含碳球团包衣防护制备海绵铁的研究
文献类型：学位论文
| 作者 | 申明辉 |
| 学位类别 | 硕士 |
| 答辩日期 | 2013-05-01 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 叶树峰 ; 魏连启 |
| 关键词 | 含碳球团 海绵铁 再氧化 涂层防护 固相反应 |
| 其他题名 | Study on the Preparation of Sponge Iron by Pellets Contain Carbon Based on Coating Protection |
| 学位专业 | 材料工程 |
| 中文摘要 | 含碳球团直接还原制备海绵铁的工艺中存在的后期“再氧化”，造成金属化率的降低，要实现反应后期还原气氛的严格控制会导致反应器造价昂贵，生产效率较低，这是目前铁矿含碳球团生产直接还原铁的瓶颈之一。本研究就含碳球团直接还原工艺中防止海绵铁“再氧化”所采取的工艺进行了较为系统的调研，结合实验室在钢铁高温防护涂层方面多年研究工作的积累，制备一种价格低廉的陶瓷料浆，通过该陶瓷料浆在含碳球团表面的动态致密化实现对单个含碳球团制备海绵铁工艺过程中的动态防护。 本文研究了含碳球团制备海绵铁过程中的“自还原”及“再氧化”现象，依据球团反应过程中球团与炉气相互作用过程，提出了含碳球团包衣层设计原则和功能要求，根据相图及固相反应原理，选择功能组分和辅助组分通过机械混合法制备了含碳球团包衣防护用陶瓷料浆，研究了其对反应初期表层“碳烧损”的影响、对海绵铁初始氧化皮致密化的效果、对海绵铁后期“再氧化”的防护效果、所形成的致密防护层从海绵铁基体上剥除的效果；并对比分析了有无包衣防护时含碳球团金属化率的变化，并研究了包衣防护涂层与含碳球团表层还原产物相互作用形成致密防护层的反应过程以及包衣防护的作用机理。 含碳球团包衣防护的实验结果表明：将0.25mm厚的 Al2O3-MgO-SiO2料浆包覆含碳球团表面可减缓球团入炉升温过程中的表层碳烧损；包衣防护使得海绵铁疏松多孔的氧化皮结构改变为相对致密且均匀的防护层，该防护层可以在高温下有效减缓氧化性炉气对海绵铁的再氧化，与无包衣防护含碳球团相比，普通马弗炉中包衣防护工艺的最高金属化率相比较无包衣防护提高了59.5%；含碳球团“自还原”过程中表层还原产物FeO在高温下通过塑性变形进入包衣涂层并包裹其中的功能组元MgO颗粒，两者发生固溶反应生成主要成分为(MgO)0.239(FeO)0.761的致密层，该致密层可进一步氧化生成内层为“针状”的Fe2.95Si0.05O4，外层为“补丁”状MgFe2O4尖晶石结构的防护层，防护层的总厚度为0.20mm，且可通过挤压形变的方式使其从塑性的海绵铁基体上完整的剥除，这样既可以减缓海绵铁在常温下的储存和运输过程中的氧化，同时保证了海绵铁的品质和后续工艺的顺利进行。 |
| 英文摘要 | Sponge iron tends to be re-oxidized by high temperature furnace gas during the later stage of direct reduction of pellets contain carbon, resulting in lower metallization ratio. In order to solve this problem, strict contral of reducing atmosphere in furnace is necessary, which leads to high expense of reactor and low production efficiency. Anti-oxidation of sponge iron is currently one of the most difficult problems in the production process of directly reduced iron. In this study, the anti-oxidation techniques for direct reduction of pellets contain carbon were systematically reviewed. Combining with accumulated research experience for many years in the field of high temperature anti-oxidation coating for steel, we developed one kind of cheap ceramic slurry as protective coating. Dynamic densification of prepared ceramic slurry on the surface of the pellets contain carbon can maintain good reduction atmosphere in the pellets and protect reduced sponge iron from re-oxidation. The phenomenon of "self-reduction" and "oxidation" in the process of direct reduction of pellets contain carbon was studied. The principle of designing coating slurry and the functional requirements for coating protection were proposed based on the study on the interaction between carbon pellets and the furnace atmosphere. On the basis of phase diagram and solid phase reaction principle, functional components and auxiliary components were mixed to produce ceramic coating slurry by mechanical mixing. The influence of protrective coating on the carbon loss, densification degree of oxidation layer, effect of anti-oxidation, metallization ratio and the removal effect of the densification coating from pellets were systematically investigated. The reduction mechanism and the anti-oxidation behavior of pellet with coating were also investigated in this paper. The experiment results showed that with coating the pellet containing carbon with 0.25 mm thick of Al2O3-MgO-SiO2 ceramic slurry as a coating layer. Pellet containing carbon with coating protection process slows down the carbon loss of pellet during heating to reduction temtemper,，the coating produced a dense protective layer which maintained a reduction atmosphere inside the pellet and prevented the sponge iron from re-oxidation by high temperature oxidation gas. Our results also show that in oxygen-rich environment the metallization ration of pellet with the protection of coating layer can be up to 80%, which is 59.5% advance of that without the protection coating layer. There are three stage during the formation of dense protective layer. Firstly, Fe2O3 was reduced to FeO, which could penetrate into the coating layer and encase functional MgO particles through plastic deformation at high temperate. Then, FeO and MgO were transformed to a dense layer of (MgO)0.239(FeO)0.761 through solid solution reaction. This dense layer can be oxidized to 0.20 mm thick of protection layer with a hybrid layer structure, which is constructed by “acicular” Fe2.95Si0.05O4 in inner side and “patchy” MgFe2O4 in outer side. After the reaction, the protection layer can be easily removed from formed sponge iron by extrusion deformation. This can not only slow down the oxidation of sponge iron at room temperature in the process of storage and transportation, but also ensure the quality and the subsequent process of sponge iron smoothly. |
| 语种 | 中文 |
| 公开日期 | 2014-06-26 |
| 页码 | 75 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/8342]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 申明辉. 含碳球团包衣防护制备海绵铁的研究[D]. 中国科学院研究生院. 2013. |
入库方式： OAI收割
来源：过程工程研究所
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