Multiphase Computational Fluid Dynamics (CFD) Modeling Study of Slopping Behavior During Basic Oxygen Steel Making (BOS) Process

Abstract

A multiphase CFD model has been developed to investigate the effect of impinging supersonic oxygen jet on hot-metal bath deformation during basic oxygen steel making process. This model also helps to study and predict the sloping behavior taken place during blowing period inside Linz-Donawitz (LD) converter. Detail knowledge of fluid flow behavior inside the LD converter is essential as steel making through LD converter is most dominant among all the primary steel making processes and the efficiency of BOS relies on mass, momentum, energy transfer and rigorous interaction among metal, slag and gaseous phases. Cavity formation in hot-metal bath due to supersonic oxygen blow has been studied using multiphase CFD simulation method. Depth profile of cavity with respect to blowing time and different oxygen flow rate has been simulated in this work. The simulation of fluid flow inside LD converter has been carried out using various turbulence modelsalong with volume of fluid method (VOF). Numerical simulationof fluid flow behavior inside LD converter has been performed using ANSYS 15.0 software. Assumptions for this modeling are: incompressible and Newtonian fluid having constant molar viscosity, no source term, isothermal fluid flow and no miscibility between oxygen and hot metal. This simulation work will help to evaluate average penetration depth with respect to different impinging supersonic oxygen flow rates. This work demonstrates change in bath deformation profileduring blowing period and also identifies the locations of different vortexes formed owing to supersonic oxygen jet penetration. Centre line velocity of impinging supersonic oxygen jet has been calculated to investigate the probability of emulsification. Two phases such as gaseous oxygen and liquid metal slag phase have been considered for this simulation work. The liquid phase is a mixture of 80% hot metal and 20% slag having 5607.24kg/m3 density. This multiphase simulation study exhibits the variation of fluid flow profiles (e.g., velocity magnitude, stream function, turbulence intensity) with respect to time during blowing period. Identification of better mixing zone as well as poorer mixing zone inside LD converter is also salient feature of this study. Moreover, it predicts the time duration for starting of sloping phenomenon for different oxygen flow rates and also finds that near nose (just below converter mouth) region is most vulnerable for erosion during slag slopping.