Parameters affecting manganese oxidation in top blown basic oxygen converter

The data obtained from 84 heats carried out in a 90-t top blown basic oxygen converter were used to study the effects of slag composition and temperature on the activity coefficient and activity of manganous oxide in the slag as well as on the manganate capacity and the manganese distribution between slag and metal. In addition, the dependence of manganese activity in the metal on the concentration of maganese and temperature was also investigated. The present study carried out in wide ranges of temperature, 1350–1690°C, and slag basicity expressed as (CaO)/(SiO₂), 1.4–10.6, clarifies the dependence of MnO activity coefficient mainly on temperature. The activity coefficient of MnO increases by decreasing the temperature. On the other hand, activity of MnO increases by increasing MnO concentration and temperature. Both activity coefficient and activity of MnO in the slag slightly increase by increasing the slag basicity. At constant temperature, the activity of Mn in the molten metal varies linearly with Mn concentration and tends also to increase with increasing temperature at constant Mn concentration. The increase in manganese activity by increasing Mn concentration is much steeper at high temperatures. The manganate capacity as well as manganese distribution ratio decrease with increasing temperature at constant basicity and tend also to slightly decrease with increasing slag basicity at constant temperature. Equations describing the parameters affecting activity coefficient and activity of manganous oxide in the slag, manganese activity in the metal, manganate capacity and manganese distribution ratio have been derived.     

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.     

Silicon distribution between blast furnace slag and hot metal

Abstract

Analyses of slag and hot metal in daily average samples from a 1033 m³ blast furnace charged with 100% self-fluxing sinter, and published data from two 2000 m³ furnaces with different proportions of various pellet types in the charge, have been used to calculate the ‘silicate capacity’ of slag and to investigate the effects of basicity and temperature on silicate capacity and silicon distribution ratio. Regression equations have been developed which show that both silicate capacity and silicon distribution ratio increase with increasing basicity and decreasing temperature. The temperature effect is very large compared with the influence of slag basicity. Similar relationships between silicate capacity and temperature are obtained individually for both furnace types as well as by combining their data together and with the data from other furnaces. Silicon distribution ratios calculated by using the silicate capacity of the slag compare well with the results found from slag and metal analyses.     

SiO2-TiO2-CaO-MgO-FeO-MnO渣系与脱钛过程铁水中Ti-Si平衡热力学模型

 为降低铁水中钛含量,采用烧结矿或球团矿进行铁水包脱钛预处理。基于共存理论,采用Matlab编程软件,建立了铁水包脱钛典型渣系SiO2-TiO2-CaO-MgO-FeO-MnO中TiO2活度计算模型。结果表明,随着MgO、FeO、MnO摩尔分数和炉渣碱度的增大,脱钛渣中TiO2活度下降;随着TiO2摩尔分数的增大,TiO2活度提高。脱钛终点铁水中的钛含量与硅含量呈线性关系,其斜率受温度、铁水成分以及炉渣中SiO2和TiO2活度的影响。计算结果与试验结果及实际生产数据十分吻合。     

Manganese Capacity and Optical Basicity of Metallurgical Slag

In practice, the concept of slag capacity is used to assess the distribution of elements between condensed phases. In particular, researchers determine the sulfide, phosphate, chromate, and nitride capacity of slags. In the present work, a mathematical model of the manganese capacity is derived. To that end, two equivalent forms of the manganese capacity are derived from the equilibrium constants of the redox reaction of manganese [Mn] + (1/2)O₂ = (MnO). These indices reflect the manganese distribution between the metal and the slag and do not depend on the composition of the metal and the gas phase. One version takes the form C^Mn = K_Mn/γ_(MnO). If we take logarithms and use the known equilibrium constant K_Mn of the redox reaction, we may write logC^Mn = 21122/T–logγ_(MnO)–4.5509. To find the activity coefficient of manganese oxide, equilibrium between hot metal, cast iron, ferrosilicon, ferromanganese, and the corresponding slags is studied experimentally at various temperatures, on circulatory apparatus permitting the study of heterogeneous equilibria involving the gas phase. Using the apparatus, the change in gas volume in the reactions is monitored and automatically recorded and constant pressure is automatically maintained in the system. The attainment of equilibrium is also judged from the constancy of chemical composition of the condensed phases over time. If numerical values of γ_(MnO) are available, they may be used to calculate the manganese capacity of all the slags from the equation already given. For the sake of practical convenience, the manganese capacity is written in terms of the temperature and the optical basicity λ_ed calculated from the electron density known for elements in the periodic table: logC^Mn =–1.866λ_ed + 21049/T–3.131 (R² = 0.997). According to this equation, the manganese capacity depends only on λ_ed and the temperature and may be used for metals and slags of practically any composition.     

CaO-SiO2-MgO-Al2O3-BaO渣系脱硫能力研究

为了探究温度、碱度（R）、MgO质量分数和BaO质量分数对高炉渣脱硫能力影响，以酒钢现场高炉渣实际成分为基准，选取分析纯化学试剂配制实验渣样，采用双层石墨坩埚法研究了含钡渣系的脱硫能力，并考察BaO对脱硫动力学条件的影响。研究结果表明，增大高炉渣碱度，提高渣中MgO质量分数均能使硫分配比增加，炉渣脱硫能力增强。渣中BaO质量分数由0增加到4%，硫分配比先逐渐升高后略有降低，BaO质量分数为35%左右时硫分配比达到最大值。BaO质量分数增加使得熔渣中硫的传质系数增大，脱硫速率明显提升。     

Reduction kinetics of manganese oxide in basic oxygen furnace type slag

In order to improve manganese yield during the reduction of manganese ore, the reduction kinetics of manganese oxide in BOF type slag has been investigated on an experimental scale. The reduction rate of (MnO) was promoted for the slag of low basicity and high contents of (FeO). The maximum reduction rate of (MnO) has been found for an iron melt with carbon mass contents of 1.9 %. The silicon in metal may accelerate the reduction of manganese oxide in slag. The kinetic model for the reduction rate of (MnO) has been formulated based on the assumption that the reduction of (MnO) was controlled by the mass transfer through the metal and slag boundary layers at the metal/slag interface. The result calculated by the kinetic model showed a good agreement with the experimental one. The reduction behaviour of (MnO) can be described by the present model.     

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.     

H2-C熔融还原条件下渣金间磷的分配比的试验研究

 通过300kg级氢-碳熔融还原热模拟试验,从热力学角度分析了氢-碳混合熔融还原条件下磷的分配比,运用熔渣规则溶液模型计算了氧化钙、二氧化硅、氧化镁、氧化铝、氧化亚铁、五氧化二磷六元熔渣组分的活度、活度系数,进而计算出一定温度条件下熔渣的磷容量以及渣金平衡时磷分配比的理论值。通过比较理论计算得出的磷分配比与试验中磷的分配比的差异,解析产生差异的原因,进而为氢-碳混合熔融还原炼铁新工艺冶炼高磷铁矿提供参数。试验结果表明：用熔渣规则溶液模型计算渣金间的磷的分配比是合适的,氢-碳熔融还原工艺可以利用高磷铁矿。     

Equilibria between liquid Mn-Si alloys and MnO-SiO2-CaO-MgO slags

The activity of silicon in manganese-silicon melts was determined at 1500°C. The results are in general agreement with the thermodynamic data of the iron-silicon system. Equilibria between manganese-silicon melts and slags containing MnO, SiO₂, CaO, and MgO were studied at 1400 and 1500°C in silica and magnesia crucibles. An empirical relationship easy to use in practice was derived, expressing the manganese and silicon distribution ratio between slag and metal as a function of the slag basicity. This relationship describes equilibria pertinent to the silicothermic reduction of manganese oxide and the production of silicomanganese. The present knowledge of the activities in the slag and metal phase is adequate to explain the experimental results. The presence of up to about 10 pct CaF₂ in the slag makes it possible to maintain a higher slag basicity and therefore a lower activity of silica, resulting in lower silicon contents in the metal. Iron contents of up to about 20 pct in the metal cause a slight increase in the silicon content of the metal under otherwise similar conditions. The effect of 1 to 2 pct carbon in the metal on the equilibrium was roughly estimated and found to be almost negligible.     

Thermodynamics of MnO, FeO, and phosphorus in steelmaking slags with high MnO contents

The thermodynamics of managanese oxide and iron oxide and the phosphate capacity of CaO-SiO₂-MnO-Fe _t O-P₂O₅-MgO_sat slags with high MnO contents relevant to the smelting of MnO ores in steelmaking were investigated. Previous data were limited to about 5 pct MnO, whereas in this study MnO contents up to 25 pct were studied. The activity of MnO showed positive deviation from ideal behavior and increased with basicity, while that of Fe _t O decreased with basicity. This is reflected in that the manganese distribution ratio at a given Fe _t O content decreases with basicity and high Mn in the metal is favored by high basicity. CaF₂ additions up to 4 pct did not affect the activities of MnO and Fe _t O. The activity coefficient of P₂O₅ decreases and the phosphate capacity increases with basicity. There was not adverse effect of high MnO contents on the dephosphorizing abilities of the slags.     

用矿热炉和摇炉生产金属锰的工艺探讨

该工艺是在矿热炉中用焦炭还原锰铁矿石,将还原反应的温度控制为1500℃以下,渣碱度ω(CaO)/ω(SiO2)为0.16,SiO2的质量分数为18%,生产出的富锰渣中MnO的质量分数不小于70%,同时有副产物碳素锰铁产生。然后将富锰渣热兑入摇炉中,加石灰精炼生产调和渣,使其碱度提高到2.0,这样有利于脱除磷、硫,并降低SiO2的活度。最后在摇炉中加入工业硅还原调和渣中的锰,获得锰质量分数不小于99%的金属锰,节能效果明显。     

富渣锰硅工艺的初步探讨

提出了生产高富锰渣锰硅生产新工艺,在理论上从温度、活度、碱度几方面论证了其可行性。通过精确配料、严格控制温度、还原剂的粒度和加入量及碱度,在小型矿热炉上进行了试验,生产效果良好。结果表明,炉料MnO/SiO_2比值是该工艺的一个重要参数,且碱度对渣中锰含量影响明显。     

环保型高磷铁水预脱磷渣的脱磷性能研究

实验室条件下采用间接测量法,测定了CaF2系和B2O3系脱磷渣的磷分配.即首先测量磷在液态渣和固态铁间的分配比,再通过计算得到磷在液态渣和铁水之间分配比,同时根据渣系成分和光学碱度计算了磷容量.同时采用了扫描电镜、能谱分析与X射线衍射分析技术对脱磷渣进行了研究.实验结果表明,B2O3系预脱磷渣的磷容量远大于CaF2系预脱磷渣的磷容量,因此可以用B2O3全部替代CaF2作为助熔剂进行高磷铁水的预脱磷处理,2种渣系的磷分配均随渣中有效CaO含量的升高而升高.用B2O3作为助熔剂时,B2O3能与渣中高熔点物质2CaO·SiO2和3CaO·P2O5反应生成低熔点物质,从而起到助熔的作用.且w(B2O3)/w(CaO)比值为0.16时,磷分配比为最高值,即该渣脱磷能力最强.     

Effect of Direct Reduced Iron on Oxygen Distribution between Slag and Bath in Electric Arc Furnaces

Test charges containing 40 to 95% direct reduced iron (DRI) were melted in two identical electric arc furnaces. Slag and the corresponding metal samples were collected from the furnace in the course of the steelmaking process and from the ladle after deoxidation and composition adjustment. The temperature was measured just before sampling. The activity coefficient and activity of total ferrous oxide in the slag were determined by using the theory of regular ionic solutions. The activity was used to assess the oxygen concentration in the metal. The effect of slag composition on Fe_tO activity coefficient and activity was investigated. The enthalpy of solution of total ferrous oxide in the slag was found to be 78 kJmol^?1. The ratio of activity to concentration of Fe_tO is equal to 0.0138. The effects of DRI proportion and degree of metallization on α^Fe,O were investigated. The activity coefficients of oxygen and carbon in the bath are 0.7243 and 1.0825, respectively. The activity coefficient and activity of oxygen in the metal decrease with increasing carbon concentration, carbon activity coefficient and activity. An “oxide capacity” has been developed which does not need the use of α^Fe,O. It correlates strongly with temperature over the range from 1500 to 1670°C. The basicity has only a small influence compared with the large temperature effect. The oxide capacity increases with growing DRI proportion and decreases with increasing metallization between 93.43 and 95.25%. Oxygen distribution between slag and metal was assessed by using the oxide capacity. Calculated values compare well with the corresponding data obtained from slag and metal analyses. The oxide capacity can be used in monitoring the steelmaking operation.     

转炉生产低磷钢的脱磷反应热力学

 为实现磷质量分数小于0.010%的低磷钢批量生产,系统研究了转炉脱磷反应热力学。分析了影响转炉渣-金间磷分配比LP的主要因素,研究了P2O5活度系数和脱磷反应氧分压的定量确定方式,以及碳、磷选择性氧化问题。研究结果表明：LP主要受氧分压、P2O5活度系数和温度的影响;P2O5活度系数采用修正的柯热乌罗夫规则离子溶液模型计算较为准确;脱磷反应氧分压受炉渣氧分压控制,炉渣氧分压主要取决于钢中碳含量、炉渣碱度和温度。对传统复吹转炉生产磷质量分数小于0.010%低磷钢的工艺条件是：终渣碱度w(CaO)/w(SiO2)≥3.0,终渣w(MgO)≤9.0%,终点碳w(［C］)≤0.065%,终点温度控制在1873～1923K范围。     

转炉终点渣钢间锰平衡状况分析

为了推广锰矿直接还原技术在转炉内的使用,对转炉终点条件下锰矿的热分解、熔融还原和渣钢间平衡状态进行了分析。利用热力学分析方法讨论了国内外转炉锰矿直接合金化锰的平衡状态。结果表明,在转炉终点时刻,锰矿以MnO形式存在于渣中;锰在渣钢间的平衡主要以铁、锰竞争氧化的形式存在;理论计算锰分配比和实践生产数据有相同的趋势,且计算值大于实践生产数据;高温、高碱度、高w([C])、低w((TFe))可以降低锰分配比;渣量越小,锰收得率越高。此外,讨论了进一步提高转炉锰收得率的控制工艺。     

On sulphur behaviour in steelmaking with sponge iron in an electric arc furnace

The sulphur behaviour in steelmaking by melting of charges containing from 38.7 to 95.4 wt.% sponge iron in the metallic input in a 70 t UHP electric arc furnace is investigated. The effect of both slag composition and temperature on the sulphide capacity of the slag and on the sulphur distribution ratio between slag and metal is studied. The kinetics of desulphurization are also treated. Regression analysis shows that the logarithm of sulphide capacity varies linearly with total lime equivalent, theoretical optical basicity and logarithm of slag basicity. Equations relating the sulphide capacity to these parameters as well as to the temperature are given. Based on these equations, functional relationships for the calculation of sulphur distribution between slag and metal are derived. Metallurgical reactions for metal desulphurization by slag and equilibrium relationships are given from which the slag-metal sulphur partition ratio can be calculated. In all cases, the results of the calculations are in line with the experimental data. The rate of desulphurization is expressed by an equation based on the boundary layer diffusion theory. Under the conditions of the present investigation, the activation energy of desulphurization is found to be 39 kJ/mol and the mass transfer coefficient of sulphur at 1600°C is equal to 0.014 cm/s.     

Multicomponent diffusion in molten slags

A method for investigating the diffusion of metal cations in multicomponent slag systems was developed. This method used microprobe analysis and allowed the analysis of the diffusion of multiple species within a single system. This project focused on the diffusion behavior of manganese, iron, calcium, and silicon in silicate slags, in order to simulate industrial steel and ferromanganese production. The molecular structure of CaO-Al₂O₃-SiO₂ slags was investigated with Raman spectroscopy, and oxidation states of manganese and iron in slags of varying composition were determined. This study identified the variation in diffusivity of slag components with changes in composition and temperature of multicomponent slag systems. An empirical model based on the correlation between optical basicity and diffusivity was developed to predict the multicomponent diffusivity of ionic species in molten silicate slags. The model takes into account properties of the bulk slag and the network forming ability of the diffusing species. The relative rate of diffusion of metal cations is proportional to the optical basicity coefficient of that species, while the rate of diffusion of all species increases exponentially with the calculated optical basicity of the bulk slag.     

Sulphur partition between hot metal and high alumina blast furnace slag

Abstract

The sulphur partition ratio between hot metal and high alumina blast furnace slag (>18% alumina) has been examined on cast by cast basis for G blast furnace of Tata Steel. Equilibrium sulphur partition ratio was calculated from sulphide capacity with the help of oxygen activity in the melt. Oxygen activity was calculated from SiO₂/Si, MnO/Mn and CO/C equilibria. The equilibrium sulphur distribution calculated by considering the reaction [C]+[O]=(CO)_g in equilibrium for estimation of oxygen activity was very close to measured sulphur distribution ratio on cast by cast basis. Use of MnO/Mn pairs gives very high oxygen activity compared with SiO₂/Si and CO/C pairs.