【作者】 李翔；

【导师】 包燕平；

【作者基本信息】 北京科技大学 ， 冶金工程， 2016， 博士

【摘要】 当前,中国钢铁工业面临产能过剩,行业利润微薄,环境污染严重等问题。转炉留渣双渣工艺使用上炉终渣替代本炉部分石灰,相对传统单、双渣工艺能大幅降低转炉石灰消耗,这对于降低转炉生产成本,并减少钢渣排放带来的环境污染等问题具有重要意义。该工艺冶炼过程分为脱磷及脱碳两阶段,脱磷阶段需要完成脱除大部分磷并将脱磷渣从炉内倒出的双重任务,其中炉渣泡沫化是将脱磷渣从炉内倒出的主要手段,脱磷阶段倒渣和脱磷是整个留渣双渣工艺的关键环节。因此,本文重点研究了脱磷阶段炉渣泡沫化及脱磷相关理论,为认识和完善留渣双渣工艺倒渣及脱磷技术提供指导。通过统计50t转炉留渣双渣工艺大量生产数据,进一步明确了脱磷阶段结束倒渣量、倒渣铁损,脱磷阶段脱磷是留渣双渣工艺开发过程中的关键难点,为相关理论研究提供了依据。在50t转炉脱磷阶段结束倒渣现场取样,并统计泡沫渣电镜照片,研究表明：泡沫渣由气泡、渣相、铁珠组成。泡沫渣至上而下气泡数量逐渐增加,气泡尺寸及孔隙率逐渐减小,气泡球形度多集中在0.9～1.0。通过分析泡沫渣形成过程,提出了获得更大倒渣量的有利条件：减少泡沫渣的析液时间即快速倒渣,同时增加碳氧反应速率。针对倒渣铁损过大,泡沫渣中含有大量铁珠等问题,使用水/硅油界面模拟了气泡穿越钢/渣界面气泡夹带行为,研究表明：增加炉渣粘度及减小气泡尺寸,有利于降低气泡夹带率。回归相关参数后,得到了气泡夹带率(M)计算公式,M=4.6Eob2.57(ηs/ηd)-0.75(ps/pd)-5进一步探讨气泡夹带机理表明：大尺寸液滴主要由高速运动的球冠形气泡夹带,而小尺寸液滴则主要是由运动速度较慢的锥球形气泡夹带。Factsage热力学理论计算及热态试验结果表明：脱磷渣中物相主要由富磷相、富铁相及基体相组成,碱度在1.5～2.5时,处在硅酸二钙初生区内,随着炉渣碱度的降低,2Ca0.SiO2析出量略微减少,从而使富磷相中磷含量增加,有利于转炉脱磷：当碱度<1.5时,处于CaSiO3初生区内,2CaO·SiO2相析出量显著减少,不利于转炉脱磷,结合提高碱度有利于渣钢脱磷反应的传统脱磷理论,适宜的脱磷渣碱度范围为1.5～2.5。50t转炉生产优化试验表明,对于倒渣环节,通过倒渣前0.5～1min批量加入矿石2～6kg/t来提高碳氧反应速率,并将倒渣时间控制在3min以内,使倒渣量增加了32.6%。对于脱磷环节,脱磷阶段：吹氧时间、温度、炉渣碱度、Fe2O3含量控制区间分别为4-6min、1350～1400℃、1.6～2.2、20-25%。脱碳阶段,温度在1610～1700℃、炉渣碱度在3.2～5.2、Fe2O3含量在17～30%之间时,降低温度、提高碱度及Fe2O3含量有利于脱磷,根据钢种脱磷需求合理控制脱碳阶段炉渣成分及温度。工艺优化后,转炉终点平均脱磷率达到了92.7%,吨钢石灰消耗下降了30.3%,钢铁料消耗降低了0.55%。更多还原

【Abstract】 Currently, Chinese iron and steel industrises are facing the problems including overcapacity, thin margins and serious environmental pollution. Compared with traditional single slag or double slag process, it will reduce the consumption of lime during the converter slag-remaining and double slag process by substitute final slag in the last heat for some lime in the current heat. It has a great significance to reduce the production cost and improve the environmental pollution by decreasing the discharge of steel slag.There are two phases during this process, i.e. decarburization phase and dephosphorization phase. Two tasks should be completed during dephosphorization process which are the removal of most phosphorus and the extracting of dephosphorization flux from converter. Slag foaming is the important way of removing dephosphorization flux from converter. Deslagging and dephosphorization are the key parts of the whole slag-remaining and double slag process. Therefore, slag foaming during dephosphorization phase and dephosphorized theory were mainly studied in this paper which provide guidance to understand and improve the slag-remaining and double slag process.The statistic analysis of many production data during 50t converter slag-remaining and double slag process indicates that the quantity of deslagging, iron loss caused by deslagging, and dephosphorization during dephosphorization phase are key difficulties. It also provides a basis for related theoretical research.Samples were taken during deslagging process at the end of the 50t converter dephosphorization phase and the electronic microscope photographs of foaming slag were analyzed. The results indicate that the foaming slag are composed of foam, slag phase and iron shot. The number of bubbles in foaming slag increases, the bubble size and porosity decreases from up to down. The roundness of bubble are about 0.9～1.0 mostly. The favorable conditions of obtaining large quantity of deslagging was obtained by analyzing the formation process of foaming slag: reducing the drainage time, i.e. deslagging rapidly, increasing the reaction rate of carbon and oxygen.As to the large loss of iron and the foaming slag containing large amount of iron shot, the water/silicon oil system was used to simulate the bubble entrainment behavior during it going through steel/slag interface process. The results show that increasing the viscosity of slag and reducing the bubble size benefit the decrease of bubble entrainment rate. After the regression of relative parameters, the formula of bubble entrainment was obtained M=4.6EoB2.57(ηs/ηd) (ps/pd)-5 The mechanism of bubble entrainment was deeply studied and it indicates that large size droplets are entrained by high speed spherical crown-shaped bubbles and the small droplets are entrained by low speed cone-shaped bubbles.The thermodynamic theoretical calculation of Factsage and hot state experimental results show that the phase constitution of dephosphorization flux were phosphorus-rich phase, Fe-riched phase and substrate. When the basicity of slag was 1.5-2.5 and the composition of slag located in primary zone of dicalcium silicate, the precipitation of 2CaO·SiO2 reduced slightly which increased the phosphorus content in phosphorus-rich phase and it benefites dephosphorization in convertor. When the basicity of slag was lower than 1.5 and the composition of slag located in primary zone of CaSiO3, the precipitation of 2CaO·SiO2 reduced obviously which was unfavorable for dephosphorization. Considering the traditional dephosphorization theory that high basicity slag benefits dephosphorization reaction between steel and slag, the suitable basicity of slag should be 1.5～2.5.The optimal production results of 50t converter indicates that during the deslagging process, the carbon and oxygen reaction rate increased through adding ore 2～6kg/t in batch 0.5-1min before deslagging and the quantity of deslagging increased by 32.6% by controlling the deslagging time less than 3min. As to dephosphorization part, during dephosphorization phase, the blowing oxygen time, temperature, slag basicity and Fe2O3 content were respectively 4-6min、 1350～1400℃,1.6～2.2,20～25%. During decarburization phase, when the temperature was 1610-1700℃, the slag basicity was 17～30%, the decrease of temperature and increase of basicity and Fe2O3 content benefit dephosphorization. The composition of final slag and temperature should be adjusted according to the requirement of steel grade. The average dephosphorization rate reached 92.7%, the consumption of lime reduced by 30.3% and the iron and steel material consumption reduced by 0.55%.更多还原