Cold Modelling of Slag Splashing in LD Furnace by Oxygen Lance with Twisted Nozzle Tip

The effects of a conventional lance tip with 4 normal nozzles and a lance tip with 4 twisted nozzles on slag splashing were investigated. A cold model for LD converters, Jiuquan Iron & Steel Co., was established and the amount of slag splashed onto the model walls was measured in the cold modelling experiments. The results from the experiments show that at low top gas flow rate the amount of slag splashing for the tip with twisted nozzles is less than that for the conventional tip, whereas at high top gas flow rate the amount of slag splashing for the nozzle twisted lance is greater than that for the conventional lance. For the nozzle twisted lance tip, slag splashing rates increase with increase in slag amount, lance height and top gas flow rate and the maximum amount of slag splashing for the tip with twisted nozzles can be obtained under the process parameters of 47.6 Nm³/h gas flow rate, 12% slag amount and 247 mm lance height. More slag droplets can be directed onto the cone with a nozzle twisted lance tip than with a normal lance tip at high top gas flow rate.     

Physical simulation of converter steelmaking with powder injection

A water model of top and bottom blown converter with top lance powder injection and bottom tuyere powder injection was established to investigate the powder injection. The results show that the powder penetration ratio under the condition of top lance injection is greater than that under the condition of bottom tuyere powder injection. In both cases, the powder penetration ratio increases with the increase of solid/gas ratio and powder particle size. Powder uniform dispersion time with top lance powder injection is longer than that with bottom tuyere powder injection. Top lance powder injection, lance height of 258?mm, bottom blowing rate of 1·96?Nm³?h^?1 and powder particle size of 0·212–0·380?mm are suggested as the optimum powder injection operation under the experimental condition. The corresponding optimum operation for prototype is top lance powder injection with lance height of 1550?mm, powder size of 1–5?mm and bottom blowing rate of 450?Nm³?h^?1.     

顶吹转炉溅渣护炉工艺冷态模型实验研究

采用水力模型的研究方法,对顶吹转炉溅渣护炉工艺进行冷态模型试验。通过测定溅到转炉炉衬上的渣量,分别对顶枪枪位、气体流量、渣量等工艺参数的影响进行比较,从而确定最佳操作工艺参数。     

Converter life enhancement through optimisation of operating practices

Abstract

Converter lining life is an important technical and economic concern of the steelmaking process. An increase in lining life decreases refractory consumption and reduces steelmaking costs. Increased availability of furnaces increases production rates and steel yield. Extended lining life was achieved by utilising the slag as a consumable refractory by splashing it over the lining. Slag splashing is a simple and effective technique followed worldwide to increase the converter life. This paper highlights the online study on various operating parameters and slag characteristics for consistent slag splashing in a 130 t converter. Parameters such as lance height, blow pattern, gas flowrate, bottom purging flowrates, tapping temperature, combination of gunniting with splashing, slag height and slag chemistry, were investigated. An optimised slag has been developed which served effectively to balance the lining erosion during blowing and maintain a uniform thickness throughout the campaign. Some innovative practices and design changes are also discussed. The developed slag regime and optimised parameters have helped in increasing the converter life to an international benchmark. JSW Steel has achieved the converter lining life of 13 771 heats, which is the highest ever recorded in India.     

新余钢铁公司25 t转炉溅渣护炉工艺的研究

采用缩小的冷态模型，对新余钢铁集团有限公司25t顶吹转炉的溅渣护炉工艺进行了研究。结果表明，顶吹气体流量的提高有利于增加炉衬的溅渣密度；当气体流量为7000m^3/h时，最佳枪位为1．4m；从整个炉衬的溅渣密度来看，最佳渣量为8％－10％，综合考虑炉衬和炉帽的溅渣量，最佳渣量为10％。将以上溅渣工艺参数应用到实际生产中，并采用改渣剂对高氧化铁终渣成分进行调整，新余钢铁集团有限公司转炉平均炉龄由2238炉增加到8721炉，最高炉龄达到11675炉。     

Bath mixing behaviour in top–bottom–side blown converter

Abstract

The influence of blowing process parameters on bath stirring was investigated in a model of a top–bottom–side blown converter using physical modelling experiments. It was shown that the side blowing gas flowrate has an important influence on bath mixing time which decreases as side tuyere gas flowrate increases up to a critical flowrate and then plateaus. Bottom gas injection is favourable for bath mixing for top–bottom–side blown converters; however, top lance height, top gas flowrate and bath level have little influence.     

转炉溅渣层与镁碳砖炉衬的结合机理

通过对生产现场带有溅渣层的转炉炉衬残砖和试验室小型坩埚溅渣试验结果进行矿相显微结构分析、研究，确定了溅渣层的矿相组成、溅渣层与ＭｇＯ－Ｃ砖结合区域的矿相结构及坩埚溅渣层自上而下的矿相分布规律，并根据矿相结构分析中观察到的烧结层、结合层和溅渣层３个区域，提出了溅渣层与镁碳砖炉衬的结合机理为化学结合、机械镶嵌与化学烧结结合及冷凝结合３种形式。     

转炉溅渣动力学水模型研究

通过对转炉溅渣的水模型研究，提出炉内溅渣的两种动力学机制：发生在转炉上部的气流喷射溅渣和出现在转炉下部的熔池浪涌溅渣。合理平衡两种溅渣机制的综合作用，得到最佳喷吹压力和溅渣枪位，以获得最大的溅渣量。根据上述两种动力学机制，分析炉内氮气射流与液态渣池的作用规律，提出了溅渣高度的理论计算公式。     

Effects of process conditions on mixing between molten iron and slag in smelting reduction vessel via water model study

Abstract

The present study has been conducted to investigate the effects of operating conditions, which include gas flowrate, tuyere size, tuyere number, and height of iron phase, on the extent of mixing between molten iron and molten slag in the direct iron ore smelting reduction process. A transparent acrylic water model, 30% of the size of the actual smelter, was constructed to study the mass transfer phenomena. In the water model, water and spindle oil were used to simulate molten iron and molten slag, respectively, while air was used to replace the bottom blown nitrogen gas. In addition, thymol (C₁₀H₁₄O₆) was used as a tracer material in the water model, added to the water at the beginning of the experiment. As mixing between water and spindle oil proceeded owing to stirring by the bottom blown gas, the concentration of thymol in the water decreased and that in the spindle oil increased. Water samples were taken from the bottom and 12 cm above the bottom of the water model at various operating times. Concentrations of thymol were then measured using a diode array ultraviolet visible spectrophotometer. By analysing the concentration data, the mass transfer rate k_wA, which is a direct index for evaluating the mixing efficiency, could be derived. The process conditions under investigation included 40-500 L min^-1 gas flowrate, 0·3^-1 cm tuyere size, four or five tuyeres, and 20-30 cm height of the water phase. The test results indicate that when the gas flowrate increases, the value of k_wA increases, which indicates better mixing between oil and water phases. However, as the gas flowrate approaches 40 L min^-1, the improvement becomes less obvious. The smaller tuyere gives better mixing, and the design of five tuyeres results in better mixing compared with four tuyeres when they are blown with the same total gas flowrate. However, mixing efficiency decreases with increased height of the water phase. Also, as the gas flowrate of bottom blowing approaches 40 L min^-1, gas blowing from the top has little effect on the mixing behaviour in the liquid bath. For a four tuyere system, the process conditions of height of oil phase 5 cm, height of water phase 25 cm, diameter of tuyere 0·75 cm, and gas flowrate for each tuyere 40 L min^-1, appear to be the optimal design.     

转炉溅渣护炉技术的工艺参数优化

着重对溅渣护炉技术的工艺参数优化过程进行了探讨，确立了溅渣调渣原则，对转炉留渣量、出钢温度、氮气压力和流量，溅渣枪位与时间、溅渣率等工艺参数的控制进行了分析，指出了湘钢条件下的溅渣工艺参数的适宜范围。     

底吹对转炉溅渣护炉的影响

采用水力学模型的研究方法,针对马钢５０ｔ复吹转炉溅渣护炉工艺进行了冷态模拟实验,分析底部吹气流量对溅渣护炉效果的影响,得出的优化工艺参数为：高温溅渣,枪位为１８００ｍｍ左右,喷吹氮气的流量在１１５００Ｎｍ＾３／ｈ以上,压力为１．０ＭＰａ底吹流量控制在４０～８０Ｎｍ＾３／ｈ。     

Numerical Simulation of CO2 Used for Slag Splashing Process in Converter

Utilizing CO₂ for the slag splashing process presents a novel approach that enhances CO₂ utilization in the steel industry and promotes efficient slag splashing. Herein, numerical simulation is employed to investigate the kinetic feasibility of this technique on a 100 t converter. The volume of fluid (VOF) model is utilized to trace the gas–slag interface, while the standard k–ε model is selected to describe the turbulent flow of each phase. Initially, the model is validated via isentropic theory and experimental data. Subsequently, the effects of gas and oxygen lance replacement are evaluated. The results indicate that employing CO₂ solely instead of N₂ leads to a reduction in jet velocity and slag mass flow rates at different positions. However, the utilization of the innovative oxygen lance slows down the jet decay and increases the slag mass flow rate at various heights and sidewalls, except for the lower cone, resulting in a satisfactory slag splashing performance. The present study verifies the feasibility of this new technology and its potential to contribute to CO₂ reduction in the industry positively.     

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。     

Cold Simulation of Oxygen Transfer Rate in BOF

 By measuring the mass transfer coefficient of between water and oil, the oxygen transfer rate of bath in the BOF smelting process is researched, and the influence of top and bottom blowing gas flow rate on the mechanism of mass transfer between metal and slag is discussed. The results show that when the bottom blowing gas flow rate increases on the conditions of top blowing, the mass transfer rate evidently increases, and the influence ratio of top blowing on the mass transfer is 10 percent of bottom blowing; The relation among top gas flow rate, bottom gas flow rate and lance height are established by the stirring power density. The equation between the mass transfer coefficient between metal and slag is formed, which furnishes reference for optimizing process parameters of BOF. The relation between the emulsification ratio between water and oil and the bottom blowing gas flow rate on the condition of top and bottom blowing is obtained. The result shows that with the increase of the bottom blowing gas flow rate the emulsification ratio increases in linearity, which increases the mass transfer rate of benzoic acid between water and oil.     

转炉溅渣护炉的炉渣控制及炉衬侵蚀机理

利用副枪在转炉吹炼过程中取样、测温和对炉衬残砖的化学成分、岩相、流动温度的测定结果,研究了宝钢转炉溅渣护炉炉渣的控制及炉衬侵蚀机理。结果表明：转炉终渣ＭｇＯ含量应控制在１０ ％ 左右、溅渣层的熔损主要发生在炉温较高的吹炼后期,而镁碳砖的侵蚀是由于炉渣渗入镁碳砖的气孔和裂缝中,使其脱碳和渣化,在高温下流入渣层所致。     

长寿复吹转炉工艺技术开发

介绍了长寿复吹转炉在武钢二炼钢80t转炉上应用的基本工艺和冶金效果。通过溅渣，控制底吹喷嘴表面生长炉渣－金属蘑菇头的内部结构、生长高度和供气面积，不仅可保证良好的底部供气功能，而且有效地保护底吹喷嘴不受熔蚀，形成永久性蘑菇头。使底吹喷嘴的一次寿命与溅渣后转炉炉龄同步，并创造了22766炉的世界复吹转炉炉龄纪录。复吹比100％，始终保持良好的复吹冶金效果。     

复吹转炉顶吹枪位与非均衡底吹搅拌的水模拟

为优化120 t复吹转炉冶炼效果,通过水模型试验,模拟研究了复吹转炉底吹强度、顶枪枪位、底吹排布方式和流量分配比对渣 钢间传质效果和熔池混匀时间的影响。研究表明,在相同底吹条件下,顶枪低枪位操作时渣 钢间传质系数比高枪位操作时渣 钢间传质系数大,且随着底吹流量分配比增大,渣 钢间传质系数先增大后减小。在相同顶枪枪位操作条件下,底吹元件间隔排布时,渣 钢界面传质效果总体优于连续排布。随着底吹流量分配比增大,高枪位和低枪位混匀效果变化趋势近似相反。在高枪位下,底吹元件连续排布混匀时间总体少于底吹元件间隔排布时对应的混匀时间;在顶枪低枪位操作条件下,底吹元件连续排布混匀时间总体大于间隔排布混匀时间。通过顶枪枪位、底吹排布和流量分配比的合理匹配,较传统均衡流量底吹模式,传质系数可提高30%～125%,混匀时间可减少8.6%～51.5%。     

A novel approach in the estimation of splashing in the BOF

A new physical model has been developed to represent the splashing behaviour in the BOF. By this technique, which is performed by a relatively simple experimental set‐up, determination of splashing distribution on the walls of the model is possible. The method enables quite fast definition of the effect of different blowing parameters on the location and quantity of liquid splashed. The main advantage of this novel method is the fact that splashes are collected from the whole model wall circumference which is very important when interaction between lance jet cavities and bottom blowing plumes results in irregular splashing distribution. Preliminary results show that the method is excellently suited for investigation of splashing in the BOF.     

重钢85t复吹转炉的水模型试验

通过重钢85 t复吹转炉1∶8的水模型,试验研究了顶枪枪位、底吹流量对转炉熔池混匀时间、炉口喷溅量、冲击深度和液面扰动的影响。实验表明,模型获得最大搅拌能的顶枪枪位为50~100 mm;枪位在90~110 mm时,由射流冲击引起的物理喷溅量达到最大值。建立了重钢85 t转炉复吹工艺参数:冶炼前期顶枪枪位为1600~1760 mm,底吹流量240~350 m³/h;中期两参数分别为1100~1300 mm和160~200 m³/h,后期两参数分别为1040~1120 mm和200~350 m³/h。     

Splashing mechanism in combined blowing

Abstract

In combined BOF blowing, lance parameters and the combination of bottom or side wall tuyeres have an influence on splashing behaviour. The aim of this study was to clarify the interaction of the lance jet cavity with the bottom blowing plume and the side wall blowing jet and to determine its effects on splashing. According to the water model tests, three basic axioms existed in the combined blowing. First, when the bottom tuyere (or side wall tuyere) was located exactly beneath the lance jet, the lowered cavity turned the direction of splashes to lower trajectories. Second, the total amount of splashing was constant and the splashing peak was generated on the wall above the bottom plume. Third, both the plume and the side wall jet formed a so called protected zone beyond it. The model experiments showed clearly that the combination of bottom tuyeres and interaction of cavities and plumes play a very important role in splash generation in real converters.