Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags

Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags were determined at 1673 K by electrochemical of the solid electrolyte cell： Mo [Mo＋MoOu[ZrO2（MgO）[Fe＋（CaO-SiO2-Al2O3-MgO-FeO）＋Ag[Fe. The influences of slag compositions and basicity on FeO activities were analyzed. The results reveal that, for slags of fixed （%CaO）/（%SiO2） ratio, MgO and Al2O3 content, there was an increase of FeO activities with increase of FeO content. For slags with constant {（%CaO）＋ （%MgO）}/（%SiO2） ratio, fixed FeO and A1203 content, FeO activities decreased when MgO content increased from 5% to 10%, and increased with the increase of MgO content when it was over 10%. The FeO activities increased when （%CaO）/（%SiO2） ratio changed from 1.03 to 1.30 in the slags of constant MgO, FeO and Al2O3 content.

Activity of VO in Molten Ternary CaO-SiO_2-VO Slag

The activity of VO in molten ternary CaO-SiO_2-VO Slag has been determined by chemical equilibrium method, using tin as the solvent metal. The relation between the activity and the content of VO, as well as the effect of slag basicity on activity of VO. are discussed.

Study on sulphide capacity of CaO-SiO_2-Al_2O_3-MgO-Fe_tO slags

The sulphide capacity of CaO-SiO2-Al2O3-MgO-FetO slags was studied at 1773 K using gas-slag equilibrium techniques. Utilizing a Pt crucible, the slag was equilibrated with a mixture of gases, namely, CO, CO2, SO2 and N2 to provide the partial pressure of oxygen and sulphur. It was shown that at fixed FetO and Al2O3 contents and a fixed { （%CaO）＋（%MgO）}/（%SIO2） ratio, the sulphide capacity decreases with increasing MgO content. At a constant （%CaO）/（%SiO2） ratio and constant MgO and Al2O3 contents, increasing the FetO content of the slags also results in an increase of the sulphide capacity. The rising basicity of （%CaO）/（%SiO2） from 1.0 to 1.4 at fixed MgO, FetO and Al2O3 contents significantly increases the sulphide capacity.

氧分压和温度对CaO-SiO_(2)-TiO_(x)渣系钛组元价态及赋存相的影响

从含钛高炉渣中绿色高效提取钛资源是实现高附加值钛制品持续开发的有力保障,目前与含钛氧化物渣系相关的关键热力学数据匮乏,严重制约了相关提钛工艺的开发。本文基于典型含钛高炉渣成分及矿物特征,结合FactSage 8.2热力学软件的“Phase Diagram”模块和“FactPS”、“FToxid”数据库,计算分析了含钛矿物在高炉不同区域还原过程中钛赋存相的变化规律,并进一步计算分析了1400~1600℃下0.21~10^(-18)atm氧分压范围内CaO-SiO_(2)-TiO_(x)渣系平衡相的演变规律。结果表明,当温度一定时,随着氧分压的降低,液相区范围先增大后减小,钛的氧化物被逐级还原;当氧分压一定时,随着温度的增加,液相区逐渐变大,液相与钙钛矿两相共存区随温度升高先小幅增大后小幅缩小,且向w(CaO)/w(SiO_(2))比增大的方向移动,液相与金红石两相共存区先大幅增大后小幅缩小。本文结果对于深入理解含钛赋存相在不同工艺参数下的演变规律,进而开发更加绿色高效钛资源提取工艺具有重要意义。

Effects of MgO/Al2O3 ratio on viscous behaviors and structures of MgO-Al2O3-TiO2-CaO-SiO2 slag systems with high TiO2 content and low CaO/SiO2 ratio

The effects of MgO/Al2 O3 ratio on the viscous behaviors of MgO-Al2 O3-TiO2-CaO-SiO2 systems were investigated by the rotating cylinder method.Raman spectroscopy was used to analyze the structural characteristics of slag and Factsage 7.0 was adopted to demonstrate the liquidus temperature of slag.The results show that the viscosity and activation energy for viscous flow decrease when the MgO/Al2O3 ratio increases from 0.82 to 1.36.The break point temperature and liquidus temperature of slag initially decrease and subsequently increase.The complex viscous structures are gradually depolymerized to simple structural units.In conclusion,with the increase of MgO/Al2O3 ratio,the degree of polymerization of slag decreases,which improves the fluidity of slag.The variations of liquidus temperature of slag lead to the same changes of break point temperature.

The Influence of CO_(2) Cured Manganese Slag on the Performance and Mechanical Properties of Ultra-High Performance Concrete

The presence of toxic elements in manganese slag(MSG)poses a threat to the environment due to potential pollution.Utilizing CO_(2) curing on MS offers a promising approach to immobilize toxic substances within this material,thereby mitigating their release into the natural surroundings.This study investigates the impact of CO_(2) cured MS on various rheological parameters,including slump flow,plastic viscosity(η),and yield shear stress(τ).Additionally,it assesses flexural and compressive strengths(f_(t) and f_(cu)),drying shrinkage rates(DSR),durability indicators(chloride ion migration coefficient(CMC),carbonization depth(CD)),and the leaching behavior of heavy metal elements.Microscopic examination via scanning electron microscopy(SEM)is employed to elucidate the underlying mechanisms.The results indicate that CO_(2) curing significantly enhances the slump flow of ultra-high performance concrete(UHPC)by up to 51.2%.Moreover,it reduces UHPC’sηandτby rates ranging from 0%to 52.7%and 0%to 40.2%,respectively.The DSR exhibits a linear increase corresponding to the mass ratio of CO_(2) cured MS.Furthermore,CO_(2) curing enhances both f_(t) and f_(cu) of UHPC by up to 28.7%and 17.6%,respectively.The electrical resistance is also improved,showing an increase of up to 53.7%.The relationship between mechanical strengths and electrical resistance follows a cubic relationship.The CO_(2) cured MS demonstrates a notable decrease in the CMC and CD by rates ranging from 0%to 52.6%and 0%to 26.1%,respectively.The reductions of leached chromium(Cr)and manganese(Mn)are up to 576.3%and 1312.7%,respectively.Overall,CO_(2) curing also enhances the compactness of UHPC,thereby demonstrating its potential to improve both mechanical and durability properties.

Structural and microwave absorption properties of CoFe_(2)O_(4)/residual carbon composites

Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.

Boron removal from molten silicon using CaO-SiO_2-BaO-CaF_2 slag

The distribution coefficient (LB) of boron between CaO?SiO2?BaO?CaF2 slag and silicon was investigated usingelectromagnetic induction melting for the purpose of improving the boron removal fraction. The dependence of the borondistribution coefficient between slag and silicon on the fundamental parameters of CaO to SiO2 mass ratio and refining time and theadditions of BaO and CaF2 to the slag was discussed. The results show that LB can be increased by adding BaO and CaF2 toCaO?SiO2 slag. The maximum value of LB (6.94) is obtained when the CaO to SiO2 mass ratio is 1.1:1 and the contents of BaO andCaF2 are fixed at 15% and 20%, respectively. Increasing the refining time increases the LB. After the slag treatment is performedtwice, the boron content of the silicon is successfully reduced from 3.5×10?5 to 3.7×10?6, and the removal fraction of boron reaches89.4%.

ACTIVITIES OF CaO AND La_2O_3 IN LIQUID CaO-SiO_2-La_2O_3 SLAGS AND SLAG STRUCTURE

The activity of CaO and LaOin the liquid ternary slay CaO-SiO-LaOhas been de-termined by equilibrating Sn with the slag phase in a graphite crucible under l arm of CO at1600C.The experimental results ,showed that the activity of CaO and LaOchanges slowlywhile the ratio of mole fraction.x/x,is less than unit.hut varies sharply while the ra-rio increases from 1 to 1.2.In addition,by equilibrating Sn with the binary slagBO-LaOsaturated witlt solid LaOat three different temperatures,the relation betweenIgγ~0 and I/T is determined as follows:Igγ~0=-20400/T+11.37(1500-1600C)A random network model of molten silicate structure was applied to CaO-SiO-La2O.It was found that the experimentally determined activity-composition curve of CaO arequalitatively reproduced by the curves calculated with the model,but the curves of LaOareconsiderahly different from the calculated ones.It implies that the model used is over-simpli-fied and that the difference in interaction energy between the metal cations of different valenceand silicate anions should be considered.

Kinetics of Reduction of Iron Oxide in CaO-SiO_2-Al_2O_3-Fe_tO Slags with Graphite Powder

The reduction rate of Fe^tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder has been determined in an alumina crucible at 1 673-1 823 K. The effects of temperature, slag basicity and Fe_tO content on the reduction rate have also been discussed. Test results show that the reduction rate increases with the increase of temperature or Fe_tO concentration in slags, and the reduction rate has a parabolic relation with slag simple basicity or optical basicity. The maximum reduction rate is observed around CaO/SiO_2=1.5 of molten slags. The reaction order is 1.26 or 1.31, and the reduction activation energy is 126.8 or 129.7 kJ/mol respectively in regard to Fe_tO content or Fe_tO activity calculated by using regular solution model. The reduction rate of Fe_tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder is in the range of 0.15×10^-4-0.86×10^-4 molO/cm^2·s.

KINETICS OF REDUCTION IRON OXIDE IN CaO-SiO_2-Al_2O_3-Fe_tO SLAGS WITH CARBON SATURATED IN MOLTEN IRON

The rate of reducing Fet O in CaO-SiO2-Al2O3-Fet O slags with carbon saturated in molten iron has been determined in a graphite crucible in the temperature range of 1673-1773K. The effects of temperature, slag basicity and FetO content on the reduction rate have also been discussed. Test results show that the reduction rate increases with increasing temperature or FEtO concentration in slags, and the reduction rate has a parabolic relation with the simple basicity or optical basicity of slag, the maximum reduction rate being observed at around CaO/SiO2=1.5 of molten slags. The reduction reaction order is 1. 73 or 1.80, and the reduction activation energy is 299.9 or 295.9 kJ/mol in regard to Fet O weight content or Fet O activity calculated by using regular solution model, respectively. The reduction rate of CaO-SiO2-Al2 O3-Fet O slags with carbon saturated in molten iron is in the range of 0.32-3.48 mol-O/cm2·s.

Oxidation process of low-grade vanadium slag in presence of Na_(2)CO_3

The oxidation process of low-grade vanadium slag in the presence of Na2CO3 was investigated by XRD,SEM/EDS and TG-DSC techniques.The results show that the vanadium slag is oxidized in a temperature range from 273 to 700 °C.Olivine phases and spinel phases are completely decomposed at 500 and 600 °C,respectively.Most of water-soluble sodium vanadates are formed between 500 and 600 °C.When roasting temperature reaches above 700 °C,the vanadium-rich phases of sodium vanadates can be obviously observed.However,at temperature above 800 °C,the samples are sintered.Most of the vanadium is enwrapped by glassy phase compounds which lead to the decrease of the leaching rate of vanadium.At the same time,the effect of roasting temperature on extraction of vanadium and characterization of leach residues were discussed.

CaO-SiO_2-Al_2O_3渣系连铸保护渣结构的拉曼光谱研究

在高铝钢连铸过程中,钢水中的Al与CaO-SiO2基连铸保护渣中的SiO2反应导致保护渣中SiO2含量降低而Al2O3含量大幅增加,CaO-SiO2基转变为CaO-SiO2-Al2O3基连铸保护渣而影响高铝钢连铸,所以研究CaO-SiO2基向CaO-SiO2-Al2O3基保护渣转变过程中结构上发生的变化有助于开发出满足高铝钢连铸需求的保护渣。本文利用拉曼光谱研究了CaO-SiO2基和CaO-SiO2-Al2O3基连铸保护渣的结构特点。研究结果表明,CaO-SiO2基保护渣主要由Q0,Q1,Q2和Q3等微结构单元构成的硅酸盐网络结构;当转变为CaO-SiO2-Al2O3基保护渣后,渣样中的网络破坏体优先用于破坏硅酸盐网络结构,当渣中SiO2含量较低时,部分网络破坏体会促进Al 3+形成[AlO4]四面体结构。渣中生成的[AlO4]四面体会进入硅酸盐网络结构形成铝硅酸盐网络结构,以Al-O-Al或Al-O-Si等方式连接,导致渣样结构变得复杂多变。使用Li2O对Na2O和CaO对MgO等摩尔替代研究表明相同价态离子之间的替换能够改变[AlO4]四面体在硅酸盐网络结构上的连接方式,导致CaO-SiO2-Al2O3基保护渣渣样结构易受成分变化而改变;CaF2对CaO等摩尔替代研究发现,当渣中CaF2小于13mol%,CaF2促进渣样网络结构解体,当高于13mol%时,CaF2又会导致渣样聚合度增加。由此可见,在设计CaO-SiO2-Al2O3基保护渣时,既要考虑不同种类离子对渣样结构产生的影响,又要考虑离子含量的影响。

CaO-SiO_2-MgO-H_2O体系的热力学研究

本文研究了ＣａＯ－ＳｉＯ２－ＭｇＯ－Ｈ２Ｏ体系的热力学，结果表明：ＳｉＯ２ 优先与ＣａＯ水热形成水化硅酸钙，多余的ＳｉＯ２ 才会与ＭｇＯ直接水热形成水化硅酸镁。当没有ＳｉＯ２ 时，ＭｇＯ才会水化形成Ｍｇ（ＯＨ）２。

Effect of Na_2O on alumina leaching property and phase transformation of MgO-containing calcium aluminate slags

In order to remove or reduce the negative effect of MgO in calcium aluminate slags, the method of adding Na2O into calcium aluminate slags was studied and its effect on leaching mechanism was also analyzed. The results show that the alumina leaching efficiency of the calcium aluminate slag increases from 68.73% to 80.86% with Na2O content increasing from 0 to 4% when MgO content is 3%. The XRD results show that the quaternary compound C20A13M3S3 disappears when Na2O content increases to 4%. The addition of Na2O cannot remove the negative effect of MgO on leachability completely. XRD and EDS results indicate that Na2O can come into the lattice of 12CaO·7Al2O3 and promote the formation of 12CaO·7Al2O3

MgO-CaO-SiO_2添加剂对纳米晶刚玉磨料烧结性能的影响

采用溶胶-凝胶工艺合成陶瓷刚玉磨料,研究了MgO-CaO-SiO2复相添加剂的组成及添加量对刚玉磨料烧结性能的影响以及形成液相时刚玉磨料的烧结动力学。结果表明:MgO-CaO-SiO2添加剂的组成和添加量对刚玉磨料的结构和性能有显著影响。当加入2.5wt%组成为5MgO-CaO-5SiO2的添加剂时,烧结后得到刚玉磨料平均晶粒尺寸达到80 nm,致密化程度高,单颗粒抗压强度为37.5 N。引入复相添加剂的液相烧结激活能为193.2 kJ/mol,结果说明该陶瓷刚玉磨料的烧结化过程由扩散机制控制。

φ-pH diagram of V-Ti-H_2O system during pressure acid leaching of converter slag containing vanadium and titanium

To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.

温度和气氛对CaO-SiO2-Al2O3-MgO-FetO渣系FetO活度的影响

采用Mo|Mo+MoO2|ZrO2(MgO)|Fe+(FetO)+Ag|Fe固体电解质电池测定不同温度和气氛条件下定组成CaO-SiO2-Al2O3-MgO-FetO五元渣系的FetO活度。结果表明,当Ar作为保护气氛时,温度由1 673 K升高到1 785 K,炉渣的FetO活度变化不明显。当气氛中CO,CO2和Ar组成固定时,炉渣的FetO活度随温度的升高而增大。温度为1 673 K时,炉渣的FetO活度随着气氛中CO2/CO的增加而增大。温度和气氛对渣系FetO活度的影响均通过体系的O2分压实现。

CaO-SiO_2-FeO体系中选择性分离锌铅的实验研究

为了探讨CaO-SiO2-FeO体系中选择性分离回收Zn,Pb的可行性,在系统分析该体系中Zn,Pb挥发行为的基础上,研究了温度、基体成分及Cl含量等因素如对Zn,Pb挥发率的影响.结果表明,低温、低碱度、低FeO含量、低Cl含量条件下,Zn与Pb的挥发率差异达到最大,原因在于该种条件下Zn倾向于以ZnFe2O4等复杂化合物形式滞留在渣基体中,而Pb以氯化物形式挥发;在此基础上,对实验后的渣基体进行升温、并添加一定量的C粉等还原剂后,渣中Zn会以单质形式挥发分离,从而实现粉尘及飞灰熔融处理过程中Zn、Pb的选择性分离回收.

CaO-SiO_2-Na_2O-CaF_2-Al_2O_3-MgO渣系的结晶温度

通过差热分析仪测定了CaO SiO2 Na2 O CaF2 Al2 O3 MgO系连铸结晶器保护渣的结晶温度。在本实验渣系条件下 ,连铸保护渣的结晶温度随着渣中CaO SiO2 值、Na2 CO3含量、CaF2 含量和MgO含量的增加而升高 ,随着渣中Al2 O3含量的增加而降低。化学成分通过改变粘度 ,来影响晶核形成速度和晶体成长速度 ,从而决定了连铸保护渣的结晶性能。