Abstract: The oxidation rate and recovery rate of vanadium for the technology of extracting vanadium from hot metal needs to be improved in China. Moreover ...
Contributed Papers from Materials Science and Technology (MS&T) 2015 October 4 – 8, 2015, Greater Columbus Convention Center, Columbus, Ohio, USA Copyright © 2015 MS&T15®
BASIC RESEARCH OF HIGH EFFICIENT EXTRACTION OF VANADIUM FROM HOT METAL WITH HIGH TITANIUM BY BOF Helin Fan1, Dengfu Chen1, Lin Bai1 , Mujun Long 1, Xinghong Du1 and Haijun Long1 1
College of Materials Science and Engineering, Chongqing University; Chongqing 400044, P.R. China
Keywords: high efficient extraction of vanadium, hot metal, high titanium Abstract: The oxidation rate and recovery rate of vanadium for the technology of extracting vanadium from hot metal needs to be improved in China. Moreover, extracting vanadium from hot metal with high titanium is fairly different form Extraction of vanadium from hot metal with normal titanium. The thermodynamics characteristic of extracting vanadium from hot metal with high titanium and the effect of titanium content on extracting vanadium were studied. Reasonable joining system for cooling agent based on heat release of element in hot metal was proposed. The results show that joining the coolant at 10% oxygen, and completing it at 40~50% oxygen can improve the efficiency of extracting vanadium. Kinetics on extracting vanadium was studied and that diffusion is restrictive link for extracting vanadium was pointed out. The results indicate mixing can obviously enhance the efficiency of extracting vanadium, improving kinetics condition. 1 Introduction Vanadium is recognized as valuable strategic resources and has been broadly applied in lots of industries, because of its advantages of excellent specific strength, corrosion resistance and nonmagnetic[1-3]. About 85% of vanadium is used in iron and steel industry, and the remaining is served in chemical catalyst, titanium alloy, function materials, etc[4-6]. At present, the most common process of extracting vanadium is to smelt and reduce magnetite of vanadium and titanium and to obtain vanadium-bearing hot metal[7-9]. The vanadium-bearing hot metal is oxidized to gain vanadium slag and semisteel with carbon. There are many kinds of processes for oxidation of vanadium-bearing hot metal. Extraction of Vanadium from hot metal by BOF is the main process in China[10]. However, the oxidation rate and recovery rate of extracting vanadium by BOF needs to be improved. Researchers have done some works about extracting vanadium by BOF, mainly involving critical transformation temperature of carbon and vanadium, existing form of vanadium in vanadium slag, temperature controlling of molten pool, system for oxygen supplying, cooling agent, distribution ratio between vanadium slag and hot metal.[11-14]. The effect of extraction of vanadium by BOF largely depends on the thermodynamics and kinetics characteristic of vanadium-bearing hot metal. Moreover, Reasonable joining system for
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cooling agent plays an important role on the result of extracting vanadium. Therefore, research on the characteristic of thermodynamics and kinetics and reasonable joining system for cooling agent is fairly necessary. 2 Experiment Design 2.1 Experiment Device Induction furnace used for experiment was employed as melting furnace and the top blowing oxygen system was designed, by which elements in hot metal were oxidized, realizing the separation of vanadium slag and iron. The schematic diagram of experimental device and the photo of induction furnace were respectively shown as figure 1 and figure 2. The fast measuring gun for temperature (the thermocouple of double platinum rhodium, B-scale) was chosen for contacting molten pool for temperature. X-ray fluorescence spectrometer, carbon sulfur analyzer, and chemical analysis were served for testing the sample.
Figure 1. Experimental Device Schematic
Figure 2. Photo of Induction Furnace
2.2 Experimental Raw Material The hot metal containing vanadium in this paper was obtained from mixture of iron ore concentrate and titanium concentrate by non-blast furnace process. The chemical composition of hot metal containing vanadium from different process was shown as table 1. It was visible difference that titanium content of hot metal from non-BF process was much higher than hot metal form BF process (Pangang). Table 1. The Chemical Composition of Hot Metal Containing Vanadium Composition
C
V
Si
Mn
Ti
S
P
BF process (Pangang) non- BF process
4.4 4.5
0.302 0.45
0.15 0.15
0.19 0.18
0.11 0.80
0.078 0.12
0.06 0.12
3 Thermodynamics Characteristic of Extracting Vanadium by BOF 3.1 Research on Transformation Temperature of Carbon and Vanadium The transformation temperature of carbon and vanadium was extremely critical
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thermodynamics parameter. The oxidation rate and recovery rate of vanadium depended on the relationship between transformation temperature and actual temperature of molten pool. Therefore, calculating transformation temperature and keeping the temperature of molten pool below the temperature was the key of extracting vanadium by BOF. According to the thermodynamics data from literatures, the transformation temperature of carbon and vanadium was calculated.
2 1 [V] CO(g) (V2O3 ) [C] ΔGθ5 250732.42 148.22T (J/mol) 3 3 The Gibbs free energy of nonstandard condition of reaction above,
ΔG 5 ΔG 5θ RT ln K ΔG 5θ RT ln
ac a
1 3 V2 O3
2 3 v
(1)
(2)
a PCO a C fC [%C]
(3)
a V f V [%V]
(4)
a V2O3 γV2O3 χ V2O3
(5)
lg fC eCC[%C] eSiC [%Si] eCMn [%Mn] eSC [%S] eCP [%P] eCV [%V] eCTi [%Ti] lg f V eCV [%C] eSiV [%Si] eVMn [%Mn] eSV [%S] eVP [%P] eVV [%V] eTi V [%Ti] Ttrans
250732.42 a c a1/3 VO 148.22 R ln 2 / 3 2 3 a v PCO
R- Avogadro constant, 8.314J·K-1·mol-1 aC, aV-activity of carbon and vanadium in hot metal aV2O3-activity of vanadium trioxide in vanadium slag PCO-partial pressure of carbon monoxide in gas phase fC,fV- activity coefficient of carbon and vanadium in hot metal [%C],[%V]-mass fraction of carbon and vanadium in hot metal eij -interaction coefficient of solute elements γV2O3- activity coefficient of vanadium trioxide in vanadium slag χV2O3-mole fraction of vanadium trioxide in vanadium slag
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(6) (7) (8)
Figure 3. Transformation Temperature and Actual Temperature of Molten Pool
It could be observed that transformation temperature decreased sharply and actual temperature of molten pool increased slowly with hot metal blowing. The obvious growing activity of vanadium trioxide, the distinct shrinking activity of vanadium and the little change of carbon activity contributed to the former phenomenon. The oxidation of elements especially carbon in the hot metal leaded to the latter phenomenon. And, the moderate rise of molten pool temperature was attributable to joining cooling agent. Moreover, when the vanadium content was lower (about 0.10%), the molten pool temperature was higher than transformation temperature, which was disadvantages condition for extracting vanadium. Molten pool temperature exceeded transformation temperature of carbon and vanadium at about eighth minute. The relatively large amount of carbon oxidation started at about ninth minute. Coherence of the two above phenomenon showed accuracy of transformation temperature by calculating. Moreover, transformation temperature of hot metal of non-BF was 27 degrees Celsius higher than hot metal of blast furnace, because of its high content of titanium. In view of transformation temperature, this was good for extracting vanadium for hot metal from non-BF. However, the high content of titanium had little impact on transformation temperature, due to titanium dioxide’s entering into vanadium slag at the starting stage of blowing. The large amount of heat from titanium oxidation went against the goal of extracting vanadium. The adding viscosity of vanadium slag from Titanium dioxide did bad to extract vanadium. In a word, high content of titanium in hot metal was bad for vanadium extracting. 3.2 Research on Law of Elements Oxidation during Extracting Vanadium The oxidation sequence of elements depending on its difference of thermodynamics properties had a fairly important effect on realizing the goal of extracting vanadium and reserving carbon. Content variations of elements in hot metal during extracting vanadium were shown as figure 4
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and figure 5.
Figure 4. Main Elements Variation during Extracting Vanadium by BOF
Figure 5. The Remaining Elements Variation during Extracting Vanadium By BOF
The oxidation of Si, Mn and V was fast at the starting stage of blowing oxygen. In the starting six minutes of blowing oxygen, Si and Mn has oxidized to low lever, while the oxidation of C was restrained. In the last six minutes of blowing oxygen, the oxidation of C accelerated clearly, while the oxidation of C slowed relatively. P and S oxidation were respectively restrained in the whole process of extracting vanadium. 4 Reasonable Joining System for Cooling Agent According to the thermodynamics characteristic of extracting vanadium by BOF, the temperature of molten pool was absolutely vital for the oxidation and recovery rate of vanadium. Concretely speaking, keeping the molten temperature under transformation temperature at most of extracting time was perfect for of extracting vanadium. Joining cooling agent was the main way to realize this goal.
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The amount of cooling agent depended on thermal equilibrium of hot metal with blowing. The addition time of cooling agent was fairly important for controlling the temperature of hot metal. The process of heat release of hot metal during extracting vanadium was calculated by the software of FactSage.
Figure 6 Process of heat release of hot metal
It could be seen that heat release at the start 30 % time of extracting vanadium process was extremely fiercely. In view of reaction kinetics and thermal accumulation, joining system for cooling agent was keeping addition from 10% time to 40 %time of the process. Compared with the traditional method, the reasonable joining system for cooling agent made the oxidation rate of vanadium increase by 2.96% and the grade of vanadium slag increase by 2.21%. 5 Kinetics Characteristic of Extracting Vanadium by BOF The kinetics of extracting vanadium determined the result of this process in a large degree. The lower vanadium and higher carbon in the hot metal was goal of extracting vanadium. The main contents of hot metal during extracting vanadium with electromagnetic stirring and without electromagnetic were compared in the figure 7.
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Figure 7 Effect of electromagnetic stirring on extracting vanadium
With electromagnetic stirring, the contents of carbon and vanadium were respectively 3.39% and 0.034%, which was satisfactory. While without electromagnetic stirring, the contents of carbon and vanadium were 2.56% and 0.36%, which was fairly unsatisfactory. It could be deduced that the amount advantage of carbon in hot metal leaded to more oxidation. According to the difference of result from electromagnetic stirring, process of extracting vanadium was controlled by diffusion. 6 Conclusions (1) Transformation temperature decreased sharply and actual temperature of molten pool increased slowly with hot metal blowing. At the later period, transformation temperature exceeded molten pool temperature and oxidation of carbon accelerated. (2) Carbon oxidation was restrained at earlier stage of blowing and vanadium oxidation was restrained at later stage. Si and Mn oxidized to low lever at earlier stage and P and S oxidation were respectively restrained in the whole process. (3) Joining system for cooling agent was keeping addition from 10% time to 40 %time of the process. (4) Differences of result from electromagnetic stirring showed that process of extracting vanadium was controlled by diffusion. Reference [1] Lanjie Li, Li Zhang, Shili Zheng, et al. “Acid Leaching of Calcined Vanadium Titano-magnetite with
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Calcium Compounds for Extraction of Vanadium”. The Chinese Journal of Process Engineering, 11(4) (2011), 573-578. [2] M. Aarabi-Karasgani, F. Rashchi, N. Mostoufi, et al. “Leaching of vanadium from LD converter slag using sulfuric acid”. Hydrometallurgy, 102(2010), 14-21. [3] R.Navarro, J.Guzman, E.Guibal, et al. “Vanadium recovery from oil fly ash by leaching, precipitation and solvent extraction process”. Waste Management, 27(2001), 425-438. [4] Taylor P R, Shuey S A, Vidal E E, et al. “Extractive metallurgy of vanadium-containing titaniferous magnetite ores: A review”. Minerals and Metallurgical Processing, 23(2)(2006), 80-86. [5] R. R. Moskalyk, A. M. Alfantazi. “Processing of vanadium: a review”. Mineral Engineering, 16(9)(2003), 793-805. [6] W. You. “The Resources of Vanadium and Its Applications, Development and Outlook”. Rare Metals and Cemented Carbides, 01(1996), 51-55. [7] Daoxin Huang. Vanadium Extraction and Steelmaking (Beijing, Metallurgical Industry Press, 2000), 16-20. [8] B.C.Jena, W.Dresler, and I.G.Reilly. “Extraction of Titanium, Vanadium and Iron from Titanomagnetite Deposits at Pipestone Lake, Manitoba, Canada”. Minerals Engineering, 8(1-2)(1995), 159-168. [9] Desheng Chen, Longsheng Zhao, Yahui Liu,et al. “A novel process for recovery of iron, titanium, and vanadium from titanomagnetite concentrates: NaOH molten salt roasting and water leaching processes”. Journal of Hazardous Materials, (244–245)(2013), 588-595. [10] Shaoli Yang, Guoqin Liu, Housheng Chen. Vanadium and Titanium(Beijing, Metallurgical Industry Press, 2007), 89-96. [11] Yu L, Dong Y C, Ye G Z, et al. “Concentrating of vanadium oxide in vanadium rich phases by addition of SiO2 in converter slag”. Ironmaking Steelmaking, 34(2)(2007),131-137. [12] Xuemei Qing, Bing Xie, Danke Li, et al. “Study on oxidation of vanadium in molten iron and formation of vanadium-iron spinels”.The Chinese Journal of Process Engineering, 9(s1) (2009),122-126. [13] M.Nohair, D.Aymes, P.Perriat, et al. “Infrared spectra-structure correlation study of vanadium-iron spinels and of their oxidation products”. Vibrational Spectroscopy, 9(2)(1995), 181-190. [14] Xiaopeng Zhen, Bin Xie, Chongyang Zhao, et al. “Vanadium distribution behavior at the end point of vanadium extraction by converter process”. Journal of University of Science and Technology Beijing. 34(12)(2012), 1371-1378.
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