Physical and Mathematical Modeling of the Vessel Oscillation in the AOD Process

The argon-oxygen-decarburization (AOD) process is a common metallurgical treatment to decarburize high-chromium steel melts using oxygen and inert gas injection through sidewall tuyeres and a top-lance. AOD converters are characterized by a fast and efficient decarburization, whereby the oxidation of chromium is reduced compared to treatments for regular steel grades like the LD process. However, low-frequency oscillations with large amplitudes can occur during the process and influence the converter's structural integrity. The aim of plant engineering is the development of an AOD converter using a vessel design that provides a fast decarburization rate and effective mixing, whereby the oscillation's amplitude and the chromium losses are as low as possible. The oscillation of the vessel is induced by the fluid flow. In this study a numerical model is presented, where the oscillation model is integrated in the CFD (computational fluid dynamics) solver by subroutines. The numerical models for both, fluid flow and vessel oscillation, are validated by experiments carried out with a 1:4 scale water model. In a further step, the numerical models are transferred to the actual AOD process. The results of the simulations are compared to experimental results obtained in plant trials. The numerical model developed in the present study can be used as a tool to design AOD vessels that fulfill the above mentioned criteria to satisfy an efficient, reliable and stable process.