Effect of MgO content in slag on dephosphorisation in converter steelmaking

Abstract

In this study, the effect of MgO content in slag on the phosphorus distribution ratios, and the equilibrium solubility of MgO in slag during converter steelmaking were analysed using the modified Kozheurov regular solution model and the thermodynamic package FactSage. Thermodynamic analysis shows that the MgO content in the final slag should be greater than 5% to saturate the slag with MgO and minimise the chemical wear of the refractory lining. However, the phosphorus distribution ratio decreases dramatically with increasing MgO. Industrial tests were performed using an 80-t top-and-bottom combined blown converter showed that the average phosphorus distribution ratio reduces significantly from 120.7 to 75.7 when the average MgO content in the final slag increases from 7.0 to 9.8%, due to thermodynamics and kinetics reasons. By optimizing the MgO content between 6 and 8% dephosphorisation and refractory wear are optimised.     

炼钢尾渣在260t转炉的应用实践

介绍了鞍钢炼钢尾渣在260 t转炉的利用现状,研究了尾渣的特性和尾渣对转炉脱磷效果、终点氧化性、炉衬侵蚀及溅渣护炉的影响,拓展了尾渣的使用途径。实践结果表明,炼钢尾渣在转炉应用,提高了转炉化渣效果,降低了熔剂消耗,提高了脱磷效率。     

济钢超低碳、超低磷钢转炉溅渣护炉工艺

随着超低碳、超低磷钢种冶炼的增多,济钢复吹转炉终点氧含量大幅提高,严重侵蚀了转炉炉衬。从高氧化性炉渣对炉衬的侵蚀机理入手,提出了兼顾溅渣层和炉底的溅渣工艺,介绍了超低碳、超低磷钢溅渣护炉工艺参数的优化及取得的效果。     

转炉用溅渣镁球造渣技术

针对转炉炉渣MgO含量偏低的现象,对转炉使用溅渣镁球代替轻烧白云石造渣技术,合理控制溅渣镁球的加入量,达到降低终渣FeO、提高渣中MgO来迅速降低炉渣过热度等目的,从而可以缩短溅渣时间,提高溅渣层的抗侵蚀能力,最大限度发挥溅渣护炉效果,延长补炉间隔时间,节约耐火材料,提高生产作业率,并降低炼钢的冶炼成本。     

转炉溅渣护炉工艺技术研究

溅渣护炉工艺是近期发展起来的一项新技术，该工艺设备简单，投资少，收效快，操作方便，可大幅度提高衬寿命，进而提高炉龄次数，介绍了溅渣护炉工艺原理，有关参数及经济效益。     

100t 转炉炉衬侵蚀因素的分析和长寿炉龄的工艺实践

通过分析了水钢100 t顶底复吹转炉炉衬的损坏机理和影响炉渣熔化性能的因素,得出每1%V₂O₅降低炉渣熔化温度27℃,每增加1%TiO₂含量,炉渣半球温度约降低5℃,当炉渣TFe含量在20%以上时,炉渣熔化温度在1 320~1 395℃。通过采取铁水捞渣工艺;建立转炉热平衡操作模式,提高拉碳率;铁水Si在0.6%~0.8%时,采用单渣操作,铁水Si>0.8%时,采用双渣操作;建立转炉最佳炉型及控制措施;优化钢水温度制度和优化脱氧合金化制度,降低出钢温度;在补吹提枪前加入适量焦丁,确保冶炼终点炉渣中FeO保持较低含量,提高溅渣护炉效果等工艺措施,结果使转炉炼钢的耐火材料消耗降到8.75 kg/t钢,转炉炉龄达到29 336炉。     

传热模型对炉衬设计与粘渣护炉关系的分析

通过建立耐火材料炉衬的传热模型，分析了炉衬内不同材料间厚度，导热系数、温度与粘渣层性能、厚度间的关系，认为在选择炉衬结构时，必须考虑炉衬的渣耗附性能，适当增加法的厚度，同时注意调整砖的导热系数与结构，以利于延长炉衬使用寿命，降低维持炉衬长寿运行的成本，模型设立有利于转炉粘渣护炉及高炉钒钛护炉技术下炉衬结构设计的合理改进。     

50 t转炉底吹作业和溅渣护炉特点

阐述了萍钢50 t顶底复吹转炉炼钢生产的工艺流程,复吹转炉底吹调试、使用、维护和溅渣护炉的工艺特征,及目前取得的效果.     

氮气转炉溅渣护炉技术

氮气转炉溅渣护炉技术是一项显著提高转炉护龄,降低生产成本的先进技术。介绍了溅渣工艺及溅渣技术的关键因素,并着重论述了保证溅渣技术实施的供氮条件。     

转炉预脱磷与“全三脱”铁水少渣冶炼技术

 京唐公司炼钢系统铁水转炉预脱磷及“全三脱”铁水少渣冶炼工艺不断进行技术优化,脱磷转炉通过优化废钢尺寸、底吹枪数量和排布,半钢脱磷率可达到70%;铁水经过脱磷转炉脱硅、脱磷后,温度和磷质量分数更加稳定,为脱碳转炉少渣冶炼、自动化炼钢终点双命中率的提高提供了先决条件;脱碳转炉通过采用留渣操作、少渣冶炼技术、溅渣护炉技术后,自动化命中率达到90%以上,炉龄达到7 000炉以上;炼钢车间内渣钢、除尘灰、氧化铁皮等含铁物料实现了自循环消耗。采用“全三脱”铁水冶炼工艺,钢种质量进一步提高,超低磷与超低硫钢中（S＋P＋N）元素质量分数可稳定控制在0.009 5%以下。     

Adhesive Behaviour of BOF Slag to BOF Lining Refractory in Slag Splashing Process

A slag layer is formed when slag is splashed onto refractory lining in BOF slag splashing process. The melting temperature of the slag layer and the adhesion of the slag layer to the lining refractory have an important effect on slag splashing and BOF lining life. This study investigates the adhesive behaviour of slag with different composition to lining refractories. It is shown that the slag can adhere to MgO particles in MgO‐C bricks well and no reaction is found between the MgO particles and the slag layer, but a gas gap exists at the interface between the slag layer and the MgO‐C matrix and there are iron granules within the slag layer, when the FeO content in the slag is high. The adhesion of the slag layer to the lining refractory can be improved with decreasing FeO content in the slag and lower carbon content in the MgO‐C bricks. BOF refractory lining life can be greatly increased due to better adhesion, high melting temperature, and stronger wear‐resistance of the slag layer.     

漩流氧枪转炉炼钢熔体的喷溅行为

 转炉冶炼过程金属熔体的喷溅对于转炉反应器的性能有重要影响。氧枪作为氧气射流的产生及控制单元,决定了转炉吹炼过程熔体的喷溅行为。通过水模型试验,研究了漩流氧枪转炉冶炼过程熔体的喷溅,考察了氧枪喷孔扭转角设计及操作参数下熔体喷溅速率和喷溅的空间分布规律,基于此,分析了漩流氧枪对转炉反应器性能的影响。结果表明,相比于传统氧枪吹炼,漩流氧枪吹炼时熔体喷溅速率降低,喷溅高度下降,喷溅在径向空间分布趋于均匀,且随着喷孔扭转角的增大,该分布规律变化更为显著,扭转角大于20°时,喷溅到炉口及炉外的熔体降为零。漩流氧枪吹炼时,喷溅速率及喷溅量在不同径向和高度位置处分布随着顶吹气量的增大而增大,受枪位的影响规律与扭转角有关。     

小型转炉溅渣护炉工艺与效果

介绍了25t转炉溅渣护炉工艺,总结了溅渣护炉试验结果,采用该工艺能够大幅度提高炉龄,降低耐材消耗,综合效益可观。     

宣钢150t转炉长寿技术创新

分析了溅渣转炉炉衬的主要破坏机理,阐述了宣钢150 t转炉炉衬维护在应对各种形式的侵蚀时采用的创新性技术。系统地介绍了溅渣护炉技术的合理应用,炉帽部位的长寿技术,受料面长寿技术,出钢口部位的维护技术,炉底底吹元件长寿技术,综合炉衬指标的优化等关键的技术情况。为大型转炉长寿技术的发展提供了借鉴。     

转炉溅渣护炉改质剂的开发研究

影响转炉溅渣护炉效果的关键因素是终渣成分的控制,采用改质剂对转炉终渣成分进行调整,降低渣中FeO含量和炉渣温度,提高MgO含量和炉渣熔点及粘度,有利于改善炉渣与炉衬的粘结效果,并提高溅渣层的耐蚀性能,缩短溅渣起孕时间,在一定程度上抑制炉渣中铁的氧化物与炉衬中石墨的反应.     

120t转炉炉衬维护实践

西钢120t转炉采用科学设计北方烘炉方案,采取分区段控制溅渣操作要点,严格落实操作工艺要求和步骤,实现北方钢厂大型转炉第一代炉役接近20000次的突破,取得良好的效果。     

转炉炉龄提高后炉型控制的实践

简介了济钢第一炼钢厂在炉龄提高后的炉型控制状况;重点针对溅渣后炉型的变化,优化了溅渣护炉和砌炉工艺,改进了炉渣性质,进而提高了溅渣护炉效果和保持了合理炉型,保证了生产的稳定运行。该厂控制炉型的实践对炼钢生产有一定的指导意义。     

包钢80 t复吹转炉溅渣护炉工艺实践

包头钢铁（集团）有限公司在80t复吹转炉上开发出溅渣护炉工艺,复吹转炉炉龄超过了1万炉,耐火材料消耗量降低至3．28kg/t,经济效益显著。     

Combined blowing with three ‐ hole lance in a sidewall blowing converter

Traditionally, in stainless steelmaking converters, oxygen has been blown by a one‐hole lance (1 HL) and sidewall tuyères. In order to reduce the tap‐to‐tap time, the multi‐hole lance has been used for oxygen blowing. The aim of this work was to develop blowing practise for a multi‐hole lance to reduce the tap‐to‐tap time and minimise metal splashing and spitting in the sidewall blowing converter (chromium converter). In the chromium converter the chemical energy of liquid ferrochrome (which contains 4 % silicon and 7 % carbon) is utilised for scrap melting by oxidising the silicon and the part of carbon. The research has been made by a dynamically scaled water model and full‐scale converter. Used parameters were the gas flowrate from sidewall tuyères and lance, lance height, charge weight and position of multi‐hole lance. Splashing has been measured during blowing from walls (splashing) and mouth of the converter model (spitting). The model tests indicated less splashing and spitting by the three‐hole lance (3 HL) than traditional 1 HL. The 1 HL caused strong skulling of the converter cone. By 3 HL blowing the position of the lance has a remarkable effect on the direction and the amount of splashing and lance life. Because of hot metal‐slag splashes, the life time of the 3 HL was halved by position 1 (compared to 1 HL). With the lance position 2 the splashing decreased by approx. 50% in model tests and lance life time increased by ~ 50% (compared to 1 HL) in the full‐scale converter. The model agreed well with the full‐scale converter. According to the process tests, the nominal productivity of the chromium converter has increased 15 % and depending on the refining practise and the silicon content of ferrochromium the lining life has increased 20 ‐ 30 %. In the future the multi‐hole lance will be tested in the AOD vessel.     

半钢炼钢条件下的溅渣护炉技术

介绍了攀钢120t转炉溅渣护炉研究中所进行的钒钛钢渣性质、钒钛钢渣成分选择、造渣工艺优化、降低终渣TFe含量、吹氮溅渣参数控制等方面的研究工作以及所取得的效果。