【作者】 何环宇；

【导师】 倪红卫；

【作者基本信息】 武汉科技大学 ， 钢铁冶金， 2010， 博士

【摘要】 随着LF精炼设备越来越广泛的应用,精炼废渣的堆弃量越来越大,由此带来的堆放占地和环境污染问题也越发凸显,因此采取有效的方式对其再利用显得非常迫切。LF精炼废渣中存在大量的与部分冶金原料成分相近的CaO、SiO₂、Al₂O₃和MgO等物质,因此将LF精炼废渣在冶金工业中进行资源化循环利用,是废渣循环利用最便捷经济的途径之一,目前已引起人们的关注。目前LF精炼废渣冶金循环利用的普遍方式是将废渣进行破碎或造球后直接返回冶金生产,由于不改变渣的化学组成,在循环过程中不可避免的存在渣中有害物质硫的循环富集的问题,易引起钢液质量的恶化。如何采取有效的再生方式去除废渣中的硫,是从本质上解决LF精炼废渣冶金资源化利用的关键和发展方向。研究LF精炼废渣冷却固化过程渣相组成及析出机理,废渣中含硫物相的组成、分布及特性,废渣再生处理去硫过程的物化机理以及再生过程废渣冶金特性的变化,可为LF精炼废渣再生循环利用提供物质特性基础,使废渣的再生去硫方式针对性的进行选取,提供废渣再生利用的有利条件并保证再生处理后废渣的冶金再利用效果,促进LF精炼废渣再生冶金循环利用技术的发展,提高精炼废渣的再生利用率,对解决大量堆存的LF精炼废渣带来的处理成本及环境污染问题有很好的理论和实际意义。本文首先通过微观检测和热力学分析手段对典型LF精炼废渣基本化学性质及渣相组成和析出机理进行了研究。LF精炼废渣的高碱度、低氧化性、高硫容量、适合的渣指数以及良好的熔化特性使得精炼废渣具有良好的在冶金工业中再循环利用的价值,但废渣硫含量远高于冶炼原材料对含硫量的要求。各物相析出顺序及分布与其熔点有关,硅酸钙类高熔点物相在凝固初期以块状物析出。铝酸钙类形成低熔点的基体相。LF精炼废渣中还存在大量的自由CaO。低碱度、高Al₂O₃含量和缓冷渣渣相种类更多、尺寸更大。利用相图及其简单三角形对应二元和三元碱度关系,可对LF精炼废渣渣相析出进行热力学分析,确定渣组成和温度对物相析出的影响以及预测析出物相的种类和数量及分布。LF精炼废渣中的硫以弥散状赋存于低熔点物相交界区域,废渣中的硫赋存相并不按照化学计量以单一组成的物相形式存在,Ca12Al14O32S是废渣中最主要的硫赋存形式,可在一个较大的硫含量浓度范围和冷却条件下析出。而废渣的碱度和成分变化时会有CaS和其它复杂硫赋存相存在。Ca₁₂Al₁₄O₃₂S是由CaS中硫离子置换12CaO·7Al₂O₃中的自由氧离子形成的。热力学计算表明,渣中a（CaS）仅为10-4的数量级,Ca₁₂Al₁₄O₃₂S就可析出成为精炼废渣主要的硫赋存相而稳定存在。LF精炼废渣的亚临界水浸出再生去硫可在物性优良的浸出剂和有利的动力学反应环境下进行,反应经过15 min已接近热力学平衡,去硫效果好,成本低。在373 K～473 K温度范围,化学反应为过程控制环节,温度>473 K时,传质过程的影响逐渐凸显,反应进入动力学控制范畴。LF精炼废渣的亚临界水浸出再生去硫过程没有氧化还原反应发生,废渣中的S2-的价态并没有发生变化,仍然是以S2-形式进入浸出液中的。在处理条件下,浸出温度为废渣亚临界水浸出再生去硫的主要热力学影响因素。废渣亚临界水浸出符合未反应核动力学模型,反应的表观活化能值很低,过程的限制性环节为水在渣粒中的内扩散环节。最后,通过对以LF再生渣为基料制备的精炼剂的冶金性能实验室热态模拟和理论计算以及现场应用表明,再生渣具有相当好的熔化特性,以再生渣为基料配制的精炼剂具有较高的光学碱度和硫容量,可达到很高的LS,脱硫速度快,反应前10 min的脱硫率已比较接近最终值,脱硫率达50%⁷0%。在现场应用中,无论低碳钢还是中碳钢,使用以LF再生渣为基料制备的精炼剂代替现场石灰渣系,其脱硫、脱氧、吸附夹杂能力以及合金收得率均得到明显提高。更多还原

【Abstract】 One of the most commonly used and most efficient methods of improving the quality of steel was ladle treatment of the metal with synthetic slag. After refining, the output of waste slag has a sharp increase, which has brought about increasing issues such as environmental pollution and resource spent. The LF waste slag has the characteristics of metallurgical resources because of the chemical composition and can be returned to metallurgical industry as raw material. For these reasons, the reuse of LF waste slag has been paid more attention for a long time.Unfortunately, in spite of its potential, the reuse of LF waste slag was not satisfied and there are only a few waste slag were returned to steelmaking process. This was due to the fact that in the refining process the slag was used as a reservoir of hazardous elements such as sulfur and subsequently used as a source material in steelmaking, the hazardous elements would pollute the steel. So the task of desulfurization to regenerate slag was considerably important before reused.But now there is not suitable method to remove sulfur from the slag, in spite of the technical obstacles, the basic characteristics of LF waste slag were not determined. The crystallized path of minerals and the incorporation of sulfur in refining waste slag during the cooling and solidification, the physical chemistry mechanisms and the changing of metallurgical characteristics during the regeneration were the research bases for the reuse of the LF waste slag. These can proffer foundation theories for the slag’s regeneration and guide the desulfurization method’s adoption and improving the technologies of reusing the waste slag. So above research works have academic and practical significance to solve the problem of environmental pollution and resource spent caused by LF waste slag.In this subject, a study regarding the typical LF waste slags with micro- and thermodynamics analytical technologies were carried out. The study indicated that the LF waste slag has favorable reuse value in steelmaking process because of the high basicity, low oxidation, high sulfur capacity and good melting characteristic, but the sulfur must be removed before reuse. The crystallized path of minerals was related to their equilibrium temperature, with the temperature drop, Calcium silicate was separated out from the slag at first and Calcium aluminates formed matrix with low melting point, and there were a lot of f-CaO in the waste slag. The amount and dimension of mineral were increased in the low basicity and high Al₂O₃ content slag. The CaO- Al₂O₃-SiO₂ ternary phase diagram and the corresponding basicity value could be used to analyze the thermodynamics equilibrium of the crystallized process of minerals, and the analyze results was very accordant to the microscopic detect results.The sulfur in the slag was existed between the low melting point minerals in a state of dispersing, and the sulfur incorporation mineral separated out from the slag was not by a single phase which was according to the stoichiometry. Ca₁₂Al₁₄O₃₂S was the uppermost sulfur incorporation mineral and it could be separated out from the slag in a broad range of sulfur content and cooling speed. There were CaS and other complicated sulfur mineral separated out when the basicity and composition changed. Ca₁₂Al₁₄O₃₂S was formed by replacing O2- in 12CaO·7Al₂O₃ with S2- in CaS, and the thermodynamics calculation indicated that Ca12Al14O32S can be easily crystallized from the slag and existed stably if only the a（CaS） over 10-4.The regeneration desulfurization reaction of LF waste slag had been done by subcritical water leaching, the results indicated that the reaction was a kind of multiphase reaction between fluid and solid, and the reaction speed and ratio were large increased in advantaged dynamics conditions which offered by the subcritical water. The reaction’s resistances were come from mass transfer or interface reaction in different temperature. At the temperature of 373 K⁴73 K, the interface reaction was the control element, and the main resistance changed to mass transfer when the temperature was up to 473 K. There has not any oxidation-reduction reaction in the process and the S2- in the slag entered into the lixivium at the same state. The primary thermodynamics influencing factor of the regeneration desulfurization reaction was temperature and the Unreacted Nucleation dynamics model could be used to characterize the desulfurization reaction. The control element of dynamics process was internal diffusion because of the low apparent activation energy value. At last, the metallurgical capabilities of the refining agent prepared with regenerated slag was researched by laboratory experimentation, theoretical calculation and production application, and the research results indicated that the regenerated slag showed goodish melting capability and the refining agent prepared with regenerated slag had high optical basicity and sulfur capacity. In the laboratary experimentation, the desulfurization reaction speed was quickly andηs approached the equilibrium value at the first 10 minute which was 50%⁷0%. In the production application, using the refining agent prepared with regenerated slag to replace lime, the effect of desulfurization, deoxygenation, inclusion adsorption and alloy recovery were all increased obviously.更多还原