【作者】 姜鑫；

【导师】 沈峰满；

【作者基本信息】 东北大学 ， 钢铁冶金， 2008， 博士

【摘要】 近年来,随着我国炼铁企业外购矿使用量的增加,以及低硅冶炼和某些特殊矿冶炼的需要,高炉渣须保证一定的MgO含量。针对此问题,本文系统地研究了含MgO原料(白云石、菱镁石等)添加到烧结或球团配料中,对烧结球团工艺及烧结矿、球团矿各种冶金性能的影响规律,并利用EPMA和X-ray衍射等现代测试技术,结合热力学原理对MgO在铁矿石及其还原过程中的赋存状态和含MgO初渣的熔化性能等进行了深入的理论分析。在此基础上,对三种炉料结构的软熔性能进行了试验研究,选择最佳的炉料结构应用于生产试验,使炼铁生产技术指标得到了显著的提高。本论文的研究工作和成果主要包括以下内容：(1)适当提高渣中MgO含量,可改善炉渣流动性,提高炉渣脱硫能力及排碱率等,炉渣中适宜的MgO含量应控制在8-10%。(2)随着烧结矿中MgO含量的提高,烧结杯利用系数和烧结矿的强度、成品率、品位随之下降,但烧结矿的低温还原粉化性能得到改善。若减少烧结配料中MgO的添加量,应采相应措施以解决烧结矿低温还原粉化率升高的问题。(3)本文定义了烧结矿的高压差温度区间。MgO含量从1.3%增加到3.0%时：R=1.36烧结矿的高压差温度区间从50℃增加到80℃；R=1.76烧结矿从168℃增加到218℃。因此,高碱度高MgO烧结矿在高炉内所产生透气性差的温度区间比较宽,表现为软熔带变厚,料柱透气性变差,气流不顺,高炉难以顺行,焦比增加,不易强化等。(4)论文考察了含MgO球团矿的冶金性能。MgO含量在2.0%以下时,对生球性能和成品球团的抗压强度、转鼓指数没有明显影响,但对球团矿的高温冶金性能有显著影响。当MgO含量由0.6%增加到1.8%时,RDI+3.15由62.2%增加到约75%,还原度Ri由34%增加到45-53%(900℃还原1h),同时还可降低高炉软熔带位置,扩大铁矿石的间接还原区。(5)本文在常规检测方法的基础上,对相同还原度时(Ri=40%)球团矿的膨胀性能进行了研究。当MgO含量由0.6%增加到1.8%时：高低MgO精矿搭配和添加菱镁石两种方法,都能使球团矿还原膨胀指数RSI由23%降低到约20%；但添加白云石时,由于Ca元素的影响,RSI反而由23%增加到32%。因此,虽然MgO可以改善球团矿多种冶金性能,但不宜使用白云石。(6)论文对三种炉料结构的高温软熔性能进行了试验研究。其中,低MgO烧结矿配加含MgO球团矿的炉料结构软熔性能最佳。不仅改善了烧结矿和球团矿的冶金性能,还可降低综合炉料的软熔带温度区间(TD-T10)和高压差温度区间(T2-T1)。(7)在实验室研究的基础上,进行了低MgO烧结矿配加含MgO球团矿炉料结构的现场生产试验。结果表明,减少烧结配料中MgO含量可显著改善炼铁生产技术指标。与基准期相比,试验期烧结机利用系数提高1.46%,高炉料柱压差降低4.82%,高炉产量提高0.66%。综上,本文认为适合于现代化大高炉强化冶炼要求的炉料结构为：低MgO烧结矿配加含MgO球团矿,含MgO球团矿的生产方式可采用添加菱镁石粉或高低MgO精矿粉搭配使用的方法。研究结果表明,采用“低MgO烧结矿配加含MgO球团矿”的炉料结构即可满足高炉渣对MgO含量的需求,又可改善综合炉料的冶金性能。对生产性能优良的高炉炉料,改善料柱透气性,优化高炉渣冶金性能等具有重要参考价值,为炼铁生产合理添加MgO工艺和优化高炉冶炼工艺开拓新的途径,实现集成创新。更多还原

【Abstract】 In recent years, appropriate MgO content is required in the slag of BF with the increase of overseas iron ores. At the same time, it is the requirement of smelting low-Si hot meltal and smelting some special iron ores.Aim at this problem, effects of the materials containing MgO on sintering process, pellet process and the metallurgical properties of sinter and pellet were studied in this paper. By the EPMA, X-ray diffraction and thermodynamic analysis, existent shapes of MgO in iron ore before and during its reduction process were discussed. We also studied the melting properties of the slag containing MgO. On the basis of above study, softening and melting properties of three kinds of burden structure were conducted. We chosed the best burden structure for testing production. Then the technical index had been improved significantly.The main contents and achievements of the paper include:(1) MgO content is increased properly, the properties of fluidity, desulphurizing and excepting alkali are improved. MgO content should be about 8-10%.(2) With the increase of MgO content, utilization coefficient of sinter pot, the yield, strength and grade of sinter decrease. But the low-temperature disintegration properties can be improved. If the content of MgO is decreased, we should take some measures to restrain the disintegration of sinter.(3) A temperature range about high-pressure was defined in this paper. When the MgO content increases from 1.3% to 3.0%, the temperature range of sinter (R=1.36) increases from 50℃to 80℃, that of sinter (R=1.76) increases from 168℃to 218℃. Therefore, the sinter with high basicity and high MgO content will take a wide temperature range with bad gas permeability. Then the cohesive zone becomes thicken, and the airflow becomes foul-up. It isn’t favourable to operation of BF.(4) The properties of pellet with MgO were studied in this paper. When the content of MgO is lower than 2.0%, MgO has no obvious effects on the strength and drum index of pellet, but it has obvious effects on metallurgical properties in high temperature. When the MgO content increases from 0.6% to 1.8%, RDI+3.15 increases from 62.2% to 75%, Ri increases from 45% to 53%(reduction condition:900℃, for 1 hour), and the position of cohesive zone can be declined. (5) The relative free-swelling properties was studied under the condition of Ri=40%. With the MgO content increases from 0.6% to 1.8%, the relative free-swelling index RSI decreases from 23% to 20% when magnesite or the fine ore with high MgO content is added. But RSI increases from 23% to 32% because of the effect of Ca when dolomite is added. So, though MgO can improve metallurgical properties of pellet, dolomite shouldn’t be added in pellet production based on the above analysis.(6) Softening and melting properties of three kinds of burden structure were studyed in this paper. Thereinto, the best softening and melting properties is the burden structure (sinter with low MgO content and pellet with high MgO content are mixed). This kind of burden structure not only can improve metallurgical properties of sinter and pellet, but also can decrease the temperature range of cohesive zone (TD-T10) and high-pressure zone (T2-T1).(7) On the basis of laboratory researches, the burden structure (sinter with low MgO content and pellet with high MgO content are mixed) was tested in practical production. The results of testing production shows that technical index can be improved significantly with the decrease of MgO content in sinter raw material. Compare with the base period, utilization coefficient of sinter machine increases 1.46%, pressure of burden decreases 4.82%, and the production of BF increases 0.66% in the testing period.Summarizing the above results, it is founded that the burden structure (sinter with low MgO content and pellet with high MgO content are mixed) is the best favourable to modern operation of BF. The production of pellet with MgO can take the measure of adding magnesite or adding fine ores with high MgO content. In this paper, the result of research can not only ensure proper MgO content in slag, but also improve metallurgical properties of burden. It provides important reference value for the production of excellent iron ores, for improvement of metallurgical properties of slag, for reasonable process of adding MgO in BF, for optimizing ironmaking technology, and for achieveing integrated innovation.更多还原