Simulation and application of pulsating bottom-blowing in EAF steelmaking

Pulsating bottom-blowing was proposed to strengthen the electric arc furnace (EAF) molten bath stirring. The fluid flow characteristics and stirring effects of different pulsating bottom-blowing modes on EAF molten bath were studied through water model experiments and numerical simulations. The mixing time was measured by water model experiments and the flow field characteristics of EAF molten bath were simulated by numerical simulations. Compared with conventional bottom-blowing, pulsating bottom-blowing can accelerate the fluid flow velocity and improve the stirring of molten bath. With pulsating bottom-blowing, the molten bath fluid flow field is more disorder, the fluid flow velocity increases and the dead zone volume decreases. Compared with EAF steelmaking with conventional bottom-blowing conditions, pulsating bottom-blowing technology can improve the metallurgical effects and the molten steel quality in EAF steelmaking with lower FeO content of final slag, lower phosphorus content and carbon-oxygen equilibrium of final molten steel, and lower temperature deviation.     

底吹条件下电弧炉炼钢熔池的流体流动特性

电弧炉炼钢广泛采用底吹技术以强化熔池搅拌、加速冶金反应和提升产品质量.本文通过数值模拟和水模型实验研究了底吹条件下电弧炉炼钢熔池内流体流动特性, 分析了底吹流股对流体流动的影响作用规律.随底吹流量的增加, 熔池平均流动速度增加, 熔池内“死区”体积减小.同时结合工业生产实测数据, 发现电弧炉底吹技术的运用可通过强化熔池搅拌, 加快熔池内热量传递, 均匀熔池钢液温度, 有效加快炼钢熔池的热量传递和整体升温速率, 大大提高冶炼过程热量的利用效率.     

电弧炉EBT区不同底吹搅拌条件的钢液流动数值模拟

底吹工艺在电弧炉炼钢过程中的应用能有效缩短熔池混匀时间, 加速碳、磷、硫的去除, 提高生产效率及产品质量.本文利用数值模拟软件模拟了EBT (偏心底部出钢) 区底吹孔不同气体流量下的电弧炉钢液速度场, 发现当EBT区域底吹气体流量从100 L·min^-1升至267 L·min^-1 (其他两孔气体流量稳定保持为133 L·min^-1) 时, EBT区域钢液的平均流速由2.805×10^-3m·s^-1升至3.268×10^-3m·s^-1, 钢液整体平均流速由4.126×10^-3m·s^-1升至4.610×10^-3m·s^-1, 并耦合得出EBT区域不同底吹流量下的钢液流动速度经验公式.由于钢液流动是影响熔池内反应的动力学因素, 本文提出了电弧炉炼钢基于底吹熔池搅拌的碳成分预报模型, 为冶炼终点均匀熔池成分、合理供氧操作提供理论建议.     

Study on the melting characteristics of steel scrap in molten steel

Steel scrap is of great benefit for environmental protection. In converter steelmaking, bottom carbon injection was applied to enhance the scrap ratio and in EAF steelmaking, submerged carbon powder injection was used to accelerate the smelting of scrap. In these two cases, carbon powder is directly injected into molten metal to improve the scrap melting with effective carburization capacity and intense stirring effect. In this study, the induction furnace experiments were carried out to study the melting characteristics of steel scrap with different carbon contents and bottom-blowing gas flow rates. The results show that larger carbon content and faster fluid flow can promote scrap melting because the carburizing reaction can be accelerated by larger carbon concentration gradient and the heat transfer can be enhanced by larger stirring intensity. Finally, the convective mass transfer coefficient and heat transfer coefficient between steel bar and molten metal were also calculated.     

Recent advances in the fundamentals of the kinetics of steelmaking reactions

G.R. Belton was the leader in developing our understanding of the kinetics of metallurgical reactions. Selected recent kinetic studies, based on this understanding and the application of the results to actual processes, are presented in this article. In particular, the rates of reaction of carbon and carbon in iron with CO₂ and H₂O gases and FeO in slag are reviewed and applied to the iron smelting process. In addition, our basic understanding of the kinetics of the nitrogen reaction with iron is reviewed, and the results are used in comprehensive models, which can predict the nitrogen content in steel as a function of operating variables in the basic oxygen furnace, electric arc furnace (EAF), and vacuum degassing. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

EBT区域底吹流量变化对电弧炉炼钢的影响

 电弧炉底吹是加速熔池流动、减少EBT区域死区、改善炼钢反应的重要手段,底吹流量变化会影响电弧炉熔池流动和冶金效果。利用Fluent软件研究了100 t电弧炉EBT区域附近不同底吹流量的熔池流动特性,发现当EBT区域底吹流量从100增加至150 L/min时,熔池平均流速提高18.03%,死区面积减少22.06%;当进一步增加至200 L/min时,熔池流速和死区面积变化幅度降低。在此基础上,通过100 t电弧炉炼钢试验研究了不同底吹条件下的冶金效果,发现底吹可显著降低电弧炉钢铁料消耗和石灰消耗,缩短冶炼周期,降低炉渣FeO质量分数和钢液碳氧浓度积;随着EBT区域底吹气体流量从100增加至150 L/min,冶金效果进一步得到改善。     

喷粉冶金技术在超高功率电弧炉上的应用

以炼、轧钢工序中间产物氧化铁皮为主要原料的喷粉冶金技术在超高功率电炉上的应用,实现了用工艺手段来控制炉况并强化冶炼过程的目的;达到了“高效脱碳,快速脱碳”的冶金效果。该工艺的实施还对提高钢水收得率,降低石灰消耗量和环境保护等有明显意义。     

Research on Top and Bottom Mixed Blowing CO2 in Converter Steelmaking Process

Based on the analysis of reaction mechanism between CO₂ and molten pool elements at the steelmaking temperature, and on the calculation of materials and heat balance during converter steelmaking process with blowing CO₂, a new technology which uses CO₂‐O₂ as top gas and CO₂ as bottom gas in a converter was proposed and experimented in a 30 t converter. It is found that the new technology is feasible absolutely, the amounts of smoke dust and T‐Fe are reduced by 11.15% and 12.98% on average, the contents of nitrogen and phosphorus are decreased by 50% and 23.33% respectively, iron loss of slag is lowered by 3.10% and oxygen consumption is reduced remarkably. This research will provide a new blowing method for BOF steelmaking process, which can save steelmaking energy consumption and reduce smelting cost.     

炼钢流程钢中氮的溶解及控制技术

 氮作为钢中典型的常存元素,其含量对钢产品性能有重要影响。炼钢生产过程中,由于钢液裸露容易导致增氮,或者钢液成分不同、操作不当等使含氮合金中氮的收得率不稳定等,这些因素都会使钢液中的氮含量产生明显波动,导致成品钢材性能不稳定。因此,氮的精准控制已成为控氮钢种或含氮钢种生产中的关键问题,分析了钢中氮的来源,阐释了钢液氮溶解热力学和动力学,综述了炼钢生产流程中钢液氮变化、控氮研究现状及技术措施等,提出炼钢流程中钢液氮精准控制发展方向。     

电弧炉炼钢成分预报现状与熔池搅拌对其影响

电弧炉炼钢成分预报与控制直接影响冶炼时间、产品质量与生产成本,是电弧炉炼钢智能化的重要环节。对转炉、电弧炉副枪检测技术和炉气分析技术进行了分析,探讨了炼钢过程的选择性氧化机理与智能算法在成分预报中的应用。结合熔池流动慢、反应不均衡的动力学条件,讨论了电弧炉炼钢成分预报的难点。在国内外文献综述的基础上,讨论了电弧炉底吹搅拌、氧气射流及电磁流体对钢液流动的影响,提出将电弧炉熔池钢液流动行为的动力学影响和炼钢反应选择性氧化热力学相结合,实现成分实时预测研究的设想,对开展电弧炉炼钢成分预测研究具有指导意义。     

现代炼钢流程冶炼工序的共性问题

论述了现代炼钢流程冶炼工序即转炉冶炼和电炉冶炼的共性问题;指出了二者在功能演变、原料结构、能源结构、终点控制、底吹氮、经济性评价及对生产钢种的适应性等方面存在共性;讨论了二者之间共性对中国钢生产发展的影响.并强调电炉流程与转炉流程在一相当长的时间内会共存,转炉钢与电炉钢的比例会有所变化,电炉钢的比例虽比不上世界电炉钢比的水平,但会逐步增加.     

电炉冶炼工序钢液氮含量的控制工艺研究

通过对电炉炼钢过程中不同条件、不同时期气体样进行分析,研究了电炉铁水配比、VD真空保持时间等工艺参数对钢液中氮含量变化的影响。实践表明电炉出钢氮含量随铁水配比的增加而降低,但当铁水配比大于40%后,出钢氮含量可控制在(35~67)×10-6;20 min与15 min的真空保持时间相比,脱氮率可提高15%以上。     

Numerical Simulation and Industrial Experimental Research on the Coherent Jet with “CH4 + N2” Mixed Fuel Gas

Metallurgical and Materials Transactions B - Coherent jet technology is widely used in the electric arc furnace (EAF) steelmaking process to deliver more energy and momentum into the molten steel...     

VOD底吹氮精炼高氮钢P91的工艺实践

锅炉用铁素体耐热钢P91（%:0.08～0.12C、8.0～9.5Cr、0.85～1.05Mo、0.18～0.25V、0.06～0.10Nb、0.030～0.070N）的冶炼工艺流程为20 t EBT EAF+10 t感应炉混炼-LF-VOD（吹氮）-3 t锭模铸。通过低真空（～26 000 Pa）底吹N气搅拌使脱氧剂、造渣材料充分快速与钢液反应,使[N]从（80～90）×10^-6增至（120～140）×10^-6,然后底吹氮以（9～15）×10^-6/min的增氮速率将[N]增至620×10^-6,钢材中的N含量约为500×10^-6,达到标准要求。     

电弧炉炼钢流程洁净化冶炼技术

电弧炉炼钢以废钢为基本原料,熔清后磷含量波动大,且受炉型结构限制,反应动力学条件差,深脱磷困难;全废钢冶炼熔清碳含量低,熔池内C–O反应缺乏,气泡产生数量少;且吹氧强化搅拌造成渣中FeO含量高、钢液易过氧化。电弧炉熔池内气–固喷吹冶炼新工艺,通过向熔池内部直接喷射石灰粉或碳粉,有效解决上述问题。本文通过数值模拟和水力学模拟实验研究了金属熔池内埋入式气体喷吹和气–固喷吹的冲击特征规律。熔池内射流水平和竖直冲击深度随气体喷吹流量增加而增加,而当气体喷吹流量一定时,随着喷枪安装角度的增大,熔池内射流竖直冲击深度增加,而水平冲击深度减少。同时发现,粉剂颗粒提高了气体射流的冲击动能,增加了气体射流的冲击穿透深度。     

The preparation process of nitrogenous ferrovanadium with bottom-blowing nitriding in electrical arc furnace

The flow field characteristics and stirring abilities of five kinds of bottom-blowing arrangements on the molten bath were researched in a 3t electrical arc furnace (EAF) with regular shape. The mixing time was measured by water experiment under different flow rates. Flow field characteristics of three-phase flow were simulated by numerical simulation. The average mixing time decreased with the flow rate and the radius of circle coincide increasing for the EAF with regular shape. Moreover, weakening counteracting force of counter-swirls could efficiently reduce mixing time than weakening impeding forces of sidewall with concentric circle arrangements at the tested conditions. Compared with 6R bottom-blowing arrangement at industrial application research, the 7R bottom-blowing arrangement, which was determined by the water model experiments and the simulations, could stir molten better in nitriding process, which agreed well with the experimental results of the water experiment and the numerical simulation.     

AOD炉的高效化冶炼模型

 以往的AOD炉高效化冶炼研究往往通过提高供氧强度,优化转炉的炉容比,提高终点命中率等技术缩短冶炼周期,需要充分利用现有的设备,优化炉料结构和供氧制度,对生产工艺参数进行优化,充分利用这些物理热和化学热,实现AOD炉的高效化冶炼。开发了AOD炉高效化冶炼模型,在AOD炉物料平衡和能量平衡的基础上,结合AOD炉冶炼的工艺特征,建立AOD炉耗氧量和冶炼周期模型,分析了AOD炉冶炼周期随着铁水比和废钢比的变化趋势,得出冶炼周期最短时的炉料结构。结果表明：电炉不锈钢母液加铁水冶炼时,冶炼周期随着铁水比的增加而增加。电炉不锈钢母液加废钢冶炼时,冶炼周期随着废钢比的增加而增加。铁水加废钢冶炼时,冶炼周期随着废钢比的增加而延长。以硅铁为发热剂比以碳粉为发热剂冶炼周期短。     

Characterisation of coal–charcoal composite biocoke as a sustainable alternative for ironmaking

The partial substitution of coal by wood charcoal or other types of biomass for the production of metallurgical coke is catching the attention of the steelmaking industry worldwide because it generates less CO₂ in the industrial processes. The objective of this paper is to correlate the effect of the proportion of coal and wood charcoal on the mechanical strength and CO₂ reactivity in briquettes of mixtures of coal and wood charcoal. The briquettes were manufactured from mixtures of coal and 5, 10, 15, 20, 30, 40 or 50 wt-% of wood charcoal. Both materials were grounded and sieved until the particle size was less than 0.044?mm. The mixture was then pressed in a cylindrical die and heat-treated under a nitrogen flow from ambient temperature until 1373?K for 8 hours. Compressive strength and CO₂ reactivity tests were conducted on the samples. Optimal results of the compressive strength were obtained for additions of wood charcoal between 10 and 15 wt-%. For mixtures with wood charcoal contents above 5 wt-%, the CO₂ reactivity tests showed an increase in the reactivity compared to the briquettes of coal without the addition of wood charcoal.     

碳化硅的冶金性能及其在钢铁工业中的应用

在分析SiC的脱氧性质、溶解特性等冶金性能的基础上,结合部分钢铁企业应用SiC脱氧剂的实例,分析了SiC脱氧剂在钢铁冶炼过程中脱氧合金化、精炼脱氧及钢水提温的冶金性能及机理。SiC在脱氧合金化过程中,脱氧反应迅速,能使钢液增Si、增C,净化钢液,提高钢水流动性,并且能提高合金收得率,降低炼钢成本。     

Interactions of Polymer/Coke Blends with Molten Steel at 1823 K: Interfacial Phenomena

With an aim to recycle waste polymers as a carbon resource in steelmaking, in‐depth investigations have been carried out on polymer/coke blends and molten steel at 1823 K. Three polymers, namely high density polyethylene (HDPE), polyethylene terephthalate (PET), and bakelite were blended with metallurgical coke and devolatilized at 1473 K using a drop tube furnace. High temperature interactions of various chars with molten steel were investigated at 1823 K using the sessile drop technique in argon atmosphere; the influence of polymers on the interfacial phenomena and carbon dissolution was determined. While the residual volatiles from HDPE did not affect the chemical composition of interfacial products, the coverage of the interfacial region was somewhat slower than metallurgical coke. Oxygen present in PET was found to oxidize liquid steel leading to the formation of FeO at the interface modifying both the chemical composition and the morphology of the interfacial region. CaCO₃, present as a filler impurity in bakelite was found to act as a fluxing agent and lowered the melting point of the ash layer at the metal/carbon interface. The addition of polymers improved the overall carbon dissolution into molten steel by a small extent as compared to metallurgical coke. This study has shown that a variety of waste polymers can be utilized to partially replace metallurgical coke in steelmaking.