电炉粉尘造泡沫渣过程中FeO的还原与炉渣发泡行为

在实验室研究了循环利用电炉粉尘造泡沫渣过程中,ＦｅＯ还原速度的影响因素,同时分析了ＦｅＯ还原速度与炉渣发泡高度的关第。结果表明,随着粉尘和煤粉加入量增加以及反应温度提高,渣中ＦｅＯ的还原速度加快;渣中ＦｅＯ被固体碳还原的反应为表观一级反应;渣中ＦｅＯ还原反应速率常数与泡沫渣的最大发泡高度存在很好的相关性,还原速度增加,泡沫渣的最大发泡高度也随之提高。     

固体碳还原熔融氧化铁的动力学

介绍了用体系的初、终态浓度,结合反应过程还原剂失重速度测定动力学参数的方法,测量了周体碳还原熔融PeO-CaO—SiO_2-MgO和FeO-CaO-SiO_2两种渣系中FeO的还原速度。结果表明,在本试验条件下测出的还原反应速度是总(FeO)重量百分浓度的表观一级反应,表观活化能为53.174kcal/mool。在本试验范围内,测得固体碳还原熔融氧化铁的经验速度方程式为: 还原反应的速度限制步骤是FeO热量向反应界面的对流扩散和气泡脱离石墨表面。发现添加少量碱金属氧化物能十分显著地加快碳还原熔融氧化铁的速度。     

高钛渣中FeO还原对Ti(C,N)生成的抑制作用

通过高钛渣中渣-焦、渣-铁反应的模拟试验表明,FeO还原率与反应时间几乎成直线关系,FeO含量越高,其反应开始时的还原速度就越大。渣-铁和渣-焦反应中FeO的还原规律基本相似,但前者还原速度比后者大。高钛渣中FeO含量到4％时可以抑制Ti(C,N)的大量生成.把提高滴落区炉料氧位和加强高炉下部(炉缸部分)的氧化性结合起来,可以达到高炉全钒钛矿冶炼的目的。     

炉渣中FeO还原的动力学实验研究

1 引言 随着对高炉内直接还原动力学研究的深入,通过碳还原渣中FeO已引起极大关注。在研究过程中,大多采用纯铁氧化物或简单渣系,这和实际情况有所不同。本实验模拟济钢高炉炉渣成分,按实际渣铁比配制碳饱和     

不锈钢粉尘碳热还原渣高效粉化分离

不锈钢粉尘是钢铁冶炼过程产生的典型二次固废，其含有大量的有价金属铁、铬和镍的氧化物，具有较高的回收利用价值。碳热还原法是一种高效冶炼金属矿物的火法工艺，使用碳热还原法处理不锈钢粉尘过程中，还原渣发生的粉化反应及冷却后的粉化效果会影响还原渣体系的理化性能，影响还原产物渣和金属的分离效果。通过高温试验研究了粉化控制过程工艺参数保温温度、保温时间和降温速率对还原渣粉化效果的影响。试验结果表明，不锈钢粉尘碳热还原-粉化控制后获得的还原渣自粉化率及自粉化渣的质量分数随着保温温度的升高呈现先增加后降低的趋势；还原渣自粉化率及自粉化渣的质量分数随着保温时间的增加呈现逐渐增长的趋势；还原渣自粉化率及自粉化渣的质量分数随着降温速率的降低呈现逐渐增长的趋势。在还原温度为1 450℃、升温速率为10℃/min、还原时间为20 min、碳氧比为0.8、控制保温温度为1 100℃、保温时间为15 min、降温速率为15℃/min的条件下，还原渣的自粉化率达到95.26%,自粉化渣的质量分数达到91.36%。在不锈钢粉尘碳热还原的过程中，还原渣中Ca₂SiO₄的生成反应...     

钒钛磁铁矿二步法熔融还原试验研究

与传统高炉流程冶炼钒钛磁铁矿相比,采用二步法熔融还原工艺有利于回收钒钛磁铁矿中的铁、钒和钛等有价元素。本研究分别在990℃、1200℃、1500℃下进行气体预还原、配碳预还原和熔融还原试验,结果表明：熔融还原的渣铁分离效果良好且铁损较低,铁水钒含量高于高炉流程铁水,钛渣品位可以达到或超过理论品位。攀枝花精矿二步法熔融还原适宜预氧化后采用固体碳预还原,其还原温度应等于或高于1200℃;熔态终还原时可不配碳,终还原应控制钛还原度、（FeO）含量在适宜的范围内。     

不锈钢粉尘含碳球团还原机理的探讨

为研究不锈钢粉尘含碳球团的还原机理,比较了含碳球团熔化速度和其中金属还原速度的相对大小,结果表明球团的还原速率大于熔化速率,渣对还原和熔化速度都有促进作用,含碳球团在AOD炉的第一个还原阶段末期加入时,金属的还原率最高。通过分析碳在渣和钢液间的迁移规律确定了碳有向渣中迁移的趋势;并估算了渣的粘度约为0.254Pa.s,渣钢间界面张力约为490mN/m。     

高炉瓦斯泥压块循环应用于电炉泡沫渣的研究

对高炉瓦斯泥应用于电炉造泡沫渣进行了实验室试验和现场试验研究.确定了冷压块工艺和现场应用工艺.试验结果表明:瓦斯泥的压块可以起到强化泡沫渣生成的作用,但瓦斯泥压块的加入量有个合适的范围.压块加入后,压块中的铁和碳通过反应参与了泡沫渣的生成;压块中的锌和铅被快速还原,进入二次粉尘.瓦斯泥压块加入电炉,对钢水和渣没有产生可觉察的影响.在此过程中,压块中的有价资源得到了循环利用.     

预还原球团在铁碳熔体中熔融还原传质规律的研究

本文对不同预还原度的铁矿球团在铁碳溶体中溶融还原的规律进行了实验和理论研究，针对熔还原反应特点，提出了表观FeO浓度概念，根据传质理论和球团矿熔融还原的特性，建立了支映球团矿在铁碳熔体中熔融还原反应规律的双相传质模型，实验和理论计算结果表明，球团预还原度和熔化速度等因素对熔融速率影响较大。     

高炉喷吹煤气对成渣过程的影响

向高炉喷吹富氢煤气代替喷煤对高炉成渣过程产生重要的影响.对喷吹煤气后高炉的成渣过程进行了模拟研究,结果表明:FeO的含量决定了初渣的性能.在炉腹区域,氢气具有很强的还原能力,渣中FeO含量迅速减少,但同时炉渣成分快速接近终渣成分,使炉腹渣仍具有较好的熔化性和流动性.由于没有未燃煤粉和煤粉灰分的加入,初渣到终渣的成分变化较小,改善了喷煤气高炉的成渣过程.     

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.     

The effect of carbon content on the rate of reduction of FeO in slag relevant to iron smelting

In the iron smelting, or bath smelting, process the tapped metal contains high amounts of sulfur and the slag contains high amounts of FeO, relative to blast furnace slag. After tapping, the FeO can be further reduced by carbon in the metal, which will also lead to better desulfurization. Although there have been many studies of the reaction of carbon in iron with FeO in slag, discrepancies exist with regards to the effect of carbon in iron on the rate of FeO reduction in slag, which is the subject of this study. Experiments were conducted at 1723 K, using a slag with basicity close to one with an FeO mass content of 5 %. The rate of reduction was measured using a pressure increase technique. For moderate and high sulfur contents, as in the case of iron smelting, the rate is primarily controlled by the dissociation of CO₂ on the surface of the molten iron. Furthermore, if the effect of carbon on sulfur is taken into account, for the range of carbon mass contents of 2 to 4.5 %, there is no effect of the carbon level on the rate of FeO reduction. At low sulfur contents it was found that there is considerable slag foaming, which inhibits mass transfer of FeO in the slag, and significantly reduces the rate. Even when there is no slag foaming at low sulfur contents, mass transfer of FeO in the slag can influence the rate of FeO reduction.     

Mathematical Modelling and Experimental Investigation of Coke Reduction of FeO in Slag

Mathematic model development and experimental investigations were carried out for the reduction of FeO in slag by coke. Rate expressions for the reduction limited by the different steps and through different reaction routes were proposed. In the experimental investigation, the FeO reduction was found to be a first order and irreversible reaction; the reduction rate increased with increasing temperature and the FeO content in slag, and decreased with increasing ash content in the coke. Low CO₂/CO ratio in the product gas and preferential reduction of FeO over SiO₂ in slag were observed in the reaction system. The proposed reaction mechanisms were discussed with the observed kinetic phenomena. The reduction of FeO in slag by coke was found most likely to be jointly dominated by the mass transfer of FeO in slag and the chemical reactions at slag‐coke, slag‐gas or slag‐metal interfaces.     

A study of the reduction rate of FeO in slag by solid carbon

The reduction reaction of FeO in slag by carbon plays an important role in bath smelting reduction processes. In this study, the rate of this reaction was measured to understand the kinetic behavior of FeO reduction in slag by using the mass spectrometer technique. The present experimental results implied that the rate-determining step would change from the mass transfer of FeO at a low FeO content (<5 wt pct) to the chemical reaction at the gas/carbon interface at a high FeO content (>30 wt pct), while the total reduction rate would increase with an increasing FeO content in the slag. Based on the results of this study and comparisons with thermodynamical data for FeO in slag, the reduction rate of FeO can be expressed by the following equation:

利用冶金尘泥直接还原的试验研究

用高炉瓦斯灰和转炉污泥进行了直接还原试验研究.采用ICP、SEM - EDS对高炉瓦斯灰和转炉污泥进行物性分析表明,高炉瓦斯灰中铁元素以高价铁氧化物的形式存在,碳含量高(27.32％)、颗粒大;转炉污泥中铁元素以金属Fe和浮氏体形式存在,且浮氏体以细小状颗粒均匀弥散分布于其它物相中,两者均含有少量有害Zn元素.直接还原试验结果表明,随还原温度提高及还原时间延长,直接还原球团的全铁含量、脱锌率均增大.在C/O=1.0,还原温度1 220℃以上,还原时间30 min以上时,还原球团的全铁含量均大于71％,锌含量均小于0.05％,脱锌率大于85％.     

非晶态高炉渣的非等温析晶动力学研究

 采用差示扫描量热法(DSC)对非晶态高炉渣的析晶过程进行研究,得出不同升温速率下非晶态高炉渣析晶过程的DSC曲线,并根据动态DSC曲线用Kissinger法求出了析晶反应的活化能、反应级数及动力学方程中的指前因子等参数,建立了非晶态高炉渣析晶反应动力学的数学模型。实验所用非晶态高炉渣的析晶反应活化能为376.466 kJ/mol,该反应为一级反应。非晶态高炉渣的DSC曲线在1130~1310 K的温度区间内呈现出单一的晶化放热峰,峰顶温度、析晶温度和反应级数随升温速率的提高而提高。     

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.     

Reaction mechanism of FeO reduction by solid and dissolved carbon

The reduction reactions of FeO by carbon have been studied in order to be able to understand the fundamental phenomena occurring in smelting reduction process. The reduction of pure FeO by solid carbon proceeds mostly according to the same reaction mechanism as that by dissolved carbon in iron, the rate of which was experimentally determined to be controlled by the interfacial chemical reaction between Fe-C melt and intermediate CO₂ gas. Hence, the reduction rate of pure FeO by solid carbon is also chemically controlled by the Boudouard reaction between the dissolved carbon and CO₂ at the interface of by-product Fe droplet/gas phase, the activation energy of which was found to be about 193.2 kJ/mol. In addition, the reduction reaction of FeO in CaO-SiO₂-Al₂O₃-FeO slags by the dissolved carbon in Fe melt was also investigated over the FeO mass content less than 20 %. The reduction rate shows first order dependence with respect to FeO concentration. The surface active sulphur content in iron does not affect the reduction rate, and the temperature dependence of reduction rate gives the activation energy of 24.78 kJ/mol. Therefore, the reduction rate of FeO in slags by the dissolved carbon can be safely mentioned to be controlled by the liquid phase mass transfer of FeO through the slag phase diffusion-resistant boundary layer over the limited FeO concentration range. The empirical expression for the mass transfer controlled reactioe, deren Aktivierungsenergie ca. 193.2 kJ/mol beträgt. Außerdem wurde die Reduktion von FeO in CaO-SiO₂-Al₂O₃-FeO-Schlacken mit dem in der Eisenschmelze gelöstem Kohlenstoff fär FeO-Massengehalte von weniger als 20% untersucht. Die Reduktionsgeschwindigkeit weist hinsichtlich der FeO-Konzentration eine Abhängigkeit 1. Ordnung auf. Der Anteil an oberflächenaktivemn rate was determined as r = 5.94(±0.07).10^?6.exp(-24780/RT).(%FeOP)^0.96 over the reaction conditions employed.     

Kinetics of simultaneous reactions between liquid iron-carbon alloys and slags containing MnO

The oxidation rates of carbon, phosphorus, and silicon; the desulfurization rate of liquid iron; and the simultaneous reduction rate of MnO from slag were examined at 1450 °C to 1550 °C by using high carbon iron alloys and CaO-SiO₂-CaF₂ slags containing MnO and FeO. The reaction rates were well reproduced by a kinetic model describing the reaction between the slag and multicomponent iron alloys. The controlling steps applied for the reactions considered in the present kinetic simulation were as follows. The rate of decarburization is controlled by the chemical reaction at the slag-metal interface, and those of the other reactions are controlled by the transport in slag and metal phases. Both observation and simulation results showed that MnO was not a strong oxidizer compared with FeO in the slag, but was an effective component for desulfurization. The simulation results also showed that the interfacial oxygen activity using MnO-based slag was much lower than that using FeO-based slag. The apparent equilibrium constants of phosphorus and sulfur, which were obtained by the kinetic modeling of experimental results, were found to increase with increasing the (MnO + CaO)/SiO₂ ratio of the slag. The controlling step(s) of each element transport across the slag-metal interface was discussed with the aid of the kinetic model.     

Foaming and the Rate of the Carbon-Iron Oxide Reaction in Slag

Foaming in the electric arc furnace is achieved by injecting carbon into slag, where the resulting reaction of the carbon with FeO dissolved in the slag generates gas (CO) that causes the slag to foam. In this research, the rate of the reaction of FeO in slag with carbon and the resulting foam height were measured. In these experiments, the FeO content of the slag ranged from 15 to 45 mass pct, and several different types of carbon were used including graphite, coals, and chars. The rate of the slag-carbon reaction and the consequent CO generation increased with FeO content of the slag from 15 to 45 mass pct. However, the slag foam height reached a maximum at about 25 mass pct FeO and decreased at higher FeO contents. The decrease in foaming is apparently due to a decrease in the foam index or foamability caused by a decrease in viscosity and an increase in density of the slag with FeO content. The results of this work indicate that the foam height is influenced more significantly by the decrease in the foam index compared to the increase in the CO gas generation rate at higher FeO contents. The decrease in the foam index with FeO agrees with that predicted from the slag properties.