氧化钙颗粒在CaO-FeO-SiO_2-P_2O_5体系炉渣中的溶解行为

在1400℃下,将平均尺寸约70mm的石灰加入硅酸二钙饱和的CaO-FeO-SiO_2-P2O_5体系的炉渣中,研究了石灰颗粒在炉渣中的溶解行为.结果表明,石灰加入炉渣中沿CaO周围形成了6个区域:未熔氧化钙区域、石灰溶解向铁酸钙层转化的过渡层、铁酸钙层、不连续的固溶体层、致密的固溶体层、基体渣层;石灰加入5 s内即可形成C_2S-C_3P固溶体层,其中P_2O_5含量约在120 s时达到最大,之后随时间增加,固溶体颗粒尺寸不断增加,固溶体中P_2O_5含量降低;炉渣中含P_2O_5时,在石灰界面形成的壳层为xC_2S-C_3P而不是C_2S,C_2S-C_3P固溶体层形成阻碍了石灰溶解.     

石灰颗粒度对含石灰熔剂熔融过程的影响

应用红外真空炉研究了CaO颗粒度对含石灰熔剂熔融过程的影响。采用了两种平均粒径分别为10μm和75μm的CaO颗粒和四种含石灰熔剂：炼铁渣CaO-SiO2、CaO-FeO、CaO—SiO2-Al2O3及炼钢渣CaO—SiO2-FeO. 在现有实验条件下得出了CaO—SiO2、CaO—FeO两种熔剂的反应产物与加热温度及保温时间的关系。对于熔剂的熔融,减小石灰粒径可以缩短保温时间,但是不能降低加热温度。CaO—SiO2熔融过程中,观测到在CaO颗粒表面形成了一层2CaO·SiO2,阻碍其熔融。减小CaO粒径同时能有效的促进其在CaO—SiO2-Al2O3炼铁渣及CaO—SiO2-FeO炼钢渣中的分解。     

高铬砖与煤渣侵蚀反应的初探

使用扫描电镜和能谱仪研究了高铬砖(Cr2O3-Al2O3-ZrO2)的侵蚀反应,结果呈现出两种形式:一是形成含有部分脱锆层、再生单斜氧化锆层、再生单斜氧化锆和锆英石共存层、锆英石层;二是形成部分脱锆层和含有单斜氧化锆的渗透层。两种类型的侵蚀反应是由煤渣成分不同引起渗透层中m(CaO)/m(SiO2)比值的差异造成的:当渗透层中m(CaO)/m(SiO2)0.22时,首先在高铬砖内部由渣中SiO2与m-ZrO2形成锆英石层,再随着渗透层中m(CaO)/m(SiO2)比值的增加,形成再生单斜氧化锆和锆英石共存层、再生单斜氧化锆层和部分脱锆层;当渗透层中m(CaO)/m(SiO2)0.27时,易形成部分脱锆层和含有单斜氧化锆的渗透层。     

电磁场作用下高铁渣对MgO-C耐火材料的侵蚀

电磁场会促使熔渣中的铁、锰离子与MgO-C耐火材料反应形成锰掺杂镁铁尖晶石相,为进一步研究锰掺杂镁铁尖晶石的生成形貌及特征,采用Fe2O3质量分数为53.62%、CaO与SiO2质量比为0.8的高铁渣,分别在有、无电磁场环境下,对碳质量分数为14%的MgO-C耐火材料进行渣蚀试验。结果表明:感应炉存在电磁场,使熔渣中部分Fe2+/Fe3+与镁砂中Mg2+发生置换形成镁铁尖晶石,其含有少量Mn2+离子;镁铁尖晶石中铁含量从渣蚀层到渗透层急剧降低,锰含量几乎维持不变;侵蚀后试样渗透层较明显。电阻炉无电磁场,则侵蚀后试样没有形成镁铁尖晶石,熔渣中Si、Ca渗透到方镁石晶格中,形成钙镁榄橄石低熔相,将镁砂溶解到熔渣中;渣蚀层有明显的MgAl2O4生成。     

LF炉精炼渣对烧成镁钙砖的侵蚀机制研究

采用静态坩埚法研究了LF炉精炼渣对w(CaO)≈34%的烧成镁钙砖的侵蚀作用,并借助扫描电镜、能谱分析和X射线衍射分析了其对镁钙砖的侵蚀机制。研究结果表明:镁钙砖对LF炉精炼渣具有很强的抗侵蚀性能,但几乎不耐渗透;反应层中(Mg.Fe)O富氏体的氧化产生体积膨胀,从而造成镁钙砖开裂;渣中2CaO.Fe2O3(C2F)向砖内的渗透导致其内部液相增加,蚀损加速;2CaO.SiO2(C2S)能在反应界面形成保护层,能在一定程度上阻碍C2F向砖内的渗透。     

宝钢150t直流电弧炉炉底侵蚀的研究

对使用 82 0次后的直流电弧炉底电极套砖和炉底捣打料进行了显微结构分析。结果发现 :渣中的FeOn 固溶到套砖的方镁石晶体里形成(Mg ,Fe)O固溶体。渣中的CaO和SiO2 粘附于中、上套砖内壁 ,并向套砖内部扩散 ,然后与套砖中的MgO、Al2 O3反应形成连续液相 ,导致了套砖的损耗加快。下部套砖 1 50 0℃烧后残余膨胀大 ,显气孔率高 ,使金属铁易于渗入到整个下套砖里。对于炉底工作层 ,除了材料里MgO固溶吸收渣中FeOn外 ,Al2 O3、SiO2 和CaO等成分形成了工作层的液相。     

Cr_2O_3-Al_2O_3砖中不同组成Cr_2O_3-Al_2O_3电熔颗粒料的抗侵蚀研究

首先以不同比例的铬绿和氧化铝粉电熔制得Cr2O3质量分数分别为15%、40%、50%、60%、85%、99%的6种Cr2O3-Al2O3电熔颗粒料(其编号依次为CR15、CR40、CR50、CR60、CR85和CR99),然后采用回转渣蚀法研究了此电熔颗粒料(4~1 mm)的抗侵蚀性。结果显示:电熔颗粒料的抗侵蚀性随Cr2O3含量的增加及颗粒尺寸的增大而增强;高Cr2O3含量的CR99、CR85颗粒料在渣面层被侵蚀,主要是渣中的FeO和Al2O3对颗粒料的侵蚀,FeO与骨料中的Cr2O3反应,首先形成(Fe,Cr)3O4尖晶石,再与其他物相反应形成了复合尖晶石,当FeO耗尽后,渗入到颗粒内的Al2O3开始和Cr2O3反应,在颗粒表面形成铝铬固溶体;CR60颗粒料在渣面层和渗透层都存在侵蚀,渗透层的侵蚀主要是CaO、SiO2对颗粒料中铝铬固溶体中Al2O3的熔蚀,形成钙长石、钙黄长石以及玻璃相;Cr2O3含量较低的CR50、CR40、CR15颗粒料在渗透层内的侵蚀机制和CR60颗粒料的相同。     

转炉渣中含磷固溶体相的形成行为研究

本工作在1400℃下,将平均尺寸约450μm的硅酸二钙颗粒加入到CaO-FeO-SiO₂-P₂O₅体系转炉渣,研究了硅酸二钙的溶解及含磷固溶体相的形成行为。结果表明,硅酸二钙颗粒在FeO-SiO₂-P₂O₅体系转炉渣中溶解时,沿硅酸二钙颗粒周围形成3个区域：未熔硅酸二钙区域(边缘区域渗透高FeO含量的液态渣)、液相和固相(2CaO·SiO₂固相和2CaO·SiO₂-3CaO·P₂O₅固溶体)共存区域以及基体渣层;转炉渣中含磷固溶体相的形成方式为析出机制和扩散机制共存,通过析出机制形成的固溶体中的磷含量较高、其他元素含量较低;通过扩散机制形成的固溶体中的磷含量相对较低、其他元素含量相对较高。     

CaO-SiO2-FeO-B2O3-MnO脱磷渣熔化温度和粘度特性

采用FactSage模拟软件和修正后的Einstein?Roscoe公式计算了无氟型CaO?SiO2?FeO?B2O3?MnO预熔脱磷渣的熔化温度和粘度,考察了碱度和各成分配比对脱磷渣熔化温度和粘度的影响,得到合理的脱磷渣成分配比及控制区间和适宜的熔池温度,采用正交法进行了实验验证,通过直观分析、方差分析和主效应分析优选出最佳配比. 结果表明,该渣系粘度随碱度、FeO含量和助熔剂含量提高而降低,1400℃时最佳配比为碱度R?4.0, B2O3含量9wt%, MnO含量10wt%, FeO含量45wt%. 计算的熔化温度为1195.51℃,粘度为0.207 Pa×s,实验所测熔化温度为1192.21℃,粘度为0.199 Pa×s,计算值与实测值相近,表明正交法优选方案可靠.     

攀钢铁水罐用后高铝残砖分析

利用化学分析、X射线衍射仪、电子探针以及热力学等方法对攀钢铁水罐用后高铝残砖进行了分析.结果表明:残砖几乎没有挂渣层.舍钒钛渣由于表面张力小,黏度低,在高铝砖中的渗透很深;渣中的V2O5、TiO2、MnO、FeO等与高铝砖中组分反应生成的固溶体和化合物(如尖晶石、刚玉、钙长石等)中均发现固溶有V2O5;变质层的形成导致了致密化热震剥落;而较高的气孔率也是高铝砖损毁严重的另一重要原因.     

Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO₂–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.     

基于响应曲面法的铁水预熔脱磷渣组成优化

铁水预脱磷的处理普遍采用石灰渣系,主要由CaO, FemOn和CaF2等组成,含CaF2高,炉衬侵蚀严重,且生成的含氟脱磷产物对环境危害大,不利于脱磷渣的综合利用。针对以上问题对脱磷渣系进行优化设计,采用FactSage软件考察单因素(FeO, Na2CO3和MnO含量、碱度和脱磷温度)对铁水脱磷效果的影响,采用响应曲面法(RSM)确定主要影响因素和水平,对铁水预熔脱磷渣配比进行优化。结合模拟结果,在CaO?SiO2?FeO渣系中添加助熔剂(Na2CO3与MnO)进行脱磷预处理实验。建立预测铁水脱磷率的多元回归模型,通过方差分析和响应曲面分析对各因素的交互作用进行优选,得到脱磷渣(CaO?SiO2?FeO?Na2CO3?MnO)的最佳配比。结果表明,脱磷率随碱度、FeO含量和助熔剂含量提高而增大,脱磷剂的最佳配比为37.79% FeO,6.24% Na2CO3,9.89% MnO,碱度4.50,温度1387℃。将预测结果用于实验,最终脱磷率为97.30%,相对误差为2.70%。响应曲面法可较好地预测和指导实验,按优化成分进行脱磷实验可获得较高的铁水脱磷率,此方法能为铁水脱磷提供理论指导。     

Interfacial reaction between magnesia refractory and “FeO”-rich slag: Formation of magnesiowüstite layer

This study investigated the reaction between CaO-SiO₂-Al₂O₃-xFeO-MgO-MnO (CaO/SiO₂?=?1.2, x?=?20–50?wt%) slag and magnesia refractory. Using SEM-EDS analysis, we confirmed the formation of a (Mg,Fe)O_{ss(solid_solution)}, called magesiowüstite (MW), intermediate layer at the slag-refractory interface. MgO dissolved from refractory and reacted with the bulk slag to form MW layer at the interface. Simultaneously, slag penetrated through micro-pores and reacted with the refractory to form MW layer. In other words, the MW layer built up in both directions from initial refractory-slag interface. The thickness of the MW layer increased as the FeO content in the slag increased, and using EDS line scanning, a Mg and Fe concentration gradient was confirmed within the MW layer. The slag, which penetrated into the refractory, had a chemical composition of the CaO-SiO₂-Al₂O₃-MgO system without FeO, indicating that FeO was consumed by forming a MW layer at the refractory hot face. The slag-refractory interfacial reaction was simulated using thermochemical software, FactSage?7.0. The results predicted a MW monoxide composed of MgO and FeO. A spinel phase was formed when FeO was greater than 40?wt%. These thermochemical computations were comparable to our experimental findings.     

PbO-FeOx-CaO-SiO2-ZnO挥发性高铅渣的挥发动力学

为揭示高铅渣的高温挥发行为,以PbO?FeOx?CaO?SiO2?ZnO为基本渣系,借助热重分析技术,建立了质量比FeO/SiO2=1.8和CaO/SiO2=0.6、不同PbO含量的高铅渣高温挥发本征动力学模型,探讨了不同PbO含量下随温度变化熔渣的挥发特性,结合挥发后熔渣物相和元素分析,揭示了高铅渣的挥发规律. 结果表明,温度高于700℃时,高铅渣中PbO挥发最剧烈,造成渣成分波动导致测定结果偏差;含铅量为20wt%、温度700?1450℃的平均挥发率为18.58%;高铅渣高温挥发受三维扩散控制,影响因素为PbO和硅氧复合离子的含量.     

LF精炼废渣水热浸出过程中主要矿相的溶解行为

通过水热浸出实验分别研究了精炼废渣及合成的废渣中2种主要单一矿相12CaO?7Al2O3和2CaO?SiO2的溶解行为,并将二者进行对比分析,探究了LF精炼废渣在水热浸出过程中的溶解行为。结果表明,废渣浸出过程中浸出液的pH?12,且随浸出时间增加,电导率和Ca浓度增加,Al浓度急剧下降,Si浓度低于0.1 mg/L且保持不变;12CaO?7Al2O3浸出过程中,随时间增加,浸出液pH值稳定在约11.3,浸出液中Al浓度增加,Ca浓度略微下降。2CaO?SiO2浸出液中主要为Ca2+,Si浓度低于0.6 mg/L;废渣与单一矿相浸出过程的pH值及Al, Si浓度较接近,可以通过单一矿相的溶解行为研究精炼废渣在水热浸出过程中的溶解行为,但废渣浸出液的Al和Si浓度均低于单一矿相,表明废渣中CaO等其它组分溶解抑制了12CaO?7Al2O3和2CaO?SiO2溶解。     

Phase evolution and nature of oxide dissolution in metallurgical slags

The dissolution of solid lime particles into liquid slags at high temperatures was evaluated by means of confocal scanning laser microscopy. An additional solid layer around the lime particle was observed at the intermediate stage of the dissolution into CaO? Al₂O₃? SiO₂ slags. The dissolution rate was decelerated due to the existence of the additional layer and the dissolution profile could be clearly distinguished into three stages, that is, an early, intermediate, and late stage. By adding 10 wt % MgO, this layer could be effectively eliminated and the slope of the whole dissolution profile kept relatively constant. The dissolution path and mechanisms were subsequently evaluated by incorporating thermodynamic calculations. Both direct and indirect dissolutions could be distinguished. It was realized that the decrease in composition range for solid precipitating after adding MgO could significantly reduce the interfacial reaction (IR) layer formation. Post‐mortem analyses on quenched samples were further carried out to confirm the theoretical calculations. It was found that the solid layer in slags without MgO was (CaO)₂·SiO₂ and (CaO)₃·SiO₂ which is in line with the thermodynamic calculations. However, only (CaO)₂·SiO₂ was noticed in slags with MgO which both (CaO)₂·SiO₂ and MgO phases should be present according to the calculations. The nonequilibrium during dissolution may play an important role on phase transformation and MgO particles in much smaller quantity may have dissolved into (CaO)₂·SiO₂ phase. The diffusion of CaO in both slags with and without MgO was additionally investigated. The local CaO concentration distributions from the direct dissolution phase to the slag bulk could be well fitted with the theoretical model proposed via Fick's second law. As a result, the local diffusion coefficient in the dissolution region was obtained and the effect of MgO addition on diffusion could be assessed. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2907–2916, 2013     

从含碱硅酸钠溶液中水热合成硅灰石

以含碱硅酸钠溶液为原料,在常压下加入石灰乳,先水热合成CaO·SiO2·H2O,再将CaO·SiO2·H2O在850℃下焙烧2 h可制备硅灰石.研究了溶液中SiO2浓度、钙硅摩尔比(C/S)及反应时间对硅灰石合成的影响.热力学计算结果表明,常压下Na2O-CaO-SiO2-H2O体系中,最有可能形成CaO·SiO2·H2O及2CaO·SiO2·1.17H2O.实验结果表明:当C/S为1.0时,随着溶液中硅浓度的增加,硅酸根离子的聚合程度增加,有利于硅灰石的制备;随着时间的延长,硅灰石结晶程度越高;当C/S为0.6、0.8、1.0时,最终产物为CaSiO3;当C/S为1.5、2.0时,最终产物中含有大量的Ca2SiO4.适宜的水热合成条件为:SiO2浓度>30 g/L、C/S 0.6～1.0、温度98℃、反应时间>3 h.     

烧结工艺参数对铝酸钙炉渣体系物化性能的影响

在铝酸钙炉渣最佳物料配比条件下,应用XRD和激光粒度分析等手段研究了温度和保温时间对铝酸钙炉渣体系物相组成、粒度和氧化铝浸出性能的影响. 结果表明,当温度低于1450℃时,炉渣处于固相反应区,反应速度缓慢,并含有相当一部分的难浸物质2CaO×Al2O3×SiO2,降低了炉渣的自粉率和浸出性能. 当温度在1450℃以上时,炉渣中出现液相,反应速度加快且进行比较完全;炉渣主要物相为12CaO×7Al2O3和g-2CaO×SiO2,自粉和浸出性能良好. 保温时间对炉渣物相和粒度影响不大,但略微降低了氧化铝浸出率.     

Surface Structure of Converter Slag Stabilized by Heating

Converter slag contains free lime (CaO) and unstable iron oxides (FeO, FeOOH) that may lead to expansive self-destruction. A typical industry practice for converter slag has been stabilization by steam curing and autoclaving; however, the stabilization can only reach the surface, and not the inside, of slag particles. A new method is proposed in this study to stabilize the converter slag by heating at a low temperature. After magnetic separation, specimens of converter slag were subjected to heating for 2 h at a temperature of 500°C, resulting in a decrease of free lime content irrespective of the particle size. This effect was attributed to the formation of Ca₂Fe₉O₁₃ and complicated apatite groups owing to the heating. The iron oxides in the converter slag were analyzed by X-ray photoelectron spectra. It was found that after heating, the unstable FeO (wustite) content decreased and an oxidized α-Fe₂O₃ (hematite) increased. This led to the prevention of the iron-induced expansion. The rate of heat liberation by the free lime in converter slag was smaller than that of the reagent CaO. This suggests that the presumed free lime is in a different form based on the Ca bond energy in the surface of slag particles.