Numerical Simulation For Free Surface And Mixing Characteristics Of Multiphase Flow In KR Stirred Vessel

With the rapid development of national economic construction, the demand for high quality steel is increasing day by day,and the high sulfur content in steel will reduce the mechanical properties of steel, such as toughness, plasticity and fatigue life.Due to the high desulfurization effect and low cost, KR (Kanbara Reactor)mechanical stirring desulfurization has been widely used in the preprocessing process of hot metal desulfurization. In the actual production, KR desulfurization involves many complex processes, such as the free liquid surface entrains the desulfurizer granules and the desulfurizer granules mix with the hot metal, and the study of the flow field in the vessel is the basis for analyzing these processes. With the rapid progress of CFD technology, numerical simulation method can not only overcome the problems such as high experimental cost and harsh conditions, but also has intuitive images and direct measurement of flow field parameters, so it is widely used in the study of multiphase flow mixing efficiency in the stirred vessel.At present, some numerical study of KR desulfurization do not take into account the effect of free liquid surface on the entrainment of the desulfurizer particles, and the desulfurizer particles are regarded as quasi-fluid,which is different from the desulfurization process under the actual working conditions. The numerical research on the influence of the process parameters on the free surface change, the flow field characteristics and the diffusion behavior of the desulfurization in the stirred vessel has important practical value to enhance the solid-liquid mixing performance and improve the desulfurization efficiency. In this paper, the commercial CFD software FLUENT is used for numerical simulation. On the one hand, based on the water model experiment, the numerical simulation is used to study the effect of main structural and process parameters on the change process of the free surface and the flow field in the stirred vessel. On the other hand, the Euler-Euler model and the coupled Euler-Lagrangian model are used to analyze the movement process of the desulfurizer particles drawn into the tank by the free liquid surface and the dispersion effect. The main research contents are as follows:(1) The water model experiment based on similarity criterion is established to obtain the measurement results of the free surface vortex depth and vortex height under different agitator speeds and immersion depths. Then based on the standard turbulence model to describe the turbulence characteristics of the flow field,the multiple reference frame (MRF) and VOF (Volume of Fluid) method are used to establish the gas-liquid flow model. The flow field and free liquid surface in the stirred vessel are analyzed by numerical simulation. In order to verify the accuracy of the numerical simulation method, the simulation results of vortex depth and vortex height are compared with the results of the water model experiment. In addition, the effect of the stirring speed, the immersed depth, the impeller diameter, the blade number and other parameters on the free surface and flow field in the stirred vessel are researched by this numerical simulation method.(2) The numerical research of multiphase flow mixing characteristics in the stirred tank is carried out under uniformity and tiling two kinds of initial desulfurization setting methods, while the desulfurizer particles are regarded as quasi-fluid by Euler-Euler method, and the desulfurization agent, water and air concentration distribution are considered. And the impact of the speed and immersed depth of the stirrer on the distribution of desulfurizer are further explored.(3) Using the joint method of EDEM and FLUENT, the solid-liquid-gas three phases flow numerical model of KR desulfurization is established by coupled discrete element method and finite volume method. The solid particles are modeled by discrete element method, while the water and air are modeled by continuous fluid phase. And the dynamic simulation analysis is carried out for the trajectory tracking of desulfurization and flow field characteristics when the free surface is considered,so as to get the direct visual display of the process effect and make the appropriate evaluation.