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.

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。

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]

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 O2 with CO2, a thermodynamic analysis and a mass spectrometry monitoring experiment of gas composition changes during O2–CO2 decarburization were used to build a better O2–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 O2–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% O2–30% CO2 gas in the middle stage and pure oxygen in other stages can save 6.3% O2 and increase the CO proportion of gaseous products by 1.2% comparing to those of conventional pure O2 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 PO2 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 O2-CO2 mixed gas is 30% or 40% which is consistent with the thermodynamic calculation results. Graphical Abstract: [Figure not available: see fulltext.] © 2022, The Minerals, Metals & Materials Society.

Adding polypropylene (PP) fibers and coarse aggregates has become a popular way to enhance the strength and stability of the cemented tailings backfilling (CTB) body. It is essential to explore the influence of tailings-aggregate ratio and fiber content on the mechanical properties of CTB samples. The comprehensive tests of the unconfined compressive strength (UCS), slump and microstructure were designed, and the regression models were established to characterize the effect of the strength, ductility and fluidity. The results indicate that the tailings-aggregate ratio of 5:5 and PP fiber content of 0.5 kg/m(3) are the optimum point considering the UCS, cracking strain, peak strain and post-peak ductility. The tailings-aggregate ratio is consistent with the unary quadratic to the UCS and a linear model with a negative slope to the slump. Microstructural analysis indicates that PP fiber tends to bridge the cracks and rod-mill sand to serve as the skeleton of the paste matrix, which can enhance the compactness and improve the ductility of the CTB. The results presented here are of great significance to the understanding and application of coarse aggregates and fibers to improve the mechanical properties of CTB.