Computational Investigation on Effect of Impeller Dimension on Fluid Flow and Interface Behavior for Kanbara Reactor Hot Metal Treatment

Abstract

Kanbara Reactor (KR) is widely used for hot metal desulfurization pretreatment in the steelmaking industry. The configuration of its impeller plays a crucial role in the reactor performance, but its function is not fully understood. Herein, a 3D volume of fluid (VOF) model coupled with the sliding mesh technique is developed, and the performance of five impellers with different dimensions is investigated. After the test of grid dependency, the calibration of turbulent models, and the validation via experiments, the numerical model is applied to study the typical developing phenomena and the effect of impeller dimension on the fluid flow characteristics, mixing time, interface profile, and vortex core depth. The results show that the centrifugal discharging flow extruded by the rotating impeller creates a double‐recirculation flow pattern in the axial direction. When the aspect ratio χ of the impeller increases, the upper recirculating region is successively strengthened and enlarged. Furthermore, the mixing time as a function of impeller configuration exists a minimum value. Impeller III is the optimal configuration in the current study. In addition, the relationship between vortex core depth and χ is obtained, and the velocity of the gas–liquid interface increases with the increase in χ.

Effects of Impeller Rotational Speed and Immersion Depth on Flow Pattern, Mixing and Interface Characteristics for Kanbara Reactors Using VOF-SMM Simulations

“…This study aims to provide a detailed analysis of the effect of impeller operating variables on fluid flow pattern, mixing characteristics, vortex core depth, and free surface velocity of KRs based on the developed Volume of Fluid model with the sliding mesh method (VOF-SMM). This study extends our previous work [20] in which the effect of the impeller dimension was discussed. Here, our focus is the rotational speed and immersion depth of impellers.…”

“…Our model has been reported in recent studies on the effect of impeller dimension for the KR process [20] and on a new dephosphorization technology for the converter steelmaking process [21]. In those studies, the grid sensitivity, calibration of the turbulence model, and model validation have been carefully examined, but considering some improvements and the completion of the present work, the outline is given as follows.…”

“…To track the free surface of gas-liquid two-phase flow in a KR, some assumptions were specified, and details were given in our previous work [20]. As a result, the hydrodynamics of this multiphase system is governed by a set of single Navier-Stokes equations and a continuity equation.…”

“…We have tested four kinds of classic turbulence models, i.e., the standard k-ε, standard k-ε with swirl flow correction term, RNG k-ε, and SST k-ω, and found that the RNG k-ε model can give an excellent solution compared with the experiments [20]. As a result, this study employs the RNG k-ε model to close the turbulence.…”

“…Model validations have been reported [20]. Because the availability of the industrial KR process data is limited by the measurement technology and the high costs of in-situ experimentation due to a high temperature under hazardous conditions, the water model experiments were resorted to in order to validate the model.…”