Jiaxin Cui

Coke is an essential raw material in the blast furnace (BF) ironmaking process. Its moisture content significantly impacts BF ironmaking production. This study employs a coupled Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) approach to simulate the drying process of wet coke within a coke silo (CS) dryer. Initially, the model was validated by comparing numerical results with experimental data from the literature. Subsequently, it investigated the gas flow dynamics, heat and mass transfer characteristics, and differences in drying behaviour across distinct dryer zones. Finally, the effects of inlet gas velocity and inlet gas temperature on the drying process were systematically quantified. Simulation results reveal that the bottom of the CS dryer exhibits a low-velocity laminar state, while the middle and upper regions display intense gas flow motion. Consequently, the bottom region exhibits insufficient particle drying in comparison to other zones, with the average particle moisture content decreasing by less than 20%. Under the continuous heat exchange between the hot gas and the particles, the moisture content of the particles decreases rapidly. Based on the drying rate behaviour, the drying process exhibits the following three different stages: the pre-heating period, the constant-rate period, and the falling-rate period. Compared to zones 1 and 3, zone 2 exhibits higher temperatures due to its high heat transfer efficiency, which significantly promotes a reduction in particle moisture content. An increase in inlet gas velocity enhances the particle drying rate and heat flux, accelerates moisture reduction, and raises the temperature. The impact of inlet gas velocity is most pronounced after the constant-rate period, with particle drying uniformity decreasing as the inlet gas velocity increases, consequently leading to a decline in drying quality. Increasing inlet gas temperature significantly increases particle temperature and heat flux throughout the drying period and accelerates the high-rate drying stage. These findings provide fundamental insights for further understanding and studying the coke drying process.

Leaching is the core step in rare earth processing, enabling efficient separation of rare earth elements through selective dissolution. It determines resource utilization rates, environmental impact, and the economic viability of subsequent purification processes, underpinning the sustainable, high-efficiency growth of the rare earth industry. It should be widely recognized that the leaching process is inherently complex and subjects to multiple influencing factors. In this paper, the leaching of the rare earths in a stirred tank is selected as the research object, and the primary attention is given to the numerical investigation of the effect of the particle size on the leaching process. To this end, a computational fluid dynamics–discrete element method–volume-of-fluid model is developed to simulate gas–liquid–solid three-phase flows in a stirred tank, incorporating the unreacted shrinking core model to predict the leaching behaviors of the rare earth particles. Based on the simulation results, the effects of on particle flow behaviors, leaching behaviors, and power consumption are subsequently analyzed. The analysis results indicate that it is more recommended to use finer particles due to the more uniform distribution, higher leaching efficiency, lower power consumption, and less fluctuation of the power consumption during the leaching process. This paper should provide the relatively significant reference value for optimizing rare earth leaching process in industrial applications.

Ionic rare earth ore is a type of featured rare earth ore in China. Its mining process suffers from a long leaching cycle and considerable consumption of leaching agents. Improving mining efficiency requires a sound physical understanding of the leaching process. In this study, the CFD‐based numerical model is used to analyze the physical process of leaching through porous media formed by particles. The simulation results indicate that a lower packing porosity and smaller particles packed granular porous medium result in much larger energy dissipation during seepage, and the energy dissipation increases with seepage velocity. It is found that when the seepage velocity increases to a certain high value, the energy dissipation exceeds the value predicted by Darcy’s law, which is mainly caused by liquid turbulence. Additionally, the effect of particle shape is examined. The results show that the granular medium composed of prolate particles causes larger energy dissipation than oblate particles, and spherical particles play the least role. This phenomenon may result from the particle shape affecting the area of the frontal contact surface between particles and liquid. The results provide new insights into the fundamental understanding of percolation and seepage behaviors in the ion‐adsorption‐type rare earth ore leaching process.