Mathematical And Physical Simulation On Molten Steel Flow And Snorkel Optimization Design For RH

In the process of RH vacuum refining,one of the most important issues is the fluid circulation flow driven by the gas-bubble-pump effect under vacuum,which is the prerequisite of all physiochemical reactions.The circulation flow rate and the mixing time are the two key parameters of measuring the circular flow.In order to effectively improve the performance of RH vacuum refining,it is necessary to increase the circulation flow rate and shorten the mixing time.Therefore,it is of great significance to study the flow behavior and thereby to optimize the snorkel design of RH.In the present work,based on the previous studies in the literature,two new designs of RH snorkel are proposed to improve the circulation flow rate and the mixing time during the RH refining process.On the one hand,a physical model of RH degasser was constructed based on the principle of similarity and water model study was conducted.On the other hand,mathematical simulation was conducted to get the fluid flow field of different types of RH immersion tube and specifically to explore the flowing behavior in the RH refining process.Through these comprehensive studies,the optimum designs of various snorkels are obtained.The main results are as follows.For the water model study,the scale of the physical model is 1:5.45 of the prototype of RH vacuum refining device.The mixing time and circulation flow of RH device with various snorkels,like round-shaped snorkel,oval-shaped snorkel,arch-shaped snorkel,multi-leg snorkel and annular-shaped snorkel are studied under different gas flow rates and snorkel immersion depths.The conclusions are as follows:(1)Compared with other types of snorkel structure,the arch-shaped snorkel and the annular-shaped snorkel perform the best in the way of improving the circulation flow rate.Under the same condition of immersion depth or gas flow rate,the circulation flow rate of the annular-shaped snorkel is 2-4 times of the round-shaped snorkel,and the circulation flow rate of the arch-shaped snorkel is 7.0～13.0 times of the round-shaped snorkel.(2)Compared with other types of snorkel,the arch-shaped snorkel can remarkably reduce the mixing time.Under the same condition of immersion depth or gas flow rate,the mixing time of the arch-shaped snorkel is 0.4-0.8 times of the round-shaped snorkel.For the numerical simulation,a mathematical model of gas-liquid two-phase flow with the Euler-Euler method is developed.Using this model,the flow field in the vessel is calculated under different conditions of snorkel immersion depth and gas flow rate for RH with various snorkel structures.The main conclusions are as follows:(1)Among all types of snorkel strcture,the arch-shaped snorkel has the best optimizing effect on the flow field of RH.When applying the arch-shaped design,the size and kinetic energy of down flows of RH snorkel get increased significantly.On the lateral and longitudinal cross sections of the ladle,the fluid flow velocity is the greatest and the percentage of the dead zone is the smallest,and thus the fluid in the ladle is mixed effectively.The second is the oval-shaped snorkel.The multi-leg snorkel cannot make an obvious improvement on the flow field of the existing double circular snorkel.(2)With the annular-shaped snorkel,there is a "short circuit" flow between the tubular loop and round pipe,which caused a large-area of dead zones existing in the ladle.Although reducing the thickness of the tubular loop can reduce the trend of the "short circuit" flow,the effect is limited.Therefore,the annular-shaped snorkel also cannot effectively optimize the flow field in RH.