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Formation and characterization of metallic iron grains in coal-based reduction of oolitic iron ore

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International Journal of Minerals,Metallurgy and Materials 2017年第2期24卷 123-129页

作者： Yong-sheng Sun Yue-xin Han yan-feng li yan-jun li School of Resources and Civil Engineering Northeastern University Shenyang 110819 China

To reveal the formation and characteristics of metallic iron grains in coal-based reduction, oolitic iron ore was isothermally re- duced in various reduction times at various reduction temperatures. The microstructure and size of the metallic iron phase were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and a Bgrimm process mineralogy analyzer. In the results, the re- duced Fe separates from the ore and forms metallic iron protuberances, and then the subsequent reduced Fe diffuses to the protuberances and grows into metallic iron grains. Most of the metallic iron grains exist in the quasi-spherical shape and inlaid in the slag matrix. The cumula- tive frequency of metallic iron grain size is markedly influenced by both reduction time and temperature. With increasing reduction temperature and time, the grain size of metallic iron obviously increases. According to the classical grain growth equation, the growth kinetic parameters, i.e., time exponent, growth activation energy, and pre-exponential constant, are estimated to be 1.3759 ± 0.0374, 103.18 kJ·mol^-1, and 922.05, respec- tively. Using these calculated parameters, a growth model is established to describe the growth behavior of metallic iron grains.

关键词： iron ore reduction metallic iron grain size growth kinetics activation energy

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

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International Journal of Minerals,Metallurgy and Materials 2019年第8期26卷 938-945页

作者： Yong-sheng Sun yan-feng li Yue-xin Han yan-jun li School of Resources and Civil Engineering Northeastern University

To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental *** migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,*** results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic *** reduction time and temperature significantly influenced the phosphorus content of the metallic and slag *** P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually *** P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.

关键词： high-phosphorus oolitic iron ore coal-based reduction phosphorus migration kinetics

A relative feasibility degree based approach for constrained optimization problems

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第4期11卷 249-260页

作者： Cheng-gang CUI yan-jun li Tie-jun WU Department of Control Science and Engineering Zhejiang University Hangzhou 310027 China

Based on the ratio of the size of the feasible region of constraints to the size of the feasible region of a constrained optimization problem,we propose a new constraint handling approach to improve the efficiency of heuristic search methods in solving the constrained optimization *** the traditional classification of a solution candidate,it is either a feasible or an infeasible *** refine this classification,a new concept about the relative feasibility degree of a solution candidate is proposed to represent the amount by which the 'feasibility' of the solution candidate exceeds that of another *** feasibility degree based selection rules are also proposed to enable evolutionary computation techniques to accelerate the search process of reaching a feasible *** addition,a relative feasibility degree based differential evolution algorithm is derived to solve constraint optimization *** proposed approach is tested with nine benchmark *** indicate that our approach is very competitive compared with four existing state-of-the-art techniques,though still sensitive to the intervals of control parameters of the differential evolution.

关键词： Constrained optimization Evolutionary computation Relative feasibility degree(RFD) Evolution differential algorithm

Growth behavior of the magnetite phase in the reduction of hematite via a fluidized bed

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International Journal of Minerals,Metallurgy and Materials 2019年第10期26卷 1231-1238页

作者： Jian-wen Yu Yue-xin Han yan-jun li Peng Gao School of Resources and Civil Engineering Northeastern UniversityShenyang 110819China State Key Laboratory of Mineral Processing Beijing General Research Institute of Mining&Metallurgy GroupBeijing 102628China

To understand the formation and growth mechanism of the magnetite phase during the fluidized reduction of hematite, a high-purity hematite ore was isothermally reduced using a 20vol% CO 80vol% CO2 gas mixture in a micro-fluidized bed to examine the process of the selective conversion of hematite to magnetite. The micro-structural characteristics of the magnetite phase were investigated using scanning electron microscopy (SEM) and the Brunauer, Emmett, and Teller (BET) method, and the thickness of the magnetite layer was measured and evaluated using statistical analysis. The experimental results showed that the fresh magnetite nuclei were dense needles of different lengths, and the original hematite grains became porous after complete reduction to the magnetite phase. The thickness of the mag- netite layer increased with an increase in reduction temperature and reduction time. The growth kinetics of the magnetite layer was investi- gated, and the value of the activation energy E was estimated to be 28.33 kJ/mol.

关键词： hematite ore fluidized bed suspension magnetization roasting magnetite growth kinetics

Distance dependence of atomic-resolution near-field imaging on α-Al2O3 （0001） surface with respect to surface photovoltage of silicon probe tip

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Nano Research 2016年第2期9卷 530-536页

作者： junsuke Yamanishi Takashi Tokuyama Yoshitaka Naitoh yan jun li Yasuhiro Sugawara Department of Applied Physics Graduate School of Engineering Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan

Recently, we achieved atomic-resolution optical imaging with near-field scanning optical microscopy using photon-induced force detection. In this technique, the surface photovoltage of the silicon-tip apex induced by the optical near field on the surface is measured as the electrostatic force. We demonstrated atomicresolution imaging of the near field on the α-Al2O3 （0001） surface of a prism. We investigated the spatial distribution of the near field by scanning at different tip-sample distances and found that the atomic corrugation of the near-field signal was observed at greater distances than that of the atomic force microscopy signal. As the tip-sample distance increased, the normalized signal-to-noise ratio of the near field is in a gradual decline almost twice that of the frequency shift （Δf）.

关键词： near-field scanning optical microscopy near field surface photovoltage ci-Al2O3 (0001) force detection

Recovery of boron from high-boron iron concentrate using reduction roasting and magnetic separation

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Journal of Iron and Steel Research International 2017年第2期24卷 131-137页

作者： Jian-wen Yu Yue-xin Han Peng Gao yan-jun li College of Resources and Civil Engineering Northeastern University Shenyang 110819 Liaoning China

The comprehensive utilization of abundant high-boron iron concentrate is of particular significance to Chi- na, and the high-boron iron concentrate has not yet been utilized as a source for boron at an industrial scale due to its complex mineralogy and fine mineral dissemination. An innovative method was proposed for recovery of boron and iron from high-boron iron concentrate by reduction roasting and magnetic sepa- ration. The effects of reduction temperature and roasting time were investigated and their optimum condi- tions were determined. The mineralogical changes during roasting were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results showed that the pyrrhotite （FeS） contained in the high-boron iron concentrate and the new-formed FeS-Fe solid solution softened or melted at high temperatures owing to their low melting points, and then decreased the metallic iron ratio and accelerated the growth of metallic iron particles. Meanwhile, the magnetite and szaibelyite were converted into metal- lic iron and suanite, respectively. Consequently, boron was readily enriched into the non-magnetic product and the metallic iron was aggregated to the magnetic concentrate by magnetic separation. Boron recovery of 88.6% with corresponding B2O3 content of 14.5% and iron recovery of 95.1% with an iron grade of 92.7% were achieved when high-boron iron concentrate was reduced at 1 125℃ for 150 min. Besides, the boron reactivity of the boron-rich non-magnetic product was up to 80.8%.

关键词： High-boron ironconcentrateCarbothermic reduction Magnetic separation Metallic iron Boron-rich non magnetic product

Strengthening iron enrichment and dephosphorization of high-phosphorus oolitic hematite using high-temperature pretreatment

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International Journal of Minerals,Metallurgy and Materials 2020年第4期27卷 443-453页

作者： Wen-tao Zhou Yue-xin Han Yong-sheng Sun yan-jun li College of Resources and Civil Engineering Northeastern UniversityShenyang 110819China

The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in *** this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.

关键词： high-phosphorus oolitic hematite high-temperature pretreatment iron enrichment and dephosphorization magnetization roasting–leaching process phase transformation

The optimal time-frequency atom search based on a modified ant colony algorithm

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Optoelectronics Letters 2008年第3期4卷 227-230页

作者： GUO jun-feng li yan-jun YU Rui-xing ZHANG Ke College of Astronautics Northwestern Polytechnical University Xi＇ an 710072China

this paper, a new optimal time-frequency atom search method based on a modified ant colony algorithm is proposed to improve the precision of the traditional methods. First, the discretization formula of finite length time-frequency atom is inferred at length. Second; a modified ant colony algorithm in continuous space is proposed. Finally, the optimal time- frequency atom search algorithm based on the modified ant colony algorithm is described in detail and the simulation experiment is carried on. The result indicates that the developed algorithm is valid and stable, and the precision of the method is higher than that of the traditional method.

关键词：最优化频率原子计算方法

Strengthening leaching effect of Carlin-type gold via high-voltage pulsed discharge pretreatment

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 965-973页

作者： Peng Gao Yong-hong Qin Yue-xin Han yan-jun li Si-ying liu College of Resources and Civil Engineering Northeastern UniversityShenyang 110819China National-local Joint Engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore Resources Shenyang 110819China

A high-voltage pulsed discharge(HVPD)pretreatment was used to strengthen the leaching effect of Carlin-type gold ore containing *** results of the pretreatment experiments were obtained at the following operating conditions:a spherical gap spacing of 20 mm,pulse number of 100,and voltage of 30 *** leaching rate of gold was increased by 15.65%via the HVPD *** mass fraction of–0.5+0.35 mm and–0.35+0.1 mm was increased by 10.97%and 6.83%compared to the untreated samples,respectively,and the Au grade of–0.1 mm was increased by 22.84%.However,the superiority of the HVPD pretreatment would be weakened by prolonged grinding *** electron microscopy results indicated that the pretreated products presented as a melting state and then condensation,accompanying by some pore *** micro-cracks were generated at the interface of the ore and the original crack were expended via pulsed discharge pretreatment,with the contact area between the leaching reagent and ore increased,the leaching reaction rate enhanced and the leaching effect strengthened.

关键词： high-voltage pulse discharge pretreatment Carlin-type gold leaching rate particle size distribution micro-cracks