Rhein-Westfalen Technical University — RWTH (Aachen, Germany):

Wuppermann Ch., Mag. Eng., Scientific Fellow

Pfeifer H., Dr. Eng., Director of the Institute of Industrial Furnaces and Heat Engineering

SMS Siemag AG (Düsseldorf, Germany):

Odenthal H.-J., Dr. Eng., Head of Dept. “Theoretical Grounds and Simulation of Melting and Reduction Processes”, hans-juergen.odenthal@sms-siemag.com

Jipnang E., Dr. Eng., Development Eng., “Theoretical Grounds and Simulation of Melting and Reduction Processes” Dept. 

Hovestädt E., Dr. Eng., Head of Development Sector

Schlüter J., Mag. Eng., Head of Dept of Special Innovations

During the AOD process high-chromium melts are decarburized by the injection of process gases through the tuyeres and the top-lance. The movement of gas and melt induces a low-frequency oscillation of the converter vessel. The authors have developed a numerical model which is able to calculate the flow-induced oscillations. The model has been validated by means of water-model experiments. On this basis it is possible to analyze the AOD process even more precisely and to involve design and process control measures in the plant design. The plant test shows that the oscillation amplitude is low when the portion of oxygen in the process gas is high. Vibrations become more intensive as the amount of inert gas in the process gas rises and the inert gas flow rate increases. The type of inert gas affects the oscillation. There is the tendency of nitrogen inducing slightly higher oscillation amplitudes than argon. The frequency is almost independent of the blowing rate. The slight inclination of the vessel during the process increases the vibration level. However, this phenomenon may intensify homogenization due to the higher melt turbulence. The length of the penetrating gas jet into the hot melt is low and can be calculated theoretically The water-model experiments make the flow related phenomena transparent, illustrate the jetting/bubbling regime, flow pattern, oscillation modes, and allow systematic test series. On the numerical side, a major effort was made by developing a CFD model that replaces time-consuming FSI simulations. The new model links CFD with the mechanical assumption of a motion with one degree of freedom; it can be expanded to rotational and translational modes. The vessel oscillation can be simulated and undesirable oscillation modes can be avoided by modification of the converter design or the process conditions.

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