AN EXPERIMENTAL STUDY OF VISCOSITY IN FeO-SiO2-V2O3-TiO2 SYSTEM Shiyuan Liua,b,c, Lijun Wang a,b,c, Kuo-chih Choua,b,c
aCollaborative Innovation Center of Steel Technology, University of Science and Technology Beijing ,China
bState Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing100083,China
cSchool of Metallurgical and Ecological Engineering, University of Science and Technology Beijing ,100083, China
Keywords : vanadium slag , viscosity , Newtonian fluid , Non-Newtonian fluid Abstract
The viscosity was the main reason that converter smelting process of slag containing vanadium caused bonding converter mouth. The study on viscosity of FeO- SiO2-V2O3-TiO2 quaternay slag system with V2O3 level varied from 5 to 15 mass % , TiO2
contents in the range from 5 to 15 mass % and three different FeO/SiO2 mass ratio in the range from 1.4 to 2.2 is important for steelmaking. The rotation cylinder method was used the determinations of the viscosity .The influence of V2O3,TiO2,FeO/SiO2 ratio and temperature on viscosity were investigated . It was found that the viscosity of compositions with temperature shift from Newtonian fluid to non-Newtonian fluid and obey the Arrhenius law. the slag viscosity increased with increasing V2O3 level ,and decreased with increasing temperature and FeO/SiO2 ratio. In the Newtonian fluid ,the viscosity of slag decreased with increasing TiO2 content . In the Non-Newtonian , viscosity of slag increased remarkably with increasing TiO2 from 5 to 10 mass % and decreased with increasing TiO2 from 10 to 15 mass%. viscosity η0 in the Non-Newtonian fluid could obtain by extrapolating viscosity of Newtonian fluid ,viscosity η for Non-Newtonian fluid could be measured by the Einstein-Roscoe type equations . The measured viscosity fit with the experimental data in the Non-Newtonian fluid .
1. Introduction
Vanadium is an important metal used extensively and largely in manufacturing micro- alloyed steels etc.[1] Iron and steel making industries consume about 85% of total vanadium production annually .[1,2] Vanadium slag from some pyrometallurgical process is the world’s principal raw material for vanadium production.The main pyrometallurgical processes for production of vanadium slag include shaking ladle process in South Africa, hot metal ladle process in New Zealand ,and converter process in China and Russia .[1]
Advances in Molten Slags, Fluxes, and Salts: Proceedings of The 10th International Conference on Molten Slags, Fluxes and Salts (MOLTEN16) Edited by: Ramana G. Reddy, Pinakin Chaubal, P. Chris Pistorius, and Uday Pal TMS (The Minerals, Metals & Materials Society), 2016
Previous studies on vanadium containing slag systems were focused on determination of vanadium oxidation states,thermodynamic activity of vanadium oxide and phase equilibria . LiJun Wang [3] studied determination of vanadium valence state by high-temperature mass spectrometry.Yang Yang [4] studied effect of basicity ,temperature and oxygen partial pressures for phase equilibria in CaO-SiO2-MgO-Al2O3-V2O3 slags . Jinichiro Nakano[5]
reported phase equilibria of synthetic coal-petcoke slag and results an isothermal phase diagram
Viscosity is one of the important properties of iron and steel making industries slag and is very sensitive to compositional and temperature changes . Viscosity data with regard to slags containing vanadium oxide were rare and scattered . Zeng [6] investigated viscosity of FeO-SiO2-V2O3-TiO2-MnO with V2O3 level varied from 15 to 35 mass % , and three different FeO/SiO2 mass ratio in the range from 1.5 to 2.5 . but didn’t care about the effect of TiO2 effect and was short of viscosity of high temperature . Moreover zeng didn’t report effect of spinel crystallization behavior on viscosity at Non-Newtonian fluid. Study of the solid-liquid two-phase viscosity was important for industries slag . Anne-Marie studied that rheology of crystal-bearing silicate melts is primarily determined by the crystal fraction ,[7] Liushun Wu [8] studied that that Einstein-Roscoe model could even be employed for particles having irregular shapes . Alex kondratievemployed the thermodynamic computer packing F * A * C * T to model viscosities of the partly crystallized slags . [9] The traditional research methods of viscosity containing solid particle were to add high-melting solid particle to pure liquid fluid , therefore , volume fraction of solid particle and viscosity of solid-free particle were known .the slag containing vanadium viscosity study of crystallization process has not been reported .
The systematic study on viscosity of containing slag is necessary . The main chemical compositions of vanadium slag were FeO , SiO2,V2O3,TiO2 . The study on viscosity of FeO-SiO2-V2O3-TiO2 quaternay slag system is important for steelmaking. The rotation cylinder method was used the determinations of the viscosity.
2. Experimental 2.1.Materials and sample preparation
The starting materials in this study, viz.SiO2,V2O3,TiO2 were Analytical-grade powder, with SiO2 and TiO2 calcined for 12h at 1273K in a muffle furnace to decompose any carbonate and hydroxide before use while V2O3 were dried at 378K for 4h to remove any moisture and kept in a desiccatore. Mixed powder of analytical pure Fe and Fe3O4 were contained in steel dies and compacted under a pressure of 12MPa, pellts were placed in an iron crucible and heated at 1373 K for 12h to form FeO. The similar way was reported by Wang et al [10] .The composition of slag sample for viscosity measurement were listed in
table Ⅰ.Slag sample were weighed and mixed in an agate morter ,and then compacted into pellets under a pressure of 12MPa, pellets obtained was placed in a Mo crucible . 2.2.Viscosity measurement
Rotating cylinder method was used to the viscosity measurement. The Mo crucible ,filled with 160g of the prepared slag sample, was placed in the viscometer, heated to 1793K and held for 120min under high pure grade argon gas flowrate of 3L·min-
1. The height of molten slag was about 40mm, then the spindle was immersed into the slag and kept at a distance of 10 mm above the crucible bottom.The crucible and the spindle must be properly aligned along the axis of the viscometer, because a slight deviation from the axis can cause large experimental errors.
The viscosity measurements were carried out at every 20K interval on cooling and held for 30 min for the next measurement to guarantee the melt uniform. At each temperature ,the different rotating speeds range from 100 to 200 rpm, distinguishing the molten was Newtonian fluid or not. The average measurement value was adopted as the viscosity value. After completing the viscosity measurement , the Mo crucible containing vanadium slag was quickly withdrawn and then quenched in water .
Table Ⅰ slag composition for viscosity measurement /wt-%
Slag FeO SiO2 V2O3 TiO2 FeO/SiO2
A1 54.64 30.36 10 5 1.8
A2 51.43 28.57 10 10 1.8
A3 48.21 26.79 10 15 1.8
B1 54.64 30.36 5 10 1.8
B2 51.43 28.57 10 10 1.8
B3 48.21 26.79 15 10 1.8
C1 46.67 33.33 10 10 1.4
C2 51.43 28.57 10 10 1.8
C3 55.00 25.00 10 10 2.2
3. Result 3.1 Effect of TiO2
The effect of TiO2 on the viscosity of the FeO-SiO2-V2O3-TiO2 slags were presented at figure 1，from which it can be seen that the Arrhenius law is obeyed and the viscosity decreases as increasing the TiO2 level . In the Newtonian fluid ,the viscosity of slag decreased with increasing TiO2 content from 5 to 15 mass%. In the Non-Newtonian , viscosity of slag increased remarkably with increasing TiO2 from 5 to 10 mass % and decreased with increasing TiO2 from 10 to 15 mass%. Guanghua Wen reported that the viscosity increased with the TiO2 content increasing from 6 to 10 mass-% [11] .Zhen Wang also reported when the viscosity increased with the TiO2 content increasing from 5 to 10 mass-%. [12] X.J.Dong reported that viscosity at high temperature decrease with increasing TiO2 from 23 to 42 mass-% and viscosity at low temperature increased with increasing TiO2 . The ionic radius of Ti4+ , Si4+ were 0.68×10-10m ,0.41×10-10m respectively. The electrostatic potential of Ti4+ ,Si4+ were 1.85I, 2.51I ,respectively , so the bond between Ti4+ and oxygen is weaker than that between Si4+ and oxygen, leading to the depolymerisation of the oxygen ion.[13] the viscosity decreased as increasing the TiO2
content in Newtonian fluid . In Non-Newtonian fluid , the viscosity increased as increasing the TiO2 content ,which is mainly due to high crystallization temperature.
3.2 Effect of V2O3
The effect of V2O3 on the viscosity of the FeO-SiO2-V2O3-TiO2 slags were presented at figure 2，from which it can be seen that the Arrhenius law is obeyed and the viscosity
Figure 1． Viscosity variation of composition A1,A2,A3 with temperature and the rotation speed of 200rpm
Figure 2. viscosity variation of composition B1,B2,B3 with temperature and the rotation speed of 200rpm
increases as increasing the V2O3 level. The crystallization temperatures increased with the increasing V2O3 concentration , which is mainly due to high melting point of V2O3 . 3.3 Effect of FeO/SiO2 ratio
Figure 3. Viscosity variation of composition A1,A2,A3 with temperature and the rotation speed of 200rpm
The effect of FeO/SiO2 ratio on the viscosity of the FeO-SiO2-V2O3-TiO2 slags were presented at figure 3，from which it can be seen that the Arrhenius law was obeyed and the viscosity decreasesd as increasing the FeO/SiO2 ratio.
3.4 Effect of temperature
The effect of temperature on the viscosity of the FeO-SiO2-V2O3-TiO2 slag were presented at figure 1,2,3, and it shows that viscosity of the slags decreases with temperature increasing . Activation energy of different slags were listed in table Ⅱ,In Newtonian fluid ,the activation energy increase as increasing the TiO2 ,V2O3 and decrease as increasing the FeO/SiO2 ratio. The was no obvious difference of activation energies for different compositions with or without solid particle.[14]
Table Ⅱ Activation energy of different slags in Newtonian fluid
sample A1 A2 A3 B1 B2 B3 C1 C2 C3
Activation energy/KJ
· min-1 (200rpm ,i n
Newtonian fluid)
271.50 276.93 290.7 2
134.8 4
276.9 3
405.4 6
- 276.
93
266.2 2
4. Discussion
There is general consensus that viscosity of Newtonian fluid do not change as different rotation speeds . Figure 5,7 indicated that viscosity decreases as the rotation speed increases and deviate from Newtonian fluid on account of solid melt supspension rather than to experimental error ,which shows the viscosity of composition A1 with temperature shift from Newtonian fluid to non-Newtonian fluid and obey the Arrhenius law .[15] It is indicated from Figure .4, 6 that viscosities are in good agreement with the Arrhenius law at different temperatures for C3 and C1 melts. In Newtonian fluid , The activation energies of viscosity is almost not affected by the rotation speed.
Figure 8，9 were the scanning micrograph of the quenched samples A1 and B3 in the middle position along the central axis of crucible , from which it can be concluded that solid particle formed during the viscosity measurement.
Figure 4.Viscosity variation of composition A1 with temperature and the rotation speed
Figure 5.Viscosity variation of composition A1 with temperature and the rotation speed
Figure 6.Viscosity variation of composition C3 with temperature and the rotation speed
Figure 7.Viscosity variation of composition C1 with temperature and the rotation speed
The general consensus is that the Einstein-Roscoe type equations were used to describing the viscosity of two-phase systems adequately ,that is
η=η
0(1 − 𝑎𝑓)−𝑛 (1)
where η and η0 were the viscosity of the solid containing and the solid-free melts respectively ; 𝑓 is the volume fraction of solid particles in the melt ; a and n were `1.35 and 2.5 for spherical particles of a uniform size ,respectively .
According to the experimental results , the viscosities are in good accord with the Arrhenius law for Al and B3 in Newtonian fluid . the viscosity of Al and B3 deviate Newtonian fluid at lower temperature . If the rheology of Al and B3 are fully liquid slags and obey the Arrhenius law at measured temperature range , viscosity η0 in the Non-Newtonian fluid could obtain by extrapolating viscosity of Newtonian fluid. the volume fraction of solid particles was determined by micrographic analysis.[15] therefore , viscosity η for Non- Newtonian fluid could be measured by the the Einstein-Roscoe type equations . Meanwhile , The NPL model relates the viscosity of slags to structure though the OB of the melt and were used to calculated viscosity of A1 and B3 .[16] The Figure 11, 12 showed that viscosity predicted by Einstein-Roscoe type equations better than NPL model .
Figure 8.Micrograph of the quenched slag for A1 Figure 9.Micrograph of the quenched slag for B3
5. Conclusions
1. The viscosity of the FeO-SiO2-TiO2-V2O3 system with TiO2 between 5 and 15 – mass %, V2O3 between 5 and 15-mass% ,and FeO/SiO2 mass ratio between 1.4 and 2.2 was measurement at temperature 1527K to 1791 K. the slag viscosity increased with increasing V2O3 level ,and decreased with increasing temperature and FeO/SiO2 ratio. In the Newtonian fluid ,the viscosity of slag decreased with increasing TiO2 content . In the Non-Newtonian , viscosity of slag increased remarkably with increasing TiO2 from 5 to 10 mass % and decreased with increasing TiO2 from 10 to 15 mass%.
2. In Newtonian fluid ,the activation energy increase as increasing the TiO2 ,V2O3 and decrease as increasing the FeO/SiO2 mass ratio.
3. In Non-Newtonian fluid , viscosity predicted by Einstein-Roscoe type equations better than NPL model .
Acknowledgment
The authors are grateful for the financial support for this work from National Nature Science Foundation of China (No.51474141), China Postdoctoral Science Foundation (2014M560046), and Beijing Higher Education Young Elite Teacher Project (YETP0349), as well as the Fundamental Research Funds for the Central Universities (FRF-TP-15- 052A3).
Figure 10. Measured and measured vlues of viscosity η for A1
Figure 11.Measured and measured vlues of viscosity η for B3
References
1.R.R.Moskaly and A.M.Alfantazi, “Processing of Vanadium: A Review,” Minerals Engineering ，16(2003),793–805.
2. B. Liu et al ., “A Novel Method to Extract Vanadium and Chromium from Vanadium Slag using Molten NaOH-NaNO3 Binary System,” AIChE J ,59(2013), 541-552.
3. L.J. Wang et al., “Determination of Vanadium Valence State in CaO-MgO-Al2O3-SiO2 System by High-temperature Mass Spectrometry,” Metallurgical and Materials Transactions B, 44B(2013),948—953
4. Y.Yang ,L.D .Teng and S. Seetharaman , “Experimental Study of Phase Equilibrai in CaO-SiO2-MgO-Al2O3-V2O3 Slags,” Steel Research International , 85(12) (2014),1588- 1596
5. J. Nakano et al., “ Phase Equilibria in Synthetic Coal-Petcoke Slags (Al2O3-CaO-FeO- SiO2-V2O3) under Simulated Gasification Conditions ,”Energy Fuels , 25(2011),3298- 3306.
6. X.L. Zeng, “Research on Physicochemical Properties and Phase Diagram of Vanadium”(M.S.thesis, Chongqing University ,2012),27-49.
7.A.M. Lejeune and Pascal Richet, “Rheology of Crystal-Bearing Silicate Melts,” Journal of Geophysical research , 100(B3)(1995),4215-4229.
8. L.S.Wu et al., “The Effect of Solid Particles on Liquid Viscosity,” steel research international ,82(4)(2011),388-397.
9. A. Kondratiev and E.Jak, “Modeling of Viscosities of the Partly Crystallized Slags in the Al2O3-CaO-FeO-SiO2 System,” Metallurgical and Materials Transactions B ,32B(2001),1027-1032.
10. Y.Wang ,L.J. Wang, and K.C,Chou, “ Effects of CaO,MgO,Al2O3 and SiO2 on the Carbothermic Reduction of Synthetic FeCr2O4,”Journal of Mining and Metallurgy,Section B:metallurgy , 51(1)(2015),17-24.
11. G.H.Wen et al., “Development of Fluoride-Free Mold Powders for Peritectic Steel Slab Casting,” ISIJ International ,47(8)(2007),1117-1125
12. Z .Wang et al ., “Effect of Substituting SiO2 with TiO2 on Wiscosity and Crystallization of Mould Flux for Casting Titanium Stabilized Stainless Steel,” Ironmaking and Steelmaking, 39(3)(2012),210-215
13. X.J.Dong et al., “Viscosity and Viscosity Estimation Model of Fully Liquid Slags in TiO2-Al2O3-CaO-SiO2 and TiO2-Al2O3-CaO-SiO2-MgO Systems with High TiO2
Concentration and Low Mass Ratio of CaO to SiO2 ,”Ironmaking and Steelmaking , 41(2)(2014),99-106].
14. G.H. Zhang , Y.L. Zhen and K.C. Chou , “Influence of TiC on the Viscosity of CaO- MgO-Al2O3-SiO2-TiC Suspension System ,” ISIJ International ,55(5)(2015),922-927.
15. S. Wright et al .,Viscosity of Calcium Ferrite Slags and Calcium Alumino-Silicate Slags
Containing Spinel Particles,” Journal of Non-Crystalline solids, 282(2001),15-23 16.K. C.Mills , “The Influence of Structure on the Physic-Chemical Properties of Slags ,”ISIJ International, 33(1)(1993), 148-155.
