【作者】 孙健；

【导师】 储满生；

【作者基本信息】 东北大学 ， 钢铁冶金， 2021， 博士

【摘要】 高炉的寿命对钢铁企业的经济效益影响巨大,而在众多制约高炉长寿的问题中,高炉炉缸异常侵蚀和烧穿是影响高炉长寿的最主要的问题。由此炼铁工作者在高炉设计、生产和维护上均提出了相关措施以控制高炉炉缸的异常侵蚀,进而提高高炉寿命。在众多提高高炉寿命的技术措施中,仅有高炉加钛护炉技术可以实现对冶炼中高炉进行维护。然而,由于含钛炉料性能差异大,高炉适应困难,含钛炉料护炉机理存在争议,无法实现钛资源的高效利用,甚至影响高炉加钛护炉的效果。因此,本论文开展了“钛矿护炉机理及钛资源优选技术”研究,旨在提升含钛炉料的利用效率和经济性、促进钛资源的高效利用,保证高炉加钛护炉效果。研究内容主要包括:护炉含钛炉料冶金特性研究,钛在渣金界面分配规律研究,加钛护炉过程中炉缸碳氮化钛保护层形成机理和基于钛资源高效利用的炉料成本优化模型研究。本研究主要得出以下结论:(1)护炉含钛炉料冶金特性研究。钛球-B具有良好的还原性、高温熔化特性和综合炉料的熔滴性能。钛球类含钛炉料中的含铁物相为赤铁矿和假板钛矿,在还原过程中物相的转变历程为:Fe2O3→Fe3O4→FeO→Fe,Fe2TiO5→FeTiO3(反应温度低于 977℃),Fe2TiO5→FexO 和 TiO2(反应温度高于977℃);钛矿类含钛炉料中的含铁物相主要为磁铁矿和钛铁矿,在还原过程中物相的转变历程为:Fe3O4→FeO→Fe,其中钛铁矿并不参与还原反应。含钛炉料中含铁物相的差别造成了还原性的差异。几种含钛炉料中钛球-B的还原性最佳,其还原性指数可达80.58%。还原后钛球-B中尖晶石和钛铁尖晶石的组分较少,熔化过程中生成的液相较少,其表现出良好的高温熔化特性,钛球-B的高温熔化特性指数和高温熔化速率指数分别为525 g·℃和1.55 g·s-1,其高温熔化性能在几种钛资源中最好。从综合炉料熔滴实验结果来看,使用钛球-B方案的S值是几种方案中最低的,为13 kPa·℃。综合来看,高炉使用钛球-B对保证高炉稳定顺行最为有利,同时实验结果与工业试验结果相符。(2)钛在渣金界面分配规律研究。渣金间二氧化钛和C的反应为吸热反应,温度升高有利于还原反应向正向进行,以及提高钛元素在炉渣和铁液中的扩散速度,铁水中钛的质量分数和渣铁间钛分配比随着反应温度的升高而显著升高;提高炉渣中TiO2的质量分数,可使炉渣中γTiO2显著升高,进而促进铁水中钛的质量分数和渣铁间钛分配比的提高;而改变炉渣碱度和炉渣中MgO的质量分数对炉渣中γTiO2影响较小,因此其对铁中钛的质量分数和渣铁间钛的分配比影响也很小。利用SPSS统计分析软件开展了相关性分析和回归分析,获得了高炉钛负荷回归方程和钛收得率的回归方程。(3)加钛护炉过程中炉缸Ti(C,N)保护层形成机理。生产实践表明铁水中钛的质量分数控制在0.08%～0.2%之间,可在高炉炉缸侵蚀位置形成Ti(C,N)保护层。通过提高冷却强度,提高铁液中钛的质量分数,控制铁水流速可促进Ti(C,N)颗粒的析出和碳氮化钛保护层的形成。Ti(C,N)的析出主要受温度和铁中钛的质量分数影响,与炉渣中钛的质量分数关系不大,提高含钛炉料的护炉效果,应从改善渣铁间钛的还原条件,提高钛在渣铁间的分配比入手。Ti(C,N)析出临界钛的质量分数测定实验结果显示,在铁水中钛的质量分数按照0.1%控制时,炉墙附近铁水温度要低于1350℃时,才能保证Ti(C,N)的稳定存在。(4)基于钛资源高效利用的炉料成本优化模型研究。以成本最低和护炉需求为目标,建立了基于钛资源高效利用的炉料成本模型,实现了不同护炉目标参数条件下的最低吨铁炉料成本的计算。利用该模型分析发现,提高目标铁中钛的质量分数和铁中硫的质量分数会使炉料的最低成本有所升高;提高铁中硅的质量分数,可降低炉料的最低成本;模型在固定护炉需求和工艺条件下,可实现含钛炉料的优选,铁中硅的质量分数为0.3%,硫的质量分数为0.08%,目标钛的质量分数为0.1%～0.12%条件下,使用钛球1可实现高炉的炉料成本最低(1143元/吨);模型可根据原料的供应,实现基于低成本护炉的炉料结构优化,如依据首钢某大型高炉的原料条件,炉料结构可优化为69%烧结矿+23%球团矿+4%钛球1+4%块矿,可实现炉料成本降低14.43元/吨。本研究开展的钛资源优选技术研究,为高炉护炉用含钛炉料的选择提供理论依据,为提高护炉用含钛炉料的使用效率提供了手段和方法,为高炉服役末期的低成本冶炼和高效率护炉奠定了坚实基础。更多还原

【Abstract】 The service life of the blast furnace has a great influence on the economic benefits of iron and steel enterprises.Among many problems restricting the long service life of blast furnace,the abnormal erosion and burning out of blast furnace hearth are the main problems.In order to control the abnormal erosion of blast furnace hearth and prolong the service life of blast furnace,some measures have been put forward by ironmakers in design,production,and blast furnace maintenance.Among many measures to improve the service life of blast furnace,only titanium addition charging can realize the maintenance of blast furnace hearth lining during blast furnace production.However,it is difficult to adapt to the blast furnace because of the large difference in the performance of titanium additions,and the mechanism of titanium addition is controversial,so the efficient utilization of titanium resources can not be realized,and even the effect of titanium addition on blast furnace hearth lining maintenance is affected.Therefore,research on mechanism of blast furnace hearth lining maintenance with titanium addition and optimization technology of titanium resources has been carried out,aiming to improve the utilization efficiency and economy of titanium addition,promote the efficient utilization of titanium resources,and ensure the effect of blast furnace hearth lining maintenance by titanium addition.The research mainly includes:metallurgical characteristics of titanium addition,titanium distribution law at slag-iron interface,formation mechanism of the protective layer of titanium carbonitride in the hearth of the BF during titanium addition,and research on burden cost optimization model based on the efficient utilization of titanium resources.This study mainly draws the following conclusions including:(1)Metallurgical characteristics of titanium addition.Titanium pellet-B has good reducibility,high temperature melting characteristics and softening-melting performance of mixed burden.In the pellet-type titanium addition,the iron-containing phases are hematite and pseudobrookite,and the phase transformations during reduction are:Fe2O34Fe3O4→FeO→Fe,Fe2TiO5→FeTiO3(the reaction temperature is lower than 977℃),Fe2TiO5→FexO and TiO2(the reaction temperature is higher than 977℃).The iron-containing phases in the lump type titanium addition are magnetite and ilmenite,and the phase transformation during reduction is:Fe3O4→FeO→Fe,and the ilmenite does not participate in the reduction reaction.The difference between iron-containing phases in the titanium addition causes the difference in reducibility.The reduction index of titanium pellet-B can reach 80.58%,which shows the best reduction performance among several titanium additions.There are less spinel and titanium-iron spinel in the reduced titanium pellet-B,and less liquid phase is formed in the melting process,which shows good high temperature melting characteristics.The indexes of the high-temperature melting characteristic melting rate index of pellet-B are 525 g·℃ and 1.55 g/s respectively,where its high-temperature melting characteristic is the best among several titanium additions.The softening—melting performance in experiments of mixed burden shows that the S-value of the scheme with titanium pellet-B is 13 kPa·℃,which is the lowest among several schemes.Accordingly,maintaining the blast furnace hearth lining with pellet-B is the most beneficial to ensure the stability of the blast furnace.Meanwhile,it agrees with the results of the industrial trial.(2)Titanium distribution law at slag-iron interface.The increase in temperature is conducive to the forward reaction,and increases the diffusion rate of titanium in slag and hot metal,as the reduction reactions of titanium dioxides are endothermic.The titanium content in hot metal and titanium distribution ratio between the slag and hot metal increase significantly with the reaction temperature.Increasing the content of titania in slag can significantly increase the γTiO2 of the slag,thereby promote the increase of the titanium content in the hot metal and titanium distribution ratio between the slag and hot metal.Changing the basicity and MgO content in the slag has little effect on the γTiO2 of slag,so it has an insignificant effect on the titanium content in hot metal and the distribution ratio of titanium between slag and hot metal.SPSS software was employed to conduct correlation and regression analysis,which established titanium load regression equation and titanium yield regression equation.(3)The formation mechanism of protective layer of Ti(C,N)in the hearth of the blast furnace during titanium addition charging.Production practice shows that the titanium content in the hot metal is controlled between 0.08%～0.2%,a protective layer of titanium carbonitride can be formed at the corroding position of the blast furnace hearth.By increasing the cooling strength and titanium content in hot metal and slowing its flow,the formation of protective layer of titanium carbonitride can be promoted.The precipitation of titanium carbonitride is mainly affected by temperature and titanium content in hot metal,yet it is not noticeably correlated with the titania content in slag.To improve the utilization of titanium addition,it should start with improving the reduction conditions of titanium at slag-iron interface,and increasing the titanium distribution ratio between the slag and hot metal.The determination of the critical titanium content of titanium carbonitride precipitation shows that when the mass fraction of titanium in the hot metal is controlled at 0.1%,the temperature of hot metal near the furnace wall must be lower than 1350℃ to ensure the presence of titanium carbonitride stably.(4)Optimization of burden cost based on the efficient utilization of titanium addition.By aiming at the lowest cost and furnace hearth lining maintenance requirements,the blast furnace burden cost model was established,and the goal of protecting the furnace lining can be achieved with the lowest cost of burden per ton hot metal.The model was used to analyse the influencing factors of the burden cost when adding the titanium addition to protect the furnace lining.The results show that increasing the target titanium content and the sulfur content in hot metal will increase the minimum burden cost,while increasing the silicon content in the hot metal can reduce the minimum burden cost.The model can acheive the optimization of titanium addition under fixed furnace hearth lining maintenance requirements and process conditions.While the silicon content in hot metal is 0.3%,the sulfur content in hot metal is 0.08%,and the target titanium content in hot metal is 0.1%～0.12%,the lowest burden cost can be acheived by using titanium pellet 1(1143yuan/ton).The model can acheive the optimization of the charging scheme based on low-cost furnace hearth lining maintenance according to the supply of raw materials.According to the raw material supply of a large blast furnace of Shougang,the charging scheme can be optimized to 69%sinter+23%pellet+ 4%titanium pellet 1+4%lump,which can reduce the burden cost by 14.43 yuan/t.The research on optimization of titanium addition provides a theoretical basis for the selection of titanium addition for BF hearth lining maintenance,it also provides means for improving the utilization efficiency of titanium addition,and lays a solid foundation for low-cost smelting and high-efficiency furnace hearth lining maintenance at the end of blast furnace service.更多还原