Energy efficiency characterization and optimization of mechanical stirring multiphase dispersion processes: Applied to Kanbara reactors for hot metal desulfurization

Abstract

In order to achieve the Best Efficiency Point (BEP) of an existing or new design of mechanically stirred multiphase reactors, such as the Kanbara Reactor (KR) desulfurization process, i.e., to realize maximum refining efficiency with minimum energy consumption, thus saving costs and offering high performance, it is essential to establish a quantitative correlation between the stirring power and the utilization rate of the lighter reagent that covering on the heavier phase. Herein, a validated droplet-resolved model based on a Large-scale Dispersed Phase-Resolved Volume of Fluid (LDPR-VoF) approach coupled with a subgrid-scale Large Eddy Simulation (LES) was applied to explore the characteristics of entrainment and dispersion of the lighter liquid reagent, the relevant energy utilization, such as the kinetic energy, turbulent kinetic energy, and its dissipation rate characteristics, with respect to different design and operating conditions during the mechanical stirring process. Furthermore, a crucial measure ηd for the quantitative evaluation of the energy efficiency and the determination of BEP, which represents the ability of an impeller to convert its power input into the dispersion of the upper lighter phase in a layered multiphase vessel, was proposed and used to evaluate the effect of the impeller and reactor inner profiles on the energy efficiency. Eventually, a correlation formula is obtained to assess the utilization rate of the stirring power on the refining performance, which can be used to optimize the design/operation parameters towards the BEP for a mechanically stirred multiphase dispersion reactor.