Rheological behavior and constitutive equations of heterogeneous titanium-bearing molten slag

Experimental studies on the rheological properties of a Ca O–Si O2–Al2O3–Mg O–Ti O2–(Ti C) blast furnace(BF) slag system were conducted using a high-temperature rheometer to reveal the non-Newtonian behavior of heterogeneous titanium-bearing molten slag. By measuring the relationships among the viscosity, the shear stress and the shear rate of molten slags with different Ti C contents at different temperatures, the rheological constitutive equations were established along with the rheological parameters; in addition, the non-Newtonian fluid types of the molten slags were determined. The results indicated that, with increasing Ti C content, the viscosity of the molten slag tended to increase. If the Ti C content was less than 2wt%, the molten slag exhibited the Newtonian fluid behavior when the temperature was higher than the critical viscosity temperature of the molten slag. In contrast, the molten slag exhibited the non-Newtonian pseudoplastic fluid characteristic and the shear thinning behavior when the temperature was less than the critical viscosity temperature. However, if the Ti C content exceeded 4wt%, the molten slag produced the yield stress and exhibited the Bingham and plastic pseudoplastic fluid behaviors when the temperature was higher and lower than the critical viscosity temperature, respectively. When the Ti C content increased further, the yield stress of the molten slag increased and the shear thinning phenomenon became more obvious.

Roasting and leaching behaviors of vanadium and chromium in calcification roasting–acid leaching of high-chromium vanadium slag

Calcification roasting–acid leaching of high-chromium vanadium slag(HCVS)was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium.The effects of the purity of Ca O,molar ratio between Ca O and V_2O_5(n(Ca O)/n(V_2O_5)),roasting temperature,holding time,and the heating rate used in the oxidation–calcification processes were investigated.The roasting process and mechanism were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),and thermogravimetry–differential scanning calorimetry(TG–DSC).The results show that most of vanadium reacted with Ca O to generate calcium vanadates and transferred into the leaching liquid,whereas almost all of the chromium remained in the leaching residue in the form of(Fe_(0.6)Cr_(0.4))_2O_3.Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with Ca O.Moreover,Ca O was more likely to combine with vanadium,as further confirmed by thermodynamic analysis.When the HCVS with Ca O added in an n(Ca O)/n(V_2O_5)ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min,the leaching ratios of vanadium and chromium reached91.14%and 0.49%,respectively;thus,efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium.Furthermore,the oxidation and calcification reactions of the spinel phases occurred at 592and 630°C for n(Ca O)/n(V_2O_5)ratios of 0.5 and 5,respectively.

Thermodynamic Behavior of Manganese and Phosphorus between Liquid Iron and CaO-MgO-SiO_2-Al_2O_3-Fe_tO-MnO-P_2O_5 Slags

The thermodynamic behavior of manganese and phosphorus between liquid iron and CaO-MgO-SiO2-Al2O3-FetO-MnO-P2O5 ladle slag system was addressed by investigating the thermodynamic equilibria between liquid iron containing Mn and P and the ladle slag at 1873 K. The Mn distribution ratio L-Mn increases with increasing FetO content and decreasing the basicity ((%CaO + %MgO)/(%SiO2 + %Al2O3 + %P2O5)) in slag, while the P distribution ratio Lp seems to be increased as FetO content and the basicity increases. The values of L-Mn and L-p decrease by the addition of Al2O3 into slag. The expression of the dependence of L-Mn and L-p on the basicity and FetO content in slag was obtained.

Vaporization behavior of lead from the FeO-CaO-SiO_2-Al_2O_3 slag system

Vaporization behavior （1163-1463 K） of lead in the slag system of FeO-CaO-SiO2-Al2O3 with CaC% was examined. A thermodynamic estimation with the principle of Gibbs free energy minimization showed that the major vapor species from the sample of the FeO-CaO-SiO2-Al2O3 system＋PbO＋CaCl2 were metallic Pb, PbCl, PbCl2, and FeCl2, at the experimental temperature range. The experimental results show that the mole ratio of vaporized Cl in lead chlorides to vaporized Pb, simply expressed as Cl/Pb decreases with increasing temperature. The larger Cl/Pb means a larger ratio of gaseous PbCl2, since metallic Pb and PbCl vapors are formed in a similar reduction atmosphere. The evaporation is initially rapid and becomes steady after holding for 10 min. Gaseous PbCl2 is mainly formed during the heating period, and at the holding stage, it reacts with FeO to produce gaseous FeCl2 With regard to slag composition, FeO content and basicity significantly affect the evaporation of lead. High FeO content and high basicity promotes the formation of metallic Pb and PbCI, whereas, it prohibits PbCl2 evaporation.

Dissolution behavior of various elements from steelmaking slag into seawater

The mixture of steelmaking slag,soil or sand is a candidate material for the landfill in sea shore to improve the marine environment,because the ferrous ion contained in the steelmaking slag plays an important role in promoting the growth of various seaweeds.However,the dissolution mechanism of various elements from steelmaking slag into seawater is not clarified.To reveal the dissolution behavior of various elements from steelmaking slag into seawater,the dissolution experiment of slag and seawater mixture was conducted at room temperature with changing the basicity of slag and the mass ratio of slag and seawater.It is shown that Mg ion contained in the seawater plays a buffering action obviously on pH increase which is provided by the dissolution of Ca.The dissolution behavior of Si strongly depends on the basicity of slag,at the same time the mass ratio has a conspicuous influence on it for the lower basicity of slag.The dissolution amount of Fe is little and it is discussed by using the solubility diagram.

气流床气化炉中煤气化熔渣的结晶行为研究进展

煤气化是实现煤炭从燃料向原料转变,推进煤炭清洁高效利用的重要途径之一。气流床气化技术是目前的主流气化技术,气化炉的稳定运行要求液态熔渣应具有良好的流动性。排渣过程中的熔渣结晶行为会导致熔渣流动性变差,是造成气化炉非正常停车的主要原因。总结了影响熔渣流动性的主要结晶特征及研究结晶行为的关键——结晶动力学的研究现状。论述根据结晶行为判断结晶机制并选择合适的结晶动力学模型的方法。为获得更准确的结晶行为数据,总结多种结晶检测手段的原理和特点并分析了根据研究重点、仪器特性与熔渣特性选择合适结晶行为的检测手段。最后,论述了化学组成与操作条件对结晶行为的影响。研究发现不同晶体之间结晶机理差异明显,同一化学组成对不同晶体结晶行为的影响不同。当限定熔渣化学组成所处相区时,化学组成与操作条件对第一相结晶矿物质结晶行为的影响更具规律性,可为调控结晶行为提供更准确指导。研究结果与相图结合或建立简单易得的预测模型能更好指导熔渣结晶行为调控。目前,结晶行为研究主要依赖试验手段,后续研究可结合相场模拟与分子动力学模拟等方法,深入挖掘结晶机理,并考察气化炉内温度场、流场等因素对结晶特性的影响。

高硫塑料模具钢中硫稳定性控制基础研究

基于高硫塑料模具钢典型缺陷检测和MnS析出行为研究,结合热力学计算和工业试验探索了高硫塑料模具钢精炼过程硫稳定性控制手段。结果表明,MnS夹杂是裂纹产生的原因之一。MnS在1708 K开始析出,且优先发生位错形核。MnS发生晶界形核的最快沉淀析出温度为1573 K,并在铸坯加热过程明显长大。综合高硫塑料模具钢精炼顶渣物化性质、硫容量和硫分配比的理论研究,确定最优精炼顶渣成分范围:1.55≤(w(CaO)/w(SiO_(2)))≤1.7、24%≤w(Al 2O 3)≤28%、1.4≤(w(CaO)/w(Al 2O 3))≤2.3、7%≤w(MgO)≤9%和2.5%≤∑w(FeO+MnO)≤4.0%。精炼顶渣成分与精炼工艺优化后,VD出站到中包钢中硫平均降低质量分数由108×10-6减少至30×10-6,平均Al s损由24.9×10-6减少至14.2×10-6,实现了模具钢中硫稳定性和VD至中包Al s损的大幅度改善。

纳米SiO_(2)协同酸预处理对碱激发钢渣-矿渣泛碱行为的影响研究

为了降低泛碱行为对碱激发钢渣-矿渣材料造成的影响,该文采用硫酸预处理钢渣协同不同掺量纳米二氧化硅的处理方式,研究在不同模数的碱性环境中,纳米SiO_(2)协同酸处理对碱激发钢渣-矿渣材料泛碱行为的影响,同时测定钢渣基复合材料的胶砂强度,采用扫描电子显微镜(SEM)、压汞测试(MIP)对复合体系进行机理分析。结果表明:硫酸预处理钢渣与纳米SiO_(2)对碱激发钢渣-矿渣材料的泛碱行为具有协同改善作用。当水玻璃模数为1时,硫酸预处理钢渣且掺入质量分数为2%的纳米SiO_(2),其微观结构平整,孔结构得到优化,抗压强度最高,泛碱行为得到最大程度改善。

高炉渣矿质元素对马尼拉草生长的影响

高炉渣是炼铁过程中产生的副产品,含有丰富Ca、Si、Mg、Fe等植物生长所需的矿质元素,在农林领域应用前景广阔。以高炉渣为研究对象,将高炉渣与泥炭土混合后开展淋溶实验和马尼拉草盆栽实验,通过测定高炉渣与泥炭土混合物淋溶液元素溶出浓度,确定马尼拉草生物量、株高、根系形态等植物生长指标和叶绿素、可溶性糖和可溶性蛋白含量等生化指标,研究了高炉渣对土壤-马尼拉草生态系统的影响。结果表明:添加少量高炉渣会提升土壤中Si、Fe、Mn的溶出浓度,但当高炉渣添加量高于4%时,会造成土壤碱化、贫钾、贫磷和富铝化。当高炉渣添加量不高于4 wt.%时,土壤中高炉渣的加入会促进马尼拉草根系的发育,提高叶绿素、可溶性糖和可溶性蛋白的含量,进而促进其生长。与对照组相比,土壤中高炉渣添加量为4%时,马尼拉草的株高和生物量分别提升了19%和35%,可起到较好的固碳释氧效果。

Flexural Fatigue Behavior of Polypropylene Fiber Reinforced Segment Concrete

The influence of polypropylene fiber on the flexural fatigue performance of high-strength concrete (HSC), which could be used as cover of reinforcement of segment, was investigate by three-point load bending tests. Also, the flexural fatigue equations of high-strength concrete with and without polypropylene fiber were established through test analysis. The experimental results indicate that the addition of polypropylene fiber can improve the static bending strength of segment concrete, and the important is that it can markedly increase the flexural fatigue performance of the HSC subjected to cyclic bending load. Especially when with 1.37 kg/m3 addition of the fiber was corporate with silica fume and slag powder, the fatigue life of the HSC can be increased by 43.4% compared to that of the segment concrete without fiber, silica fume and slag.

配置参数对萘系减水剂在NaOH-矿渣水泥系统中的吸附行为影响研究

萘系减水剂是一种典型的高效减水剂,其在传统硅酸盐水泥系统中的积极作用得到大量的实践证实,但在新型胶凝材料碱矿渣水泥系统中的研究应用相对较少。该文从减水剂掺量、激发剂掺量、激发剂掺加方式和搅拌时间等配置参数的角度,研究了萘系减水剂在NaOH-矿渣颗粒表面的吸附行为,并对其作用机理进行探讨。研究结果显示:萘系减水剂在NaOH-矿渣水泥系统中的吸附量随减水剂掺量的增加而增大,随激发剂掺量的增大而减弱,随搅拌时间的延长而增长,且与激发剂的掺加方式无直接关系。

碱激发偏高岭土-矿渣砂浆的碱骨料反应机理研究

碱激发胶凝材料是一种新型低碳材料,其液相环境的碱度普遍高于水泥基材料,势必导致碱骨料反应引起的体积变形不同于水泥基材料。为探究碱激发胶凝材料的碱骨料反应行为与液相碱度的关系,选取花岗岩为代表性骨料制备碱激发偏高岭土-矿渣砂浆,研究在不同浓度NaOH溶液浸泡下的砂浆变形行为。结合微观分析表明,碱激发胶凝材料的体积收缩能很好地抑制碱骨料反应产生的膨胀,不同浸泡条件下碱激发偏高岭土-矿渣砂浆会呈现不同的变形行为。碱激发偏高岭土-矿渣砂浆的膨胀是由碱骨料反应生成产物以及原类沸石结构的水化硅铝酸钠凝胶向沸石结构转化所造成的。当碱激发胶凝材料的孔溶液氢氧根离子浓度大于0.209 mol/L时,碱骨料反应会发生。

含锌尘泥球团直接还原过程中渣相行为与固结强度关系研究

通过表征不同直接还原温度下碱性含锌尘泥球团外观形貌、物相组成、微观结构及抗压强度变化,并结合FactSage热力学计算,分析了碱性尘泥球团直接还原过程中渣相行为及其对球团固结强度的影响。结果表明,随着还原温度升高,碱性尘泥球团体积先膨胀后收缩,对应抗压强度也先减小后增加,碱性氧化物一直参与球团渣相的形成过程并最终形成复杂的含钙化合物渣相。固相反应是渣相形成的基础,其中间产物Ca 2SiO 4良好的固溶性促进了钙铁和钙镁低熔点物相的固相生成,铁氧化物的初步还原产物FeO有利于液相生成,促进球团中物相的迁移和重新排列,球团体积收缩,强度明显提高。

Inconel 625合金在富氧高温熔渣中的腐蚀行为

针对镍顶吹熔炼喷枪使用寿命低的问题,以Inconel 625合金为替代材料,采用挂片试验,研究了该合金在氧气流量为15000~42000 Nm^(3)/h,熔渣温度1400℃下的腐蚀行为及机理.采用金相显微镜、扫描电镜、能谱仪、电子探针及显微硬度计等分析了试样的组织形貌、元素分布及硬度.结果表明:15~20 h时Cr_(2)O_(3)等氧化膜的形成阻碍了氧化腐蚀的进行;合金的严重腐蚀区域发生在表面0~250μm,250~1650μm为热影响区;富Nb贫Cr区优先被腐蚀,随着由Cr_(2)O_(3)、Fe_(2)O_(3)、Cr_(2)S_(3)、Nb_(0.1)Ni_(0.9)、[Mg、Fe]_(2)SiO_(4)等构成的复杂氧化膜体系的不断形成与分解,合金中各主要元素不断腐蚀脱落,且氧化膜中的Mg、S元素来源于熔渣;腐蚀后的合金表面硬度明显降低.

Numerical Comparative Study on the Effective Replacement Thickness of Traditional Stone Coarse Aggregate or Steel-Slag Aggregate Mixtures in Improved Soft Fine Soils

This study uses Steel Slag Coarse Aggregate (SSCA) as a mixture replacement, preamble material to improve soft soils, which is economic, and has good effect environment. Recently, the development and utilization of by-product, waste and recycle materials must be studied and investigated as a source of improved material for soft soils as, an economic and good effect environmental. The study analyzes effects of both replaced mixtures, (SSCA) or (TSCA) on improved soil bearing capacity and expected settlement after verifying the model. Numerical modeling of the one of real store loaded strip using, PLAXIS, 2D, strain deformation behavior to achieve field visible and measured deformations of untreated soft soil. Numerical studies were devolved to investigate geomechanics parameters improved to compare between using (SSCA) or (TSCA) as, replacement mixture. Results demonstrate that using (SSCA) improved compressibility and strength of shallow soft soil layer significantly than using (TCSA) mixture, while (SSCA) improved strip footing ultimate bearing capacity, (UBC), by 84.4% compared with increase of 20.5% when using (TCSA) mixture at the same thickness. In addition, the study highlights the effective (SSCA) replacement thickness ranges between (0.65 ~ 0.80) footing width.

基于数字图像相关法的铝镁质耐火材料抗侵蚀性能研究

钢渣侵蚀是耐火材料在服役过程中的主要损毁形式之一,实际侵蚀过程难以直接观察。传统上采用蚀后分析方法来评价耐火材料的抗侵蚀能力和了解侵蚀机理,但易缺少过程信息,导致结果存在偏差。因此,本文在高温可视化系统基础上,结合数字图像相关法,选取三种典型钢渣,开展铝镁质耐火材料的渣蚀行为研究,并探讨了不同钢渣及热处理温度对材料抗侵蚀能力的影响。结果表明:碱度越低的熔渣对铝镁质耐火材料的侵蚀越严重;对铝镁质耐火材料进行1 000℃以上的热处理,可有效提高材料的抗侵蚀能力;通过数字图像相关法可以获得随时间变化的平均应变曲线和侵蚀应变云图,其中平均应变曲线可以对比铝镁质耐火材料对不同钢渣的抗侵蚀能力,侵蚀应变云图可以反映侵蚀的演变过程,两者为耐火材料渣蚀过程的表征提供了量化指标。

硫含量对KR脱硫渣中CaS氧化行为的影响

KR脱硫渣中主要成分(CaO)为转炉冶炼的优质造渣原料,但KR脱硫渣中含有质量分数为1.0%~2.5%的硫,直接将其代替活性石灰用作转炉造渣料回用于冶炼工艺会导致钢液增硫。因此,为了实现KR脱硫渣的氧化脱硫,分析渣中硫氧化行为随炉渣中硫含量变化的机理,通过实验室制取KR脱硫渣样品,采用SEM和XRD分析了氧化后炉渣的微观结构、矿物成分,采用红外碳硫分析仪测定了氧化渣样的硫含量。研究表明,在1693 K,随硫含量增加炉渣脱硫率先增加后减小,炉渣脱硫率均达到80%以上;随硫含量增加氧化渣样中析出的硅酸盐固相质点数逐渐增加。

顶吹浸没熔炼炉中气-渣-铜锍多相流搅拌特性的数值模拟

采用VOF方法对顶吹浸没熔池中氮气-渣-铜锍的流体动力学特性和搅拌特性进行数值研究。阐明气泡行为和流体速度之间的关系;研究气体入射速度和旋流对流体涡流结构、气体穿透深度和流体速度的影响。结果表明,气泡的形成和上升分别增加和降低流体速度。由于低温气体的注入,流体温度在高度0.43 m和0.52 m处分别呈现V形和W形分布。相比于58 m/s的气体注入速度,气速为98 m/s时气相的时均和最大穿透深度分别增加78.4%和31.9%。由于轴向速度分量的减小,旋流降低气体穿透深度、增加相间动量传递效率、抑制渣相喷溅。

重金属在煤气化过程中迁移规律及在气化渣中浸出行为和固化处理综述

随着我国煤气化行业不断发展,产生的煤气化渣总量也越来越多,已成为急需解决的问题之一。为充分利用气化灰渣,拓宽其应用场景,体现潜在的资源价值,已在建材、陶瓷、玻璃、分子筛、催化剂等行业进行了大量探索,并得到成功运用。然而,煤气化过程中,煤中有害重金属元素(Hg、Cr、Cd、Pb、Zn、Ni)会残留在气化灰渣中,其可能随扬尘、降水等释放或浸出到环境中,对生态环境和人类生命健康造成不利影响,制约煤气化渣综合利用。在气化过程中,煤中重金属的迁移受气化温度、气氛和压力等条件影响,不同种类重金属受这些条件的作用方式和影响程度也不同。对于煤气化渣中重金属,其浸出率受浸出液pH、浸出温度、固液比、颗粒尺寸和浸出时间等因素影响,其中浸出液pH是主要影响因素。为稳定灰渣中重金属,降低重金属释放和浸出,减少环境污染,总结梳理了煤气化渣中重金属的固化处理技术,并根据固化方式分为水泥固化、热处理固化、水热处理固化、添加剂固化、化学共沉淀固化和矿化协同固化等6种方式。

铬铁矿对高炉渣制备微晶铸石晶化行为及理化性能的影响

以包钢高炉渣为主要原料,配加少量铬铁矿,在高温渣液降温过程中采用一步保温热处理方法制备微晶铸石,通过熔点测定、差热分析、X射线衍射,扫描电子显微镜观察并结合理化性能测试,研究了铬铁矿加入量对微晶铸石晶化行为和理化性能的影响规律,为包钢高炉渣的低成本高值化利用开辟了新途径。结果表明:在原料配比为高炉渣95%、铬铁矿5%(质量分数)时,微晶铸石整体析晶,主晶相为镁黄长石和铝黄长石,抗折强度为31.88 MPa,密度为3.439 g·cm^(-3),吸水率为0.036%,耐酸性为0.145%,耐碱性为0.033%,符合国家建筑材料标准,完全可以替代天然大理石和花岗岩用作建筑装饰材料。