Study on Foaming Behaviour of Molten Slag during Smelting Reduction with Iron Bath

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Reduction Behaviour of BOF type Slags by Solid Carbon

Experiments were carried out on a system with artificially prepared slags in a graphite crucible, in order to examine the possibility of recycling BOF slags produced in the steelmaking process. More than 80% of FeO and P₂O₅ was reduced within 20 minutes and the FeO reduction rate was greater than that of P₂O₅. P₂O₅ reduction began after more than 60% of FeO was reduced. Increasing slag basicity enhanced the reduction of FeO and P₂O₅. Temperature also improved slag reduction. The overall reduction rate was controlled by the chemical reaction at the slag/carbon interface. The reduction rates of FeO and P₂O₅ were second and first order with respect to their respective contents. Most of the reduced phosphorus is believed to vaporize in the form of P₂ gas.     

Reduction Behaviour of BOF Slags by Carbon in Iron

Experiments were carried out in a system with BOF slags from industrial operations in order to optimize the conditions of recycling BOF slags produced in the steelmaking process. Reduction reactions of FeO and P₂O₅ proceeded steadily and the FeO reduction rate was almost identical to that of P₂O₅. The reduction reaction of FeO and P₂O₅ in BOF slag at the slag/gas interface is the rate‐controlling step. The reaction rates of FeO and P₂O₅ by dissolved carbon in molten iron are of first order with respect to their respective concentrations. The reduction reactions of FeO and P₂O₅ by dissolved carbon in iron are much closer to the equilibrium state compared with the reduction by solid carbon. It is necessary to control the portion of phosphorus vaporization during reduction treatment in order to obtain efficient operational conditions for BOF slag reduction.     

铜还原钼酸盐实验研究

基于钨钼的电化学性质差异,以铜为还原剂,在添加EDTA络合剂和无络合剂作用的条件下,研究了EDTA用量、pH值、还原时间、反应温度对钼还原率的影响。结果表明,添加EDTA络合剂不利于钼还原率的提高;反应可采用铜直接还原,选择pH=1.0～1.5、反应温度60℃及延长还原时间,利于钼还原率的提高。     

Y2O3与MgO复合掺杂ZrO2材料的电性能研究

利用交流复阻抗分析技术对Y2O3与 MgO复合掺杂ZrO2材料的电性能进行了研究.发现随着Y2O3掺入量的增加,参与跃迁的氧空位增多,并促进烧结体的密度提高,气孔率降低,使得晶粒边界的电阻减少,导致(ZrO2)1-x-y(YO1.5)x(MgO)y陶瓷电导率增大.烧结温度的提高也是增加 (ZrO2 )1-x-y(YO1.5)x(MgO)y陶瓷电导率的重要因素之一.     

Reduction of Fine Ores in Argon‐Hydrogen Plasma

The steel industry is a major source of global CO₂ emission. Larger reductions of greenhouse gases are the challenge to develop new processes, like Hydrogen Plasma Smelting Reduction (HPSR). The present paper shows physical and chemical fundamentals for the reduction of iron oxides with hydrogen plasma. The behaviour of different hematite iron ores during melting and reduction with hydrogen plasma were investigated with thermogravimetry and a laboratory plasma furnace. The path of iron oxides during smelting and reduction in the Fe‐O phase diagram are described. Reduction tests in the laboratory furnace show the possibility to reduce hematite iron ores with hydrogen plasma in a short time with high utilization degrees without direct CO₂ emissions.     

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).     

Reduction swelling behaviour of haematite/magnetite agglomerates with addition of MgO and CaO

Abstract

The influence of three kinds of CaO and MgO additives (dolomite, burnt lime and serpentine) on the reduction swelling behaviour of haematite–magnetite (H–M) concentrates pellets was studied. Burnt lime and dolomite increased the reduction swelling index of H–M oxidised pellets, while the reduction swelling index was able to be reduced when serpentine was added. CaO accelerated the formation and growth of metallic iron whiskers and led to abnormal swelling of the magnetite briquettes, while MgO was able to be dissolved in wüstite and reduced the migration rate of Fe²⁺; therefore, there was no catastrophic swelling in either the haematite or magnetite briquettes. As far as H–M concentrate pellets were concerned, because the solubility of CaO in magnetite was greater than that in the primary haematite and the secondary haematite generated from magnetite during the oxidation was easy to be reduced to wüstite, there was abnormal swelling in the reduced H–M pellets with CaO addition.     

铈或钕掺杂TiO2光催化陶瓷及其自洁净抗菌性能研究

采用溶胶-凝胶法和浸渍提拉法在陶瓷表面覆盖了Ce或Nd掺杂的TiO2薄膜.稀土掺杂量为Ce/TiO2=0.007,Nd/TiO2=0.003(摩尔比)时,铈或钕掺杂TiO2光催化陶瓷分别对甲基橙的降解率最大.稀土掺杂TiO2光催化陶瓷对大肠杆菌的抗菌率高达99%,较纯TiO2光催化陶瓷的91%更高.     

Plasma Reduction of Iron Oxide by Methane Gas and its Process Up‐scaling

This paper investigates the characteristics of the methane plasma reduction of iron ore in comparison to that of the hydrogen plasma reduction process. Although hydrogen plasma smelting reduction (HPSR) has potential advantages as a steelmaking alternative in terms of simplicity (less operation units) and less harmful detrimental environmental implications, its high cost has a negative influence on its usage. In this regard, natural gas (> 96 % methane) could be adopted in the field of plasma smelting reduction. A brief comparison between hydrogen and methane options has been carried out experimentally. Heat and mass balance models were conducted to explore the features of up‐scaled processes with respect to consumption figures and CO₂ emissions. It was found that the methane plasma is a good alternative iron oxide smelting process.     

Effect of CaCO3 on the Gaseous Reduction of Tin Oxide Under CO-CO2 Atmosphere

Calcite (CaCO₃), one of the main impurities, has an uncertain effect on the volatilization behavior of tin oxide in the tin-bearing iron ore concentrates during the selective reduction volatilization process. In this study, natural calcite powders were added into the tin-bearing iron ore concentrates to investigate tin volatilization behavior affected by CaCO₃ under different roasting temperature, CO content, and roasting time. In addition, the effect of CaCO₃ on the phase transformation of SnO₂ was determined using XRD, SEM-EDS combined with thermodynamics calculation. The results indicated that CaCO₃ had a significantly adverse effect on the Sn volatilization ratio, because Ca₂SnO₄ was easily formed under CO-CO₂ atmosphere. It was also found from the study that the generation of SnO_(s) was the most critical intermediate for promoting the formation of Ca₂SnO₄.     

150 kA预焙铝电解槽生产稀土铝中间合金生产实践

本文介绍了150 kA预焙铝电解槽生产稀土铝中间合金的工业实践.通过多年的生产表明,在铝电解槽添加碳酸稀土用熔盐电解法生产稀土铝中间合金,在实际生产中是切实可行的,所生产合金能满足后序生产需要,并且此方法有利于电解槽电流效率的提高.     

Kinetics of Reduction of MnO in Molten Slag with Carbon Undersaturated Liquid Iron

The reduction of MnO in molten slag with carbon undersaturated iron was studied. It was found that the process is affected by the carbon content of molten metal and the temperature. The higher the carbon content and the temperature, the faster both the reduction and the emerging of the hump on curve of ωFeO, the larger the difference betwe en ωFeO, max and ωFeO, e. The phenomena were explained with three-step reaction model.     

铁浴式熔融还原型熔体的性质

研究了铁浴式熔融还原型熔体的组成与性质的关系，测试了熔体对耐火材料的浸润性，分析了熔体中ＦｅＯ浓度，熔体温度，耐火材料的组成及结构，耐火材料中石墨碳含量等对熔体与耐火材料间浸润性的影响，同时测试了熔体组成与流动性的关系，熔体中ＦｅＯ浓度，熔渣碱度对熔体的熔化温度的影响，测定和分析了熔体组成与粘度变化的关系，结果表明，熔中ＦｅＯ浓度是影响熔体性质的最关键因素，ＦｅＯ浓度提高，熔体对耐火材料的润湿能力     

Study on the Design of the Soft Reduction Unit of High‐Speed Billet Casters

The production of continuously cast products that display very low centre segregation and thus more homogeneous properties is an important objective, particularly for high‐speed continuous casting of billets, in meeting increasingly stringent quality requirements. In addition to the well known methods of reducing macro‐segregation in continuous casting, inline deformation of the partially solidified strand, already used successfully in slab and bloom casting, offers an alternative for producing material with low segregation level. The present report considers the feasibility and effectiveness of mechanical soft reduction for the continuous casting of billets. The structural design of the soft reduction unit as a stand or segmental construction was investigated, as well as the influence of varying roll diameters. A strand of the existing billet caster S4 was modified for this purpose and soft reduction tests were conducted on spring steel grade 54SiCr6 at casting speeds between 3.30 and 3.60 m/min. The conclusions drawn from the test results as regards roll diameter, required reduction rate and necessary reduction force formed the basis for designing the soft reduction unit of the new billet caster SO that went in operation in March 2004.     

H_2-CO混合气体还原氧化亚铁粉体的动力学

通过热重实验获得了873、973和1173 K三个温度条件下不同组成的H_2-CO混合气体还原氧化亚铁的动力学曲线,发现在873和973 K时由于析碳反应的发生,动力学曲线较为混乱,没有规律,而在1 173 K时,还原曲线则随还原气体中H_2含量(体积分数)的增加表现出明显的规律性.通过H_2-CO与H_2-Ar气体还原氧化亚铁动力学的比较,混合气体中CO参与反应的速率与其含量(体积分数)基本符合线性关系.还原产物形貌观察的结果表明,随着反应温度的升高,还原产物孔隙增大,铁相充分发育长大并逐渐有明显的烧结现象.     

熔融还原法冶炼高速钢

对用白钨矿、氧化钼和钒渣冶炼高速钢进行了热力学和动力学的计算与分析。在熔融还原过程中，CaWO4、MoO3、V2O5将被C、CaC2、Si-Fe、SiC还原。反应过程包括：固一固反应、液一固反应、铁浴反应和液一液反应。开发了低温快速还原、控制渣量、抑制沸腾等技术。还原WO3的限制性环节是WO3在熔渣中的扩散，改善渣的流动性，扩大反应界面能加快WO3的还原；使用阻尼剂能有效抑制钼的挥发。用20t的AC电弧炉还原氧化钨矿工业化生产高速钢M-2已取得成功，具有质量高、缩短工序、节约资源、降低能耗、提高成品率和改善环境等优点。综合上述功效，生产每吨M-2钢可节约成本1780元。应用这一新技术，重庆特钢公司累计生产M-2钢7981t。     

海绵铋中频炉还原熔炼

采用中频感应熔炼炉还原熔炼处理海绵铋，渣量少，熔炼温度较低，炉渣的熔点和粘度均能满足要求，铋回收率95％一99％。     

高磷稀土精矿的碳热还原过程研究

采用63kVA直流矿热炉,对高磷稀土精矿直接进行碳热还原,制备高品位稀土硅化物合金。冶炼过程中生成的废渣很少,炉底不上涨,炉内碳热还原反应进行得较为彻底,稀土几乎全部进入产品合金当中。同时,对稀土精矿中的主要有害杂质磷在冶炼过程中及在矿热炉内的行为进行了深入的研究,提出了最大限度减少磷进入产品合金的策略。实验得到的稀土硅化物合金具有独特的组织结构,与众不同的抗水化性,其粉化特性也与传统观点有较大的差异。