含钒钛铁矿球团还原过程中微观结构变化

在实验室模拟高炉条件下研究了含钒钛铁矿球团的还原过程,采用X射线衍射仪测定含钒钛铁矿球团在不同还原温度下的物相组成,通过光学显微镜和扫描电镜观察含钒钛铁矿球团还原过程中微观结构变化,并结合能谱分析仪研究氧化物中不同元素的分布状况.含钒钛铁矿球团在还原过程中出现的铁钛分离现象会影响含钒钛铁矿球团的还原性,形成的高钛含量钛铁晶石会增加铁氧化物还原难度.高温时形成的密实金属铁球壳会阻碍内部氧化物的还原,导致还原停滞,从而造成含钒钛铁矿球团高温还原性较差.当内部熔融物滴下时,会提高高炉下部氧势,有利于减少Ti(C,N)的生成.      

小块焦对高炉焦比的影响

在高炉冶炼过程中小块焦一直被认为只是作为资源再利用,使用时常常不被看好。通过实验室的探索性研究,了解到小块焦的粒度效应对其失重率作用很大,小块焦的反应性相对于冶金焦有很大的提高。可以认为小块焦在炉内改善了还原性,有促进矿石还原作用。小块焦的大量气化吸热有降低热储备区温度的倾向,对高炉的燃料消耗进一步降低起了一定作用。750 m3高炉的生产性试验结果表明,提高小块焦的用量有利于燃料消耗的降低,其他工艺参数不变,增加1 kg/t的小块焦相当于置换焦比1.19 kg/t。     

高炉使用含碳复合炉料的原理

 高炉炼铁正朝着高产、低污染、低能耗的方向发展,为了实现这一目标,包括高炉使用含碳复合炉料等一些革新的炼铁技术已经被提出或实际应用。铁焦、热压含碳球团是将铁矿粉和煤粉按一定比例混合后制成的新型含碳复合炉料。研究结果指出,含碳复合炉料相比于传统的高炉炉料（烧结矿和球团矿）具有高温强度高、还原性能好以及原料适应性强等优势。阐明了高炉使用含碳复合炉料的基本原理,介绍了铁焦制备的工艺流程及应用情况,重点进行了热压含碳球团制备工艺流程、冷态冶金性能、高温冶金性能、高炉使用热压含碳球团等试验研究,最后利用多流体高炉数学模型对高炉使用热压含碳球团操作进行了模拟研究。研究表明,高炉使用一定量的含碳复合炉料可以降低热空区温度,增加产量,降低焦比,高炉热利用效率明显提高,操作性能得到有效改善。     

高炉添加金属化球团炉料的冶金性能试验

在掌握金属化球团及其他含铁原料特性的基础上,采用熔滴试验方法,考察不同比例金属化球团对高炉冶炼过程的影响。试验结果表明：金属化球团具有含铁品位高、金属化率高、还原性能好、无低温还原粉化、软熔滴落性优良等特点,在高炉中配加金属化球团其综合炉料的软熔滴落性能变好,但考虑到配加金属化球团后减少焦比对高炉的影响,其配加比例在20%（质量分数）左右比较适宜。     

添加铁矿粉对焦炭质量影响的研究

高反应性焦炭能够降低高炉焦比,减少CO2的排放量,改善高炉内铁矿石还原反应的反应效率。研究了在配合煤中添加碱性铁矿粉和酸性铁矿粉炼焦,铁矿粉的配入量对焦炭热性能的影响规律。试验结果表明,随着铁矿粉配入量的提高,焦炭的反应性增大,随后增幅放缓,且添加碱性矿粉的焦炭反应性高于添加酸性矿粉的焦炭,反应后强度与机械强度均有明显劣化;焦炭的灰分增大、硫含量逐步下降;焦炭的各向异性指数不断下降。     

Effect of coke reactivity and nut coke on blast furnace operation

Abstract

Two 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.     

Effect of mixing charge of highly reactive semicoke nut on the reaction of high Al2O3 ferrous burden in blast furnace

In order to improve the performance of blast furnace ironmaking when using the high Al₂O₃ iron ore, the technology of mixing charge of high reactive semicoke nut with ferrous burden was proposed and systematically investigated at laboratory scale in the present paper. The CO₂ gasification activation energy of semicoke ranged from 136.5 to 150.3?kJ?mol^?1, which was lower than that of the traditional coke. At the temperature of 1200°C, the reduction degree of ferrous burden increased a little with the addition of semicoke nut and the consumption ratio of semicoke was 14.0?wt-% under the simulated blast furnace ironmaking condition. The mixing charge of semicoke could obviously reduce the softening beginning temperature, increase the melting temperature and improve the permeability compared with the standard and traditional coke mixing charge samples. During the total softening and melting process, about 90?wt-% of the semicoke nut and 45?wt-% of the traditional coke nut were consumed, respectively. The experiment results indicated that the mixing charge of high reactive semicoke nut could obviously improve the performance of blast furnace ironmaking when using high Al₂O₃ ferrous burden and the semicoke was more effective than traditional coke.     

Effect of Coke Reaction Index on Reduction and Permeability of Ore Layer in Blast Furnace Lumpy Zone Under Non-Isothermal Condition

 Reasonable control on CRI (coke reaction index) is one of the key factors for BF (blast furnace) low-carbon smelting. However, there are contrary opinions. One is increasing CRI to improve reaction efficiency in BF and the other is decreasing CRI to suppress coke degradation in furnace. Different methods are adopted to realize effective catalysis (increasing CRI) and passivation (decreasing CRI) of coke. Simulation tests of coke in BF lumpy zone under gradual temperature rising have been done. Effect of CRI on gas composition, ore reduction, burden column permeability and heat reserve zone′s temperature under non-isothermal condition are studied. Then combined with iron making calculations, a novel BF operation suggestion is proposed as coke nut with small size be catalyzed and mixed with ore while skeletal coke with large size be passivated and separately charged into BF.     

Blast Furnace Operating Conditions Manipulation for Reducing Coke Consumption and CO2 Emission

A comparative reduction behavior of wüstite samples prepared from iron ore sinter was investigated to find the optimum way for reducing coke consumption and CO₂ emission in blast furnace technology. A series of wüstite reduction experiments was carried out using different gas mixtures. A correlation between the experimental results and real data of blast furnaces at Egyptian Iron and Steel Company (EISCO) was demonstrated in order to optimize the coke consumption inside blast furnaces. Different theoretical models were applied on real data of blast furnaces to calculate the effect of operation parameters on the coke consumption. It was found that the wüstite reducibility can be controlled and enhanced using certain ratio of H₂ and CO gases. Such kind of enhancement decreases the remaining quantity of unreduced wüstite which descends to the high temperature region of blast furnace. The theoretical analysis of real data using certain values of H₂ and CO shows that increasing the amount of natural gas injection in blast furnace of EISCO will decrease the degree of direct reduction of iron oxide and consequently will decrease the amount of coke consumption.     

攀钢高炉配加澳大利亚块矿试验研究

介绍了攀钢高炉配加澳大利亚块矿工业试验情况,分析了使用该矿后高炉的冶炼特点及对高炉生产指标的影响,同时研究了澳大利亚块矿的冶金性能以及配加该矿后钛渣的性能变化。试验表明,高炉配加澳大利亚块矿后,产量增加,焦比降低,铁水质量改善。     

Performance Optimization and Efficient Application of Highly Reactive Iron Coke: Research Progress and Future Trend

Iron coke has emerged as a promising raw material for low-carbon ironmaking. However, the structure and properties of iron coke are still obstacles to practical application in blast furnaces, especially the strength of iron coke. Herein, investigations on the preparation and properties of iron coke are reviewed and an integrated system for the performance optimization and efficient utilization of iron coke is proposed. First, the characteristics of different preparation processes for iron coke are compared; then the advantages and limitations of the three processes are summarized. Afterward, the evolution mechanism of iron coke strength and the catalytic mechanism of Fe on the gasification reaction of iron coke are explored in depth. In addition, the coupling mechanism of iron coke gasification and iron ore reduction is analyzed and discussed. The influence of iron coke on the melting–dropping properties of blast furnace charge and the mathematical simulation of using iron coke in the blast furnace are analyzed and summarized. Finally, a comprehensive strategy for the performance optimization of iron coke and its efficient application in the blast furnace is proposed, in which the sequence slicing 3D reconstruction method is applied to analyze the relationship between microstructure and performance of iron coke.     

高炉使用铁焦的㶲分析

 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)。     

Utilization of High Sulfur Raw Materials in Iron Ore Pellets

Pyrite cinder and high sulfur magnetite were used as raw materials to produce iron ore pellets. Good qualities of green balls and fired pellets were obtained from the feed comprising 50% pyrite cinder and 50% high sulfur magnetite concentrate at a small scale. Small-scale tests were proven by pilot-scale tests. The high grade fired pellets, assaying 63.22% Fe, were analyzed, and the compressive strength of fired pellets was over 2500 N/pellet. The fired pellets possessed excellent metallurgical performances, such as reducibility index higher than 67%, reduction swelling index lower than 15% and low temperature reduction degradation index (+ 3.15 mm) higher than 1%, which can be used as the burden for blast furnace.     

Experimental study on the effect of using nut coke on the permeability of packed beds in blast furnaces

The charging pattern may affect blast furnace permeability,coke ratio,and the freedom to select low-grade raw materials. Ore-coke mixed charging is a potential technique for optimizing the charging pattern. In recent years,charging small-sized coke( nut coke) into the burden layer has been applied to save raw materials and decrease cost.Although mixed charging,especially adding nut coke into the burden layer,may have many advantages,the mechanisms and side effects of nut coke use are not well understood,and the mixing ratio is still limited in industrial blast furnace operation. In this study,the status of mixed charging,especially nut coke used in blast furnaces,was investigated. A cold flow model was established to study the permeability of the packed bed in the blast furnace "dry zone"under different conditions with the aim of better understanding the mechanisms of mixing coke and nut coke into the burden layer. The effect of coke size,mixing coke ratio,layer numbers,and gas flow rate on the pressure drop of the packed bed was investigated. The experimental results show that mixing the nut coke in the ore layers decreases the pressure drop to different extents depending on mixing ratio.     

莱钢2号1880 m~3高炉炉役后期稳定炉况生产实践

针对莱钢2号1 880 m~3高炉炉役后期生产特点,2013—2015年逐步采用了加长风口、优化布料制度和球团、生矿及焦丁平铺的技术措施,达到了稳定炉况、优化指标的目的。实际生产结果表明,加长风口长度有利于活跃炉缸中心,但需要上下部制度的配合;焦丁平铺后布在靠近炉墙位置,有利于改善边缘矿层的透气性,改善边缘矿石的还原,促进边缘气流的稳定和炉体软水水温差的稳定,有利于降低炉体热量损失,进而有利于降低高炉消耗。     

高炉冶炼预还原炉料能耗分析

 通过建立高炉冶炼预还原炉料数学模型,计算了原料铁品位、预还原炉料金属化率和铁的存在形态对高炉冶炼能耗的影响,比较了高炉冶炼预还原炉料和传统高炉的能耗。计算结果表明：针对不同铁品位原料,有一个适合高炉冶炼的炉料最佳金属化率,使高炉冶炼焦比最低;预还原炉料中的铁以硅酸铁形式存在时,主要进行直接还原,冶炼焦比较高;与传统高炉相比,高炉冶炼预还原炉料,可以大幅度降低焦比,但燃料比升高。     

Fundamental Study on Carbon Composite Iron Ore Hot Briquette Used as Blast Furnace Burden

Carbon composite iron ore hot briquette (CCB) is the product of fine iron ore and fine coal by hot briquetting process, which attracts more and more attention as a new type of ironmaking raw materials aiming to improve the operation efficiency and reduce the coke consumption of blast furnace. This paper is devoted to experimental study on metallurgical properties of CCB and numerical simulation of the BF operation with CCB charging. At first, the metallurgical properties of CCB, including cold crushing strength, RDI, RSI, reducibility, high temperature strength, and softening and dripping are experimentally tested and compared with the common burdens, which revealed that the CCB possesses the required metallurgical properties and is suitable to use as the blast furnace burden. Then, the effects of charging CCB on the dripping properties of comprehensive burdens are elucidated based on the experiments under simulated blast furnace conditions. The results showed that the maximum charging ratio of CCB in the iron burdens is 40%–50% for achieving appropriate dripping properties of the mixed burdens. Finally, a multi‐fluid blast furnace model is used to simulate BF operation with CCB charging. According to model simulations, charging CCB will cause the temperature level to decreases in the furnace and the location of the cohesive zone shifts downward. On the other hand, the productivity tends to increase while coke rate and total reducing agent rate decrease, the heat efficiency improves remarkably and the operation performance of BF is effectively enhanced.     

混装铁焦对人造富矿还原行为的影响

 高炉炼铁是资源、能源的消耗大户,节能潜力巨大。铁焦是一种高反应性焦炭,将合适粒度和数量的铁焦与含铁炉料混装入炉,从理论上说具有降低焦比,取得节约稀缺炼焦煤资源和降低生产成本的潜力。对混合试样的还原机理进行了分析,并对铁焦与人造富矿的耦合反应进行了实验室研究,证明混入铁焦对烧结矿和球团矿的还原反应有明显的促进作用,提高温度和增加铁焦用量对提高铁矿石的还原度有利。     

气基直接还原竖炉还原段参数设计方法

分析了气基直接还原竖炉还原段参数的影响因素,找到了各参数的研究方法;在模拟的气基直接还原竖炉还原氛围下进行了铁矿石的直接还原实验,研究了铁矿石的还原性和还原膨胀性;采用颗粒离散元仿真分析软件EDEM对颗粒炉料的传输过程进行仿真分析,研究了炉料的下降运动规律;结合实验数据和仿真结果,确定了竖炉还原段参数的表达式。研究结果表明:铁矿石在模拟条件下的必要还原时间约为3h,且还原膨胀率先增大后减小;竖炉中心炉料的下降速度大于边缘炉料的下降速度,且速度超前比受排料速度的影响较小;从上到下还原段内型曲线由3条拟合线段组成,对应的炉身角分别为:87.162°、88.949°以及90.652°。     

碱度对白云鄂博矿球团矿还原膨胀性能的影响

高比例球团矿冶炼是高炉炼铁发展的趋势。由于化学成分、矿物组成和结构的差异，不同企业生产或所用的球团矿还原膨胀的原因各不相同且相对复杂。面向保障矿产资源安全供给的国家重大战略需求，选择白云鄂博铁精矿球团矿作为研究对象，根据球团矿铁氧化物还原理论，从热力学方面深入研究碱度对球团矿还原膨胀性能的影响机理，并结合XRD结果来探究钙结合相在球团矿生产中的变化规律以及对球团矿还原膨胀的影响，找到满足高炉冶炼对球团矿还原膨胀率要求的合理碱度，从而提高白云鄂博铁精矿球团矿在包钢冶炼生产中的比例。完善特殊矿球团矿还原膨胀理论，为复杂共生矿高效冶炼提供理论支撑。研究结果表明，随着碱度的提高，球团矿的膨胀率呈现出先升高后降低的规律，碱度为0.8时，其膨胀率最大，达到75.743%,其外形如同花瓣开花，无法维持原来的球型。综合不同碱度球团矿含铁品位的高低和还原膨胀的大小，得到制备球团矿的最优碱度为1.4。随着碱度的提高，成品球的液相生成量先降低后升高，碱度为0.8时液相生成量最少。球团矿膨胀率先增加是因为球团矿的结晶度提高，晶粒粗大，晶体结构逐渐趋向有序，为铁晶须的生长奠定了基础；膨胀率后减小是因为生成了铁酸...