Influence of nature and particle size distribution on granulation of iron ore mixtures used in a sinter strand

Abstract

The ore mixture granulation process is described and the granulation fitness of a series of iron ores forming part of the mixture is studied. Good granulation and control of the maximum sintering temperature makes it possible to achieve the optimum sinter structure, formed by a hematite nucleus surrounded by a lattice of acicular ferrites. The granulation fitness of ore mixtures used to manufacture a series of sinters in a pilot plant are also determined. It is verified that sinters with an optimum structure have been obtained. A series of iron ores are classified using the granulation index (G index). The evolution of the G index of ore mixtures used in ACERALIA during recent years is considered and it is verified how improvement of the G index increases productivity and decreases coke consumption in the sinter strand.     

Sintering Properties and Optimal Blending Schemes of Iron Ores

 In order to obtain good sintering performance, it is important to understand sintering properties of iron ores. Sintering properties including chemical composition, granulation and high-temperature behaviors of ores from China, Brazil and Australia. Furthermore, several indices were defined to evaluate sintering properties of iron ores. The results show that: for chemical composition, Brazilian ores present high TFe, low SiO2, and low Al2O3 content. For granulation, particle diameter ratio of Brazilian ores are high; particle intermediate fraction of Chinese concentrates are low; and average particle size and clay type index of Australian ores are high. For high-temperature properties, ores from China, Brazil and Australia present different characteristics. Ores from different origins should be mixed together to obtain good high-temperature properties. According to the analysis of each ore′s sintering properties, an ore blending scheme (Chinese concentrates 20%+Brazilian ores 40%+Australian ores 40%) was suggested. Moreover, sinter pot test using blending mix was performed, and the results indicated that the ore blending scheme led to good sintering performance and sinter quality.     

基于生石灰吸水性的适宜烧结制粒水分

为了有效发挥生石灰在制粒过程的作用,依据生石灰的吸水特性对烧结料制粒水分进行优化,是值得深入研究的工艺技术问题。考察了固定量配水、满足生石灰完全消化的配水,以及满足生石灰湿容量的配水等3种加水量选取方式,对烧结混合料制粒效果的影响。研究结果表明:烧结制粒过程中生石灰的吸水,一方面消耗于生成Ca(OH)2的化合水,另一方面还包括生石灰消化后自身吸收的物理水,二者影响烧结料的水分含量及分布;当制粒水分满足化合水消耗时,虽然烧结料水分得以保证,但消石灰和CaCO3吸水会争夺铁矿粉中的水分而影响制粒效果;当制粒水分满足生石灰湿容量时,可获得适宜烧结制粒水分,使铁矿粉中的水分得以保证,生石灰改善制粒的作用充分发挥。     

铁矿粉烧结制粒过程颗粒行为研究综述

摘要：烧结原料需经过制粒处理以确保高效低耗的烧结生产,即在水或其他粘结剂的参与下混合料颗粒在相互运动、碰撞中形成粒度更大且粒度分布更窄的聚团颗粒体。制粒效果受制粒设备参数和铁矿粉物理化学性质的影响,因而合适的制粒工艺和铁矿粉优化配置对烧结技术经济指标的改善具有显著作用。阐述了制粒现象的基本理论,综述了制粒过程中颗粒聚结长大的作用力以及颗粒的长大机制,制粒工艺参数如加水量、搅拌动能、制粒时间等和铁矿石的粒度组成、表面性质、颗粒形貌等性质对制粒效果的影响规律。相关结果为系统深入理解铁矿粉制粒过程以及高效生产优质准颗粒提供理论基础。     

褐铁矿配加澳矿的烧结效果

对褐铁矿配加澳在利亚矿进行了烧结试验。研究表明：与褐铁矿相比,澳大利亚矿适合于低水、低碳烧结。对碱度为２．０的烧结矿,配加３０－４０％的澳矿,其烧结效果最佳。     

铁矿粉颗粒特性对其烧结制粒性的影响

 掌握铁矿粉的烧结制粒性是进行制粒工艺参数优化以保证混匀矿优良制粒效果的基础,确定铁矿粉颗粒特性对其制粒性的影响,是值得深入研究的工艺理论问题。通过微型圆筒制粒法研究铁矿粉的圆形度[（Ψw）]、气孔率[（P）]、润湿性[(cosθ)]以及粒度分布对其制粒性的影响,在此基础上,采用回归方法预测混匀矿的制粒性。结果表明,铁矿粉的圆形度和气孔率对其制粒性有负面影响,而提高润湿性则有利于铁矿粉制粒;铁矿粉粗颗粒群的制粒性与其等效表面积呈反比,细颗粒群的制粒性与其黏附粉与中间粒级的比值[(R<0.25 mm/0.25～1.00 mm)]呈正比;混匀矿的制粒性可以根据各组元的配比和颗粒特性进行有效预测。     

吸水剂对高铝S矿烧结影响的试验研究

通过系列正交试验,研究了吸水剂添加对高铝S矿烧结性能的影响。结果表明:S矿含水14%~16%,矿料易于形成湿黏团状物,吸水剂能够快速吸收矿料表面水分,使湿黏团状物粒度得到改善,改善了混合料的制粒条件,提升了烧结料层透气性,加速了垂直烧结速度,提升了烧结产量。但由于烧结速度加快,高温区域保温时间势必缩短,从而影响了提升强度液相的生成,造成了烧结矿物理强度的下降。     

Improvement of sintering characteristics by selective granulation of high Al2O3 iron ores and ultrafine iron ores

The worldwide steel companies are expected to use low grade iron ores such as pisolitic iron ores, high Al₂O₃ iron ores and ultrafine iron ores etc. in their sinter blends due to the depletion of high grade iron ores or for the economic reason. This study investigated the methods for improving sintering characteristics without deteriorating sintering productivity and sinter quality by blending mini-pellets comprising high Al₂O₃ pisolitic iron ores and ultrafine iron ores containing low alumina. The results showed that the blending of iron ore mini-pellets produced by selective granulation is an effective way to improve sintering productivity and sinter quality without increasing the Al₂O₃ content in sinter as well as to effectively utilise high Al₂O₃ iron ores and ultrafine iron ores in the sintering process.     

TG-DSC法对莱钢进口铁矿粉烧结性能的研究

采用TG-DSC法对进口铁矿粉添加生石灰的烧结性能进行了研究。实验结果表明,此法可以表征铁矿物烧结过程中发生的物理和化学变化,弄清了添加8．45％生石灰后巴西MBR粗粉、澳大利亚库利安诺宾粗粉和哈默斯利粗粉在烧结过程中产生液相的初始温度、主体矿物熔化温度,以及结晶与凝固温度。三者相比,库利安诺宾粗粉和巴西MBR粗粉比哈默斯利粗粉更有利于低温烧结。实验还发现,铁矿物在熔化和凝固中分别伴随着赤铁矿分解—磁铁矿氧化过程,铁酸半钙存在对磁铁矿氧化有抑制作用。     

Relationship between sinter properties and iron ore granulation index

Abstract

A range of iron ores were used in varying proportions to prepare 28 different ore mixtures. Each mixture was classified according to its granulation index and sintered in a pilot plant. The resulting sinters were characterised by chemical analysis, degradation during reduction in the blast furnace (reduction degradation index test), cold strength (tumbler test), coke consumption and process productivity. Sinter quality was assessed in relation to the granulation index of the ore mixture.     

Influence of Alumina on Iron Ore Sinter Properties and Productivity in the Conventional and Selective Granulation Sintering Process

Iron ore sinter constitutes a major proportion of blast furnace burden. Hence, its quality and consistency have a significant impact on blast furnace performance. Iron ore fines are the main source for sinter, and the chemical composition of the iron ore fines, together with the thermal conditions that blends are subjected to, plays an important role in forming the primary melt during the sintering process and accordingly determines the sinter structure and quality. Therefore, considerable importance has been placed on the chemical composition and consistency of iron ore fines, particularly in terms of alumina content. Due to depletion of high grade iron ore resources, alumina content in the iron ore fines is expected to increase gradually. Ore with higher alumina content is usually expected to be detrimental in forming the sinter matrix, if sintered alone, due to the low reactivity of alumina bearing minerals and the high viscosity of primary melts. The selective granulation process is a new sintering process for high alumina iron ore fines, and can eliminate the adverse effects of ‘hard to sinter’ or ‘unsuitable – for ironmaking’ ores. In the present work laboratory sintering experiments have been carried out with iron ore fines of different alumina level (2.00 to 5.46 mass‐%) to know the influence of alumina on mineralogy, productivity, physical and metallurgical properties of sinter prepared by the conventional and the selective granulation process. With increasing alumina content in sinter of both the conventional and selective granulation process, the fractions of hematite and of silico‐ferrites of calcium and alumina (SFCA) as well as the pore phase increased whereas the magnetite and silicate phases decreased. With increase in alumina content sinter productivity and tumbler index (T.I.) decreased, and metallurgical properties like sinter RDI and reducibility improved. However, sinter of the selective granulation process showed better results compared to the conventional process.     

钢铁企业烧结制粒工艺与设备优化进展及趋势

 为明晰当前烧结制粒工艺的发展进展及未来发展的趋势,对钢铁企业烧结制粒工艺与设备进行了充分的总结与分析。烧结制粒性能直接影响着料层透气性以及准颗粒结构分布,是钢铁企业烧结工序中重要的环节,长期以来铁矿石烧结工序的热态性能受到较多关注,但制粒性能欠缺重视。近年来,随着理论和工艺的发展,烧结制粒受到钢铁企业越来越多的重视,随之针对制粒也采取了诸多工艺与设备的优化措施。首先阐述了烧结制粒优化的意义,进而总结了近些年来国内外钢铁企业在原料预处理、滚筒设备、生石灰消化以及混合料水分监测4个方面针对制粒做出的优化进展,并基于对烧结制粒的理解和新兴人工智能技术的认识展望了在可预见的未来钢铁企业烧结制粒优化的趋势。     

Influence of Iron Ore Characteristics on FeO Formation During Sintering

  The influence of iron ore characteristics on FeO formation during sintering was examined mainly in terms of chemical composition and the melting characteristics of iron ores. Statistical regression and X ray diffraction were used to further explain the specific effect of iron ore characteristics on FeO formation. The results indicate that LOI (loss on ignition) in iron ores have a positive influence on FeO formation by promoting the sintering process of Fe2O3 decomposing and reducing. Silica contents in iron ores play a determining role in final content of FeO in sinter. The melting characteristics of iron ores significantly affect FeO formation during sintering.     

铁矿石高温烧结基础特性评价方法的国外研究进展

 随着全球优质铁矿石日益减少、资源禀赋变差,国内外钢厂普遍面临着烧结原料供应不稳定、铁矿石性质波动大、原料结构频繁变化等问题,对烧结生产、高炉冶炼和产品质量产生了极大的不利影响。因此,开展铁矿石烧结性能评价研究具有重要的现实意义。铁矿石烧结基础特性可分为冷态特性和高温特性两大类,前者主要包括铁矿石的化学成分、粒度组成、矿物学特性等常温性质,后者主要包括铁矿石的同化性能、液相生成特性等高温成矿行为及实际烧结性能。概述了国外关于铁矿石高温烧结基础特性评价方法的研究进展,系统归纳了不同研究机构提出的评价指标和试验方法。已有研究表明,现有基于团块烧结法的评价方法虽然对铁矿石不同的烧结行为分别进行了深入研究,但未能在其与铁矿石的实际烧结性能之间建立起准确可靠的关系,主要原因在于,对影响铁矿石实际烧结性能的最关键因素把握不准,同时对烧结过程的模拟性有待提高。因此,揭示铁矿石基础特性与其烧结性能的内在联系,首要前提在于必须深入研究和把握“铁矿石-制粒物料-烧结矿”不同阶段物料性质的传递规律,查明影响铁矿粉烧结过程的主要因素,这对找准高温烧结基础特性研究的切入点具有十分重要的意义。     

钒钛磁铁精矿的矿物特性与造块强化技术

攀枝花钒钛磁铁矿矿物组成复杂,属于难选、难烧、难炼的矿石,其精矿含铁品位低,TiO2含量高,粒度粗,制粒性能差,影响烧结透气性。采用阶磨阶选工艺可提高铁品位2%左右,但TiO2变化不大。该精矿初始熔点高,生成液相量少,烧结矿矿物组成复杂,严重影响强度与冶金性能。烧结采取了使用生石灰、提高烧结矿碱度等主要强化技术,烧结与高炉冶炼取得了重大技术突破。     

细粒级铁矿粉对烧结液相和矿结构的影响

利用基础烧结设备检测了细粒级铁矿粉同化速度、流动能力,并通过微型烧结杯模拟料层下部单元点烧结过程的方法来研究配加15%细粒级矿粉的烧结矿结构变化,有效分析了3种细粒级矿粉在烧结时的液相行为及对烧结矿结构和性能的影响。通过比较生产用混匀矿与配加质量分数为15%的A、B、C粉的烧结矿结构表明:A粉有利于减少烧结矿内部孔洞的尺寸,减少核颗粒和液相间较大孔洞的数量,并能促进针铁矿发展;B粉会增加烧结矿内部大孔洞,增加柱状或片状铁酸钙的生成;C粉同化速度慢,液相流动能力差,粘结效果差,会使液相与核颗粒间孔洞尺寸和数量增加。烧结杯试验结果表明:在生产用混匀矿中使用质量分数为15%的A粉,烧结矿的转鼓指数提高2.94%,低温还原粉化指数(RDI)降低3.37%。     

巴西Vale低硅铁矿粉烧结性能研究

采用最优实验设计方法,在实验室条件下进行了巴西Vale低硅粉矿配加低硅铁精矿的烧结杯实验,研究了该粉矿配比对烧结主要技术经济指标及烧结矿冶金性能的影响。通过优化其它铁料、燃料配比及混合料水分,确定了在巴西Vale低硅粉矿配比为19．35％、水分为6．9％-7．1％时,可获得较好的烧结性能指标。     

Structure Model of Granules for Sintering Mixtures

Structure model of granules, boundary value of nucleus and powder, and the relationship between granula- tion efficiency and boundary value were investigated. Granules of sintering mixtures are composed of adhesive powder and nucleus. In the mixtures, particles larger than 1.00 mm act as nucleus and particles smaller than 0.25 mm act as adhesive powder. Particles with size between 0.25--1.00 mm can be adhesive powder as well as nucleus depending on the granulation conditions. When the boundary value is close to 0.25 mm, the granulation efficiency is lower than 50%. When the boundary value is close to 1.00 mm, the granulation efficiency is above 90%. The boundary value is influenced by the iron ore type, granulation moisture, fineness of raw materials and burnt-lime activity. Good adhe- sive capability, suitable moisture content, appropriate particle size distribution and high burnt-lime activity make the boundary value move towards 1.00 mm and improve the granulation efficiency.     

褐铁矿在烧结工艺中的优化配置

为了探究全进口矿条件下褐铁矿在烧结工艺中的合理配置,实现褐铁矿的高效利用以进一步提铁降本,针对S钢铁公司500 m2大型烧结机实际原燃料条件,基于试验用铁矿粉的常规理化性能和高温烧结基础特性开展了不同褐铁矿配比的烧结杯试验研究,结合Factsage 7.1热力学软件,模拟计算了不同褐铁矿配比条件下的黏附粉含量和理论液相生成量及性能,并采用矿相显微镜分析了烧结矿的显微结构,探明了褐铁矿与赤铁矿和磁铁矿的优化搭配规律。研究表明:澳大利亚褐铁矿具有粒度粗、矿化能力弱,同化温度低、黏结相强度差、吸液性强的特点,当褐铁矿质量分数由45%增加至55%时,提高磁铁精矿OD矿的质量分数至15%,同时降低OC矿质量分数至10%,烧结矿转鼓强度和低温还原粉化性能等指标达到最优,这是由于一方面提高磁铁精矿配比不仅具有增加黏附粉比例、改善液相生成数量和性能的作用,而且可以均匀液相分布,消除过熔现象;另一方面,增加磁铁精矿配比可以改善烧结料球的粒度组成,减少褐铁矿吸液量,提高烧结矿强度。因此,在高褐铁矿配比条件下,增加适宜的磁铁精矿配比有利于稳定烧结矿质量,全面改善烧结矿性能。      

巴西和印度粗矿粉烧结特性研究

对巴西和印度粗矿粉的烧结性能进行了研究,结果表明,这两种矿烧结性能较差,当它们的总和超过综合料配比的３０％时,烧结矿产量降低,含粉率升高,大烟道温度下降。其原因是巴西矿和印度矿粒度组成差,颗粒形成不合理及软化温度区间大所致。