低品位硼铁矿硼铁分离的热力学研究

 对低品位硼铁矿碳热还原分离铁硼进行了热力学分析,分析结果表明：1500 ℃以下硼铁可以通过选择性还原进行分离,矿石中的氧化物杂质对其没有影响。按化学当量C/O = 1配碳,进行了差热及马弗炉焙烧实验。实验结果表明：由于该矿本身相互嵌布特点,焙烧温度在1200 ℃以下时硼铁分离效果不好。焙烧温度过高选后硼铁精矿粉品位变化不大,能耗增大。因此,最佳的焙烧温度为1200～1350 ℃,在此温度下能使硼铁分离,铁硼精矿粉品位分别达到80％和12％以上。实现了低品位硼铁矿的综合利用。     

Oxidation of Silicon and Boron in Boron Containing Molten Iron

 A new process of directly smelting boron steel from boron containing pig iron has been established. The starting material boron containing pig iron was obtained from ludwigite ore, which is very abundant in the eastern area of Liaoning Province of China. The experiment was performed in a medium frequency induction furnace, and Fe2O3 powder was used as the oxidizing agent. The effects of temperature, addition of Fe2O3, basicity, stirring, and composition of melt on the oxidation of silicon and boron were investigated respectively. The results showed that silicon and boron were oxidized simultaneously and their oxidation ratio exceeded 90% at 1 400 ℃. The favorable oxidation temperature of silicon was about 1 300-1 350 ℃. High oxygen potential of slag and strong stirring enhanced the oxidation of silicon and boron.     

Effect of alumina on slag–metal separation during iron nugget formation from high alumina Indian iron ore fines

Abstract

Iron nuggets can be obtained from ore–coal composite pellets by high temperature reduction. Alumina in the ore plays a vital role in slag–metal separation during nugget formation, as it increases the liquidus temperature of the slag. In this study, the effect of carbon content, reduction temperature and lime addition on slag–metal separation and nugget formation of varying alumina iron ore fines were studied by means of thermodynamic modelling. The results were validated by conducting experiments using iron ore fines with alumina levels ranging from 1·85 to 6·15%. Results showed that increase in reduction temperature enhances slag metal separation, whereas increasing alumina and carbon content beyond the optimum level adversely affects separation. Carbon below the required amount decreases the metal recovery, and carbon above the required amount reduces the silica and alters the slag chemistry. Optimum conditions were established to produce iron nuggets with complete slag–metal separation using iron ore–coal composite pellets made from high alumina iron ore fines. These were reduction temperature of 1400°C, reduction time minimum of 15 min, carbon input of 80% of theoretical requirement and CaO input of 2·3, 3·0 and 4·2 wt-% for 1·85, 4·0 and 6·15 wt-% alumina ores respectively.     

含碳球团生产珠铁的试验研究

 采用以铁精粉、煤粉和石灰石为主要原料制成含碳球团,在1573、1623、1673K下进行了不同加热时间的还原试验研究,并分析计算了炉料带入硫的去向。试验结果表明：在温度为1673K、12min时,渣铁已经能够很好的分离。所得珠铁中碳、硫的质量分数分别为3.53%和0.17%,珠铁的内部组织结构主要由珠光体和渗碳体组成。渣中以硅酸钙(CaSiO3)和硅酸二钙(Ca2SiO4)为主,含有少量的钙镁橄榄石(CaMgSiO4)和玻璃体。计算得知：炉料带入的硫中24.61%进入渣、61.91%进入铁、13.48%进入空气。     

Experimental Study on Deep Desulfurizer in LF Process

 Abstract： CaO-Al2O3-SiO2-CaF2-MgO was selected as the slag system for desulfurization in LF process. The reaction between steel and slag during desulfurization has been simulated by using Factsage software to study the influence of component on the sulfur distribution ratio. In order to research the influence of CaO content, aluminum powder content and its granularity on desulfurization, laboratory experiments have been carried out in a 200 kg inductive furnace. Results showed that the optimal composition of deep desulfurizer is wCaO=64% and aluminium powder 10% with a granularity of 30 μm. Industrial trials showed that the main composition range of final slag in LF process is wCaO=530%-570%, wAl2O3=234%-251%, wSiO2=81%-100%, and wCaF2=32%-47%. The sulfur mass percent in steel is lower than 00008% with a desulfurization rate above 89%. According to the result of industrial production, this desulfurizer could meet the production requirement for ultra-low sulfur steel, of which sulfur mass percent is under 00015%.     

含硼高硅铁水脱硅时硼的氧化

 提出以我国辽东地区硼铁矿经高炉分离后的含硼生铁为原料直接冶炼硼钢。针对含硼铁水中硅、硫含量较高的特点,以及有价元素硼的进一步提取利用,首先研究了铁水中主要元素硼的氧化行为。再利用中频感应炉、石墨坩埚或刚玉坩埚,以Fe2O3为氧化剂,研究了温度、Fe2O3与CaO添加量、熔体成分等因素对Si、B氧化的影响。结果表明,Si、B氧化几乎是同步的,在1 400 ℃下氧化率均可达到90%;实验结果和有关热力学计算表明,适宜的脱硅温度应在1 400 ℃以下;增加氧化剂Fe2O3有利于脱硅和硼的氧化,本实验条件下CaO添加量对脱硅和硼氧化影响不大。     

Effect of Boron on Morphology of Inclusions in Tire Cord Steel

 Abstract： B2O3 was added to tire cord steel during refining in a carbon tube furnace. The influence of boron on the deformability of oxide inclusions was studied by metallographic and scanning electron microscope (SEM) observations. The melting points of boron-bearing compound oxide inclusions were calculated using Factsage software. The results showed that the main inclusion was a boron-bearing compound oxide and the deformation properties of the inclusions were clearly improved by adding B2O3. As the boron content was increased from 00046% to 0039%, the proportion of long strip type inclusions changed slightly and the number of inclusions decreased. The low-melting point areas of the MnO-SiO2-Al2O3 and CaO-SiO2-Al2O3 ternary system increased with the addition of B2O3. Moreover, the area increased with the increase of B2O3 content. Clear improvements in the deformation ability of the inclusions occurred when the B2O3 mass percent rose to 5% in the CaO-SiO2-Al2O3 inclusion system and to 10% in the MnO-SiO2-Al2O3 inclusion system.     

Slag/metal Separation Process of Gas-reduced Oolitic High-phosphorus Iron Ore Fines

Slag/metal separation process of the highly reduced oolitic high-phosphorus iron ore fines was investigated. Samples were prepared using the reduced ore fines （metallization rate： 88%） and powder additives of CaO and Na2CO3. Slag/metal separation behavior tests were conducted using a quenching method and the obtained metal parts were subjected to direct observation as well as microstructure examination with SEM and EDS; iron recovery and phosphorus distribution tests were conducted using a Si-Mo high temperature furnace and the obtained metal parts were examined by ICP-AES analysis and mass measurement. Thermodynamic calculation using coexistence theory of slag structure was also performed. Results show that temperature for slag/metal separation must be higher than 1823 K and a satisfying slag/metal separation of the highly reduced ore fines needs at least 4 min; phosphorus con- tent of hot metal is mainly determined by thermodynamics; temperature of 1823-1873 K and Na2CO3 mixing ratio of about 3 % are adequate for controlling phosphorus content to be less than 0.3 mass% in hot metal; temperature, time and Na2CO3 mixing ratio do not have significant effect on iron recovery, and iron recovery rate could be higher than 80% as long as a good slag/metal separation result is obtained.     

HIsmelt熔融还原主反应器能质流转模型构建与验证

 HIsmelt熔融还原炼铁工艺以铁矿粉和煤粉作为原料,流程中不需要烧结、球团和焦化,与高炉炼铁流程相比具有降碳减排等优势。明晰能质流转过程对HIsmelt熔融还原炼铁实际生产具有指导意义。基于物料平衡、热平衡方程,对输入和输出HIsmelt主反应器物质和能量进行平衡计算,建立能质流转模型,并结合FactSage中Equilib模块计算的各元素在渣铁两相间的质量分配比及实际生产数据对其进行修正。该模型可以计算原料和燃料成分、矿煤质量比、二次燃烧率、热风氧含量等参数对铁水温度、炉渣成分、热风量、煤气量等主要冶炼指标的影响。其次依据该模型,进行了物料平衡、热平衡计算,依据实际生产数据对模型计算结果进行了验证,结果表明该模型与实际生产数据契合度较高。探究了矿煤质量比对冶炼的影响,矿煤质量比为1.39～1.45时,矿煤质量比降低0.1,会使二次燃烧率降低0.23%,进而造成煤气化学能的利用率降低,同时需要更多的热风使煤粉燃烧,热风量和煤气产生量增加,可以通过适当提高热风氧含量以提高二次燃烧率并使煤气量降低来改善;矿煤质量比降低0.001,会使铁水温度升高3.76 ℃,有利于铁水后续的加工处理,但铁水温度升高使铁元素在铁液与渣中的比值降低,使炉渣FeO质量分数升高0.026%,增加铁损,可通过降低富氧热风喷吹量来降低铁的氧化量,从而降低铁损。     

Phosphorus Removal of High Phosphorus Iron Ore byGasBased Reduction and Melt Separation

A large deposit of high phosphorus iron ore in China contains an average of 1.2% phosphorus and 50% iron and it has not been utilized. In current work, a novel process to remove phosphorus of the ore has been proposed. The novel process has been demonstrated theoretically and experimentally. The theoretical work (numerical simulation) was carried out with HSC chemistry package and a mathematical model developed using the coexistence theory of slag structure. Gas-based reduction and melt separation experiments were then designed and conducted. Simulation results shows that that all iron compounds in the ore could be reduced to metallic iron using CO/ H2 under temperature above 1000K and the yield of iron is more than 90% under either atmosphere; P can not be reduced and exists as Ca3(PO4)2; in the melt separation process, iron metallization ratio, melting temperature and CaO-adding ratio affect the phosphorus partition between slag and molten metal and CaO-adding ratio is the most distinguished parameter. Results of gas-based reduction agreed well with the simulation except for iron metallization ratio being less than predicted. This difference is mainly attributed to kinetic condition. Results of melt separation experiment show most P is left in the slag sample and some P in the metal sample exists as slag inclusion..     

Process of Re-Resourcing of Converter Slag

 The process of “re-resourcing of converter slag” was put forward based on the analysis of the existing steel slag treatment process. The converter slag obtained from Jinan steel plant was studied. After grinding, the slag contained 33% of iron particles, 5484% of magnetic part (wTFe=20%), and 4184% of non-magnetic part, which could be used for making cement directly. At a temperature below 1000 ℃, the non-magnetic Fe2O3 in the slag could be efficiently reduced to magnetic iron by pure H2 and CO. The slag after precise reduction had high degree of dispersion and did not get sintered, which provided an optimum condition for the separation of iron and impurities. To separate the slag and enrich the iron after reduction, the laboratory-scale device of magnetic separation was designed and made. The process of slag re-resourcing, which included magnetic sorting, precise reduction, magnetic separation, and removal of free calcium oxide (f-CaO), was proposed to obtain iron-rich magnetic materials and cement adulterant materials. Through this process, 33 kg iron particles, 150 kg iron-rich material and 700 kg cement could be obtained in each ton slag. Besides, this process to recycle converter slag had a lower energy and material consumption and no pollutant emission.     

基于铝土矿配碳球团还原熔分过程的渣相组成

 试验采用煤基直接还原熔分技术和热力学分析手段,对高铁铝土矿含碳球团在还原熔分过程中的渣相组成机理进行了研究。试验结果表明,渣系碱度对粒铁的收得率和粒铁尺寸以及渣系组成有重要影响。当碱度为1.00、2.00、3.85时,粒铁收得率分别为91.55%、44.53%和88.48%,粒铁尺寸分别为15.50、7.00 和8.54 mm;熔分渣的相组成（质量分数）分别为55%A-34%CA6-6%C2AS-4%Fe、64%A-35%C2AS-2%Fe、24%C2S-62%C12A7-7%C2AS-4%C3AS3-3%Fe;当渣系碱度为3.85时,还原熔分渣系的组成主要为C2S和C12A7,两者质量分数约为85%;只有当混合物处在C2S到C12A7的渣线上或者渣线附近时（即[R]=3.85时）,冷却析晶的平衡相中才会出现C2S和C12A7。     

Reduction and Carburization of Iron Oxide by Carbonaceous Materials

The iron nugget making process, where mixtures of iron ore powder and pulverized coal are made to heat rapidly, is regarded as a new ironmaking process. Since the iron carburization reaction is an especially important step from the viewpoint of energy saving in this process, the purpose of this study is to reveal the carburization mechanism of reduced iron formed during the heating process of the mixtures. Fe₂O₃ and H₂‐CO‐CO₂ gas mixture were made react with each other to simulate the formation of iron ore and the generation of coal gas from coal during the heating process. An electric resistance furnace was used to heat the samples. A cut surface of the quenched iron product was observed by microscopy. Carbon content in the iron was analyzed after reduction and carburization of Fe₂O₃. It is considered that there are many possibilities in the real process to carburize the reduced iron during the heating process, such as carburization with CO formed by coal combustion, solution loss reaction, and direct carburization with coal. It was observed in the present work that the carbon content in the reduced iron became the highest as Fe₃C was formed during the heating process. Therefore, it became clear that the key technology for production of pig iron containing high carbon was to control the formation of Fe₃C in the heating period of the mixture. The carburization mechanism was discussed in this study based on these experimental results.     

Cleanliness of Alloying Structural Steel

 Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel. It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production. For this purpose, cleanliness control in 02C-03Si-06Mn-1Cr-02Mo steel was investigated. Firstly, low melting temperature zone (≤1873 K) of CaO-Al2O3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation. On this basis, industrial tests were carried out. Through sampling at different stages, transformation of oxide inclusions and change of total oxygen content in steel were studied. The results show that: in order to form CaO-Al2O3-MgO system inclusions with low melting temperature, mass percent of Al2O3, MgO and CaO in inclusions should be controlled from 376% to 708%, 0 to 174% and 255% to 606%; For the condition of 1873 K and 005% (mass percent) dissolved aluminum in steel, the activities of dissolved oxygen, magnesium and calcium should be controlled as 0298×10-4-2×10-4, 01×10-5-40×10-5 and 08×10-8-180×10-8 respectively. With secondary refining proceeding, average total oxygen content and inclusion amount decrease, the type of most inclusions changes from Al2O3 after tapping to Al2O3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al2O3-MgO after RH treatment. In the final products, average total oxygen content was 127×10-6 and most inclusions were in spherical shape with size less than 5 μm.     

Investigation of Reduction and Smelting Mechanism in the Hi‐QIP Process

A new coal‐based reduction and smelting process for production of high quality iron pebbles in a rotary hearth furnace (Hi‐QIP Process) was developed. The reduction, carburization, smelting, and separating mechanism of the Hi‐QIP process were investigated. The experiments were carried out in a graphite heater furnace under rapidly heating up to 1773 K. A mixture of coal and ore produced molten metal and slag, which were held on the coal and did not come into contact with the refractory located under the coal layer. It is confirmed that the reduction of wettability between the iron and slag promotes the separation of them, when the content of FeO slag decreases. High productivity of the process is expected when using iron ore with small particle diameter and low gangue content. Favourable operating results were obtained in a pilot test using a rotary hearth furnace with a diameter of 7 m and a width of 1.5 m. This test demonstrated the possibility of continuous production of iron pebbles with high productivity (15t‐iron/d).     

Dephosphorisation of high phosphorus oolitic hematite by carbon composite pre-reduction and fast melting separation

High phosphorus oolitic hematite deposit is a kind of refractory iron ore resource of huge amount. At present, it is difficult to be utilised by traditional physical and chemical technology efficiently and economically. A novel process for utilisation of the high phosphorus oolitic hematite based on carbon composite pre-reduction and fast melting separation has been put forward in the paper. High grade pig iron nugget of low phosphorus could be obtained in the present research. The influence of experimental conditions, such as pre-reduction temperature, C/O (molar ratio) and basicity, on the dephosphorisation behaviours was studied in detail. The thermodynamic basis and reduction and melting separation process were also analysed. The phosphorus content in the iron nugget decreased with the increasing of basicity and increased with the increasing of C/O. The optimum parameters were pre-reduction temperature of 1200°C for 30?min, C/O of 0.95 and basicity of 1.7. After melting separation of molten iron and slag at 1400°C for 10?min, the iron nugget containing 0.02?wt-% [P] would be obtained. The dephosphorisation degree and iron yield in the form of iron nugget were 97.5% and 96.9% respectively. The iron nugget may be directly used as the raw materials of steelmaking from the view point of its high grade.     

Manipulation of slag separation properties from pig iron nuggets with flux additions to dried greenball mixture

Pig iron nugget process is one of the direct smelting processes developed as an alternative to the traditional blast furnace process. Throughout the process, slag-free pig iron nuggets, which have similar properties to the blast furnace pig iron and white cast iron, are produced by single-stage heat treatment of dried greenballs. During the process, slag separation from the metallized areas can be enhanced by adjustment of the slag’s chemical and physical properties. The objective of this research was to investigate the effects of flux addition rates (basic to acid ratio) to the dried greenball mixture on pig iron nugget production and slag separation. Thus, this study involved the heat treatment of six different greenball mixtures, which contained various amounts of limestone addition (basic to acid ratios, 0, 0.63, 1.02, 1.42, 1.85, and 2.29) utilizing a laboratory-scale resistance box furnace or simultaneous differential scanning calorimetry and thermalgravimetric analyzer. The samples produced by heating in the box furnace were analyzed for their morphological and chemical properties utilizing optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), macroscopic observations, iron titrations, and atomic absorption spectroscopy. It was determined that the highest percentage of iron yield in the nugget for the process and the highest distribution of iron in magnetic slag were obtained when utilizing the greenball mixture, which contained 7.5 wt% limestone as flux (basic to acid ratio of 1.42).     

富氧顶吹熔融还原冶炼高磷铁矿与钛铁矿配矿的试验研究

采用模拟HIsmelt的富氧顶吹熔融还原技术冶炼惠民高磷铁矿与勐桥钛铁矿配矿,在温度为1 500K,碱度为1.3,配碳比为1.0的条件下,恒温时间20min(在升温过程中,没有通入惰性气体),恒温过程中通入O2(流量250L/h、纯度为99%)10min。恒温时间结束后,调整氧气流量为5L/h,保持其氧化性气氛至冷却。研究了不同配矿比例对铁回收率、生铁中磷、硫含量以及磷、硫分配比的影响。研究结果表明,在惠民铁矿和勐桥精矿的比例为1∶1时,其冶炼结果比较理想:铁的回收率为95.1%,生铁中磷的质量分数约为0.32%,硫的质量分数为0.054%,钛的质量分数为0.031%。     

基于铁水成本的铁矿粉烧结经济价值评价方法

传统的铁矿粉烧结评价方法存在未考虑MgO、Al2O3脉石和酸性炉料的影响等缺点,本文提出了一种新的基于铁水成本的铁矿粉烧结经济价值评价方法,即在一定的炉渣二元碱度和镁铝比下,以单烧矿的铁水成本(元/t)作为铁矿粉烧结经济价值评价指标。其结果比以往的评价方法更准确可靠,能够反映铁矿粉烧结的经济效益。     

CaO B2O3对钢包精炼渣的调质处理

 为减少钢包合金化精炼浸渍罩粘渣,以质量比1∶1配制的CaO B2O3作调质剂对钢包顶渣调质,研究调质剂对渣熔化温度、粘度及脱硫能力的影响。半球法熔化温度测定结果表明,调质剂的助熔效果明显,当其加入量为10%时,渣熔化温度从调质前的1 439 ℃降至1 320 ℃。旋转柱体法粘度测试结果表明,调质剂能有效降低精炼处理后钢包顶渣的粘度。在1 500 ℃时,未调质的钢包顶渣粘度约为65 Pa·s,调质后渣的粘度低于20 Pa·s。调质处理后的钢包渣不会引起钢液的回硫,并可使钢中硫含量进一步降低。