Numerical Simulation Of Interfacial Behavior And Mixing Phenomenon Of Three-phase Fluid Flow In 180t Ladle Bottom-blowing Process

With the continuous improvement of the purity and strength requirements of industrial steel,the out-of-furnace refining technologies have gradually developed and are extensively used in the refining and purification of molten steel.Among these out-of-furnace refining technologies,the ladle bottom blowing argon process is the main process of LF refining technology,and its parameter setting directly affects the refining effect of molten steel.Consequently,in order to promote the uniform stirring of argon to the molten steel and improve the refining quality of the molten steel,it is very vital to set reasonable bottom blowing argon process parameters.In this paper,a 180 t ladle bottom-blowing of a certain factory was taken as the research object.In order to enhance the stirring effect of molten steel and acquire the best bottom blowing process parameters,a three-dimensional multiphase flow mathematical model was developed based on the ladle prototype,and unsteady numerical simulations of bottom blowing argon process were conducted by utilizing the software FLUENT.The specific research contents are as follows:(1)In order to study the effect of the center angle of the double permeable bricks at the bottom of the ladle on the bottom blowing argon process,the distance between the double permeable bricks and the center of the ladle bottom is set to 0.5R,and the ladle models with the center angles of 45°,90°,135° and 180° were established,respectively.The best center angle of double permeable bricks is determined by comparing and analyzing the velocity field characteristics,the proportion of "dead zone",the behavior of steel-slag interface,and the mixing time.It is found that when the center angle of the double permeable bricks is 135°,the flow field characteristics in the ladle are better and the proportion of "dead zone" is effectively reduced.Meanwhile,the slag hole size formed at the steel-slag interface and the mixing time value are both the smallest,which means that the bottom blowing argon shows a better uniform effect on the stirring process of the molten steel in this case.(2)In order to study the influence of the center distance of double permeable bricks on the bottom blowing argon process,the center angle of double permeable bricks was set to be 135°and the ladle models with the center distances of double permeable bricks of 0.3R,0.4R,0.5R,0.6R and 0.7R were established seperately.The velocity field characteristics,the proportion of "dead zone",the steel-slag interface behavior,and the mixing time of the fluid in ladle were calculated and analyzed to determine the optimal center distance of double permeable bricks.The results show that when the center distance of double permeable bricks is 0.6R,the circulation flow in the ladle is distinct,the velocity distribution is fairly well-distributed,the proportion of "dead zone" is the lowest,the slag hole size and mixing time of the steel slag interface are smaller,thus the stirring effect of the liquid steel is the best at this point.(3)Based on the above research,the center angle and distance of the double permeable bricks are set to 135° and 0.6R,respectively,to further explore the effect of the bottom blowing argon flow rate on the bottom blowing process of the ladle.Concurrently,the average velocity of the fluid in the ladle,the proportion of "dead zone",the behavior of the steel-slag interface,and the mixing time were extracted and analyzed to study the optimal bottom blowing argon flow rate.The results indicate that with the increase of bottom blowing flow rate,the velocity of molten steel in the ladle and the proportion of "dead zone" show a trend of gradually increasing and decreasing,respectively,and a relatively obvious circulation flow is formed in the ladle.Meanwhile,the slag hole size formed at the steel-slag interface increases with the increase of bottom blowing argon flow rate,which is due to the higher the bottom blowing argon flow rate,the higher the velocity of horizontal flow,and thus the higher the height of molten steel being carried,leading to a easier slag entrapment.In addition,the simulation results of the critical bottom blowing flow rate and mixing time show that 600NL/min is the best flow rate for the ladle,and the stirring efficiency of molten steel is relatively better.(4)In order to verify the applicability of the above numerical simulation method and the accuracy of the results,the predecessor's water physical model ladle was established and calculated.Moreover,the effect of bottom blowing argon flow rate on the behavior of the steelslag interface in the ladle and the mixing time on the ladle argon blowing process was analyzed.The obtained results are compared with the conclusions of physical experiments.The results show that the numerical simulation results are well-agreed with the previous physical experiments results,which fully verifies the dependability of the numerical simulation method used in this research and the accuracy of the obtained results.