As an efficient oxygen supplying technology, coherent jets are widely applied in electric arc furnace (EAF) steelmaking processes to strengthen chemical energy input, speed up smelting rhythm, and promote the uniformity of molten bath temperature and compositions. Recently, the coherent jet with CO2 and O-2 mixed injection (COMI) was proposed and demonstrated great application potentiality in reducing the dust production in EAF steelmaking. In the present study, based on the eddy dissipation concept model, a computational fluid dynamics model of coherent jets with COMI was built with the overall and detailed chemical kinetic mechanisms (GRI-Mech 3.0). Compared with one-step combustion reaction, GRI-Mech 3.0 consists of 325 elementary reactions with 53 components and can predict more accurate results. The numerical simulation results were validated by the combustion experiment data. The jet behavior and the fluid flow characteristics of coherent jets with COMI under 298 K and 1700 K (25 degrees C and 1427 degrees C) were studied and the results showed that for coherent jets with COMI, the chemical effect of CO2 significantly weakened the shrouding combustion reactions of CH4 and the relative importance of the chemical effect of CO2 increases with CO2 concentration increasing. The potential core length of coherent jet decreases with the volume fraction of CO2 increasing. Moreover, it also can be found that the potential core length of coherent jets was prolonged with higher ambient temperature. (C) The Minerals, Metals & Materials Society and ASM International 2018

A new type of oxygen-supplying technology was developed for electric arc furnace (EAF) steelmaking using submerged CO2 and O-2 mixed injection (S-COMI). S-COMI injects O-2 into the molten steel bath directly by a submerged injector installed in the furnace bed; so the metallurgical reactions can be accelerated with a high utilization ratio of oxygen. However, there has been limited research on the impact characteristics of the S-COMI submerged gas jet in EAF steelmaking. In this study, water model experiments and numerical simulations were carried out to analyze the submerged gas jet behavior, and a theoretical model was built to depict the axis trajectory of submerged gas jet in the liquid bath. The numerical results were validated against the water model experiments to show that the gas flow rate and the installed angle have a significant influence on the jet impact characteristics. The results show that as the gas flow rate increases, the horizontal and vertical penetration distances increase; as the installed angle increases, the horizontal penetration distance increases while the vertical penetration distance decreases. In addition, the erosion mechanism of the element around the submerged injector exit was studied. As the installed angle increases, the velocity component in the vertical direction increases, the fluid flow is accelerated, and the wall shear stress of the underpart of the injector element increases. Therefore, the erosion rate of the upper part of the element decreases, while that of the underpart increases.

In the steelmaking industry, the utilization of CO2 as a resource has become one of the important research projects. The decarburization and desilication mechanism were investigated to the extension range of low carbon condition and in Fe–C–Si ternary system in 1 873 K. 13CO2 and 18O2 dual isotope gases were use to clarify the complicated oxidation process. The results showed that in Fe-1.0 mass%C-0.5 mass%Si molten alloy, CO2 substitution part of O2 within 40% slightly reduced the decarburization rates in the advantage area of decarburization, and after reaching the oxidation equilibrium curve, the decarburization rates were basically stable and low even 100% CO2. However, with introducing CO2 from 0 to 40%, the desilication rates were dropped a lot. CO2 replacing part of O2 was beneficial to reducing the loss of silicon during decarburization process at 1 873 K. The critical value of carbon content was around 0.3 mass%, that the main limiting rate step was transformed to the diffusion of carbon in molten under the correspondindg condition of 1.2 to 3.2 Nm3/t·min gas supply intensity in the present experiments. When the gas supply was sufficient, CO2 participation ratio was decreased and that of O2 was increased with the carbon content decreasing. When the gas supply was insufficient, both CO2 and O2 participation ratios were relatively stable until the carbon transfer limiting the reactions. © 2025 The Iron and Steel Institute of Japan.

二氧化碳的大量排放使人类面临全球变暖的严峻问题。2019年我国粗钢产量达到9.969亿吨。长流程产量约占85%,生产1吨钢约产生2.2吨CO2;短流程产量约占15%,生产1吨钢约产生0.8吨CO2。我国钢铁工业2019年总计约产生了19.82亿吨CO2。钢铁生产中几乎所有工序均会产生CO2,如烧结、炼铁、炼钢等。如何高效利用生产过程中排放的CO2,已为国内外众多冶金工作者所重视,并相继开展应用研究。本研究在课题组前期研究基础上,开展了CO2-O2混合底吹和顶底复吹进行炼钢的实验研究,讨论了不同喷吹模式下CO2对于提钒过程的影响,确定了不同喷吹模式下CO2的最佳喷吹比例和合适的起始喷吹温度和气体喷吹总流量。这对于进一步开展CO2在含钒铁水中提钒的生产应用,具有理论和实际指导意义。在本实验条件下,得到了如下结论。（1）CO2-O2混合底吹实验表明,CO2喷吹比例在10%至25%变化时,当其比例为15%时具有最佳的提钒效果,钒的氧化率最高,氧化率为95.65%;此时碳的氧化率最低,氧化率为30.87%。（2）通过开展顶部喷吹O2,底部喷吹CO2气体的顶底复吹实验,表明,当CO2比例从10%逐渐增加至25%时,钒的氧化率先增大后减小。当CO2比例为20%时达到最大值,钒氧化率为94.70%;此时碳氧化率最低,氧化率为27.83%。（3）在上述两种喷吹模式下,起始喷吹温度为1300 oC和喷吹流量为0.6 L/min（约1.714 L/（min·kg））时有利于提钒保碳。

我国钢铁行业的CO2排放量约占全国CO2排放总量的15%,少数钢铁企业开展了工业尾气CO2捕集利用的工程建设,但原料气气源石灰窑和热电厂尾气中的CO2含量普遍小于30%,且石灰窑和热电厂区域距离转炉冶炼区域较远,造成CO2捕集项目的投资运行成本、能耗和占地面积大幅度增加。基于此,本文提出了“转炉炼钢CO-CO2质能转换自循环利用”的新工艺思路,采用转炉煤气富氧燃烧富集烟气中的CO2,降低CO2捕集的投资和运行成本,有助于推动钢铁企业大规模捕集CO2资源化利用技术的发展。分析了助燃气成分、当量比、循环烟气和预热温度对于转炉煤气富氧燃烧特性及烟气性质的影响,确定了当量比为0.9的SCH-3为最适合CO2捕集工序的燃烧方案;经过4次循环的烟气中CO2含量稳定在74.32%,预热温度降低了烟气中NOx的生成量,但对烟气中C02含量没有影响。研究了不同CO2捕集流程的碳排放及（火用）效率,发现C-PRO-1、C-PRO-2、C-PRO-3 和 C-PRO-4 流程的碳排因子分别 为 3.7811 tCO2/km3、3.2057 tCO2/km3、1.8553tCO2/km3 和 0.8701tCO2/km3,产品（火用）效率分别为 9.76%、6.71%、4.34%和 4.51%,而回收（火用）效率分别为 9.76%、6.71%、18.27%和 19.01%。建立了转炉顶底复吹CO2冶炼的物料平衡和能量平衡模型,开展了 CO2冶炼工业试验,确定CO2喷吹最大比例为14.71%,且煤气和蒸汽循环作为捕集工序的输入项不会影响能源平衡;U-BOU-1边界和U-BOU-2边界的CO2排放量分别为165.5 kg/t钢和138.2 kg/t钢,（火用）损失分别为7.17%和5.98%,（火用）效率分别为92.83%和94.02%,主产品（火用）效率分别为84.75%和85.01%。评估了新工艺思路（PRO-4流程）的碳排放、（火用）效率和经济性指标,发现PRO-4流程的CO2排放量为0.1404t/t钢,相比常规冶炼、PRO-1、PRO-2和PRO-3流程的CO2排放量分别减少了 25.13 kgCO2/t钢、16.91 kgC02/t钢、13.57 kgCO2/t 钢和 5.72 kgCO2/t 钢;C-PRO-4 流程的运行成本为 247.64 元/km3CO2,相比 C-PRO-1、C-PRO-2 和 C-PRO-3 流程分别降低了 39.5%、55.5%和 26.3%。本文的研究成果将为“转炉炼钢CO-CO2质能转换自循环利用”新工艺提供参考依据,有助于钢铁企业CO2捕集利用技术的进一步发展。

CO2是冶金工业广泛使用的气体之一,可以作为反应气体、保护气体和搅拌气体。在转炉提钒工艺中,CO2作为反应气体具有弱氧化性与低放热性特点,可以减缓熔炼过程中的熔池升温速度,从而获得较好的提钒保碳效果。在课题组已成功实现CO2-O2混合喷吹进行提钒实验的背景下,本研究提出将CO2作为复吹提钒底吹气体的思路,将CO2同时作为搅拌气体和反应气体来达到提钒保碳的目的,从而为CO2应用于复吹提钒提供理论基础,具有重要的实践意义。本研究结合理论计算与实验室模拟顶底复吹提钒工艺的形式进行了提钒保碳工艺研究,受到了国家自然科学基金资助（51334001）。在本实验条件下,得到了如下主要结论:（1）与混合喷吹相比,复合喷吹可以提升CO2参与反应比例约5%,缩短提钒时间约1min,降低熔池温度约3-7 oC。复合喷吹时CO2最佳喷吹比例为20%,临界温度为1347-1363 oC。（2）适当增强底吹强度有利于提钒保碳,底吹CO2流量每增加10%,熔池温度降低5-7 oC左右,CO2参与反应减少熔池放热约1.3857-2.0214kJ。（3）阶梯喷吹有利于提升提钒保碳效果,为了获得较好的提钒保碳效果,阶梯喷吹的反应初始温度不应高于1340 oC,最佳初始温度为1300 oC,最佳初始比例为15%。（4）扩大实验证明复合喷吹一定比例CO2可以较好地实现提钒保碳效果。复合喷吹有利于降低渣中全铁含量,大幅提升钒在渣金间的分配比,从而提高钒渣品位。复合喷吹的终点钒渣主要物相为Fe2VO4与Fe3O4。

Fe-V-O体系的基础热力学研究可为转炉提钒冶炼、高强度低合金钢的冶炼、钒基耐蚀钢的腐蚀机理、含钒冶金渣提取及火电厂含钒废料处理工艺等工业生产提供重要理论指导,关于该体系的热力学研究始终处于国内外的难点及热点研究领域。由于缺少Fe-V-O系的热力学数据库,目前无法利用热力学计算软件对工业生产中涉及到Fe-V-O系或Fe-V-Si-O系的热力学问题进行准确的计算。本文将围绕Fe-V-O体系的热力学建模和参数优化展开系列研究,旨在构建可靠的Fe-V-Si-O系热力学数据库,进而为含钒多元多相体系的热力学计算提供理论依据。目前,弱氧化性的CO2已被证明有控制转炉氧势及熔池温度的作用,可作为转炉铁水提钒过程中的清洁冷却剂,同时达到节能减排的目的。采用本研究所优化的Fe-V-Si-O系热力学数据库对CO2应用于铁水提钒过程进行热力学分析和计算,同时开展CO2-O2混合气体喷吹铁水提钒系列实验,检验数据库的准确性,为提钒工艺优化提供重要的理论支撑。论文首先针对钒铁尖晶石相进行热力学优化研究。基于CALPHAD（CALculation of PHAse Diagram）技术,在复合能量模型（Compound Energy Formalism,CEF）框架内建立Fe3O4-FeV2O4全成分范围内的钒铁尖晶石相的热力学模型,采用晶体场理论（Crystal Field Theory）对两种亚晶格（四面体和八面体）位点之间的阳离子稳定能及阳离子分布进行计算和模拟,建立了符合尖晶石物理结构的结构模型(Fe2+,Fe3+,V3+)T[Fe2+,Fe3+,V3+,Va]2OO4,计算出Fe2+-V3+离子对的位点稳定能为71 kJ。将优化后的一组包含体系中每个物相、相互自洽的热力学参数加载至以吉布斯自由能最小化为计算准则的FactSage软件,可对全成分范围内的钒铁尖晶石相的微观性质（阳离子在亚晶格间的分布）与宏观热力学性质（吉布斯自由能、平衡氧分压、活度、混合自由能等）进行准确计算,且理论计算值与其它作者的实验值在实验误差范围内吻合。随后对Fe-V-O体系热力学优化和数据库建立进行研究。针对文献中1 atm条件下Fe-V-O体系的热力学性质和相平衡实验数据进行了综合评价和热力学优化,其中氧分压的变化范围为空气条件（0.21 atm）至还原气氛条件(10-16 atm)。Fe-V-O体系中化学计量化合物如FeVO4,FeV2O6,FeV6O15和Fe2V4O13的?H~0298 K、S~0298 K、Cp等关键热力学参数均被合理优化,并使用Braggs-Williams随机混合模型对维氏体相、刚玉相和VO2固溶体相进行描述,通过改进的准化学模型（Modified Quasichemical Model）对熔渣相进行建模,其中涵盖了钒和铁的所有价态(Fe2+,Fe3+,V2+,V3+,V4+和V5+)。本研究采用的关于溶液的热力学模型均基于它们（熔渣、尖晶石固溶体、维氏体和刚玉相等）本身物理结构性质所建立,因此溶液的构型熵可在该研究的热力学模型中得到体现。优化后的热力学模型参数可在编译器中整合为数据库,并加载于FactSage计算软件,以准确计算出不同条件下（温度、组分及氧分压）的多种热力学性质。本研究通过计算值与实验值的吻合度验证模拟的精度和准确性。此外,利用Kohler和Toop几何模型对优化后的二元热力学参数向Fe-V-Si-O体系进行外延预测,且理论计算值与其它作者的实验值吻合度很好,证明了该Fe-V-Si-O数据库具有可靠的拓展性。继而探索出利用CO2控制提钒氧势及熔池温度的铁水提钒新工艺。基于本研究建立的Fe-V-Si-O数据库进行气-渣-金三相热力学计算,开展CO2-O2混合气体喷吹铁水提钒实验,验证了这两种新工艺的可行性以及清洁、高效冷却的冶金效果,同时验证了数据库的可靠性。热力学计算和实验研究表明:纯CO2喷吹时能与熔体内的V、Fe、C等元素发生氧化还原反应,且产物CO会改变气相平衡条件,延缓碳元素的继续氧化。此外,CO2与铁水中含量最多的Fe、C反应时会吸收热量从而促进提钒反应,经计算CO2的冷却能力为9426.6 kJ/m~3,可替代工业转炉提钒过程中传统固体冷却剂。CO2-O2混合喷吹工艺采用顶吹的方式更具有提钒保碳的优势,CO2含量在0-15 vol.%时表现为以吸热控温为主的作用机理,有利于提钒保碳;CO2含量在15-25 vol.%时表现为以弱氧化性为主的作用机理,在此区间提钒效率变低。当初始温度为1300°C时,顶吹混合气体中CO2的最佳占比为15%,在供氧强度为1.5 m~3/（t·min）时持续喷吹混合气体10 min后,钒的氧化率为94.4%,且钒氧化率与碳氧化率的比值相比于其他混合方式最大,说明该喷吹方式提钒保碳的能力最强。此时终点熔池温度相比纯氧喷吹降低约20°C,耗氧量相比纯氧喷吹减少了1 Nm~3/吨铁水。同时,经热力学计算及高温实验研究表明,CaCO3作为一种固体冷却剂,冶炼中可在线分解出CO2,对熔池的冷却效果也非常显著。在铁水提钒过程中添加CaCO3后对熔池碳元素的氧化几乎没有影响,且随添加量的增加,钒的氧化率会有轻微的提升,钒渣脱磷能力则大幅增强。当加入铁水质量1.3%的CaCO3后,钒渣中P2O5含量从0.12 wt.%增加到0.32 wt.%,有利于工业冶炼高磷钒钛磁铁矿。本工艺后续可进行钙化焙烧并搭配酸浸处理的方法,进一步实现对钒的绿色提取。

To develop CO2 utilization technology in converter process, it is necessary to study the chemical reactions of the CO2–O2 mixed gas in the cavity.13CO2–18O2 dual isotope gas was used to distinguish the complex reactions and analyzed the effect of injection height. The results show that as the injection height increased from 10 to 30 mm, the influence of CO2 participating in the reaction is relatively unobvious; regarding O2, the flowrate of uninvolved reaction increases; the flowrate of post combustion increases first and then decreases; the flowrate of O2 directly involved in decarburization is basically stable in the range of 20–30 mm after decreasing. Maintaining the injection height of 20 mm, the O2 flowrates of post combustion in the ranges of 0–5 mm, 5–10 mm, and 10–15 mm are 4.95 mL·min− 1, 13.85 mL·min− 1 and 6.73 mL·min− 1, respectively. It can reduce the waste of mixed gas due to post combustion and improve the quality of furnace gas if the injection height is not in the range of high post combustion ratio. © 2023 The Iron and Steel Institute of Japan.

An increasing number of people have been giving attention to the application of CO2 in the steelmaking process. To determine the optimal substitution ratio of blowing O-2 with CO2, a thermodynamic analysis and a mass spectrometry monitoring experiment of gas composition changes during O-2-CO2 decarburization were used to build a better O-2-CO2 mixed injection pattern. The decarburization process is divided into the first, middle, and final stages to analyze the effect of different ratios of mixed gas at different stages. The results show that using O-2-CO2 mixed gas in the first or middle stage is more conducive to adjusting the temperature of the molten bath; however, using mixed gas in the middle or final stage is more conducive to improving the quality of the furnace gas and saving more oxygen. Based on the thermodynamic calculation, the injection pattern of 70% O-2-30% CO2 gas in the middle stage and pure oxygen in other stages can save 6.3% O-2 and increase the CO proportion of gaseous products by 1.2% comparing to those of conventional pure O-2 blowing in the whole process. Moreover, based on the mass spectrometry method, middle stage at 1773 K and with 2 mass% [C] has the best decarburization kinetic conditions, and its overall reaction rates are larger than the first stage at 1573 K and 3.5 mass% [C] and final stage at 1873 K and 0.5 mass% [C] as long as P-O2 is larger than 0.4 atm. The CO proportion of the outlet gas improves by more than 2.0% when the CO2 substitution ratio in the O-2-CO2 mixed gas is 30% or 40% which is consistent with the thermodynamic calculation results.[GRAPHICS]