Silicomanganese production from manganese rich slag

Abstract

Manganese rich slag produced by the appropriate treatment of high manganese pig iron has a high manganese content and results in low fines, is low cost and gives low excess oxygen. Manganese recovery from this slag in the form of manganese ferroalloys compensates for the excess cost of the treatment process. Manganese rich slags produced from the injection of high manganese pig iron under at optimum conditions have levels of (Mn)>35 wt-%, (Mn)/(Fe)>7.65, (Mn)/(Si)>2 and (Mn)/(P)>285, which satisfy requirements for use as raw material in silicomanganese alloy production. Various experiments were carried out to smelt high manganese slag resulting from the treatment of high manganese pig iron to produce silicomanganese in a bench scale submerged electric arc furnace. Use of such manganese rich slag in the proportion of 40% of the blend has been found to be optimum to obtain a silicomanganese alloy with the highest metallic yield and highest manganese recovery. The silicomanganese alloy produced satisfies the standard chemical specifications, with manganese and silicon contents 68 and 18%, respectively.     

转炉锰矿熔融还原工业试验研究

为打通转炉炼钢过程锰矿熔融还原技术路径,提高锰的收得率,对锰矿熔融还原过程和提高锰收得率的工艺参数进行了热力学探讨,并在某钢厂200 t转炉上开展了工业试验研究。研究结果表明:高效稳定的铁水“三脱”预处理技术是锰矿熔融还原技术成功的基本前提;通过理论计算,在炉渣中的(MnO)质量分数为5%～10%,终点[C]质量分数控制在0.13%～0.36%时,终点钢液[Mn]质量分数可控制在0.3%以上。工业试验主要通过采用双渣法冶炼操作,在确保前期铁水低磷的条件下尽可能控制少渣量、降低炉渣中氧化铁,从而实现加入锰矿后提高锰收得率;并在现有工艺控制条件下,锰矿加入10 kg·t?1以内时,工业试验可使锰矿还原过程锰收得率超过40%,平均为51.40%;为进一步提高锰收得率,建议严格将锰矿熔融还原渣料总量控制在40～60 kg·t?以内,石灰加入量控制在10～15 kg·t?1以内;研究结果为锰矿熔融还原技术的开发和应用提供重要参考。      

Study on Efficient Use of High-Manganese Pig Iron

The smelting process of high-manganese pig iron is studied to determine ways to efficiently utilize the by-product of manganese-rich slag. This process consists of two stages: 1) demanganese and carbon retention and 2) decarbonization and dephosphorization. In the first stage, oxygen is supplied at 0.5–2.0 Nm³ t⁻¹ min⁻¹. The temperature is controlled between 1300 and 1400 °C by adding iron ore to the molten bath. Ultimately, high-manganese slag, which contains more than 50% manganese oxide and semisteel with 3.2% carbon, is produced. In the second stage, oxygen is supplied at 2.0−5.0 Nm³ t⁻¹ min⁻¹ and slag-forming materials are added to the molten bath for the dephosphorization and desulfurization of the hot metal. Consequently, the iron oxide, manganese oxide, and silicon oxide contents of the high-manganese slag and the carbon, manganese, phosphorus, and sulfur contents of the semisteel are 10.8–15.3%, 70–77%, and 3–7%, and 3.2–4.2%, 0.3–1.0%, 0.12–0.22%, and 0.01–0.024%, respectively. The main mineral phases of high-manganese slag, 2MnO·SiO₂ and FeO·MnO·SiO₂, are suitable for the preparation of high-carbon ferromanganese raw materials. After further smelting, clean molten steel containing 0.03−0.08%, 0.08−0.20%, 0.005−0.02%, and 0.01−0.024% carbon, manganese, phosphorus, and sulfur, respectively, is obtained.     

A thermodynamic model for calculating manganese distribution ratio between CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 ironmaking slags and carbon saturated hot metal based on the IMCT

A thermodynamic model (IMCT-L_Mn) for calculating manganese distribution ratio between CaO–SiO₂–MgO–FeO–MnO–Al₂O₃–TiO₂–CaF₂ slags and carbon saturated liquid iron have been developed based on the ion and molecule coexistence theory. The predicted manganese distribution ratio shows a reliable agreement with the measured ones. With the aid of the IMCT-L_Mn model, the respective manganese distribution ratio of (Mn²⁺?+?O^2?), MnO·SiO₂, 2MnO·SiO₂, MnO·Al₂O₃, MnO·TiO₂, and 2MnO·TiO₂ are investigated. The results indicate that the structural units SiO₂?+?FeO play a key role in CaO–SiO₂–MgO–FeO–MnO–Al₂O₃–TiO₂–CaF₂ slags in demanganisation process in the course of hot metal treatment at 1673?K. The manganese distribution ratio at a given binary basicity range increases with CaF₂ content, while that decreases with TiO₂ content at different binary basicity scopes, which demonstrate that high Mn in the metal is favoured by TiO₂ content. In the present study, various critical experiments are carried out in an effort to clarify the effect of temperature on demanganisation ability, indicating that the lower temperature of molten metal is, the faster the rate of demanganisation reaction is and the shorter the thermodynamic equilibrium time is and the lower end-point Mn content is. It can be deduced from the obtained experimental results that the greater oxygen potential of slags or iron-based melts, lower content of basic oxides in slags, and lower temperature at reaction region is benefit for demanganisation reaction.     

铁水预处理中钛硅锰同时脱除规律及工艺

通过钼丝炉上1kg铁水和感应炉上10kg铁水的实验,研究了铁水预处理时炉渣碱度和铁水温度对脱钛硅锰的影响,并系统的分析了其脱出规律.研究表明铁水中钛硅的氧化基本不受铁水温度和炉渣碱度的影响,锰的氧化受铁水温度和炉渣碱度的影响较大,低温、低碱度有利于铁水脱锰.当铁水温度T=1280℃,碱度R=0.44,铁水中钛硅锰可分别脱除至[Si]=0.011%,[Ti]<0.005%,[Mn]=0.024%,满足了高纯生铁对锰的指标要求.     

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.     

Effect of manganese ore blends on performance of submerged arc furnace for ferromanganese production

Abstract

Manganese ore blends are used in ferromanganese production. The blend composition controls the operational performance of submerged arc furnace. A case study has been carried out at FAP, Joda, Tata Steel to better understand the process. The results of experiments revealed that the phase decomposition and decrepitation of Mn ore at low temperatures (500–900°C) in the upper part of the furnace increased the furnace top temperature and thereby promoted agglomeration of the charge, which caused the violent eruptions in the furnace. The root cause of the problems in reaction zone (bottom part) of the furnace was changes in the composition of slag, i.e. low silica and high alumina, which was also due to selection of Mn ores in the blends. Various options for silica addition were examined and compared. The pretreatment of the Mn ores and use of synthetic slag for silica adjustment options were identified to overcome the operating problems and to utilise the captive Mn ores.     

90 t转炉留渣双渣工艺钢中残余锰含量的控制

低锰钢一般要求控制转炉终点[Mn]≤0.05%,针对传统双渣工艺熔剂消耗成本高,留渣双渣工艺去锰不稳定的问题,基于热力学、动力学分析和现场数据分析,研究了碱度炉渣（R 1.68~2.00）、温度（1340~1460℃）及渣中FeO含量（FeO）(15.5%~18.7%)对留渣双渣工艺中炉渣去锰能力的影响。通过溅渣留渣期间加入部分石灰石,吹炼开始加入少量生白云石替代部分轻烧白云石和加入少量萤石以及吹炼初期采用较高枪位,加强熔池上层炉渣搅拌加速初期锰的氧化等措施,使终点[Mn]由≤0.06%降至≤0.045%,与传统双渣法比较,减少石灰用量6.5 kg/t,减少萤石1.48 kg/t,铁皮单耗降低6.42 kg/t,明显降低冶炼熔剂成本。     

[Mn]/[Si]对小方坯表面夹渣物的影响

主要分析了[Mn]/[Si]对小方坯表面夹渣物的影响,提出了防止表面夹渣物产生的措施经实践检验,随着[Mn]/[Si]的提高,铸坯表面夹渣明显减少。     

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.     

Thermodynamics of carbon and oxygen solutions in manganese melts

The thermodynamics of carbon and oxygen solutions in manganese melts is studied. An equation for the temperature dependence of the activity coefficient of carbon in liquid manganese is obtained (γ _C(Mn) ⁰ = ?1.5966 + (1.0735 × 10^?3)T). The temperature dependence of the Gibbs energy of the reaction of carbon dissolved in liquid manganese with the oxygen of manganese oxide is shown to be described by the equation ΔG _T ⁰ = 375264 ? 184.66T(J/mol). This reaction can noticeably be developed depending on the carbon content at temperatures of 1700–1800°C. The deoxidation ability of carbon in manganese melts is shown to be much lower than that in iron and nickel melts due to the higher affinity of manganese to both oxygen and carbon. Although the deoxidation ability of carbon in manganese melts increases with temperature, the process develops at rather high carbon contents in all cases.     

Dephosphorization of Mn-based alloys

The critical oxygen partial potential of dephosphorization in liquid Mn-base alloys under oxidizing or reducing conditions has been determined by thermodynamic analysis. Under oxidizing conditions, thermodynamic conditions to achieve dephosphorization and avoid manganese oxidizing were given. The results of thermodynamic analysis show that BaO-base slag can be an effective dephosphorization agent for Mn-base alloys. Under reducing conditions, the high degree of dephosphorization in Mn-base alloys can be obtained based on thermodynamic analysis. In experimental work, BaCO₃ was added to remove phosphorus from Mn–Fe–C melts. The time needed for equilibration of the dephosphorization reaction of Mn–Fe–C melts was determined at 1573, 1623 and 1673 K. The refining results were experienced as dephosphorization efficiency ≠_p = (%[P]₀ ? %[P])/%[P]₀. Moreover, the effect of the initial content of Si and C on ≠_p was investigated. ≠_p in the Mn–Fe–C melts was also given as a function of temperature. Dephosphorization reaction in Mn–Fe–C melts is of first order.     

Oxidation of molten impurities in converters by means of combustion flames: Thermodynamic principles. 2. Interaction of flame with metal and slag in converter bath

Thermodynamic analysis is applied to the physicochemical processes in the converter bath when intensifying bath heating by means of gas–oxygen burners. In the converter’s working space, when the combustion flames interact with the liquid bath, the oxygen and natural gas supplied through the burners and the oxygen supplied through the tuyere interact in a bubbling slag–metal emulsion. As a result, iron and the impurities are oxidized. The use of such burners changes the gas composition: not only O₂, CO, and CO₂ are present, but also H₂ and H₂O, which changes the oxidative capacity of the gas phase. The presence of solid carbon (for example, pulverized coal) in the burner flame may be used to control and intensify the combustion process. Combustion is most effective in the oxidation of carbon to CO when the oxygen excess is less than 1.0. The oxidation conditions of carbon in the melt change with variation in its activity as a function of its concentration and the temperature. The equilibrium in the M–O–C system may be described by the oxygen partial pressure \({P_{{O_2}}}\), which may be regarded as a universal characteristic. In addition, the equilibrium may be assessed on the basis of the associated ratios \({P_{CO}}/{P_{C{O_2}}}\) and \({P_{{H_2}}}/{P_{{H_2}O}}\) It is found that iron may be oxidized by oxygen and, to some extent, by carbon dioxide. At 1600–2000 K, there is practically no oxidation of iron by steam. The carbon dissolved in the steel is oxidized relatively effectively by oxygen and carbon dioxide until its concentration is less than 0.1% C. Steam oxidizes carbon very poorly and is not much more effective with manganese and silicon. With increase in temperature, the rate at which carbon dissolved in steel is oxidized by oxygen increases, while the oxidation rate of manganese and silicon falls. Above 1800 K, superoxidized slag with a high FeO content actively oxidizes silicon (to <2% Si), manganese (to <1% Mn), and carbon (to <1.5% C).     

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.     

Mechanism and Kinetics of Optimized Slag Formation in an Oxygen Converter

One of the most important technical requirements in modern high-speed converter steelmaking is early formation of the furnace slag. Early slag formation helps optimize conditions for the oxygen blow and facilitates thorough refining of the steel in the converter. The main factors that determine the rate of slag formation are the contents of oxides of iron and manganese in the slag, the temperature of the steel, and the conditions under which the lime is added. When converter steelmaking is done on low-silicon, low-manganese pig iron with use of a portion of the slag from the previous heat, the slag tends to form earlier and intensive decarbonization takes place as the blow proceeds in the dynamic regime. Such steelmaking is also more efficient as a whole, since it reduces the amount of silicon and manganese in the pig and shortens the heat. __________ Translated from Metallurg, No. 8, pp. 42–43, August 2005.     

顶底复吹转炉冶炼低碳钢的工艺研究

以实际生产数据为依据,分析研究涟钢1座100 t顶底复吹转炉冶炼低碳钢08Al(%:≤0.08C、0.17～0.37Si、0.25～0.65Mn、≤0.030P、≤0.030S、0.015～0.65Als)的工艺。发现其冶炼后期底吹强度足,导致部分钢水过氧化,实际终点碳氧浓度积与理论的平衡值有一定偏差;转炉终渣碱度在4～5时,磷、硫在渣-钢间的分配系数最大,脱磷、脱硫效果最好,其终点[C]高,(FeO)低,炉渣氧化性低,不利于脱磷但利于脱硫;冶炼终点钢水温度越低,[C]越高,钢水、炉渣氧化性越低,钢水中残锰含量越高。     

精炼渣对高锰钢中非金属夹杂物的影响

 为了研究精炼渣对高锰钢中非金属夹杂物的影响,采用渣/钢平衡的试验方法研究了MgO SiO2 Al2O3 CaO系精炼渣对Fe xMn高锰钢(x=10%, 20%)中非金属夹杂物的影响。结果表明,无顶渣情况下,高锰钢中夹杂物主要为MnO类和MnO Al2O3类2类。加入精炼渣后,夹杂物类型发生了变化,主要有 MnO类、MnO SiO2类和 MnO Al2O3 MgO类3类,其中MnO SiO2类数量最多。采用ASPEX扫描电镜对夹杂物的平均成分进行分析,无顶渣时高锰钢中夹杂物的成分主要是MnO,质量分数在95%以上,并含有质量分数为4%左右的Al2O3。加入精炼渣后,夹杂物中MnO质量分数降低,SiO2质量分数显著增加,MgO质量分数增加。热力学计算结果表明,加入精炼渣后,渣/钢间反应4［Al］+3(SiO2)=2(Al2O3)+3［Si］和2［Mn］+(SiO2)=2(MnO)+［Si］的吉布斯自由能均小于零,这说明在本试验条件下,钢液中的［Al］和［Mn］会还原渣中SiO2,生成的［Si］进入钢液,进而与钢液中的［O］结合,导致夹杂物中SiO2增加。     

Production of high carbon ferromanganese using manganese rich slag in the charge

The possibility of replacement of the high cost sinter manganese ore by manganese rich slag for the production of high carbon ferromanganese was experimentally demonstrated. The experimental heats were designed and carried out to optimize this replacement through the adjustment of different production parameters. The results of pilot plant experimental heats showed that replacement of 50% of the sinter in the blend (or 25% of the blend) by slag containing 32% Mn and operation under slag basicity 0.9 and low (MgO)/(CaO) ratio of about 0.2-0.3 are the optimum conditions to attain the highest manganese content in the produced ferromanganese, the highest manganese recovery and the highest metallic yield. The industrial application of reusing manganese slag clarified the economic efficiency of charging manganese slag up to 20-25% of the blend in reducing the production cost due to reducing the cost of manganese ores. Charging of 20-25% manganese slag reduces the cost of manganese ores and the total production cost by about 13 and 6% respectively, comparing with the conventional technology (without using manganese slag in the blend).     

转炉铁水预处理脱磷的影响因素

 基于炉外铁水深度预脱硫+转炉铁水预脱磷的铁水预处理工艺是当今低磷或超低磷钢冶炼的重要工艺平台,其中转炉铁水预处理脱磷是关键的技术环节。以国内“双联转炉炼钢法”预脱磷炉实践为出发点,在实验室高温炉上通过顶加脱磷剂、浸入吹氧进行了铁水模拟转炉预脱磷影响因素的试验研究,比较了铁水温度、铁水初始硅质量分数w(Si)_i、脱磷渣碱度、供氧制度、搅拌强度、萤石加入量对脱磷效率的影响。结果表明,各因素对脱磷率影响的顺序为铁水温度＞w(Si)_i＞供氧制度＞脱磷渣碱度、搅拌强度＞萤石加入量;适宜的工艺参数为铁水温度为1 300 ℃,w(Si)_i 为0.10%～0.26%或低于0.30%,脱磷渣碱度为2.9～3.0,供氧制度中气氧与固氧各占50%或固氧稍偏多,维持较高的搅拌强度;转炉内铁水预脱磷处理可不加萤石。     

Dissolution behaviour of manganese ore in basic oxygen furnace type slag

In order to improve manganese yield during the reduction process of manganese ore in blowing practices employing less slag at BOF, the dissolution behaviour of manganese ore in slag has been studied in an experimental scale. The effect of temperature, slag composition, addition of CaF₂, and pre-treatment of manganese ore was examined for the dissolution behaviour of manganese ore into BOF type slags. The precipitation of (Fe,Mn)O phase in slag was observed during the addition of manganese ore. The dissolution rate of manganese ore into molten slag increased with temperature, and also increased with the initial contents of FeO, MgO and MnO. However, the effect of slag basicity was not evident on the dissolution rate of manganese ore into slag. The addition of CaF₂ and pre-treatment of Mn ore were very effective to promote the dissolution of manganese ore into slag.