【作者】 张道远；

【导师】 白国华； 张元波；

【作者基本信息】 中南大学 ， 矿物加工工程， 2011， 硕士

【摘要】 随着我国铁矿氧化球团工业的快速发展,铁品位高、粒度细和焙烧性能良好的磁铁精矿资源供应日益紧张。因此,开发和应用新的铁矿资源已成为推动我国球团工业持续发展的新途径。镜铁矿具有铁品位高,储量高,价格低廉等优点,已引起人们的广泛关注。然而,镜铁矿普遍具有成球性差和难焙烧等缺点。针对镜铁矿存在的上述优缺点,深入研究和开发镜铁矿在铁矿球团中的应用新工艺和技术,对缓解我国铁矿资源紧张的局面具有重要意义。近年来,中南大学开发出一种新型MHA粘结剂。MHA粘结剂主要由含有大量极性功能基团的大分子有机物组成,具有低残留和热稳定性高等优点。而且,MHA粘结剂能够改善铁精矿的界面特性和成球性能。因此,开展MHA粘结剂在镜铁矿氧化球团制备中的应用研究为高效利用镜铁矿资源提供了一个新思路。本研究主要以中南大学开发的MHA粘结剂(无机膨润土作为对比)以及巴西ORP镜铁矿为原料,通过对镜铁矿进行不同方式的预处理,开展了MHA粘结剂在镜铁矿氧化球团中的应用研究。获得主要结论如下：采用湿式球磨—高压辊磨处理技术对镜铁矿进行预处理,当镜铁矿比表面积达到1609cm2/g时,采用1.0%MHA粘结剂的生球落下强度为3.7次／(0.5m),抗压强度12.4N/个,爆裂温度330℃；与1.0%MHA粘结剂相比,采用2.0%膨润土的生球落下强度为3.9次／(0.5m),抗压强度13.6N/个,爆裂温度365℃。采用1.0%MHA粘结剂的镜铁矿球团适宜的预热焙烧制度为：预热温度980℃、预热时间10min、焙烧温度1280℃和焙烧时间10min。在最优条件下,1.0%MHA预热球团的抗压强度为401N/个,焙烧球团抗压强度为2700N/个。与2.0%膨润土球团相比,1.0%MHA球团的高温冶金性能较好,TFe品位提高了0.85%。MHA粘结剂与镜铁矿表面的吸附作用表明,MHA粘结剂与镜铁矿颗粒发生明显的吸附作用,吸附量的大小主要与镜铁矿比表面积、MHA与铁矿质量比、吸附时间等因素的有关。MHA粘结剂的吸附改善了镜铁矿表面亲水性。MHA粘结剂在镜铁矿球团预热焙烧过程中的行为研究表明,MHA粘结剂主要有两个方面的作用：(1)燃烧放热。MHA粘结剂中有机元素在球团高温焙烧过程中发生燃烧,释放部分热量,提高了球团内部温度,有利于球团固结；(2)还原作用。在镜铁矿球团焙烧过程中,MHA粘结剂中的还原物质与铁矿颗粒发生还原反应,球团内部分Fe2O3先被还原为磁铁矿或浮士体,随着温度的升高和时间的延长又被氧化为次生赤铁矿,促进了Fe2O3晶粒的长大和固结。MHA粘结剂的加入,改变了镜铁矿球团的结晶过程,有利于改善镜铁矿的高温焙烧性能,获得高强度的成品球团矿。更多还原

【Abstract】 With the development of iron ore oxidized pellet industry, the magnetite concentrates characterized by high TFe grade, fine granularity and good roasting performance become more and more shortage in China. Therefore, the development and application of new iron ore resources has provides a new approach for the sustainable development of pellet industry. Specularites are now invoking more and more interests because of their many advantages such as low price, great reserves and high TFe grade, although they are characterized by poor ballability and bad high-temperature reactivity. The reasonable utilization of specularite resources, hence, can play significant role in lightening the shortage of iron ores. Recently, one modified humic substances based binder, named MHA binder, have been patented and proved to be an effective binder for iron ore pellets in China. The MHA binder mainly comprising functional organic polymer is characterized by low residue, low price and good thermal stability. And the presence of MHA binder onto surface of iron ore particles is able to modify the interfacial characteristics of iron ores and improve the green pellet strength. Therefore, the research on application of MHA binder in oxidized pellet preparation from specularite concentrates provides us a novel method and a newdirection for Effective use of specularite.Compared with inorganic bentonite binder, the specularite oxidized pellets are produced by adopting as the MHA binder developed by central south university and Brazilian ORP specularite treated by different pretreatment methods as raw materials. The research results are concluded by the following:The specific surface aera of specularite 1609 cm2/g can be obtained when the process of wet ball grinding combined with high pressure grinding technology is adopted. Under the condition of the dosage of MHA binder 1.0%, balling time 15 min, the moisture wet green pellets 8.0%, the drop strength, the compression strength and the thermal crack temperature of green pellets are respectively 3.7 times/0.5m,12.4 N/P and 330℃. Comparatively speaking, the drop strength, the compression strength and the thermal crack temperature of the green pellets balled with 2.0% bentonite are respectively 3.9 times/0.5m,13.6 N/P and 365℃.Under the optimal experimental conditions of the dosage of MHA binder 1.0%, preheating temperature 980℃, preheating time 10 min, roasting temperature 1280℃and roasting time 10 min, the compression strength of the preheated pellets and the compression strength of the roasted pellets is 401 N/P and 2700 N/P, respectively. Compared with the MHA binder pellets, the compression strength of preheated pellets and the compression strength of the roasted pellets with 2.0% bentonite is 445 N/P and 2709 N/P, respectively. The qualities of the two kinds of pellets are almost close to each other. Compared with the pellets with 2.0% bentonite, the metallurgy performance at high temperature of the pellets with 1.0% MHA binder is better and TFe grade increase by 0.85%.The adsorption experiments show that the MHA binder have a obvious adsorption on the surface of speclarite grains during specularite pelletizing. The adsorption amount of MHA binder is influenced by the specific surface area of specularite, the proportion of MHA binder to specualrite, the adsorption time and so on. Meantimes, MHA improves the surface hydrophilicity of specularite with appearance of MHA binder on the surface of speclarite.The behavior of MHA binder in specularite pellets during preheating and roasting can be involves the following two aspects. (1):combustion and releasing heat of MHA binder. The organic fraction of MHA binder is burned out during heating and partial heat is released. This is helpful to increase the temperature of the core of pellets, and to promote the induration of pellets. (2):reducing action of MHA binder. The reduction reaction of MHA binder takes place on the surface of specularite grains. Fe2O3 is reduced to magnetite or wustite firstly. Thereafter, the secondary magnetite is reoxidized to secondary Fe2O3. The preheating and the roasting processes promote the recrystallization of secondary Fe2O3 grains. Therefore, these changes in the induration process of specularite at high temperature improve the roasting properties of the pellets with MHA binder.更多还原