Iron Ore Pellet Dustiness Part II: Effects of Firing Route and Abrasion Resistance on Fines and Dust Generation

Iron ore pellets abrade during their production and handling, which lowers product quality and leads to dustiness issues. Pellets were collected from a variety of plants (operating either Straight-Grate (SG) or Grate-Kiln (GK) furnaces) to understand whether furnace type affects fines and dust formation. Results showed that pellets fired in SG furnaces were less abrasion-resistant (3.5 × lower) than pellets fired in GK furnaces. Concurrently, laboratory pellets were prepared using various ores, binders, and firing temperatures. These were tested to understand the relationship between abrasion index and dustiness. AI was observed to range from 1 to 14%. Dustiness, determined via AI and size distributions of abrasion progeny, ranged from 0.2 to 1.6%. For AI greater than 5%, AI can be used to indicate potentially high levels of dust. For AI less than 5%, there was a poor correlation between AI and dustiness. This was explained by the observation that as AI decreased, the abrasion product fineness increased. The results from parts I and II of this investigation suggest that material loss and levels of pellet dustiness may be significantly affected by pellet quality up to a certain point. Poorly fired pellets will be dusty during handling and transportation, while well-fired pellets will generate less – but finer – material as their quality improves. This could lead to little observed changes in dust generation over a wide range of pellet quality. Dust generation at each site would then depend on the quantity of material produced and their extent of handling.     

Iron Ore Pellet Dustiness Part I: Factors Affecting Dust Generation

Iron ore pellets abrade during handling and produce dust. This study was conducted to determine what factors affect pellet dustiness, and whether dustiness can be related to the abrasion index. Factors studied included bed depth within a straight grate furnace; pellet chemistry; firing temperature; coke breeze addition; and tumble index. Abrasion indices for all pellet samples ranged from 1.9–5.0% (20 samples) and from 7.1–27.5% (5 samples). Pellets were dropped in an enclosed tower, which enabled the collection of airborne particles generated during pellet breakdown. The quantity of airborne particles generated by each pellet type was 10–100 mg/kg-drop, or 50–500 mg/kg over five drops through the tower. Pellet dustiness was predominantly affected by pellet chemistry and by pellet firing temperature. Results showed a nearly 21% increase in dustiness for every percent decrease in firing temperature – this was based on a typical firing temperature of 1280°C. Pellet dustiness was regressed to the pellet abrasion index (for AI < 5%), which yielded a correlation coefficient of 0.22. These results show that, although AI is one of the best indicators of fired pellet quality and can indicate high levels of dust, it could not explain the dustiness of good quality pellets.

The second paper (Iron Ore Pellet Dustiness Part II) explains the relationship between AI and dust for good-quality pellets; and compares fines generation between pellets fired in Straight-Grate (Traveling Grate) and Grate-Kiln furnaces.     

A New On-Line Method for Predicting Iron Ore Pellet Quality

The Abrasion Index (AI) describes fines generation from iron ore pellets, and is one of the most common indicators of pellet quality. In a typical pellet plant, dust is generated during the process and then captured. Can the dust be measured and used to predict AI? In this paper, the feasibility of using airborne dust measurements as an indicator of AI is investigated through laboratory tests and using data from a pellet plant. Bentonite clay, polyacrylamide and pregelled cornstarch contents, and induration temperature were adjusted to control the abrasion resistance of laboratory iron ore pellets. AI were observed to range from approximately 1% to 12%. Size distributions of the abrasion progeny were measured and used to estimate quantities of PM₁₀ (particulate matter with aerodynamic diameter less than 10 µm) produced during abrasion. A very good correlation between AI and PM₁₀ (R² = 0.90) was observed using the laboratory pellets. Similarly, a correlation was observed between AI and PM measured in the screening chimney at a straight-grate pelletization plant in Brazil, with an R² value of 0.65. Thus, the laboratory and industry data suggest that measuring dust generation from fired pellets may be an effective on-line measurement of pellet quality. The data also showed that particulate emissions from pelletization plants may be directly affected by AI.     

链箅机--回转窑氧化球团热工操作分析

论述了采用链苒机-回转窑工艺生产氧化球团热工系统的基本特点和基本热工制度、风流匹配；分析了生球的在链算机内进行干燥、预热及氧化的各段合理温度要求、调节温度故障的措施和有效预防破坏性高温停机的对策；探讨了干球在窑内不同部位的焙烧温度、火焰操作以及窑头出现止压的预防和控制办法。同时，对采用2段鼓风式环冷机冷却时，热球达到允分氧化与完全冷却的风温、风世的匹配进行了优化。     

The Effect of Calcined Colemanite Addition on the Mechanical Strength of Magnetite Pellets Produced with Organic Binders

Iron ore pellets must have sufficient mechanical strengths against degradation in all stages of pellet production. Low strength is also a problem for product pellets since they abrade during transportation to the reduction furnaces. The use of a binder is necessary to provide sufficient strength to the pellets and for better operation and handling of pellets. Bentonite is the standard binder in the industry; however, it is considered an impurity due to its acid oxide contents. Organic binders have been tested for many years as alternative binder to bentonite. They have been found to give sufficient wet pellet properties. However, they failed to provide sufficient strength to the preheated and fired pellets due to lack of slag bonding. It has been assumed that one possible effective method to improve the preheated and fired pellet strengths is addition of a slag-bonding constituent. In this study, calcined colemanite was added to the pellet feed to overcome the lower strength problem encountered with organic binder use. The strength of pellets produced with organic binders and calcined colemanite alone and in combination was comparatively studied against the strength of pellets made with standard bentonite binder in magnetite concentrate pelletizing. The results showed that addition of calcined colemanite into the pellet mixture improved the preheated and fired pellet strengths of pellets produced with organic binders.     

马钢链箅机-回转窑氧化球团试验研究

基于马钢球团原料条件,在模拟试验装置中研究了链箅机-回转窑氧化球团生产的料层高度、鼓风干燥热风温度、抽风干燥热风温度、预热热风温度和回转窑焙烧等工艺参数。在配用40%(质量分数)赤铁精矿时,采用最佳链箅机-回转窑工艺参数条件下,获得了冶金性能良好的成品球团矿,主要指标为:单球抗压强度3 113 N,转鼓强度93.16%,抗磨指数2.00%,w(TFe)63.64%,w(FeO)1.62%。     

100万t链箅机和回转窑设备改造实践

介绍了宣钢炼铁厂为降低生产成本改善炉料结构,为替代昂贵的外购球团矿而进行的一期链箅机和回转窑球团生产线改造性大修。此次大修改造重点是要解决链箅机和回转窑生产线链算机、回转窑、环冷机工艺设备及自动化上存在的问题,改造后三大主机的设备作业率达到了100％,在保证球团矿质量的前提下,球团矿日产水平稳定在3000t以上。经过改造和生产实践加深了链箅机和回转窑球团工艺设备的了解,为后续稳定生产及二期工程改造积累了大量宝贵的经验。     

基于非线性主成分分析与自适应小波神经网络的球团质量预测模型研究

在链篦机-回转窑法球团生产过程中,成品球团的质量与系统的热工制度的控制和参数调节密切相关。鉴于系统的过程变量多、滞后性大、周期性长的特点,提出并建立了基于非线性主成分分析与自适应小波神经网络的球团质量预测模型,并用实例证明,该模型在质量预测中与传统的BP神经网络模型相比有较好的效果。     

高配比镜铁矿的生产实践

为了降低漓铁8 m2竖炉生产成本,配加30%(质量分数)的镜铁矿进行球团生产。针对镜铁矿焙烧温度高的特点,为了有效提高成品球的抗压强度,对漓铁竖炉球团生产线的燃烧室及水梁等进行了改造,在配加镜铁矿的情况下使成品球能够满足高炉的要求。在焙烧温度为1 250℃的条件下,成品球团矿抗压强度可达到2 741 N/个,表明添加了镜铁矿后的球团矿指标仍然达到了国家标准。     

改善竖炉球团矿质量的研究

为优化大冶铁矿球团生产工艺参数,研究了钠化改型膨润土和润磨技术对球团生产的影响。结果表明,膨润土钠化改型后,有利于生球强度的提高和焙烧球强度的改善;润磨技术可以提高生球强度,降低膨润土用量,改善球团矿质量,是提高大冶球团矿产、质量的一项有效技术措施。     

邯钢200万t/a链篦机-回转窑投产初期生球爆裂的原因及解决方案

介绍了邯钢200万t/a球团生产线达产过程中出现的生球爆裂问题及解决方法和实际效果.     

莱钢型钢链篦机 回转窑智能控制系统及其应用

介绍了莱钢型钢炼铁厂120万t/a链篦机-回转窑智能控制系统,包括:物料配比实时动态控制,链篦机温度自优化控制,链篦机-回转窑-环冷机三机速度联调控制以及回转窑温度模糊控制等。实际运行效果表明,该控制系统结构合理,性能稳定,为球团生产线的高产、稳产和确保产品质量发挥了重要作用。     

改善鞍钢球团矿冶金性能的研究

对带式机酸性球团矿添加含MgO添加剂的造球、焙烧和冶金性能研究表明,在带式机目前焙烧工艺制度条件下,MgO／SiO2比值在0．45～0．6时,球团矿抗压强度高于2500N／个,还原膨胀率大幅度降低;随着MgO／SiO2比值的升高,低温还原粉化率RDI＋3.15、RDI＋6.3提高;900℃还原度提高。当MgO／SiO2比值为0．45时,球团矿的综合冶金性能较好。     

稳定球团生产的若干设计问题

就链箅机-回转窑球团生产线设计中,各种贮仓和缓冲仓、各种旁通设施、关键设备进排料口的紧急出口以及风流系统的各种放散阀和兑冷热风阀的功能和设置进行了讨论。这些设施是稳定生产、避免发生重大设备事故、提高作业率、改善产品质量所必备的调节手段。     

鞍钢球团生产工艺的发展与高炉炉料结构的进步

介绍了鞍钢球团生产系统从"七五"到"十五"的技术改造(从隧道式焙烧机方团矿的生产到带式焙烧机和链箅机-回转窑的全面推广),通过引进和开发球团生产新技术,使球团矿技术经济指标明显改善.高炉从使用单一的自熔性烧结矿到现在的高碱度烧结矿搭配酸性球团矿的合理炉料结构,高炉技术指标实现了质的飞跃.     

链篦机-回转窑铲料板的改造

链篦机-回转窑氧化球团生产线铲料板是把链篦机篦床上的料球导入回转窑的关键部件，其使用效果对整个链篦机-回转窑氧化球团生产至关重要。本文介绍了莱钢通过链篦机铲料板改造，彻底解决了制约链篦机-回转窑生产的一大难题。     

新兴铸管公司链箅机-回转窑球团生产线的改造及效果

介绍了新兴铸管球团部2007年元月对链箅机-回转窑球团生产线进行的技术改造,包括对原料系统、造球系统、筛分系统、焙烧系统等进行的完善。配合工艺设备改造,该厂还在生产操作方面进行了调整。最终,取得了球团矿产质量提高,能耗和膨润消耗降低的良好效果。     

煤粉燃料球团生产中链篦机结渣物成因分析

对以煤粉为燃料的链篦机-回转窑法铁矿球团生产中链篦机预热段生成的结渣物进行了XRD、显微结构及扫描电镜能谱分析,发现其矿相组成主要是铁氧化物以及少量含镁铝固溶体。为查明链篦机结渣物形成机理,开展了温度及煤灰残碳量对结渣物形成影响的模拟焙烧试验。结果表明,焙烧物的物相中有含残碳的煤灰,其物相组成、显微结构与实际结渣物组成物相类似,证实链篦机喷煤补热燃烧过程中煤灰中的残碳可使结渣混合物体系生成含亚铁相的硅铝酸盐类低熔点化合物,是导致链篦机结渣物形成的主要原因。     

邯钢200万t氧化球团的试生产

介绍了邯钢第1条200万t／a链算机一回转窑氧化球团生产线在试生产期间的原料条件和生产情况；分析了生产中遇到的难题；提出了调整设备和工艺的方法。经调整后，球团矿的绝大部分指标均达到国家标准，高炉在使用自产球团矿期间炉况顺行、焦比降低、产量增加。该生产线实现了投产后40天快速达产的目标。     

基于减法聚类ANFIS的链-回-环球团热状态控制模型

 链箅机-回转窑氧化球团热工制度是影响球团矿产质量指标及生产能耗的关键因素,但由于其工艺特点,热工过程状态参数和操作参数多、设备的耦合性强、操作变量与被控变量关系复杂,难以采用精确的机理模型进行控制。在分析链箅机-回转窑氧化球团热工过程物料流及热风流特点的基础上,建立了基于自适应神经模糊推理系统（ANFIS）的热状态控制模型。采用减法聚类划分模型输入空间,采用最小二乘法及梯度下降法对T-S模型进行辨识。结合VC++和MATLAB混合编程的方法,开发了链箅机-回转窑氧化球团热状态控制指导系统,实现了模型的在线计算,以及操作变量的实时控制指导。采用国内某球团厂的生产数据对模型进行了仿真,模型的平均相对误差均小于5%。