaction for reduction degree less than 0.2 with an apparent activation energy of about 68 kJ·mol-1 and by three-dimensional diffusion for reduction degree greater than 0.75 with an apparent activation energy of about 134 kJ·mol-1. For the reduction degree in the range of 0.2-0.75, the reaction rate is under mixed control, and the activation energy increases with the increase of the reduction degree.

关键词： titanomagnetite carbothermal reduction thermogravimetric analysis kinetics

Oxidation pathway and kinetics of titania slag powders during cooling process in air

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 981-990页

作者： Wen-chao He xue-wei lü Cheng-yi Ding Zhi-ming Yan School of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China State Key laboratory of Mechanical Transmissions Chongqing UniversityChongqing 400044China Chongqing Key laboratory of Vanadium-Titanium Metallurgy and New Materials Chongqing UniversityChongqing 400044China College of Metallurgical Engineering Anhui University of TechnologyMa’anshan 243002China WMG University of WarwickCoventryCV47ALUK

The oxidation pathway and kinetics of titania slag powders in air were analyzed using differential scanning calorimetry(DSC)and thermogravimetry(TG).The oxidation pathway of titania slag powder in air was divided into three stages according to their three exothermic peaks and three corresponding mass gain stages indicated by the respective non-isothermal DSC and TG *** isothermal oxidation kinetics of high titania slag powders of different sizes were analyzed using the ln-ln analysis *** results revealed that the entire isothermal oxidation process comprises two *** kinetic mechanism of the first stage can be described as f(α) = 1.77(1-α) [-ln (1-α)]^((1.77-1)/1.77),f(α)= 1.97(1-α) [-ln (1-α)]^((1.97-1)/1.97),and f (α) = 1.18(1-α) [-ln (1-α)]^((1.18-1)/1.18).The kinetic mechanism of the second stage for all samples can be described as f (α)=1.5(1-α)^(2/3)[1-(1-α)^(1/3)]^(-1).The activation energies of titania slag powders with different sizes(d_(1)l conditions,the rate-controlling step in the first oxidation stage of all the samples is a chemical *** rate-controlling steps of the second oxidation stage are a chemical reaction and internal diffusion(for powders d_(1)l diffusion(for powders 0.125 mm

关键词： high titania slag powder oxidation pathway isothermal oxidation kinetics ln-ln analysis activation energy rate-controlling step

Isothermal reduction kinetics of Panzhihua ilmenite concentrate under 30vol% CO–70vol% N2 atmosphere

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International Journal of Minerals,Metallurgy and Materials 2017年第3期24卷 240-248页

作者： Ying-yi Zhang wei lü xue-wei lü Sheng-ping li Chen-guang Bai Bing Song Ke-xi Han College of Materials Science and Engineering Chongqing University Chongqing 400044 China Panzhihua Iron and Steel Research Institute Panzhihua 617000 China

The reduction of ilmenite concentrate in 30vol% CO–70vol% N_2 atmosphere was characterized by thermogravimetric and differential thermogravimetric(TG–DTG) analysis methods at temperatures from 1073 to 1223 *** isothermal reduction results show that the reduction process comprised two stages;the corresponding apparent activation energy was obtained by the iso-conversional and model-fitting *** the first stage,the effect of temperature on the conversion degree was not obvious,the phase boundary chemical reaction was the controlling step,with an apparent activation energy of 15.55–40.71 k J·mol^(–1).For the second stage,when the temperatures was greater than 1123 K,the reaction rate and the conversion degree increased sharply with increasing temperature,and random nucleation and subsequent growth were the controlling steps,with an apparent activation energy ranging from 182.33 to 195.95 k J·mol^(–1).For the whole reduction process,the average activation energy and pre-exponential factor were 98.94^(–1)18.33 k J·mol^(–1) and 1.820^(–1).816 min^(–1),respectively.

关键词： ilmenite isothermal reduction kinetics carbon monoxide

Effect of cooling rate on the crystallization behavior of perovskite in high titanium-bearing blast furnace slag

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International Journal of Minerals,Metallurgy and Materials 2014年第11期21卷 1052-1061页

作者： lu liu Mei-long Hu Chen-guang Bai xue-wei lü Yu-zhou Xu Qing-yu Deng College of Materials Science and Engineering Chongqing University

The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace（BF） slag was studied using confocal scanning laser microscopy（CSlM）. Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O^2-, when Ti2O3 was involved in the formation of perovskite.

关键词： blast furnace slag perovskite crystallization cooling rate

Solid-state reaction of a CaO−V_(2)O_(5)mixture:A fundamental study for the vanadium extraction process

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International Journal of Minerals,Metallurgy and Materials 2021年第9期28卷 1462-1468页

作者： Jun-yi Xiang Xin Wang Gui-shang Pei Qing-yun Huang xue-wei lv College of Materials Science and Engineering Chongqing UniversityChongqing 400044China School of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China Chongqing Key laboratory of Vanadium-Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China

The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery *** analysis,X-ray diffraction spectroscopy,scanning electron microscopy,and energy dispersive spectrometry were used to characterize the solid-state reaction of the *** extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray *** results indicate that the solid reaction of the CaO−V_(2)O_(5)mixture is strongly influenced by the reaction temperature and CaO/V_(2)O_(5)mole *** transformation of calcium vanadate in-volves a step-by-step reaction of CaO−V_(2)O_(5),CaO−CaV_(2)O_(6),and CaO−Ca_(2)V_(2)O7 depending on the CaO/V_(2)O_(5)mole *** kinetic data of the solid reaction of the CaO−V_(2)O_(5)(1:1)mixture followed a second-order reaction *** activation energy(Ea)and preexponential factor(A)were determined to be 145.38 kJ/mol,and 3.67×10^(8)min^(−1),respectively.

关键词： calcium vanadate vanadium extraction solid-state reaction kinetics

Effect of titanium content on the precipitation behavior of carbon-saturated molten pig iron

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International Journal of Minerals,Metallurgy and Materials 2019年第4期26卷 483-492页

作者： lei-zhang Gao Tong-xiang Ma Meng-jun Hu Zhi-ming Yan xue-wei lü Mei-long Hu College of Materials Science and Engineering Chongqing University Chongqing Key laboratory of Vanadium-Titanium Metallurgy and New Materials

The use of iron ores bearing titanium as a raw material is an effective measure to prevent hearth erosion and prolong the life of a blast furnace. In this research, the effect of titanium content on the precipitation behaviors of high-melting phases of carbon-saturated molten pig iron were studied by confocal scanning laser microscopy. The results showed that, when the titanium content was less than 0.25 wt%,Fe_3C was precipitated as a single phase from the molten carbon-saturated iron. The growth rate of the precipitated Fe_3C crystals was very high, reaching 7387 μm^2/s. When the titanium content in the molten pig iron was greater than 0.47 wt%, TiC crystals precipitated first. The shape and size of the precipitated TiC crystals did not obviously change. After TiC was precipitated, the fluidity of the molten pig iron worsened. With a decrease in temperature, Fe_3C was also precipitated but the growth rate of Fe_3C was limited by the presence of the first precipitated TiC phase. The crystal size of the precipitated Fe_3C was much smaller than that of pure Fe_3C.

关键词： carbon-saturated molten pig iron precipitation behavior titanium titanium carbide confocal scanning laser microscopy

Effect of sodium carbonate addition on carbothermic reduction of ilmenite concentrate

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Transactions of Nonferrous Metals Society of China 2022年第3期32卷 1010-1018页

作者： Xiao-dong lÜ Dan CHEN Yun-tao XIN wei lÜ xue-wei lü College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Chongqing Key laboratory of Vanadium−Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China

The enhanced reduction mechanism and kinetics of different Na_(2)CO_(3) additions in the carbothermic reduction of ilmenite concentrate were *** reduction process was carried out at different heating rates in a thermogravimetry facility,and the kinetics was studied using the Starink *** results indicate that Na_(2)CO_(3) addition enhanced the reduction effect as well as reduced the initial temperature of the reaction and the activation energy by increasing reactant activity in reactant form;however,it deteriorated the late-stage kinetic conditions by generating a molten phase,thereby reducing the reaction rate in the late stages of *** average apparent activation energies of ilmenite concentrate with 0%,3%,and 6%Na_(2)CO_(3) are 447,289,and 430 kJ/mol,*** results from kinetics parameters confirm that Na_(2)CO_(3) addition accelerated the reduction kinetics;however,excessive addition worsened the reduction kinetics.

关键词： ilmenite concentrate non-isothermal kinetics reduction mechanism apparent activation energy

Effect of additives on growth of ferronickel grains and metal-slag separation behavior

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Transactions of Nonferrous Metals Society of China 2022年第10期32卷 3459-3468页

作者： Dong-lai MA Jian-bo ZHAO Qing-qing HU xue-ming lÜ Yang YOU Zhi-xiong YOU xue-wei lü College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Chongqing Key laboratory of Vanadium–Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China

Na_(2)S,Na_(2)CO_(3),FeO,FeS and carbon were used to regulate the properties of slag or metal fractions,and their effects on metal growth and metal–slag separation behavior were *** growth of ferronickel grains can be enhanced by adding these additives,and Na_(2)S was the most ***_(2)S,Na_(2)CO_(3) and FeO mainly affected the properties of slag,while carbon and FeS affected the metal *** onset temperature of metal–slag separation was 1297℃ for the sample without additive,which was decreased to 1123 and 1101℃ after adding 3.30 wt.%Na_(2)S and 4.47 wt.%Na_(2)CO_(3),*** onset temperature of metal–slag separation was mainly controlled by the slag *** average apparent activation energy of metal grain growth was 125.32 kJ/mol without additive,and it decreased obviously after adding different ***_(2)S also had the most remarkable effect on the decrease in activation energy.

关键词： nickel laterite ore slag properties metal growth metal–slag separation kinetics

Recovery of vanadium from vanadium slag by composite roasting with CaO/MgO and leaching

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Transactions of Nonferrous Metals Society of China 2020年第11期30卷 3114-3123页

作者： Jun-yi XIANG Xin WANG Gui-shang PEI Qing-yun HUANG xue-wei lü College of Materials Science and Engineering Chongqing UniversityChongqing 400044China College of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China Chongqing Key laboratory of Vanadium−Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China

A novel process of composite roasting with CaO/MgO and subsequent acid leaching was proposed to improve the recovery rate of vanadium from linz–Donawiz(lD)converter vanadium *** effects of the MgO/(CaO+MgO)molar ratio and the roasting and leaching parameters on the recovery of vanadium were *** results showed that the leaching efficiency of vanadium decreased from 88%to 81%when CaO was replaced completely by MgO;however,it could be improved by roasting with the composite of CaO/*** maximum vanadium leaching efficiency of 94%was achieved under the optimum MgO/(CaO+MgO)mole ratio of 0.5:*** results from X-ray diffractometry(XRD)and scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM−EDS)confirm that the formation rate of acid-soluble vanadates can be enhanced during roasting with the composite of CaO/MgO and that the leaching kinetics can be accelerated owing to the suppression of calcium sulfate precipitation.

关键词： vanadium vanadium slag roasting acid leaching recovery