烧结矿粘结相的熔化特性

以高碱度烧结矿中的铁酸盐粘结相为研究对象,考察了粘结相的熔化特性随粘结相组成的变化规律.通过试验探讨了不同nCaO∶nFe2O3以及不同的w(Mg),w(MgO2),w(SiO2)和w(Al2O3)铁酸盐粘结相的熔化特性.结果表明,nCaO∶nFe2O3=1∶1时,粘结相的熔化温度最低,熔化时间最短;添加MgO粘结相的熔化温度升高,熔化时间变长;当w(SiO2)或w(Al2O3)为3%时,粘结相的熔化温度最低,熔化最快.     

Origin of middle Miocene leucogranites and rhyolites on the Tibetan Plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary

Leucogranites play a significant role in understanding crustal thickening, melting within continental collisional belts, and plateau uplift. Field investigations show that Miocene igneous rocks from the Hoh Xil Lake area mainly consist of two-mica leucogranites and rhyolites. We studied the Bukadaban two-mica leucogranites and the Kekao Lake, Malanshan and Hudongliang rhyolites by zircon U-Pb, muscovite and sanidine 40Ar/39Ar geochronology, and whole-rock geochemical and Sr-Nd isotopic analysis. Results yielded crystallization and cooling ages for the Bukadaban leucogranites of 9.7±0.2 and 6.88±0.19 Ma, respectively. Extrusive ages of the Kekao Lake and Malanshan rhyolites are 14.5±0.8 and 9.37±0.30 Ma, respectively. All rocks are enriched in SiO2 (70.99%-73.59%), Al2O3 (14.39%-15.25%) and K2O (3.78%-5.50%) but depleted in Fe2O3 (0.58%-1.56%), MgO (0.11%- 0.44%) and CaO (0.59%-1.19%). The rocks are strongly peraluminous (A/CNK=1.11?1.21) S-type granites characterized by negative Eu anomalies (δ Eu=0.18-0.39). In also considering their Sr-Nd isotopic compositions (87Sr/86Sri=0.7124 to 0.7143; δ Nd (9 Ma) =-5.5 to -7.1), we propose that these igneous rocks were generated through dehydration melting of muscovite in the thickened middle or lower crust of northern Tibet. Melting was probably triggered by localized E-W stretching decompression in the horse tails of Kunlun sinistral strike-slip faults. Reactivation of the Kunlun strike-slip faults, accompanied by emplacement of leucogranite and eruption of rhyolite in the Hoh Xil Lake area, indicates that large-scale crustal shortening and thickening in northern Tibet mainly occurred before 15 Ma. In addition, these findings suggest that the northern Tibetan Plateau attained its present elevation (~5000 m) at least 15 Ma ago.     

LF精炼过程中SAE8620钢所含MgO复合夹杂物分析

采用非水溶液电解的方法,萃取分离出SAE8620齿轮钢中含MgO复合夹杂物,利用扫描电镜、能谱分析仪对夹杂物的组成、类型和形貌特征进行分析。结果表明,SAE8620齿轮钢在LF精炼过程中,含MgO复合夹杂物中MgO、CaO含量逐渐增加,SiO2含量逐渐减少,Al2O3含量呈先上升后下降的趋势;夹杂物的形貌多不规则,呈块状且棱角分明;夹杂物类型主要为SiO2-Al2O3-MgO、SiO2-MgO、SiO2-Al2O3-CaO-MgO等,此类夹杂物的尺寸较大、熔点较高,直接影响钢材的质量和使用性能。     

Effect of slag composition on the cleanliness of 28MnCr5 gear steel in the refining processes

The equilibrium reaction between CaO—Al₂O₃—SiO₂—MgO slag and 28MnCr5 molten steel was calculated to obtain the suitable slag composition which is effective for decreasing the oxygen content in molten steel. The dissolved oxygen content [O] in molten steel under different top slag conditions was calculated using a thermodynamic model and was measured using an electromotive force method in slag–steel equilibrium experiments at 1873 K. The relations among [O], the total oxygen content (T.O), and the composition of the slag were investigated. The experimental results show that both [O] and T.O decrease with decreasing SiO₂ content of the slag and exhibit different trends with the changes in the CaO/Al₂O₃ mass ratio of the slag. Increasing the CaO/Al₂O₃ mass ratio results in a decrease in [O] and an increase in T.O. To ensure that T.O ≤ 20 ppm and [O] ≤ 10 ppm, the SiO₂ content should be controlled to <5wt%, and the CaO/Al₂O₃ mass ratio should be in the range from 1.2 to 1.6.     

Effect of aluminum oxide on the compressive strength of pellets

Analytical-reagent-grade Al₂O₃ was added to magnetite ore during the process of pelletizing, and the methods of mercury intrusion, scanning electron microscopy, and image processing were used to investigate the effect of Al₂O₃ on the compressive strength of the pellets. The results showed that, as the Al₂O₃ content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al₂O₃ was added to the pellets, the Al₂O₃ combined with fayalite (2FeO·SiO₂) and the aluminosilicate (2FeO·2Al₂O₃·5SiO₂) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al₂O₃ increased sequentially, high melting point of Al₂O₃ particles hinder the oxidation of Fe₃O₄ and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.     

Al2O3对高炉渣物化性能影响的理论分析

随着优质铁矿资源的消耗,钢铁企业可利用的铁矿原料品位逐渐降低。因此,高铝质铁矿资源越来越受到钢铁企业的关注,但高铝原料在高炉冶炼过程中会带来渣铁黏稠、炉温偏低、冶炼安全等一系列问题。本研究中采用FactSage热力学软件分析Al₂O₃质量分数对高炉渣平衡物相、熔化温度、相析出温度的影响以及高铝渣液相区变化和黏度变化,旨在为高炉冶炼高铝原料提供一定的基础支撑。研究发现：炉渣为低铝（5%～10%）含量时,随着Al₂O₃含量增加,炉渣熔化温度升高,析出相为黄长石相和纯物质相,高炉渣黏度变化不大,炉渣中SiO₂含量高,炉渣黏度过高,不适合高炉冶炼;炉渣为中铝（10%～15%）含量时,随着Al₂O₃含量增加,炉渣熔化温度升高,析出相为尖晶石相、黄长石相和纯物质相,高炉渣黏度增加幅度略有提高,Al₂O₃含量对高炉渣性质影响较小,增加炉渣二元碱度对炉渣黏度降低效果较明显;炉渣为高铝（15%～30%）含量时...     

Heteroseneous oxidation of carbonyl sulfide on mineral oxides

Heterogeneous oxidation of carbonyl sulfide （OCS） on mineral oxides including SiO2, Fe2O3, CaO, MgO, ZnO and TiO2, which are the main components of atmospheric particles, were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy （in situ DRIFTS）, ion chromatography （IC）, temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely, OCS can be catalytically oxidized to produce surface SO4^2- species and gaseous CO2 through the surface hydrogen thiocarbonate （HSCO2-） and HSO; species. The activity series for heterogeneous oxidation of OCS follows： Al2O3 ≈ CaO 〉 MgO 〉 TiO2 ≈ ZnO 〉 Fe2O3 〉 SiO2. The specific area, basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS.     

添加剂对准东煤灰熔融特性的影响

以4种典型的准东煤为煤样,利用SiO2-CaO-Al2O3三元系统相图分析了准东煤结渣倾向性的变化,并采用灰熔融温度测试仪研究煤灰化学成分和灰熔融性的关系,寻求提高准东煤灰熔融温度的方法.结果表明,根据三元相图的灰熔融性趋势,预测添加适量的氧化物添加剂可以提高煤灰的熔融温度,并通过试验进行验证.发现神华煤分别添加5%的CaO和5%的Al2O3,可以显著地提高煤灰熔融温度;SiO2对准东煤灰熔点的影响具有两面性.研究结果为准东煤的实际工业应用提供了理论依据,考虑到经济性,电厂、工业锅炉可以添加石英砂、高矾土、石灰石的混合物,使其更好地解决准东煤问题.     

添加剂对准东煤灰熔融特性影响的研究

以四种典型的准东煤为煤样,利用SiO₂-CaO-Al₂O₃三元系统相图分析了准东煤结渣倾向性的变化,并采用灰熔融温度测试仪研究煤灰化学成分和灰熔融性的关系,寻求提高准东煤灰熔融温度的方法。结果表明,根据三元相图的灰熔融性趋势,添加适量的氧化物添加剂可以提高煤灰的熔融温度,实验中神华煤添加5%的CaO,5% Al₂O₃的可以显著的提高煤灰熔融温度。研究结果为准东煤在实际工业应用提供理论依据。     

高铝钢精炼渣的热力学计算与分析

为了在高铝钢中得到最低的溶解氧含量,必须找到CaO-Al2O3-MgO体系中Al2O3活度最低点的位置。因此,利用炉渣结构的共存理论,结合CaO-Al2O3-MgO相图,利用Matlab软件计算了CaO-Al2O3-MgO体系中Al2O3活度。通过对不同模型计算出的CaO-Al2O3渣系中Al2O3活度值比较,表明其变化趋势基本相同。由共存理论对CaO-Al2O3-MgO体系中Al2O3活度进行计算得到,在一定的MgO含量下,随着CaO含量增加,炉渣中Al2O3活度降低;在一定的CaO含量下,随着MgO含量增加,炉渣中Al2O3活度降低,且Al2O3活度最低值在CaO和MgO均达饱和的区域。     

In situ reaction mechanism of MgAlON in Al-Al2O3-MgO composites at 1700℃ under flowing N2

The Al-Al₂O₃-MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M₁, M₂, and M₃, respectively, were prepared at 1700℃ for 5 h under a flowing N₂ atmosphere using the reaction sintering method. After sintering, the Al-Al₂O₃-MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M₁ was composed of MgO and MgAl₂O₄. Compared with specimen M₁, specimens M₂ and M₃ possessed MgAlON, and its production increased with increasing aluminum addition. Under an N₂ atmosphere, MgO, Al₂O₃, and Al in the matrix of specimens M₂ and M₃ reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al₂O₃-MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N₂ atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al₂O₃-MgO composites were soaked at 580℃ for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al₂O₃ diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al₂O₃ to form MgAl₂O₄. When the temperature was greater than (1640 ±10)℃, AlN diffused into Al₂O₃ and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl₂O₄ at high temperatures because of their similar spinel structures.     

铁酸钙粘结相自身强度的研究

以烧结矿中的铁酸钙粘结相为研究对象,考察了粘结相自身的抗折、抗压强度随粘结相组成的变化规律.实验考察了不同n(CaO)∶n(Fe2O3)(摩尔比)以及MgO,SiO2和Al2O3含量对铁酸钙粘结相的抗折、抗压强度的影响规律.结果表明,n(CaO):n(Fe2O3)=1∶2时,粘结相的抗折、抗压强度最高,添加MgO使粘结相抗折、抗压强度下降,适量的SiO2(w(SiO2)<3%)能提高粘结相的抗折、抗压强度,但随Al2O3含量的增加,粘结相的抗折、抗压强度下降.     

铝热自蔓延制备CuCr合金渣系粘度测量及模型建立(Ⅱ)

用已建立的针对非二氧化硅体系的粘度模型对CaO Al2O3体系的粘度值进行估算,与前人的测量值进行了比较,估算值和文献测量值吻合·根据已知文献确定了CaO Al2O3体系中的Al3+和Ca2+的离子作用系数L·由测量知,CaO Al2O3体系共晶点附近的熔渣流动性好,在1460℃时粘度值低于0 5Pa·s·对于Al2O3 CaO MgO体系按两个不同共晶点处的成分配渣,其中含氧化钙较多的渣粘度较低,1500℃时,其粘度小于0 03Pa·s·添加剂MgO能显著降低CaO Al2O3体系的熔渣粘度·     

Mineralogical and sink-float studies of Jajarm low-grade bauxite

Jajarm’s bauxite deposits are mainly diasporic, and they have a low mass ratio of Al₂O₃/SiO₂. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al₂O₃ and 13.35wt% SiO₂, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000+710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350+710, -710+212, and -212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al₂O₃/SiO₂ mass ratios of 5.03, 5.16, and 5.15 for the -3350+710, -710+212, and -212+125 μm sizes, respectively.     

LF炉合成精炼渣成分优化

通过建立二次回归正交设计模型,考察了合成精炼渣碱度w(CaO)/w(SiO2),Al2O3和CaF2质量分数对LF深脱硫效果的影响.结果表明,当渣中w(FeO)为0.5%,w(MgO)为9%时,随渣中w(CaO)/w(SiO2)增加,脱硫率均先增大后减小.当w(CaO)/w(SiO2)不同时,Al2O3和CaF2质量分数对脱硫效果的影响程度不同,主要原因是渣中有效CaO含量变化引起的.随渣中w(FeO)降低和渣量增加,脱硫率明显增大.实验优化的最佳脱硫渣系组成为w(CaO)/w(SiO2)=9~11,w(Al2O3)=27%~29%,w(MgO)=9%,w(CaF2)=8%~10%,w(FeO...     

Modification of MgO·Al<Subscript>2</Subscript>O<Subscript>3</Subscript> spinel inclusions in Al-killed steel by Ca-treatment

The modification of MgO·Al₂O₃ spinel inclusions in Al-killed steel by Ca-treatment has been studied by industrial trials and thermodynamic calculations. In the industrial trials, samples were taken systematically during the refining process in which the molten steel was treated by calcium, and the characters of the inclusions were analyzed using scanning electron microscopy (SEM) and energy dispersive spectra (EDS). The effects of Ca-treatment were evaluated by tracking the compositions of the inclusions. The results show that the modification of MgO·Al₂O₃ spinel inclusions by Ca-treatment is effective and the transformation sequence of the inclusions during the refining is Al₂O₃→MgO·Al₂O₃→liquid complex inclusions. The modification of spinel inclusions by Ca-treatment was calculated by FactSage6.0 utilizing its free-energy minimization routines. The results of thermodynamic calculations indicate that spinel inclusions are easier to be modified than Al₂O₃ inclusions and the spinel inclusions in 30CrMo steel would transform to liquid complex inclusions when the content of dissolved Ca in the molten steel exceeds 1×10⁻⁶. Also, the results show that adding more calcium into the molten steel would lower the contents of Al₂O₃ and MgO and increase the CaO content of the inclusions, while the change in SiO₂ content is little.     

镍渣表面理化特性及对Pb2+、Cu2+的吸附研究

利用多种表征手段对镍渣的组成和表面特性进行分析,证实了镍渣具备吸附废水中重金属的能力。本实验所采用的水淬二次镍渣中含有含量较高的SiO₂、Al₂O₃、CaO、MgO等活性成分,且具备由不同聚合度的Si-O四面体、Al-O四面体或Al-O八面体组成的岛状、链状或网状骨架结构,能够通过离子交换和专性吸附去除溶液中的重金属离子。此外,镍渣粉体表面的碱中心可以为金属阳离子提供有效的吸附位点,且表面在pH=4~12的范围内均带负电,这些都有利于金属阳离子的吸附。镍渣粉体对模拟废液中的Pb²⁺、Cu²⁺吸附实验结果显示,其对废液中的Pb²⁺、Cu²⁺均表现出较好的吸附效果,且对Pb²⁺表现出更好的选择性吸附效果。     

基于铁矿粉液相流动性的塞拉利昂高铝铁矿配矿研究

以塞拉利昂高铝铁矿粉及其他5种烧结常用铁矿粉为原料,通过添加CaO、SiO2、Al2O3纯试剂改变铁矿粉中三种组分的含量,并分析了其对铁矿粉液相流动性的影响,比较了6类铁矿粉液相流动性对SiO2、Al2O3含量的敏感性差异,研究了混合矿粉液相流动性随塞拉利昂高铝铁矿粉配比的变化并进行了烧结试验。结果表明,随着CaO配比的增加,铁矿粉的液相流动性变好,其中塞拉利昂高铝铁矿粉变化的幅度最大;SiO2含量对塞拉利昂高铝铁矿粉液相流动性的影响较Al2O3含量更为明显;随着塞拉利昂高铝铁矿粉配比增加,混合矿粉的液相液动性指数降低,烧结矿的强度和成品率下降。     

Experimental study on dehydration melting of natural biotite-plagioclase gneiss from High Himalayas and implications for Himalayan crust anatexis

Here we present the results of dehydration melting, melt morphology and fluid migration based on the dehydration melting experiments on natural biotite-plagioclase gneiss performed at the pressure of 1.0—1.4 GPa, and at the temperature of 770—1028℃. Experimental results demonstrate that: (ⅰ) most of melt tends to be distributed along mineral boundaries forming “melt film” even the amount of melt is less than 5 vol%; melt connectivity is controlled not only by melt topology but also by melt fraction; (ⅱ) dehydration melting involves a series of subprocesses including subsolidus dehydration reaction, fluid migration, vapor-present melting and vapor-absent melting; (ⅲ) experiments produce peraluminous granitic melt whose composition is similar to that of High Himalayan leucogranites (HHLG) and the residual phase assemblage is Pl+Qz+ Gat+Bio+Opx± Cpx+Ilm/Rut± Kfs and can be comparable with granulites observed in Himalayas. The experiments provide the evidence that biotite-plagioclase gneiss is one of source rocks of HHLG and dehydration melting is an important way to form HHLG and the granulites. Additionally, experimental results provide constraints on determining the P-T conditions of Himalayan crustal anatexis.     

高Al2O3钒钛炉渣熔化性能的实验研究

针对炉渣中Al2O3,TiO2质量分数大幅升高给高炉冶炼带来极大困难的问题.对承钢高Al2O3钒钛炉渣进行了熔化性能的实验研究.结果表明:考虑承钢的实际情况,高炉的炉渣温度应高于1400℃;二元碱度控制在1.02左右,MgO质量分数控制在13.95%左右;Al2O3质量分数控制在12%~14%;TiO2的质量分数应控制在12.57%以下.