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Mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes from stone coal

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Rare Metals 2013年第1期32卷 57-62页

作者： Fei Wang Yi-Min Zhang Jing Huang Tao Liu Yi Wang Xiao Yang Jie Zhao College of Resources and Environmental Engineering Wuhan University of Science and Technology

The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ~C, 6 h, 1.5 ml.g-1, 15 vol % H2SO4, and 5 % calcium fluoride （mass ratio of CaF2 to stone coal）. The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol.L-1 to the pH of 1.80 4- 0.05 by 200 g.L-1 lime milk, respectively. The solvent extraction experiments were carded out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81%, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate （Fe2Fs.7H20） and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KA1SO4 and FeA1Fs. In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.

关键词： Vanadium Stone coal Aid-leaching reagent calcium fluoride Mechanisms

Investigation of effect of electrode polarity on electrochemistry and magnetohydrodynamics using tertiary current distribution in electroslag remelting process

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Journal of Iron and Steel Research(International) 2021年第12期28卷 1551-1561页

作者： E.Karimi-Sibaki A.Kharicha A.Vakhrushev M.Wu A.Ludwig J.Bohacek Christian-Doppler Laboratory for Metallurgical Applications of Magnetohydrodynamics Montanuniversitaet of LeobenLeobenA-8700Austria Chair of Simulation and Modeling of Metallurgical Processes Montanuniversitaet of LeobenLeobenA-8700Austria Heat Transfer and Fluid Flow Laboratory Faculty of Mechanical EngineeringBrno University of TechnologyTechnicka 2896/261669BrnoCzech Republic

Transport phenomena including the electromagnetic,concentration of ions,flow,and thermal fields in the electroslag remelting(ESR)process made of slag,electrode,air,mold,and melt pool are computed considering tertiary current distribution.Nernst-Planck equations are solved in the bulk of slag,and faradaic reactions are regarded at the metal-slag interface.Aiming at exploring electrochemical effects on the behavior of the ESR process,the calculated field structures are compared with those obtained using the classical ohmic approach,namely,primary current distribution whereby variations in concentrations of ions and faradaic reactions are ignored.Also,the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is considered.The impact of the polarity of electrode,whether positive,also known as direct current reverse polarity(DCRP),or negative,as known as direct current straight polarity(DCSP),on the transport of oxygen to the ingot of ESR is investigated.The obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

关键词： Electroslag remelting Electrochemistry calcium fluoride calcium oxide Ion transport Electro-migration

Synergistic effect of microwave irradiation and CaF2 on vanadium leaching

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International Journal of Minerals,Metallurgy and Materials 2017年第2期24卷 156-163页

作者： Jing-peng Wang Yi-min Zhang Jing Huang Tao Liu School of Resource and Environmental Engineering Wuhan University of Science and Technology Wuhan 430081 China Hubei Provincial Engineering Technology Research Center of High Efficient Cleaning Utilization for Shale Vanadium Resource Wuhan 430081 China Hubei Provincial Collaborative Innovation Center for High Efficient Utilization of Vanadium Resource Wuhan 430081 China

The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride （CaF2） on the vana- dium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when CaF2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%-15% when 5wt% CaF2 is added; by contrast, in the absence of CaF2, the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation, whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover, a large amount of A1 and V and a small amount of Si are dissolved from samples under microwave heating, as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When CaF2 is present, the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer, resulting in a prominent effect of mi- crowave irradiation.

关键词： vanadium extraction leaching microwave irradiation calcium fluoride synergistic effects

Thermal bleaching of optical absorption and photoluminescence spectra of γ-irradiated CaF_2:Dy:Pb:Na single crystals

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Journal of Rare Earths 2010年第4期28卷 493-497页

作者： S.M. Moses Kennedy Department of Physics S.S.N. College of Engineering Rajiv Gandhi Salai Kalavakkam-603 110 Chennai Tamil Nadu India

The variation of the optical absorption (OA) and photoluminescence (PL) spectra with temperature was studied on γ-irradiated CaF2:Dy:Pb:Na single crystals. The OA spectrum showed bands around 2.05, 3.20, 3.82 and 6.20 eV which could be attributed to different sodium associated (SA) colour centres (CCs) such as MNa and RA+ . Heating the crystal indicated the annihilation and formation of different SACCs. The excitation spectrum for the characteristic Dy3+ emission at 2.14 eV immediately after irradiation was...

关键词： calcium fluoride optical absorption photoluminescence colour centres dysprosium lead sodium rare earths

Hydrogen Pick-Up During Electroslag Remelting Process

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Journal of Iron and Steel Research(International) 2011年第4期18卷 19-23页

作者： JIANG Zhou-hua DONG Yan-wu LIANG Lian-ke LI Zheng-bang School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China Central Iron and Steel Research Institute Beijing 100081 China

The pick-up of hydrogen during electroslag remelting process for several slags consisting of CaF2-Al2O3-CaO-SiO2-MgO had been investigated.The laboratory-scale remelting experiments had been carried out in open air and water-free argon atmosphere,and then the influencing factors were analyzed.It had been found that the hydrogen content in steel varied with different slag compositions.The compositions and state of slag had significant effect on the hydrogen level in steel.Partial return slag and premelted slag could avoid the hydrogen pick-up especially in the early stages of the process.However,premelted slag was the optimum state to control the hydrogen pick-up in steel.Experimental results indicated that water-free argon atmosphere was very favorable to the control of hydrogen in steel in the normal remelting period.

关键词： electroslag remelting hydrogen calcium fluoride premelted slag protective atrriosphere

Effect of Boron Mud and CaF_2 on Surface Tension and Density of CaO-SiO_2-B_2O_3 Ternary Slag Systems

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Journal of Iron and Steel Research(International) 2014年第8期21卷 745-748页

作者： Li-li YANG Hong-ming WANG Xiang ZHU Gui-rong LI School of Materials Science and Engineering Jiangsu University Jiangsu Province Key Laboratory of High-End Structural Materials

The effect of boron mud and CaF2,which were used as fluxing agents,on surface tension and density of CaO-SiO2-B2O3 ternary slag systems was investigated.The surface tension and density were measured by using the ring detachment method and Archimedean method,respectively.The results indicated that surface tension and density of the slag systems decreased with increasing temperature in the range of 1380-1480℃.When 5%-10% CaF2 was employed as fluxing agent,the surface tension and density of slag were decreased with increasing CaF2 content,and the surface tension changed from 0.3to 0.6N/m,while the density changed from 3.4to 4.1g/cm3.However,when using 5%-10%boron mud as fluxing agent,the surface tension was enhanced,whereas the density decreased with the increase of boron mud content,and the variation range was 0.4-0.6N/m for surface tension and 3.2-3.9g/cm3 for the density.As a conclusion,using boron mud as fluxing agent to substitute for CaF2 did not cause significant changes in slag surface tension and density.

关键词： boron mud calcium fluoride surface tension density

Thermodynamic Properties of CaCl<sub>2</sub>-CaF<sub>2</sub>-CaO System: Phase Diagram Investigation

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Materials Sciences and Applications 2021年第4期12卷 139-151页

作者： Julien Claquesin Mathieu Gibilaro Laurent Massot Olivier Lemoine Gilles Bourges Pierre Chamelot Laboratoire de Génie Chimique UMR 5503 UPS-CNRS-INP Université de Toulouse Toulouse France CEA DAM VALDUC Is-sur-Tille France

The CaCl2-CaF2-CaO phase diagram was investigated in the CaO low region (2-CaF2 and CaCl2-CaO binary diagrams, constituting the ternary system, were first studied by Differential Scanning Calorimetry (DSC) measurements and X-Ray Diffraction (XRD) characterization;a good agreement was obtained between the phase diagram models calculated with FactSage®software (FTsalt database) and present experimental data. As the CaF2-CaO liquidus could not be measured by DSC due to the high melting temperature, this diagram was calculated using FTsalt database combined with FToxid database of FactSage® software. The ternary phase diagram was obtained by calculations and exhibits an eutectic at the composition CaCl2-CaF2-CaO (78.2-15.7-6.1 mol.%) melting at 637°C, and five peritectic points. Measurements of relevant vertical cross-sections for three CaCl2-CaF2 compositions (50-50, 40-60 and 30-70 mol.%) up to 18 mol.% CaO are in agreement with the ternary phase diagram model. For each section, the liquidus temperature is constant up to around 11 mol.% CaO and then sharply increases. Moreover, an increase of CaF2 content in CaCl2-CaF2 melt leads to a decrease of the CaO solubility in isothermal condition.

关键词： Differential Scanning Calorimetry (DSC) Phase Diagram calcium Chloride calcium fluoride calcium Oxide Ternary System