【作者】 胡汉涛；

【导师】 魏季和；

【作者基本信息】 上海大学 ， 钢铁冶金， 2005， 博士

【摘要】 回顾了钢液RH精炼技术的发展历程和取得的进展,概述了其冶金功能。分析和综述了有关该过程数学和物理模拟研究已有的成果和现状。另外,探讨了关于上升管中液相内气泡的直径和RH精炼过程脱碳机理的研究。 介绍了非平衡态热力学的基本理论。以纯净钢（超低碳钢和超低硫钢）的真空循环（RH）精炼为例,说明了冶金过程的非线性和非平衡性特征,分析了冶金反应工程学和非平衡态热力学的异同,讨论了基于非平衡态热力学和冶金反应工程学的观点、原理和方法研究和处理实际冶金过程的必要性和可行性。指出:为真实地定量描述实际冶金过程,必须充分考虑其非平衡性和非线性的特点;非平衡态热力学在冶金领域应该和能够发挥其作用,应该加强、加速开展和进行冶金过程非平衡态热力学及其应用的研究。对非平衡态热力学线性区的几种特殊情况分析了相应的本构关系、交互作用系数和唯象系数,并简要介绍和评述了已有的一些工作;从热力学稳定性分析出发,评述了非线性非平衡态热力学理论在电解和碳氧反应两个冶金过程中的应用研究。对非平衡态热力学线性区的几种特殊情况分析了相应的本构关系、交互作用系数和唯象系数,并简要介绍和综述了已有的一些工作;从热力学稳定性分析出发,评述了非线性非平衡态热力学理论在铝电解和钢液的脱碳两个冶金过程中的应用研究。 针对90 tRH多功能RH装置,在1∶5的水模型上,测定了钢液的循环流量,采用电导法测定了RH钢包内钢液的混合时间,显示了钢包内液体的流动状态和流场,由此研究了吹气管直径的变化对90 tRH装置内钢液的循环流动和混合特性的影响,得出以下结论:环流量随吹气管直径的增大有所增大,考虑吹气管直径影响的环流量关系为:Q_l∝Q_g^0.23D_u^0.72D_d^0.88d_in^0.13;随着吹气管直径的增大,RH钢包内液体流态基本不变;随着吹气管直径的增大,混合时间略有缩短;在吹气管直径为1.2 mm情况下,混合时间与搅拌能密度的关系为^τm∝ε^-0.49。 基于气—液双流体模型和湍流的修正k-ε模型,提出了RH循环精炼过程中钢液流动的数学模型,确定了模型的有关参数,按等截面喷枪内气体的加热和摩擦流计算了上升管内提升气体的入口参数,由气流和钢液间的穿热估算了提升气体在上升管钢液内所达到的温度。应用该模型对90 tRH装置及线尺寸为其1/5的水模型装置内流体的流动作了模拟和估计,结果表明,该模型可以相当精确地模拟整个RH装置内液体的循环流动;吹入的提升气体主要集中在管壁附近,难以到达上升管的中心部位,存在气体的所谓附壁效应,在实际RH精炼条件下更为更多还原

【Abstract】 The developing history and progresses obtained in the RH refining technology molten steel have been reviewed, and its metallurgical functions were briefly described, the available achievements and present situations for study on physical and mathematical modeling of this refining process have been analyzed and summarized. Also, the investigations of the gas bubble diameter in the liquid in the up-snorkel and the decarburization mechanism during the RH refining process of molten steel have been discussed.The basic fundamentals of non-equilibrium thermodynamics have been introduced and described. Taking the vacuum circulation （RH） refining of clean steel （ultra-low-carbon and ultra-low-sulphur steel） as an example, the non-linear and non-equilibrium features of metallurgical processes have been illustrated. The similarities and differences between metallurgical reaction engineering and non-equilibrium thermodynamics have been analyzed. The necessity and feasibility investigating and dealing with practical metallurgical processes from the viewpoints, fundamentals and methods of non-equilibrium thermodynamics with metallurgical reaction engineering have been discussed. It is pointed out that to get a clear and true understanding of the natures and internal patterns of practical metallurgical processes and really and quantitatively describe the processes, their features of non-linear and non-equilibrium must be fully be taken into account. Non-equilibrium thermodynamics should and can play its proper role in the metallurgical area, and the studies on non-equilibrium thermodynamics of metallurgical processes and its applications should be enhanced and accelerated to develop and carry out. The corresponding constitutive relations between the thermodynamic fluxes and forces, interacting and phenomenological coefficients of a few of special cases located in the linear region of non-equilibrium thermodynamics, have been analyzed. Simultaneously, some available studies in the literature have been briefly introduced and summarized. Proceeded from themodynamic stability, the studies on application of non-linear and non-equilibrium thermodynamics theory to the two metallurgical processes of electrolysis of aluminum and decarburization of molten steel have also been reviewed.The flow and mixing characteristics of molten steel during the vacuum circulation refining were investigated on a 1:5 linear scale water model unit of a 90 t RH degasser, respectively with the diameters of the ports of 1.2 and 0.8 mm. The flow patterns for the two situations were essentially same, and there were no obvious changes. The relation of the circulation flow rate withsome main process parameters at din = 1.2 mm can be expressed as Q₁ ∝ Q_g^0.26D_u^0.69D_d^0.80 , The circulation flow rate slightly increases with an increase of the port diameter and the corresponding relation can be described by Q₁ = 2.40Q_g^0.23D_u^0.72D_d^0.88d_in^0.13 . Relevantly, themixing time little decreases with an increase of the port diameter. The relations of between mixing time and stirring energy density are rm oc eos and T oc e049, respectively at dm = 0.8 mm anddm - 1.2 mm.Based on the two-fluid （Eulerian-Eulerian） model for a gas-liquid two-phase flow and the modified k-s model for turbulent flow, a three-dimensional mathematical model for the flow of the molten steel in the whole degasser during the RH refining process of molten steel has been proposed and developed with considering the physical characteristics of the process, particularly the behaviors of gas-liquid two-phase flow in the up-snorkel and the momentum exchange between the two phases. The related parameters of the model have been determined, and the lifting gas properties at the inlet section in the up-snorkel has been calculated with considering the gas stream in the gas blowing pipe being a heating and friction flow. In addition, the lifting gas temperature reached in the molten steel of the up-snorkel has been determined from the estimated results for the heat transfer between the gas jets and the liquid steel. The fluid flow fields and the gas holdups of liquid phases and others respectively in a 901 RH degasser and its water model unit with a 1/5 linear scale have been computed using this model. The results showed that the flow pattern of molten steel in the whole RH degasser could be well modeled by the model. The liquid can be fully mixed during the refining process except the area close to the free surface of liquid and zone between the two snorkels in the ladle, but there is a boundary layer between the descending liquid stream from the down-snorkel and its surrounding liquid, which is a typical liquid-liquid two phase flow, and the molten steel in the ladle is not in a perfect mixing state. The lifting gas blown is rising mostly near the up-snorkel wall, which is more obvious under the conditions of a practical RH degasser, and the flow pattern of the bubbles and liquid in the up-snorkel is closer to an annular flow. The calculated circulation rates for the model unit at differ-ent lifting gas rates are in good agreement with the determined values.Considering the characteristics of the non-equilibrium decarburization process during the RH refining of molten steel, a new mathematical model has been proposed and developed on the base of the metallurgical reaction engineering and non-equilibrium thermodynamics theories and the two-fluid model for gas-liquid two-phase flow. The details have been presented, including the establishment of the control equations, the determination of the boundary conditions and the source items and the related parameters. The decarburization processes in a 90 t RH degasser under the RH and RH-KTB operating conditions have been computed using this model. The results showed that the carbon and oxygen contents in the molten steel during the refining process could well precisely be modeled using this model. The flow characteristics governed the distributions of the carbon and oxygen concentrations in the molten steel. When the initial carbon concentration is higher than 400x10"4 mass%, the top oxygen blowing can not only supply the oxygen needed for the decarburization process, and accelerate the decarburization更多还原