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Burak Birol Muhlis Nezihi Saridede 《Mineral Processing and Extractive Metallurgy Review》2013,34(4):195-201
Composite pellets which contain a reducing agent and are produced only by cold bonding process are improved instead of traditionally hardened pellets by sintering. The new ironmaking technologies that are able to utilize these pellets have been developed from pilot plant to commercial scale. Iron nuggets which have a similar composition to pig iron can be produced by using composite pellets at high temperatures (1350–1400°C) and in a short reduction time (15–20 min) by smelting reduction process. In this study, the effect of reduction parameters and basicity of composite pellets on the reduction properties and product quality are investigated. Composite pellets containing magnetite concentrate with a reducing agent (coke) and a flux are processed at different temperature and at times by smelting reduction process. The increasing temperature and time has a positive effect on reduction and melting of the pellets. Excessive carbon prevents the metal droplets from coalescing. The iron nugget that is produced from the sample with the basicity (CaO/SiO2) of 0.68 has the optimal physical and chemical properties. It is also determined that a decrease or increase of basicity has a negative effect on the properties of the iron nuggets. 相似文献
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Mass loss and direct reduction characteristics of iron ore-coal composite pellets under different technological parameters were investigated. Meanwhile, changes of iron phase at different temperatures were analyzed by using X-ray diffraction (XRD), and characteristics of crushed products were studied by using a scanning electron microscope (SEM). The results showed that heating rate had little influence on the reduction, but the temperature played an important role in the reduction process. The mass loss rate increased rapidly from 800 to 1 100 ℃. The reduction process can be divided into three steps which correspond to different temperature ranges. Fe2 03 began to transform into Fe304 below 500 ℃, and FeO was reduced into Fe from 900 ℃. At 900 ℃, the reduction product showed a clear porous structure, which promoted the reduction progress. At 1000 ℃, the metallic Fe dominated the sample, and the reduction reached a very high degree. 相似文献
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Ironorecoalmixedpelletsarecapableofquicklyself reduction .Intheyearsofsixties ,theInmetcoprocessandMidrexFastmetprocessformakingcoalmixedpelletstodealwiththesecondarydustinironandsteelplantortoproduceDRI[1- 3] weredevel oped .Recently ,alotofbasicresearcheso… 相似文献
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针对气固直接还原工艺中存在着气体利用率低和还原供热不足等问题,利用恒温热重分析(TG)法,研究了氢/碳比率对白云鄂博铁精矿还原速度的影响。结果表明,在还原试验开始后40 min内,还原速率随wH2/wCO比增加而增大,使得Fe2O3→Fe3O4反应时间缩短。基于气相内扩散和界面反应的球团还原速度方程均能较好地处理本研究的数据,得到了反应速度常数与wH2/wCO的关系为:k界面=-0.1975+0.3 575wH2/wCO,k扩散=0.171 01+0.269 7wH2/wCO。根据Arrhenius方程计算出界面反应和气相内扩散活化能分别为26 k J/mol和44 k J/mol,因此本研究条件下限制性环节为气体内扩散控制。 相似文献
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In this paper, a new kinetic model has been developed for reduction of metal oxides with hydrogen under both isothermal and non‐isothermal conditions. This model describes the kinetics of single reductive reaction and double reductive reactions by considering the diffusion and chemical reaction controlling mechanisms. In particular, the model is in the analytic form of expressing the reduction extent as an explicit function of time, temperature, radius of the particle, and hydrogen partial pressure, which is convenient for using and theoretical analysis. The reduction kinetics of nickel oxide, natural ilmenite, and Fe2MoO4 agree well with the theoretical results by the present model. 相似文献
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煤种对含煤球团还原速度的影响 总被引:6,自引:1,他引:5
研究了在1223 ̄1473K的氮气氛中3种不同挥发分煤粉的粒度、铁精矿粉粒度、温度及碳-氧摩尔比对含煤球团还原速度的影响。发现降低煤粉或铁精矿粉粒度,提高温度或碳-氧摩尔比可提高含煤球团的还原速度,且这4种因素对还原速度的影响程度随煤种挥发分的降低而增大。分别采用以碳气化反应、气相内扩散、界面反应为控制环节而得出的表达含煤球团反应过程的速度方程处理本研究数据,发现3种速度方程(4种表达形式)均能较 相似文献
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Oleksandr Kovtun Mykyta Levchenko Erik Oldinski Martin Gräbner Olena Volkova 《国际钢铁研究》2023,94(10):2300140
The need to develop green steelmaking techniques has led to the replacement of reducing agents such as CO with H2. H2 and N2/H2 mixtures can be used for the carbothermal reduction of iron ore. Herein, the reduction swelling index (RSI) of iron ore pellets in a forming gas (N2/H2) atmosphere at temperatures of 700–1000 °C is investigated and it is compared with that in pure H2. It is showed in the experimental results that the RSI increases with increasing temperature for both the H2 and N2/H2 atmospheres. The maximum swelling is reached approximately 5 min into the H2 reduction process, while in the N2/H2 atmosphere, it is reached after 25–45 min of reduction, depending on the temperature. When the reduction temperature exceeds 900 °C, the RSI is greater than 20%. Scanning electron microscopy/energy-dispersive X-ray spectroscopy is performed to detect the changes in the microstructure and chemical composition of the samples. The nonreduced areas in the reduced pellets during the N2/H2 reduction process are analyzed using light optical microscopy. 相似文献
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Thecarbongasificationhasagreateffectonre ductionbehaviorofironorepelletscontainingcarbon ,especiallyinneutralatmosphere .Generalspeaking ,addinganyadditives ,whichcanpromotecarbongasi ficationreaction ,canenhancethereductionrateofironorepelletscontainingca… 相似文献
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搜集并评估了氢气还原铁氧化物反应的表观活化能。分析了反应动力学条件与反应机理和表观活化能的关系。得出:气体内扩散控速和铁离子固态扩散控速时,还原过程的表观活化能分别为8.0~28.0 kJ/m ol和> 90 kJ/m ol;界面化学反应控速时,将Fe2O3,Fe3O4 和‘FeO’还原为Fe的表观活化能分别为40.0~70.0 kJ/m ol,55.0~65.0 kJ/m ol和42.0~52.0 kJ/m ol;两个环节混合控速时,表观活化能介于每个环节单独控速的表观活化能范围之间。 相似文献
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During hot rolling process metals will inevitably oxidize because of high temperature and air condition.In order to guarantee the surface quality,acid pickling is applied to remove the oxide scale while waste acid will do harm to the environment.Faced with the problem,by means of reduction process of hot-rolled plates,the oxide scale will be reduced to iron,so that acid pickling is unnecessary.One pass cold rolling procedure was applied.The compression ratios of hot-rolled plates with oxide scale were 10%,18%,26%and 31%,respectively.After that,samples mentioned above including a sample without deformation were separately reduced under hydrogen atmosphere condition(5% H2 +95% Ar in volume percent)at 600-1 000℃.The thermal gravimetric apparatus(TGA)was used to establish accurate experimental condition and obtain complete mass loss data.Field emission electron probe microanalysis(EPMA)was applied to analyze scale morphology change and composition distribution through the oxide scale.It was found that the sample with 26%compression ratio could be reduced completely at 900℃ which was favorable to galvanization. 相似文献
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Large amounts of fines and superfines are generated in Indian iron ore and coal mines due to mechanized mining and mineral dressing operations. Utilization of these fines for extracting metal is of vital concern for resource utilization and pollution control. For agglomeration of these fines, a suitable binder is required. Iron ore-coal composite pellets were prepared by cold bonding. Various binders such as lime, Ca(OH)2, slaked lime, dextrose, molasses, and sodium polyacrylate (SPA), alone or in combination, were employed for making composite briquettes. The slaked lime–dextrose combination produced the highest strength among the various binders employed for producing composite briquettes and was therefore selected for producing composite pellets for the smelting reduction. In cold bonding, the composite pellets attain the requisite properties due to physico-chemical changes of the binder in ambient conditions. It was possible to obtain a dry strength of more than 300 N per pellet in some cases and more than 200 N per pellet in many trials. Drop strength and shatter index values of composite pellets were also measured. In the present paper an attempt has been made to evaluate the mechanical properties of cold-bonded composite pellets so as to throw some light on the capacity of these pellets to withstand stresses during handling and transportation. 相似文献