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1.
K S Abdel Halim 《钢铁研究学报(英文版)》2013,20(9):40-46
The operation of blast furnace using natural gas and oxygen enriched blast (composite blast technology) is considered in many countries to be standard operation for a modern blast furnace particularly in certain countries with cheap and stable supply of natural gas. The theoretical flame temperature (TFT) of combustion and the degree of direct reduction of iron oxides (rd) arc considered as the main controlling parameters of composite blast technology. The calculated values of these parameters are mainly dependent on the amount of air blast consumption. This amount of air blast is measured before entering into blast stoves. Actually, some of air blast is lost through valves of air stoves. Consequently, the real volume of air blast in the furnace is less than the recorded value by amounts of 5% ? 15% which is not considered in the estimation of rd and TFT. The purpose is to analyze the different methods for estimation of air blast inside the blast furnaces and develop a theoretical model to calculate air blast consumption with high accuracy. Based on the calculation of air blast consumption, a complete roadmap is demonstrated to change the operation regime parameters of blast furnaces working on composite blast technology. 相似文献
2.
Mohamed Bahgat Khaled S. Abdel Halim Mahmoud I. Nasr Abdel Hady A. El‐Geassy 《国际钢铁研究》2007,78(6):443-450
Compacts made from pure wüstite and compacts doped with 2% MgO were annealed at 1000°C for 3 hrs in 50%CO‐CO2 gas mixtures. The annealed samples were isothermally reduced at 800‐1100°C in H2 gas. Selected samples were isothermally reduced at 1000°C with pure CO and 50%H2‐CO gas mixture to investigate the effect of gas composition on the reduction processes. The oxygen weight loss resulting from the reduction of the samples was recorded as a function of time. X‐ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy and porosity measurements were used to characterize the annealed and reduced samples. Magnesio‐wüstite (MgO·FeO) phase was formed during the annealing of MgO doped wüstite. The MgO·FeO in turn decreased the porosity of the annealed doped samples compared to pure wüstite compacts. The influence of temperature, gas composition and MgO content on the reduction behaviour and the morphology of the annealed samples was investigated. The values of the apparent activation energy were calculated from Arrhenius plots and correlated with the reduction mechanism. The reduction rate increased with reaction temperature. In doped compacts, the MgO·FeO phase was not completely reduced both at lower reduction temperature (800°C) and during reduction with pure CO. From the activation energy values, the initial reaction stage was controlled by the combined effect of chemical reaction and gas diffusion while solid state diffusion controlled the final stage of reduction. Morphologically, metallic iron was formed in different shape structures under the effect of MgO addition and reduction conditions. 相似文献
3.
《钢铁冶炼》2013,40(8):631-640
AbstractThe effect of basicity on the metallic iron whisker growth during wüstite reduction was studied in the present investigation. Compacts of pure and CaO/SiO2 doped wüstite were synthesised. The annealed compacts were isothermally reduced in thermogravimetric apparatus with CO gas at 800–1100°C. The course of reduction was followed by measuring the weight loss as a function of time. X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope and porosity measurements were used to characterise the annealed and reduced samples. The influence of temperature and basicity (CaO/SiO2) on the reduction behaviour and the morphology of the annealed samples were investigated. The reduction rate increased with temperature but decreased by increasing basicity value. Metallic iron whisker shape structure was detected in the pure wüstite samples after reduction at high temperatures while in basic wüstite samples, whiskers were formed at the surface of the compacts. From the activation energy values, the reduction of pure wüstite is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. The reduction of basic wüstite compacts with 0·2 and 0·5 basicity ratios are most likely controlled by chemical reaction mechanism while for 0·8 basicity ratio, the reduction rate is most likely controlled by solid state reaction mechanism. 相似文献
4.
Hongsheng Chen Zhong Zheng Zhiwei Chen Wenzhou Yu Junrong Yue 《Metallurgical and Materials Transactions B》2017,48(2):841-852
The reduction kinetics of Brazilian hematite by CO is investigated in a Micro Fluidized Bed Reaction Analyzer (MFBRA) using an analyzing method based on Johnson-Mehl-Avrami (JMA) model at temperatures of 973 K (700 °C), 1023 K (750 °C), 1073 K (800 °C), and 1123 K (850 °C). The solid products at different reduction stages are evaluated by SEM/EDS and XRD technologies. Results indicate that the reduction process is better to be discussed in terms of a parallel reaction model that consists of the reactions of hematite to wüstite and wüstite to iron, rather than a stepwise route. Meanwhile, the controlling mechanism of the reduction process is found to vary with temperature and the degree of conversion. The overall process is controlled by the gas–solid reaction occurring at the iron/wüstite interface in the initial stages, and then is limited by the nucleation of wüstite, and finally shifts to diffusion control. Moreover, the reactions of hematite to wüstite and wüstite to iron take place simultaneously but with different time dependences, and the apparent activation energies of hematite to wüstite and wüstite to iron are determined as 83.61 and 80.40 KJ/mol, respectively. 相似文献
5.
G. J. W. Kor 《Metallurgical and Materials Transactions B》1972,3(9):2343-2347
The solubility of sulfur in wüstite in equilibrium with γ iron and liquid oxysulfide was found to be 0.011 wt pct at 1050°C.
The sulfur solubility in γ iron in equilibrium with wüstite and liquid oxysulfide was also determined at 1050°, 1150°, and
1250°C and found to be 135, 165, and 160 ppm respectively. These values are considerably lower than the sulfur-solubility
in y iron in the binary Fe-S system saturated with pyrrhotite. The diffusivity of sulfur in wüstite was determined by oxidizing
Fe-S alloys in mixtures of CO and CO2, and analyzing the entire sample for sulfur afterwards. From the amount of sulfur diffused through the growing wüstite layer
into the gas phase, the diffusivity of sulfur in wüstite was evaluated, and found to be 4.1 × 10−8 and 9.6 × 10−7 cm2/s at 1050° and 1250°C respectively. These values are of the same order as the self-diffusivity of iron in wüstite in equilibrium
with iron at the same temperatures. 相似文献
6.
中国钢铁生产主要以高能耗和高排放的高炉-转炉长流程为主,节能减排压力较大。因此,积极研发高炉低碳炼铁技术,促进高炉工序CO2减排尤为重要。铁焦是将含铁原料加入适宜的煤中,经焦化或炭化后成型的新型碳铁复合炉料,其高反应性可以显著降低热储备区温度、降低碳消耗,高炉使用适量的铁焦可实现一定程度的节能降碳。基于现场生产数据,采用㶲分析理论,建立高炉使用铁焦的㶲平衡模型,探索铁焦添加量对高炉物料消耗及能量利用效率的影响。结果表明,高炉使用铁焦后,炉内间接还原得到发展,碳利用率提高,炉内灰分量降低,冶炼单位生铁的碳素消耗和炉渣量均会降低,与未使用铁焦相比,高炉使用114 kg铁焦后,吨铁碳素消耗降低25.95 kg,渣量降低11.28 kg。此外,铁焦内部的金属铁仅需熔化,节省还原所需的㶲量,焦炭和鼓风带入㶲会显著降低,因此高炉冶炼吨铁消耗的总㶲量降低,同时,炉内传热也得到改善,内部㶲损失有效降低,与未使用铁焦相比,高炉使用114 kg/t铁焦后,目的㶲效率由46.14%提高至48.87%,热力学完善度由87.46%提高到88.02%。在此条件下,高炉吨铁的内部㶲损失降低192.63 MJ,实现节能6.57 kg(标煤)。 相似文献
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Fired compacts of hematite doped with different contents of CaO (mass fractions were 3.5, 4.0, 4.5, 5.0 %) were isothermally reduced to wüstite in a CO‐CO2 gas mixture at 1173K. It was found from X‐ray diffraction investigation that the lattice parameters of wüstite increased with CaO content dissolved in wüstite crystal. The pure wüstite as well as the wüstite doped with CaO were reduced at different temperature. The results showed that the reductions were promoted with increasing CaO content. The higher the content of CaO dissolved in wüstite crystal was, the larger the lattice parameter and the interplanar distances of wüstite became. This expansion was helpful to the migration of Fe ions and enhanced the reduction. At the early stage, the reduction of pure and doped wüstite compacts was controlled by the interfacial chemical reaction step. At the latter stage, the gaseous diffusion was the rate‐determining step for both sample types. 相似文献
9.
钢铁工业是中国制造业中碳排放量最高的行业,碳排放占全国碳排放总量的15%左右。高炉是钢铁工业碳消耗量最大的工序,碳消耗占钢铁流程总碳消耗的70%以上,减少高炉冶炼碳消耗是降低钢铁工业碳排放的最有效措施。高炉喷吹富氢气体不但可以提高冶炼效率,减少污染物排放,而且可以减少焦炭或煤粉消耗,从源头上降低高炉冶炼碳消耗,从而减少碳排放。以山西晋南钢铁两座1 860 m3高炉风口喷吹富氢气体工业化生产数据为例,详细研究了高炉喷吹富氢气体对燃料比、风口理论燃烧温度、炉腹煤气量、H2利用率以及CO2排放量的影响。结果表明,喷吹富氢气体可以显著降低高炉固体燃料消耗,在吨铁富氢气体喷吹量为65 m3条件下,富氢气体与固体燃料的置换比为0.49 kg/m3;风口喷吹富氢气体降低了风口理论燃烧温度,吨铁每喷吹1 m3富氢气体,风口理论燃烧温度降低约1.5 ℃,高炉鼓风量和炉腹煤气量都少量降低;喷吹富氢气体以后,炉内H2的利用率平均为37.3%,CO的利用率约为43.2%;吨铁CO2排放量可以降低80 kg左右,高炉CO2排放降低了5.6%,取得了较好的经济、环境和减污降碳效果。 相似文献
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Yury Kapelyushin Yasushi Sasaki Jianqiang Zhang Sunkwang Jeong Oleg Ostrovski 《Metallurgical and Materials Transactions B》2017,48(2):889-899
Reduction of un-doped magnetite is developed topochemically with the formation of a dense iron shell. However, the reduction of alumina-doped magnetite to wüstite proceeds with the formation of a network-like structure which consists of criss-crossed horizontal and vertical plates of wüstite. Reduction of magnetite includes the conversion of Fe3+ to Fe2+ and the movement of iron cations from the tetrahedral sites on the {400} and {220} planes of magnetite to the octahedral sites on the {200} planes of wüstite. Alumina has a negligibly small solubility in wüstite. In the reduction of magnetite doped with Al2O3, rejected Al3+ cations from wüstite diffuse to the magnetite–hercynite solid solution. Enrichment of the Fe3O4–FeAl2O4 solution with alumina in the vicinity of the reduction interface restricts the growth of {220} planes of wüstite and nucleation of {220} planes adjusted to the existing planes, preventing the merging of wüstite plates during the reduction process. Reduction of magnetite from the magnetite–hercynite solid solution practically stops when the Al3+ content at the interface approaches the solubility limit. Wüstite in the separated plates is reduced further to iron. 相似文献
12.
《钢铁冶炼》2013,40(3):222-229
AbstractTwo measures for coke saving and increase in blast furnace efficiency related to coke characteristics – reactivity and size – are discussed in this paper. Modern blast furnace operation with low coke rate and high injection rate causes a change in coke quality requirements. A discussion has arisen recently about highly reactive coke. Here, a theoretical analysis of influence of coke reactivity on the thermal reserve zone, direct reduction and carbon consumption in the blast furnace has been undertaken. Experiments have been performed using non-standard test scenarios that simulate coke behaviour under real blast furnace operating conditions. Coke reactivity and microstructure have also been investigated under the impact of alkali and pulverised coal ash and char. Operation of many blast furnaces has proved the possibility of coke saving and increase in productivity when using small-sized coke (so-called nut coke) mixed with the burden, but the reasons for this phenomenon, and consequently the limit for nut coke consumption, are still not very clear. An analytical method and cold model simulations have been used to quantify the change in shaft permeability and furnace productivity when using nut coke. 相似文献
13.
Elsayed Abdelhady Mousa Alexander Babich Dieter Senk 《Metallurgical and Materials Transactions B》2014,45(2):617-628
The application of off-gases from the integrated steel plant for the direct reduction of lump iron ore could decrease not only the total production cost but also the energy consumption and CO2 emissions. The current study investigates the efficiency of reformed coke oven gas (RCOG), original coke oven gas (OCOG), and coke oven gas/basic oxygen furnace gas mixtures (RCOG/BOFG and OCOG/BOFG) in the direct reduction of lump iron ore. The results were compared to that of reformed natural gas (RNG), which is already applied in the commercial direct reduction processes. The reduction of lump ore was carried out at temperatures in the range of 1073 K to 1323 K (800 °C to 1050 °C) to simulate the reduction zone in direct reduction processes. Reflected light microscopy, scanning electron microscopy, and X-ray diffraction analysis were used to characterize the microstructure and the developed phases in the original and reduced lump iron ore. The rate-controlling mechanism of the reduced lump ore was predicted from the calculation of apparent activation energy and the examination of microstructure. At 1073 K to 1323 K (800 °C to 1050 °C), the reduction rate of lump ore was the highest in RCOG followed by OCOG. The reduction rate was found to decrease in the order RCOG > OCOG > RNG > OCOG-BOF > RCOG-BOFG at temperatures 1173 K to 1323 K (900 °C to 1050 °C). The developed fayalite (Fe2SiO4), which resulted from the reaction between wüstite and silica, had a significant effect on the reduction process. The reduction rate was increased as H2 content in the applied gas mixtures increased. The rate-determining step was mainly interfacial chemical reaction with limitation by gaseous diffusion at both initial (20 pct reduction) and moderate (60 pct reduction) stages of reduction. The solid-state diffusion mechanism affected the reduction rate only at moderate stages of reduction. 相似文献
14.
研究了五种具有不同反应性的焦炭对高炉块状带含铁炉料还原的影响规律,并对料层的压差、CO体积分数以及含铁炉料的还原程度进行了分析.当炉内通入的原始气体中CO体积分数(仅考虑CO和CO2)为72.22%时,随着焦炭反应性的增强,焦炭气化速率加快,含铁炉料颗粒周围的CO体积分数升高,含铁炉料的还原度依次增高,还原度从使用低活性焦炭时的33.18%增大到使用高活性焦炭时的53.83%;而当原始气体成分中CO体积分数为66.67%时(低于900℃还原FeO的平衡气相体积分数),使用高反应性焦炭也可还原出金属铁.由此可见,适当增加入炉焦炭的反应性,可促进焦炭与含铁炉料间的耦合反应,提升料层CO体积分数,提高含铁炉料进入软熔带区域的金属化率. 相似文献
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S. V. Filatov S. A. Zagainov L. Yu. Gileva I. F. Kurunov V. N. Titov 《Steel in Translation》2017,47(8):534-537
Analysis of measures used to reduce energy expenditures shows that methods in which a single parameter is changed are ineffective. Coordinated adjustment of several parameters is required. Theoretical analysis reveals the combinations of parameters with the greatest effect. The influence of the granulometric composition of the sinter on the blast-furnace efficiency is considered in terms of the influence of the mean piece size on the reduction rate and the gas dynamics of the upper furnace region. When the reaction FeO + CO = Fe + CO2 reaches equilibrium, the heat consumption in smelting is reduced by increasing the smelting rate. Analysis of specific approaches to reducing the heat consumption in blast furnaces for the example of PAO Novolipetskii Metallurgicheskii Kombinat (NLMK) indicates the basic measures that decrease heat consumption: optimization of the iron ore by reducing the proportion of the >45 mm fraction; increase in output of the blast furnaces to 75–90 t/day (per m2 of hearth); operation with the highest permissible pressure (in terms of the charging-unit design); increase in hot strength of the coke to 60–62%; pulverized- coal injection at 140 kg/t of hot metal; and optimization of the ore distribution over the furnace radius. Between 2013 and 2016, those measures decreased coke consumption by more than 10 kg/t of hot metal. In addition, the total consumption of carbon fuel was reduced. 相似文献
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《钢铁冶炼》2013,40(6):418-429
AbstractIn this study, synthetic sinters with different basicity (CaO/SiO2?=?0, 0·5 and 2·0) were prepared at 1300°C and prereduced at 900°C using low potential reducing gas (LPRG; 20%CO, 20%CO2, 5%H2 and 55%N2). The prereduced sinters were subsequently reduced to metallic iron at 950–1100°C using relatively high potential reducing gas (HPRG; 30%CO, 5%CO2, 10%H2 and 55%N2). Both LPRG and HPRG were selected to simulate the gas composition in the blast furnace upper and lower shaft respectively. High pressure mercury porosimeter, X-ray phase analysis, optical and scanning electron microscope were used for the analysis of the prepared and reduced sinters. In the original basic sinter, calcium ferrite (CaFe2O4) and dicalcium silicate (Ca2SiO4) phases were identified as well as the main Fe2O3 phase, whereas wollastonite [Ca2·87Fe0·13(SiO3)3] and silica (SiO2) were formed in the acidic sinter. The prereduction in sinters with LPRG at 900°C resulted in the formation of wüstite (Fe0·902O) phase. The subsequent reduction in wüstite sinters to metallic iron using HPRG at 950–1100°C was found to be the highest for basic sinter and the least for acidic sinter. The higher reduction rate of basic sinter was attributed to the enhancement of wüstite reducibility through the formation of calcium ferrites. The lower reduction rate of wüstite in acidic sinter was attributed to the formation of hard reducible fayalite (Fe2SiO4) and ferrobustamite [(Ca0·5Fe0·5)SiO3] phases. The rate controlling mechanism during the reduction process was estimated by the correlation between apparent activation energy calculation and microstructure investigations. 相似文献
19.
《钢铁冶炼》2013,40(3):155-162
AbstractRolling mill scale is a solid byproduct of the steelmaking industry that contains metallic iron and three types of iron oxides: wüstite, haematite and magnetite. It also contains traces of non-ferrous metals, alkaline compounds and oils from the rolling process. A study was made of the reduction of mill scale to sponge iron using coke at different temperatures and times. The reduced samples were studied by X-ray diffraction and scanning electron microscopy. Oxygen analysis was carried out by combustion in a LECO oven. Sponge iron was successfully produced for reuse in electric furnaces as part of the metallic charge or as a raw material in the production of iron-based powder metallurgy parts. 相似文献
20.
The traditional blast furnace ironmaking process has many problems such as long process flow, high dependence on coke and large environmental pollution. In order to solve these problems, the new ironmaking process of rotary kiln pre- reduction and smelting by coal and oxygen was developed. This new process has advantages of wide raw material adaptability, no coke consumption, less pollutant emissions and suitable for special iron ore resources. The mathematical model of the new process was established. Numerical simulation results show that the metallization rate of pre- reduction iron, smelting furnace gas oxidation degree and blast air oxygen content have great influence on coal and oxygen consumption. The coal and oxygen consumption reduces with the increase of pre- reduction iron metallization rate, the rise of oxygen degree of coal gas or the decrease of oxygen content of blast air. This process has a significant advantage in smelting special iron ore resources, which can make up the shortage of blast furnace ironmaking. It is also of great significance to reduce fuel consumption and CO2 emissions. 相似文献