Simulation Study On Bubble Breakup And Aggregation Behavior During Bottom-blown Argon Ladle Refining

Refining process is the important link and guarantee to realize high purification of steel.Bottom blowing argon is the most widely used refining method.The bubble size and distribution in the molten pool have a significant impact on the steel flow,blending components and inclusion removal.Given that the bubble breakup and coalescence mechanisms in the gas-stirred ladle refining process are not clear,and the bubble size and distribution in the molten pool have not been revealed and grasped yet,the research combined physical water model experiment and numerical simulation to study on the bubble breakup and coalescence behavior and mechanisms.The bubble breakup and coalescence mechanisms were revealed.The mathematical model was established accurately to describe bubble behavior in ladles.On the basis of the research,the influence rules of different process parameters on the bubble behavior were revealed,and the theory basis was laid for truly reappearing bubble behavior in the gas-liquid two phase flow of gas-stirred ladles.The main research results are as follows:(1)Based on the similarity principle,the physical water model of gas-stirred ladle was established.By the study of water model experiment,it was found that with the increase of gas flow rate,gas holdup and bubble size both increased gradually,and the gas holdup radial distribution became more uneven.As the height increases,the bubble size increased gradually and the gas holdup decreased gradually.When the bubble size and the gas holdup reached a certain height,the changes tended to be stable and reached an balanced distribution.(2)The empirical formulas for the sauter mean diameter of the initial bubbles formed by slit component and dispersive component under the current bottom blowing system were derived respectively by dimensional analysis method and physical water model experimental data.(3)By establishing the CFD-PBM coupling mathematical model,the behavior of bubble breakup and coalescence in the gas-stirred ladle refining process was described accurately.The mechanisms of bubble breakup and coalescence in the gas-stirred ladle and their influence on bubble size distribution were revealed.The study established the mechanism of bubble size distribution dominated by bubble coalescence.It is proved that the collision between bubbles is mainly caused by turbulent random movement of bubbles and bubbles floating up.By modifying the parameter of the coalescence efficiency model,the mathematical model which can accurately describe the bubble size distribution in the gas-stirred ladle was obtained.(4)The influence rules of various process parameters on the bubble size distribution under the current bottom blowing system were revealed.It was found that with the increase of gas flow rate,the radial distribution of bubble size became wider and the bubble size increased.At the same air flow rate,the bubble size in the molten pool was significantly smaller using the dispersive component compared with using the slit component.At the same gas flow rate,the bubble size in the molten pool is larger when the component was arranged at 1/2 eccentric location,while the bubble size in the molten pool is smaller when the component was arranged in the center location.