【作者】 耿佃桥；

【导师】 赫冀成； 雷洪；

【作者基本信息】 东北大学 ， 热能工程， 2010， 博士

【摘要】 RH真空精炼是一个涉及多相流、传热及不同化学反应的复杂冶金过程。在实际生产中,提高循环流量、缩短均混时间是提高RH精炼生产效率的重要手段。要充分发挥RH的精炼功效,降低生产成本,就必须对RH内传输过程进行深入研究。本文针对RH精炼装置内钢液流动、脱碳及夹杂物碰撞长大行为分别发展了相应的数学模型,研究了传统侧吹RH、侧底复吹RH和电磁RH内的传输行为;在此基础上针对底吹钢包内夹杂物碰撞聚合行为建立数学模型,研究了钢包底吹方式对夹杂物去除过程的影响,并对双孔底吹钢包的底吹位置进行了优化。研究成果概括如下:一、RH精炼过程中传输行为(1)建立了与RH精炼装置原型1:5.5比例的水模型,考察了不同工艺参数对循环流量、均混时间、顶吹溶氧及脱碳过程的影响,并根据实验数据回归得到循环流量、均混时间的表达式:(2)针对水平侧吹气体行为进行研究,推导了水平侧吹条件下气体穿透深度公式:建立了RH内气液两相流动行为数学模型,数值结果表明提升气量是决定含气率分布的关键因素。(3)发展了综合RH不同脱碳机理的三维数学模型及夹杂物碰撞长大行为的均相模型,讨论了不同工艺因素对夹杂物去除过程的影响;通过将Stokes碰撞应用于夹杂物数量及质量守恒模型,建立了RH装置内夹杂物碰撞长大行为的数学模型,给出了夹杂物数量密度及浓度的三维空间分布。二、侧底复吹及电磁RH精炼过程中传输行为(1)在钢包底吹条件下,当底吹位置和钢包中心连线与浸渍管中心连线的夹角θ=0时,循环流量随底吹位置至钢包中心距离L的增大先增大后减小,均混时间随L的增大而增大;当L=0.535m时,循环流量随夹角θ的增大而减小,均混时间随夹角θ的增大先减小后增大。(2)在施加行波磁场条件下,循环流量随励磁电流强度的增加而增大,均混时间随电流强度的增大而减小,并且二者与电流强度近似成线性关系;电流频率在10～30Hz变化时,循环流量随电流频率的增大而增大,均混时间随电流频率的增大而减小;在30～60Hz变化时,循环流量随电流频率的增大而减小,均混时间随电流频率的增大而增大;提升气量小于饱和值时,在上升管周围施加行波磁场优于在下降管周围施加行波磁场;提升气量大于饱和值时,二者效果等同;同时在上升管和下降管周围施加行波磁场的脱碳及夹杂物去除效率最高,仅在上升管周围施加行波磁场次之。三、底吹钢包内传输行为(1)在夹杂物数量及质量守恒模型中引入气泡吸附夹杂物模型,建立了钢包内夹杂物去除过程的三维数学模型,结果表明:底吹方式是影响夹杂物去除的重要因素;三孔底吹效果最好,双孔底吹次之,偏心底吹优于中心底吹;顶渣吸附是最重要的夹杂物去除方式,侧壁吸附次之,钢包底壁吸附可忽略不计。(2)针对双孔底吹钢包的底吹位置进行优化,结果表明:在底吹位置偏移中心距离一定的条件下,底吹位置与中心连线夹角存在一个最优值,反之亦然;回归实验数据可得双孔底吹钢包的均混时间表达式如下:更多还原

【Abstract】 RH vacuum refining is a complicated metallurgical process which involves in multiphase flow, heat transfer and various chemical reactions. By increasing circulation flow rate and shortening mixing time, the RH production rate can be increased in actual system. Therefore, in order to take full advantage of the production efficiency of RH degasser and reduce production costs, it is necessary to have a deep insight into the transport process in RH.In present work, several mathematical models have been developed to study the gas-liquid flow, decarburization process and the collision and growth among inclusions. The transport behavior in RH with traditional side blowing, RH with side-bottom blowing and electromagnetic RH have been investigated by the above mathematical models. On this basis, the mathematical model concerning collision and coalescence among inclusions in gas-stirred ladle has been developed to study the effect of different types of bottom blowing on the inclusion removal process. In addition, the double bottom blowing locations in ladle have been optimized. The results are as follows:I. The transport behavior during RH vacuum refining process(1) A 1: 5.5 scale water modeling of the RH prototype has been developed and the effects of different operating parameters on the circulation flow rate, mixing time, top blowing oxygen absorption and decarburization process have been investigated. By regression on the base of experimental data, the empirical correlations for the circulation flow rate and mixing time are as follows:(2) The side-blowing gas behavior has been studied and the formula for the horizontally blowing gas penetration depth is as follows:A mathematical model of gas-liquid flow in RH degasser has been developed and the numerical results show that the lifting gas flow rate is the key factor to determine the distribution of gas holdup.(3) A three dimensional mathematical model considering different decarburization mechanisms and a homogeneous model concerning the collision and growth among inclusions in RH degasser have been developed to investigate the effects of different operating parameters on the inclusion removal process. By introducing the Stokes collision among inclusions into the inclusion mass and number conservation model, a mathematical model about inclusion behavior in RH degasser has been developed to give the three dimensional spatial distributions of inclusion number density and concentration in RH degasser.II. The transport behaviors during RH with side-bottom blowing and electromagnetic RH(1) For RH with bottom blowing, when the included angle of the line between bottom blowing location and ladle center and the line between two snorkels 0 is zero, the circulation flow rate increases with the increasing distance between bottom blowing location and ladle center L firstly, and then decreases. In addition, the mixing time increases with the increasing L. When L is equal to 0.535m, the circulation flow rate decreases with the increasing 6. In addition, the mixing time decreases with the increasing 9 firstly, and then increases.(2) For RH imposed by traveling magnetic field, with the increasing current density, the circulation flow rate increases linearly and the mixing time decreases linearly. If the current frequency lies in the range of 10～30Hz, with the increasing current frequency, the circulation flow rate increases while the mixing time decreases. If the current frequency lies in the range of 30～60Hz, with the increasing current frequency, the circulation flow rate decreases while the mixing time increases. In order to increase circulation flow rate and shorten mixing time, the most effective measure is to apply the traveling magnetic field near the up snorkel, and the second choice is to apply the traveling magnetic field near the down snorkel if the gas flow rate is smaller than the saturation value. However, such a difference disappears if the gas flow rate is greater than the saturation value. For decarburization and inclusion removal, the most effective measure is to apply the traveling magnetic field near the up and down snorkels, and to apply the traveling magnetic field near the up snorkel has the minor effect.III. The transport behavior in the gas-stirred ladle(1) By introducing the model of inclusion adhesion to gas bubble into the inclusion mass and number conservation model, a three dimensional mathematical model is developed to investigate the inclusion removal process in ladle. The numerical results show that the type of bottom blowing is the key factor for inclusion removal. The triple bottom blowing is the most effective method for inclusion removal, while the double bottom blowing has a minor effect and the eccentric bottom blowing is better than the centric bottom blowing. For inclusion removal, the absorption by the top slag is the main manner, the adhesion to the sidewall is the minor manner, and adhesion to the bottom wall can be negligible.(2) The double bottom blowing locations in ladle have also been optimized and the results show that there is a unique optimum offset of double blowing locations for a particular included angle and vice versa. The correction for the mixing time for the ladle with double bottom blowing can be expressed as:更多还原