Experimental Study Refining on Composition Slag Containing Optimization for BaO

Laboratory study; was carried out on deep desulfurization of molten steel by CaO-Al2O3 based refining slag containing BaO at 1873K to achieve lower sulphur level in steel. A mathematical model of desulfurization was established with the methodology of quadratic orthogohal regression. According to the modle, the influence of AlO3/CaO, MgO, CaF2, BaO in slag on desulfurization rate was analyzed. The results showed that the desulfurization rate almost linearly decreased with the increase of Al2O3/CaO and it increased firstly then decreased when MgO and BaO content increased respectixely, yet the trend is on the contrary as CaF2 content increased. Based on the comprehensive analysis, the optimum composition of the refining slag was achieved under the experimental conditions.     

低氟CaF2-CaO-Al2O3-MgO-SiO2系精炼渣的性能

设计了精炼铜-铬合金用低氟CaF2-CaO-Al2O3-MgO-SiO2五元渣系,并研究了其粘度、密度、表面张力及熔化温度等性能. 结果表明,该渣系的熔化温度在1336~1402℃之间;高温下该渣系的密度和表面张力均随温度升高而减小,且随CaF2含量和MgO含量增加逐渐降低;增加CaF2添加量可降低渣系粘度;CaF2含量较低时,MgO含量增加也可降低渣系粘度,CaF2含量较高时,渣粘度在MgO含量为6%时最小,MgO含量续增加到9%时粘度反而上升. 该渣系粘度较低,表面张力较小,具有良好的精炼效果.     

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。     

RH精炼渣高熔点相作用浓度对粘渣的影响

为抑制RH精炼过程中熔渣中高熔点镁铝尖晶石和铁铝尖晶石相的析出以减轻浸渍管粘渣,基于分子离子共存理论,建立了CaO-SiO2-MgO-Al2O3-FeO-CaF2-MnO七元精炼渣系结构单元作用浓度的计算模型,计算了高熔点相的作用浓度,分析了熔渣组成对高熔点相作用浓度的影响. 结果表明,当RH精炼渣的碱度(CaO/SiO2, w)在4.0~5.0, CaO/Al2O3(w) 为1.5~2.0, MgO含量约10%(w), FeO含量约17%(w), CaF2含量不高于7.5%(w)时,精炼渣中MgO×Al2O3和FeO×Al2O3的作用浓度处于较低水平,不足以结晶析出,因而可以减轻RH浸渍管的粘渣. 模型计算结果与实验结果一致,为减轻粘渣用改质剂配方的设计提供了理论依据.     

电渣重熔过程增镁及其对夹杂物的影响

通过设计含镁渣系，并在电渣重熔过程添加脱氧剂，氩气保护气氛下进行电渣重熔实验，研究了电渣重熔过程增镁的可能性。用电感耦合等离子体原子发射光谱分析了钢中的镁含量，用ASPEX扫描电镜分析了电渣锭中镁含量对夹杂物尺寸、类型、形貌等的影响。结果表明，渣中含20wt% MgO以上时，即使自耗电极中不含镁，也能使渣中MgO向钢液中传递镁。实验室条件下，分别用55wt% CaF2–15wt% Al2O3–10wt% CaO–20wt% MgO, 65wt% CaF2–10wt% Al2O3–25wt% MgO, 51wt% CaF2–8wt% Al2O3–8wt% CaO–23wt% MgO–10wt% MgF2渣系重熔时，电渣锭中镁含量分别为0.0034wt%, 0.0039wt%, 0.0043wt%。随电渣锭中镁含量增加，夹杂物组成逐渐从以Al–Ca, Al–Mn–S, Al–Mg–Mn–S为主，转变为以含镁夹杂物为主，镁含量最高达98wt%；夹杂物数量大幅减少，直径明显减小，最大直径均小于10 μm，大多数小于5 μm。与含镁0.0003wt%的电渣锭相比，镁含量增至0.0034wt%时，夹杂物从357个降至31个，最大夹杂物直径由11.0 μm降至8.5 μm，平均直径由3.7 μm降至3.2 μm。     

改质剂对LATS精炼钢包渣粘度的影响

为减少LATS合金化精炼钢包浸渍罩粘渣,研究了LATS精炼前后钢包渣粘度的变化,并分别用CaO+CaF2, CaO+B2O3及Li2O作为钢包渣的改质剂来降低渣粘度. 采用旋转柱体法的粘度测试结果表明,LATS合金化精炼钢包渣的粘度高及LATS处理后渣的粘度进一步升高是造成浸渍罩粘渣的主要原因之一. 实验所用3种改质剂均能有效降低钢包渣的粘度. 在1500℃无改质剂时LATS处理后钢包渣粘度为6 Pa×s,当加入10% CaO+CaF2后渣粘度低于3 Pa×s,而加入10% CaO+B2O3或加入4% Li2O都可使渣粘度低于2 Pa×s.     

超低碳铝硅镇静钢精炼过程中夹杂物的行为及其对钢组织的影响

针对RH精炼并结合典型的渣-钢化学平衡实验,研究了超低碳铝硅镇静钢精炼过程中夹杂物的变化以及钢包顶渣组成对钢中夹杂物的影响. 用激光共聚焦高温扫描显微镜在线观察了再加热过程中钢的微观组织变化,讨论了夹杂物对钢的晶粒长大的影响. 结果表明,本实验条件下精炼前钢中夹杂物是以Fe-Mn氧化物为主的复合夹杂,夹杂物数量和大小受渣碱度、Al2O3含量及CaO/Al2O3比值的影响较大,当碱度为1.5及Al2O3含量为20%时,夹杂物数量最少. 以成分优化的钢包渣与精炼末期钢样进行的平衡实验显示,夹杂物为Al2O3-MgO或Al2O3-MgO-SiO2-MnO为主的复合夹杂,随渣中w(MnO)的增加,复合夹杂中Mn含量有增加的趋势,使钢的晶粒长大过程需要更高的再加热温度. 钢样再加热后,钢中夹杂物变为以Al2O3, MgO, SiO2复合夹杂为主,三者总量占夹杂物总量的90%或以上,复合夹杂中MnO含量受加热制度影响.     

铬矿在CaO-SiO2-MgO-Al2O3渣系中的熔解行为

研究了形状一定的致密铬矿在CaO-SiO2-MgO-Al2O3渣系中的熔解行为,系统考察了不同渣系组成对铬矿在渣中熔解量及熔解速度的影响,结合实验现象讨论了铬矿在渣中的熔解机理. 研究结果表明,在本实验条件下,炉渣碱度在0.8~1.5范围内,随渣碱度降低,铬矿熔解量及熔解速度均增大;铬矿熔解量和熔解速度随着Al2O3和MgO质量分数,尤其是Al2O3质量分数增大而减小,在炉渣中添加CaF2可明显加快铬矿熔解速度.     

Na2O-TiO2-SiO2-CaO-Al2O3-V2O5-MnO-MgO-FeO渣系渣铁间硫分配比热力学模型

基于离子分子共存理论(IMCT)建立了Na₂O-TiO₂-SiO₂-CaO-Al₂O₃-V₂O₅-MnO-MgO-FeO九元渣系的结构单元作用浓度模型和渣铁间硫分配比热力学模型,并对模型进行实验验证。通过模型计算出1200℃下渣系主要结构单元组成和渣中Na₂O,CaO,MnO,MgO和FeO的活度,发现Na₂O的加入可促进渣中低熔点物质的生成,降低渣系熔化性温度,改善脱硫反应的动力学条件;同时随着Na₂O加入量的增加,渣中Na₂O和CaO的活度增加,进而降低渣中S^2?离子活度,强化渣铁间脱硫反应。实验结果表明,增加碱矿比提高了渣铁间硫分配比,有利于铁水深度脱硫,铁水中硫含量可降至0.0005wt%以下,硫分配比的理论计算值与实验结果吻合极好。渣中各碱性氧化物的硫分配比随碱矿比R_N/C增加逐渐增大,各碱性氧...     

Effect of substituting CaO with BaO on the viscosity and structure of CaO‐BaO‐SiO2‐MgO‐Al2O3 slags

In this study, the effect of CaO and BaO substitution on the viscosity and structure of CaO‐BaO‐SiO₂‐MgO‐Al₂O₃ slags was investigated. The results showed that the viscosity increased with an increase in the BaO substitution concentration, which was correlated to an increase in the degree of polymerization (DOP) of the slag structural units as the activation energy increased from 207.9 to 263.8 kJ/mol for viscous flow. Deconvolution and area integration of the Raman spectrum of the slag revealed that the ratio of Q³/Q² (Qⁱ, i is the number of O⁰ in a [SiO₄]‐tetrahedral unit) increased and NBO/Si (nonbridging oxygen per unit silicon atom) decreased with higher BaO content. It was also observed from the ²⁷Al magic angles pinning nuclear magnetic resonance (²⁷Al MAS‐NMR) spectrum that the relative proportion of Al^IV increased, while that of Al^V decreased because of the decrease in the percentage of nonbridging oxygen (O^?), indicating the polymerization of the slag. O_1s X‐ray photoelectron spectroscopy (XPS) was also carried out to semi‐quantitatively analyze the various types of oxygen anions present in the slag. The XPS results correlated well with the results obtained from the analysis of the Raman and ²⁷Al MAS‐NMR spectra of the slags and its viscous behavior.     

钢渣改性用于烟气脱硫研究进展

钢渣结构上疏松多孔、组分上富含氧化钙、氧化镁等碱性氧化物,因此其在溶液中碱性较高,酸中和能力强,能有效去除烟气中二氧化硫实现有效脱硫。目前钢渣主要用于湿法脱硫工艺,基本机理是气液两相间的传质过程,包括二氧化硫由气相进入液相、液相中钢渣碱性物质溶解析出、进入液相的二氧化硫与钢渣中碱性物质发生化学反应3个过程,但脱硫效果主要受前两个过程影响,主要影响因素包括入口二氧化硫质量浓度、液气比、浆液pH、反应温度、钢渣粒径等。但目前对钢渣中除氧化钙、氧化镁外其他组分对脱硫效果的影响机理研究还不够深入。因此,下一步要积极探索钢渣中不同化学组分在烟气脱硫过程中的协同作用和机理,完善钢渣用于烟气脱硫的理论基础,进而实现钢渣脱硫的工业化应用。     

中间包涂料对钢液洁净度的影响

实验研究了镁质、氧化铝质和镁钙质三种中间包内衬涂料与钢水反应,考察了其对钢中T.O, T.N及Al, Ti, Si, Mn含量、夹杂物组成、数量和尺寸分布的影响,并分析了钢水在钢/涂层界面对涂层的渗透和侵蚀程度. 结果表明,在1550℃下,相比于镁质涂料和氧化铝涂料,镁钙质涂料能对钢液T.O和成分有更好的控制,终点氧含量在8.5′10-5,对钢液的二次氧化很少,并有利于细小夹杂物的形成,其中<1 mm夹杂物占98.13%;钢中首先是Al, Ti被氧化,之后是Si, Mn被氧化;氧化铝涂料被损坏的机理主要是冲刷脱落,镁质和镁钙质涂料的损坏则以渗透侵蚀为主. 镁钙质涂料对钢液的二次污染小,有利于洁净钢的生产.     

炉渣组分对CaO-Al2O3-SiO2-TiO2-MgO-Na2O渣系粘度的影响

针对高碱度高氧化铝含氧化钠的CaO-Al2O3-SiO2-TiO2-MgO-Na2O六元渣系,采用有限制的混料均匀设计方法设计实验,在1773 K温度熔融还原条件下测定了该渣系的粘度. 利用偏最小二乘法回归分析,建立了炉渣组分与粘度的回归方程,利用回归方程分析了炉渣碱度[w(CaO)/w(SiO2)], MgO, TiO2, Al2O3及Na2O对炉渣粘度的影响. 结果表明,回归方程拟合的关联系数RC2为0.9945,方程可很好地预测该渣系的粘度. 在实验范围内,炉渣粘度随碱度的增加而增加. 碱度一定时,炉渣粘度随MgO, Al2O3, Na2O含量的增加而逐渐降低,随着TiO2的增加先降低后增加. 当炉渣碱度小于3.1、MgO质量含量大于4%、Al2O3大于20%、TiO2在3.1%~6.1%、Na2O大于0.75%时,1773 K温度下炉渣粘度均小于2 Pa×s,此时渣系粘度完全满足实际冶炼要求.     

复合熔析精炼去除工业硅中的非金属杂质硼

在1550℃下将CaO-SiO2-Al2O3三元渣与Sn-Si合金混合精炼,降温熔析去除工业硅中的杂质B,考察了渣系光学碱度及合金组成对B去除的影响及作用机理. 结果表明,渣系光学碱度增大,BO1.5的活度系数降低明显,增加了B的分配系数,即增强了精炼效果. Sn-Si合金中Sn比例从0增至70%时,B在渣相与合金相间的分配系数从3.16提高至13.8,硅中B含量最低为0.89′10-6,最高除硼率为93.3%;当Sn比例大于30%时,合金粘度大幅降低,B的分配系数提高;当Sn比例为70%、合金粘度为0.61 mPa×s时,渣系CaO-SiO2-20%Al2O3与CaO-SiO2-40%Al2O3精炼工业硅所得最大B分配系数分别为10.1和12.3.     

添加剂对中钛炉渣性能的影响

以河北钢铁集团承德钢铁集团有限公司现场高炉渣为基准,用化学纯试剂配制渣样,考察了添加剂对中钛炉渣粘度、熔化性温度的影响. 结果表明,炉渣碱度为1.12, CaF2含量为0.5%~2%, Fe2O3含量约为5%, Al2O3含量约为13.75%, MgO含量约为13.95%, MnO含量约为5%(w)时,有利于降低炉渣粘度和熔化性温度;添加Ce2O3使炉渣熔化性温度和粘度升高,不利于生产.     

不锈钢渣理化性质分析与应用研究

借助于XRD、SEM和DSC/TG等测试分析手段进行不锈钢渣理化性质分析与表征.结果表明:不锈钢渣化学成分主要是SiO2和CaO,其次是MgO、Al2O3及Fe2O3;矿物组成包括硅酸三钙(Ca3SiO5)、硅酸二钙(Ca2SiO4)、硅钙石(Ca3Si2O7)、硅酸钙(CaSiO3)及RO相;微观结构由许多尺寸大小不等的颗粒组成,孔隙大、结构疏松;内外照射指数IRa和Iγ均小于1.0,符合GB 6566-2010标准;当不锈钢渣质量百分比掺量为30%时,28 d抗压强度基本达到P· C32.5复合硅酸盐水泥标准,且7 d活性指数显著高于28 d活性指数.并依据研究结果分析不锈钢渣在水泥、混凝土及建筑材料领域资源化利用的可行性.     

Corrosion modeling of magnesia aggregates in contact with CaO–MgO–SiO2 slags

Ladle refining is an efficient process for improvement of quality of steel on secondary metallurgy under harsh conditions. Magnesia refractories with high purity are important raw materials for ladle lining in high-quality steel production. However, the penetration by CaO–MgO–SiO₂ slags damages magnesia refractories, which considerably limits their service life. Abundant grain boundaries in magnesia create channels for slag penetration and lead to the destruction of the structure. The effect of the microstructure on the slag corrosion behavior of magnesia aggregates requires further systematic investigation. In this study, a corrosion model was established to describe the slag penetration process of magnesia aggregates. The effects of the grain-boundary size and slag CaO/SiO₂ mass ratio (C/S ratio) on slag penetration were investigated, and the possibility of the microstructure optimization of magnesia aggregates was discussed. The results indicated that magnesia aggregates exhibited excellent slag resistance for slag with a C/S ratio above 1.5 or even 2.0. When the slag C/S ratio was lower than 1.5, the dissolution rate of magnesia decreased more rapidly with the increase in the slag C/S ratio. In addition, the much smaller grain-boundary size increased the slag penetration resistance by promoting the formation of a dense isolation layer and inhibiting further penetration processes. The calculation results agreed well with the experimental results, suggesting that the corrosion model is promising for predicting slag corrosion.     

活性炭混合钢渣烧结烟气脱硫脱硝实验研究

采用混合法用钢渣与活性炭制备混合钢渣活性炭吸附剂，对其进行XRF, BET, SEM和FT-IR等表征，于可编程电加热固定床反应器中进行模拟烧结烟气脱硫脱硝实验，考察反应温度、SO2浓度及[NH3]/[NO]浓度比、O2含量等因素对混合钢渣活性炭的吸附及催化性能的影响。结果表明，模拟烧结烟气中SO2初始浓度0.06vol%, NO初始浓度0.04vol%, O2含量15vol%及反应温度120℃条件下，最高脱硫脱硝率分别为79%和34%。按浓度比[NH3]/[NO]=1通入还原剂NH3时，脱硫脱硝率均升高，表明钢渣具有一定催化还原作用。脱硝率随反应温度升高而下降，O2含量提高有利于混合钢渣活性炭对SO2和NO的吸附。掺混钢渣降低了吸附剂的比表面积，但钢渣中含一定量Fe2O3，具有一定催化还原作用，有利于NO吸附。同时，加入钢渣也是对固废资源的合理利用，达到“以废制污”的目的。     

电石水解制备复合钙基吸附剂及其循环吸附CO2的特性

利用电石水解制乙炔工艺制备新型电石渣CaO/Ca12Al14O33复合钙基吸附剂,考察了Ca12Al14O33含量、碳酸化和煅烧再生温度对CaO转化率和多循环吸附CO2的影响,并与分析纯CaCO3和传统电石渣进行了比较,对其表面形貌、比表面积和孔结构进行了分析. 结果表明,新型复合钙基吸附剂在多循环煅烧/碳酸化过程中具有较好的多循环吸附CO2的性能. Ca12Al14O33有效减缓了吸附剂烧结现象. 20次循环后,自制电石渣吸附剂的CaO转化率仍保持在48%以上.     

Enhanced performance of ultra-low carbon MgO–C bricks by the addition of special C/MgAl2O4 composite powders

Argon oxygen decarburization (AOD) refining as one type of secondary refining plays an important role in the steel industry. MgO–CaO and MgO–C bricks are widely used in AOD refining, and MgO–CaO bricks are easily hydrated. MgO–C bricks containing carbon easily pollute molten steel and have lower mechanical strength. In this study, ultra-low carbon MgO–C bricks containing C/MgAl₂O₄ composite powders used in AOD refining were explored. MgAlON as the strength phase was in situ generated in the composites (M3) containing 2 wt% C/MgAl₂O₄ composite powders. The samples were further compared with commercial MgO–CaO bricks (M1), which are currently used in the slag line of the AOD furnace, and the sample (M2) without the addition of C/MgAl₂O₄ composite powders. The hot modulus of rupture (HMOR) of M3 was the highest at 27.3 MPa, which increased 44% compared with that of M2 and increased 158% compared with that of M1. The number of thermal shock test cycles of M3 was 1.6 times that of M2. HMOR and cold crush strength (CCS) of samples after thermal shock resistance test were measured. The HMOR of M3 after 3 cycles of the thermal shock test was 2.1 times greater than that of M1. After 20 thermal shock cycles, the residual CCS ratio of M3 was highest, up to 94.6%. Improvement in the thermal shock resistance of the composites can be achieved by the addition of C/MgAl₂O₄ composite powders, which promote the generation of MgAlON. It was also found that the slag corrosion depth of M3 was the lowest at 64.7% of that of M2 and was 13% of that of M1. The internal micromorphologies researched by XRD and SEM and the corrosion mechanism revealed by thermodynamic calculations show that MgAlON was formed in situ after the corrosion test and endowed the composites with excellent properties.