Volume 38,Issue 5,2015 Table of Contents

1 Effect of hematite particle size and reaction temperature onthe preparation of iron carbide from high phosphorus oolitic hematite

LI Guangqiang , YANG Jian , WANG Henghui , MA Jianghua

2015, 38(5):1-10. DOI: 10.11835/j.issn.1000-582X.2015.05.001

[Abstract](1376) [HTML](395) [PDF 11.46 M](1288)

Abstract:
In order to use high phosphorus oolitic hematite as a new raw material for steelmaking, the particle size of high phosphorus oolitic hematite and reaction temperature on the preparation of iron carbide are studied in H2-CH4 atmosphere. The weight loss of sample in reduction process, phase composition of high phosphorus oolitic hematite and carburization products are investigated by means of thermogravimetric method, SEM-EDS and XRD. The SEM-EDS and XRD analysis show that the main compositions of high phosphorus oolitic iron ore are hematite and quartz, and the main microstructure is oolitic clusters with the zonal distribution of hematite and apatite. According to the experiment results, the reaction activation energy of high phosphorus oolitic hematite with size in the range of 120~160 mesh is the lowest. In reduction step, the reaction activation energy is 44.95 kJ/mol, and the apparent reaction activation energy is 9.71 kJ/mol in carburization step. From the perspective of reaction rate, the optimum temperature for preparing iron carbide from high phosphorus oolitic hematite is 1 023 K and the optimum particle size is 120~160 mesh. Generally, compared with iron ore particle size, temperature has much more influence on the iron carbide formation from high phosphorus oolitic hematite.

2 Analysis on reaction dynamics model of pellets

WU Chengbo , ZHANG Jiangbin , WU Qianjiang , YUE Lin

2015, 38(5):11-16. DOI: 10.11835/j.issn.1000-582X.2015.05.002

[Abstract](1334) [HTML](632) [PDF 5.91 M](1384)

Abstract:
Through analyzing the reaction rate model of CO and H2 in the process of reducing pellets and based on experiments, the changes of resistance and reaction rate with the increase of temperature and reducibility is concluded respectively. Reaction rate model of gas mixture is concluded based on the two kinds of model. The proportion of internal diffusion resistance increases with the increase of temperature and reduction degree when pellets are reduced by carbon monoxide. Internal diffusion belongs to the rate control link when pellets are reduced by hydrogen. The reaction rate increases with temperature increasing while it decreases with carbon monoxide content increasing in the process of gas mixture reducing pellets when temperature is below 500 ℃. It will increase with the increase of the carbon monoxide concentration while temperature is over 500 ℃. Theoretical calculation value of gas mixture is consistent with the experimental results.

3 Multi-fluid numerical simulation and analysis of blast furnace inoxygen blast furnace process

ZHANG Zongliang , MENG Jiale , GUO Zhancheng

2015, 38(5):17-25. DOI: 10.11835/j.issn.1000-582X.2015.05.003

[Abstract](1232) [HTML](321) [PDF 10.23 M](1132)

Abstract:
To study the effects of different oxygen blast furnace operating procedures and their operating parameters on blast furnace process, and to predict the variation of each parameter of oxygen blast furnace process, a multi-fluid blast furnace model is built based on multi-fluid theory, metallurgical transport theory, metallurgical thermodynamics and kinetics, and computational fluid dynamics. By modifying its boundary conditions and internal parameters, the establishment of multi-fluid model of oxygen blast furnace is achieved. Numerical simulation of the normal blast furnace and gasification furnace-oxygen blast furnace (GF-FOBF)is carried out with this model and the fields of typical parameters, such as temperature field, are obtained. By comparing the calculation results, the main features of the furnace under oxygen blast furnace operating conditions and changes relative to the traditional blast furnace are analyzed. It can be found that the oxygen blast furnace internal velocity field and temperature field change, especially the distribution of gas. This model can provide reference for the experiment and development of the oxygen blast furnace process.

4 Establishing the characteristic number equation about liquid phasefluidity of iron ore powder during sintering

WU Keng , SHEN Wei , DU Ruiling , YAN Guang , MEN Zhengchao , YUAN Xiao

2015, 38(5):26-31. DOI: 10.11835/j.issn.1000-582X.2015.05.004

[Abstract](1199) [HTML](452) [PDF 5.59 M](1183)

Abstract:
The terminal point information of area growth rate is usually used to characterize liquid phase fluidity of iron ore powder during sintering. However, this characterization doesn’t take process information into account. In order to avoid using several indexes to evaluate fluidity of iron ore powder, the factors that affect liquidity are analyzed, characteristic number (LD)which could quantitatively measure liquidity is deduced by dimensional analysis and Buckingham’s theorem. Equivalent characteristic number (Ld Θ)is concluded by simplified the characteristic number equation. The high temperature furnace is used to record the whole process information in experiment. The value of each kind of ores’ Ld Θ are calculated after starting point and ending point of liquid flowing are determined by basic experiment and control experiment. The data of liquidity of 5 kinds of mineral powder are measured under original standard and new standard, the result is respectively A>C≈D>B>E and Ld ΘA>Ld ΘD>Ld ΘC≈Ld ΘE>Ld ΘB. As a result, the two standards have identical results, but the new standard that combined important factors could distinguish the influence degree of each factors on fluidity.

5 Study on BFC grid generation of blast furnace mathematical modeland its realization in Matlab

LIU Ran , ZHANG Xinyuan , QIE Yana , L Qing , ZHAO Shiwei

2015, 38(5):32-37. DOI: 10.11835/j.issn.1000-582X.2015.05.005

[Abstract](1200) [HTML](765) [PDF 5.53 M](910)

Abstract:
Simulating the process of blast furnace ironmaking through mathematical models is an effective way of new technology research and development. As an important pre-treatment process, numerical grid generation process technology is a prerequisite for the simulation of the blast furnace. Grid quality has an important impact on the blast furnace model simulation accuracy, efficiency and convergence. Therefore, the establishment of high-quality grid is very important for solving the mathematical model of blast furnace. A new method for grids-generation of balst furnace mathematical model based on body-fitted coordinate (BFC)is studied, including division of solution region, conversion and discretisation of elliptic equation and the concrete steps of the grid generation in MATLAB. In the process of BFC grid generation, using Poisson equation with source phase as the transformation equation can make the orthogonality and density of the grid to get better controlled. Treating the boundary of the deadman as boundary condition can simplify the solving process of the mathematical model. The principles of the algorithm are simple and easy to program, as well as, the efficiency of generating grids is higher and the grids can satisfy the requirements of the mathematical model.

6 Analysis on distribution law of particle size segregation ofbinary particle mixtures based on DEM

HU Zhaowen , GUO Fuliang , CHEN Chen , XU Jian , BAI Chenguang

2015, 38(5):38-45. DOI: 10.11835/j.issn.1000-582X.2015.05.006

[Abstract](1576) [HTML](625) [PDF 10.12 M](1343)

Abstract:
The distribution of particle size segregation is an inevitable phenomenon during the burden distribution process of blast furnace, which can easily lead to the decrease of porosity and the increase of pressure at the throat of the furnace top. As a result, it makes an indirect impact on the uniform distribution of gas flow, thus indirectly affecting the smooth operation of blast furnace. Based on DEM (discrete element method)simulation method, present work studies the segregation status of binary particle mixtures and proposes a segregation index T, which could be used to characterize the relative degree of particle size segregation distribution. The results show that: in the same T value graph, the greater of the difference of value T between the adjacent area is, the greater of the degree of particle size segregation of the above areas is; and in different T value graphs, the greater of the average of all the absolute difference of value T between adjacent areas is, the greater of the overall degree of particle size segregation is.

7 Influence of Al2O3 content on the fluidity behavior ofprimary melts in sintering process

WANG Zhe , ZHANG Jianliang , GAO Bing , LI Fengguang , WANG Runbo , MENG Fanyi

2015, 38(5):46-51. DOI: 10.11835/j.issn.1000-582X.2015.05.007

[Abstract](1079) [HTML](274) [PDF 7.49 M](1031)

Abstract:
In iron-ore sintering process, primary melts fluidity behavior is an important factor for sinter consolidation. Experiments to study the influence of Al2O3 content on the fluidity of primary melts is carried out. With the analysis of microstructure, the property of pore in primary melts is investigated. Results show that the fluidity index of primary melts decreases with the increase of Al2O3 content. XRD results of water quenched sample ascertain that the increase of Al2O3 content can stabilize SFCA, leading to the decrease of primary melts fluidity property. In addition, the fluidity of primary melts can have an influence on the property of pore. Pore structure in primary melts with high Al2O3 content is associated with irregular shape and it also increases the number of pore with size below 50 μm.

8 Theoretical analysis on top gas recycling of gas-based shaft furnace

LIU Bingnan , LI Qiang , ZOU Zongshu , YU Aibing

2015, 38(5):52-58. DOI: 10.11835/j.issn.1000-582X.2015.05.008

[Abstract](1136) [HTML](587) [PDF 7.61 M](1196)

Abstract:
To adequatly utilize chemical potential of the reducing gas in gas-based shaft furnace, three processes with top gas recycling(TGR) are established and a process model based on the mass and energy balance is developed to numerically analyze the advantages and disadvantages of the proposed processes. The results show that in the proposed TGR1, TGR2 and TGR3 cases, the demand of the fresh hot reducing gas decreases by 63.77%, 57.13% and 55.85%, respectively, and meanwhile the requirement of the corresponding sensible heat shows the same tendency. However, the consumption of energy in each process increasess by 5.68%, 7.27% and 17.12%, respectively, because of the additional cost of the gas reforming and preheating. The emission of CO2 for TGR1 decreases by 15.35% while the one for TGR2 and TGR3 increases by 0.16%, 3.15%, respectively.

9 Analyses on percolation behaviour of small particles in a packed bed by DEM

ZHOU Heng , ZHANG Tao , YOU Yang , LUO Zhiguo , ZOU Zongshu

2015, 38(5):59-65. DOI: 10.11835/j.issn.1000-582X.2015.05.009

[Abstract](1026) [HTML](499) [PDF 8.73 M](1011)

Abstract:
In order to further reveal the solid flow behaviour in COREX, the phenomenon of small particle percolation under gravity, which involves in COREX process, is investigated by means of discrete element method. The effects of material properties on the percolation behaviour are simulated in this paper, including diameter ratios of percolation to packing particles, damping and sliding friction coefficients between percolating and packing particles. The trajectories of percolation particles under different simulation parameters are also examined. The results show that the mean percolation velocity of small particle moving down through the bed is a constant. It is shown that increasing the diameter ratio would decrease the mean percolation velocity and increase the radial dispersion and the mean residence time. With the increase of damping coefficient, the mean percolation velocity increases and the residence time and radial dispersion of the percolation particles decrease. The sliding friction coefficient has limited effects on the percolation behaviour. From the analyses of the trajectory of small particle, it can be seen that small particle would move down slowly and even trend to be static as the diameter ratios of percolation to packing particles increase. With the decrease of damping coefficient, the trajectory of small particle would deviate from the centre and close to the boundary of the bed.

10 Effect of CO2 and O2 mixed injection on the oxidation of carbon and vanadium in vanadium-containing hot metal

WEN Gang , WANG Yu , DU Weitong

2015, 38(5):66-72. DOI: 10.11835/j.issn.1000-582X.2015.05.010

[Abstract](1048) [HTML](620) [PDF 6.62 M](863)

Abstract:
To clarify the possibility of substituting part of O2 with CO2 during the vanadium extraction process in converter, the oxidation of vanadiumTo clarify the possibility of substituting part of O2 with CO2 during the vanadium extraction process in converter, the oxidation of vanadium-containing hot metal is carried out on a laboratory-experimental scale by using CO2-O2 gas mixture as oxidizer. The results show that both the oxidized carbon and oxidation rate of carbon in the hot metal are increased with increasing proportion of CO2 in the gas mixture, while the amount of oxidized vanadium decreases with increasing proportion of CO2. The amounts of oxidized vanadium and carbon are comparable when the CO2 proportion is 0 and 20% (volume percentage) respectively. The amount of oxidized carbon and vanadium is 34.56% and 96.85% respectively when the CO2 proportion is 0, and the amount of oxidized carbon and vanadium is 36.83% and 93.29% respectively when the CO2 proportion is 20%. The ratio of vanadium oxidation amount to carbon oxidation amount (ΔV/ΔC) is adopted to evaluate the effectiveness of extracting vanadium. The ΔV/ΔC is 5.96 when the CO2 proportion is 20%, and the ΔV/ΔC are all below 3.8 when the CO2 proportion is 40%, 60% and 80%. The vanadium oxidation rate increases in the early reaction stage and decreases in the late reaction stage with increasing of CO2 concentration.

11 The effect of the grain size of calcium carbonate mineral on its heated state

LI Hong , KANG Le , FENG Jia , LI Chenxiao , ZHANG Qianqian

2015, 38(5):73-77. DOI: 10.11835/j.issn.1000-582X.2015.05.011

[Abstract](1192) [HTML](306) [PDF 5.80 M](1345)

Abstract:
In order to research the advantages and disadvantages of the ores used to make slag which have different grain sizes, six kinds of calcium carbonate minerals which have different grains are studied by X-ray diffraction, mercury, scanning electron microscopy and other analytical methods. It analyzes the grain size, the extent of fragmentation, fragmentation processes of the ore, and the ratio of pore volume, the bulk density, porosity, average pore size, activity and other factors of the lime. It researches the effects of grain size of the ore on its thermal cracking and microstructure parameters, activity of lime which is calcined. It concludes that the larger the grain size of the ore, the higher activity and more porous of lime which is calcined. When heated rapidly, the ore which has larger grain size will burst and slagging faster.

12 Behavior of phosphorus transfer from CaO-SiO2-FetO-P2O5slags to 2CaO·SiO2 particles

DOU Xiaofei , ZHU Mingmei , LIN Tiancheng , WANG Yu , XIE Bing , ZHU Bin , ZHOU Hong

2015, 38(5):78-82. DOI: 10.11835/j.issn.1000-582X.2015.05.012

[Abstract](1215) [HTML](310) [PDF 5.19 M](1039)

Abstract:
In this paper, the behavior of phosphorus transfer from CaO-SiO2-FetO-P2O5 slags to 2CaO·SiO2 (C2S) particles is investigated. The reaction between C2S particles and the slag saturated C2S is conducted at 1 500 ℃ in laboratory. Ingredients at different positions on the interface between C2S particles and the slag are observed and analyzed by SEM/EDS and the phosphorous transfer behavior is discussed. The result shows that C2S particles react with the particles surrounded molten slag in the solid-liquid two phase zone and forms the n·2CaO·SiO2-3CaO·P2O5 (nC2S-C3P) solid solution. With the reaction time progressing, the thickness of nC2S-C3P solid solution layer increases. In the direction to the inside of C2S particles, the phosphorus content in the nC2S-C3P layer decreases. Knowing the behavior of phosphorus transfer from CaO-SiO2-FetO-P2O5 slags to C2S phase is helpful to study the formation mechanism of nC2S-C3P in the slags.

13 Laboratory study on dephosphorization with limestone substituting for some lime

LIANG Yongchang , TANG Haiyan , LI Jingshe , GUO Senlin , WANG Guofeng , DANG Jinqian , YANG Hongbo , LI Hong

2015, 38(5):83-88. DOI: 10.11835/j.issn.1000-582X.2015.05.013

[Abstract](1070) [HTML](409) [PDF 5.33 M](1048)

Abstract:
To investigate the effect of the quantity of limestone added to and the way of limestone added into the furnace on dephosphorization efficiency, thermal experiment is carried out in a vacuum induction furnace by changing the quantity of added limestone. The experiment results show that it is feasible to substitute limestone for lime to slag, and how the limestone is added to the furnace plays a significant influence on dephosphorization. When the substitution ratio is 40%, thermal experiment gets the best result of dephosphorization efficiency with the final phosphorus content reaching 0.012% from the initial number of 0.12%, and the dephosphorization rate increasing by 24.17%. However, much of the slag is in incrustation state, thus the experiment couldn’t be carried out normally when the ratio reaches 80%. Furthermore, the optimum scheme for dephosphorization with limestone can be described as follows: steelmaking with the substitution ratio of 60% is the best one when lowering production cost is the first concern, while 40% is the best when the quality is cared most.

14 The evolution of inclusions in high quality GCr15 bearing steels during secondary refining process

ZHU Chengyi , WU Bingxin , ZHANG Zhicheng , LI Guangqiang , PAN Mingxu

2015, 38(5):89-97. DOI: 10.11835/j.issn.1000-582X.2015.05.014

[Abstract](1099) [HTML](431) [PDF 8.18 M](1064)

Abstract:
Based on the productive process of BOF-LF-RH-CC for GCr15 bearing steels and using FE-SEM/EDS, evolution rule and mechanism of the inclusions in LF and RH refining process have been studied. Results show that two types of evolution manners of the complex inclusions for the steel during refining process are summarized. The complex inclusions originate from Al2O3 and then change to MgO·Al2O3→(CaO-MgO-Al2O3-(CaS)) and (Al2O3-MnS)→(Al2O3-MnS- Ti(C,N)) respectively. Desulfurization effect is obvious in LF refining process, and sulfide inclusions in steel decrease significantly. The main inclusions at the beginning of LF refining process are some simple inclusions such as MnS, Al2O3, TiN, etc. At the end of LF refining process, the inclusions are compounds which Al2O3 is covered with MnS, TiN, Ti(C, N) or CaS on the surface. CaO in refining slag and MgO in refractories are easily reduced by aluminum and carbon in the steel and then Ca and Mg will react with the dissolved oxygen in steel, which leads to the number of D-type inclusions increasing at the end of LF refining. After RH and soft blowing process, sulfide inclusions are removed further, the number of D-type inclusions and complex D-type inclusions covered with A-type and T-type inclusions increase. During the LF refining, the size of inclusions mainly concentrates in the range of 1-3 μm. During the RH refining, the size of inclusions mainly concentrates less than 1 μm. The maximum size of the inclusion changes from 10.79 μm to 5.68 μm, and the number of inclusions in per square microns decreases from 372/mm 2 to 258/mm 2. RH and soft blowing process have removed the inclusions larger than 3 μm in steel effectively.

15 Activity calculation model of FeO in refining slag

XUE Zhengliang , ZOU Feng , XIONG Rui , LI Jianli , ZHU Hangyu

2015, 38(5):98-103. DOI: 10.11835/j.issn.1000-582X.2015.05.015

[Abstract](1155) [HTML](389) [PDF 5.11 M](1123)

Abstract:
An activity calculation model for SiO2-Al2O3-CaO-MgO-FeO-MnO slag system has been established according to the molecule-ion coexistence theory. From the model, the activity of FeO in the refining slag can be calculated, and the effects of MgO, FeO and basicity w(CaO)/w(SiO2) in slag composition on the activity of components related to FeO have been analyzed in this paper, which can provide reference for steelmakers to study the control of resulfurization at changing slag’s process of LF refining to blow tire cord steel.

16 Numerical simulation analysis of electroslag remelting process for different melting rates

HE Zhu , CAI Hui , LIU Shuang , WANG Qiang , LI Baokuan

2015, 38(5):104-111. DOI: 10.11835/j.issn.1000-582X.2015.05.016

[Abstract](1183) [HTML](723) [PDF 10.46 M](899)

Abstract:
Electroslag remelting process can improve the quality of the ingot for special usage. Complex physical phenomena are involved in this process and the influence of the magnetic fluid flow, the heat and mass transfer, as well as the electrochemistry must be taken into account. By coupling the electromagnetic field, the flow field and the temperature field, a three-dimensional transient-state mathematical model has been developed to analyze the influence of melting rate on electroslag remelting process. The simulation results show that, with the increase of melting rate, the current density, joule heat and electromagnetic force become bigger, and the maximum value of field increases more than 100% when melting rate increases from 14.4 kg/h to 27.0 kg/h. With the increase of melting rate, the maximum value of temperature increases a little, while the maximum value of velocity increases about 50%, and the depth of metal melting pool increases from 27 mm to 38 mm, which is harmful to the ingot quality.

17 Behavior of inclusions during solidification of heat-resistant steel containing cerium

LI Yandong , LIU Chengjun , LI Chunlong , JIANG Maofa

2015, 38(5):112-118. DOI: 10.11835/j.issn.1000-582X.2015.05.017

[Abstract](1670) [HTML](268) [PDF 7.91 M](953)

Abstract:
A coupled thermodynamic model of inclusions precipitation and microsegregation of solute elements during solidification of heat-resistant steel containing cerium is achieved. Then the validation of this model is conducted through commercial test and physical simulation experiment at high temperature in laboratory. The effect of cerium adding, oxygen content and sulfur content on the inclusions behavior during solidification of 253MA steel is studied. The results are concluded as follows. As the increase of cerium adding, SiO2 and MnS disappear, and CeN begins to form during solidification. Ce2O3, SiO2 and MnS are formed as the oxygen content increases, and the latter two are precipitated during the solidification. As the sulfur content increases, Ce3S4 and MnS are formed while Ce2O3 disappears, and the precipitation temperature of Ce3S4 develops from liquid-solid area to above the liquidus. All the work will indicate the theoretical direction to solve nozzle clogging problem of heat-resistant steel containing rare earth elements.

18 Optimization of flow control devices in four-strand T type tundish by water simulation

CHEN Dengfu , L Kui , XIE Xin , LONG Mujun , YU Sheng

2015, 38(5):119-126. DOI: 10.11835/j.issn.1000-582X.2015.05.018

[Abstract](1075) [HTML](314) [PDF 11.50 M](1105)

Abstract:
A four-strand T type tundish is studied by using water modeling based on similarity principles. A 1∶3 physical model is built to study the influence of different walls, diversion holes and turbulent inhibitors on flow characteristics. The results show that the flow control device of “Y” type baffle+trapezoidal turbulent inhibitor (case F) apparently favor the flow pattern of the tundish. When the flow control device of case F is equipped, the proportion of dead zone goes down from 23.69% to 8.02% which means that the molten steel could mix well; the standard deviation of the average residence time is decreased by 68.85%, which infers that the consistency among all strands is also improved.

19 Numerical simulation of three-dimensional shell thickness in slab continuous casting mold

ZHANG Li , LI Jingshe , ZHANG Jiangshan , GAO Wei

2015, 38(5):127-134. DOI: 10.11835/j.issn.1000-582X.2015.05.019

[Abstract](1142) [HTML](284) [PDF 8.18 M](1128)

Abstract:
Based on the calculation of flow flied and temperature field, this article has made a numerical simulation on a slab casting mold that has a section of 1 780 mm×225 mm. In this process, three cases with different nozzles and a case without nozzle are compared to research the effect of flow field to solidification shell. It could be seen that, the maximum shell are about 45 mm at the corner and 24 mm at the center of wide face and narrow face. However, all of these are about 1-2 mm thinner than the case without nozzle. Besides, the flow of liquid steel would form a 2.5 mm sunken, which is 300 mm away from corner and 400 mm below meniscus. The molten steel would scour the whole narrow face, especially at the center. The pointed-bottom nozzle has the smallest shell and recessed-bottom has the largest shell.

20 Computational simulation on the coordination structure of CaO-B2O3-SiO2-TiO2 mold fluxes system

LIANG Xiaoping , LU Dongxu , WANG Yu , WU Jianqing

2015, 38(5):135-141. DOI: 10.11835/j.issn.1000-582X.2015.05.020

[Abstract](1102) [HTML](473) [PDF 6.57 M](1334)

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The coordination structure of the quaternary mold fluxes CaO-B2O3-SiO2-TiO2 is invested by means of molecular dynamics simulation, and then the regularity of the changes for the variety of TiO2 content is concluded. The results show that there are only three-coordinate triangular body and four-coordinated tetrahedron of boron, and it is mainly the form of six-coordinated octahedral between Ti and O in the slag. With the increasing of TiO2 content, microstructure ligands form of Si, B and Ti will change significantly, converting to the direction of four-coordinate structure, three-coordinate structure and five-coordinate structure respectively.

21 Simulation experiments for dealkalization of red mud by limekiln gas

TANG Xiaohui , XU Gang , LIU Runzao , LI Shiqi , XU Kai

2015, 38(5):142-150. DOI: 10.11835/j.issn.1000-582X.2015.05.021

[Abstract](1049) [HTML](298) [PDF 9.27 M](897)

Abstract:
Through analyzing the basic characteristic of red mud from an aluminum factory in Shanxi, a dealkalization simulation experiment of red mud with lime kiln tail gas containing CO2 around 20% is proposed. Thermodynamic analysis shows that dealkalization by using lime kiln exhaust is feasible, and the actual main factors affecting dealkalization are the dynamics factors. Experiments take dealkalization rate as an index, the influence of liquid-solid ratio, CO2 volume fraction, CO2 mole ratio, stirring speed and reaction temperature of red mud on dealkalization rate are researched and the results are as follows. The reasonable parameters for dealkalization are liquid-solid ratio 8 mL/g, CO2 volume fraction 20%, CO2 mole ratio 40, stirring speed 400 r/min and reaction temperature 60 ℃, and the dealkalization rate under these process conditions is 31.10%. The study results show that lime kiln tail gas of containing CO2 at around 20% could be used for red mud dealkalization treatment, and this process can remove the soluble alkali in red mud, which conforms to the concept of “using waste treat waste”.

22 Effect of different calcification agents on vanadium extraction from high-vanadium slag by calcified roasting-acid leaching

FAN Kun , LI Zengchao , LI Zishen , WANG Weipeng , ZHANG Weiling , ZHENG Haiyan , SHEN Fengman

2015, 38(5):151-161. DOI: 10.11835/j.issn.1000-582X.2015.05.022

[Abstract](1473) [HTML](310) [PDF 11.10 M](1287)

Abstract:
Compared with the traditional technology of vanadium extraction from vanadium slag, a new process of classified roasting-acid leaching is researched in this study. Based on the theoretical analysis on the principle of calcified roasting process, the roasting mechanism and the effect of three kinds of calcification agents (CaSO4, CaCO3 and CaO) on vanadium extraction in the calcified roasting and acid leaching processes are investigated in which high-vanadium slag is used as raw material. Research results show that the leaching ratio of vanadium increases with the increasing of roasting temperature when the temperature is lower than 1 450 K. The leaching ratio reaches maximum at 1 450 K, and then comes down. The best calcification agent composition is 100% CaSO4. By controlling the experimental conditions, the leaching ratio of vanadium in high-vanadium slag can reach 93.53%.

23 Numerical simulation for flow characterisitcs in titanium slag fluidization

LIU Songli , ZHU Kuisong , XIANG Junyi , HUANG Pan

2015, 38(5):162-163. DOI: 10.11835/j.issn.1000-582X.2015.05.023

[Abstract](1284) [HTML](281) [PDF 2.67 M](986)

Abstract:
The flow characteristics of chlorination of titanium slag in a fluidized bed are studied based on two-fluid model combined with physical properties of titanium slag with Fluent under different critical fluidizing velocities. Numerical results indicate that the modifier formula by Grace is more suitable for calculating the minimum fluidization velocity of chlorination of titanium slag. Furthermore, it also shows that, under minimum fluidization velocity, emulsion phase emerges first in the bed, and then some small bubbles take place, while under complete fluidization velocity, slugging processes at the beginning, and then it turns to be complete fluidization.

24 Application of biomass to the RHF direct reduction process

HAN Hongliang , YUAN Peng , DUAN Dongping , LI Dawei

2015, 38(5):164-170. DOI: 10.11835/j.issn.1000-582X.2015.05.024

[Abstract](1077) [HTML](440) [PDF 6.36 M](1189)

Abstract:
By considering the rotary hearth furnaces direct reduction process, using bamboo charcoal, charcoal, straw fiber and coal as reductants, the experimental study on the influence of reduction has been conducted from metallization rate, compressive strength and volumetric shrinkage. The results show that biomass reductants can replace traditional reductants used in the RHF direct reduction process. Compared with traditional reductants, biomass reductants have less affect on metallization rate, but different biomass reductants have large influence on strength and volumetric shrinkage of pellets. The compressive strength of pellet with straw fiber is relatively higher, and the compressive strength of pellets with charcoal or bamboo charcoal is low, but it can be improved at higher temperature(1 300 ℃) for reaching the production requirement. Using bamboo charcoal as reductant will lead to the swelling of pellets in the beginning stage, and this situation will make the volumetric shrinkage at high temperature lower, which will affect the strength of pellets and the heat-transfer between different material layers. Thus it would be better that bamboo charcoal should be used with other reductants.

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