Can Modified Starch be Used As A Binder For Iron Ore Pellets?

Organic binders are often desired when making low-silica iron ore pellets. Corn and wheat are grown in large quantities near certain iron ore pelletizing facilities and their starches are easily modified to form cold-water-soluble powders that can be used as binders. We investigated how starch cold-water solubility, starch dose, starch hydration time, green ball moisture content, and firing temperature affected pellet quality. With a fluxed, hematite concentrate, the high-soluble starch led to good wet and dry balls, but weak and friable indurated pellets compared to the standard binder, bentonite clay. As expected, the low-soluble starch did not make as good green balls as the high-soluble starch. Thermogravimetric analyses of unfired pellets and their abrasion products showed that modified starch was inhomogeneously distributed in pellets, with a high concentration near the ball surfaces. The surface concentration increased, and the core concentration decreased, as pellets grew during the pelletizing process. This suggests that starch enrichment near surfaces is a consequence of the agglomeration–compaction process, and may occur with other pelletizing binders. Abrasion mass losses were 81% greater with modified starch than with bentonite at 1100°C, and 31% greater at 1250°C. However, starch contents near the surfaces did not qualitatively correlate to roughness, as the highest starch dose tested gave the smoothest and least dusty pellets.     

铁矿球团膨润土粘结剂提质改性研究进展

膨润土作为铁矿球团生产广泛使用的粘结剂,具有成球性能好、廉价易得的特点,但中国膨润土普遍质量差,直接使用时配加量常达到3％(质量分数)甚至更高,带来铁品位降低的问题.为降低膨润土用量,提高球团铁品位,国内外对膨润土的提质改性开展了广泛的研究,已达到能将膨润土用量降至1％甚至更低的技术水平.综述了膨润土分选提纯、钠化改性...     

Plate Water Absorption as an Assessment Tool for Organic Binders

Plate water absorption has been traditionally used to assess the binding ability of bentonite clay binders for iron ore concentrate pelletization. Until 1997, there was an accepted test by ASTM, but due to inconstant data this method was withdrawn. This value, however, is still used by some pelletization operations to gauge the efficacy of their bentonite. This test procedure has only been investigated on inorganic binders and never organic binders. This paper seeks to confidently prove that PWA can be used to accurately determine the efficacy of starch binders both alone and in conjunction with bentonite. The role of bentonite as a binder for iron ore concentrate is not only to hold agglomerates together during high temperature operations. But during pelletization it can also mitigate many times its own weight in water. This water absorption capacity aids in retarding the growth rate of pellets, as faster growing pellets tend to be weaker. The value of this water absorption, known as plate water absorption (PWA), is used as a metric to determine the strength and quality of the resulting pellets by industrial pelletizing facilities. As new low silica binders seek to replace bentonite, they too must take on the role of moisture mitigation. This study has shown that starches with lower water absorption capacities tend to have lower compressive strengths. As the water absorption capacity increases so too does the compressive strength. When using only starch, higher absorption capacities lead to lower compressive strengths of pellets exposed to elevated temperatures. When bentonite is used in conjunction with starch, higher water absorption mixtures do exhibit an increase in strength when heated.     

Recovery Improvement of Fine Magnetic Particles by Floc Magnetic Separation

The performance of floc magnetic separation (FMS) has been compared with wet high-intensity magnetic separator (WHIMS). This study was performed on low-grade iron ore slime contained 59.58% Fe with 4.57% silica and 3.78% alumina. Detailed characterization data indicated that a substantial amount of the slime was below 20 µm in size. Beneficiation studies indicated that the FMS process is effective to recover fine hematite and goethite particles, compared with the conventional magnetic separation. In conventional magnetic separation, the extent of the fluid drag force exceeds the magnetic force exerted on ultrafine particles. Thus, ultrafine magnetic particles were usually not recovered effectively by magnetic separators, resulting in the loss of valuable ultrafine slime particles. The FMS process significantly increases the magnetic force on the ultrafine iron ore in the form of hydrophobic flocs in a magnetic field, thus the ultrafine particles can be picked up effectively as magnetic concentrates. The FMS process improved the Fe recovery from 37.35% to 79.60%.     

Brazilian Iron Ore and Production of Pellets

Brazil is the second-largest producer of iron ore in the world. Brazilian richer superficial deposits are composed of brittle material with fine texture and significant amounts of fines are generated during mining and transport. Another type of ore found in this country is the itabirites that have lower iron contents. Beneficiation and concentration steps are required to prepare these materials for the pelletizing process. A general view of Brazilian types of iron ores, mines, and mining companies is given in this work. Special attention is given to pelletizing and the influence of mineralogical characteristics of different ores on the production and final properties of iron ore pellets.     

优化球团原料的配矿

为了获得低成本、质量好的球团矿产品,以两种铁精矿粉（低铁高硅磁铁矿和高铁低硅磁铁矿）和一种膨润土为原料,以生球落下强度、抗压强度以及焙烧后成品球团抗压强度为评价指标,在相同造球工艺和膨润土加入量的条件下,研究两种质量不同的铁精矿混合配料造球对球团性能的影响。研究表明,随着低铁高硅矿配比的增加,生球落下强度、抗压强度以及焙烧后成品球团抗压强度均随之降低。通过优化配矿,当低铁高硅矿配比达40%时,生球的落下强度达到3次以上,抗压强度达20N以上,焙烧后抗压强度为3850N,完全满足生产要求。     

Study of Organic and Inorganic Binders on Strength of Iron Oxide Pellets

Bentonite is a predominant binder used in iron ore pelletization. However, the presence of a high content of silica and alumina in bentonite is considered undesirable for ironmaking operations. The objective of this study was to identify the alternatives of bentonite for iron ore pelletization. To achieve this goal, different types of organic and inorganic binders were utilized to produce iron oxide pellets. The quality of these iron oxide pellets was compared with pellets made using bentonite. All pellets were tested for physical strength at different stages of pelletization to determine their ability to survive during shipping and handling. The results show that organic binders such as lactose monohydrate, hemicellulose, and sodium lignosulfonate can provide sufficient strength to indurated pellets.     

Development of fluxed micropellets for sintering utilising iron oxide waste fines

Abstract

Ultrafine iron oxide wastes such as slime, blue dust and Linz–Donawitz (LD) converter sludge have very limited use in sintering of iron ore due to their excessive fineness (?50 μm). Pelletisation of these ultrafine materials for use in blast furnace involves high temperature curing, which is a highly energy intensive process. Briquetting of LD sludge requires costly binders and contains high moisture, which creates problem at high temperature of the downstream process. In order to alleviate these problems, the current study has developed a process for preparing micropellets of waste iron oxide fines (2–6 mm size) without using any binder. The strength of the micropellet has been increased by a novel CO₂ treatment process at room temperature. Developed micropellets exhibit very suitable drop strength (125 Nos), tumbler properties and cold compressive strength (～9 kg/pellet) to withstand cold handling. Low lime containing micropellets have the possibility of being used as a mixed material in usual sinter making, and high lime containing micropellets may be exploited for making super fluxed sinter that can be used as synthetic flux in the basic oxygen furnace process towards the formation of low melting oxidising slag at the early stage of blow.     

Does the Zeta Potential of an Iron Ore Concentrate Affect the Strength and Dustiness of Unfired and Fired Pellets?

We show how pelletizing additives affect the zeta potential, sedimentation and agglomeration behavior of a hematitic iron ore concentrate. When the additives stabilized the particle–water system—indicated by higher zeta potential, higher total suspended solids content and denser settled sludge—pellet strength increased and dustiness decreased. Conversely, when the additives destabilized the particle-water system—indicated by lower zeta potential, lower total suspended solids content and rarer settled sludge—pellets became weaker and dustier. Specifically, our results show that problems related to starch binders can be resolved using carefully selected dispersants, and starch-dispersant mixtures are better pellet binders than starch alone.

In general, our results suggest that sedimentation and zeta potential tests may be effective techniques for understanding pellet–water–binder systems; organic dispersants are good alternatives to bentonite for making low-silica binders; and understanding surface properties and water chemistry of the balling feed is necessary to understand its agglomeration behavior. We believe that understanding the interactions between the balling feed minerals, pore water, and binder will become more important as balling feeds become finer and process waters more complex.     

Beneficiation of Low-grade Iron Ore Fines by Using a Circulating-type Air Classifier

ABSTRACT

The current beneficiation study examines the potential for separating ultrafine low-grade iron ore materials using a circulating-type air classifier. Statistical analysis using Response Surface Methodology (RSM) was implemented for optimization of the separator critical processing parameters to achieve sharp separation at a cut size as fine as 20–38 µm. Results demonstrated that it was possible to achieve a separation of about 9.21% lean grade ultrafine content with a size cut of ~d₅₀ 20 µm through a single-stage application.     

利用印度赤铁矿造球的工艺试验

针对100%印度赤铁矿生产氧化球团的可行性问题,对印度赤铁矿造球工艺参数进行了试验研究。在微型球团矿焙烧模拟系统中,通过模拟链箅机—回转窑生产工艺,采用正交试验的方法,得出:经细磨后的印度赤铁矿小于0.075 mm的矿粉应达到65%以上;配加膨润土的比例为1%左右;按照试验得出的干燥段和预热段工艺参数,实现100%印度赤铁矿造球是完全可行的。     

铁矿球团用有机黏结剂研究进展

 随着钢铁行业绿色低碳转型,使用有机黏结剂替代膨润土已经是铁矿球团工序提质降耗的必然趋势。然而,有机黏结剂彻底替代膨润土的技术壁垒仍未突破,严重限制了其在工业生产中的广泛应用。有机黏结剂的黏结效用也是控制球团强度的关键因素,研究其在球团生产中的作用机理对提高球团强度以及开发具有国内知识产权的新型有机黏结剂意义重大。通过总结有机黏结剂在铁矿球团中的研究进展,旨在为其在中国钢铁行业的广泛应用以及新型有机黏结剂的研发工作提供理论指导与试验依据。在介绍理想有机黏结剂分子结构模型的基础上,揭示了4种常见有机黏结剂的结构及特性。重点讨论了黏度和吸水性对有机黏结剂黏结效用的作用机理,有机黏结剂的高黏度特性能够调节球团颗粒间液桥黏滞力大小,从而显著提高生球强度;吸水性是有机黏结剂调控生球自由水含量的重要特性,只有在最佳吸水率下,才能获得强度较高、粒径均匀的生球。总结了有机黏结剂的常见优缺点,其主要优点是微量高效、烧失量大、基本不影响球团铁品位,缺点是生产球团矿缺乏渣相固结而强度不足。分析了优化原料粒度组成、添加含硼化合物及分散剂等强化有机黏结剂球团生产的调控手段,并展望了有机黏结剂未来的发展方向。     

Application of Modified Humic Acid (MHA) Binder in the Pelletizing Of Fluxed Hematite Concentrate

Modified humic acid (MHA) binder consists of high molecular weight organic molecules and inorganic part. It is extracted from lignite coal with sodium hydroxide and used in pelletization of iron ore concentrates. Our previous study shows that MHA binder is also a potential binder instead of bentonite for pelletizing of fluxed hematite. For evaluating the use of MHA binder in pelletization of fluxed hematite, pelletizing tests were conducted to optimize parameters, such as dose, firing temperature and time. The results show that the qualities of green/dried balls with 0.6 wt% MHA binder are equal to or even better than that of 0.66 wt% bentonite pellets, and that both are much higher than the minimum requirements of the pellets’ strengths. The compression strength of fired pellets also suggested that MHA binder is promising to completely replace bentonite in pelletizing of fluxed hematite concentrate. However, the abrasion rate of the fired pellets with MHA binder is slightly higher than that of bentonite pellets.     

Innovative Development on Agglomeration of Iron Ore Fines and Iron Oxide Wastes

In steel industry and in mines, a significant amount of ultra-fines waste iron oxides and iron ore fines is generated. Utilizations of these fines are required to reduce the environmental hazards and conserve the natural resources. Some of these fines are normally used in sintering practice. However, sintering has a limitation of accepting ultra-fines materials. Pelletizing can use ultra-fine iron oxides. However, suitable technology is required for preparation of good quality pellets. Some of the fines, viz. blast furnace (BF) flue dust, Linz Donawitz (LD) converter sludge etc., are not suitable due to their high alkali and Zn content. Some other material like slime is not considered to be suitable in normal pelletizing practice, because of its high alumina and silica content and excessively fine size. On the other hand mill scale and blue dust have poor green bonding property. Therefore, suitable technologies are required to be developed for their utilization/recycling. This paper discusses the various technologies developed such as (i) developing flux for basic oxygen steelmaking process, (ii) improved pelletizing practice for better reducibility, lower reduction degradation and replacing bentonite binder, and (iii) special quality sinters for improving micro-fines utilization. These technologies may have very good application potential.     

球团配加膨润土实验室及工业试验研究

在实验室测定了1号、2号膨润土与现场用膨润土的理化性能,通过造球对比实验,确定了1号、2号膨润土的适宜配比,分析了其对球团铁品位及低温还原粉化性能的影响.在此基础上进行了带式焙烧机半工业性投笼试验及工业试验.试验表明,1号膨润土适宜配比不小于1.9%,2号膨润土适宜配比大于1.1%;配加1号膨润土时球团铁品位比基准期降低了0.38个百分点,配加2号膨润土的铁品位比基准期提高了0.18个百分点;基准期成品球团低温还原粉化性能比试验期好.     

碱度对熔剂性球团生球性能的影响

 熔剂性铁矿球团具有优良的高温冶金性能，是高炉炼铁的优质炉料。为探明生产熔剂性铁矿球团时碱度对生球性能的影响规律，以某钢厂赤铁精矿为原料，通过添加石灰石粉调节碱度，进行了造球及生球干燥特性试验研究。结果发现，提高碱度，生球落下强度呈提高趋势，抗压强度变化不明显，适宜膨润土配比略有下降，生球爆裂温度明显提高，生球干燥速率则没有明显变化。与基准自然碱度（R＝0.14）相比，当碱度提高到0.6以上时，适宜膨润土配比由1.2%下降到1.1%，生球爆裂温度提高近50 ℃以上。     

攀成钢10 m2竖炉球团喷加转炉污泥的工业试验

本文介绍了攀成钢用转炉污泥浆代替竖炉造球添加水的工业试验。在10m^2竖炉球团造球盘喷加转炉污泥浆后显著改善了生球质量和成品球质量，降低了膨润土消耗，试验结果表明：用转炉污泥浆取代造球添加水，能改善和提高生球和成品球某些质量指标。在润磨工艺条件下，膨润土配比可降低30％-50％，效益十分显著。     

Humic Substance-based Binder In Iron Ore Pelletization: A Review

Due to the reducing ability and bonding effect, a humic substance-based binder has been added into iron ore pellets, both as a reductant and a binder. However, humic substance-based binders were not commonly used in pelletization since some pelletizing results indicated they were not as good asbentonite or other binders. Thus, there were few detailed investigations using humic substance-based binders in pelletization before the 1980s. Funa, which is a type of humic substance-based binder extracted from lignite, was successfully invented and applied in cold-bonded pellets in China. Since the organic fraction in the humic substance-based binder is burnt away during heating, leaving no contaminant in pellets and improving the iron content of the pellets, humic substance-based binders were also gradually utilized in oxidized pellets. On the basis of Funa binder research, the extracting procedure of a humic substance-based binder was modified, and a composite binder named Modified Humic Acid (MHA)was prepared for oxidized pellets, especially for making Vanadium-Titanium (V-Ti) magnetite pellets, and achieved qualified V-Ti magnetite oxidized pellets in industrial testing. The behaviors of humic substance-based binders in wet balls, dry balls and fired balls were well investigated. Moreover, MHA binder was gradually tested in a lab for pelletization of several other types of iron ore concentrates, such as magnetite from different districts, specularite and fluxed hematite, and good quality pellets were obtained. A review of the development of a humic substance-based binder and its characteristics, preparing method, and behaviors in pelletizing were considered in this paper.     

Al2O3对铁矿烧结球团及高炉冶炼的影响

摘要：随着中国钢铁行业迅猛发展,高品位铁矿石储量减少,进口铁矿石以及国内自产铁矿石中Al2O3含量逐年增加,将会给烧结矿、球团矿生产及高炉冶炼带来一系列不利影响。介绍了不同赋存状态的Al2O3的形成及形貌特征,总结了Al2O3赋存状态改变以及含量增加对烧结矿、球团矿和高炉冶炼的影响规律及机制,Al2O3赋存状态、含量改变会对烧结矿、球团矿的成品矿质量、矿物组成和冶金性能产生影响,同时Al2O3含量的增加会对高炉炉渣的熔化性、黏度和脱硫产生不利影响。基于以上内容,认为可通过改善选矿过程、烧结球团制备过程和高炉冶炼过程3个环节来减少Al2O3对烧结球团、高炉冶炼的影响。     

鞍钢自产铁精矿合理使用研究

对鞍钢常用4种铁精矿的烧结基础特性进行了试验研究,在此基础上,采用最优试验设计方法,建立了烧结合理配矿的统计模型,给出了烧结获得最佳和最差烧结指标值时的各种矿的定量搭配关系,提出了鞍钢烧结合理配矿方案.优化配矿工业试验结果表明:烧结技术经济指标有不同程度改善,尤其是烧结矿的粒度组成改善、固体燃耗降低;提出并确定了球团配加铁精矿A的优越性,配加铁精矿A后,皂土配比降低8.69%,转鼓强度提高0.35个百分点.