Simulation of Fluid Flow and Oscillation of the Argon Oxygen Decarburization (AOD) Process

Abstract

The oscillation of argon oxygen decarburization (AOD) converters is flow related and depends on the process parameters (e.g., vessel geometry, melt fill height, process gas type and blowing rate, vessel tilting angle, as well as geometry, number, and arrangement of the side-wall nozzles). For a 120-ton AOD converter with seven submerged side-wall nozzles, plant tests, physical simulations on a 1:4 scale water model, and computational fluid dynamics simulations have been done. The investigations show that the penetration depth of an inert gas jet into the melt does not exceed approximately 0.4 m. The plumes are located close to the nozzle-side converter wall and induce a large-scale primary vortex as well as intensive surface movements; both are responsible for the oscillation. Several process mechanisms were investigated. The oscillation is highest in the last stage of the dynamic blow and is still high during the reduction stage. As the amount of inert gas increases, the vibration level also increases. Inert gas has a greater influence on the oscillation than oxygen. Tilting the converter around 8 deg clearly leads to more intensive oscillations. Increasing the blowing rate increases the forces and torques acting on the vessel, whereas the oscillation frequency remains nearly constant. A varying fill level does not influence the vibration level the same way as the blowing rate. The operational test shows, for example, that the maximum torque does not depend on the heat size when the latter varies between -8 pct and +21 pct of the nominal heat size. The water model test shows decreasing forces and torques with a rising fill level.

Review on CFD Simulation and Modeling of Decarburization Processes

“…Odenthal [44] 2010 AOD 3D Transient Realizable k-e/ SST-SAS Side blowing, oscillations Wang [23] 2010…”

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

“…The jet injection and the trajectory of the plume are characterized by the modified Froude number, which is commonly used in literature as criterion to reach kinematic similarity between AOD converters, prototypes and water models. 18,19) ............. (3) ρg Gas density at the tuyere exit in kg/m³ ρl Liquid density in kg/m³ g Gravity, 9.81 m/s² ug Mean gas velocity at the tuyere exit in m/s Dt Tuyere diameter in m Gas density and velocity at the tuyere exit have to be calculated in terms of gas dynamics, as the flow in the tuyere exceeds Ma > 0.3.…”

“…This tendency is also described elsewhere. 3,4) The data shown in Fig. 1 was carried out in plant trials on a 120 ton AOD vessel.…”

“…2 and described by various authors. 3,[5][6][7][8][9] Thus, the stirring energy of the argon bubbles, which are predominant during the AOD reduction process stage, is introduced into the melt. The transfer of forces between fluid and vessel is caused by the shear and pressure forces acting on the walls.…”

A Novel Approach to Determine the Mixing Time in a Water Model of an AOD Converter

“…The drag force between gas and melt leads to the characteristic AOD flow pattern described by various authors. [2][3][4][5][6] Thus, the stirring energy of the argon bubbles, which are predominant during the AOD reduction process stage, is introduced into the melt. The process variables, which determine the stirring effect for a given multiphase system, are the vessel and tuyere geometry, the number of tuyeres, the angle between the tuyeres, the melt capacity and the volume flow rate.…”