SiO2基酸化剂高温消解转炉钢渣中游离CaO的研究

转炉钢渣中游离CaO的水化膨胀是导致转炉钢渣体积安定性不良的重要原因。通过高温配加SiO_2基酸化剂,改变w(SiO_2)/w(CaO)对转炉钢渣进行稳钙改质处理。利用化学检测分析、X射线衍射和场发射扫描电子显微镜对SiO_2基酸化剂高温消解转炉钢渣中游离CaO的效果和特征进行研究。结果表明,改质后的转炉钢渣的w(SiO_2)/w(CaO)在0.37以上,就能满足钢渣中f-CaO低于3%的水泥和混凝土行业使用标准,且消解率达到60%以上,而当w(SiO_2)/w(CaO)为0.67时,f-CaO低于1%,且消解率达到90%以上;改质前后转炉钢渣的矿相组成有明显差异,改质后转炉钢渣以硅酸二钙、镁黄长石、镁铁尖晶石、磁铁矿和铁铝酸钙相为主,并且镁黄长石相随着w(SiO_2)/w(CaO)的增大而增多;转炉钢渣酸化稳钙前f-CaO被紧密包裹在矿相基体中,高温酸化改质后,团簇状聚集的f-CaO颗粒会嵌在硅酸盐相间,无明显包裹现象,尺寸为0.5~2μm。     

电磁场对低碳MgO-C耐火材料渣蚀性能的影响研究

采用碳含量为6％的低碳MgO-C耐火材料和CaO/SiO2为0.8的渣,分别在中频感应炉和电阻炉中进行渣蚀实验.对在不同环境下渣蚀后的试样进行X射线衍射( x-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)和EDAX分析.结果表明,感应炉环境中存在电磁场,其渣蚀试样渗透层中高温相结构紧密,在界面处形成镁铁固溶体( Mg1-x FexO)和镁锰固溶体(Mg1x MnxO),低熔相主要为含少量铁锰氧化物的钙镁橄榄石[Ca Mg( Fe、Mn)SiO4].电阻炉中无电磁场,渣蚀试样界面没有固溶体形成,低熔相主要为硅酸钙(CaSiOa)、镁蔷薇辉石(Ca3MgSi2O8)和钙镁橄榄石(CaMgSiO4).在高温下,电磁场的存在提高了Fe2+/3+,Mn2的扩散系数,以及与镁砂中Mg2的置换能力,有助于形成镁铁固溶体和镁锰固溶体.无论有无电磁场作用,渗透层都有镁铝尖晶石( MgAl2O4)生成.电磁场环境加剧了熔渣对MgO-C耐火材料的侵蚀.     

CaO/SiO2质量比对不锈钢渣微晶玻璃析晶及性能的影响

以不锈钢渣、废玻璃为原料,采用熔融法制备了主晶相为硅灰石相的微晶玻璃.利用DSC、XRD、SEM等测试分析手段研究了CaO/SiO2质量比对微晶玻璃物相组成、显微结构及理化性能的影响.结果表明:随CaO/SiO2质量比增加,玻璃转变温度和析晶放热峰温度逐渐降低,且析晶放热峰变尖锐;硅灰石相XRD衍射峰强度先增强后减弱;显微结构由表面析晶向整体析晶过渡,晶粒形状由球形颗粒变为针叶状晶,最后发育成片状晶,晶体尺寸先增加后减小;当CaO/SiO2质量比为0.72时微晶玻璃性能达到较优,显微硬度为6.49 GPa,密度为3.11 g/cm3,吸水率为0.11％,耐酸性96.51％,耐碱性99.92％.制备出的微晶玻璃有望应用在建筑装饰材料领域.     

CaO-SiO2-FeO-MgO体系钢渣的氧化改质动力学研究

通过高温煅烧的方式对工业BOF钢渣进行氧化改质.借助热力学分析,利用XRD、SEM-EDS和湿式磁选对改质前后钢渣矿物相进行研究,证实了氧化改质后钢渣中无磁性氧化亚铁向磁性尖晶石相转变并可通过湿式磁选选出,氧化改质最佳温度为1 100℃.对CaO-SiO2-FeO-MgO体系钢渣的氧化进行进一步热力学和动力学分析,并与文献中已有CaO-SiO2-FeO体系钢渣研究进行对比.结果表明,成分中镁的添加有益于磁性尖晶石相在空气中生成.钢渣的氧化过程可以被分为三个阶段:初始阶段、化学反应阶段和扩散阶段.     

Na2O对低SiO2保护渣理化性质的影响

高铝钢中活泼元素Al易与保护渣中的SiO2发生氧化还原反应,导致致使保护渣的各种理化性质显著改变,连铸工艺难以稳定。于是设计了低SiO2保护渣,并研究了Na2O含量对其熔融特性、粘度特性、及结晶特性渣的影响。结果表明：当w（Na2O）从6％增加到12％,保护渣熔化温度、粘度、粘流活化能均降低;保护渣的等温转变曲线向孕育时间增加的方向移动。     

高温质子交换膜燃料电池用Nafion(R)/SiO2 复合膜研究进展

传统的质子交换膜燃料电池在高温下工作时,质子膜会因温度升高而发生脱水和膜电阻升高的现象,这对提高燃料电池的工作性能是一个致命的阻碍.由于Nafion(R)/SiO2复合膜具有较好的吸水和保水性能和较好的阻止甲醇渗透的能力,人们通过溶胶-凝胶法或重铸法合成了Nafion(R)/SiO2复合膜,并于高温(80～140℃)下应用在质子交换膜燃料电池和直接甲醇燃料电池中.简单介绍了Nafion(R)/SiO2复合膜的制备方法、结构性能及研究情况,并分析了存在的问题和其广阔的应用前景.     

高温质子交换膜燃料电池用Nafion®/SiO2 复合膜研究进展

传统的质子交换膜燃料电池在高温下工作时,质子膜会因温度升高而发生脱水和膜电阻升高的现象,这对提高燃料电池的工作性能是一个致命的阻碍.由于Nafion(R)/SiO2复合膜具有较好的吸水和保水性能和较好的阻止甲醇渗透的能力,人们通过溶胶-凝胶法或重铸法合成了Nafion(R)/SiO2复合膜,并于高温(80～140℃)下应用在质子交换膜燃料电池和直接甲醇燃料电池中.简单介绍了Nafion(R)/SiO2复合膜的制备方法、结构性能及研究情况,并分析了存在的问题和其广阔的应用前景.     

钒渣组成对V_2O_3溶解能力的影响

利用高温淬火方法得到钒渣渣系的高温物相,采用X-ray衍射分析方法确定钒渣的物相组成,分别研究了V2O3含量及n(FeO)/n(SiO2)对钒渣中V2O3溶解能力的影响。结果表明,钒铁尖晶石和Fe3O4为钒渣中存在的固定相;钒渣中V2O3含量不断增加,V2O3的溶解度随之增加,但n(FeO)/n(SiO2)1.5,V2O3增加到一定量时,溶解度无明显变化;n(FeO)/n(SiO2)不断增大,V2O3在钒渣中的极限溶解度也随之增加。     

Al/SiO2复合粒子制备及其催化性能研究

文章利用溶胶一凝胶法,以超细铝粉为核,SiO2为膜,制备了包覆式超细Al／SiO2复合粒子。采用扫描电镜、X射线光电子能谱、红外光谱等方法对包膜的效果进行了表征分析。分析结果表明：制备的Al／SiO2复合粒子表面的SiO2膜均匀致密。运用差热分析法（DTA）研究了制备的肼SiO2复合粒子对高氯酸铵（AP）热分解性能的影响。结果表明：与添加5％纯Al粉的AP相比,添加5％Al／SiO2复合粒子的AP,其高温放热峰温降低了29．73℃,表观分解热增加了616．8J／g。表明Al／SiO2复合粒子比纯Al粉对AP热分解具有更好的催化作用。     

PP/TPU/纳米SiO2复合材料的制备与性能研究

采用熔融共混法制备了聚丙烯(PP)/热塑性聚氨酯弹性体(TPU)/纳米SiO2复合材料,研究了复合材料的力学性能、结晶性能、流变性能.研究结果表明,填充5%的TPU和极少量纳米SiO2具有协同增强和增韧效应;PU能诱导PPβ晶的形成,纳米SiO2的用量影响其诱导作用;纳米SiO2对PP/TPU有一定的增容作用,使复合材料体系的模量与黏度增大.     

A discussion on improving hydration activity of steel slag by altering its mineral compositions

This study aims to investigate the ways to improve the cementitious properties of steel slag. The results show that the cementitious phase of steel slag is composed of silicate and aluminate, but the large particles of these phases make a very small contribution to the cementitious properties of steel slag. RO phase (CaO-FeO-MnO-MgO solid solution), Fe(3)O(4), C(2)F and f-CaO make no contribution to the cementitious properties of steel slag. A new kind of steel slag with more cementitious phase and less RO phase can be obtained by removing some large particles. This new steel slag possesses better cementitious properties than the original steel slag. The large particles can be used as fine aggregates for concrete. Adding regulating agent high in CaO and SiO(2) during manufacturing process of steel slag to increase the cementitious phase to inert phase ratio is another way to improve its cementitious properties. The regulating agent should be selected to adapt to the specific steel slag and the alkalinity should be increased as high as possible on the premise that the f-CaO content does not increase. The cooling rate should be enhanced to improve the hydration activity of the cementitious phase at the early ages and the grindability of steel slag.     

富硼渣钠化法制备硼砂的实验研究

采用X射线衍射分析(XRD)方法分析表明,富硼渣中的硼组分主要以Mg2B2O5形式存在,而钠化渣中的硼组分以Na4B2O5和NaBO2晶相形式析出.为提取富硼渣中的硼,考察了热处理温度、碳酸钠加入量、热处理时间、水浸温度等因素对钠化渣中硼浸出率的影响.同时考察了富硼渣中w(Al2O3)、w(CaO)、w(B2O3)、m...     

Characterization and activation of Basic Oxygen Furnace slag

BOF slags are by-products of steel conversion. They are a valuable mineral resource for the construction but have chemical properties that directly control their stability or any hydraulic activity. This paper provides a complete characterization and quantification of BOF slag phases in order to better understand their potential hydraulic activity. The acceleration of the hydration by chemical admixtures is also presented. The BOF slag variability is investigated on several samples with different origins and ages.BOF slag with different origins mainly contain 38-52% C₂S, 20-30% C₂F, 1-7% Ca(OH)₂, 11-13% Fe_1−xO, 2-8% CaO. Calcium silicate is present in β-C₂S form which is the active polymorph present in clinker. BOF slags have poor hydraulic activity at early ages which can be enhanced by calcium chloride addition.     

Investigation on the effect of MgO content on the crystallization behavior of synthetic BF slag

The crystallization of molten blast furnace (BF) slag can increase its viscosity and reduce its liquidity; it can also affect the quality of slag fibers following their manufacture. The crystallization behavior of BF slag is influenced by its chemical composition. In this study, four synthetic BF slags with various MgO contents, ranging from 6 to 12%, were investigated. FactSage simulations were performed to predict the types of crystallized phases as well as their mass fractions that are developed within the synthetic BF slags during the cooling process. To verify the validity of FactSage simulation, X-ray diffraction and scanning electron microscope–backscattered electron imaging, where the equipment was coupled to an energy-dispersive spectrometer, were performed to explore the mineralogical compositions and morphologies of the synthetic BF slags. Experiments using the hot thermocouple technique were performed to identify the initial crystallization temperatures of the synthetic BF slags. The results indicate that the observed phases of the synthetic BF slags were primarily composed of akermanite (2CaO?·?MgO?·?2SiO₂) and gehlenite (2CaO?·?Al₂O₃?·?SiO₂), which could form a solid solution, melilite, and control the initial crystallization temperature. The initial crystallization temperature increased as the MgO content of the slag increased. A low initial crystallization temperature was achieved in the cases of the synthetic BF slag samples with MgO contents of 6–8%; these slags were considered suitable for the manufacture of slag fiber.     

镍渣资源化利用现状及发展趋势分析

镍渣含Fe 40%~45%,SiO_232%~36%,MgO 1%~11%,CaO 1%~3%(质量分数),并含少量的镍、铜、钴等有价金属,是重要的二次资源。介绍了典型镍渣成分及物相,总结了镍渣提取有价金属、作井下填充材料、生产微晶玻璃、制备建材等资源化利用工艺的技术要点,分析了现有工艺存在的问题,提出了镍渣直接还原提铁及协同制备胶凝材料的绿色利用思路,介绍了初步研究结果,探讨了进一步资源化的方向。     

Treatment of petroleum-hydrocarbon contaminated soils using hydrogen peroxide oxidation catalyzed by waste basic oxygen furnace slag

The contamination of subsurface soils with petroleum hydrocarbons is a widespread environmental problem. The objective of this study was to evaluate the potential of applying waste basic oxygen furnace slag (BOF slag) as the catalyst to enhance the Fenton-like oxidation to remediate fuel oil or diesel contaminated soils. The studied controlling factors that affect the removal efficiency of petroleum hydrocarbons included concentrations of H₂O₂, BOF slag dosages, types of petroleum hydrocarbons (e.g., fuel oil and diesel), and types of iron mineral. Experimental results indicate that oxidation of petroleum hydrocarbon via the Fenton-like process can be enhanced with the addition of BOF slag. Results from the X-ray powder diffraction analysis reveal that the major iron type of BOF slag/sandy loam system was iron mineral (e.g., α-Fe₂O₃ and α-FeOOH). Approximately 76% and 96% of fuel oil and diesel removal were observed (initial total petroleum hydrocarbon (TPH) concentration = 10,000 mg kg⁻¹), respectively, with the addition of 15% of H₂O₂ and 100 g kg⁻¹ of BOF slag after 40 h of reaction. Because BOF slag contains extractable irons such as amorphous iron and soluble iron, it can act as an iron sink to supply iron continuously for Fenton-like oxidation. Results demonstrate that Fenton-like oxidation catalyzed by BOF slag is a potential method to be able to remediate petroleum-hydrocarbon contaminated soils efficiently and effectively.     

Mechanical properties and microstructure of steel/iron slag blended mortar

This study aims to examine the mechanical properties and microstructures of steel/iron slag blended mortar (SISBM), which contains two by-products of the steel and iron industries: steel slag (basic oxygen furnace slag, BOFS) and iron slag (blast furnace slag, BFS). Test results indicate that steel slag will have effective hydration reactions with iron slag and contribute strength. The optimal mixing ratio of steel to iron slags was 3:7 (by weight), and the compressive strength was about 83.59% compared with that of ordinary Portland cement mortar (OPM). The strength development was similar to that of OPM and the strength increased as the curing period increased. The X-ray diffraction analysis results implied that the main products of hydration could be C–S–H, C–A–S–H, CaO–MgO–Al₂O₃–SiO₂, Fe_0.974O, and C₄AF. The scanning electron microscope images indicated that the distribution of Ca(OH)₂ and CaCO₃ increased as the inclusion of steel slag increased, perhaps resulting from insufficient reactions between BFS and Ca(OH)₂ and f-CaO due to excessive BOFS. In addition, the results indicated that the density of OPM was superior to that of SISBM. This may be the reason for lower strength of SISBM compared to OPM.     

电热还原法制备V-Ti-Cr-Fe储氢合金

采用电热还原热法制备了V-Ti-Cr-Fe合金,考察了CaO加入量、Al-Ca还原剂用量及精炼剂成分对制备效果的影响。结果表明,CaO和Al-Ca合金用量对Ti的收得率和合金中杂质含量影响显著,m(CaO)/m(Al)为0.9、m(Al-Ca)/m(Al)为0.5时的熔炼效果较好,Ti的收得率可达66%,Al、O杂质含量可分别达到3.66%和0.75%(质量分数)。以90%(3CaF_2-CaO)-10%V_2O_5(质量分数)渣体为精炼剂,采用喷吹造渣的精炼方法,可较有效地去除合金中的Al杂质,并能起到一定的预脱O作用,精炼后Al和O含量可分别降到1.23%和0.59%(质量分数)。SEM分析表明,未精炼的合金除了含有固溶体主相外,还含有很多氧化物夹杂相,而通过喷吹造渣精炼,夹杂相明显减少。     

Properties of hydraulic paste of basic oxygen furnace slag

Basic Oxygen Furnace (BOF) slags are by-products of the conversion of pig iron to steel. They mainly contain C₂S, C₂F, Fe_1−xO, CaO, Ca(OH)₂ and CaCO₃. According to their chemical composition they are a valuable mineral resource as additions in certain hydraulic binders. This paper presents a hydration study of the BOF slag pastes preserved at different temperatures and in different environments. Pastes are characterized by X-ray diffraction and scanning electron microscopy. The compressive strengths of hydrated pastes are given at 7, 28, 90 and 190 days. Results show that – BOF slags containing 40% of C₂S – have attractive mechanical properties. Hydration tests under water showed a pastes swelling due to the hydration of CaO contained in BOF slags. A lime extinction procedure was proposed as alternative to standard PR NF EN 13282-2. This approach is more effective for these materials: the volume expansion of pastes cured in water is avoided and the compressive strengths are thus significantly improved.     

Hazardous ions uptake behavior of thermally activated steel-making slag

This study concerns the utilization of waste steel-making slag, a by-product that contains mainly CaO, Fe(2)O(3) and SiO(2). The as-received slag was ground and thermally activated by temperature treatment from 110 to 1000 degrees C for 24 h. Although the as-received slag was amorphous, it became partially crystallized during grinding. These crystalline phases were larnite and iron oxide but other crystalline phases also appeared in addition to larnite after calcination. The uptake of Ni(2+), PO(4)(3-) and NH(4)(+) by the samples was investigated from solutions with initial concentrations of 10 mmol/l. The sample calcined at 800 degrees C showed the highest Ni(2+) uptake (4.85 mmol/g) whereas the highest simultaneous uptake of PO(4)(3-) (2.75 mmol/g) and NH(4)(+) (0.25 mmol/g) was achieved by calcining the material at 700 degrees C. The principal mechanism of Ni(2+) uptake is thought to involve replacement of Ca(2+) by Ni(2+). The mechanism of PO(4)(3-) uptake is mainly by formation of calcium phosphate while that of NH(4)(+) involves sorption by the porous silica surface of the samples.