A Mathematical Modeling Study of Bubble Formations in a Molten Steel Bath
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IN modern steelmaking processes, gas is often injected into the molten steel through tuyeres or porous plugs to increase the thermal and chemical homogenization of the melts as well as to help remove inclusions from the steel bath. This is good for improving the production quality. The bubble formation from the gas injection devices plays an important role in a variety of steelmaking operations such as the gas-stirred ladle; the investigation of the gas stirring effect relies much on the ability to predict the bubble dynamics. Therefore, it is necessary to understand the evolution of bubble formations in the molten steel from a scientific research point of view as well as for industrial engineers. Plenty of bubble formation work has been done in the field of chemical engineering.[1–4] However, studies on this topic in liquid metals are relatively scarce. An experimental approach utilizing noises generated by bubbles in tin, lead, or copper melts was used to determine the bubble formation frequencies and bubble rising velocities by Andreini et al.[5] In addition, Davis et al.[6] reported the individual bubble rising through a low-temperature metallic alloy through the use of X-ray YONGGUI XU, Ph.D. Student, MIKAEL ERSSON, Assistant Professor, and PA¨R GO¨RAN JO¨NSSON, Professor, are with the Division of Applied Process Metallurgy, Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Brinellva¨gen 23, 100 44 Stockholm, Sweden. Contact e-mail: [email protected] Manuscript submitted March 24, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
cinematography. Irons et al.[7] studied the size of gas bubbles formed at nozzles in liquid pig iron by measuring the frequency of bubble formation with an acoustic device. They[8] also studied the bubbling behavior in molten metals with non-wetted nozzles at low gas flow rates. Also, Mori et al.[9] observed the behavior of nitrogen injecting into a mercury bath through a transparent bottom plate using a high-speed cinecamera. Iguchi et al.[10] observed the formation of bubbles at a nozzle and the subsequent rising behavior of them in a molten iron bath at 1523 K (1250°C) using a high-voltage X-ray fluoroscope and a high-speed video camera. Furthermore, Iguchi et al.[11] developed a two-needle electroresistivity probe to measure bubble characteristics in a molten iron bath at 1873 K (1600°C). A water model study of bubble formation under reduced and elevated pressures was also carried out by Iguchi et al.[12] However, the application of different measurement methods is limited due to the high temperatures and nontransparent liquids of industrial melts. Fortunately, numerical simulations represent a promising method to provide information on the bubble behaviors in steel melts. Over the past decades, significant progress has been made in computational fluid dynamics (CFD). Several numerical attempts have been tried to describe the gas–liquid multiphase flow in a quantitative sense. Here, the multiphase simulation methods can be categorized from the point of the sc
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