Update on the Equilibrium between Liquid Fe‐Ti‐O Slags and Metallic Iron

The current work is an update on the equilibrium between a synthetic high titania slag and metallic iron at temperatures above the slag melting point. The experimental setup is essentially the same as previously shown in the literature, thus employing a cold crucible in a high frequency induction furnace. A new addition to the experimental setup is the temperature measurement by a spectropyrometer. The temperature measurements will give the liquidus temperature for the slags. This temperature shows a decreasing trend as the FeO content in the slag increases. 24 slags have been successfully produced with iron saturation with a FeO content ranging from 6 to 33 wt%. The slags show a clear trend and provide a solid foundation to the location of the slag‐metal equilibrium line in the investigated area. The experiments are in agreement with previously published experimental data but not with previously calculated results using thermodynamical software.     

首钢高炉渣与配制四组元渣的黏度研究

对首钢高炉渣样及相应配制的四组元渣的固相析出温度和黏度进行了对比研究,通过电子探针和旋转法分别检测渣样的固相析出温度和黏度。结果表明,现场高炉渣固相析出温度为1400～1440℃,相应配制的四组元渣的固相析出温度要比现场高炉渣高40～50℃。其中微量组元如S（CaS形式）,FeO,MnO和TiO2等的存在有利于降低渣固相析出温度。黏度测试表明,现场高炉渣在1500℃时的黏度范围为0.3～0.4Pa·s,相应配制的四组元渣在1500℃时的黏度比现场渣要高30%左右。通过以上对比,不仅了解了高炉渣中微量组元对高炉渣的整体影响,而且有助于将实验室研究结果应用于现场操作。     

首钢A高炉炉渣降低MgO的热力学分析

为了研究首钢A高炉炉渣降低MgO的可行性,利用FactSage热力学软件,从理论上解析首钢A高炉炉渣中MgO对固相析出温度和黏度的影响。研究发现,A高炉炉渣固相析出温度在1 400 ℃左右,炉渣在高炉炉缸中全为液相并具有较好的流动性。1 500 ℃下,现有炉渣组分在相图中液相区,若MgO含量降低,炉渣仍处在液相区。MgO质量分数在2.87%～7.37%区间变化时,随MgO含量升高,固相析出温度增加;MgO质量分数升高1%,炉渣固相析出温度升高约3.73 ℃。随MgO含量升高,炉渣黏度降低。1 500 ℃下,MgO质量分数升高1%时,炉渣黏度降低0.014 Pa·s。分析认为,炉缸热状态较好(铁水温度在1 480 ℃以上)时,适当降低MgO质量分数至6%,炉渣黏度不会受较大影响;炉缸热状态较差(铁水温度在1 480 ℃以下)时,不建议降低MgO含量。     

Study on the Possibility of Using ZnO to Increase the Desulfurization Potential of Blast Furnace Slag and Sulfide Capacities

Zinc oxide has recently been suggested to be a potential material for hot metal desulfurization. The present work was carried out to examine whether ZnO could help the remaining blast furnace (BF) slag to capture sulfur. For this purpose, slags prepared with relatively high ZnO content was equilibrated with either liquid silver or liquid copper under controlled oxygen potential at 1773 K. It was found that most of the ZnO escaped during the experiment, indicating thereby that ZnO could not increase the desulfurization potential of the BF slag in the case of hot metal. The experimental data were used to evaluate the sulfide capacities of the studied slags. In some of the slags equilibrated with silver, the MgO activities were evaluated.     

含钛高炉渣铁侵蚀炉衬的显微结构分析

对含钛高炉渣，铁显微结构的研究表明，攀钢高炉随冶炼强度的提高，炉渣组成发生变化，渣中TiC,TiN,Ti(C,N)含量减少，影响护炉效果，含钒钛的铁水中含有TiC,TiN,Ti(C,N),对护炉起着很大作用，因此钒钛矿护炉不单是含钛渣完成的，也有含钒钛铁水的作用。     

An empirical formula for accurate calculation of liquidus temperature of blast furnace slags in SiO2–Al2O3–CaO–MgO system

Precise numerical simulations of blast furnace (BF) rely on accurate and convenient thermophysical property models of BF slags. Liquidus temperature (T_liq) is one of the most fundamental properties of BF slag, however, the conventional phase equilibrium diagram method for T_liq calculation can be hardly used in numerical simulations. In this work, an accurate and simple empirical formulation suitable for T_liq calculation of BF slags in numerical simulations is established. The model was calibrated by 707 measurement representing 11 primary phase fields in SiO₂–Al₂O₃–CaO–MgO system. The calculated T_liq in present work agrees very well with the measured values, with an average error of only 17.1°C, which is much more accurate than CalPhad method. Present work also suggests that the liquidus region of BF slag at 1500°C should be slightly extended based on the classic phase equilibrium diagram.     

Manganese Distribution between FeO‐MnO‐SiO2–CaO–MgO‐Al2O3 Slags and Molten Iron

Pretreatment of high manganese hot metal is suggested to produce hot metal suitable for further processing to steel in conventional LD converter and rich manganese slags satisfy the requirements for the production of silicomanganese alloys. Manganese distribution between slag and iron represents the efficiency of manganese oxidation from hot metal. The present study has been done to investigate the effect of temperature, slag basicity and composition of oxidizer mixture on the distribution coefficient of manganese between slag and iron. Ferrous oxide activity was determined in molten synthetic slag mixtures of FeO‐MnO‐SiO₂–CaO–MgO‐Al₂O₃. The investigated slags had chemical compositions similar to either oxidizer mixture or slags expected to result from the treatment of high manganese hot metal. The technique used to measure the ferrous oxide activity in the investigated slag systems was the well established one of gas‐slag‐metal equilibration in which molten slags contained in armco iron crucibles are exposed to a flowing gas mixture with a known oxygen potential until equilibrium has been attained. After equilibration, the final chemical analysis of the slags gave compositions having a particular ferrous oxide activity corresponding to the oxygen potential of the gas mixture. The determined values of ferrous oxide activity were used to calculate the equilibrium distribution of manganese between slag and iron. Higher manganese distribution between slag and iron was found to be obtained by using oxidizer containing high active iron oxide under acidic slag and relatively low temperature of about 1350°C.     

高炉炉渣熔化温度及液相生成热力学分析

为了研究温度、二元碱度、Al2O3含量和MgO含量对高炉渣熔化温度和液相生成特性的影响,结合炼铁生产中典型的高炉渣成分,利用Factsage集成热力学数据计算系统计算并绘制出了不同组分高炉渣渣系四元相图,并根据试验计算所得结果,分别分析了温度、二元碱度、Al2O3含量和MgO含量这4种因素对高炉渣熔化温度及炉渣液相区变化的作用规律,并结合生产实际给出了高炉冶炼中适宜的炉渣碱度、炉渣中合理的MgO及Al2O3含量。     

模拟复吹转炉脱钛预处理的理论和试验

 采用具备顶底复吹功能的500 kg感应炉模拟了转炉预脱钛工艺,分析了钛的氧化反应机理。试验结果表明：终点铁水钛质量分数平均为0.008 2%,脱钛率平均为71.3%。脱钛率随铁水温度升高而降低,随熔池供氧量增加而增加。铁水的终点钛质量分数与终点硅、锰质量分数存在平衡关系,与过程中碳的氧化没有相关性。渣铁间钛分配比为0.6～1.6,随渣中氧化亚铁质量分数的提高而提高,随铁水温度的升高而降低。试验结果和低温下有利于脱钛的理论分析一致。     

Effect of titania on the characteristics of blast furnace slags

The objective of this study was to understand the effect of 1 – 2 % titania on the high-temperature properties of blast furnace slags containing high alumina and magnesium oxide. The viscosity and liquidus temperature of semi-synthetic blast furnace slags were measured using a viscometer and a hot stage microscope, respectively, and the data were used to develop a statistical model for predicting the liquidus temperature and viscosity of blast furnace slags. Samples of the titanium bearing accretions were collected during tearing-out of the hearths of Tata Steel's blown-out D and E blast furnaces. They were subjected to various physico-chemical analyses (e.g. chemical, XRD, optical microscopy, SEM and image analysis) in order to understand the mechanism of hearth protection. In the range of composition studied, the liquidus temperature is found to lie between 1365 to 1430°C and the viscosity, between 0.30 to 0.60 Pa · s. Increase in titania fluidizes the slag and also makes it easy-melting. The titanium bearing compounds in the slag show traces of TiC, TiN, Ti₂N, TiO, Ti₂O₃, Ti₃O₅ and Ti₅O₉. A mechanism of formation of these precipitates is proposed in this paper.     

Use of Banded Hematite Quartzite (BHQ) in Blast Furnace for Partial Replacement of Quartzite

Hot metal produced through blast furnace (BF) route is still the most preferred route in majority of the steel industries. In the blast furnace operation, quartzite is used as flux to adjust the desired slag chemistry and basicity (B2 of 1–1.08) to achieve optimum slag properties such as low liquidus temperature, high Sulphur carrying capacity and low viscosity. This paper describes the investigations carried out at JSW Steel Ltd to identify alternate sources of silica other than quartzite for use as flux in BF to maintain the desired slag chemistry for smooth operation and cost reduction. Banded hematite quartzite (BHQ) ore available in Karnataka region contains 28–33% Fe, 45–46% silica, 1.3–1.5% alumina and is found suitable for use as partial replacement for quartzite in blast furnaces. Mineralogy and phase analysis of BHQ reveals alternate bands of hematite and silica whereas in lump ore, hematite and silica are uniformly distributed. This phase distribution and reducibility index of BHQ (~66%) affect the softening start temperature by forming fayalite (2FeO·SiO₂) as primary slag. Fines generations are found to be comparatively higher (from 6.3 to 6.4%) but in acceptable range. The Fe content in the BHQ also contributes to the overall Fe input to the furnace favoring an option to reduce the equivalent amount of iron bearing materials in the charge. Plant trials at JSW steel blast furnace #4, indicate an improvement in overall operational performance resulting in increased Fe input per charge, reduction in slag rate by 8 kg/thm due to low alumina input and easier achievement of final slag chemistry.     

A Study of Some Elemental Distributions Between Slag and Hot Metal During Tapping of the Blast Furnace

This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10‐minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag‐metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L_Mn and L_V, but an increased L_S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO₂ was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.     

TiO2对京唐高炉渣性能的影响及热力学分析

 为明确TiO2对京唐炉渣性能的影响机理,基于京唐高炉渣的实际成分,通过黏度试验研究了TiO2对炉渣黏度及熔化性温度的影响;同时利用FactSage热力学软件,计算了不同TiO2质量分数炉渣的活度、熔化温度,液相区以及炉渣从1 500冷却到1 000 ℃时的物相变化。试验结果表明,炉渣的黏度和熔化性温度随着渣中TiO2质量分数的增加而降低。FactSage计算表明,炉渣中TiO2活度增大,炉渣的黏度随之减小;TiO2增多有利于降低炉渣的熔化温度和扩大液相区,但当[w(TiO2)]由4.2%变化到5.6%时,炉渣的液相区反而在CaO区域缩小;炉渣结晶相的变化表明渣中TiO2不宜过多,否则在高温时就容易生成钙钛矿相,从而增大炉渣的黏度,不利于高炉顺行。为满足京唐高炉冶炼对炉渣性能的要求及护炉的需要,炉渣中[w(TiO2)]应控制在5.0%以内。     

京唐1号高炉低燃料比冶炼技术

为了降低京唐高炉燃料消耗,通过对Rist操作线的意义进行阐述,以京唐1号高炉生产参数为依据,计算并绘制了Rist操作线,据此分析了煤气利用率、风温、生铁含碳、金属化率等高炉操作参数改变对燃料比的影响。针对这些影响因素,京唐1号高炉对降低燃料比进行了一系列攻关工作,通过采取强化原燃料管理,提高原燃料质量,为降低燃料消耗创造条件。优化高炉操作,降低热风炉拱顶温度,对热风管系进行改造,提高送风系统的安全性,尽可能提高风温水平;优化装料制度,获得较高的煤气利用率;高风温、富氧,稳定均匀喷吹以提高煤粉置换比。通过对生产攻关实践,首钢京唐1号高炉实现了低燃料比生产,达到490kg/t。     

Study of the Effect of Hellenic Diasporic Bauxite Addition on Blast Furnace Operations

The blast furnace (BF) operation, as well as the steel‐shop downstream, can derive benefits from adjusting the slag alumina content with the proper addition of bauxite flux to its burden. Additions of 5‐15 kg of bauxite/t hot metal lead to a raise of the alumina content of the resultant BF‐slag from 10% to the level of about 12%. In Hellas extensive deposits of diasporic bauxite exist which, however, are under‐utilized by the alumina refineries due to their rather low solubility during the Bayer‐process. The above BF application, therefore, as an alternative use of the diasporic bauxite, is of great interest to the bauxite producers of Hellas. The influence of the bauxite additions on the metal/slag reactions under BF‐conditions was simulated in the laboratory by smelting BF‐slag with diasporic bauxite additions in a graphite crucible. It was achieved the production of BF‐slags with higher alumina contents under the condition of constant slag basicity. The results show the beneficial effect of the bauxite addition to the quality of the produced hot metal. In accordance to its desulphurization and desiliconization as well as the increase of BF‐slag sulphur capacity and fluidity, a thermodynamic evaluation of the metal/slag reaction in respect of SiO₂ reduction and S‐transfer to the slag in relation to its Al₂O₃ content was carried out. This evaluation led to simple algebraic functions and graphs easily applicable by the BF operators. The attained metallurgical results were verified in comparison to industrial test heats with bauxite additions in the BF‐burden in USA, Canada and Europe.     

Application and analysis of slag holdup model in BF deadman

The operation of blast furnace is considerably influenced by slag performance, particularly in BF hearth. Slag holdup in deadman has negative effects on hearth, such as sharp peripheral flow of hot metal and carbon brick erosion. Therefore, it is urgent to monitor the slag holdup. In this paper, a slag holdup model was proposed to give a transient snapshot of the internal state of BF. Based on the analysis of practical example of Jingtang (Hebei, China) No. 1 blast furnace, three typical models and the slag holdup model were compared. Furthermore, the effects of slag basicity(CaO/SiO₂), MgO/Al₂O₃ ratio, temperature of hot metal, diameter of coke, shape factor of coke and voidage of deadman on slag holdup were investigated. The results show that current slag holdup model can timely predict the general trend of the permeability of the deadman and internal state of hearth. In addition, the influence extent of the six factors which affect the slag holdup is in the following order (from large to small effect): the voidage of deadman, shape factor of coke, diameter of coke, basicity(CaO/SiO₂), MgO/Al₂O₃ ratio, temperature of hot metal. The weighting ratio of these factors is 1:0.92:0.69:0.69:0.38:0.23.     

Al2O3对酒钢低铝渣黏度的影响及热力学分析

为进一步分析Al2O3含量对低铝渣黏度的影响,以酒钢高炉渣成分为基础,通过试验和FactSage热力学软件分别研究了不同Al2O3含量炉渣的黏度、液相线温度、活度和冷却结晶过程的物相变化。结果表明,在本试验的低铝渣范围内,随Al2O3含量增加,炉渣黏度增大,在1 450 ℃以上黏度低于0.45 Pa·s,炉渣流动性和稳定性良好。Al2O3活度随Al2O3含量的增加而增大,相反,SiO2活度降低也证明炉渣聚合度的增大。炉渣的冷却结晶过程则表明,在液相线温度以上时,炉渣黏度主要与炉渣结构的复杂程度有关;在液相线温度以下时,黏度受液相炉渣结构和固相颗粒含量的共同影响。     

富铅渣的性质及其还原机理

选用实验室制备的不同PbO含量的富铅渣,确定富铅渣的孔隙率和密度、软化温度、微观结构和相成分。在竖管炉中用石墨坩埚进行还原试验。研究结果表明,当温度低于900℃时,富铅渣与石墨之间没发生明显的反应。富铅渣与石墨之间的反应主要是通过液体形式进行。并对富铅渣相平衡进行热力学计算。     

Formation of Hearth Sediment during Vanadium Titano-magnetite Smelting in Blast Furnace No.7 of Chengde Iron and Steel Company

The large quantity of sediment produced in the hearth during vanadium titano-magnetite smelting in a blast furnace(BF) affects the stability of the blast furnace operation. Testing and analysis of the sediment in the hearth of Chengde Iron and Steel Company?s BF No.7 revealed that it was mainly concentrated in the location below the tuyere and above the iron notch. Notably, some of the bonding material(sediment) consisted of greater than 50% pig iron, and the pig iron distributed in the slag was granular. It is proposed that a large quantity of Ti C and Ti(C,N) are deposited on the surface of the pig iron. These high melting point materials mix with iron drops, preventing the slag from flowing freely, thus leading to the formation of bonding materials. In addition, the viscosity and melting temperature of the slag in the tuyere areas fluctuate greatly, and thus the properties of the slag are unstable. Moreover, the slag contains large quantities of carbon, which results in the reduction of Ti O2. The resultant precipitation of Ti is followed by the formation of Ti C in the slag, which also leads to an increase in the viscosity of the slag and difficulty in achieving separation of the slag-iron. In fact, all of these factors interact with each other, and as a result, sediment is formed when the operating conditions in the hearth fluctuate.     

Variation in hot metal and slag composition during tapping of blast furnace

Abstract

To determine the quality of the hot metal and the thermal conditions inside the blast furnace, the composition of the hot metal and slag must be known. Obtaining representative metal and slag samples during tapping is thus highly important to blast furnace operation. The study covered in the present report focused on hot metal and slag composition variation during tapping from a commercial blast furnace. From the results, optimal sampling time points for obtaining elemental concentrations that can be taken as representative for the whole tapping sequence were identified. It was furthermore concluded that the reliability of hot metal composition data is significantly improved by averaging elemental concentrations determined from two samples, each taken at a particular time point. One sampling, however, was found to be adequate for slag. Results from the study also showed a fairly strong correlation between amounts of silicon and carbon, sulphur and carbon, and silicon and sulphur in the hot metal, while a weaker correlation between hot metal temperature and each of these elements was observed.